Stereoacuity in mild, moderate and severe glaucoma

Abstract

To determine the association between stereoacuity and severity of glaucoma. Stereoacuity was measured using the Titmus stereo test for 97 glaucoma subjects with visual acuity better than 0.3 logMAR (6/12, 20/40 Snellen) and reliable Humphrey visual fields (24-2 SITA standard). The severity of visual fields was graded with the Hodapp-Anderson-Parrish (HAP) classification and visual fields index (VFI) score and the stereoacuities for different grades were compared. Presence of a significant field defect (p < 1%) in any one of the paracentral points in 10-2 SITA standard/Macular threshold was considered as a threat to fixation. Mean ± SD age of the subjects was 57.28 ± 14.0 years. The median [inter-quartile range, (IQR)] stereoacuity of the 97 subjects was 50 (40-100) arc sec with 13 subjects having stereoacuity of >3000 arc sec. Median (IQR) stereoacuity of 97 subjects classified with HAP as mild, moderate and severe were 40 (40-40), 50 (40-60) and 60 (40-400) arc sec; similarly median (IQR) stereoacuity of the subjects classified using VFI as mild, moderate and severe were 40 (40-55), 60 (40-100) and 120 (50-3000) s of arc and the difference between groups were significant (p < 0.001). Median (IQR) stereoacuity in subjects with no threat to fixation (45) and threat to fixation in at least one eye (52) were 40 (40-60) and 70 (40-800) arc sec (p < 0.001). Decreased stereoacuity was associated with greater glaucomatous visual field loss, although it was normal with early visual field defects. Relatively moderate defects can be associated with decreased stereoacuity and it is more pronounced in the severe stages of the disease when there is a threat to fixation.