Mohamed Abdelzaher

1. Interpretation Of Perimetry Mohamed Abdelzaher

2. When is Perimetry Called For? GLAUCOMA • most conclusive and concrete means of establishing a diagnosis of chronic open-angle glaucoma • great value in diagnosing neurological diseases but When it comes to managing neurological disease, field testing is not as crucial a technique as it is in glaucoma management; neuroimaging can often replace perimetry. • direct observation of the fundus through ophthalmoscopy is usually of greater value in retinal diagnosis NEUROLOGICAL DISEASES RETINAL DISEASES

3. Ordering a test

4. Choosing a Test 1) Central vs Peripheral test 2) Stimulus size 3) Test strategy 4) Follow-up test 5) Testing for special conditions

5. Central vs Peripheral testing GLAUCOMA • Central 30-2 or 24-2 • Central 30-2 or 24-2, Exception: small central scotoma is suspected in a patient who has normal or near-normal visual acuity but a history that suggests acute optic neuritis - central 10-2 • Peripheral e.g. to rule out retinal detachments, or to differentiate between detachment and retinoschisis in eyes that cannot be well visualized ophthalmoscopically NEUROLOGICAL DISEASES RETINAL DISEASES

6. Stimulus size • Standard size is Goldmann size III • Small enough (0.43 degrees in diameter) to be used even in fairly detailed examinations, and large enough to be visible when the patient’s refractive correction is not quite perfect The typical blind spot is roughly 5 by 7 degrees. About two hundred size III stimuli or 12 size V stimuli fit inside the area of a typical blind spot.

7. Exception • Advanced glaucoma: use size V stimulus which is 4 times size III stimulus, WHY? • Testing with size V stimuli will result in sensitivity levels that are 5 to 10 decibels higher than those found using size III, often extending the available sensitivity range and making it possible to follow such patients. • NB. When the size V stimulus is used, one no longer has access to several of the analytical follow-up tools available for the standard size III tests

8. Same patient tested with size V stimulus and to the 10-2 pattern resulted in enough data for meaningful long term follow-up 30-2 test using a size III stimulus does not contain enough data for good follow-up

9. Test strategy

10. Switching from the older Full Threshold strategy to SITA Standard cuts test time almost in half for glaucoma patients. Modern threshold perimetry can be very time efficient. Normal subjects can be tested in about 4 minutes; glaucoma patients will take somewhat longer.

11. Follow-up test The standard test • SITA Standard or SITA Fast • 30-2 or 24-2 programs for both glaucoma detection and follow-up * central vision loss: e.g. macular degeneration Patient fixates in the center of a large diamond pattern * very late stages of glaucoma: SITA Standard or SITA Fast 10-2 test use larger stimulus,size V (not with SITA) Exceptions - Changing test programs in follow-up also makes comparisons with earlier tests more difficult and less exact. - When switching from the earlier standard Humphrey threshold tests, Full Threshold, to the corresponding newer, faster SITA Standard or SITA Fast, the most relevant comparisons can be made by focussingon probability plots. NB

12. Testing for special conditions Blepharoptosis Driving Disability • Goal: rule out profound visual dysfunction • Use: stimulus Goldmann III 4e (10dB) suprathreshold testing Drug induced maculopathies e.g. chloroquine, hydroxychloroquine 10-2 test pattern, standard size III white stimulus, SITA standard or SITA fast

13. 30-2 SITA Standard threshold test 24-2 SITA Standard threshold test • When perimetric test is needed using a size III white stimulus is the best choice in most cases OR

14. Glaucomatous visual field loss

15. RNFL & ONH Anatomy • Arcuate path of axons • Superior & Inferior temporal axons do not mix, respect the horizontal raphe • Retinotopic organization of axons in optic disc

16. Common glaucomatous field defects and their anatomical correlates 1) Generalized depression: - Can be an early sign of glaucoma - Non specific, also occurs with aging, miosis, or hazy media • Generalized depression can increase the physician’s suspicion that glaucomatous damage has occurred, especially if it is: … unilateral or …. more pronounced in the eye with the higher pressure or larger cup/disc ratio - If the patient has generalized field loss, the MD has a negative sign Mild: MD < -6 dB Moderate: MD < -12 dB Severe: MD > -12 dB

17. 2) Irregularity of the visual field: - lack of uniformity in the visual field - variation of decibel level among contiguous points that is greater than that anticipated in normal patients of the same age - These areas of loss appear non-uniformly throughout the field - This variation is expressed statistically as the standard deviation of the deviations found in the, Humphrey uses the termpattern standard deviation(PSD),

18. 3) Nasal step: • Limited field loss adjacent to the nasal horizontal meridian with at least one abnormal point (p < 5%) at or outside 15 degrees on the meridian. Cannot include more than two significant points (on either plot) in the nerve fiber bundle region on the temporal side • Anatomy: widespread involvement of fibers in the optic disc will seldom be entirely symmetrical, but usually will involve a larger percentage of lost fibers in either the inferior or superior half of the optic disc. As a result, differential light sensitivity in the opposite visual field halves will not be the same • Occurs early in glaucoma and may persist to last stages of the disease

19. 4) Isolated Paracentralscotomata: • A relatively small visual field abnormality (a cluster or a single point) in the nerve fiber bundle region that is generally not contiguous with the blind spot or the nasal meridian. • In particular, it does not involve points outside 15 degrees that are adjacent to the nasal meridian. • NB: Scotomata smaller than 6° may be missed in 30-2 field. This is particularly critical in the paracentral region where even very small scotomata can be visually symptomatic. Spacing the test spots closer than 6° (for example 3° apart) increases the chances of identifying such scotomata but also increases the test time to an impractical level. If one is concerned about identifying or monitoring a paracentralscotoma, use the central 10-2 test. notch is partial, that is, it involves only a portion of the axons in the affected area of the optic disc

20. 5) Arcuate defect (Bjerrumscotoma) begins at the blind spot, arcs around point of fixation, in the nerve fiber bundle region, end abruptly in at least one point outside 15 degrees adjacent to the nasal horizontal meridian (corresponding to temporal raphe) Anatomy: focal notch in ONH reaching the edge of the disc NB: double arcuate defect Represents middle to late stage glaucoma

21. 6) Temporal step: A small visual field defect that is temporal to the blind spot may develop as an isolated finding or in conjunction with other glaucomatous defects more commonly found as a component of late-stage disease Anatomy: erosion of the nasal aspect of the optic disc

22. 7) Enlargement of the blind spot: • Nonspecific changes for glaucoma • If the blind spot enlarges in an arcuate manner, it is called a Seidel’s scotoma and may be seen in early glaucoma

23. 8) End stage defects (central and temporal islands): small central island and a larger temporal crescent remaining Anatomy: most of the axons at the superior and inferior poles of the disc are destroyed, leaving only the papillomacular bundle and some nasal fibers

24. Reversal of visual field defects Fluctuation Increasing familiarity with the test Patients following therapy for glaucoma

25. Pitfalls • The narrower normal limits of SITA mean that statistically and clinically significant defects can be identified in probability plots even before they are clearly visible in grayscale representations. • This happens regularly in patients who are developing early glaucomatous visual field loss, and it is therefore important to focus on probability plots rather than grayscale representations.

26. A large percentage of glaucoma patients have coexisting media opacities, complicating follow-up analysis of their visual fields. These problems can be largely avoided by using analyses based on patterndeviation.

27. Large, sudden visual field changes are not typical in glaucoma. Such changes often occur for reasons other than progression of the glaucomatous disease process, e.g., arterial or venous occlusions in the retina or neurological disease. If a large change is seen and part of the field loss seems hemianopic or occurs in the other eye as well, neurological causes are generally the rule. Glaucomatous field defects may not correspond well to the amount of cupping of the nerve head. During the acute phase of angle-closure glaucoma in patients with high IOP, corneal edema and retinal ischemia can produce bizarre field defects that have little clinical value for following disease progression. After the pressure has been normalized, field defects may remain and may sometimes be extensive if ischemic atrophy of the nerve has occurred. In such cases, pallor of the nerve may be more severe than cupping.

28. Visual field artifacts: 1) Perimetric learning: • a large minority, probably 10% to 20%, of patients with a normal visual field do not produce an entirely normal test result on their first test • Typically, such fields show depression of sensitivity in the mid-peripheral area 20 to 30 degrees from fixation, while the very central field is normal • How to avoid? • Use shorter SITA test • Use 24-2 test point pattern • Do not rely entirely on the 1st test result, repeat

29. 2) Eyelid artifacts: • patients with somewhat droopy eyelids will often produce grayscale results that look relatively dark superiorly • this type of pattern is common and normal is obvious from the probability plots, where it usually does not result in readings indicating high statistical significance

30. 3) Correction lens artifacts: • Strong positive correction lenses --- concentrically contracted field • Misaligned lenses or their rims may create artifactual patterns

31. 4) The cloverleaf field: - very characteristic artifactual pattern • threshold values are normal or near normal at and sometimes around the four primary points where the test begins in all Humphrey threshold programs, but they are much reduced at other locations where the threshold is measured later in the test • occurs when the patient has responded more or less appropriately during the first part of the test, and then given up • You have to instruct and supervise patients

32. 5) The “Trigger-Happy” field: • The patient presses the response button as often as possible, resulting in large numbers of false responses given when, in fact, the patient has not seen the stimulus. • This will push up measured threshold values at some points to levels that no human can see. • The result is a classical “trigger-happy”field, characterized by patches of abnormally light or even entirely white tones in the grayscale presentation. • High false +ve • GHT: “Abnormally High Sensitivity”

33. Other diseases may cause arcuate nerve fiber bundle visual field defects that may be confused with glaucomatous damage: 1) Chorioretinitis 2) Myopic retinal degeneration 3) Refractive scotomata 4) Trauma 5) Retinal laser damage 6) Optic nerve ischemia 7) Optic nerve compressive lesions 8) Optic neuritis 9) Drusen of optic nerve head Glaucoma is a jigsaw puzzle in which all the ‘pieces’ of the disease should fit. If a piece Does not fit properly, the physician should be Suspicious that it may belong to some other Puzzle (disease).

35. Neurological visual field loss

36. In the era of CT and MRI, perimetry remains simple and cost-effective method of making neurological diagnoses because the visual system occupies or passes through so much of the brain. • SITA Standard has been found to be at least as good as the older Full Threshold test in detecting optic neuropathies and hemianopias.

37. Optic nerve diseases Central scotoma Centrocecalscotoma Altitudinal defect Enlargement of blind spot Arcuate defect Optic neuritis: e.g. Toxic, Compressive Drusen, Ischemia AION Optic disc swelling

38. Optic chiasm lesions - e.g. pituitary adenomas, craniopharyngiomas, suprasellarmeningiomas, aneurysms coming from the arterial circle of Willis

39. craniopharyngioma Pituitary adenoma Bitemporal hemianopia

40. Post chiasmal lesions • Respect the vertical meridian • More posterior  More congrouos “extent, pattern” - Extensive defect: Homonymous hemianopia Incongrouoshemianopia Congrouoshemianopia

41. LGB lesion: Homonymous Sectoranopia Homonymous Quadrablesectoranopia

42. Optic radiation and visual cortex lesion:

43. Visual pathways: correlation of lesion site and field defect

44. various causes of visual loss according to lesion site within the afferent visual pathway

45. Visual field loss In retinal diseases

46. Most retinal lesions are visible on ophthalmoscopy • Importance of field: • field defects found accidentally • to determine whether encountered field loss is caused by one disease or the other e.g. in glaucoma follow-up

47. ARMD • central scotoma • More evident with 10-2 test • Patient tested with the large diamond fixation target

48. CSR • central scotoma • VA is moderately reduced • Resulting field loss may be discrete and visible only on probability plots

49. Retinochoroiditis • arcuate or wedge-like defects (DD, glaucomatous field defect) • Field defects: • deep and have sharp borders • show much less variability from test to test than glaucomatous lesions

50. Diabetic retinopathy • relative and multifocal “mottled” defects • Visible in moderate and more advanced stages