A prospective longitudinal study of retinal structure and function in achromatopsia.

PURPOSE: To longitudinally characterize retinal structure and function in achromatopsia (ACHM) in preparation for clinical gene therapy trials. METHODS: Thirty-eight molecularly confirmed ACHM subjects underwent serial assessments, including spectral domain optical coherence tomography (SD-OCT), microperimetry, and fundus autofluorescence (FAF). Foveal structure on SD-OCT was graded and compared for evidence of progression, along with serial measurements of foveal total retinal thickness (FTRT) and outer nuclear layer (ONL) thickness. Fundus autofluorescence patterns were characterized and compared over time. RESULTS: Mean follow-up was 19.5 months (age range at baseline, 6-52 years). Only 2 (5%) of 37 subjects demonstrated change in serial foveal SD-OCT scans. There was no statistically significant change over time in FTRT (P = 0.83), ONL thickness (P = 0.27), hyporeflective zone diameter (P = 0.42), visual acuity (P = 0.89), contrast sensitivity (P = 0.22), mean retinal sensitivity (P = 0.84), and fixation stability (P = 0.58). Three distinct FAF patterns were observed (n = 30): central increased FAF (n = 4), normal FAF (n = 11), and well-demarcated reduced FAF (n = 15); with the latter group displaying a slow increase in the area of reduced FAF of 0.03 mm(2) over 19.3 months (P = 0.002). CONCLUSIONS: Previously published cross-sectional studies have described conflicting findings with respect to the age-dependency of progression. This study, which constitutes the largest and longest prospective longitudinal study of ACHM to date, suggests that although ACHM may be progressive, any such progression is slow and subtle in most patients, and does not correlate with age or genotype. We also describe the first serial assessment of FAF, which is highly variable between individuals, even of similar age and genotype.

Dual tasking and balance in those with central and peripheral vision loss.

PURPOSE: To investigate the effects of a secondary task on standing balance in patients with glaucoma or AMD compared with age-similar control subjects. METHODS: Twelve AMD, 12 glaucoma, and 12 control participants underwent posturography under two standing conditions (eyes open on a firm or foam-rubber surface) and two tasks: quiet standing and undertaking a mental arithmetic task. Center of foot-pressure average displacement (root mean square [RMS]; in millimeters) was calculated. RESULTS: The mean (SD) age of the participants in each group was as follows: controls 66.2 (6.4) years, glaucoma 69.2 (4.3) years, and AMD 72.2 (5.3) years. There were significant differences in RMS between controls and AMD patients when undertaking the mental arithmetic task standing on the firm surface (mean difference [SE]: 2.8 [0.8] mm, P = 0.005). There were significant differences between controls and AMD patients when undertaking the mental arithmetic task on the foam surface, with the difference between controls and glaucoma patients approaching significance (mean difference [SE]: control versus AMD = 3.1 [0.9] mm, P = 0.005; control versus glaucoma = 2.2 [0.9] mm, P = 0.06). CONCLUSIONS: Postural instability increases with the addition of a secondary task in older persons, which may put them at greater risk of falls. Patients with central losses exhibit greater instability with the addition of a secondary task, particularly during somatosensory perturbations. The negative effects of secondary tasks on balance control in those with peripheral visual losses become more apparent under somatosensory perturbations.

Balance control in glaucoma.

PURPOSE: To examine postural stability in glaucoma patients and subjects with no ocular disease. METHODS: Twenty-four glaucoma (G) and 24 control (C) subjects participated (mean age [SD] G: 65.9 [5.5] years; C: 68.3 [5.2] years). Postural stability was measured using a force-balance platform under four conditions: eyes open/closed standing on a firm surface and eyes open/closed on a foam surface. Average magnitude of center of foot pressure displacement (root mean square [RMS]) was calculated in the anteroposterior (AP) direction. The Romberg Quotient (RQ) was used to evaluate the visual contribution to balance. The difference in sway between firm and foam standing evaluated the relative somatosensory contribution to balance. The binocular mean deviation (BinMD) score was calculated from Humphrey 24-2 SITA strategy tests. RESULTS: Glaucoma patients had a lower visual contribution to sway (AP RQ, G = 1.65 [0.44]; AP RQ, C = 2.25 [0.53], P = 0.0001), and higher relative somatosensory contribution to sway (change in AP RMS EYES open firm to foam standing: G = 4.12 [1.85] mm, C = 2.22 [2.04] mm, P = 0.002). BinMD was a significant predictor of balance (AP RQ versus BinMD ß-coefficient = 0.58, P = 0.0001; change in AP RMS [eyes open "firm" to "foam"] versus BinMD ß-coefficient = -0.35, P = 0.02). CONCLUSIONS: Glaucoma patients display differences in their visual and somatosensory contributions to quiet standing balance compared with control subjects, associated with the degree of binocular visual field loss. This suggests that balance control may be compromised in this patient group.