PPO2 EX1 PDF - Primary Care Review Exam

Correal scars ? whaI can affect carneal clarance Cataract vitreous opacity humor chamber citreous humor aqueous , Correal , in ant , , , edema,vascular apacity, vitrious henornages , deposits Primary Care Review Exam #1 FRSSO Retinoscopy PowerPoint Synonyms of retinoscopy: Skiascopy, Skiametry, Umbrascopy, Pupilloscopy, Retinoskiascopy Skia: Derived from Greek meaning shadows from internal structures en ex yochealsokraorefractiveerror b Definitions: tid Refract: To change the direction of a ray of light when it passes from one medium into another of diﬀerent optical density. refrac pt no Objective with inpute lens put of ↳You front change ofrays in to Retinoscopy: method of determining error of refraction by illuminating the retina and observing the rays of light emerging eye from the eye. Keratonometer ,retinoscopy - Determining the nature and degree of the eye’s refractive errors and its correction with lenses. direction Refractometer: optical instrument to determine in an objective manner the refractive state of the eye (autorefractiondepends on refractive indexes). Refractor: instrument designed for refraction and phorometry, equipped with spheres and cylinders, prisms, and other accessories for refraction and binocular vision testing. -tictateevalrsiueate with phonepter Phorometry: used to test oculomotor functiontypically - Vergences, phorias ↳ deviations,fusions stem Corred closeda en en el andgo con ht a - Can be performed behind refractor or trial frame in thelig enter Retinoscopy: During retinoscopy, the retina acts as the primary reflector of the light that has traveled through the eye must show everything clea structures with diﬀerent refractive indexes. A reliableretinoscopy cAH back , - Greatest index of refraction is the cornea (needs to be clear). 1 376 mostime an Retina Layers: The incident light rays that strike the outer limiting membrane (OLM), are transmitted to the photosensitive pigments in the outer segments of photoreceptors by a waveguide mechanism. orange to red reflexx if we see anything deviating, its abnormal o The light that returns from the RPE and choroid is the result of competition between light absorption and backscatter. o Because of this, the fundus reflex is of red/orange color during retinoscopy or photorefraction. The RPE and choroid contain important light absorbers - Melanin: Highest concentration in RPE ↳ red color Hemoglobin: higher concentration in choriocapillaris for sinp ~ cularalth Xanthophyll: yellow pigment which absorbs blue light (Lutein and zeaxanthin are responsible for macular color) Fundus Reflex-Light reflected from the fundus has two components: Yet Lthin , Diﬀuse (backscatter): Result of light scattered due to micro and macroscopic particle reflections. Great portion is blocked by and light sensitivity do a cyclopegic agentthis can parale ciliarymuscle,dilate pupil cause blurryvision ↳ when. As en the pupil After you everywhere because pupil will not block it off tobe thatbackscated is igg Directed: the result of light that has been reflected from the retina/pigmented epithelium and is waveguided by the retina Retinoscopy Types/Modalities at 00 , Relax accommodation set distance at aset target indicating or stimulating Static Retinoscopy: the determination of ametropic correction during fixation at a set distance with accommodation relaxed. - Streak Retinoscopy: uses a streak of light, converging or diverging rays. Mostly used modality. Spot Retinoscopy: uses a spot of light, with a plane mirror. Good for children. Not good if you want to refine astigmatism from the start. Kidfixates on a static Radical Retinoscopy: used with small pupils or media opacities that make the reflex faint and indistinct. Examiner will have to use a closer WD (20-10cm). Important to note new WD ↳ closer untilyousee something Hindra Mohindra: used for children. The patient fixates the light on the retinoscope, the WD is 50cm. When compensating the objects 200 WD, 1.25D is subtracted instead of 2.00D. Dynamic Retinosocopy: When retinoscopy is performed while the patient is fixating a target at near.useful for accommodative system e scope really fast while lookingat MEM or BELL3 looking at near target distant target 2 - Accommodation is in use Streak retinoscope: The one we always use ac Spot retinoscope: Very rare. It works the same, but you are not going to be able to define or identifiy astigmatism axis from the beginning. When looking at a spot, there is no axis aligning. Instrumentation well Refractor or phoropter Skioscopy bars Trial lenses and trial frames - sever Youca biggest very straigthtoward Simplest to use ↳ Minus cylinder from: -0.12DC to 6.00DC - Prisms: 1-15▵ - field of view ±0.12D to ±20.00D - , Occluders, pinholes, Maddox Rods, red and green lenses, neutral density (ND) filters, polarized lenses Trial Frame cuseful for lowvision patients Why trial lenses and frame? Trial lenses and frame: A 100 visual field cannot be appreciated but trial las yes! with phonopter Porque trial lenses and i frame mira - must - knowT 50cm 2D 2 ufragileismallelderte 34rold For children that cannot stand behind phoropter (also some elderly). Bedridden patients: patient’s home, assisted living homes, hospitals. Lenses are larger in diameter; examiner can observe better the eye movements Verify distance RX Verify near Rx Screenings Examiner at 50cm from the patient. Usually performed in children, have them sit in their parent’s lap if unable to keep in chair. Completely dark room o can te similar it - Mohindra’s Set up doneee if - ~ 0 o o ret Treective o Use loose lenses or sciascopy bars Retinoscope light intensity enough to observe the reflex, but the patient still feels comfortable Have the patient look at the light while scoping the meridians and neutralizing - Write down the optical cross Remove the 1.25D WD from the results to obtain Mohindra Retinoscpy Phoropters o Refractors or Phoropters are interchangeable terms - pros Autorefractor do not : Fast , youdo it haud to Autorefractor cons: en a ·childrenyou of accommodation Sphere and cylinder lenses recefines basein haseo Jackson cross cylinder for astigmatic axis and power - Risley rotating prisms (for phorias and vergences)↑ - , evaluation Near vision tests ubifocal accommodative Objective Retinoscopy: Refractive error is determined without the input of the patient. It requires a/an: Human operator with a retinoscope, automated refractor-several and photorefractor ↳ an estimate and then do subjective you get refraction Purposes: To determine the distance refractive status of the patient’s eyes. - overminus) Goal: locate the far point of the spherical eye or the two far-point planes of an astigmatic one. Lyou can who cannot It is an objective measurement Patients orchin Used as the starting point for subjective refraction · put face Know your working distance children who get think scared cuz they - Retinoscopy brings the patient’s far point to a location that is a predetermined distance from the patient, the · conen Pwith opacities itS NCT · working distance, in front of the eye, with the use of lenses. Retinoscopes The most widely used retinoscopes are the Copeland Keeler, Heine, and the Welch-Allen They consist of an optical head, a sleeve, and a battery handle Streak vs. Spot Retinoscopy Esky - Streak: more accurate-fast. Developed by Copeland. Spot: external light source., very fast, for estimation. Skiascopy bar has to be close to the eye or spectacle plane. Mostly put it at forehead. Don’t cover target, if not the patient will for accommodate(positive power but it will create a myopic shift) · Accommodation produces myopia good childrenSpot Retinoscopy: Optic are the same, except that cylinder axis and power determination more accurate with the streak method. For some, the brightness of the reflex is much better with the spot retinoscope.. Meridional axis control are not ↳ 900 tism Las e astigmaLiple me youvarious and , tutes with Irreg in ans con meridi ans 90 aova be meridi not war necessary and not present with spot retinoscopy. Will look at the center of a diverging light through the patient’s pupil. o no Not manufactured anymore e Retinoscopic Reflexes to determine the principal meridians Hishapps to to ht tietreligpupil reflet Sker pheromma whe The principal meridians correspond to the orientation of the streak that provide the thickest and the thinnest reflexes or the For brightest and dimmest reflexes. Spherical error: Same thickness reflex in all meridians. Astigmatic error: thickness varies in diﬀerent meridians: ~ - ametropias do from steps like high big go prevent false neutrality - 3 to-6 to Break phenomenon, Thickness phenomenon, Skew phenomenon Astigmatic Reflex Skew phenomena is used more to refine the axis of small cylinders (astigmatism) ives mas - When the streak is of the axis, the reflex and intercept move in diﬀerent directions (their motion is skewed) The reflex moves parallel to the intercept when the streak is on the axis Straddling: Used to confirm the axis. Perform with the estimated cylinder in place. Then the streak is turned 45 degrees oﬀ axis in both directions. Then the streak is turned 45 degrees oﬀ axis in both directions. o Results: if the axis is - ↳ if one is faster than the other is not Correct: widths are equal in both positions Incorrect: widths are not equal in positions Confusing Fundus Reflex 180 obliqueaxis or right tinoscope all o o aplegüerweae To envergadebatene e Possibilities are the patient is having: - i Number of separate optical areas existing and degree of ametropic refractive diﬀerences between these areas. o high vatusic streaks Motion will be confused, according to the: - con a Irregular astigmatism Distorted corneas: Example Keratoconus, PMD disso Monochromatic optical aberrations (especially coma and spherical aberration, which are the most common) The usual situation is encountered when spherical and coma aberrations coexist, and the refracting power of the eye is greater throughout the periphery than the center of the pupil. - Then the eye is relatively myopic in the periphery and becomes more myopic peripherally when the pupils dilates (dim or by pharmacological agents). o Center is thicker and has with motion and the periphery is thinner and has against motion (horizontal meridian being scoped). The is what happens with scissors motion. o Reflexcacodegi ancrohappeni s anfrgatis happus 2 ax ricknow Wit Go ut o Scissor motion: the retinoscopy reflex moves more quickly in the center than in the periphery of the pupil as neutrality is approached from less minus/more plus direction and appears to have a wider streak in the central area than in the periphery. is o what o o Neutrality is reached first in the center of the pupil and more minus is needed to neutralize the periphery. More common in very myopic eyes, light irises, younger adults When confused reflex is encountered: - Is best to neutralize the central portion and rely on bracketing to reduce the error in neutralization -Scissor reflex: Sometimes one half of the reflex goes with the other half goes against Scissor Motion: The retinoscopy reflex moves more quickly in the center than in the periphery of the pupil as neutrality is approached from less minus/more plus direction and appears to have a wider streak in the central area than in the periphery. -100 neutral before or periphery viceversa -1 (Accommodating or relaxing accome Neutrality is reached first in the center of the pupil and more minus is needed to neutralize the periphery. More common in very myopic eyes, light irises and young adults. When confused reflex is encountered is best to neutralize the central portion and rely on bracketing to reduce the error in neutralization. False Neutrality Can be created by focusing the incident beam on the entrance pupil. The beam is well focused on the iris, which is approximately in the same plane as the entrance pupil. - You will do this in slit lamp/biomicroscopy evaluation, for retro illumination technique. ↳ Sources of Error in Retinoscopy o o o Incorrect working distance Failure to remove the working distance Scoping oﬀ the patient’s visual axis - 4 Failure of the patient to fixate the distance target o Failure to obtain reversal o o accommodate alot cause to Many times, examiner is away from visual axis o happens childre they ↳ Looking at you will cause accommodation, making it a dynamic retinoscopy. Failure to locate the principal meridians Failure to recognize the scissors motion DO Interpupillary Distance 8 diffuses 8 o Is the distance from the center of one pupil to the center of the other pupil, in mm. o Necessary before ordering SRx and before performing retinoscopy o - is p From temporal limbus OD to nasal limbus OS or measured from center to center of pupils ↳ To measure Binocular PD - to evaluate for lens and youdoitonPUPOcon where you anly place PD anteristheact your youroptical Instrument: millimeter rule (PD ruler) Examiner and patient are at the same eye level, at 40cm (16 inches) Position the PD ruler at the nose bridge of the patient, tilted back, resting on the nose Hold the PD ruler between the thumb and forefinger and the other 3 fingers are used to rest in the subject’s head(temple) Procedure3 Si lo haces mal , elpt no podrá ver 1. Close your OD. Ask the patient to fixate at your OS. 3. Examiner closes OS, subject fixates at your OD 5. DO NOT MOVE THE PD RULER : Now examiner closes OD, opens OS and patient fixates to OS and check to make sure 2. Zero the PD ruler at the center OD pupil, or to OD temporal margin of pupil or OD temporal limbus - 4. Read the marking on the contralateral side Examiner reads oﬀ scale directly in line with OS pupil center, OS left nasal pupillary border or OS nasal limbus zero point is still correct need to be correceen Total (PD-OD lansas - ↳ Usapositio en en Highest number is distance PD, the lowest is near PD a Always record Distance/Near in mm (largest always first) prodonocat grLarge essivaer or des Using the corneal reflexes IPD o o para pt opción devi ations s · Measure from the center of the nose bridge to the corneal reflex ·. Also gives Monocular PD (method to be used of patients with strabismus or only having one eye). Phoropter o The first far line is neutralized with a sphere and the other one (second far line) with a cylindric lens (plano-cyl), added over the sphere, with its axis at the orientation of the retinoscopic bar/streak reflex (in the phoropter). o o o o Adjustment knobs: PD, leveling, VD, pantoscopic tilit Sphere controls Minus-plano cylinder control: power knob and axis knob Auxillary lens/aperture control: O, OC, R, -0.50, JCC,PH,RL (red lens), RMH/RMV 9red Maddox rod), P (polaroid), +0.12DS, H (10 I) and V (6 U) prism. o Ancillary units: Jackson Cross cyl unit, rotary prism unit Diﬀerent Phoropters: o o Optometrist use minus cylinder form, spectacle prescriptions (SRx) are done in minus cylinder form. You will find all phoropter in pre-clinic and clinic are minus cylinder, therefore using minus-cylinder form the axis is recorded according to the orientation of the streak and not the movement. o This is because you already neutralize with the cylinder at that axis. Set Up for Phoropter o o o o o Disinfect with alcohol the phoropter Remove corrective lenses Adjust height of the chair, so your eyes and patient eyes are at the same level Place the target of 20/200 or larger with R/G filter at distance o Instruct to keep both eyes open and if you block their view, let you know - Is - o not if will To fixate and help relax accommodation aut I, accommodate the Look at the big letter E (Red/Green part). Not at me. Tell me if I block the letter. Using DIM illumination a,8094501350 Procedure o Of Adjust IPD in phoropter, level phoropter, vertex distance (12mm) and check pantoscopic tilt o overheadal Fff Measure IPD (distance/near) ↓ a ↳ post refina Identify the principal meridians em Identify the meridian with the most WITH motion (thicker reflex). This is the most plus meridian. Neutralize this meridian first. o Add plus lenses (black numbers) to neutralize the with motion. o Add minus lenses (red numbers) to neutralize an against motion. 802 Dioptric wheel down Dioptric wheel up Retinoscopy in the Phoropter o Once you neutralized the most plus meridian, go 90° away and change the direction of the streak to 90° away and align the cylinder axis arrow in phoropter with the direction of the streak. o Now neutralize the other meridian - This time you should have against motion if the patient is astigmatic. If not, it was spherical and should have a - The axis of the cylinder lens should now be aligned with the streak of the retinoscope. neutral motion. ÉÉa.int o In the phoropter: - Neutralize this meridian by adding minus cylinder power in the phoropter. The axis must be aligned with the streak. o o When both meridians have been neutralized, the number indicates the GROSS retinoscopy. Remove the WD to your SPHERE ONLY. Now you have the NET retinoscopy. - o Take VA This is your objective retinoscopy using a phoropter. Stay close to the visual axis without obstructing the patient’s view - One of the most common errors in retinoscopy is eccentricity due to wrong examiner’s position must say o The patient should be instructed to tell the examiner if the view of the target is blocked. - Look at the letter E, red or green side. Tell me if I am blocking the E. fear e aut farther re o Place a lens ≥+1.50D to relax the accommodation - For NBEO you need to perform a 3-eye retinoscopy: OD-OS-OD For proficiency purposes DO NOT use the retino (R) lens o Hold retinoscope 50 or 67 cm from the patient’s eye. o The patient’s OD is scoped with the examiner’s OD and the patient’s OS is scoped with the examiner’s OS. - Working distance for 50cm is -2.00D and for 67cm is -1.50D. This allows the examiner to stay as close to the patient's visual axis as possible, however, the examiner should not obstruct the patient’s view of the target. o Alternatively, in the phoropter, spherical lenses can be used to neutralize both principal meridians, like using loose lenses or skiaoscopy bars. - o Ex: useful when cyl is higher than 6DC ↳ Need to use optical cross ese shiascopy ifhigher or Plus (+) cylinder form - Rather than overplus the against motion (as in (-) cyl form), you will “overminus” the tested eye, so “with” motion will be achieved. Transpositions Spherical (+) power is then added at the spectacle plane until neutrality is obtained in the least plus meridian. Next, (+) cyl lenses are added until neutrality is obtained in the most plus meridian (using phoropter) Transposition negative to positive form - 3. 00-100X090 +3. = +2 00 H 00X180.. 00-1 00 = +2 00.. + 1 00 -1 00 converts to.. Recording fensologue o Objective Retinoscopy: Net Ret 090+090-180 OD: +2.00-1.00x060. 20/30 NIPH OS -3.00-3.00x120 20/20 o Eaency o Record the objective retinoscopy and VA of OD and OS - Do PH if 20/20 is not achieved Write Mohindra’s Retinoscopy/Dynamic, MEME, Bell, ect... if it was used. Mahindra’s Set Up: Examiner at 50cm from the patient. Usually performed in children, have them sit in their parent's lap if unable to keep in chair. Completely dark room. Use loose lenses or skiaoscopy bars. Retinoscope light intensity enough to observe the reflex, but the patient still feels comfortable. Have the patient look at the light while scoping the meridians and neutralizing. Write down the optical cross. Remove the 1.25D WD from the results to obtain Mohindra Retinoscopy figures ascremi effectinvge tinoscope as as usefulnot re Photorefraction ↳ Tooli than III e ↳ always top Photorefractions: Axial and paraxial techniques - Is a photographic technique that can measure the refractive error and e ↳willso accommodative response. - It is rapid and objective - A specific photographic pattern, which varies with the degree of eye defocus Only requires the patient to pay attention for short periods of time ↳ with respect to the plane of the camera. - Photorefractive methods are not as accurate as retinoscopy but can be very useful for testing infants and young children. myopic Paraxial Photorefraction: if the eyes are focusing light for normal vision, the image shows a smooth “full moon” of red over the retina. - If the eyes have abnormalities, the image changes. Myopia: reflects a bright half moon over the top of the pupil. Hyperopia: the light reflects as a brighter crescent moon in the bottom half of the eye. Photorefraction taking 3 photos o o o o 3 photos will be taken at an axial plane 1st: at 75cm: to determine pupil size 2nd: at 50cm 3rd: at 150cm 2nd and 3rd photos are compared to see which pupil is larger. If pupil is larger at 150cm, then eye is hyperope. If larger at 50cm, then the eye is myope. myopia a Ekin e willsh as Prevalence aldinadence · adoles ants te s of myopia in Profesionatacione Prevalence of Refractive Error Refractive Errors (RE) have a prevalence of ~800 million to 2.3 billion - It varies with age, country, sex, ethnicity, race, occupation, environment and other. Visual environment is an important factor in eye development, but also there is a genetic component - May be inherited from one parent, but higher probability of inheritance if both parents - Genome-Wide Association Studies (GWAS) in adults have have identiﬁed 39 genetic loci associated with RE and myopia. Hypropia DiOerences in Prevalence and Progression of Myopia o The Selection-Relaxation theory o Poste, in 1962, evaluated the prevalence of myopia by society: o Hunting and gathering: lower myopia prevalence o Agriculture: some higher myopia prevalence than hunting societies o Industrialized: higher prevalence of myopia Racial and Ethnic Variations ishighmelanic o Vanuatu Melanesian children: extremely low myopia prevalence o Rios Negro, Amazon rainforest in Brazil Indigenous population: 1% of myopia prevalence se little contact to industrial Now: Younger Brazilian generations, higher education: higher prevalence o Asian children in Taiwan, Hong King and Singapore: very high prevalence of myopia. Increases from 7% at 7 y/o to 60% at 12 y/o o University students in England: 40% prevalence o Medical students in Hong Kong: 95% are myopes o Fact: higher myopia prevalence among medicine, law, accounting, engineering and optometry students! Optometry students have a myopia prevalence of 85% ifitoshrink Environmental Inﬂuences sea o In US 2-4% of children entering school have clinically signiﬁcant hyperopia and astigmatism a Flagcant Re que - Hyperopia does not have a tendency to increase or progress during school years e mos se - This indicates more hereditary factors, minimizing the environment inﬂuences. a ↓ Latet o Myopia is present in 2% of children entering school in U.S. que mas - About 2% of children from ages 5-6 y/o, have -0.50DS or more of myopia y un - Its prevalence increases markedly during school years, having a tendency to progress rapidly for a period or years. (That suggest possibility of environmental inﬂuences.) · hypeopic emstrapeyou born an are weborn out opict mi a watch aborneve marbe your Lo deuebated If your if mopicnot Lincel& didwell babies increases hypropia compensa conacomodaci ón cuando hyperopia Myopia at birth and early childhood (related to age) o Emmetropization occurs rapidly during the ﬁrst year At birth there is a wide range of refractive error prevalence - Eyes that are completely developed at birth tend to be emmetropic or hyperopic - Eyes that do not completely develop at birth tend to be myopic By the end of the 1st year, few children are found to be myopic o The myopia found in low birth weight (premature babies) is due to eye underdevelopment, not axial elongation - Having steep corneas and relatively spherical, underdeveloped, lens, thus having more power G Congenital vs Acquired Myopia o Congenital myopia is present at birth or at a very early age, persisting through life - This is not necessarily hereditary. Ex: Premature EverhoredeP o Acquired myopia you hac - Approximately 1/3 of the population in industrialized society will become myopic after several years of schooling or during adult years still o Factors that inﬂuence myopia development: - Children with 1 myopic parent have more than 2x the risk to develop myopia - Children who spend an additional hour per week outdoors signiﬁcantly lowered their odds of developing myopia School Years o It has long been known that children who entered school while being emmetropic become myopic during the school years - Myopia tends to progress o This increases in a linear form from 2% at age 6 to 20% at age 20. The Early Adult Years o Myopia reaches a peak of about 30% prevalence between the ages of 20 to 40 years though Lasch4 Hacenotengs 20 40 Peakolo poracissaile Crigeadidenhole dar e · mpreasbyopesreceac ommodation Correa se d go en e o After 40 y/o there is a slight decrease in the percent of myopia due to the tendency of some low myopes to “loose” the myopia, rejoining the emmetropic group e Myopia in the Later Adult Years o Increase from 6.7% at 47-49 y/o to 15.3% beyond 75 y/o (Hirsch 1958) - Hirsch attributed this to nuclear sclerosis - Used a criteria of -1.13D or more of myopia - US Department of Health, Education and Welfare found double the prevalence (30%), using a 0.50D or more criteria dractswa cat UWSO and CCLR, Waterloo, Canada & o University of Waterloo’s School of Optometry and Vision Science st th study: myopia in children increases drastically from 1 grade to 8 grade - 1/3 cases were undiagnosed and uncorrected o History indicated that myopia used to increase by ages 12 or 13 - Study: more often in kids 6 or 7 y/o (Dr. Mike Yang, Centre for Contact Lens Research (CCLR), Waterloo - “Deteriorating at a much younger age” o Myopia typically worsens until the age of 21 - Study: an earlier onset age and may experience a much greater decline of eyesight over their lifetime compared to previous generations Classiﬁcation of Myopia o Myopia classiﬁcation based on observed or assumed etiological factors: Donders (1864): by prolonged close work 1. Stationary Myopia ↳ How it stays , stop 2. Temporarily progressive myopia ↳ Develops,progress never , o o o o o stops 3. Permanently progressive myopia ↳ keeps progress Steiger (1913): based on biological variability will get - Genetically determined ↳ a how much myopia we - Refractive error depends on the association between corneal refractive power and axial length Duke-Elder (1949): physiological vs. degenerative - Physiological myopia/Simple myopia: from normal biological variability appearing between age 5 and puberty - Degenerative myopia: rare, frequently leading to visual disability, even blindness Sorsby (1957): myopia and hyperopia in 2 broad categories: - Plano to +/- 4.00D - Greater than +/- 4.00D: Most possible the axial length is beyond the range found in an emmetropic eye Goldschmidt (1968) Denmark study - Low myopia is most common genetically determined, rarely exceeding 6-9D - Late myopia, developing after the cessation of bodily growth and related to excessive close work - High myopia excessive degrees. Causing severe reduced vision and degenerative changes Curtin (1985) classiﬁcation based on the etiology, degree of myopia and time of onset 1. Physiological myopia (simple myopia) due to the correlation between the axial length and the refracting power of the eye 2. Intermediate myopia by expansion of the posterior segment of the globe (medium or moderate myopia) 3. Pathological myopia considered an ocular disease in which several complications are · associated with the elongation of the eye Grosvenor (1987): Classiﬁcation based on age of onset and age-related prevalence Makes no assumptions about the etiology of the various categories of myopia 1. Congenital myopia: persists throughout infancy and is present when entering school. 2% prevalence. 2. Youth-onset myopia: onset about 6 y/o through teenage years. Prevalence is 2% at age 6 to about 20% at age 20. Many are low myopes that will become emmetropes or hyperopes in later years. 3. Early Adult-onset myopia: onset during the period of 20-40 y/o with a prevalence of 30%. Many will have small amounts of myopia and may become emmetropes or hyperopes later in life. 4. Late adult-onset myopia: onset beyond the age of 40 with prevalence increasing in later years, major cause is nuclear cataracts. Older adults who have +2.00D gradually become myopic due to nucleus changes. associatesen o 40 levels signific esc up Progression of myopia in children o Goss and Winkler (1983) found that most cases of myopia tend to increase in a linear manner into the middle or late teen years, then levels oO Found that mean age of cessation was 16 y/o for males and 15 y/o for females with a standard deviation of 2 years o The earlier a child becomes myopic the more rapidly the condition tends to progress. strong String relationship between the progression of myopia and increase in axial length and in others also vitreous depth. opad e Myopia Control Studies: not o +1.00D bifocals show to progress slowly or not at all in cases of less than o 1.00D of myopia. o Summer months: the increase in myopia is insigniﬁcant compared to school months periods. o Atropine ↓ doses placebo o Multifocal SCL o Orthokeratology myopia control Progression of Myopia in young adults o Myopia tends to progress o 3 categories for adult patients 1. Adult stabilization: rapid increase during early adolescence, then stabilization in to adulthood s 2. Adult continuation: rapid increase in adolescent years, then slow progression during adult years. 3. Adult acceleration: rate of progression accelerated after adolescence. o Increase I power (steepening) of the anterior surface of the cornea is the responsible for young myopia progression o Presbyopia year: most hyperopic and emmetropic eyes undergo hyperopic shifts during presbyopic years. - Small or moderate myopes will observe a decrease in myopia. o Children who are highly myopic during teenage years tend to progress at a much higher rate. - If it is asymmetrical, the eye with higher myopia may develop amblyopia in that eye. What causes myopia? Etiological factors: o Multifactorial or polygenic: cannot be traced to a single gene or strictly environmental. (Identical twins have similar refractive error, Runs in family,As a result of excessive near work) o Donders (1864): caused by prolonged tension on the eyes during close work and elongation of the axes. o Sato (1957): ciliary spasm and lens- caused by accommodative spasm, followed by hypertrophy of ciliary muscle. o Accommodation, IOP, and axial elongation. (Strenstroms and Sorsby determine there was an increase in axial length) o Proposed - Prolonged near work causes an increase in IOP followed by expansion of the vitreous chamber Experiments with implanted radiosonde transducers have measured vitreous chamber pressure changes - Accommodation causes a blockage of the ﬂow of aqueous humor due to sphincter muscle pulling forward on the anterior vitreous - OP increase when ﬁxating an object at 20cm o AM: it has been found high IOP in myopic subjects in the morning o Temperature: high body temperature 41C ̊ to 45C ̊ can cause scleral stretch (animals) Von Alphen: ciliary body and the choroid form an elastic envelope that limits the stretch of the sclera, counteracting a part of the IOP. o Macula supplies information about the focus to the brain, that feeds information to EdingerWestphal nuclear (EWN) concerning the degree of stretch necessary to maintain emmetropia. If mechanism fail, there will be inadequate tonus of the ciliary- choroid envelope allowing the eye to stretch, causing myopia. High Myopia o High myopia is deﬁned as refractive error of at least -6.00D or an axial length ≥26.5mm. o Myopic eyes are at increased risk for occurrences of ocular morbidity in later years including: Chorioretinal degeneration, Retinal detachment, Glaucoma, Cataracts o Greene (1980): the total stress of the posterior sclera caused by IOP and oblique muscles, accounts for posterior staphyloma. o Corneal radius is also involved in myopia. In myopes older than 18 with myopia progression, there is also corneal steepening. effect = Happense -sa High CORON e aa location myops not allhigh ic Pathologic or degenerative myopia: High myopia with any posterior myopia-speciﬁc pathology from axial elongation. 1. Progressive and irreversible 2. AOects ~3% of the world population 3. Global prevalence is from 0.9-3.1% with regional variability 4. Prevalence of pathologic myopia-related visual impairment is: - From 0.1% to 0.5% in European studies - From 0.2% to 1.4% in Asian studies Pathologic Myopia Etiology: o Biomechanical forces related to axial elongation resulting in stretching of the ocular layers and progressive thinning of the retina, choroid and sclera. Risk factors: o Primary risk factor: greater axial length and age. Indicator o Additional risk factors: Female gender, Larger optic disc area, FOH of myopia Pathologic changes in myopic eyes Indicators of a posterior staphyloma: Optic nerve crescents, Myopic cupping (ONH), Peripapillary detachment, Disruption of the retinal pigment epithelium, Chorioretinal degeneration, Retinal detachment, Glaucoma, Cataracts, Ocular and systemic disease in highly myopic children EMartan's of staphylorea syndrome Anomalous Myopias In these the accommodation stimulus is insuOicient for the patient’s accommodative response slightly accommodating - Night myopia: presents in low visibility conditions due to the fact that there is not an adequate stimulus to accommodation. ↳ night driving Pupil dilation leads to spherical aberration - Empty ﬁeld myopia: in photopic conditions in which there is not suOicient detail in the central accommodate at accommodate so visual ﬁeld to provide stimulus of accommodation. (Pilots) Do not know where tocertain distance - Instrument myopia: accommodation is stimulated by instrument and response is not appropriate. (Microscopes) techsthat 3 & med ist biolog accomm c.ir. at a usloly stimulus Hyperopia work at glasses o Hyperopia prevalence during school years is 6% from age 6 to 15.Many can accommodate and overcome the low hyperopia until their amplitude of accommodation is lower and cannot compensate anymore. Usually goes undetected in screening tests. nopo Manifest Hyperopia see - Facultative: portion of the hyperopia that can be overcome 9compensated0 with g to 8 min accommodation latent 06 - Absolute: Part of the hyperopia that cannot be compensated with accommodation H 2 00 Ab3 + 00 Latent hyperopia: hypermetropia that reveals only under cyclopegia +2 Example: 5-year-old HF has an objective refraction of +3.00DS OD and OS. Subjective refraction is e +2.00DS OD and OS VA 20/20. Lastly cyclopegic refraction is +5.00DS OD and OS. le Excessive accommodative convergence: When you use excessive amounts of accommodation must be algo constantly used to obtain clear vision. This results in crossed in crossed eyes, esotropia. Even if esotropia does not occur, the eyestrain of prolonged near work in uncorrected hyperopia results in serious problems in children’s ability to read. Lobj-subt Lobj -cyclo fasultativa · cases.. Torait. When excessive amount of accommodation is required to compensate an uncorrected hyperopia, the visual system has 3 choices: 1. Let the letters be out of focus, impossible to read 2. One eye turns inward, reliving the eyestrain but causing double vision (diplopia). 3. Overconvergence: Single vision (SV) is maintained but with large amount of stress due to unconscious continuous overconvergence, avoiding double vision Indication for cyclopegic refraction o Children with constant or intermittent ET on 1st visit o Accommodative esotropias (eye inward) o Suspected or having latent hyperopia o Suspected pseudo-myopia o Uncooperative/non-communicative patients o Variable/inconsistent endpoints in subjective refraction o Children and young adults with asthenopia E CasoClinico I p and young patient with esophoria, accommodative insuOiciency , 8 o Children accommodative fatigue, accommodative inertia, spasm of accommodation 9 o All children younger than 3 y/o Hyperopia at 6 months: During the ﬁrst 6 months of life an eye turns inward. After that it is most likely to happen due to high hyperopia or less common, paralysis of extraocular muscle or nerve. In this case if not corrected the eye will suppress and become amblyopic. Hyperopia Progression: o Hyperopics in early adulthood tend to become more hyperopic and also the emmetropic patient, but the changes are very slow with the years. o Age related hyperopia can be due to gradual decrease in the refractive error of the crystalline lens or maybe small decrease in the axial length. Uncorrected hyperopia and reading problems o Uncorrected hyperopic children have problems adjusting to school. (Slow readers, Worst in performing visual perception skill tests) o Unfortunately school and pediatrician’s screenings are directed toward myopes. Better vision screenings are needed Hyperopia can usually be detected by clinical refraction, thus most of the time there is no VA complaint How to detect possible hyperopes o During screening, while taking VA at distance, if the child was able to read the 20/20 line: o Introduce a trial lens of +1.00D and ask the child to read again the 20/20 line o If they cannot read it with +1.00D: passed screening If they can read it with +1.00D: failed screening It is very possible that they are hyperopes (can read the letters without the lens because they use accommodation to compensate for uncorrected hyperopia) Hyperopia Facts o Several states are making it a law to have a comprehensive eye examination before preschool born o InfantSEE program from AOA for babies lombthing o Also as eyecare professionals we need to be aware of when to at every prescribe back if o Study by Atkinson, determined if +3.50 or more is not corrected, they are at risk of developing ma strabismus or amblyopia. The correction will not alter the emmetropization of the eye Critical when to prescribe Astigmatism Types of astigmatism: Compound Myopic, Simple Myopic, Mixed, Simple hyperopic, Compound hyperopic o Children tend to have WTR astigmatism: According to a USA study 28.4% of children between the ages of 5 and 17 have astigmatism o Elderly tend to have ATR astigmatism check childre orge & Alsoarat Studies: Northeastern Brazil: 34% of students were astigmatic Bangladesh: 32.4% of adults older than 30 years old had astigmatism en el Manual Keratometry you,, when Keratometry: - Evaluates the curvature, power and toricity of the cornea film suspect tear in ret - Assess the integrity of the cornea and tear surface - Helps speed up retinoscopy and subjective refraction Provides axis and power of astigmatism - Helps with keratoconus diagnosis by providing obvious signs Mire distortion, irregular form of mires - Provides proper assessment for CL evaluations Astigmatism - Anterior Corneal Astigmatism: measured by the keratometer - Refractive (total) Astigmatism: measured by retinoscopy and/or subjective refraction - Corneal and refractive astigmatism may not coincide due to: o Physiologic lenticular astigmatism (Usually ATR and varies with age) o ELectivity changes: ~ 25% increase in astigmatism going from the corneal plane to the spectacle plane o Corneal posterior surface curvature Basic components of a keratometer: Adjustable eyepiece, Adjustable chin rest and forehead support, Knob to raise and lower the instrument and align the patient's eye, Two power wheels to measure corneal power in each principal meridian, Axis scale of the 2 meridians, Mires (target) that are reﬂected in the cornea, Focus knob or joystick to focus mires on patient’s cornea Correa , ↳ Keratometer: The design of the keratometer provides a measurement of the size of the reﬂected image and leads to the determination of the radius of curvature of the anterior corneal surface. - Taking the refractive index of the cornea into account, the radius of curvature is converted to the dioptric power of the cornea, which is the number indicated on the side of the dial. - Keratometers can measure corneal curvature between 36.00D and 52.00D - Auxiliary lenses have to be added to measure anything above 52.00D or below 36.00D o Keratoconus, Cornea plana or LASIK myopic pts ↳ Congenital Keratometry Limitations: - Only measures a small region of the cornea (3-4mm zone) - Assumes the cornea is symmetric with a major and minor axis separated by 90 degrees - Ignores spherical aberrations - Is susceptible to focusing and misalignment errors - Mire distortion prevents accurate measurement of irregular corneas Keratometry Set Up: - Disinfect the instrument o Chin rest and forehead rest - Focus eyepiece o Reticule in focus o Incorrect focusing can produce signiﬁcant error - Adjust the patient - Turn on and unlock Procedure: - Align the barrel with the patient’s eye (lateral canthus with mark) until you see the reﬂection of the mires in the patient's cornea. - Ask the patient to look at their own eye - If you cannot ﬁnd the patient’s eye you can use a penlight to help guide you - Focus the mires and adjust the instrument - Focus the crosshair in the center of the lower hand circle - Using the focusing knob, bring the bottom circle into focus as a single image - Locate the principal meridians o Make the “plus” signs parallel by rotating the instrument and then overlap them with the horizontal meridian wheel o Align the “minus” signs with the vertical meridian wheel o Keep one hand on the focusing knob - Adjust and re-center as necessary during the procedure - Observe corneal integrity by observing the conditions of the mires (Patients with dry eyes will need to blink or use artiﬁcial tears before the procedure) - After evaluating OD proceed with OS - If irregular astigmatism is present the 2 principal meridians will not be 90 degrees apart. (In this case ﬁrst do the horizontal meridian, readjust the barrel and then do the vertical) 36 52 Recording - Record each eye separately - Flatter K’s/ Steeper K’s - 44.12@180/45.25@090 (Always record to 2 decimal points) - Also include the amount of corneal astigmatism in diopters with the axis o CC: -1.13x180 soval - Record the condition of the mires: (Clear or distorted) Shape - Can also include if astigmatism is ATR, WTR, OBL or irregular Astigmatism - Regular Astigmatism: principal meridians are perpendicular (90 degrees away) o With-the-rule (WTR): more power (greatest curvature) in the vertical meridian and horizontal meridian is ﬂatter. Ex:43.25@180/45.00@090 - Against-the-rule (ATR): more power (greatest curvature) in the horizontal meridian and vertical meridian is ﬂatter. Ex:42.50@115/44.87@025 - Oblique: principal meridians lie between 30-60 degrees and 120-150 degrees - Irregular Astigmatism: principal meridians are not perpendicular toeach other. o Produce distorted mires Troubleshooting - Unable to locate keratometric mires: instrument and/or patient are not aligned properly. - Mire clarity is transient: measure quickly after allowing the patient to blink. - Mire focus is transient: ensure the patient’s forehead is secure against the headrest. - Patient gaze is unsteady: ensure that fellow eye is occluded. - H&V mires cannot be measured concurrently: patient may have irregular astigmatism. - Only 1 plus sign is visible: patient’s eyelid is drooping, have them open wide. - Only 1 minus sign is visible: the occluder is in the way. Extended ranges - If the power in a meridian falls outside the power range of the keratometer, lenses can be used to extend the range. - Tape or hold loose lenses over the opening of the keratometer barrel and perform the measurement as described before. o +1.25D loose lens: to increase the diopter range o -1.00D loose lens: to decrease the diopter range - Then multiply the K reading by the corresponding correction factor. Increasing Range - Either you add +9.00D with the +1.25D lens to the K reading or -6.00D with the -1.00D lens to the K reading OR Multiply the K reading by the correction factor Increasing Range Examples - K’s are over 52.00D o Add a +1.25D lens in front of the barrel o New K drum reading is 49.00D o True K value: 49.00 x 1.166 = 57.13D or 49 + 9= 58.00D - K’s are less than 36.00D o Add a -1.00D lens in front of the barrel o New K drum reading is 38.00D o True K value: 38.00 x 0.8576= 32.59D or 38 – 6= 32.00D Expected - The 2 principal meridians are expected to be 90 degrees apart (If not, it is irregular astigmatism) - Average K readings are between 43.00 to 44.00 - Reminders for recording: o Eye: reading ﬂat@meridian/steep@meridian; quality of mires; corneal cylinder (cc) with axis o Diopters: 0.125 steps (each line in the dial) o Axis of the corneal astigmatism is from the ﬂattest meridian Recording Examples - Mires can be recorded as: Clear And Regular (MCAR), irregular and distorted, or egg shaped. o OD: 42.50@180/43.00@090 MCAR CC -0.50x180 o OS: 41.00@170/43.00@010 MCAR CC -2.00x170 o OD: 42.50@180/43.50@090 MCAR, 1.00D WTR o OS: 41.37@180/47.37@090 distorted mires, 6.00 AR o OD: 43.13@060/44.00@150 distorted; -0.87x060 o OS: 47.37@180/41.37@090 egg shaped mires; -6.00x180 ego 5441 4 Javal’s Rule - It is an empirical determination of the relationship between corneal astigmatism and refractive astigmatism. - Total refractive astigmatism = 1.25 (CC) ± 0.50 axis 090 o Add or subtract 0.50 cyl according to the axis § If CC axis is ATR astigmatism will be higher = subtract § If CC axis is WTR astigmatism will be lower = add Simpliﬁed Form of Javal’s Rule - By Grosvenor et al - Refractive astigmatism = (Keratometric astigmatism) –/+ 0.50x090 o Add or subtract 0.50 cyl according to the axis § If CC axis is ATR astigmatism will be higher = subtract § If CC axis is WTR astigmatism will be lower = add

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