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Z. Saihan, L. Cook, S.A. Jenkins, M. Guest, F.W. Fitzke, M. Bitner–Glindzicz, A.T. Moore, A.R. Webster; Visual Function in Usher Syndrome . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1936.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the detailed clinical ophthalmic phenotype of patients with Usher syndrome in the UK. Methods: Sixty three patients affected with Usher syndrome from 54 families underwent ophthalmic examination, kinetic perimetry, electrophysiology, retinal autofluoresence imaging and optical coherence tomography (OCT). Here we report on the comparison of acuity and visual field in those with Usher type I versus type II/III. Visual field area, in degrees–squared, was measured by using in–house software on digitised V4e and II4e isopters obtained by Goldmann perimetry. Visual acuity was taken as LogMAR measurements. Results: The mean age of the total cohort was 36 years (SEM=11). LogMAR visual acuity of the better eye (±SEM) in each group was 0.47(±0.68) for Usher type 1 and 0.30(±0.64) for Usher types 2/3, corresponding to Snellen equivalents of 20/59 and 20/40 respectively. Using linear regression a stronger association between age and declining visual acuity was observed in the Usher type 1 with a positive correlation between age and LogMAR acuity (R2=0.14) than in the Usher type 2/3(R2=0.03). Acuites in the Usher I patients were generally worse than in Usher II/III when corrected for age. Using linear and quadratic regression models for the analysis of visual field area and age in Usher type 1 and type 2/3, the visual field area decreased significantly with age in Usher type 1 (R2 = 0.3) but the rate of loss was greater with age for type 2/3 patients (R2 = 0.5). This was likely due to the fact that the Usher type I patients had significantly smaller fields overall when corrected for age (P = < 0.05), but that both groups converged to a field size of only a few degrees in older patients. Conclusions: In our cohort both visual acuity and visual field size appears to be significantly worse in Usher type 1 patients than those with Usher type 2/3 when corrected for age. Field size declines inexorably with age in both groups. However, those with Usher type 2/3 did generally maintain their acuity despite increasing age. The natural history data from this study presents important information useful for counseling patients and families and in the assessment of future therapies. Further clinical differences may emerge as our cohort grows and when based on a molecular subclassification of the patients.
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