Low Vision Assessment - OPT 032 PDF
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This document discusses low vision, including various aspects like peripheral field constriction, contrast sensitivity, and its impact on quality of life. It includes factors affecting contrast sensitivity and methods of measurement, along with the importance of a comprehensive vision assessment.
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OPT 032: LOW VISION possible. letter VA. ctivities Area lighting, glare a Low Spatial...
OPT 032: LOW VISION possible. letter VA. ctivities Area lighting, glare a Low Spatial vs High Spatial Frequencies management, high contrast cotomata may be recognised S architectural surrounds, subjectively using the Amsler conspicuous stair treads. charts. ERIPHERAL FIELD P ifficult travel and orientation in D edical management for M CONSTRICTION unfamiliar environments (no glaucoma, diabetes and threat detection). Night blindness consequential cataracts. Image . Entire periphery 1 with RP, even in children. enlargement onto the peripheral glaucomą, retinitis pigmentosa, retina may be unhelpful because diabetic retinopathy following umping into objects, glare B of field losses. Yellow and panretinal laser difficulties, slow light-dark orange 'blue-blocking' filters, photocoagulation adaptation. Putting things down glare management. Mobility and losing them. Hemianopsia training and other rehabilitation. causes slow reading, losing the Area lighting, glare . Sector defects 2 place in the text even if distance management, high contrast neurologic disease (stroke, brain is a single letter. VA is normal. architectural surrounds, tumors, tumors, chiasmal defects Watch for cognitive decline in conspicuous stair treads. etc) post detachment losses older patients. ehabilitation training to develop R umber of disability n adaptation strategies and new characteristics of these skills are available from low conditions are often vision clinics and blindness unpredictable agencies Low Contrast Threshold QUALITY OF LIFE isease Progression D Peripheralvisionloss→Lossofactivitiesandmobility→ Social isolation and depression High Contrast Threshold Foveal vision loss → Poor facerecognitionandDifficulty reading → Increased reliance on voice recognition → Social isolation and depression easurement Notations M 1. SnellenFraction:Expressedasd/Dwhered=testdistance HIGH AND LOW CONTRAST VISUAL ACUITY and D=distance at which letters subtend an angle of 5 minutes of arc. ontrast Sensitivity C 2. MAR (Minimum Angle of Resolution): Inverted Snellen ContrastSensitivityistheabilitytoperceiveslightchanges function expressed in minutes of an arc. inluminancebetweenregionswhicharenotseparatedby 3. LogMAR(LogarithmoftheMinimumAngleofResolution): definite borders and is just as important as the abilityto Logarithmic to base 10 of MAR perceive sharp outlines of relatively small objects. 4. Decimal Notation: Common in Europe, calculated by dividing the numerator by denominator PURPOSE OF IDENTIFYING THE CONTRAST SENSITIVITY HIGH CONTRAST DISTANCE VISUAL ACUITY CHARTS . 1 omprehensive Vision Assessment C 2. Real-world Visual Function igh contrast visual H 3. Early Detection of Eye Condition acuityreferstotheability 4. Treatment Monitoring of the eyes to discern 5. Safety Considerations fine details of objects 6. Quality Life Assessment when there is a 7. Customized Vision Correction significant difference in brightness (contrast) between the object and FACTORS AFFECTING CS its background. This is typically . 1 efractive Errors R measured under optimal 2. Age viewing conditions where the contrast is close to 100%, 3. Cataract such as black letters on a bright white background. 4. Glaucoma 5. Diabetic Retinopathy nellen Acuity Chart S 6. Optic Neuropathy The Snellen chart, while successful for screening 7. Pituitary Adenoma refractive errors, haslimitations,reducingitssensitivityin 8. Drugs theuppervisualacuityrange,whichiscrucialinlowvision 9. Toxic Chemicals assessments. Italsofailstoaddress"crowding"or"contourinteraction," easurement of CS M makingsingleletteridentificationeasierthanmultiple-letter 1. Averageamountoflightreflecteddependsonillumination presentations, and the legibility of letters varies greatly, of paper and darkness of ink especially in the higher acuity range. 2. Degree of blackness in relation to white background 3. The distance between the grating periods of cycles per eeler A Series Chart K degree of the visual angle designed by Charles Keeler 27 OPT 032: LOW VISION he A series charts, based on a logarithmic (constant T 5. N ote the smallest line of letters where the patient can ratio)scalingsystem,wereessentiallytheprecursorstoall correctly identify the majority of letters. currently available LogMAR charts. 6. Repeat for Each Eye They had 20 different series of letters, ranging from A1 7. Test the other eye following the same procedure. (6/6[LogMAR0.0]equivalent)toA20(1/60[LogMAR1.9] 8. Finally, test both eyes together for binocular vision. equivalent). Eachlinedifferedfromitsnearestneighbour,insize,bya ailey-Lovie Logmar Chart B factor of ×1.25. TheBailey–Loviechartuses a consistent logarithmic scale, with equal numbers ofequallylegiblelettersper line and uniform spacing based on letter size. A change of three lines represents a doubling or halving of letter size. Visual acuity is scored as 0.1 LogMAR per row and 0.02 LogMAR per letter correctlyidentified,adjusted for chart distance, as rocedures in Conducting the Test P LogMAR defines a visual 1. Set the chart at 1 meter or appropriate distance. angle, not letter size. 2. Ensure good lighting without glare. Simplifies calculating required magnification for reading 3. Seat the patient comfortably, facing the chart. specific text sizes, with LogMAR scores decreasing as 4. Ensure the patient wears distance correction if needed. acuity improves (inverse of decimal acuity). 5. Occlude one eye; start testing the other. 6. Point to the largest optotype and ask the patient to read. rocedure P 7. Gradually move to smaller optotypes as the patient 1. Position the chart at 6 meters (or 1 meter for near vision). succeeds. 2. Ensure adequate lighting and have the patient sit 8. Record the smallest line where they identify most comfortably at eye level. optotypes correctly. 3. Cover one eye. 9. Repeat for the other eye and then both eyes together. 4. Ask the patient to read letters, starting from the top line 10. Record visual acuity at the test distance (e.g., 6/60 at 1m). and moving down. 11. If no letters are seen, assess hand motion or light 5. Record 0.1 LogMAR for each correct line and -0.02 perception. LogMAR for each correct letter within a line. 12. Use results for diagnosis or management. 6. Repeat for Other Eye: 7. Test the other eye the same way. loan Distance Acuity Charts S 8. Calculate and record the total LogMAR score for each TheSloandistanceacuitychartuses eye. the metric "M" notation, tailored for visually impaired individuals, with aterloo Charts W linear scalingoflettersizes(e.g.,3M Similar to Bailey–Loviecharts,butlettersarearrangedin letters are three times larger than columns instead of rows for testing visual acuity. 1M). Testing Method: Patients read across the top line and Letterssubtend5minutesofarcat1 move vertically to determine exact acuity meter, with results recorded in Interactive Features: Includes surround bars to make Snellenformat(e.g.,0.2/3Mfora3M lettersatthestartandfinishofeachlineequallydifficultto letter read at 20 cm). read as those in the middle. Whilenotwidelyadoptedglobally,itis best known for near acuity erris LogMAR Chart F assessment and provides a The ETDRS chart, designed by standardizedapproachformeasuring Ferris and colleagues, uses Sloan visual performance. optotypes and is the most widely usedLogMARchartforvisualacuity rocedure P testing, typically used at a 4-meter 1. Place the chart at the appropriate test distance (e.g., 1 distance. meter for standard use). One chart is used for refraction, 2. Have thepatientweartheircorrectivelensesfordistance while the other two are for testing vision, if applicable. the optimal acuities oftherightand 3. Cover one eye while testing the other. left eyes, with results recorded in conventional format. 4. Ask the patient to readfromthetopofthechart,starting Acuity values are adjusted based on the distance tothe with the largest letter size (e.g., 3M). chart(e.g.,6m,3m,or1.5m),usingaconversionfactor to accurately calculate visual acuity. 28 OPT 032: LOW VISION rocedure P Regan Low Contrast Letter Charts 1. Set the Ferris LogMAR (ETDRS) chart at a 4-meter The Regan lowcontrast distance from the patient. letter charts follow LogMAR 2. Ask the patient to read from the top line, noting thelast principles with each line correct letter or line. containing eight equidistant 3. Calculate and record the visual acuity based on the letters, and contrast ratings smallest line read correctly, adjusting for any missed of 96%, 7%, and 4%. letters. TestDistance:Designed for use at a 3-meter testing ymbols Chart S distance. Symbol charts are designed for individuals with severe Illumination & Scoring: learning disabilities, including children, to assess visual Requiresuniformillumination function. at 100 cd/m² and uses a nonogram scoring system for Developed by Lea results. Hyvarinen, it includes LogMAR-based rocedure P alphanumeric and picture 1. Position the Reganlowcontrastletterchartatadistance symbol charts, as well as of 3 meters from the patient, ensuring that the chart is matching symbols and uniformly illuminated to approximately 100 cd/m². crowded symbol books. 2. Ask the patient to read the first line of letters with the Symbol matching is done highest contrast (96%) and proceed down the chart. similarly to the 3. As thepatientreadseachline,notethelastcorrectletter Sheridan–Gardner letter they identify. If they make a mistake, stop at the last matching cards or Kay correctly read letter. picture cards. 4. Repeat the process for each subsequent line with lower contrast(7%and4%).Ensurethatthepatientreadseach omputer-Generated Charts C line from left to right. Computer-generated charts 5. Recordthelowestline(contrastandsize)thepatientcan eliminatetargetmemorizationby read correctly, and use the nonogram scoring system to randomizing optotype document their visual acuity for each contrast level. sequences and allowing for 6. Test the other eye in the same manner, ensuring enhanced accuracy with consistent testing conditions and illumination. adjustable parameters like luminance, contrast, spacing, and exposure time. Previously limited by pixelation, current technology allows for high-quality shapes, with lines now scrollable to overcome vertical space constraints. An advanced system that incorporates these improvements and provides a more precise and customizable visual acuity testing experience. LOW CONTRAST VISUAL ACUITY CHARTS elli-Robson Low Contrast P Low contrast distance The Pelli–Robson low visual acuity measures a contrast letter chart consists person's ability to discern of letters of equal size, objects or letters at a grouped in threes, with distance when the contrast contrastdecreasingfrom89% between the target and the at the top left to 0.5% atthe background is reduced.Itis bottom right across seven oftenusedtoevaluatevision lines. in conditionswherecontrast The patient is asked to read sensitivity is impaired, such groups of three letters per as in patients with line, and the score is based glaucoma, cataracts, or retinal diseases. on the logarithm of the The test typically uses low contrast optotypes (letters or contrast sensitivity ofthelast symbols) with reduced contrast levels, making it more group with at least two letters read correctly. challenging than standard high-contrast visual acuity The chart is designed for use at 1 meter to assess testing. The results are recorded similarly to standard contrast sensitivity at the peak of the contrast sensitivity visual acuity but help assess howwellapersoncansee function, correlating well with daily activities likemobility, under conditions of reduced contrast, whichiscrucialfor face recognition, and reading. daily activities like driving or recognizing faces in low light. 29 OPT 032: LOW VISION rocedures P ecordtheThreshold:Stopwhenthechildcannolonger R 1. Set Up the Chart: Position the Pelli–Robson chart at a reliably identify the face or respond visually. Note the 1-meter distance from the patient. lowest contrast level at which the child can identify the 2. HavethePatientRead:Askthepatienttoreadeachgroup smiling face. of three letters, starting from the top left. Repeat for Confirmation (Optional): For consistency, 3. Record Results: Score the contrast sensitivity based on repeat the test at the same distance or a different the last group where at least two letters were read distance, if necessary. correctly. dge Detection Test E ailey-Lovie Low Contrast Chart B The Melbourne Edge Test (MET) Bailey–Loviechartsfeaturehighcontrast(blackletters)on uses a portable lightbox, a one side and low contrast (grey letters) on the other. transparent acetate chart with Thelowcontrastchartuses10%Michelson(18%Weber) circlesdividedbyluminanceedges, contrast for testing. and a response key card for edge The difference between high and low contrast acuities orientation tasks. helps measure the slope of the CSF in high spatial Observersidentifytheorientationof frequency ranges. edges (0°, 45°, 90°, or 135°) as contrastdecreaseswithsuccessive ymbols Contrast Chart S circles. Lea Test System: The Lea Test system includes low contrast rocedure P charts with symbols at contrast 1. Place the MET lightbox on a stable surface with the levels of 10%, 5%, 2.5%, and transparent acetate chartinserted.Ensureproperlighting 1.25%. conditions. Matching Symbols: The same 2. Showthepatientthecirclesonthechart,startingwiththe symbols used in high contrast highestcontrastedge.Askthemtoidentifytheorientation charts are utilized, allowing the of the edge (0°, 45°, 90°, or 135°). samesetofmatchingcardstobe 3. Gradually move to circles with lower contrast until the used for both children and individuals with learning patient can no longer correctly identify the edge disabilities. orientation. Note the lowest contrast level where Pediatric Contrast Sensitivity: Newer systems like orientation is correctly identified. Hyvärinen’sHidingHeidisetandBailey'sMrHappyFaces are designed to assess low contrastacuity,withcontrast inusoidal Gratings S levels down to 1.25% and 0.25% respectively. Sinusoidal gratings, used inprinted card formats, screen contrast rocedure P sensitivity but require 1. Set Up theChart:PlacetheappropriatelowcontrastLea computer-generated versions for chart (with symbols at the desired contrast level) at a comprehensive spatial frequency standard test distance, typically 3 meters for distance analysis. vision or 40 cm for near vision. The Arden Test uses plates where 2. Present Symbols: Ask the patient (usually a child or gratingcontrastincreasesdownthe individualwithalearningdisability)toidentifythesymbols, plate, and the patient identifies starting from the top row. Use the matching cards that when thegratingsfirstbecome correspond to the symbols on the chart. visible. 3. Measure Performance: Record the last row or set of The Vistech (VCTS) chart symbols the patient can correctly identify. Note the presents circular targets with contrastlevelofthesymbolsinthatrowtodeterminetheir gratings at five spatial contrast sensitivity. frequencies and nine contrast levels, requiring observers to iding Heidi Contrast Chart H identify grating orientations. Sit the patient (typically a child) at a comfortable viewing rocedures P distance, usually 40–50 cm. 1. Place the VCTS chart at 1 meter from the patient, Place the Hiding Heidi cards in ensuring appropriate lighting and clear visibility. frontofthechild,startingwiththe 2. Ask the patient to identify the orientation (vertical, highest contrast card. horizontal, or diagonal) of the gratings in each circular Present the Cards: Show each target,startingwiththehighestcontrastatthetopofeach card one at a time, starting with the highest contrast row. (100%)smilingHeidiface,andgraduallyprogresstolower 3. Note the lowest contrast level at which the patient can contrast levels (e.g., 10%, 5%, 2.5%, 1.25%). correctly identify the grating orientation for each spatial Observe Response: Ask the child to pointtoordescribe frequency (row). the face (e.g., "smiling" or "Heidi"). For non-verbal children, observe their visual behavior (e.g., eye movement, reaching, or gazing) to determine recognition. 30 OPT 032: LOW VISION TESTING STRATEGIES Key Differences In a low vision clinic, it is crucial to obtain accurateand Aspect Visual Function Functional Vision repeatable measurements of visual acuity and, where needed, low contrast acuity or contrastsensitivity.These Definition erformance of the visual system P ractical use of vision in daily P components activities measurements are essential for: Determining Low Vision Aids: The results of these tests inform the selection of appropriate low vision aids (like Assessment Method ontrolled tests measuring C specific visual capabilities eal-world tasks assessing R overall visual task performance magnifiers,telescopes,orelectronicdevices)thatwillbest assist the patient in their daily activities. RehabilitationStrategies:Thevisualassessmentprovides Focus Objective measures (acuity,contrast) ubjective experience S (efficiency, processing) guidanceonrehabilitationstrategiesfortasksthatrequire far or intermediate distance vision (e.g., reading, linical settings with standardized C veryday environment with varying E recognizing faces, navigating environments). Environment conditions condition StandardizedTestingEnvironment:Testingshouldoccurin consistent lighting and follow a clear procedure, as described in earlier chapters, to ensure accuracy. ear Acuity N Standardizing the testing environment helps reduce Often quoted when describing visual performance using potential errors in measurement. conventional Near Vision Charts. Patient Comfort and Time: It's essential thatpatientsare The measurement is not the near equivalent ofdistance given enough time to discriminate optotype details. acuity, irrespective of theutilizationsofSnellenChartsor Rushedtestsmayresultininaccurateresults.Additionally, LOGMAR Charts. positive feedback from the clinician can motivate the Distance acuity utilizes uppercase single optotypes patientandencourageoptimalperformance,makingthem At near, patients rely on higher cortical processes feel more confident and engaged in the process. Task of reading involved delivery to reflect meaning and context. PRACTICAL RELEVANCE Influencing Factors hen patients move from a high-contrast test (like the W Fluency Bailey–Lovie chart) to a low contrast equivalent (e.g., 10% Reading Speed contrast),thedifferenceoftendemonstratesadramaticimpact Comprehension ofcontrastlossonvision.Thisstarkcontrast(nopunintended) between high and low contrast helps patients better NEAR (READING) ACUITY CHARTS understand their visual impairmentsandwhycertainadaptive strategies (like better lighting, high-contrast materials, or magnification) may be necessary in their daily lives. aeger J Textisformulatedfromtypesof20 NEAR VISUAL ACUITY AND READING PERFORMANCE different sizes. (ASSESSMENT AND STRATEGIES) The size progression has never been standardized. Use highly variable words and isual Function V letter spacing. Referstotheimportanceoftheanatomicalcomponentsof the visual system, such as the eyes and the brain, in N Point System Charts detecting and processing visual stimuli. ach Npointisbasedonaprinter’sblocksizeof1/72ofaninch.Theactualletter E unctional Vision F Measurement size is about 1/107 of an inch. Howeffectivelyanindividualusestheirvisionineveryday he charts use Times Roman typeface. Lowercase letters are smallerbyabout T activities. Type of Letters 0.68 times. Practical application of the visual abilities in real - world Familiarity N point charts are widely recognized by UK practitioners. scenarios, such as reading, driving, etc Double Concept Doubling tl'!e point size.doubles the letter size and the retinal image size. isual Function V Font Use Point size is also used to specify font dimensions in computing. Visual Acuity Contrast Sensitivity Color Perception Depth Perception Motion Perception unctional Vision F Visual Integrity Visual Efficiency Visual Processing 31 OPT 032: LOW VISION Sloan M Series Charts N Read Charts M Itcomesinvariousforms,bothin his system is specified in M notation and works alongside Sloan T regular and reverse contrast. M Notation distance charts. Themostwell-knownversionsare here are five reading cards in the series, designed tohelpcalculate T acuity charts with text sizes Reading Cards the reading addition needed for low vision patientstoperformvarious ranging from 1.3LogMARto-0.2 reading tasks. logMAR,designedforuseata40 Working Distance The recommended distance to use the chart is 40 cm. cm distance. This feature isparticularlyhelpful for patientswhofindglarefroma white page uncomfortable. NAC (Practical Near Acuity Charts) P ThePNACaimstostandardizethenumberanddifficultyof words on a logMAr chart to quickly measure nearvisual acuity. Itusesrelatedthree-,four-,andfive-letterwordsoneach line. The chart is readfromthetopdownuntilthepersoncan no longer resolve the words. Bailey-Lovie Word Reading Charts he charts range in size from 1.6 to 0.0 LogMAR,whichcorrespondstoN80toN2,or T Size Range M10 to M0.25 hey have 17linesofunrelatedwords,withtwowordsinlargercategoriesanduptosix T Content words in smaller categories. Distance They are designed to be used at 25 and 40 cm distances. hey are great for measuring how well someone can read (reading acuity)butnotfor T Purpose assessing reading speed. REVIEW ON VISUAL FIELD TESTS rimary Care P Generally assessedtodetectthepresenceofearlyonset diseases and monitor progression. ow Vision L In order to determine the magnitude of loss, thereafter, equating functional loss with disability. epper Visual Skills For Reading Test (VSRT) P isual Field V Purpose Elderly patient who experienced a ○ Designed to test reading speed and fluency in stroke patients with macular disease. Developed right side hemiparesis Text Size Developed visual field loss ○ The charts range from N8 to N32 (M1-M4). Affected Reading performance, social Structure awareness, and mobility. ○ There are 13 lines of text, all the same size. PERIPHERAL VISUAL FIELD utomated Perimetry A This test maps out the visual field ofpeoplewithsevere vision impairment. It's thorough but can be stressfuland time-consumingforpatients.Theresultsoftenlookworse than the person's actual vision. Confrontational visual field assessments and tests using tangent screens, goldmann bowl perimeter, or arc perimeters are more accurate and useful. 32 OPT 032: LOW VISION ey to Accuracy K Thepatientissuspectedofhavingacentralorcecocentral Keeping the central point of vision stable is crucial for s cotoma. accurate results. Using a larger “crosstype”targethelps with this. hart 7 C This chart breaks the horizontally CENTRAL VISUAL FIELD oriented 6 degree x 8 degree central area, which corresponds anatomically to the normal macula, into 0.5 degree entral Perimetry C squares rather than 1 degree squares Automated perimeters, like the Humphreys 10-2 More useful in cases where there is programs, areusefulformeasuringthesizeanddepthof subtle visual disturbance blind spots (scotomas) in patients with macular or near-central vision issues. hart 5 C This chart consists of 20 evenly spaced msler Chart A white horizontal lines on a black This tool helps assess the subjective quality of central background. vision and detect visual distortions (metamorphopsia). Patients with central or paracentral metamorphopsia and choroidal disorders ehabilitation Advice and Assistance R may be especially sensitive. Therapeutic options: ○ Training techniques:patientscanlearnscanningand hart 4 C peripheral viewing techniques to maximize their This charthasolinestodistort;consistof remaining vision. small whitedotsrandomlydistributedover ○ Safe viewing strategies: it's crucial to develop and a black background like stars in the sky. practice safe viewing strategies. ○ Special devices: highly motivated patients might hart 6 C benefit from devices like reverse telescopes, fresnel prisms, or clip-on mirrors. This chart varies slightly from chart no. 5 It contains black lines against a white msler Grid Test A backgroundandtheareas1degreeabove and belowthefixationdotarebisectedby developed by dr. Marc Amsler, swiss Ophthalmologist in additional horizontal lines. 1920 Purpose: hart 2 C ○ Important in testing macular function ○ Chartconsistingofwhitelinesonblackbackground& The patient with a central scotoma may central white dot for fixation respond better if this chart is used. ○ Evaluates 20 deg. of vf surrounding fixation The only difference between this and the ○ This test is used for screening & diagnostic purposes standard grid chart is that diagonal lines intersectatthecenterofthegridtoforman rocedure P X. Can you see the central white dot in the center of the grid? While looking at the central dot, can you see all four angent Screen (Bjerrum Screen) T quadrants of the chart simultaneously? A type of kinetic perimetry used to Does the grid appear to have any missing or distorted assesstheintegrityofthecentral30 area? degree radius of the visual field. Are there any areas of the grid that have an unusual Test distance: 1 meter appearance? Consist of a black surfacemadeup Are any square blurring /missing? of black felt material stitched with radial lines at 15 degrees. Interval hart 1 C and circles at degree intervals. The standard Amsler grid. Is actually a form of Campimetry Merely a grid pattern consisting of In campimetry, the visual field is 0.5cm white squares, each tested on a flat surface. corresponding to 1 degree of visual field, set against a black background. et-Up S Arrange in 20 horizontal and vertical The tangent screen should be moderately and evenly rows making 20 squares each. illuminated (7FC). Px wears habitual distance correction. hart 3 C Monocularly Performed. Px’s eye should be in the level of the central fixation target This charthasanidenticalconfiguration Examiner stands on the side being tested. with that of the standard Amsler Chart exceptforhavingredsquaresinsteadof rocedure P white one in the black background. Show the patient the fixation point. 33 OPT 032: LOW VISION ell the patient you are going to test his side vision. T READING AND WRITING ASSESSMENT Instructhimtotellyouwhenheseesthetestobjectsinhis side vision and to alwaysmaintainfixationonthecentral fixation target. TYPICAL READING RATES Instruct the patient to say “gone” when the object disappears and “I see it” when it comes into view. ighted Individuals S Always observe the Px. 200 to 300 words per minute (wpm) Non seeing to seeing. Plot the blind spot. ow Vision Readers L Plot the limit of the isopter. To detect scotomas within the central field,theisopteris Mild: 100 to 150 wpm movedinaradialdirectionatanintervalof5degreesfrom Moderate: 50 to 100 wpm all directions. Severe: 25 to 50 wpm Smaller the target, the more sensitive the test. actors Affecting Reading Speed F ecording R Acuity Reserve Mark the location ofeachpointonthetangentscreenby Contrast Sensitivity puttingsmallpinsonthescreenandconnectthosepoints Visual Field Limitations on the chart. Text Characteristics ield of View F hildren With Low Vision C Superior = 50 degrees Grade 1 - approx 53 wpm Nasal = 60 degrees Grade 3 - approx 107 wpm Inferior = 75 degrees Temporal = 90 degrees TYPICAL WRITING RATES Bernell Handheld Disc Perimeter ighted Individuals S 20 to 30 words per minute (wpm) urpose P Itisdesignedforvisualfield ow Vision Individuals L testing Used in clinical, industrial, Mild: 15 to 25 wpm and training settings Moderate to Severe: often less than 15 wpm ey Features K actors Affecting Writing Speed F 13 inches arc radius Visual Acuity and Contrast 2 inches height Assistive Devices and Technology Adaptable positions (H, V, O) Motor Skills and Coordination 9 inches wand 1 - 4 mm targets ategories of Reading Rates C High Fluency Reading - 160 wpm esting Procedure T Survival Reading - 40 wpm Occlude one eye; px holds instrument horizontally. Optimal Reading - 300 wpm Target presented; px reports where it disappears/ reappears. OBJECTIVES Conduct test for temporal, nasal, superior, and inferior fields. ➔ to understand factors influencing reading and writing performance ➔ toimplementstrategiesthatenhancereadingfluencyand writing quality aterials M Reading Materials Writing Prompts Timer Recording Sheets METHODOLOGY ssessing Reading Performance A 1. Reading Task Setup ○ Select appropriate text ○ Prepare comprehension questions 2. Conducting The Reading Assessment 34 OPT 032: LOW VISION Instruct px to read aloud or silently ○ B inocularVisionAssessment:Evaluatinghowwellthe ○ Start the timer as they begin and as they end eyes work together, including depth perception and 3. Data Recording coordination. ○ Record the time taken to read the passage in seconds ○ Calculate reading rate: inocular Vision Testing B ReadingRate(wpm)=TotalWordsRead/Time Binocularvisiontestsareessentialforassessinghowboth (in minutes) eyes function together. . Comprehension Assessment 4 ○ Administer comprehension questions ey Aspects Include: K Stereopsis: The ability to perceive depth based on the ssessing Writing Performance A slightly different views from each eye. 1. Writing Task Setup Ocular Alignment: Checking for any misalignment or ○ Choose variety of prompts appropriate to the skill strabismus. level of the patient Ocular Motility: Ocular motility refers tothemovementof 2. Conducting The Writing Assessment the eyes and their ability to work together to maintain ○ Instructparticipantstorespondtothepromptwithina visual focus and alignment. specified timeframe (e.g. 5 minutes) ○ Start the timer as they begin and as they end Importance of Binocular Vision Testing in Low Vision 3. Data Recording ○ Count the total number of words written during the IdentificationofBinocularAnomalies-Lowvisionpatients session often have issues like suppression, diplopia (double ○ Calculatethewritingrate:WritingRate(wpm)=Total vision), or misalignment of eyes. Words Written / Time (in minutes) Improvement of Depth Perception - Depth perception 4. Quality Assessment relies on effective binocular vision. Testing allows for ○ Usearubrictoevaluateclarity,coherence,grammar, interventionsthatenhancespatialawareness,aidingtasks spelling, and overall structure of written responses like navigating stairs or driving. TailoredLowVisionAid-Acomprehensiveunderstanding verall Feedback O of binocular vision enables clinicians to identify the best What did you find easy or challengingaboutthereading low vision aid designed to address the specific visual task? challenges of the patient. What did you find easy or challenging about the writing task? irschberg Test and Krimsky Test H Any additional comments or suggestions? Purpose: To determine the approximate positions of the visual axes ofthetwoeyesunderbinocularconditionsat BINOCULAR VISION AND COLOR VISION TESTING near.Thistestisusedtoidentifyastrabismuswhenother more precise methods cannot be used. ow Vision L xtraocular Motility Test
