Department of Optometry, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, Karnataka, India.
Myopia Research Lab, Prof. Brien Holden Eye Research Centre, and Brien Holden Institute of Optometry and Vision Sciences, L V Prasad Eye Institute, Hyderabad, India.
J Optom. 2022 Oct-Dec;15(4):293-298. doi: 10.1016/j.optom.2021.12.001. Epub 2021 Dec 21.
This pilot study aimed to investigate the maximum extension of foveal fixation in the horizontal direction among young adults in both emmetropes and myopes.
35 participants (28 emmetropes and 7 myopes) were included. Participants with restricted extra-ocular mobility, end gaze nystagmus, and/or any other ocular pathology were excluded. Visual acuity (VA) was used as a surrogate measure of foveal fixation. VA was determined using a staircase procedure with 8 reversals. The average of the last 5 reversals was taken as the thresholds. VA acuity was measured at different gaze eccentricities along nasal and temporal visual field meridian. The eccentricity at which VA drops significantly was taken as the maximum extent of foveal fixation. A bilinear fit regression model was used to investigate the drop in the VA in both nasal and the temporal direction.
Emmetropes can foveate up to 35 ± 2° in nasal and 40 ± 3° in temporal direction and myopes can foveate up to 38° in both nasal and temporal directions. Paired student t-test showed a significant difference in foveal fixation between nasal and temporal direction for emmetropes (P<0.001) but not in myopes (P = 0.168). An unpaired student t-test showed a significant difference in foveal fixation for nasal direction between myopes and emmetropes (P = 0.01). However, no statistically significant difference was found in foveal fixation for temporal direction between myopes and emmetropes (P = 0.792).
The eye rotation does not necessarily match with the extent of foveal fixation at extreme eye rotation. Eyes can fixate only up to 35° nasally and 40° temporally maintaing their maximum visual acuity.
本初步研究旨在探究正视眼和近视眼中，年轻人在水平方向上的最大中心注视维持范围。
共纳入 35 名参与者（28 名正视眼和 7 名近视）。排除眼球运动受限、终末眼震和/或任何其他眼部疾病的患者。视力（VA）用作中心注视的替代测量指标。采用 8 次反转的阶梯程序确定 VA。取最后 5 次反转的平均值作为阈值。在鼻侧和颞侧视野子午线的不同注视偏转角处测量 VA 敏锐度。VA 显著下降的偏转角被视为中心注视的最大维持范围。采用双线性拟合回归模型研究鼻侧和颞侧 VA 的下降情况。
正视眼在鼻侧可注视至 35°±2°，在颞侧可注视至 40°±3°，近视眼在鼻侧和颞侧均可注视至 38°。配对学生 t 检验显示，正视眼在鼻侧和颞侧的中心注视维持范围存在显著差异（P<0.001），但在近视眼中无显著差异（P=0.168）。独立样本学生 t 检验显示，近视眼和正视眼在鼻侧的中心注视维持范围存在显著差异（P=0.01）。然而，在颞侧的中心注视维持范围上，近视眼和正视眼之间无统计学差异（P=0.792）。
眼球旋转并不一定与极端眼球旋转时的中心注视维持范围相匹配。眼睛在鼻侧和颞侧的最大视觉敏锐度仅能维持在 35°和 40°。
