OPT 015: Clinical Refraction Notes.pdf

OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Optometers are the autorefractors and visual ana...

OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Optometers are the autorefractors and visual analyzer. MODULE 1: INTRODUCTION TO REFRACTION Autorefractor is a refraction carried out with an instrument which generally uses infrared light. Retinoscope is an objective instrument used for R.A. 8050 or Revised Optometry Law of 1995 determining the patient’s refractive status based on the fundus reflex. An act regulating the practice of optometry, upgrading optometric education, integrating Subjective Refraction optometrists, and for other purposes. Determination of the refractive state of the eye entirely based on the patient’s subjective responses Refraction or judgments. Its technique is comparing one lens against another, changing in vision as the criterion, to arrive at the To simply determine the refractive state of the eye. dioptric lens combination that results in maximum According to Michel Millodot, Refraction is the visual acuity. process of measuring and correcting the refractive errors of the eyes. Cycloplegic Refraction To simply determine the set of grades or Determination of the refractive state of the eye using prescriptions that will enable the patient to attain the cycloplegics. best vision possible. It is a multi-step process that involves a combination Cycloplegics are drugs which paralyze the ciliary of psychomotor skill and intellectual muscle (accommodation). problem-solving. The process allows the examiner to arrive at one individualized prescription, from a Stenopaic Refraction universe of approximately 200,000 possible prescriptions. (Carlson, Kurtz & Heath). It is a refraction done with the use of a stenopaic slit. Goal and Endpoint Automated Refraction The goal and endpoint of refraction is to render the retina conjugate with the optical infinity through the Determination of the refractive state of the eye using application of lenses in front of the eye or simply to a computerized measurement of the refractive error identify the lenses which will allow the patient of the patient. achieve: clear and comfortable vision. It can either be subjective or objective. Refraction is a problem-solving, not merely a technical exercise. FAQs Is the Automated Refractor reliable and accurate? Automated Refractor (AR) is an instrument that helps MODULE 2: DIVISIONS OF ROUTINE EYE the Optometrist spend less time in Refraction. With its EXAMINATION AND TYPES OF REFRACTION continuing upgrade, most ARs are reliable and can be checked for accuracy by calibration. But it is still highly recommendable to do Subjective Refraction or 3 Divisions of Routine Examination Refinement because there are factors such as patient’s compliance and instrument’s calibration that will give 1) Starting Point: preliminary information of the either too high or too low refractive results. refractive status of the patient 2) Refinement: predictions tested and refined SUMMARY TABLE (phoropter) Objective Procedures vs Subjective Procedures 3) Endpoint Techniques: includes binocular balance OBJECTIVE SUBJECTIVE and trial frame technique Does not rely on the Relies on the patient’s patient’s response response Types of Refraction Signs Symptoms Basis: Results found by Basis: Patient’s response, using an instrument or complaints and own Objective machine description Subjective Cycloplegic Stenopaic MODULE 3: RETINOSCOPY Automated Objective Refraction Objective Refraction (Retinoscopy) Determination of the refractive state of the eye based on the optical principles of refraction Objective Refraction (Retinoscopy) is to (objective Optometer, retinoscope or photorefractor) objectively determine the refractive status of the eye without the need for subjective responses on the relative to the point of fixation. part of the patient. It is the starting point for subjective refraction. It may be heavily relied on as the final prescription Optometer contains an optical system which of patients that are unable or unwilling to give determines the vergence of light reflected from the reliable subjective responses. object’s retina. Electronic optometers are the types in which all data appears digitally. Examples of 1 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 The far point is brought to the instrument with trial Retinoscopy lenses. The basic principle is that of Foucalt’s method of It is performed on infants, mentally infirm, low vision determining the focal power of a lens. patients and uncooperative or malingering patients. Being considered a lens of unknown power, the It is also helpful in objective determination of the lag refractive status of the eye can be determined by of accommodation during use of the eyes at near. locating its conjugate foci in space with a source at More reliable (if performed correctly) than subjective a known point. refraction and can break down latent hyperopia and Pseudomyopia. 2 Systems in Retinoscopy Advantages of Retinoscopy 1) Provide a starting point for subjective refraction and I. Illumination System independent comparison for subjective results. Involves the light from the apparent and real source 2) More reliable than subjective when patients are and the image of that source upon the fundus. unable or unwilling to give appropriate responses. It can be adjusted to emit parallel, divergent or 3) Can sometimes break down latent hyperopia or convergent rays. Pseudomyopia. The rays are reflected toward the patient’s eye by a 4) Can identify signs of accommodative dysfunctions, plane angulated mirror and seem to come from an ocular media opacities and certain ocular apparent source whose location determines the pathologies. position of the illuminated fundus patch. Only when the apparent source is between the eye History of Retinoscopy and the instrument is the fundus image opposite to its rotation. Sir William Bowman (1859) noticed a peculiar None of the fundus displacements are influenced by reflex in the pupil of astigmatic eyes that occurs the patient’s ametropia. during ophthalmoscopy. Meagan publicized the method. II. Observation System Chilret proposed the term “Skiascopy” Involves the light starting at the fundus and the Cuignet (1873) made known the clinical use of peephole of the instrument, which serves as the retinoscopy in qualitative determination of refractive point of conjugation. status. He used the plane mirror to measure The rays originate at the patient’s fundus. astigmatic errors. They are reflected from the pigment epithelium and Landolt (1878) made explanations of the optical underlying choroid, thus creating a red-orange concepts underlying retinoscopy. reflex. Parent (1880) updated the optical theory and began The retinoscopic reflex may be against, with or to quantitatively assess the refractive error through neutral. the use of lenses. In 1881, he introduced the name The movement depends upon the ametropia of the “Retinoscopy”. patient. Priestley-Smith (1884) suggested the name “Shadow Test”. Jackson and Copeland (late 19th century and Classification of Retinoscopes According to early 20th century) gave retinoscopy a great Illumination System emphasis. Andrew Cross (1911) pioneered Dynamic According to Light Source Skiametry. Charles Sheard (1920) developed his own method Non-luminous or Reflecting - is a mirror with an of dynamic retinoscopy and introduced the concept aperture which reflects a source placed before the of “Lag of Accommodation”. mirror Copeland (1927) developed the “Streak Self-illuminating - the real source of illumination is Retinoscopy”. contained within the instrument and reflected into Tait (1953) found an average of +2.25D lag of the eye by a mirror which is part of the device accommodation of Sheard’s method. According to the Mirror Used Synonyms of Retinoscopy Plano Mirror - the apparent source of light will lie Retinoscopy - means vision of the retina behind the instrument (misnomer) was used by Parent. It was the Concave Mirror - the source will appear to lie in accepted name in English-speaking countries. front of the instrument Skiascopy - means vision of the shadows by Chilret was accepted name in non-English-speaking According to the Bulb Used countries. Spot - usually achieved by a diaphragm over the Other Names: Skiametry, Umbrascopy, bulb Pupilloscopy, Retinoskiascopy, Keratoscopy, Streak - achieved by the line filament of the bulb Shadows Test, Koroscopy & Keralampsiskopie itself. It is more useful for determination of astigmatic corrections by assessment of the axis of Optical Principles the cylinder and refractive powers in the two primary The criterion of ametropia is the far point and that meridians. is what the retinoscope measures. With or against motion occurs according to A plane mirror adjustment moves the fundus image whether the instrument is inside or outside the eye’s in the same direction as the rotation of the far point and remains neutral when the far point instrument. coincides with the peephole. 2 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 A short focus concave mirror adjustment moves Factors Neutrality Low High the fundus image in the opposite direction as the Ametropia Ametropia rotation of the instrument. Clarity Very Sharp Sharp Dull Intensity Very Bright Bright Very Dim Note: Modern Retinoscopes permit movement either Size Pupil is Filled Large Small filament of the bulb or the condensing lens which alters With Light the effect of the mirror from plano to concave as Speed of Infinitely Fast Fast Slow desired. Motion or Neutral Form or Round or Oval or Low Band-like or FAQs Shape Simple Astigmatism High Why is Retinoscopy the Starting Point of Subjective Myopia Astigmatism Refraction? Because it gives the Optometrist the refractive condition, and even the prescription, of the patient and Fundus Reflex Movement refine it during Subjective Refraction. With Movement What cases where Retinoscopy results are used as the final prescription? The movement of the light reflex is in the same Retinoscopy results are relied more on the cases of direction as the movement of the retinoscopic beam unresponsive or uncooperative patients such as of light. patients with low vision, children, bed-ridden and even It indicates hyperopia, emmetropia or myopia malingering patients. less than working distance. Against Movement MODULE 4: STATIC RETINOSCOPY SPHERICAL The movement of the light reflex is in the opposite ERROR direction as the movement of the retinoscopic beam of light. It indicates myopia greater than the working Retinoscope distance. A retinoscope is a small, handheld device that Point of Neutrality emits visible light toward the pupil of the eye being It is also known as Point of Reversal. analyzed and allows the operator to view the It is the point at which the motion of the reflex red-orange reflex of light reflected back through the cannot be detected or determined either by placing pupil from the ocular fundus. lenses before the eye or by moving the retinoscope It has a reflecting surface perforated or half-silvered to a point in space conjugated with the retina. to view the patient’s eye through a central aperture. It is the point at which the motion of the reflex It is also known as Pupilloscope, Skiascope, etc. changes from with motion into against motion or vice versa and the pupil appears to be filled with Internal Parts light. Condensing Lens Bulb Types of Retinoscopy Batteries External Parts According to the Distance of the Target and Forehead Rest Accommodation Peephole Static Retinoscopy - the patient is asked to fixate On/Off Switch at a distant object Body Dynamic Retinoscopy - the patient is asked to Streak Rotator fixate at near and the accommodation is at its Spring cap maximum Dust Shield Mirror According to the Method Light Streak Width Adjustment Stable Method ○ Working without Working Distance Lens (WDL) Fundus Reflex ○ Working with WDL Mobile ○ Creeping Fundus Reflex is a light reflected from the fundus ○ Use of Auxiliary lenses that appears as a red glow (red-orange) in the plane of the pupil, as observed in retinoscopy, due to the reflected light having passed through choroid. Static Retinoscopy Factors Affecting the Reflex Static Retinoscopy is done to objectively Clarity determine the distance refractive status of the Intensity patient’s eyes with accommodation relaxed. Size The results of this technique will serve as a starting Speed of Motion point for the subjective refraction or as the final Form and Shape prescription if the patient is unable to respond to subjective testing. 3  OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Set-Up With Movement Room Illumination: Dim The movement of the light reflex is in the same Test Target: Big E or Any Big Distant Object direction of the movement done by the examiner. (Snellen’s Chart) Introduce plus lens Test Distance: Patient looking at far or 20 feet (6 It indicates: meters) and the Examiner 16 inches or 20 inches ✔ Hyperopia from the patient ✔ Emmetropia or Control Lens: Plano, Working Distance Lens, ✔ Myopia lesser than the Working Distance Lens Retinoscopic Lens Against Movement Procedure The movement of the light reflex is in the opposite 1) The patient removes his corrective lenses (habitual direction of the movement done by the examiner. lenses). Introduce minus lens 2) Disinfect the surface of the phoropter. It indicates: 3) Adjust the interpupillary distance (IPD or ✔ Myopia greater than the Working Distance Lens PD-pupillary distance) for far. 4) Instruct the patient to keep both eyes open during Static Retinoscopy: Spherical Error retinoscopy and ask the patient to inform you if your head blocks his view of the fixation target (distant target). If the error is spherical, the reflex within the pupil will 5) The examiner will also keep both of his/her eyes be continuous with the intercept of the streak (on open in performing retinoscopy. the patient’s eye/face). 6) The examiner’s right eye will examine the patient’s right eye and vice versa (right to right; left to left). Step No. 4: Static Retinoscopy at 20 Inches The unexamined eye of the patient should not be Examples: occluded but you can place retinoscopic lens 1) Without WDL (Working Distance Lens) (located in the phoropter). 180th and 90th Meridian 7) Hold the retinoscope at 20 inches (or 16 inches) Initial Reflex Movement (IRM): With from the patient’s eye. The examiner will hold the retinoscope with his right hand to examine the +2.75D — against (PR) patient’s right eye. +2.50D — with (GNL) 8) Scope the vertical meridian (90th meridian) and the +2.25D — with horizontal meridian (180th meridian). +0.25D — with 0.00D — with Position of the Streak Net #4: = GNL - WDL Net #4: = +2.50D - 2.00D Net #4: = +0.50D Refractive Status/Diagnosis: Hyperopia 2) With WDL 180th and 90th Meridian IRM: Against Working Distance Lens +2.00D — against Working distance lens is the distance of the +1.75D — against examiner from the patient converted to diopters. 0.00D — against Formula: D = 1/f -0.25D — against ○ Example: 16 inches -0.50D — against ○ D = 40 inches/16 inches -0.75D — with (PR) ○ D = 2.50 Count the number of clicks and multiply with 0.25 Focal Length Diopter Formula Another way: 2.00 + 0.50 = 2.50 Meter (m) 1/f The sign will depend on the movement of lens Decimeters (dm) 10/f change: Centimeters (cm) 100/f ○ positive to negative – negative sign ○ positive to more positive – positive sign Millimeters (mm) 1000/f Inches (in) 40/f Net #4: = GNL Net #4: = -2.50D 2 Methods of Retinoscopy Refractive Status/Diagnosis: Myopia greater than WDL I. Working without WDL (Working Distance Lens) FAQs Formula: Net #4 = GNL-WDL Why is Static Retinoscopy called Static? Because in this procedure, the patient is asked to focus II. Working with WDL (Working Distance Lens) at far and thus causes the accommodation to relax. Formula: Net #4 = Gross #4 Retinoscopy is best done under dim illumination where the pupils are dilated. 4 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 MODULE 5: STATIC RETINOSCOPY ASTIGMATIC Break Phenomenon ERROR The Break Phenomenon happens when the reflex within the pupil is not continuous with the intercept Static Retinoscopy: Astigmatic Error of the streak on the patient’s eye. This is immediately observed and it’s the most Procedure commonly known indicator of astigmatic error. 1) Instruct the patient to look at the fixation target. Examine the patient’s right eye. 2) Determine if the error is spherical or astigmatic by rotating the streak of the retinoscope through 360 degrees. Observe for the Break Phenomenon, Thickness Phenomenon and Skew Phenomenon. 3) If the error is spherical, observe the reflex for with or Thickness Phenomenon against motion. Remember: a) Plus Lens - for with motion or movement In Thickness Phenomenon, as the streak is b) Minus Lens - for against motion rotated through 360 degrees, the thickness of the 4) To neutralize an astigmatic error, identify the 2 reflex within the pupil will be constant in a spherical Principal meridians. Then neutralize each meridian error and vary in astigmatic error. separately. When using the phoropter with minus The thickness of the fundus reflex indicates the cylinders, one meridian is neutralized with a sphere amount of Ametropia (see Factors of Affecting the only while the other meridian is neutralized with a Fundus Reflex). cylinder in addition to the sphere. Neutralize: a) Weaker With Motion first if both meridians exhibit with motion b) Stronger Against Motion first if both meridians exhibit against motion c) With Motion first if one meridian exhibits with Skew Phenomenon motion and the other meridian exhibits against motion In an astigmatic error, the streak is swept (scoped) 5) When neutrality is reached, recheck all meridians across the patient’s pupil, if the streak is aligned with the sleeve of the retinoscope in both the plane with one of the principal meridians, the reflex within mirror and the concave mirror position. If true the pupil will move parallel to the movement of the neutrality is achieved, all meridians will look neutral streak on the patient’s face (eye). regardless of the position of the sleeve of the But if the streak is not aligned with one of the retinoscope. principal meridians, the reflex will move in a different 6) The lens that produces neutrality is called the direction of that streak. Gross Retinoscopy Finding or Gross Note: Skew Phenomenon is absent in a spherical Neutralizing Lens (GNL). Leave the lens that error. neutralized the patient’s right eye and neutralize the left eye. 7) To convert the gross retinoscopy finding to net finding, algebraically add a spherical minus lens equal to your working distance in diopters to the spherical lens that produced neutrality. This is the net static retinoscopy finding that makes the patient’s eye conjugate with infinity. Examples: 8) Measure the patient’s visual acuity in each eye 1) Static Retinoscopy at 20 Inches Without WDL through the net static finding. 180th Meridian 90th Meridian Tips IRM: With IRM: With If reflex motion is slow, dull, dim and narrow, the +2.75D — against (PR) +2.00D — against (PR) error is high. Therefore apply big lens changes like +2.50D — with (GNL) +1.75D — with (GNL) 1 diopter or 2 diopters changes. +2.25D — with +1.50D — with If the reflex is fast, bright sharp and the pupil is 0.00D — with 0.00D — with almost filled with light, the error is low or you are approaching neutrality therefore apply small lens Computation A changes like 0.25 diopters. 180th M: +2.50D – 2.00 = +0.50D If motion is with neutralize with plus lens and if the 90th M: +1.75D – 2.00 = -0.25D motion is against neutralize with minus lens. = +0.50 cyl x 180 = -0.25 cyl x 90 Use sphero-cylindrical method. In the Phoropter method, neutralize weaker with or Net #4 = +0.50sph = -0.75 cyl x 90 stronger against motion first. Ref. Stat.: Mixed Astigmatism, ATR In the Trial Case Method, neutralize any meridian Against-the-Rule Astigmatism first. Computation B SPAM 180th M: +2.50D 90th M: +1.75D Same = Plus lens = +2.50sph = -0.75 cyl x 90 (GNL) Against = Minus lens - 2.00sph (WDL) 5 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Net #4 = +0.50sph = -0.75 cyl x 90 Reveals the degree to which accommodation is Ref. Stat.: Mixed Astigmatism, ATR fluctuating at near and if eyes are balanced equally at near 2) Static Retinoscopy at 20 Inches With WDL Near imbalance could be the result of: ○ Unequal accommodation between the 2 eyes. 180th Meridian 90th Meridian ○ Unequal accommodation demand as in IRM: With IRM: With Anisometropia. +2.50D — against (PR) +2.00D — against ○ Improper balance of the distance refractive +2.25D — with +1.75D — with (PR) correction. +2.00D — with +1.50D — with No WDL is added to or subtracted from the finding and static finding in place Computation 180th M: +0.25D 90th M: -0.50D Dynamic Retinoscopy = +0.25 cyl x 180 = -0.50 cyl x 90 Net #4 = +0.25sph = -0.75 cyl x 90 Dynamic Skiametry (retinoscopy) was pioneered Ref. Stat.: Mixed Astigmatism by Andrew J. Cross. 3) Static Retinoscopy at 20 Inches Without WDL Procedure 1) Start with the static finding. 180th Meridian 90th Meridian 2) For with motion add plus lenses beyond the neutral IRM: With IRM: With until reversal occurred. +1.00D — against (PR) 0.00D — against The concept of Lag of Accommodation was +0.75D — with -0.25D — with (PR) introduced by Charles Sheard (1920). +0.25D — with -1.00D — with 0.00D — with -1.25D — with Procedure Computation 1) Done by adding plus lenses to the distance 180th M: +0.75D 90th M: 0.00D retinoscopy lenses until neutrality is reached. = +0.75 cyl x 180 = 0.00 cyl x 90 2) Charles Sheard believed that the normal Lag of Accommodation was 0.50D or slightly more. He Net #4 = +0.75sph = -0.75 cyl x 90 routinely subtracted 0.50 from Dynamic Findings. - 2.00sph (WDL) Example: Static Finding = +1.25D Net #4 = -1.25sph = -0.75 cyl x 90 Dynamic Finding = +2.50D Ref. Stat.: CMA (Static Finding) 1.25 – 2.50 (Dynamic Finding) = 1.25D 1.25 – 0.50 (lag) = 0.75D FAQs Did you know that Astigmatism is a common Refractive condition? Other Methods Of Retinoscopy Astigmatism is a common refractive condition. It nearly affects 2/3 of the population according to BOOK RETINOSCOPY rosineyecare.com. Some have symptoms while others don’t know it. We have a physiological astigmatism of It was introduced by Gessel and Bulls (1949). 0.25 to 0.50 cylinder. The target is a rectangular aluminum on which simple pictures were projected in sequence. The test distances used are 15 feet, 7 feet and 20 MODULE 6: DYNAMIC RETINOSCOPY inches. For children 2 years old and above, the retinoscopy is performed while the child is looking at pictures in Dynamic Retinoscopy a book. The examiner observes the following: Is performed at near to determine the lag of ✔ Dullness or brightness of the reflex accommodation objectively. ✔ Color of the reflex Lag of Accommodation is the adjustment of the ✔ Speed, range, promptness, pick-up and release eye to focus from far to near. of motion Dynamic Retinoscopy reveals whether the system ✔ Meridional differences is lagging off more than normal. If the reflex increases in brightness the moment the child identifies an object, a registering against Lag Of Accommodation motion indicates increase in accommodation. He described the color: If lag is greater than +0.75D, there is inadequate ✔ Dull Red - high plus or minus accommodative response as a result of: ✔ Bright Pink - low minus ○ Near Esophoria ✔ Dull Pink - low plus ○ Accommodative Insufficiency ✔ White Pink - plano ○ Uncorrected Hyperopia ✔ White - plus (+0.50D to +0.75D) If lag is less than +0.50D, patient is: ○ Over accommodating significantly as a result of Note: The farther the child’s visual development has near exophoria progressed, the more likely it is that the reflex will be ○ Spasm of Accommodation found to be white pink or white. 6 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Procedure 4) The examiner, while observing the direction of the 1) The fixation target is a white card containing a 1⁄2 motion of the reflex in the patient’s pupil, will slowly inch hole, having letters, words or pictures move the ball towards the patient’s face until neutral appropriate to the child’s age printed within 1⁄2 inch motion is observed in each principal Meridian. of the hole. This card is attached to the retinoscope by means of a clip, so the beam passes through the The position of the ball at neutrality is determined by hole in the card. the use of a yard stick, one end held at the 2) The examiner is seated slightly below the patient’s patient’s cheek (zero) and the other held by the eye. The child is in a downward gaze as would examiner (over his ear or shoulder). occur when reading. The “Harmon Distance” Neutrality occurs when the ball is located about 15 (distance from the elbow to the knuckles) which for to 16 inches from the patient’s face resulting in a the child is 8-10 inches. lag of accommodation from 0.50 to 0.75D. 3) The child is instructed to read the words aloud or describe the pictures and the examiner quickly NOTT TECHNIQUE moves the vertical streak across the pupil, while It was introduced by Nott. noting the motion present (against or with). 4) Using a hand-held trial lens or a retinoscopic rack Procedure (lens rack), the examiner neutralizes the motion in 1) Uses a card with aperture at the center placed at 40 each meridian. It is done quickly so as to disturbing centimeters, while the examiner starts at 50 accommodation, response or avoid interfering with centimeters. binocular alignment of the eyes. 2) The examiner then moves forward or backward until 5) Record the lens power required to attain neutrality. neutrality is achieved. MOHINDRA’S NEAR RETINOSCOPY Example: It was introduced by Mohindra in 1949. (40 centimeters) +2.50 - +1.50 (66 centimeters) = Its purpose is to determine the patient’s distance +1.00D neutral refractive error while using the light of the retinoscope as the fixation target. According to Nott, the normal lag of While this method may be used for adults, it is accommodation is +0.50D. particularly useful for infants and toddlers. It is also If it is greater than +0.50D, there is either useful for people who have a hard time maintaining ○ accommodative insufficiency distance fixation. ○ under corrected hyperopia ○ presbyopia Set-Up ○ insufficient negative fusional vergence (NFV) Examiner is at 50 centimeters. Lead of Accommodation is less than +0.50D, it is Room Illumination is dim or dark and unexamined due to eyes will be occluded. ○ excessive accommodation ○ insufficient positive fusional reserve (PFV) Procedure ○ ciliary spasm 1) Occlude OS and examine OD. MEM RETINOSCOPY 2) If you are examining an infant, the infant will tend to fixate the light. If this does not occur, stimulate his MEM means Monocular Estimation Method. attention by making sounds (ringing bell, animal It was introduced by Bieber in 1974. sounds, coos or babble sounds). It objectively measures the accommodative 3) Scan and identify the principal meridians. response to near working distance. 4) Using the lens rack, identify the power which It differs from other methods in the fixation target neutralizes each meridian. because the target is placed at the patient’s 5) Calculate your gross retinoscopy finding in minus customary reading distance rather than the arbitrary cylinder form. distance such as 20 inches or 50 centimeters. 6) Add a -1.25D (constant) to the spherical component of your findings. CHROME RETINOSCOPY It was introduced by Bobier and Sivak in 1980. BELL RETINOSCOPY It was introduced by Apell in 1975. Procedure It measures the linear magnitude of the 1) Carried out in the usual way except that the light accommodation lag using a mobile target. entering the examiner’s eye is limited to a specific Originally done by dangling a small bell in front of band of wavelengths by placing an appropriate filter the examiner’s forehead but instead a 1⁄2 inch between the retinoscope and the examiner. chrome steel ball attached to a thin metal rod was used rather than a bell. RADICAL RETINOSCOPY It is performed when retinoscopic reflex is so faint Procedure and indistinct (maybe due to small pupils, cataract 1) The examiner is at 20 inches from the patient (with or other opacity of the media and keratoconus) that habitual glasses for near). the static retinoscopy is not possible at the usual 2) The examiner will hold the retinoscope with one working distance of 50 cm and 20 in. hand and the ball is suspended on its handle at eye The working distance may be as close as 20 cm or level with the other hand. 10 inches but the examiner must be careful. 3) The patient will be asked to look at his reflection in The equivalent WDL is subtracted from the lens the ball. power in the phoropter or refractor. 7  OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 FAQs Auxiliary Lens Knob (Aperture Control) How to test for accommodative insufficiency? The Aperture Control determines what the patient Lag can be measured several different ways including looks through when behind the phoropter. binocular cross-cylinders and near point retinoscopy, It consists of: such as the Monocular Estimated Method (MEM). A Open (O) – Is an aperture that contains the measurement of lag equal to or greater than +1.00 can lenses. be expected in patients with accommodative Blank (BL) or Occluded (OC) – Completely insufficiency or infacility. occludes or prevents the eye from seeing a target. MODULE 7: SUBJECTIVE REFRACTION AT FAR Retinoscopy Lens Aperture (RL) – Is a +1.50 or +2.00D spherical lenses in the aperture in addition to the lenses. This can be used to relax Subjective Refraction the unexamined eye during retinoscopy. Jackson Cross Cylinder (JCC) – Contains both +0.50 and -0.50 diopters. The purpose of Subjective Refraction is to Pinholes (PH) – Is used to determine if the determine, by subjective means, the combination of refractive error is correctable or will be improved spherical and cylindrical lenses necessary to through lenses or not. artificially place the far point of each of the patient’s Red Lens (RL) eyes at infinity. Maddox Rod (RMH or WMH) It is a combination of lenses which provide the best Polaroid (P) possible visual acuity with accommodation +/- 0.12 D relaxed. Horizontal Prism (10^I) Vertical Prism (6^U) Phoropter Ancillary Units The Ancillary Units have 2 or 3 ancillary units that The Phoropter is a complex lens holder designed can rotate in front of the eyehole when desired. to allow the examiner to change lenses efficiently Jackson Cross Cylinders Unit (JCCs) – JCC and easily. is marked with red dots or lines to indicate their It is consists of 4 Groups of Control: minus axis and white marks to indicate their Lens Control plus cylinder axis. The handles are positioned Auxiliary Lens Knob or Aperture Control 45 degrees away from the cylinder axes. Ancillary Units Rotary Prism – It has an indicator for the Adjustments direction of the prism base and a scale to indicate their net prism power. Lens Control Maddox Rod – It has grooves (red or white). It The heart of the phoropter. is used for phoria testing. It is divided into 2: Spherical Lens Control and Minus Plano-Cylinder Control. Adjustments This consists of: I. Spherical Lens Control PD Knob (Pupillary Distance) Has a total range of +20 diopters to -20 diopters. It Leveling Knob with Spirit Level consists of: Vertex Distance Control Weak Sphere Dial is a large wheel at each side Pantoscopic Tilt Control of the phoropter. Strong Sphere Control allows 3.00D or 4.00D changes in sphere. Step-by-step Procedure for Subjective Refraction Sphere Power Scale shows the net spherical (For Distance by using Phoropter) power. When rotated downwards, you add plus sphere. When rotated upwards, you add Monocular Subjective Refraction minus (or take away plus). 1) Sphere Used to Fog II. Minus Plano-Cylinder Control 2) Tentative Diagnosis It consists of: 3) Determination of Cylinder Under Fog Cylinder Power Knob rotates the cylindrical 4) Elimination of Fog lenses. 5) Confirmation of Cylinder Axis Under Slightly Cylinder Axis Knob rotates the cylindrical axis. Illuminated Accommodation Cylinder Axis Indicator displays the axis of the 6) Confirmation of Cylinder Power Under Slightly minus cylinder by the position of an arrow on a Illuminated Fog standard ophthalmic protractor. 7) Duochrome Test for Spherical Refinement Cylinder Axis Reference Scale is a standard ophthalmic reference scale; it shows the Binocular Balance cylinder axis. 1) Prism Dissociation Cylinder Power Scale shows the cylinder power. When rotated clockwise, you add plus FAQs cylinder. When rotated counterclockwise, you How important is Subjective Refraction? take away plus. In the business side of Optometry, less time consumed per patient means more patients to check in a day. This is good but almost, not all, optical clinics focus on this. To make a difference in the competitive world of 8  OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Optometry, let the patient experience a quality, ✔ Compound Astigmatism clinical-centered eye examination. It is tried and proven, the good impression you leave on one patient will lead Case Examples: you to more regular patients – they will be your free, 1) Patient, 18 years old, male, came in the clinic with walking advertisement. the complaints of constant blurring of vision at far. You performed a Visual Acuity procedure and the smallest line that the patient can read was 20/50 MODULE 8: SPHERE USED TO FOG & TENTATIVE both eyes. You then performed Refraction (Occlude DIAGNOSIS unexamined eye). Steps: Monocular Subjective Refraction a) Check VA. If visual acuity is okay or the patient can read the 20/20 line easily and without straining, I. Sphere Used to Fog proceed to fogging by adding the strongest plus that Fogging is the most perfect non-cycloplegic control will slightly blur his best VA which is 20/20. But if the of accommodation. VA is not 20/20, correct the ametropia and fog. It is the strongest convex (plus) lens for hyperopes (may also apply to emmetropes) and NVA — 20/50 the weakest minus for myopes. +0.25sph — 20/50-3 (VA worsen by +) It is used to make sure accommodation is relaxed. -0.25sph — 20/40 It is done by placing enough plus power in front of -0.50sph — 20/30 the eye to ensure that the image formed by the -0.75sph — 20/25 eye’s optical system will be located in front of the -1.00sph — 20/20 (Amount of Ametropia & the Best VA) retina, making the eye artificially myopic. With the image in his position, any effort to Approximate Amount (AAmt.): -1.00sph accommodate will result in poorer vision. Tentative Diagnosis (TDx): Myopia Proper Fogging Lens (PFL): -0.25sph Material Used b) Add plus lens or weaker minus to blur 2 lines above Snellen’s Test Chart (Far) the best visual acuity of the patient. Astigmatic Chart (Far) *for determining astigmatism - next step 2) Patient, 25 years old female, came into the clinic Spherical Lenses with the complaints of headache and constant blurring of vision both far and near, but worst on Procedure near. 1) Occlude the left eye. 2) Correct the refractive error. Present the Snellen’s NVA — 20/30 chart and determine the strongest plus or weakest +0.25sph — 20/25 minus spherical lens that will enable the patient to +0.50sph — 20/20 maintain or obtain clarity of a smallest line or best +0.75sph — 20/25 visual acuity (VA). Tip: Use small increments if +1.00sph — 20/30 uncorrected visual acuity is good and larger +1.25sph — 20/40 amounts of increment if uncorrected VA is poor. 3) Fog by increasing plus until the vision becomes Ametropia Amount: +0.50sph definitely worse, one or two lines above his best VA. TDx: Hyperopia Record this as Step #1. PFL: +1.25sph 4) Correct. If with plus spherical lenses vision becomes worse, cautiously try minus spherical lenses. Locate FAQs the weakest minus that enables the patient to obtain Fogging is a non-invasive way to relax accommodation. his best VA (smallest line possible, but necessary When accommodation is not relaxed, the resulting 20/20; case to case basis) prescription may be too high or too low from the actual refractive error. Some headaches complained by the Note: A minus lens that merely makes the letter more patient are not merely because of high refractive errors black but does not add another line is an over but more on the accommodation. Relaxing the correction. Then decrease the minus until vision accommodation by giving lenses with enough plus becomes definitely worse 1 or 2 lines above his best VA. power will relieve headache, plus, educating the patient Record this Step #1 about the 20-20-20 rule will also help. II. Tentative Diagnosis Tentative diagnosis is done after correcting the MODULE 9: DETERMINATION OF CYLINDER refractive error of the patient in Step #1. UNDER FOG & ELIMINATION OF FOG Whenever a plus lens is accepted and vision remains the same or improved, the case will be: III. Determination of Cylinder Under Fog ✔ Simple Hyperopia After determining the Proper Fogging Lens, ✔ Simple Hyperopic Astigmatism introduce to the patient the astigmatic chart. ✔ Compound Hyperopic Astigmatism This step will determine if the patient is astigmatic or ✔ Mixed Astigmatism not. When a minus lens is accepted and vision improved and the final prescription will contain a Types of Astigmatic Charts minus element, the case will be: Fixed Clock Or Sunburst Dial ✔ Simple Myopia ✔ Simple Myopic Astigmatism 9 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Clock Dial - Consists of 12 radiations at Tentative Diagnosis = 11.25° intervals of 30 degrees. Each radiation usually consists of 3 separate lines. Procedure (continuation) Sunburst Dial - Single spoke at 10 degrees 3) Add a minus cylinder with the tentative axis above interval until the patient will report that all meridians are now Fan Chart - Has 16 radiations at 22.5 degrees equally blurred. each 4) Record as Tentative Rx (Prescription) for Step #4. Arrowheads Dials Example: ○ A rotatable cross contains an arrowhead-like PFL: +1.25sph figure at the end or adjacent to one of the lines Tentative Axis: 45° of the cross Minus Cylinder: -0.75sph cyl Lebensohn’s Chart Tentative Rx: +1.25sph = -0.75sph cyl x 45 Raubitschek Chart Rotating T IV. Elimination of Fog Set-Up Set-Up Test Distance (TD): 20 ft. or best VA Test Distance (TD): 20ft Test Target (TT): Astigmatic Chart Test Target (TT): Best VA or 20/20 Control Lens (CL): PFL Control Lens (CL): #3 Finding Procedure Instruction to Patient 1) Instruct the patient to look at the astigmatic chart Please report if the letters in the 20/20 line or best and ask the patient to report if the lines are equally VA are clear. blurred. If the patient reports equally blurred lines, it Procedure indicates free from astigmatism (or no astigmatism). 1) Slowly reduce the fog until the patient attains the If the patient reports not equally blurred lines, it best VA. The strongest plus and weakest minus that indicates presence of astigmatism. gives the best VA is considered the best sphere. 2) Record as Tentative Rx for #4. 2) If the patient reports that some lines are different from the rest of the lines that are blurred, ask the Example: patient which lines and ask him if the lines are PFL: +1.25sph darkest or blackest. Sphere: +0.50sph 20/20 For Clock Dial, get the axis of the cylinder by Fog Eliminated: 0.75sph multiplying the smallest value to 30°. FAQs Examples: When the patient reports more than 3 darker or blurred Clock Dial lines, try to add one click fog lens. Repeat the 1) Patient reports the line 2 and 8 (clock instructions if necessary and ensure the patient is position/pattern) is darkest cooperating. Line 2 and 8 Axis = 2 x 30° MODULE 10: CONFIRMATION OF CYLINDER AXIS Tentative Axis = 60° AND AMOUNT Set the phoropter, specifically the cylinder axis knob to 60°. V. Confirmation of Cylinder Axis Under Slightly 2) Patient reports blurriest line is 3 and 9 Stimulated Accommodation Note: Same procedure with the darkest but you will add or subtract 90°. Set-Up Line 3 and 9 Test Distance: 20ft Axis = 3 x 30° Test Target: Best VA = 90 + 90° CL: Tentative Axis #4 Tentative Axis = 180° JCC Handle at the Tentative Axis If the product is 90° and below, add 90° and if the Rotating Method product is above 90°, subtract 90°. A. Jackson-Cross Cylinder (JCC) Fan Chart Procedure 1) Patient reports line 2 and 8 is darkest 1) Let the patient fixate at the letters one line above Line 2 and 8 the best VA obtained so far in monocular subjective Axis = 2 x 22.5 refraction. Tentative Axis = 45° 2) Patient reports that the line 4 and 10 and 5 and 11 are the blurriest Line 4 and 10 Line 5 and 11 Average = 4 + 5 = 9 ÷ 2 = 4.5 2) As shown in the previous figure, place the JCC lens Axis = 4.5 x 22.5 before the eye such that its axes straddle at 45° = 101.25° - 90° 10  OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 angle in the axis of the correcting cylinder in the Set-Up phoropter. Test Distance: 20 ft 3) Instruct the patient that you will show him two views Test Target: Best VA of the line of the letters and will identify each view Control Lens: Tentative Rx #5 with a number. Tell him that both views may be Jackson Cross Cylinder blurry, but to tell you which view is sharper or less blurry. Further instruct the patient to try to ignore the Procedure differences in the shapes (orientation) of the letters when comparing the views. 1) Place the JCC lens red dot along the final axis. 4) Let the patient look at the letters and tell him, “(Name of Patient), this is view number 1...” 5) After 2 to 5 seconds, flip the JCC and say “(Name of Patient), this is view number 2. Which view has clearer letters?” if the views are equally blurry, the axis is set in the appropriate position. 2) The instructions are the same in the previous steps 6) If the views are not equally blurry or equally clear, 3, 4 & 5 in the confirmation of cylinder axis under move the axis of the phoropter cylinder first by 15° fog. toward the minus cylinder axis (towards the red dot). 3) Present the two views to the patient by flipping the If not equally clear or blur, move the axis again by JCC lens. 10° and eventually by 5°. Until you are on the axis If the patient prefers the view no. 1, increase the that gives a clearer view. power of the minus cylinder in the phoropter by Note: 0.25D If the Cylindrical Amount is: If the patient prefers the view no. 2, decrease Less than 1.00D – rotate 15° the power of the minus cylinder in the phoropter 1.00D to 2.00D – rotate 10° by 0.25D Greater than 2.00D – rotate 5° 4) Throughout the JCC power check (confirmation), 7) Shift the orientation of the JCC lens so that the maintain the spherical equivalent of the MPMVA handle remains aligned with the axis of the starting point. (more plus, less minus) phoropter cylinder. For each increase in the minus cylinder of 8) Repeat procedure 4 to 7 as long as you have to -0.50D (that the patient accepts), add +0.25D or keep adjusting the cylinder axis in the same decrease minus on the sphere power direction. For each decrease in the minus cylinder of Note: The greater the cylinder power, the greater -0.50D, add -0.25D to the sphere the need for precision in the axis. 5) End the JCC power confirmation when either of the 9) End the JCC axis check (confirmation) when either following 2 conditions are met: of the following two condition are met: a) Both views look the same to the patient a) Both views look the same as the patient reports b) The patient’s responses call for changes within b) The patient’s responses create a back and forth a narrow range of powers. In this event, select movement within a narrow range. In this event, the power closer to that found in habitual select an axis in the middle of the range. prescription. If habitual prescription is not available, select the lens minus cylinder power. B. Rotating Method Procedure Example: 1) Tentative Rx: +1.75sph = -1.00 cyl x 90 1) Using the cylinder axis scale, put the indicator on 1st Position - Place the red dot along the axis of the the tentative axis or axis of the correcting cylinder. correcting cylinder which is 90 2) Instruct the patient to fixate on the target report if the letters become blurred. 3) Rotate the indicator clockwise until the patient reports blurring (or possible distortion) of letters. Note the axis where you stopped and rotate back to your 1st position or to the axis where the patient can = +2.00 cyl x 180 = +0.50 cyl x 90 see the target clearly. Rotate again the indicator counterclockwise until the patient reports blurring Transpose: +2.00sph = -1.50 cyl x 90 and rotate back until the patient reports clearer Patient wants to be over-fogged and over corrected. target. Perform 2 to 3 trials. 2nd Position - Place the red dot 90 degrees from the axis of the correcting cylinder which is 180 Example: Tentative Axis: 90 = +1.50 cyl x 180 = +1.00 cyl x 90 1st Trial: 70 – Clockwise blur Transpose: +1.50sph = -0.50 cyl x 90 114 – Counterclockwise blur Patient wants to be under fogged and under Get Average: 184 ÷ 2 = 92 corrected Confirmed Axis: 92 Note: Borish describes a variation on the JCC technique VI. Confirmation of Cylinder Power Under Slightly in which the whole VA chart, from 20/50 to the 20/15 Stimulated Accommodation letters, rather than an isolated line of letters, is 11  OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 displayed. The patient is asked to report which view I. Vertical Prism Dissociation allows him to read down the chart. Upon reaching the Vertical Prism Dissociation is the most commonly conclusion of the JCC test for both axis and power, used method. perform the second monocular MPMVA. FAQs Set-Up These 2 steps will be tricky and essential in making Test Target: 20/20 line (Snellen’s Chart) sure the astigmatic amount and axis are correct. Some Test Distance: 20 feet patients will have symptoms and some will have none. Control Lens: Add fog of +0.50sph to both eyes and It is important to master this techniques or 3^BD (Base Down) on OD and 3^BU (Base Up) on procedures to avoid discomfort. Getting the correct OS prescription will relieve major symptoms of astigmatism, headache. Procedure 1) Set the control lens. The patient should be able to MODULE 11: DUOCHROME TEST AND see two lines of letters: 1 on top of the other. BINOCULAR BALANCING Note: The right eye (with BD) is seeing the upper target and the left eye (with BU) is seeing the lower target. VII. Initial Duochrome (Bichrome, Red-Green Test) Remember: Base Up – target will be seen at the bottom of Procedure lower part 1) Let the patient fixated at the letters/symbols in the Base Down – target will be seen on top red and green side of the chart 2) Ask the patient if both targets are equally blurred. If 2) Ask the patient if the letters or numbers inside the the patient reports that the targets are not equally two colored charts (boxes) are equal or one side is blurred, it means one image or target is clearer than sharper and clearer the other. The eye which sees the clearer target is 3) If the letters on the red side are clearer, add under fog, therefore, increasing plus or decreasing -0.25D (click up) and ask the patient again if the two minus until the patient reports equally blurred colored charts are already equal. If the letters on the targets. green side are clearer, add +0.25D (click down) Example: Patient reported that the upper target is and ask the patient again. If the patient reports that clearer than that of the bottom (lower) target. The both charts (boxes) are equally clear, then the eye which has the base down prism is the right eye. patient is effectively Emmetropic or is an Increase plus by 0.25sph on the right eye or accommodating hyperope. decrease minus (if myope) by 0.25sph. 3) Remove the fog or the +0.50sph placed at the start To eliminate the possibility of the latter: of the test (reduce plus or increase the minus). When the patient reports red and green are equal, Example: Tentative Rx is -1.25sph both eyes. You always add +0.25D and repeat. If the patient continues added +0.50sph, making the lenses in place to be to respond to equality of the letters, continue adding -0.75sph OU. The patient reported the upper target plus spheres until a red response is obtained. to be blurrier. You increased plus on the left eye making the lens in place to -0.25sph and the patient Consider the Following: reported equality of the targets. You removed the If the phoropter contains a tentative cylinder from +0.50sph added at the start of the test. New static retinoscopy or some other test, proceed with tentative Rx is -1.25sph OD and -0.75sph OS. the JCC test. Remember that a VA of 20/20 or 4) Record the findings. sharp, clear vision may not be possible at this point in refraction, since the cylindrical part of the General Comments on Binocular Balancing prescription has not yet been refined. There is no point in attempting binocular balancing if If the patient has a clear VA of 20/20 or better with the patient has no binocular vision such as patients spherical lenses and if you are refracting the right with strabismus, deep amblyopia and patients with eye, proceed to the monocular refraction of the left one eye only. eye. If the patient has a clear VA of 20/20 with Always ensure sufficient fog is introduced. spherical lenses, proceed to binocular balance. FAQs Binocular Subjective Refraction There is no point in attempting binocular balancing if the patient has no binocular vision such as patients with strabismus, deep amblyopia and patients with one eye Purpose only. Always ensure sufficient fog is introduced. An The purpose of Binocular Subjective Refraction is accurate prescription will be given. not to balance the visual acuity but to balance the state of accommodation of the two eyes. MODULE 12: PRESBYOPIA AND SUBJECTIVE The procedures used to balance the state of the two REFRACTION AT NEAR eyes are called equalization tests or binocular balancing tests. Determining the Near Addition in a Presbyopic 5 Principal Methods Patient 1) Successive Alternate Occlusion 2) Vertical Prism Dissociation 3) Polaroid Techniques (Vectograph) Presbyopia is not considered as an ametropic condition 4) Blurring Techniques (Humphriss Immediate but rather a physiological effect caused by a loss of Contrast) resiliency of the crystalline lens. 5) Septum Techniques (Turville’s Infinity Balance) 12 OPT 015: Clinical Refraction Module 1 - 13 Doctor of Optometry │ Third Year - First Semester │ Academic Year 2023 - 2024 Common Symptoms: 2) Introduce plus lenses simultaneously to both eyes Recession of near point until that line is clear (increase plus or increase Vision at accustomed near point becomes blur or is minus) only clear with excessive effort 3) The lens in the phoropter is the TOTAL NEAR so Symptoms of Hyperopia you have to deduct the far prescription Constricted pupils upon dilatation in poor illumination, near vision blurs Example: Far Prescription: +0.50sph OU Lens which makes vision clear at near is +2.00sph OU Presbyopia (total near) Presbyopia is a condition whereby the amplitude of +0.50sph far RX accommodation is diminished with increase in age. - +2.00sph Total near It is defined as a condition when the amplitude of accommodation is diminished to the point where Add is +1.50sph (lenses added over and above the far clear or comfortable vision at the near point is not prescription) achievable. Commonly accepted age is 45 years old, but may Recording: +0.50sph ADD 1.50 OU appear as early as 40 years old as 48 years old or 50 years old. ADD BASED ON AGE The patient accustomed to greater working distance AGE ADD (WD) either to working condition or long arms, will 40-42 1.00 D not manifest the need for add power. 43-44 1.25 D The practical correction for presbyopia consists of 45-46 1.50 D the application of a plus lens beyond the lens power 47-48 1.75 D used for correction of the refractive error (far 49-50 2.00 D prescription). 51-52 2.25 D 53-55 2.50 D Reading Correction or Reading Add 56-58 2.75 D 59-60 3.00 D The difference between the power of the lens correcting the refractive error (known as Distance FAQs Correction) and the total amount needed for seeing Can we still base the reading add with the patient’s clearly at near. age? Yes, but because of the rising technology (computers and gadgets) and high demand for near work, Total Near presbyopia occurs earlier and higher than the expected age. The total power (far prescription and add) needed to see clearly at near. MODULE 13: CASE STUDY ANALYSIS Example: Far Prescription: +0.50sph OU SOAP: Subjective, Objective, Assessment and Plan Total Near: +1.50sph OU Add: +1.00sph OU In this last lesson of our class, you will study all the data gathered in Objective and Subjective Techniques Used: Refraction. 1) Plus Build-Up Based on the cases history and refraction results, 2) Add based on the Age you assess your patient, have a definite refractive 3) Fused Cross-Cylinder diagnosis and your possible plan or management 4) Proportion of Amplitude for the patient. 5) Dynamic Retinoscopy Reminder, you are still not allowed to dispense or 6) NRA/PRA Balance (Negative Relative prescribe any optical devices at this level. Accommodation/Positive Relative Accommodation) Recall all our lessons and procedures and get 7) Near Duchrome started. FAQs Plus Build-Up Do you need to explain to the patient the procedures you will be doing? This technique is the most commonly used. The answer is yes. In the Code of Ethics, the patient has the right to know the procedures to be done to him Set-Up or her. By doing this you are eliminating any doubts or fears of the patient. Educating and informing the patient Test Target: 0.62M Type of #28 of the reading card what to do and what to expect during the procedure will Test Distance: 13 inches to 16 inches give good patient compliance and eventually good, Control Lens: Far Correction accurate results. Another ways to get good and accurate results are good questioning (more Procedure (Phoropter Method) open-ended questions than close-ended) and complete, 1) Let the patient read the 0.62M type of #28 line in the proper instructions. reading card 13