Nearwork-induced transient myopia and parental refractive error.

PURPOSE: To investigate the relationship between parental refractive error and the nearwork-induced transient myopia (NITM) characteristics of their children. METHODS: Three hundred sixty children (173 boys and 187 girls) aged 6 to 17 years were tested. Initial NITM and its decay time (DT) were assessed objectively (WAM-5500, Grand-Seiko) immediately after binocularly viewing and performing a sustained near task (5 diopters [D]) for 5 minutes, incorporating a cognitive demand with full distance refractive correction in place. The NITM was classified into three categories: low (< 0.15 D), moderate (0.15 to 0.30 D), or high (≥0.30 D), whereas its decay was classified into two categories, namely, complete or incomplete. In addition, the children were divided into three groups based on the number of myopic parents (none, one, or two) and into four groups based on the level of parental myopia (no, low, moderate, or high). RESULTS: Neither paternal nor maternal refractive error was associated with either their children's initial NITM magnitude or its DT in the myopic, emmetropic, or hyperopic groups or the combined group. No significant differences (p > 0.05) in the NITM magnitude, DT, or decay time constant were found as related to the number of myopic parents or level of parental myopia. Multiple odds ratio for incomplete decay of NITM did not change significantly (p > 0.05) with either an increase in number of myopic parents or level of parental myopia. CONCLUSIONS: There was no association between parental refractive error and their children's NITM characteristics. This suggests a primary environmental basis for the NITM characteristics in the children.

Optic disc measurements in myopia with optical coherence tomography and confocal scanning laser ophthalmoscopy.

PURPOSE: To evaluate the relationships between optic disc measurements, obtained by an optical coherence tomograph and a confocal scanning laser ophthalmoscope, and myopia. METHODS: One hundred thirty-three eyes from 133 healthy subjects with mean spherical equivalent -6.0 +/- 4.2 D (range, -13.13 to +3.25 D) were analyzed. Optic disc measurements including disc area, rim area, cup area, cup-to-disc area, and vertical and horizontal ratios were obtained with an optical coherence tomograph (StratusOCT; Carl Zeiss Meditec Inc., Dublin, CA) and a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, HRT 3; Heidelberg Engineering, GmbH, Dossenheim, Germany). The modified axial length method derived from prior published work was used to correct the OCT measurements for ocular magnification. Bland-Altman plots were used to evaluate the agreement for each optic disc parameter. Associations between optic disc area and axial length/spherical equivalent were evaluated by linear regression analysis. RESULTS: Disc area increased with the axial length/negative spherical equivalent in the HRT and the corrected OCT measurements although opposite directions of associations were found when the OCT measurements were not corrected for magnification. The difference of the corrected OCT and HRT disc area (corrected OCT disc area minus HRT disc area) was correlated with the axial length (r = 0.195, P = 0.025). When the ametropia was limited to -8.0 to +4.0 D, the correlations became insignificant in the HRT. Using the corrected OCT measurements, disc area, rim area, and cup area, cup-to-disc area, and cup-to-disc horizontal and vertical ratios were significantly larger than those measured by the HRT, with a span of 95% limits of agreement at 1.99, 1.33, and 1.86 mm(2) for the areas, 0.34, 0.53, and 0.58 for the ratios, respectively. CONCLUSIONS: While optic disc area generally increased with the axial length and myopic refraction, the HRT measurements demonstrated that optic disc size was largely independent of axial length and refractive error between -8 and +4 D. OCT may overestimate optic disc size in myopic eyes and results in poor agreement between the two instruments.