Clinical Characteristics And Assessment Of Nystagmus Waveforms In Congenital Stationary Night Blindness And Aland Island Disease

摘要

Purpose: : To investigate clinical characteristics and assess nystagmus waveforms in congenital stationary night blindness (CSNB) and Aland Island (AI) disease; conditions that present with negative scotopic ERGs and have been found to be allelic. Methods: : A retrospective analysis of clinical data and eye movement recordings (Eyelink II, 500Hz) collated from 8 CSNB and 4 AI patients. Patients were included based on clinical findings and the presence of a negative scotopic electroretinogram (ERG). Patients classified with Aland Island disease had iris transillumination. Nystagmus has been classified based upon the 12 waveforms for infantile nystagmus described by Della??osso et al. Results: : Scotopic ERGs in both groups were negative, with an absent or significantly reduced b-wave and a-reduced amplitude of b/a wave ratio. Iris transillumination, typical for AI, was present in all AI patients. For 6 CSNB and 2 AI patients, a positive family history of nystagmus affecting only male relatives, consistent with X-linked inheritance. Variation in best corrected binocular visual acuity (BCVA) was recorded for both groups with mean logMAR BCVA of 0.41 (?± 0.22) in CSNB and 0.44 (?±0.22) in AI. Four patients with CSNB were myopic. Abnormal head posture was observed in 6 of the 8 CSNB patients but not in the AI group. Two patients in each group had strabismus. All patients had nystagmus that was conjugate but varied in other characteristics regardless of diagnosis. Eye movement recordings showed the plane of nystagmus in primary position was oblique or horizontal and waveforms were classified as jerk, jerk with extended foveation, pseudo jerk, bidirectional jerk, pendular with foveating saccades and pseudo pendular. For jerk waveforms the slow phases were all of increasing velocity. Two patients (1 CSNB and 1 AI) presented with manifest latent nystagmus with decelerating slow phases. Conclusions: : Clinical characteristics of CSNB and AI are widely variable in terms of best corrected VA, the presence of strabismus and, in particular, nystagmus waveform characteristics. Abnormal head posture and presence of myopia appear to define the two groups, whilst negative scotopic ERG and the presence of nystagmus are consistent parameters across all patients.