Genest Reno, Chandrashekar Naveen, Irving Elizabeth
Mechanical and Mechatronics Engineering Department, University of Waterloo, Ontario, Canada.
Acta Bioeng Biomech. 2012;14(2):3-8.
Myopia is characterized by an increase in axial length of the eye, but the reasons for the axial elongation are still unknown. Higher intraocular pressure (IOP) has been associated with myopia and could be involved in eye enlargement. The purpose of this study was to investigate the effect of intraocular pressure on the geometry of the chick eye and to investigate whether an increase in IOP could cause the elongation of the eye. The IOP of ten 7-day old chick eyes was raised by injecting fluid into the eyes and the resulting deformation of the eyes was measured using digital cameras. In-vitro pressure-volume curves were obtained. The axial and equatorial strains (deformation normalized to the original dimension) were calculated. Our results showed that IOP increased exponentially with increasing injected volume. About 25 D myopia could be induced by the axial elongation created with an increase in IOP by 100 mmHg. As pressure increased from 0 to 140 mmHg, the chick eye elongated in the axial direction and initially contracted in the equatorial direction. The natural tendency of chick eyes is to elongate as IOP increases and this suggests that from a mechanical perspective IOP could play a role in myopia onset and progression. The results also suggest that oblate eyes might have higher risk of developing myopia.
近视的特征是眼轴长度增加，但眼轴伸长的原因仍不清楚。较高的眼压（IOP）与近视有关，可能参与眼球增大。本研究的目的是研究眼压对雏鸡眼睛几何形状的影响，并研究眼压升高是否会导致眼球伸长。通过向十只7日龄雏鸡眼睛内注射液体来升高眼压，并使用数码相机测量由此产生的眼睛变形。获得了体外压力-容积曲线。计算了轴向和赤道应变（变形相对于原始尺寸进行归一化）。我们的结果表明，眼压随注射量的增加呈指数增长。眼压升高100 mmHg所导致的眼轴伸长可诱发约25 D的近视。当压力从0增加到140 mmHg时，雏鸡眼睛在轴向伸长，在赤道方向最初收缩。随着眼压升高，雏鸡眼睛自然倾向于伸长，这表明从力学角度来看，眼压可能在近视的发生和发展中起作用。结果还表明，扁球形眼睛可能有更高的患近视风险。
