Visual field

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1. Visual field assessment in glaucoma patients Presenter Dr. Desta G.(R-2) Moderator Dr. Abeba T. ( associat. Professor of ophthalmology, Glaucoma sup.specialist,CHS,AAU)

2. Seminar outline Introduction Common visual field defects Glaucomatous visual defects Types of perimetry

3. Introduction The visual field is that portion of the external environment of the observer where in the steadily fixating eye can detect visual stimuli (International Perimetric Society (1978) ) TRAQUAIR – “HILL OF VISION IN THE SEA OF DARKNESS ”

4. Boundaries

5. Physiologic blind spot Corresponds to the area of the optic nerve head Located 15 temporal to the peak of the island Span – 5 deg horizontal -- 7 deg vertical Two thirds below the horizontal meridian 5

6. Color field Point at which passing from periphery to centre , the colour first becomes evident Extent of field for objects of same size and intensity white > yellow > blue > red > green

7. COMMON VISUAL FIELD Defects

8. SCOTOMA : focal region of abnormally decreased sensitivity surrounded by an area of normal sensitivity ABSOLUTE vs RELATIVE DEPRESSION : is an area of reduced sensitivity without a surrounding area of normal sensitivity appears as denting of isopters

9. Homonymous is when the defects are in the corresponding region of the visual field in both eyes. Hemianopia , there is a defect to the side of the midline in both visual fields . Quadrantanopia there is visual field defect in one quadrant

10. Congruousness describes the degree to which the field defects match between the two eyes. Generally, the more congruous the field defect the more posterior along the visual pathway the lesion is located. Isopter is a threshold line joining points of equal sensitivity on a visual field chart

11. A defect that affects the nasal field of one eye and the temporal field of the other eye is described as homonymous. Most widespread effects on vision occur where the nerve fibers of the visual pathway are tightly packed togather ,such as in optic nerve or optic tract. The defects in a homonymous field are congruent if the two defects are similarly shaped and are incongruent if the defect shapes are dissimilar

12. Nerve fiber bundle defects are the following 1 . P apillomacular bundle 2 . Sup and inf arcade bundle 3 . Nasal bundle

13. If temporal retinal fibers are affected, an arcuate defect can be produced that curves around the point of fixation from the blind spot to termination at the horizontal nasal meridian

14. a lesion affects a nasal bundle of nerves, producing a wedge-shaped defect emanating from the physiologic blind spot into the temporal field.

15. Injury to the optic nerve is accompanied by a visual field defect, a relative afferent pupillary defect, and atrophy of the affected nerve fibers, which eventually is manifested at the disc .

16. Complete section of one nerve produces total blindness of that eye. The pupil will not react to light directly but do consensually(affected side) The site of other eye is normal ; the pupil react to light directly but not consensually. The pupil on the injured side will constrict on accommodation.

17. If the optic nerve sectioned close to its entrance to the optic chiasm ,the inferior nasal fibers from the opposite side optic nerve that loop forward within the optic nerve will also be sectioned. In this case, in addition to visual field loss of the same eye, there is a superior temporal defect in the field of the opposite eye. This is known as anterior junction defect.

18. Optic chiasm Sagittal section of the optic chiasm will produce bitemporal hemianopia. The pupil react normally to direct light reflex , the consensual light reflex , and accomodation reflex. Lateral section of optic chiasm on one side divides the fibers originating from the temporal retina on that side produce nasal hemianopia. Lateral section on both sides divides the fibers originating from both temporal retinae, produce binasal hemianopia.

19. Optic tract Division on one side will result in contralateral homonymous hemianopia. The pupil react normally to the direct light reflex ,the consensual light reflex and accommodation reflex.

20. LGN Distraction of LGN produces contralateral homonymous hemianopia. The pupil react normally to the direct light reflex ,the consensual light reflex and accomodation reflex. Lesions here eventually cause optic atrophy. Because of point-to-point localization in LGN, lesions here produce moderately to completely congruent field defect .

21. Pie on the sky vs pie on the floor Where is the possible area of lesion?

22. Visual cortex Destruction of primary visual cortex produces contralateral homonymous hemianopia. The pupils react normally to reflex stimulation. T he macula is often spared if the posterior cerebral artery is blocked by thrombosis because of anastomosis between posterior and middle cerebral arteries at this site.

23. Congruous field defects occur with lesions involving the calcarine cortex More anterior involvement often produces incongruous field defects, suggesting that the corresponding fibers lie farther apart more anteriorly in the visual pathways.

24. Glaucomatous VF loss Early: - Diffuse reduction / constriction of isopters - Paracentral scotoma - Bjerrum / arcuate - Nasal steps - Temporal wedge Advanced: Double arcuate with peripheral extension Central and temporal island of vision 26

25. Early glaucomatous VF defect Paracentral scotomas early sign of localized glaucomatous damage Could be multiple along the course of the nerve fiber bundle 27

26. Early glaucomatous VF loss… Bjerrum / arcuate scotomas More advanced bundle of nerve fibers loss 28 Chorioretinal lesions: Myopic deg Atypical RP BRVO, BRAO Juxtapapillary chorioretinitis ONH anomaly: - Pits - Colobolmas - Drusen Neuropathy -Papillitis -Chronic papilledema -Ischemic optic neuropathy -Retrobulbar neuritis DDX

27. Early glaucomatous VF loss Nasal steps Peripheral step-like defect along the horizontal meridian From asymmetric loss of nerve fiber bundles in the superior and inferior hemifields Frequently occurs in association with arcuate and paracentral scotomas Accounts for 7% of initial visual field defects 29

28. Early glaucomatous VF loss Temporal wedge defect Damage to nerve fibers on the nasal side of the optic disc Less common Does not respect the horizontal meridian 30

29. Early glaucomatous VF loss… Enlargement of blind spot Vertical elongation may occur with the development of a Siedel's scotoma, an early arcute defect May also result from Peripapillary atrophy

30. Advanced glaucoma VF loss 1. Double arcuate defect Superior and inferior arcuate fibers lost, leaving only papillomacular 32

31. Advanced… 2. Central and temporal island of vision The typical visual field in advanced glaucoma 3. Diffuse depression Non-specific to glaucoma Medial opacity : Cataract, corneal scare Refractive error Pupil miosis Aging Patient: fatigue, inattentiveness or inexperience with the examination 33

32. What is perimetry ? Measurement of visual functions of the eye at topographically defined loci in the visual field1 Measures differential light sensitivity, or the ability of a subject to distinguish a stimulus light from background illumination2

33. Techniques of examination Confrontation Amsler grid Kinetic Static

34. Vf by confrontation Preliminary , quick and easy way to measure visual field Patients and examiner at same level Compares the visual field of eye of patient with opposite eye of the examiner in a plane perpendicular to line of gaze Red pin is particularly useful for neurological cases

35. Kinetic Perimetry Stimulus is moved from a non-seeing area of the visual field to a seeing area along a set meridian Tangent screen, Glodmann perimeter

36. Tangent screen Simple to perform Used to screen pts for VF defect Isopter : contour obtained by same size and brightness target Patient sits 1-2m away from the screen Series of isopters can be obtained with smaller and dimmer targets, representing the contour of the island of vision Testing object moved from periphery to the center ( seeing to non seeing) 40

37. Tangent… Used to identify, and localize scotomas in the island of vision Deep/ absolute scotoma : area where largest and brightest test object is not visible Relative/shallow scotoma : Defect obtained with small or less bright testing object Drawbacks Non standardized lightening of the screen and brightness of the test object Measures the central 30 degree only 41

38. Goldmann perimetry • It is usually kinetic (but static perimetry is used for the central field ). • Skilled operators are required. • It is useful for patients who need significant supervision to produce a reliable visual field .

39. The target sizes are indicated by Roman numerals (0–V ), Representing the size of the target in square millimeters, each successive number being equivalent to a 4-fold increase in area.

40. Methods The machine should be calibrated at the start of each session. Distance and near add with wide aperture lenses are used during testing(to prevent ring scotoma ). Aphakic eyes should, where possible, be corrected with contact lenses

41. Seat patient with chin on the chin rest and forehead against rest. Occlude the non test eye; ask patient to fix gaze on central target and To press the buzzer whenever he/she sees the light stimulus .

42. From the opposite side of the Goldmann , the examiner directs the stimulus to map out the patient’s field of vision to successive stimuli ( isopters ).

43. The examiner should move the stimulus slowly and steadily from unseen to seen, Inward for periphery and outward for mapping the blind spot/central scotomas

44. The examiner should monitor patient fixation via the viewing telescope . The central 20° with an extension to the nasal 30° is appropriate for picking up early glaucomatous scotomas

45. Interpretation The intensity of the light is represented by an Arabic numeral (1–4), each successive number being 3.15 times brighter (0.5 log unit steps). It is measured in apostilbs ( asb ).

46. A lower-case letter indicates additional minor filters , progressing from a , the darkest, to e , the brightest . Each progressive letter is an increase of 0.1 log unit .

47. Results Isopters are contours of visual sensitivity. Common isopters plotted are as follows • I-4e (0.25 mm2, 1000 asb stimulus). • I-2e (0.25 mm2, 100 asb stimulus). • II-4e (1.0 mm2, 1000 asb stimulus). • IV-4e if smaller targets are not seen (16 mm2, 1000 asb stimulus).

48. Standard automated perimetry Automated static perimetry , also called standard automated perimetry ( SAP) is the Gold standard for glaucoma evaluation. Reasons It is more sensitive to early glaucoma changes Since it is computerized less variability among operators statistical programs can be used to do important tasks such as comparing the patients’ responses to a normal group of subject responses, subtract out the effect of diffuse depression on the field as occurs in cataract, and provide information on progression

49. Testing Algorithms in Standard Automated Perimetry 1. Suprathreshold tests present a stimulus brighter than expected and determine whether a subject can see it or not Uses in a community screening setting or when assessing neuron-ophthalmic, retinal disease, or visual disability. but is not recommended for glaucoma diagnosis or follow-up

50. 2. Full threshold testing is a trial and error system whereby stimuli are shown and then increased or decreased in intensity until an estimate is made of the amount of light that can be seen approximately 50% of the time. 4-2algorithm Time consuming (15-20min)

51. 3. The Swedish Interactive Threshold Algorithm (SITA ) There are two SITA programs to choose from, SITA Standard (preferred) and SITA Fast . Decrease time by 50% than FTS Program selection includes the central 30°, 24°, 10°, or full field .

52. Humphrey perimetry • Sensitive and reproducible • Fixation monitoring (by tracking gaze and retesting the blind spot).

53. Method of Humphrey visual field (HVF) The machine automatically calibrates itself on start-up. Selection of programs includes the following : full threshold or Swedish interactive threshold algorithm [SITA ] central 30–2, 24–2, 10–2 ). Suprathreshold testing (screening central 76 point, full-field 120 point,and Esterman ). Colored stimuli can also be use .

54. What to look for… • Reliability indices (Table 2.2). • Absolute retinal thresholds. • Comparison to age-matched controls. • Overall performance indices (global indices).

55. Unreliable VF Fixation losses ≥ 20 %, False positive error ≥ 33 %, False negative error ≥ 33 %

56. Humphery data display Reliability indices Thresholds grid (Numerical) Graphic grayscale Total and pattern deviation plots with their probability maps Global indices 65

57. Steps to interpreting a HVF 1. Check patient name and age If a younger age is entered, some graphs on the field can look much worse. Many of the calculations are based on the age group of the patient 2. Check the field parameters Was this a 30-2 or a 10-2? Was the correct prescription used? Was the pupil size very small? (Makes the field look worse.) What was the stimulus size used? 66

58. Steps to interpreting a HVF 3. Check reliability How many fixation losses, false positives and false negatives are present? Is the SF high? 4. Examine the all numeric data charts as well as the corresponding graphs and compare them to previous HVFs Are new defects emerging? Are the focal defects found on the pattern deviation graph the same over time? Is the mean deviation getting worse? Are there focal defects on the pattern deviation not seen on the total deviation?

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60. Probability values (p) These values indicate the significance of the defect <5%, <2%, <1%, and <0.5 %. The lower the p value, the greater its clinical significance and the less the likelihood of the defect having occurred by chance .

61. Almost always localized Respect horizontal meridian Begin nasal to the blind spot Almost always detectable within the central 30° CHARACTERISTICS OF GLAUCOMATOUS VISUAL FIELD DEFECTS

62.   VISUAL FIELD SEVERITY GRADING SYSTEM FOR THE HUMPHREY VISUAL FIELD ANAYLZER (STAGES 0–5 ) Stage 0 doesn’t meet any criteria from stage1 Stage 1: Early Defect Mean deviation (MD) ≤ –6.00 dB and at least one of the following: A, On pattern deviation plot, there exists a cluster of 3 or more points in an expected location of the visual field depressed below the 5% level, at least 1 of which is depressed below the 1% level B, Corrected pattern standard deviation/pattern standard deviation significant at P < 0.05 C, Glaucoma hemifield test “outside normal limits ”

63. Stage 2: Moderate Defect MD of –6.01 to –12.00 dB and at least one of the following: A On pattern deviation plot, greater than or equal to 25% but fewer than 50% of points depressed below the 5% level, and greater than or equal to 15% but fewer than 25% of points depressed below 1% level B At least 1 point within central 5° with sensitivity of < 15 dB but no point within central 5° with sensitivity of < 0 dB C Only 1 hemifield containing a point with sensitivity < 15 dB within 5° of fixation

64. Stage 3: Advanced Defect MD of –12.01 dB to –20.00 dB and at least one of the following: A .On pattern deviation plot, greater than or equal to 50% but fewer than 75% of points depressed below the 5% level and greater than or equal to 25% but fewer than 50% of points depressed below 1% level B .Any point within central 5° with sensitivity of < 0 dB C. Both hemifields containing a point(s) with sensitivity < 15 dB within 5° of fixation

65. Stage 4: Severe Defect MD of –20.00 dB and at least one of the following: A. On pattern deviation plot, greater than or equal to 75% of points depressed below the 5% level and greater than or equal to 50% of points depressed below 1% level B. At least 50% of points within central 5° with sensitivity of < 0 dB C. Both hemifields containing greater than 50% of points with sensitivity < 15 dB within 5° of fixation

66. Stage 5: End-Stage Disease Unable to perform Humphrey visual fields in “worst eye” due to central scotoma or “worst eye” visual acuity of 20/200 or worse due to primary open-angle glaucoma. “Best eye” may be any stage

67. References Yanoff & Duker : Ophthalmology, 3rd ed . Duanes foundation of clinical ophthalmology 2007ed BCSC neurophthalmolohy and glaucoma Dr. Ababa teaching lecture 2013 Online sources

68. Thank you