The Optometric Examination of the Older Adult PDF

The Optometric Examination of the Older Adult  IAN L. BAILEY The patient’s demands should be given some overt attention, but the optometrist should remain conscious...

The Optometric Examination of the Older Adult  IAN L. BAILEY The patient’s demands should be given some overt attention, but the optometrist should remain conscious of the possibility of an unspoken hidden agenda that might be harbored by either the patient or the eye care practitioner. The practitioner should mentally take stock and ask three questions: (1) What does this lder adults are a special group within patient want? optometry’s patient population. Many of their (2) What, in my opinion, does this patient need? (3) visual characteristics and their varied needs What is the real reason for the patient’s being here O make them different from the younger segments of the clinical population. This chapter focuses today? These three questions will some- on the special considerations commonly required in 133 the provision of vision care for the older patient. times give rise to the same answer; in older adults Inevitably, a chapter such as this is laden with especially, however, any differences in these answers generalizations because it emphasizes features that can be important in making and presenting decisions may be relatively common in older adults even though and recommendations. they are by no means universal within, or unique to, The case history should begin with the patient this group. being asked to identify the main visual problem or Visual needs are often changed by retirement or by problems. The optometrist should encourage a full changes in lifestyle imposed by physical or sensory elaboration of the presenting complaint by asking limitations acquired through aging. Aging brings questions motivated by a genuine curiosity and a inevitable changes to the visual system, such as loss of desire to understand fully the patient’s problem. After accommodation, reduced transmittance of ocular the major presenting complaint has been adequately media, and pupillary miosis. The visual system is also explored, the patient should be asked if other problems affected by agerelated ocular pathological conditions, are present, and each of these should be pursued in the most notable of which are maculopathy, cataracts, turn. Some older patients, especially those who are glaucoma, and retinopathy. Changes in the visual lonely or have some doubts about their self-worth, needs and normal and pathological changes in the may relish being the focus of attention, and the visual system create a wide diversity of special clinical interview might become quite diverted. The clinician problems. The eye care practitioner becomes obliged should be sensitive and tolerant toward such to apply special emphasis and techniques, and special digressions. optical treatment or other rehabilitative attention often When the patient exhausts the self-generated list of is essential. problems, some important topics should be raised if The diversity of vision needs and characteristics they have not been covered already. These areas can distinguishes older adults from the rest of the patient be divided into the following four categories: population. Therefore, when dealing with older 1. Distance vision. Patients should be asked about the patients, practitioners must use more imagination and adequacy of their distance vision for particular flexibility in structuring the examination and tasks, among which are recognizing faces, treatment to suit these diverse individual needs. watching television or movies, and reading signs. CASE HISTORY Mobility tasks such as driving, using public transportation, and walking in familiar and The goal of all case history taking is to obtain an unfamiliar environments can be important. understanding of the patient’s problems and needs. Reactions to different illumination conditions may The case history shapes the sequence and emphasis of be included here. examination and assessment procedures, the design of 2. Near vision. Reading is typically identified as the treatment programs, and the presentation of most important near vision task. The optometrist recommendations and advice. The rapport developed should establish whether the patient can in the case history interview can be a crucial factor in satisfactorily read books and magazines, private determining the success of any treatment. The and business correspondence, and labels and price optometrist must develop and display a genuine strong tags. Patients should be asked about the use of concern for the patient’s needs that are motivating the computers and any optical or electronic magnifiers investigative procedures and treatment considerations. or special lighting conditions that are important to  reading tasks. Other near vision tasks such as disbelief, grief, denial, and anger. In time, however, handicrafts, maintenance chores, self-grooming the individual’s emotional state stabilizes. tasks, and food preparation also warrant attention. Practitioners dealing with patients who have a recently 3. Ocular and general health history. Current and acquired loss of vision should be aware of the previous ocular health and general health probability of changing emotional attitudes. conditions or treatment should be investigated. The Sometimes delaying the finalization of prescription practitioner should determine whether the patient decisions until the patient comes to reasonable terms is currently taking any medications and, if so, with having visual limitations is warranted. consider any possible side effects. The patient’s Patients who already have some loss of vision experience with glasses or other optical aids should commonly fear that total blindness or substantially be investigated, and any problems or shortcomings worse vision is inevitable. Patients should be of previous optical treatment should be identified. encouraged to discuss these fears. Often associated When some loss of vision has occurred, the pattern with the fear of blindness is a concern that some past of development of the loss should be established. abuse of the eyes is the cause of their vision loss and The practitioner should ask patients about their will soon produce dreaded injurious consequences. perception of the cause, prognosis of the ocular Excessive reading, excessive fine work, poor condition, and the treatment that has been given. illumination, wearing glasses, failure to wear glasses, 4. Lifestyle. Some major changes in the activities of wearing the wrong glasses, sitting too close to the daily life occur with aging. Some changes will be television, using fluorescent lamps, or watching color forced by age-related changes in health and deficits television are all believed to ruin vision, and such in motor, sensory, or cognitive functions. The mistaken beliefs are more prevalent in older adults. living environment may change; interests, Patients with these concerns should be given aspirations, and habits may be altered; the capacity appropriate advice and reassurance. Patients who have of independent travel and independent home already suffered some vision loss are particularly management may be curtailed; and dependence on likely to be influenced by erroneous but commonly relatives, friends, or rehabilitation personnel may held beliefs that may lead them to expect a dismal develop. The practitioner should be alert to such visual future. Furthermore, low vision patients may changes because they can significantly influence sometimes proudly claim great virtue and restraint the needs of the patient. because they do not sit too close to the television, do Aging patients often have special fears and not read any more than is essential, and do not use prejudices that require consideration. Most people strong light, when, in fact, the avoided behaviors pose have some fear of vision loss occurring in their no threat to remaining vision and could provide the advancing years. This fear becomes heightened when means for a broader and more enjoyable range of peers experience vision loss or begin to require activities. Thus practitioners should take special care attention or treatment for cataracts, maculopathy, or to counsel their older patients about their future eye glaucoma. Older patients commonly and strongly fear care needs and the prognosis for changes in their impending blindness or serious vision loss, but they vision and ensure that the patients really understand rarely admit this fear. The practitioner should the status of their own vision. therefore be careful to read between the lines during When an individual retires, interests and priorities the history and identify such fears. In recent years the often change. Especially if some agerelated disability public’s awareness of health care issues has rapidly has occurred, older people often curtail their social, increased. The practitioner should stay abreast of the vocational, and recreational activities. Withdrawal latest developments in current and emerging from social and other pleasurable activities can be treatments, including nutritional supplements, passive and unconscious. The eye care professional particularly as they relate to disorders affecting vision. should understand the patient’s range of current daily Through the Internet, patients and their families now visual activities. When some vision loss has occurred, have easy access to medical information and opinions, the extent to which the vision loss is restricting and consequently clinicians now have to be prepared activities or aspirations should be determined. A to answer more sophisticated questions. useful approach is to ask patients to describe their A partial or total vision loss is inevitably an typical daily activities. Ask what they do from the time emotionally traumatic experience for the individual they get out of bed in the morning until they go to bed concerned. After the initial shock, a sequence of at night. Such questioning often reveals the range of emotional reactions can involve depression, anxiety, visual demands and, when restricted vision is present, often indicates the extent to which people are part of the clinician’s basic responsibility and also modifying their lives because of vision difficulties. reinforces the message that regular eye examinations The frustration and regret associated with a vision loss are important to older individuals. The details of is often revealed by the question, “What things could discussion about ocular disease will vary according to you do when you had good vision that you cannot do the patient, the examiner, and their previous now?” interactions. Even though the examiner can grow tired In bringing the introductory interview to a close, of giving essentially the same routine explanations to the careful optometrist will summarize the priorities patient after patient, this responsibility should not be for the examination process that is to follow: “So, if I neglected or conveniently curtailed. understand things correctly, the most important thing for us to concentrate on is your reading, especially for REFRACTION bank statements. And we should thoroughly check the The older population experiences significant changes health of your eyes. Is this right?” in refractive error.17 Commonly a shift toward more Reminding the patient that mutually agreed upon against-the-rule astigmatism occurs, and the spherical goals have been established and that these goals component of refraction shifts in the direct of motivate all the examination procedures can be hyperopia. The prevalence of oblique astigmatism and reassuring. Advising the patient of the purpose of anisometropia increases. Cataractous changes in the various tests and relating them to the patient’s lens may precipitate rapid changes in refraction. Often symptoms emphasizes the clinician’s concern and an individual’s refractive status is changed develops a stronger spirit of participation in the substantially as a result of cataract surgery. patient. Objective Refraction OCULAR HEALTH EXAMINATION Retinoscopy can be more difficult in older patients A thorough inspection of the external and internal because of small pupils and media irregularities and aspects of the eyes with appropriate instrumentation is opacities. However, it remains an important technique especially important in older patients. Statistically and the examiner should make every effort to obtain a they are much more likely to have significant ocular retinoscopic estimate of refractive error. When and general health diseases and disorders. retinoscopy becomes unusually difficult, however, the The inspection of the interior of the eye can be clinician should be prepared to vary techniques. more difficult than in younger patients because of Moving to closer than usual observation distances or small pupils and lack of media clarity. Unless moving off axis may provide an “easier” retinoscopic contraindicated, the pupils should be dilated to enable reflex; Mehr and Freid25 described this as radical the examination. However, postponing the instillation retinoscopy. If a useful retinoscopic reflection cannot of the mydriatic and the full ocular inspection until be obtained with the standard procedures, the clinician after the visual abilities have been tested is beneficial. should first move closer and thus reduce the working When ophthalmoscopy remains difficult, easier distance, perhaps to as close as 5 cm in search of a observation is possible by using small-diameter satisfactory reflex. This technique is useful with ophthalmoscope systems and perhaps reducing the unsuspected high myopia. If moving closer still illumination level. Slit lamp examination of the provides no useful retinoscopic reflection, high eyelids, conjunctiva, cornea, anterior chamber, iris, hyperopia could be responsible. Placing a high and lens requires more attention in older patients positively powered lens (e.g., +14.00 D) at the because of the relatively high prevalence of aging patient’s eye, beginning with a standard working changes affecting these tissues. distance and gradually reducing the distance, might Tonometry should be performed routinely on older enable the clinician to find a difficult retinal reflection patients because of the higher incidence of raised in patients with high hyperopia. Of course, when the intraocular pressure and glaucoma. retinoscopic working distance is changed, an During the examination of the eyes, the practitioner appropriate allowance must be made in estimating the should explain what is being done. Older patients are power of the refractive correction. Furthermore, almost invariably aware of cataract, glaucoma, and moving off axis may produce some inaccuracy in both macular degeneration, and they should be reminded the spherical and astigmatic components; thus this that these and other ocular diseases are being given procedure is used only when axial viewing does not close attention. They should be fully and clearly provide an adequate reflex. advised of the state of their own ocular health. This is  When substantial lenticular irregularities are the spherical refraction becomes easier because of the present because of cortical or posterior subcapsular stability of the accommodative state. Standard cataract, obtaining consistent or accurate results may binocular balancing techniques may be used. be impossible because the apparent movement of the Astigmatism may be determined by using crossed- reflected light seems to be fragmented (moving in cylinder techniques; the clock dial or related different directions or at different speeds). In these techniques also may be used. In the presence of media circumstances, a spot retinoscope is sometimes more irregularities, however, the crossed-cylinder method is useful than a streak retinoscope. preferred. Clock dial, sunburst, paraboline, and similar Objective optometers or automated refractors techniques involving judgment of the relative clarity depend on light being reflected from the retina. Again, of lines in particular orientations all can produce the small pupils and media opacities commonly found anomalous results when refractive irregularities in the in older patients often lead to less-reliable results. media are present. Similarly, the stenopeic slit method Sometimes no result at all can be obtained. for determining astigmatism may be less appropriate Keratometry or keratography to estimate total for patients with significant lens or corneal astigmatism becomes more important when irregularities. retinoscopy or objective optometer measurement fails. A record of corneal curvature can be useful in Refraction of Patients with Low Vision quantifying any future changes. Patients with low vision often require different Patients with low vision are often unable to make refraction techniques. The phoropter should not be accurate judgments in subjective refraction used. Patients should be free to move the head and procedures. Thus more than usual reliance on eyes to any preferred positions; they should not be objective refraction results may be necessary. artificially shielded from the ambient illumination; their eye movements and eye position should be Subjective Refraction observable by the clinician; and they should be aware Subjective refraction often requires more time with that improvements achieved are attributable to simple older patients. Their sensitivity to blur may be reduced lenses rather than the “magic box” that the phoropter because of small pupils or because of media or retinal might represent. changes that affect visual discrimination. Judging Trial lenses supported in trial frames, or in lens changes of image clarity in response to small clips attached to the patient’s current glasses, should refractive changes becomes difficult. Slower be used. However, trial frames tend to be clumsy and presentation of alternatives and sometimes repeated often require repeated readjustment and repositioning. presentations can become necessary. However, older Furthermore, the vertex distance they provide is often patients, lacking accommodation, do have a stable larger than the eventual spectacle-lens vertex distance. refractive state, which can improve the reliability of These factors all become more bothersome when the refractive error measurement. refractive error is large. In general, therefore, trial lens When visual acuity is expected to be normal or near clips (Halberg, Bernell, Jannelli, or other clips) that normal, a phoropter and the usual range of refractive attach to existing glasses are easier to use. With trial techniques may be used. The biochrome (or lens clips used over the patient’s current glasses, the duochrome) test, which is sometimes unreliable in frame usually sits securely and the lenses have a more younger patients, can be a more reliable test in older appropriate vertex distance and pantoscopic tilt. These individuals. Again, small pupils may make together enable a more accurate determination of the discriminating the relative clarity of the red and green required refractive correction. targets more difficult. The yellowing of the crystalline Working over the current glasses, the practitioner lens with age may cause the brightness of the green typically has to use only relatively low-powered background to be reduced more than the red. lenses. This is useful because lowpowered lenses are Importantly, clarity of the letters rather than the easier to insert and remove from trial lens mountings brightness of the red or green background is the and are usually available in finer steps of power. criterion. Astigmatism can usually be measured more When the observation distance is 4 m or closer, an accurately when trial lens clips are used. For either appropriate dioptric allowance (obtained by changing retinoscopic or subjective determination of the refraction result by 0.25 D for a 4-m distance) astigmatism, the practitioner should first completely should be made if clearest distance vision is being ignore an astigmatic correction that may be in the old sought. With older patients, the binocular balancing of glasses. The astigmatic component of the overrefraction is determined as though it were finding or the patient’s previous correction. Initially completely independent. The axis and power of the the steps of dioptric power should be large enough to overcorrecting cylinder does not have to bear any be certain that recognizing changes in clarity will be relation to the cylinder present in the glasses over easy for the patient. which the refraction is being performed. Begin with a strong plus lens in one hand and a When the overrefraction has been completed, the minus lens of equal power in the other (e.g., +6.00 D glasses—with lens clips and trial lenses still and −6.00 D). Once the patient can make confident attached—are taken to a lensometer, and the back responses to dioptric changes, the size of the changes vertex power of the combination is measured. This should be systematically reduced in the process of gives the total power required to optimally correct the pursuing the refractive error. When using handheld refractive error. For example, a patient may be lenses, fabricating the plano presentation is often wearing a correction of 0.00 DS −4.50 DC × 35, and advisable by holding lenses of equal and opposite the overrefraction in the trial lens clips may be +0.75 power together rather than using no lens at all. Some DS −1.25 DC × 160. The examiner could do laborious patients have already decided whether they want a calculations to determine the resultant power, but change of correction, and this can influence their measuring the back vertex power of the combination responses to “with” to “without” comparisons. with a lensometer is easier. The resultant power will When large steps of dioptric power are being used, be found to be 0.00 DS −4.25 DC × 27. Note that the the clinician can be guided by the strength of the axis of the overrefraction cylinder (160 degrees) is patient’s response. This may be revealed by the different from the axis of the original (35 degrees) or patient’s choice of words, tone of voice, or quickness the final (27 degrees) cylinder and that a moderate of response. Encouraging patients to describe what overrefraction cylinder power (1.25) gives rise to a they see is better than simply indicating whether they very small 0.25 change in the final astigmatic prefer the “first” or “second” view. For example, upon correction. This method becomes particularly valuable the introduction of a +6.00 D lens, the patient is asked, when the lens powers are high. “What happens with this lens? Does it make it worse, In any new glasses the pantoscopic tilt of the lenses better, or no difference?” The patient might respond, and the vertical positioning of the optical centers will “That’s blurry.” Upon switching to the −6.00 D lens, probably be similar to those in the previous glasses. the patient says firmly, “That’s much worse.” To a Any power errors that may have resulted from the plano presentation (+6.00 D combined with −6.00 D) aberrational effects created by tilt and position of the the same patient responds, “Ah! That’s better.” From lens will be compensated for by the overrefraction, this sequence, the examiner has learned that plus is and a more appropriate refractive correction preferred to minus and the patient has a solid determination will be obtained. preference for 0.00 D over +6.00 D. The refractive Patients with low vision are often less sensitive to error appears to be positive: closer to 0.00 D than refractive changes. In general, the poorer the acuity, +6.00 D, but it is not very close to 0.00 D because of the poorer the sensitivity to change. However, this is the strong difference between +6.00 D and −6.00 D. far from being a universal rule. Sometimes patients At this stage a reasonable guess at the spherical with visual acuities of 20/500 will be able to respond refraction error would be in the range of +1.25 D to reliably to 0.50 D of change, and some patients with +2.25 D. This process is called “bracketing,” which 20/60 acuity may not be able to respond to 1.50 or 2.00 means obtaining “rejections” from both an excess of D of change. The clinician should not have a fixed plus and an excess of minus. expectation of the patient’s sensitivity to refractive At this stage the patient’s spherical refractive error changes based of the visual acuity. Beginning the is contained within a ±6.00 D bracket, and it appears refraction with an open mind and waiting for the to be on the hyperopic side of plano. Next, a patient’s responses to reveal the individual sensitivity reasonable estimate of the spherical refraction (e.g., to blur is best. +2.00 D) is added to the trial frame and a new pair of Refraction Procedures handheld bracketing lenses are used. A +1.50 D and a −1.50 D might be chosen. The clinician should expect Subjective refraction with a low vision patient begins the patient to “reject” both limits of the new with directing the patient’s attention to visual acuity bracketing range (+0.50 D and +3.50 D) and indicate chart letters at, or close to, the patient’s limit of a preference for the central region of this range. With resolution. The best estimate of refractive error should the +1.50 D over the +2.00 D, the patient might say already be in place; this might be the retinoscopic “That makes it blurred.” Switching the +1.50 D to the VISUAL ACUITY MEASUREMENT −1.50 D the patient may say, “That’s a bit better,” and Visual acuity measurement requires a little more care when the +1.50 D and −1.50 D are combined, the in older patients than in younger ones. Older patients patient may say, “That’s better still.” This sequence of are more affected by the luminance of the test chart responses first indicates that the refractive error is and the distribution of light within the luminous closer to +0.50 D than to +3.50 D, which means it is environment. Thus more care than usual should be less than +2.00 D. Second, it is closer to +2.00 D than taken to ensure that the chart illumination is at a +0.50 D, which means it is more than +1.25 D. If the standard level (80 to 320 cd/m2) and that potentially responses have been reliable, the only logical troublesome glare sources are eliminated from the possibilities remaining are that the refractive error is field of view.12 Illumination conditions may need to be +1.50 D or +1.75 D. Changing the lens power in the changed while visual acuity is being measured. trial frame to one of these two alternatives, and using Because older patients are more likely to have ocular a +0.75 D and −0.75 D, for example, to create a tighter changes that affect their vision, for reference purposes bracket might lead to a final decision. If the +1.50 D the best practical measure of visual acuity should be lens is in the trial frame and the +0.75 D handheld lens made and the viewing conditions kept the same. is preferred to the −0.75 D, then the answer is +1.75 When visual acuity is reduced, nonstandard D. The answer is +1.50 D if no preference between the techniques become necessary. Projector charts, which are suitable for the measurement of normal or near- ±0.75 D is stated. The spherical refraction is finalized normal visual acuity, should not be used for low vision when changing from plus to minus in the finest patients. Most projectors do not provide the high discriminable step elicits a response indicating that contrast or the simple and broad range of luminance both presentations appear slightly, but equally, adjustability that is available with printed panel or blurred. transilluminated charts. Also, projector charts lack On completing the initial spherical power flexibility to extend the range to larger angular sizes determination, the optometrist can begin the to measure poorer acuities. With printed panel charts, astigmatic determination with some knowledge of the altering the observation distance over a wide range is patient’s responsiveness to refractive blur. This easy. knowledge can guide the practitioner in choosing the For all visual acuity measurement, recording acuity power of the Jackson cross cylinder to be used. In a by giving partial credit for rows that were only general optometric office, ±0.25 D and a ±0.75 D partially read correctly (20/20 −2, or 20/25 +1, etc.) is handheld cross cylinder should be available. The important. Practitioners who do not always use the lower power cross cylinder is useful for normally same chart should always make note of the chart that sighted patients, and the ±0.75 D cross cylinder will was used. be strong enough for most low vision patients with poorer discrimination. The test target observed during Visual Acuity Measurement in the Jackson cross-cylinder refraction is usually a Low Vision Patients selected letter or letters on the Snellen chart at, or close Chart design can influence the visual acuity score, to, the limit of the patient’s acuity. Remember that the which can become most important when macular flip cross-cylinder test works best when the spherical function is disturbed. The number of letters per row equivalence of the test lens combination is kept and the relative spacing between letters and between constant. Again, bracketing approaches are rows can cause substantial variations in visual acuity recommended. Begin using large steps of power to scores. Many low vision patients require a reduced obtain strong rejections of powers that are too strong observation distance, and the practitioner should be and too weak. When determining axis, elicit strong aware that, with some charts, changing observation rejections by presenting alternative axis orientations distances can influence the acuity scores obtained. that are substantially to one side or the other of the First, scaling may change. Many charts have a size predicted true axis of astigmatism. sequence of 200, 100, 80, 60, 50, 40, 30, 25, 20, and After the astigmatism has been measured, recheck 15. At 20 feet, an acuity of 20/200 might be recorded, the spherical component. If any significant spherical indicating that the patient read the 200-foot symbols change is necessary, the power of the cylindrical but failed to read the 100-foot symbols. On changing correction should be rechecked. to a 10-foot observation distance, the practitioner might first anticipate that the acuity score will be 10/100 because that is consistent with the 20/200 result. Consistency with the 20-foot measurement with the English alphabet. Landolt rings and the only requires that the acuity be at least 10/100, but not tumbling E are alternative optotypes that do not as good as 10/50. Thus the acuity score could be require any level of literacy from the patient. measured as 10/100, 10/80, or 10/60 and still be fully Low vision patients may have their visual acuity consistent with the 20/200 finding. Only when the significantly altered by relatively minor changes in chart follows a logarithmic (or constant proportion) illumination. Thus the recommended procedure is to size progression can this scaling problem be avoided. make the first measurement of acuity at the standard Second, changing to a closer observation distance or customary illumination level. Then, referring the often alters the nature of the task at threshold. The patient to the smallest letters that can be read, ask if number of letters per row may increase, and the any change is perceived when illumination is relative spacing between optotypes may change. With increased or decreased. When externally illuminated macular dysfunction, contour interaction and panel charts are being used, the illumination may be crowding become much more important than usual, controlled by increasing or decreasing the room light, and increasing the number of letters per row or moving a light closer to or further from the chart, or reducing spacing can significantly reduce the acuity using masks to shield the chart from light. score that can be obtained.14 A patient who reads a When central or paracentral scotomas are present, single 20/200 letter with ease might not be able to read the manner in which the patient reads the chart may be any of three closely spaced letters on a 100-foot row informative. Many patients perform much better when when the viewing distance has been changed to 10 reading letters at the start or the end of rows and feet. perform poorly when attempting to read more central Visual acuity scores will be more valid and more letters. At other times a pronounced hesitancy and impervious to change with changing observation difficulty reading the letters in sequence are present. distance if the task is made essentially the same at each These behaviors usually indicate problems from size level. This requires that almost equally legible central scotomas and may lead the clinician to expect symbols be used, that the same number of symbols be some limitation of the patient’s potential to read in each row, that the spacing between symbols and efficiently.11 When evidence or suspicion of macular between rows be proportional to symbol size, and that disturbance is present, encouraging eccentric viewing size follow a geometric (or logarithmic or common is useful by directing the patient to fixate above, multiplier) progression. BaileyLovie logMAR charts below, to the right of, or to the left of a row of letters and their derivatives follow these principles.6,13,32 that has been found to be difficult. Any reported The Bailey-Lovie design principles were changes in visibility can indicate whether eccentric developed to avoid problems often encountered in low viewing strategies may facilitate reading the chart. For vision work. Their original size range extended from some patients the scotoma size and its effect on the 200- to 10-foot letters (60 m to 3 m). With the chart as ability to read the chart will vary substantially with close as two feet, acuities of 2/200 (equivalent to relatively modest changes in chart luminance. 20/2000) can be measured. The Feinbloom visual ASSESSMENT OF NEAR VISION acuity chart is a popular chart designed for low vision work. The size progression is irregular, and wide Some aspects of the near vision assessment become variation exists in spacing and the number and much easier with older patients. Because older legibility of symbols at the different size levels. patients lack accommodation, their working distance These features together reduce the reliability of visual becomes highly predictable from the power of the acuity measurement and the consistency of scores addition being used. The range of clear near vision when viewing distance or magnification is changed. depends on pupil diameter and the size of the test Nevertheless, the Feinbloom chart does have target detail. If the target is newsprint, or something of attractive features: the size range extends to a 700-foot similar legibility, the range of clear vision is symbol, and the symbol size sequence progresses in commonly measured to be approximately 1.00 D in relatively small but irregular steps. The page-turning older patients. Using charts with print sizes that go mode of presentation can be psychologically smaller than the patient’s resolution limit, and encouraging to patients who have become accustomed providing that the patient always looks at the smallest to reading few letters correctly when tested on more print that can just be read, the range of clearest vision common charts. The Feinbloom chart also uses is often found to be reduced to approximately 0.25 D numbers rather than letters. Numbers can be useful in patients with good visual acuity. optotypes for patients who are not familiar or facile  For patients with normal distance visual acuity, an marginal improvement will occur (one third of a line). equivalent near-vision letter chart visual acuity A +3.25 D addition would be required to provide a usually will be achieved. Occasionally, near visual resolution improvement that could be described as acuity may be significantly worse if central lenticular “one full line.” opacities are present that have a more harmful effect Optometrists usually measure and record the near on vision when the pupil constricts in response to visual acuity. Near visual acuity may be measured viewing near objects. More rarely, acuity can improve with a letter chart, similar to the kind used for distance at near distances because peripheral lens opacities are visual acuity, or a reading chart that uses typeset print. rendered less important by pupillary constriction. The near visual acuity record should specify both the The quantity and quality of illumination should be observation distance and the size of the smallest print optimized, and older patients generally should be that may be read. Specifying print size in M units or given advice on how to arrange their lighting for points is preferable. M units express the distance in prolonged near visual tasks. An adjustable lamp with meters at which the height of the lowercase letters a compact lamp or bulb (60 or 100 W) provides an subtends 5 minutes of arc. Points indicate print size almost universally useful means of controlling the task according to the units used by printers and typesetters. illumination. The illumination on the task can be Charts from the United Kingdom usually specify print increased by moving the lamp closer to the page. The size with the letter N followed by a number (e.g., N.8). lamp or bright spots from the reflector of the lamp The N indicates the font is Times New Roman, and the should not be directly visible to the patient. number indicates the size of the print in points. The most appropriate near-vision addition can be Expressing print size as a reduced Snellen equivalent, determined in various ways, but the desired viewing a fraction that expresses the equivalent distance visual distance dominates the decision for the typical older acuity required to read that particular print when it is patient. A variety of methods can be used to determine viewed from 40 cm, is common but not appropriate. the power of the addition; the range of clear vision, This method is clearly inappropriate when the viewing biochrome, or cross cylinder at near techniques all can distance is other than 40 cm. Recording 20/20 at 30 work satisfactorily on older patients. After the cm is confusing and inaccurate because this clinician has determined the power of the required expression, as it is most commonly used, is intended addition while using test charts at the desired working to indicate that the visual acuity is in fact less than or distance, performance should be tested by using equivalent to 20/20. magazines, newspapers, bank statements, or whatever Print that is truly equivalent to 20/20 at 40 cm can represents the patient’s most common or most be said to be 0.40 M units in size. By using the M unit important near vision tasks. notation, near visual acuity can be expressed as a true If a change in the power of the addition is to be Snellen fraction. Print that is 0.40 M (20/20 at 40 cm) considered, the clinician should be conscious of the viewed at 40 cm would demand an acuity of 0.40/0.40 magnitude of resolution improvement that can be M; if the same print were just legible at 30 cm, the expected. Almost all distance visual acuity charts use acuity would be 0.30/0.40 M. The M unit system is far a size progression ratio of approximately 5:4 in the more appropriate and more consistent with the region of 20/20 (50, 40, 30, 25, 20, and 15). Changing methods traditionally used to measure distance visual viewing distance by a 5:4 ratio (50 cm to 40 cm, 40 acuity. Another alternative system for indicating print cm to 32 cm, etc.) should proportionally increase size is the Jaeger notation, which is favored by many resolution capacity equivalent to one line of ophthalmologists. Print sizes are labeled with a letter improvement on the test chart. Because dioptric power J followed by a number, with smaller numbers is inversely proportional to viewing distance, the associated with smaller print sizes. The Jaeger system addition must be increased by a ratio of 5:4 to achieve is not standardized and, between different charts, improvements that may be thought of as one line of substantial differences in the size of print that have the acuity. Thus 1.50, 2.00, 2.50, 3.25, 4.00, and 5.00 D is same J label can occur—J.3 print on one chart may be a series of lens powers in which each step represents as much as twice the size of J.3 on another. approximately one line of acuity improvement. Note Fortunately, the Jaeger system is becoming less the close similarity between the numbers in this commonly used, and its lack of standardization is sequence and the size progression in the 20/20 region becoming well known. of the distance visual acuity chart. With this sequence In patients with normal or near-normal vision, close as a reference, the clinician can deduce that if an concordance between the near and distance visual addition is increased from +2.50 D to +2.75 D, only a acuities usually exists. The visual task for the near visual acuity measurement usually involves reading before on eye. Poor fusional responses tend to indicate typeset print, which is more complex than reading the a need to consider prescribing prisms. fairly widely spaced letters found on the distance Although measuring the near phoria with the test visual acuity charts. Such differences in complexity do target close to eye level is common practice, having not have much influence on acuity scores in the the target lower so that downgaze is required is more normally sighted eye. In patients with disturbed appropriate. This is more representative of the habitual macular function, however, task complexity can cause reading eye posture, particularly if the patient holds or major inconsistencies in acuity scores. Patients with touches the near fixation target. macular degeneration commonly have a near or A variety of subjective tests are available for reading acuity score that is twofold worse than the measuring heterophoria in younger patients, and these distance letter chart acuity. often provide different measures of the heterophoria. Near visual acuity measurements with reading However, more consistency is found in older patients charts often serve as a basis for determining the because of the absence of accommodation, so the magnification that a low vision patient might require choice of method for measuring heterophoria becomes to perform a complex task at near satisfactorily. less important. Distance visual acuity measurements taken with letter When a heterophoria is potentially significant, the charts are much less reliable for this purpose. practitioner must decide if a prism is to be prescribed Reading efficiency or speed is often assessed, and, if so, how much. Many reasonable approaches to usually qualitatively during the assessment of near these decisions are available (see Chapter 13). vision needs. Clinicians should be aware that, even Fixation disparity, rules involving fusional reserves, when the patient has good visual acuity, reading speed and rules based on phoria magnitude can all be useful is likely to be reduced in older patients because of in indicating how much prism should be prescribed. contrast, motor, and attention deficits.24 Checking the advantage obtained from the prism can Many satisfactory reading charts are available for be prudent by introducing the prism of the indicated testing normally sighted patients. Reading charts with power and orientation and asking the patient to report larger size ranges and more systematic design features on the clarity or comfort of vision while observing fine have been designed by Keeler,21 Sloan,30 Bailey and print. The prism is then removed and reintroduced Lovie,7 and Legge et al.22 after a pause, but with the base direction changed 180 degrees. If a patient with exophoria does not prefer ASSESSMENT OF BINOCULAR VISION base-in to base-out prisms, judged by changes in As patients grow older, they are more likely to have clarity or by relative difficulty in adapting to the some ocular motor difficulties because of changes change, the decision to prescribe prisms should be affecting the neuromuscular mechanisms and the carefully reconsidered. With vertical prism, the prism structural tissues around the eyes. In examining power magnitudes are usually smaller, and making binocular coordination, care should be taken to this kind of change may be more convenient by observe the version movements of the eyes as they keeping the prism in the same orientation but move in the six cardinal eye movement directions transferring it to the other eye, changing from 2 BUR (right, left, up and right, down and right, up and left, to 2 BUL, and so forth. and down and left). A relative lagging of on eye Anisometropia creates special problems, especially indicates an oculomotor dysfunction that warrants a relating to vertical phorias. Younger patients with more detailed evaluation of the noncomitancy. anisometropia can use a forward or backward head tilt The cover test should be carefully and routinely to achieve viewing through the optical centers of the performed at distance and near for older patients. lenses, which avoids differential prismatic effects. Older patients lack accommodation and have no Older patients wearing bifocals must move their eyes stimulus to accommodative convergence; thus they in downgaze to view through the bifocal segment show more exophoria at near. Vertical deviations are when they read. When patients are already wearing a also more common in older adults. Phorias or tropias bifocal correction for anisometropia, decision making should be measured at both distance and near by using is easier. Unless refractive error has substantially loose prisms. When large near exophoria is found, the changed, the patient’s need for vertical prismatic strength of the fusional vergence mechanism can be correction can be tested at distance and at near with judged by the facility and speed with which the patient methods, such as those previously described, using the makes vergence eye movements to obtain fusion when patient’s old glasses. Many patients with a baseout prism (e.g., 10 prism diopters) is introduced anisometropia may exhibit significant vertical heterophoria at near, but they do not have symptoms patients.8,31 or show a strong preference for having a correcting When measuring visual fields, the clinician should prism in place. Each case should be considered be conscious of the purpose of conducting the test individually. When the anisometropia is newly (Box 7-1). acquired, perhaps because of a myopic shift in one The stimulus parameters and testing strategies will eye, symptoms and adaptation difficulties are more vary accordingly. Today most visual field testing is likely. Some practitioners prefer to prescribe some done with automated perimetry instruments that overall vertical prism to minimize such vertical phoria present lights at various luminosities at selected problems at near. Others choose to prescribe bifocals locations in the visual field following computer with no special prism compensation, but they may controlled sequences. The presence of risk factors and warn the patient of possible symptoms and adaptation symptoms associated with glaucoma and other difficulties; this strategy avoids prescribing a special neurological and retinal diseases guides the clinician’s prism until the patient fails to adapt. choice of which field tests and what testing strategies The remedies for the bifocal problems in should be used. The Humphrey Visual Field Analyzer anisometropia are to use slab-off or other (Carl Zeiss Meditec AG, Jena, Germany) and the prismcontrolled bifocals, executive bifocals where no Octopus (Bio-Rad, Cambridge, Mass.) are the two prism is present at the dividing line, Franklin split-lens most widely used automated perimeter instruments. bifocals, or asymmetrical bifocal segments (e.g., a They both offer a wide range of options for selecting round segment in one eye and flat top in the other) or different sets of stimulus locations by using different to revert to separate distance and reading glasses. strategies for determining thresholds in given Fresnel press-on prisms can be cut so they are locations. They can also check the consistency of the confined to the bifocal segment region. Although they patient’s responses and their maintenance of fixation. are not often used as a permanent solution, they can be The visual field testing programs for screening are of useful in investigating the potential value of a relatively short duration (often 2 or 3 minutes), with prismatic correction in the bifocal segments. fewer points tested and fewer presentations at each Several tests can determine whether a patient truly location, whereas more extensive and longer routines does have binocular vision in a particular situation. ranging from 7 to 20 minutes per eye may be used for Good stereoacuity, the ability to see both monocular monitoring and for more thorough diagnostic targets on a fixation disparity test, and fusion with the purposes. The results for a given eye can be analyzed Worth four-dot test are useful standard criteria. The in different ways. Summary statistics, such as the simple bar-reading test is sometimes overlooked; mean deviation, provide an index of the average holding a pen midway between the eyes and the page reduction in visual sensitivity compared with value to of print should not obscure any point if simultaneous normal visual field for the age-matched population. binocular vision is present. Graphic display printouts typically show the regional VISUAL FIELD MEASUREMENT variations in visual sensitivity with gray scales to indicate the severity of reductions in visual sensitivity. Visual field losses are more common in older patients. Such plots may show absolute threshold values, Field defects may come from glaucoma, chorioretinal reductions relative to the thresholds for an agematched disease, optic atrophy, and visual pathway disorders. normal population (commonly called “total Also, visual sensitivity is reduced with age and, for a deviation”), and regional reductions relative to the given visual stimulus strength, the measured visual individual’s overall sensitivity level (“pattern BOX 7-1 deviation”). Most of the automated perimetry devices Purposes of Testing concentrate on testing the central 25 to 30 degrees of the visual field. The characteristics of field loss in glaucoma have influenced many of the testing and To screen for otherwise unsuspected pathological conditions analysis strategies. The glaucoma hemi-field test To seek evidence that will confirm the presence of an analyses threshold data and compares the relative already suspected pathological condition sensitivity of selected regions in the superior and To monitor the progress of a previously identified field inferior visual fields, looking for patterns defect characteristic of glaucomatous field loss. To evaluate the impact that the field loss already known to be present will have on the person’s ability to Display technology and advances in visual science function have lead to the development of new visual field tests field becomes reduced in size for older that specify properties of visual processing of information originating in different regions of the The classic perimetric techniques of tangent screen visual field. They attempt to identify deficits in and bowl perimeter examination for fields are less specific neural processing mechanism that may be commonly used today, but they remain the best especially vulnerable to certain diseases. Again, the methods for determining the shape and location of central visual fields receive the most attention. The scotomas. The targets may be spots of various sizes or frequency-doubling perimetry test is a central visual lights of various luminosity and sizes at the end on a field test in which a large area (5 degrees square) of handheld wand, or they may be projected spots of flickering grating is presented in one of 17 different light, usually with variable luminance and size. locations. The grating has a spatial frequency of less Illumination conditions such as luminance of the than 1 cycle per degree, and when presented in rapid illuminated perimeter bowl, or the ambient counterphase flicker (more than 15 Hz), there is an illumination on the tangent screen, need to be illusion that twice as many stripes are in the target controlled and a record should be kept of the test pattern.20 This frequency-doubling illusion depends on conditions. Usually most of such testing is done with the sparse large-diameter magnocellular nerve fibers, kinetic perimetry, in which the clinician moves the which are believed to be especially vulnerable to chosen target across the visual field. Sometimes static damage from glaucoma. The visual system is more perimetry techniques are used; a target location is sensitive to contrast at the higher spatial frequency. chosen and the clinician turns the target on and off The test measures contrast thresholds for detecting the while the patient reports when the target is seen. grating in each of the selected locations. This test is The test parameters (target size and luminance as reported to be sensitive for the early detection of well as background luminance) and strategies for glaucoma. The visibility of the stimulus is relatively presentation will vary according to the purpose for unaffected by optical defocus, ambient illumination, conducting the test. pupil diameter, or media clarity. Another test that For screening, test spots should be just comfortably shows good sensitivity to early losses in glaucoma is detectable, and a systematic broad search should be the short wavelength automated perimetry (SWAP), in made of the whole visual field. For confirming which the a large blue target is presented on a bright tentative diagnoses, the test targets should be just yellow background.19 Some automated perimetry detectable—and only just detectable in the region procedures use temporal variations and involve where the field defect is most likely to occur. The test detection of flickering stimuli or detection of motion target presentation should be confined largely to this or displacements. High-pass resolution perimetry is region of the visual field, and the motion of dynamic performed on a display screen, and the patient’s task targets should be such that the direction is is to see rings that have a light central region with a approximately at right angles to the probable border of dark region on either side. The average luminance of the scotoma. Results are more reliable and the the dark and light regions is equal to the luminance of scotoma shape becomes better defined if the direction the background. The diameter of the rings and the of motion goes from nonseeing to seeing. widths of the dark and light components are gradually To monitor the progression of visual field defects increased until the ring can be seen in different regions with tangent screen or bowl perimetry techniques, the of the visual field. stimulus conditions should be identical (or as similar Automated perimeters do include some programs as possible) to those previously used. Again, any target that present stimuli beyond the central 30 degrees, motion should be orthogonal to the known border of typically testing out to 60 degrees. Testing in these the scotoma. more peripheral regions is obviously important in For functional evaluation of the visual fields, some diseases (e.g., retinitis pigmentosa, retinal binocular observation may be more relevant then the detachment, visual pathway disorders). monocular fields.23 Relatively easy to see targets The automated visual field testing procedures have (large or bright) should be used. special advantages that come mainly from consistent Special problems may be associated with visual control of the test stimuli, the test procedures, and the field measurement in low vision patients. If a central computerized analysis of the results. They are not as scotoma is present, two alternative strategies may be useful for mapping out the detailed shape of scotomas used. One is to have the patent look at the fixation spot or for testing the more peripheral parts of the visual by eccentric viewing. Patients with central scotomas field. Detailed information about the shape and often develop a preferred retinal locus (PRL) that they location of scotomas across the entire visual field can use for giving direct visual attention to an object. This be very important for predicting functional abilities. may be many degrees away from where the anatomical fovea was located. Allowance for this functional difficulties. However, a patient often will displacement must be made when interpreting the not recognize scotomas because “filling in” seems to visual field results. The central scotoma region will be occur. Indeed, the normal physiological blind spot located to one side of the fixation point. The second usually cannot be observed on the Amsler grid pattern. alternative is to use a fixation cross centered on the Useful information is obtained about the patient’s fixation point. Elastic cord, masking tape, or chalk vision function when visual disturbances are reported may be used on the tangent screen to provide a cross on the Amsler grid test. When no visual disturbance is through the central point. The patient is instructed to observed by the patient, however, no definite look toward the center of the cross, even though he or conclusion should be made about the presence or she may not see the actual intersection. Flashing the absence of scotomas. target can make it easier for the patient to maintain central fixation because patients are less tempted to COLOR VISION TESTING move their eyes to check on the presence of the target The purpose of testing color vision is twofold. First, when it is flashing. the identification of color vision anomalies can assist Functional visual field testing is important in low in the diagnosis or detection of pathological changes vision patients. Whenever frank scotomas are found in the visual system. Second, altered color vision can on the tangent screen or bowl perimeter, a much cause some difficulties with color discrimination coarser test of functional detection ability should be tasks, and the possibility of such functional difficulties made by using larger and more visible targets. A hand should be discussed with the patient. or piece of paper may be used as a target against a Color discrimination usually changes slightly as the black screen to establish whether the scotoma is truly patient ages because of yellowing of the crystalline absolute. lens and physiological and pathological changes in the Coarse screening for peripheral field loss may be macular region. Such acquired defects tend to be performed by using confrontation or similar tritanopic, the most obvious manifestations being a techniques.10 With confrontation testing, the patient’s reduction of color discrimination ability for the blue visual field is compared to that of the clinician. The and blue-green regions of the spectrum. The clinician closes one eye, the patient closes the opposite congenital color defects found in approximately 8% of eye, and they each look toward the open eye of the the male population (0.5% in women) are almost other. In a vertical plane midway between their eyes, always of the deuteranopic or protanopic types, and the clinician introduces the test stimulus, which may the main color discrimination difficulties are in the be a handheld target or the clinician’s fingers. It is “tomato” region of the spectrum (green, yellow, though the clinician and the patient are looking at clear orange, red). The congenital color vision defects do glass screen from opposite sides, and the anatomical not cause new functional problems in older patients. limitations of the peripheral fields from the brow, The test of choice for the routine assessment of nose, and cheek should project to similar locations for color vision in older patients is the Farnsworth Panel the patient and the examiner. If no substantial D-15 test, in which 15 colored chips are arranged so peripheral field deficits are present, the point of that they appear to be in order according their appearance and disappearance of the test target should chromatic similarity. Patients with normal aging be at approximately the same location for both changes affecting color vision typically make only a clinician and patient. An alternative technique is to few smallmagnitude errors of the tritanopic type. move the target along an arc beginning from behind When retinal disease is present, however, the number the patient and simulating a sweep across a bowl and magnitude of errors in arranging the D-15 targets perimeter. This pseudoperimeter technique enables are greater. In cases of substantial retinal pathology, better testing of the more peripheral regions of the the magnitude of errors in arranging the D-15 test field, especially on the temporal side. targets is large, and the pattern of the errors is more The Amsler grid can be a useful test of central random (see Chapter 2 for further discussion of age- visual function, characterizing disturbances of central related vision changes). vision.29 Patients may report absences, fading, or OTHER TESTS OF OCULAR OR distortion in parts of grid pattern while they maintain fixation on its center. When patients report observable VISUAL FUNCTION changes, the practitioner may gain insights into the A variety of clinical tests of visual functions can be nature of the visual disturbance and perhaps may be useful in identifying the presence of ocular better able to predict or understand the patients’ pathological changes, for making diagnostic distinctions, or for explaining functional difficulties visual acuity or contrast sensitivity, tested with and resulting from the disease. Contrast sensitivity losses without the presence of a glare source. The Brightness of small magnitude are common in older adults, and Acuity Tester is a device that has a 6-cm diameter more severe losses of contrast sensitivity accompany hemispherical bowl of controlled luminance held over many of the ocular and visual pathway disorders the eye.18 The patient observes a visual acuity or associated with aging. No close relationship between contrast sensitivity chart through an aperture in the visual acuity and contrast sensitivity exists; center of the bowl. A more analytical assessment of sometimes one function may be significantly reduced light scatter and glare can be made by a method while the other may be scarcely affected. Mobility and introduced by Van den Berg33 in which scattered light driving performance and many other tasks of daily from a flashing bright annulus of light can induce a living are more affected by impaired contrast flickering appearance in a steady, central, spot target. sensitivity than by impaired visual acuity. Introducing counterphase flicker of variable intensity Contrast sensitivity measurements are mainly into the central spot provides a means of nulling the useful for predicting functional abilities, but they can flickering appearance induced by the light scattered also have value in making diagnostic decisions and in from the annulus. This effectively quantifies the understanding the nature of a person’s vision loss. scattered light. Low-contrast letter charts with a Three basic approaches for measuring contrast surrounding field of glare have been shown to be sensitivity are taken. The traditional method is to sensitive measures of disability glare.5,28 Most present sinusoidal grating targets at selected spatial clinicians do not have glare tests at hand, and a less- frequencies. Then contrast is varied to determine the controlled assessment of disability glare can be made minimal contrast required for detection of the striped by shining a penlight at the patient’s eye as a visual grating pattern for each of the selected spatial acuity chart is being read. frequencies. The contrast sensitivity function is a Retinal adaptational mechanisms may be impaired graph showing how contrast sensitivity varies with by some age-related eye diseases, and dark adaptation spatial frequency (see Chapter 2). The grating displays and glare recovery tests may identify such losses. may be presented on oscilloscope or video screens or Sophisticated instrumentation is available for testing on printed chart displays.16 The second method is to dark adaptation and glare recovery, but some relative measure visual acuity with low-contrast letter charts or functional assessments may be made by testing the that effectively determine the spatial frequency limit patient’s ability to see objects in very dim light or by for resolution at selected contrast levels.27 The third measuring the time taken for maximal visual acuity to method is to present a sequence of large targets, such return after exposure to a strong light such as from a as large letters or edge targets, in which a progression penlight held close to the eye. Differential diagnosis of reducing contrast is shown, and the lowest contrast of pathological conditions may be facilitated by the at which the target can be recognized is the measure use of electroretinograms, electro-oculograms, of contrast sensitivity.4,26,34 The most widely used fluorescein angiography, measurement of responses to contrast sensitivity test is the Pelli-Robson chart, flicker, special tests of color vision function, and which has a series of large letters (49-mm high) with visually evoked cortical potentials. a progressive reduction in contrast in which each successive set of three letters becomes lower in contrast by 0.15 log units (70%). Patients read as far as possible down the chart until reaching their threshold contrast. Disability glare is more of a problem in older patients because all develop increased intraocular light scatter as a result if inevitable aging changes in the lens of the eye. Light scatter becomes more pronounced with the development of cataract or with disorders affecting the cornea or the vitreous. Tests of disability glare can be useful for monitoring the development of cataract or other medical opacities or for the prediction of functional difficulties that may be experienced under glare conditions. The common feature is that all glare tests measure a visual function,