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Peripheral astigmatism in emmetropic eyes
Author(s) -
Gustafsson Jörgen,
Terenius Erik,
Buchheister Jan,
Unsbo Peter
Publication year - 2001
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.2001.00606.x
Subject(s) - emmetropia , astigmatism , central scotoma , optics , blind spot , fixation (population genetics) , optometry , refraction , refractive error , physics , ophthalmology , medicine , visual acuity , population , environmental health
Summary The long‐term aim of the work introduced here is to investigate the influence of off‐axis aberrations on human vision, especially for subjects with a large central scotoma. The latter use their peripheral vision in spite of its poor off‐axis optical quality, and a correction of the off‐axis aberrations might be of great assistance. The eccentric fixation angles used by these subjects can be up to 20–30°. In this initial study we have measured oblique astigmatism, the major off‐axis aberration, in 20 emmetropic eyes in 10° steps out to 60° nasally and temporally using a ‘double pass’ setup. The results show very large individual differences and the oblique astigmatism also varies from nasal to temporal side. In an off‐axis measurement angle of 30° the astigmatism varied between subjects from 1 to 7‐D, with a mean astigmatism of about 4‐D on the nasal side and about 1.5‐D lower on the temporal side. At 60° temporally, the mean astigmatism was 7‐D. At 60° nasally, all subjects had astigmatism larger than 8‐D and the mean astigmatism was 11‐D. The results indicate that any attempt to correct the off axis astigmatism in an eye with central scotoma cannot be based on central refraction; instead, individual measurements are necessary.