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 300 - 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 Optic nerve Retina
- 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 Central 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
- 18. 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
- 19. Advanced glaucomatous field defects • Tubular vision • Temporal island of vision
- 20. • 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