Visual assessment and colour vision.pptx

Visual assessment

1. VISUAL ACUITY FOR VISUAL ASSESSMENT -DINESH

2. DEFINITION Visual acuity is the clarity or sharpness of vision, representing the ability of the eye to discern the shape and details of objects at a given distance

3. TYPES Distant visual acuity Snellen’s chart Logmar visual acuity charts Pin hole test Near visual acuity Jaeger’s chart Roman test types Snellen's near vision test types

4. Snellen's test types The distant central visual acuity is usually tested by snellen's test types. The two distant points can be visible as separate only when they subtend an angle of 1 minute at the nodal point of the eye forms the basis of snellen's test types.

5. PROCEDURE OF TESTING For testing distant visual acuity,the patient is seated at a distance of 6m from the snellen's chart,so that the rays of light are practically parallel and the patient exerts minimal accommodation. The patient is asked to read the chart with each eye separately and the visual acuity is recorded as a fraction. Numerator being distance of patient from letters and denominator being smallest letters accurately read. Visual acuity 6/6 is normal.

6. If he cannot see the top line from 6m,he is asked to slowly walk towards the chart till he can read the top line. If the patient is unable to read the top line even from 1m,he is asked to count fingers(CF) of the examiner. His vision is recorded as CF-3’,CF-2’,CF-1’ or close to face depending upon the distance at which patient is able to count fingers. When a patient fails to count fingers, check for perception of hand movements (hand-movements appreciation) by moving examiner’s hand in front of the patient’s eyes.(HM +ve) When the patient cannot distinguish the hand movements,the examiner notes whether the patient can perceive light or not.(PL +ve,PL-ve)

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8. Other tests based on same principle as snellen's test Simple picture chart: for children more than 2 yrs. Landolt’s C-chart:used for illiterate patients. E-chart: used for illiterate patients.

9. LogMAR visual acuity charts It stands for logarithm of the minimum angle of resolution. A logmar chart comprises Rows of letters and has equal number of letters in each line. It is used at the distance of 4 m. It is design to enable a more accurate estimate of a acuity as compared to others, for this reason it is recommended in research settings.

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11. Pin hole test Pin hole test should be performed if the distant visual acuity is found abnormal. For example, if vision on snellen’s test is 6/24 and after pinhole,but in improves it indicates presence of refractive error. If vision does not improve with pinhole some other occular pathology is present.

12. VISUAL ACUITY FOR NEAR Near vision is tested by asking the patient to read the near vision chart,kept at a distance of 35 cm in good illumination with each is separately. Jaeger's chart : in this chart Prints are marked from 1 to 7 and accordingly patients acuity is labelled as J1 to J7 depending up on the print he can read. Roman test types: according to this chart,the near vision is recorded as N5,N8, N10, N12 and N18.

13. Jaeger's chart Roman test types

14. THANK YOU

15. Sense of contrast By Eishan

16. Introduction It is the ability of the eye to perceive slight changes in the luminance between regions which are not separated by definite borders. Loss of contrast sensitivity results in mild fogginess of the vision.

17. Clinical importance Contrast sensitivity is affected by various factors like Age,refractive errors, glaucoma, amblyopia, diabetes, optic nerve diseases and lenticular changes. Further, contrast sensitivity may be impaired even in the presence of normal visual acuity.

18. Measurement of contrast sensitivity. In clinical practice the contrast sensitivity can be measured by using any of the following charts with letters or stripes represented in various shades of grey: Arden gratings Cambridge low contrast gratings

19. Methods of testing Pelli-Robson contrast sensitivity chart which consists of letters arranged in triplets. The contrast sensitivity decreases from one triplet to next. Visitech chart Functional acuity contrast test (FACT)

20. Elamparuthi . R Roll no 20 COLOUR VISION TESTS

21. Colour blindness An individual with normal colour vision is known as trichromate. This is because the normal human eye can appreciate three primary colours (red, green and blue) due to presence of three different types of cones, i.e., red sensitive, green sensitive and blue sensitive. All colours of the spectrum can be perceived by fusion of these three primary colours in varying proportions. In colour blindness, mechanism to appreciate one or moreprimary colours is either defective (anomalous) or absent (anopia).

22. Tests for colour vision These tests are designed for : (1) Screening defective colour vision from normal . (2) Qualitative classification of colour blindness i.e., protons, deuteran and tritan. (3) Quantitative analysis of degree of deficiency, i.e., mild, moderate or marked .

23. 1 . Pseudoisochromatic charts . It is the most commonly employed test using Ishihara’s plates . In this there are patterns of coloured and grey dots which reveal one pattern to the normal individuals and another to the colour deficients.

24. 2. Edridge-Green lantern test. In this test the subject has to name the various colours shown to him by a lantern and the judgement is made by the mistake he makes. 3. Farnsworth-Munsell 100 hue test. It is a spectroscopic test in which subject has to arrange the coloured chips in ascending order. The colour vision is judged by the error score, i.e., greater the score poorer the colour vision. It is the most sensitive test for both congenital and acquired colour vision defects. It consists of 85 hue caps (not 100) and colour vision is judged by error score (higher score means poorer colour vision).

25. 4. Farnsworth D15 hue discrimination test It is similar test but utilizes only 15 hue caps. 5. City university colour vision test. It is also a spectroscopic test where a central coloured plate is to be matched to its closest hue from four surrounding. colour in each of 10 plates.

26. 6. Nagel’s anomaloscope. In this test, the observer is asked to mix red and green colour in such a proportion that the mixture should match the given yellow coloured disc. The judgement about the defect is made from the relative amount of red and green colours and the brightness setting used by the observer.

27. 7. Holmgren’s wools test. In this, the subject is asked to make a series of colour-matches from a selection. of skeins of coloured wools.

28. Thank you

29. Visual field Test Gagan Singh Yadav

30. # Introduction Visual field:- it’s a three dimensional area of a subjects surrounding that can be seen at any one time around an object of fixation

31. Normal extent of visual fields( monocular) :- superiorly – 50° Inferiorly- 70° Nasally- 60° Temporally – 90°

32. Central field:- it includes an area from the fixation point to a circle 30° away. - it contains physiological blind spot on the temporal side. -> Peripheral field of vision:- It refers to rest of area beyond 30° to outer extent of field of vision.

33. -> Scotoma:- - It refers to area of loss of vision totally( absolute scotoma) or partially ( relative scotoma) in the visual field.

34. # Methods of visual field testing . Manual perimetry:- Perimetry:-procedure for estimation of visual field. -> Kinetic perimetry:- -Moving target from non seeing to seeing area -it maps isopters. Eg:- confrontation test, goldmanns perimetry.

35. Static perimetry:- - target is stationary, intensity varied - more sensitive, reproducible. - used in glaucoma detection. -> confrontation test:- - simple bedside test. - examiner compares patients field with his own. - useful in gross field defects( hemianopia, quadrantopia)

36. 2 dimesional measurement of vision. All the location where the stimulus is first seen have equal sensitivity, these points were joined form a ringed shape locus of points called an isopter.

37. B. Automatic perimetry:- - Fully Computer controlled testing of visual fields Commonly performed using Humphrey visual field analyzer. Patient presses a button when light stimulus is seen Generate detailed field plots with defect pattern Considered gold standard for diagnosis and monitoring of glaucoma.

38. # Common visual field defects:- Glaucoma – Arcuate scotomas, paracentral scotomas. 2. Optic nerve lesion:- central scotoma 3. Chiasmal lesion( pituitary adenoma) - bitemporal hemianopia

39. 4. Optic tract lesion:- Homonymous hemianopia ( contralateral) 5. Occipital lobe lesion:- homonymous hemianopia with macular sparing.