Visual acuity examination(adult) Update (1).pptx

Examination of visual acuity

1. Visual acuity examination for adult CHAIRMAN : DR. MD. ASHIQUR RAHMAN AKANDA Associate Professor Department of Pediatric ophthalmology, NIO&H MODERATOR : DR. CHANDAN KUMAR PAUL Junior Consultant Department of Pediatric ophthalmology, NIO&H PRESENTER : DR. SONIA ISLAM Phase A Resident NIO&H

2. Visual acuity Definition: Visual acuity is the resolving power of eye by which objects are distinguished clearly from other. Visual acuity refers to the spatial limit of visual discrimination. Components of vision : Visual acuity Field of vision Colour vision Contrast sensitivity Light Brightness sensitivity

3. Visual acuity Components of visual acuity : Minimum visible Resolution Recognition Minimum discriminable or hyperacuity

4. Measurements of VA Measurements of VA is done to monitor change in vision with progression of disease and/or treatment plan. It is the way to measure blurr vision. VA must be measured on every patient at every visit. Visual acuity depends on : The refractive error of the eye The health and integrity of eye The test targets used The test conditions

5. Clinical measurement of VA Criteria : Normal testing distance (distance visual acuity ) -6m For near -33cm/40cm. Illuminated visual acuity chart Proper room illumination. Steps : Unaided VA ( OD,OS,OU) Pinhole VA (OD,OS) Aided VA(OD,OS,OU)

6. DISTANCE VISUAL ACUITY CHARTS Snellen visual acuity chart -6m bailey- lovie ( logMar ) -4m/2m/1m Landolt ring chart (C chart) Tumbling E chart

7. Procedure Patient seated 6 meters from the chart Illumination is 20 foot candles Each eye is tested separately VA is recorded as a fraction (6/60,6/36,6/24,6/12,6/9,6/6) Numerator : distance of the patient from the chart Denominator : smallest letters accurately read

8. Procedure If the patient can not see the top line from 6m, he is asked to slowly move towards the chart till he can read the top line (5/60,4/60,3/60,2/60,1/60). If the patient is unable to see even from 1 m, he is asked to count fingers of the examiner. When a patient fails to count fingers ,the examiner moves his hands close to the patient's face & ask whether he could appreciate the movement or not (HM +/-). When the patient cannot appreciate hand movement, perception to light is noted.(PL+/-)with projection of rays in four quadrants.

9. Formula

10. Near Acuity Chart Reduced snellel chart N chart M chart Jaeger chart

11. Procedure (Near Vision) Near vision tested by asking the patient to read a near vision chart kept at distance of 16 inches (40cm). Each eye should be tested separately and respectively . Record the binocular acuity achieved. The near vision is recorded as the smallest type which the patient can read comfortably

12. Jaeger’s Chart Consists of ordinary printer’s front of varying sizes Prints are marked from 1 to 7 and accordingly patient’s acuity is labeled as J1 to J7 depending upon the print he can read

13. Testing Pinhole Visual Acuity Position the patient and occlude the eye not being tested. Ask the patient to hold the pin whole occlude in front of eye that is being tested. That patient’s habitual correction may be worn. Instruct the patient to look at the distance chart through the single pinhole. Instruct the patient to use small hand or eye movement to align pinhole to resolve the sharpest image on the chart . Ask the patient to read the line with smallest letters that are legible to determined on the previous vision test without use of pinhole Record the Snellen acuity obtained and precede or follow it with the abbreviation PH

14. Picture

15. Mechanism of Pinhole

16. LogMar scale It stands for logarithm of minimum angle of resolution. The chart was designed by Bailie & Lovie for the Early Treatment Diabetic Retinopathy study (ETDRS). Which is designed to be used at a distance of 4 Meter. Also known as Bailie & lovie Chart.

17. Steps Set the patient 4 meters from the chart. Cover one eye, if cannot read, then move 1 meter & add 0.6. Repeat second eye. If still unable to read, then use other option. Example: It one read 0.4 line plus 3 letters of 0.3 line, he or she will have a score of 0.4-(0.2x0.3)=0.34. 19

18. Colour vision This is the inability to distinguish certain colour . Unexplained reduction in visual acuity e.g. 20/25 One or more cone type is missing or defective to any extend. Abnormal colour matching and colour confusion .

19. Colour Vision Chart

20. Colour Vision Test 1. Pseudoisochromatic test a. Ishihara colour vision chart b. AOHRR-American Optical Hardy Rand Rittle Plate 2. Arrangement test a. Franswoth Munsell-100 Hue test b. Fransworth D-15 test c. Anamaloscope Nagel’s anamaloscope

21. Some Diseases Associated with Reduced VA: Refractive errors Cataract Retinal detachment Retinopathy of prematurity Glaucoma Optic nerve atrophy Albinism Nystagmus

22. VA is the most fundamental and basic clinical examination in eye. Meticulous visual acuity assessment is essential. We all should practice it. VA is impotent for clinically and medico-legally. VA acuity is the opening door for examination of eye. Take Home Message