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Neural selectivity of orientation is a fundamental property of visual system. We aim to investigate whether and how the orientation selectivity changes in amblyopia.Seventeen patients with amblyopia (27.1 ± 7.1 years) and 18 healthy participants (25.1 ± 2.7 years) took part in this study. They were asked to continuously detect vertical gratings embedded in a stream of randomly oriented gratings. Using a technique of subspace reverse correlation, the orientation-time perceptive field (PF) for the atypical grating detection task was derived for each participant. Detailed comparisons were made between the PFs measured with the amblyopic and healthy eyes.The PF of the amblyopic eyes showed significant differences in orientation and time domain compared with that of the normal eyes (cluster-based permutation test, ps0.05), with broader bandwidth of orientation tuning (31.41 ± 10.59 degrees [mean ± SD] vs. 24.76 ± 6.85 degrees, P = 0.039) and delayed temporal dynamics (483 ± 68 ms vs. 425 ± 58 ms, P = 0.015). None of the altered PF properties correlated with the contrast sensitivity at 1 cycle per degree (c/deg) in amblyopia. No difference in PFs between the dominant and non-dominant eyes in the healthy group was found.The altered orientation-time PF to the low spatial frequency and high contrast stimuli suggests amblyopes had coarser orientation selectivity and prolonged reaction time. The broader orientation tuning probably reflects the abnormal lateral interaction in the primary visual cortex, whereas the temporal delay might indicate a high level deficit.

Aims To determine the influence of single-vision lenses (SVLs) and progressive addition lenses (PALs) on the near vision posture of myopic children based on their near phoria. Methods Sixty-two myopic children were assigned to wear SVLs followed by PALs. Eighteen children were esophoric (greater than +1), 18 were orthophoric (−1 to 1) and 26 were exophoric (less than −1) at near. Reading distance, head tilt and ocular gaze angles were measured using an electromagnetic system after adaptation to each lens type. Results The lens type did not influence reading distance or head tilt angle (p>0.05 for both), but ocular gaze angle decreased significantly with the PALs (F=9.25, p=0.004). With the PALs, exophoric children exhibited significantly increased head tilt angle (p=0.003) and reduced ocular gaze angle (p=0.004) compared with esophoric children. Near non-exophoric children exhibited similar eye and head postures when wearing SVLs and PALs, whereas exophoric children exhibited reduced ocular gaze angle (t=−3.18, p=0.04) with PALs compared with SVLs. Using PALs for reading, the mean addition power employed by esophoric children was significantly greater than exophoric children (p=0.04). Conclusions The lens type and the near phoria state affected near vision posture. During reading, myopic esophoric children used a lower portion of their PALs compared with exophoric children, resulting in greater addition power. These results may partially explain why myopic children with near esophoria exhibited superior treatment effects in myopia control trials using PALs.

Purpose To study the repeatability and reproducibility of corneal power measurements obtained with a new corneal topographer (Keratograph 4) and assess their agreement with those obtained by a rotating Scheimpflug camera (Pentacam HR) and an automated keratometer (IOLMaster). Setting Eye Hospital, Wenzhou Medical University, Wenzhou, China. Design Observational cross-sectional study. Methods One eye of normal subjects was measured 3 times using all devices. Another operator performed an additional 3 consecutive scans using the corneal topographer. One week later, the first operator repeated the corneal power measurements using the corneal topographer. Parameters were flat meridian power, steep meridian power, average power, J0, and J45. The repeatability and reproducibility of measurements were assessed by the within-subject standard deviation (Sw), repeatability (2.77 Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Agreement between devices was assessed using 95% limits of agreement (LoA). Results Intraoperator repeatability and interoperator and intersession reproducibility of all measured parameters showed a CoV of less than 0.3%, a 2.77 Sw of 0.32 diopter or less, and an ICC of more than 0.97. No significant differences in the parameters were noted between the corneal topographer and Scheimpflug camera. Statistically significant differences existed between the parameters analyzed by the corneal topographer and the automated keratometer, except J45. The mean differences between the corneal topographer and the other 2 devices were small, and the 95% LoA were narrow for all measurements. Conclusion The new corneal topographer had excellent reliability and high agreement with the other 2 devices in corneal power measurements in normal subjects. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.