Clinical factors influencing the visual prognosis of the fellow eyes of normal tension glaucoma patients with unilateral field loss

Aim-To investigate the influence of several clinical variables on the devel opment of visual field loss in the "second eye" of patients with normal ten sion glaucoma (NTG) presenting with unilateral field loss. Methods-Patients with NTG and unilateral field lass at presentation were se lected from a cohort of 403 consecutive diagnoses of NTG. The state of the visual field "normal" or with a visual field defect was defined using the A dvanced Glaucoma Intervention Study (AGIS) template. Where available, optic disc planimetry was carried out on stereo photographs taken at presentatio n. Measurements of the topography of each of these optic discs were compare d with morphometric values from a group of normal subjects, allowing for di fferences in age and disc size. For each patient the percentage of the rela tive neuroretinal rim (NRR) area was calculated. The time taken to develop a visual field defect was related to clinical factors including age, sex, p eak and mean diurnal intraocular pressure (IOP), refraction, relative NRR a rea, and the AGIS score of the fellow eye at presentation Results-54 patients were included in the study. The median (range) follow u p time was 49.2 (11.1-116.7) months. 14 (26%) patients developed field loss in the eyes with an initially normal field. The estimate of the median tim e to field loss onset was 95.1 months. Field damage developed more rapidly in women and in patients with greater AGIS score in the contralateral eye a t the beginning of follow up ((adjusted hazard ratio, HR (95% confidence in terval, CT) 0.20 (0.04; 0.93); 1.19 (1.02; 1.41) respectively)). Little evi dence of any association was found between time to onset of field loss and each of age, refraction, and peak or mean diurnal IOP. Planimetric disc ana lysis was carried out in 33 (61%) patients, Of these 10 (30%) developed fie ld loss in the eyes with initial normal held at a median follow up of 95.1 months. After adjustment for sex and AGIS, relative NRR area was found to b e significantly related to the time of onset of field damage, the greater t he reduction in relative NRR area, the shorter the time to visual field los s (HR 0.93 (0.89; 0.99)). Conclusions-NTG patients with unilateral field loss are at high risk of dev eloping field damage in the eyes with an initially normal visual field. In this study, the visual prognosis of the eye with the normal visual field at presentation was found to be influenced by the extent of the reduction in relative NRR area together with the severity of field damage in the contral ateral eye at presentation.