Yoon-Hee Chang

The effects of interocular differences in retinal illuminance on vision and binocularity

BackgroundIt is known that binocular function is affected by interocular differences in retinal image size, shape, clarity, and illumination. The present study was performed to systematically examine the effects of interocular differences in retinal illuminance on monocular visual acuity, fusion, and stereopsis.MethodsFifty adults with normal binocularity and a best-corrected visual acuity of 20/20 or better were enrolled. We examined best-corrected visual acuity, fusion, and stereoacuity as monocular retinal illuminance was gradually reduced by increasing neutral density filters from 0.2 neutral density (ND; 63% transmission) to 3.0 ND (0.1% transmission) in increments of 0.2 ND. We measured the smallest size of fusion slide by major amblyoscope, and evaluated stereoacuity with the Titmus test and the Lang test.ResultsThe best-corrected visual acuity began to decrease significantly when the value of the neutral density filter reached 2.0 ND (1% transmission; p<0.01). The level of fusion decreased significantly when monocular retinal illuminance was reduced to 2.0 ND (p<0.01). Stereoacuity began to decline significantly when the value of the neutral density filter was 1.4 ND (4% transmission) with the Titmus test and 1.6 ND (2.5% transmission) with the Lang test.ConclusionsA binocularly conducted Titmus test was the most sensitive to the presence of monocularly induced retinal illuminance deterioration.

Outcomes of 6 Hour Part-time Occlusion Treatment Combined with Near Activities for Unilateral Amblyopia

Purpose To evaluate the outcome of the part-time occlusion therapy with near activities in monocular amblyopic patients according to gender, age, severity of amblyopia, and the cause of amblyopia. Methods Fifty eight patients who were prescribed part-time occlusion therapy with near activity from July 1998 to October 2004, were included in this retrospective study. All patients were divided into groups by gender, age, severity of amblyopia, and the cause of amblyopia. Main outcome measures were best corrected visual acuity, line improvement, and success rate. Results At the end of patch therapy, visual acuity improved from baseline by an average of 3.2±2.5 lines (0.33±0.26 log MAR), and follow-up period was 19.71±14.61 months (1.62±1.20 years). At the last follow-up, visual acuity improved from baseline by an average of 3.7±2.4 lines (0.38±0.26 log MAR), and follow-up period was 37.41±25.83 months (3.08±2.12 years). The success rate was 86% (50 patients) at the end of patch therapy. In 44 patients out of 50 patients (88%), the visual acuity was maintained. While 43 patients out of 47 patients who were less than 7 years old (91%) achieved success, 7 patients out of 11 patients 7 years or older (64%) achieved success (p=0.035). Conclusions Six-hour part-time occlusion treatment combined with near activities appears to be favorable in treating 58 children during follow-up of mean 3.08 years. The significant factor was the age at initial treatment.

Calcium uptake and release through sarcoplasmic reticulum in the inferior oblique muscles of patients with inferior oblique overaction.

We characterized and compared the characteristics of Ca2+ movements through the sarcoplasmic reticulum of inferior oblique muscles in the various conditions including primary inferior oblique overaction (IOOA), secondary IOOA, and controls, so as to further understand the pathogenesis of primary IOOA. Of 15 specimens obtained through inferior oblique myectomy, six were from primary IOOA, 6 from secondary IOOA, and the remaining 3 were controls from enucleated eyes. Ryanodine binding assays were performed, and Ca2+ uptake rates, calsequestrins and SERCA levels were determined. Ryanodine bindings and sarcoplasmic reticulum Ca2+ uptake rates were significantly decreased in primary IOOA (p<0.05). Western blot analysis conducted to quantify calsequestrins and SERCA, found no significant difference between primary IOOA, secondary IOOA, and the controls. Increased intracellular Ca2+ concentration due to reduced sarcoplasmic reticulum Ca2+ uptake may play a role in primary IOOA.