Earliest sign in visual field suggestive of glaucoma:: (A) Isopter contraction, (B) Baring of blind spot, (C) Seidels scotoma, (D) Arcuate scotoma
Answer is A. Isopter contraction is earliest sign of glaucoma though it is not very specific. High Yield points regarding visual fields Isopters : degrees of visual field. A normal visual field extends approximately 100deg temporally (laterally), 60deg (nasally), 60deg (superiorly), and 70deg (inferiorly). A physiologic scotoma (a blind spot) exists at 15deg temporally where the optic nerve leaves the eye.. Earliest field defect in glaucoma is isopter contraction f/b baring of blind spot. Earliest specific defect is paracentral scotoma > Seidel scotoma. NOTE- in PAOG there is no expansion of blind spot. other conditions where blind spot expansion is seen are - Papilledema Optic nerve hypoplasia.