Comparison of Rates of Functional Loss Using Binocular and Monocular Visual Fields

Abstract

Purpose: : To compare rates of visual field change between monocular and binocular visual fields.

Methods: : This observational cohort study included glaucomatous patients, glaucoma suspects and ocular hypertensives recruited from the Diagnostic Innovations in Glaucoma Study (DIGS) and African Descent and Glaucoma Evaluation Study (ADAGES). Included eyes had to have a minimum of 5 pairs of visual fields with a minimum follow-up period of 5 years. Threshold sensitivities of the binocular visual field were obtained by the square root of the summed squares of the threshold sensitivities of the two monocular visual fields. Mean sensitivities were calculated for the monocular and binocular visual fields of each patient. Rates of change were calculated using ordinary least squares linear regression.

Results: : The mean age was 67.9 years (± 12.4), the mean number of binocular visual fields tests was 9.6 (± 3.2) and the mean follow-up period was 7.7 years (± 2.0). At baseline, 309 patients had glaucoma, 166 were glaucoma suspects, and 127 were ocular hypertensives. There was no significant difference in mean rates of visual field change between the right and the left eyes (-0.17dB/year vs. -0.18dB/year, p = 0.36). The mean rate of change using the binocular visual field was -0.10dB/year, which was significantly slower than mean rates of change obtained for the right and left eyes (p<0.001 for both comparisons). A slope faster than -1 dB/year was found in 7.31% of the right visual fields, 6.48% of the left visual fields and in 1% of the binocular visual fields.

Conclusions: : Rates of functional loss obtained using integrated binocular visual fields were slower than those obtained using monocular visual fields. It may be important to consider the rate of binocular vision loss when assessing the likelihood of visual impairment in glaucoma.

Keywords: visual fields • binocular vision/stereopsis