Visual field defects

visual field- its assessment, defects, diseases associated. Types of visual field defects. visual field defects in glaucoma in detail. Humphrey's visual field analyser chart.

1. VISUAL FIELD DEFECTS

2. INTRODUCTION Visual field : 3D area of a subject’s surroundings that can be seen at a time around a point of fixation. Traquair : “Island of vision surrounded by a sea of darkness”

3. The normal extent of vision 60°superiorly . 60°nasally . 75°inferiorly . 100° temporally .

4. VF divided into central and peripheral field Central field- area from fixation to a circle 30 - physiologic blind spot on temporal side Peripheral field- rest of area

5. Scotoma : Area of depressed or lost vision surrounded by area of normal vision . - Positive & negative - Absolute & Relative

6. COMMON CAUSES OF VISUAL FIELD DEFECT Central field loss Optic neuropathy Macular degeneration Macular hole Cone dystrophies

7. Peripheral field loss Glaucoma Retinal detachment Retinitis pigmentosa Chorioretinitis

8. Visual Field Assessment Screening test Confrontation method Quantitative methods Perimetry

9. Advantages Localize the site of the lesion by mapping the visual field deficit by finger confrontation Quantitative visual field the perimeters provide a sensitive means of detecting scotomas in the visual field. They are exceedingly useful for serial assessment of visual function in chronic diseases such as glaucoma

10. INTERPRETATIONS Scotoma in one eye- lesion in either

11. Retinal diseases When photoreceptors affected Corresponding scotoma more loss of VF for blue than red When ganglion cell layer/nerve fibre layer affected Does not correspond to lesion More loss of VF for red than blue

12. Temporal bundle lesion Nasal defect Arcuate in shape Nasal bundle lesion Temporal defect Fan shaped

13. Damage to macula C entral scotoma

14. Optic nerve lesion Central or centrocecal scotoma Field defects more marked to red VF normal in early papilloedema Enlargement of blind spot in late papilloedema Altitudinal scotoma - ishaemic optic neuropathy

15. Glaucoma Damage to nerve fibres in optic disc Arcuate fibres most prone to damage Macular fibres most resistant

16. Glaucomatous field defects Isopter contraction Baring of blind spot Small wing-shaped paracentral scotoma Siedel’s scotoma Arcuate or bjerum’s scotoma Ring or double arcuate scotoma Roenne’s central nasal step

17. Key points Paracentral scotoma Roenne nasal step Paracentral scotoma widens, new scotoma forms, they coalasce  arching shape between the nasal horizontal meridian and the blind spot Affect both upper &lower regions  Ring- scotoma

18. Advanced glaucomatous field defects Tubular vision Temporal island of vision

19. Defect identical in other neuropathies- differentiated by history & examination - VF defects before loss of vision - Colour blindness typically blue-yellow - Ophthalmoscopic appearance of disc - Tonometry