ABSTRACT
AIM: To evaluate the effect of low-degree astigmatism on objective visual quality through the Optical Quality Analysis System (OQAS). METHODS: This study enrolled 46 participants (aged 23 to 30y, 90 eyes) with normal or corrected-to-normal vision. The cylindrical lenses (0, 0.5, 0.75, 1.0, and 1.25 D) were placed at the axial direction (180°, 45°, 90°, and 135°) in front of the eyes with the best correction to form 16 types of regular low-degree astigmatism. OQAS was used to detect the objective visual quality, recorded as the objective scattering index (OSI), OQAS values at contrasts of 100%, 20%, and 9% predictive visual acuity (OV100%, OV20%, and OV9%), modulation transfer function cut-off (MTFcut-off) and Strehl ratio (SR). The mixed effect linear model was used to compare objective visual quality differences between groups and examine associations between astigmatic magnitude and objective visual quality parameters. RESULTS: Apparent negative relationships between the magnitude of low astigmatism and objective visual quality were observed. The increase of OSI per degree of astigmatism at 180°, 45°, 90°, and 135° axis were 0.38 (95%CI: 0.35, 0.42), 0.50 (95%CI: 0.46, 0.53), 0.49 (95%CI: 0.45, 0.54) and 0.37 (95%CI: 0.34, 0.41), respectively. The decrease of MTFcut-off per degree of astigmatism at 180°, 45°, 90°, and 135° axis were -10.30 (95%CI: -11.43, -9.16), -12.73 (95%CI: -13.62, -11.86), -12.75 (95%CI: -13.79, -11.70), and -9.97 (95%CI: -10.92, -9.03), respectively. At the same astigmatism degree, OSI at 45° and 90° axis were higher than that at 0° and 135° axis, while MTFcut-off were lower. CONCLUSION: Low astigmatism of only 0.50 D can significantly reduce the objective visual quality.
ABSTRACT
AIM: To investigate the safety and efficacy of sticky silicone oil (SSO) removal using a 22-gauge vein detained needle and inner limiting membrane (ILM) wrap-and-peel technique. METHODS: This retrospective consecutive case series reviewed the records of patients with a history of retinal detachment who had received silicone oil and perfluorocarbon liquid (PFCL) as intraocular tamponades. Patients were included in the analysis if they exhibited SSO remnants during silicone oil removal. The aspiration of most of the SSO remnants was performed by a 22-gauge vein detained needle. The small amounts of droplets adhered to the macula and epi-macular membrane were subsequently removed by the ILM warp-and-peel technique. The anatomical and functional outcomes, and postoperative complications were recorded. In vitro experiments were performed to simulate the formation of SSO remnants in four groups. RESULTS: Of 711 patients who underwent silicone oil removal during the study period, 9 patients exhibited SSO remnants and underwent follow-up for at least 3mo. Seven eyes (78%) underwent the ILM wrap-and-peel technique to completely remove small droplets of SSO that were glued to the macula and epi-macular membrane. No obvious complications occurred. Postoperative optical coherence tomography revealed normal retinal structure in all patients. In vitro analyses showed that balanced salt solution and prolonged vibration (for 1wk) had the strongest effects on silicone oil and PFCL compound opacities. CONCLUSION: SSO remnants could be removed in an intact manner and without complications, using a vein detained needle-assisted and ILM wrap-and-peel technique. The findings suggest that PFCL and infusion fluid should be completely removed before silicone oil injection to prevent SSO formation.
ABSTRACT
OBJECTIVE: The guinea pig becomes an important model for studies on myopia, but little is known about its visual performance. In this study, grating acuity was measured using a custom-built automated device to track optomotor responses. METHODS: To record head nystagmus, guinea pigs were individually placed in the center of a rotating drum of 130 cm diameter. The drum was covered inside with square wave gratings of adjustable fundamental spatial frequencies and contrast. The turning movements of the head were tracked using custom-written video software that detected two little white spots painted on a small black piece of cardboard that was attached to the guinea pig's head. Angular head speed was determined from the positions of the two white spots with respect to each other over time, and the ratio of angular head speed to drum speed was determined (the "gain"). In 11 guinea pigs of the same age, but with different refractive states (+9.7 to -15.0 D), responses to spatial frequencies of 0.6 and 2.4 cyc/deg were tested. Furthermore, 17 guinea pigs were tested which had similar refractive states but were different in age (1 to 3 months old). Finally, the effects of different grating contrasts were studied (25%, 50% and 100% contrast respectively) and the effects of different stripe luminances (10, 30, and 350 cd/m(2) respectively). RESULTS: The optomotor response could be used to measure vision in one eye only even if both eyes opened. The optomotor gain was affected by refractive error. Younger animals (one month old) had lower optomotor gain than older ones (0.61 ± 0.2 in one-month, 0.77 ± 0.13 in two-month and 0.80 ± 0.11 in three-month old). For a spatial frequency of 0.6 cyc/deg, the effects of stripe contrast were tested in two months old guinea pigs. At an average stripe luminance of 30 cd/m(2), the optomotor gain dropped from 0.95 ± 0.20 at maximal contrast, to 0.94 ± 0.16 at 50% contrast, and 0.70 ± 0.10 at 25% contrast. At three different luminances, gains were 0.81 ± 0.25 (10 cd/m(2)), 0.95 ± 0.20 (30 cd/m(2)), and 0.80 ± 0.09 (350 cd/m(2)), measured with gratings of 100% contrast, respectively. CONCLUSIONS: Myopic guinea pigs have reduced grating acuity compared to hyperopic ones. The optomotor gain increases with age. For a given grating contrast, the highest optomotor gains are obtained at the highest luminance of 30 cd/m(2). In summary, spatial vision in guinea pig declines with the magnitude of myopia, and increases with luminance and age.
