Clinical Examination of V isual System

1. Clinical Examination of Visual System

2. Just a revision…… • Some formulas and concepts … • Some tips to remember certain aspects in clinics.. • “Normal Values” • Few questions for discussion…

3. Accommodation • Amplitude of accommodation • Hofstetter formula • Maximum = 25 – 0.4 X age • Average = 18.5 – 0.3 X age • Minimum = 15 – 0.25 X age

4. AC/A AC/A=IPD (in cms) + NWD (in meters)(horizontal near phoria (Hn)-horizontal distance phoria (Hf)) Eso is taken as plus and exo is taken as minus while the values are entered in the formula • Low and high AC/A in relation to excess or insufficiency. • Insufficiency always has a low AC/A e.g. CI, DI (insufficient = low) • Excess always has a high AC/A e.g. CE, DE (excess = high)

5. Treatment of vergence dysfunction • High AC/A = Excess (CE, DE) = lenses are Effective in treatment • Normal AC/A = (Basic Eso, Basic Exo) sometimes effective • Low AC/A = Insufficiency (CI, DI) = lenses are Ineffective in treatment. • Way to remember that plus lenses induces exo The plus sign (+) looks like an rotated X

6. Vergence • What prism stimulates what type of vergence Mnemonic = “BIN BOP” • BI stimulates Negative Fusional Vergence • Negative implies divergence • BO stimulates Positive Fusional Vergence • Positive implies convergence . • Prism • The prism makes the eye deviate in the direction of the apex • When correcting eye deviations, point the APEX toward the direction of deviation

7. EOM Intort Intort Also remember SIn RAd

8. 1 = 2pd 1mm = 7 Recording Position of Reflex 7 or 15 prism 15 or 30 prism 30 or 60 prism 45or 90 prism 45°or > 90 prism Between center of pupil and pupillary border. Pupillary border. Between pupillary border and limbus Limbus Beyond limbus

9. HESS CHART • PURPOSE: • To diagnose paretic/paralytic muscle. • EQUIPMENT: • Red-green filter • Hess screen(a screen that has a red dot in 8 inner positions and 16 outer positions) • Green light projector

10. PROCEDURE • The test is done at a distance of 50 cms from the Hess screen with the red-green goggles over the patient’s habitual correction. • The eye with the green filter is the testing eye and the eye with the red filter is the fixating eye. • The patient is asked to coincide the green light projector against the individual red dots.

11. Recording: • - The two charts are compared • - The smaller chart indicates the eye with the paretic muscle • - Larger chart  eye with the normal but over acting muscle

13. The following are true about Hess's test: True a. Ocular dissociation is necessary b. It can be used to calculate the amount of ocular deviation c. A visual acuity of better than 6/12 is essential for the testing d. The eye with restricted movement usually has a smaller field on the the Hess's chart e. It can be used to test the field of binocular single vision. True True True False

14. Diplopia charting • Purpose: • To diagnose paretic muscles. • Equipment: • Red - Green filter • Streak light

15. Procedure • The patient is asked to wear the red-green goggles over his habitual correction with the red filter in front of the right eye. • The patient is asked to fixate the streak light with his paretic eye (in order to elicit the maximum deviation). • The light is moved from the primary position into all of the other eight directions of gaze.

17. For each direction the patient is asked to inform the examiner about the kind of diplopia he experiences (horizontal/vertical/crossed/uncrossed) and the amount of separation between the red and green light • The direction of greatest separation will identify the paretic muscles

18. Normal values

24. Questions…

25. The following about Fresnel's prism are true: a. its power is determined the thickness of the base b. the visual acuity is affected by the power of the prism c. it is normal fitted to the front of the spectacle d. the maximum prismatic power than an adult can tolerate is usually around 15 dioptres e. dividing the strength of the prism between the two eyes improves the comfort of the patient false True false false True

26. Regarding the fusional reserves: a. the horizontal fusional reserve is higher than the vertical fusional reserve b. the positive fusional reserve is higher for distance than near c. the positive fusional reserve is affected by the subject's accommodative reserve d. the horizontal fusional reserve decreases with age e. the vertical fusional reserve is decreased in patient with reduced accommodative reserve True False True True False

27. With regard to Bagolini's glasses: a. the test is only useful for adult b. contain two lenses one with striation set at 90 degrees and the other at 180 degrees c. amblyopia in one eye always result in perception of only one line d. a cross is only seen in subjects with binocular single vision e. can be used to test the presence of abnormal retinal correspondence when combined with cover / uncover testing False False False True True

28. The range of stereoscopic vision as measured by the following tests are true: a. 3000 to 60 seconds of arc with the Frisby's test b. 3000 to 40 seconds of arc with the Titmus test c. 480 to 15 seconds of arc with the TNO test d. 1200 to 600 seconds of arc with the Lang stereostest e. 3000 to 15 seconds with the synotophore False True True True False

29. Myopic shift occurs in: a. keratoconus b. spasm of the ciliary body c. staphyloma d. lens subluxation e. brittle diabetes True True True True True

30. Induced hyperopia occurs in: a. cystoid macular oedema b. wearing of RGP lens c. presbyopia d. nuclear sclerosis e. posterior dislocation of the lens True True True False True

31. The following are true about indirect ophthalmoscopy: a. the aerial image of the retina is formed between the subject's eye and the condensing lens b. the aerial image of the retina is an inverted real image c. in an emmetrope, a 30D condensing lens produces a larger retinal images than a 20D lens d. in an emmetrope, a 30D condensing lens gives a larger visual field than a 20D lens e. for a given condensing lens, the aerial image of a hypermetropic retina is larger than a myope. False True False True True

32. The following are true about direct ophthalmoscopy: False a. the field of view is about 25º b. refractive error has a significant effect c. the magnification is 15X d. the field of view increases as the distance between the observer and the patient increases e. the fundus of a patient with high astigmatism can be sharpened with correcting lenses True True False False

33. In colour vision testing: a. the illumination should be equivalent to the morning daylight in northern hemisphere b. Farnsworth-Munsell hue 100 test uses 84 coloured discs c. the discs of Farnsworth-Munsell hue 100 tests have the same brightness and saturation. d. D-15 is a modified Farnsworth-Munsell (FM) hue 100 e. Ishihara is most useful for picking up congenital red-green defect False True True True True

34. Amsler's grid: • Should be read at 60cm • when used at the correct distance each square subtend one degree of arc on the retina • Of the most commonly used type contains 360 small squares d. Of the most commonly used type contains small squares each measuring 5 X 5mm e. Is useful for self-monitoring in patients at risk of retinal detachment False True False True False

35. In applanationtonometry False a. the area flattened is 13.06mm² b. based on Imbert-Fick principle c. the intraocular pressure (IOP) can be calculated by the formula area=force/IOP d. increased corneal curvature is associated with a falsely high IOP True True True

36. THE FOLLOWING ARE TRUE ABOUT THE JONES' TEST IN A PATIENT WITH EPIPHORA: True a. It is used to detect functional epiphora b. It should be performed before syringing of the nasolacrimal system c. A positive Jones I test suggests either hypersecretion or functional epiphora d. A positive Jones II test suggests partial blockage below the lacrimal sac e. Jones II test is not necessary if Jones I test is positive False True True True

37. In the measurement of the palpebral fissure: a. in patients with malposition of the lower lid, MRD gives a more accurate measurement of ptosis than the nterpalpebral fissure b. MRD is the distance between the upper eyelid margin and the corneal light reflex in the primary gaze c. ptosis is present if the MRD is less than 2 mm d. the MRD is increased in facial nerve palsy e. in normal persons, the upper lid is at the level of the limbus True True True True False

38. The following are true about Hertel'sexophthalmometer: a. the measurement may be affected by the presence of strabismus b. the foot plate should rest on the lateral canthus rather than the orbital for accurate reading c. patients of African origin has a higher normal reading than European d. a difference in readings between the two eyes of up to 5 mm is normal in up to 50% of the population e. can be used to monitor the progress of Grave's eye disease True False True False True

40. Slit Lamp Illumination techniques

41. 1. Diffuse illumination • Main Applications • General surveys of anterior eye segments. • Assessment of soft contact lenses. • Settings • Microscope positioned at 0° • Angle of slit illumination system approx. 30° - 50° • Desired Mx.

42. 2. Direct focal illumination • Main Applications • Illuminating and viewing path intersect in the area to be examined (e.g. Individual corneal layers) • Cells in the aqueous humour. • The crystalline lens is viewed. • Settings • The angle between illuminating and viewing path should be as large as possible (up to 90°) • Slit length should be kept small (about 0.1 mm to 0.2 mm) • Mx variable

43. Direct focal illumination

44. 3. Indirect illumination • Settings • Narrow to medium slit width • Desired Mx The axes of illuminating and viewing path do not intersect at the point of image focus. Reflected, indirect light illuminates the area of the anterior chamber or cornea to be examined. This method provide glare free viewing, always seen along with direct illumination

45. 4. Retro illumination • There are two types of retro-illumination. • Direct retro-illumination caused by direct reflection at surfaces such as the iris, crystalline lens or the fundus. • Indirect retroillumination caused by diffuse reflection in the medium, i.e. at all scattering media and surfaces in the anterior and posterior segments • Settings • The slit width 1 - 2 mm wide and 4 - 5 mm high. • Direct alignment.

46. 5. Specular reflection • Illumination and viewing system positioned such that the angle of incidence is equal to the angle of reflection . • Can see tear film, epithelium, posterior endothelium and keratic precipitates. • Settings • This method is monocular procedure. • High magnification

47. Sclerotic scatter • Settings • A narrow vertical slit (1-1.5mm in width) is directed in line with the temporal (or nasal) limbus. • Magnification as low as 6x - 10x is used • The room illumination is kept as dark as possible. • The principle behind sclerotic scatter is total internal reflection. • A halo of light will be observed around the limbus as light is internally reflected within the cornea, but scattered by the sclera. • Corneal opacity, edema or foreign body will be made visible by the scattering light, appearing as bright patches against the dark background of the iris and pupil.

48. 7. Oscillatory illumination • A beam of light is rocked back and forth by moving the illuminating arm or rotating the prism or mirror. • Occasional aqueous floaters are easier to observe. 8. Tangential illumination • The iris is examined under very oblique illumination while the microscope is aligned directly in front of the eye. • Useful for examining tumours and naevi of the iris.

49. In slit-lamp examination: a. specular reflection is useful in examining the corneal endothelium b. the angle of incidence and reflection are equal in specular reflection c. total internal reflection is used in sclerotic scatter d. in retroillumination, a secondary light source is used to illuminate a more anterior surface e. corneal oedema is best highlighted with retroillumination