The model now includes the positions of the optic disc and fovea. These two locations have a fixed distance from one another in retinal degrees, and subtend a nearly constant 16.6 degrees of visual angle, even with changes in posterior chamber size. The change in posterior chamber size, however, moves the optic disc further away from the posterior apex of the vitreous chamber. The effect of this is to move the fovea closer to the optical axis as the eye lengthens with increasing myopia. This causes the alpha angle to shrink in good agreement with empirical measurements.
The model now includes the positions of the optic disc and fovea. These two locations have a fixed distance from one another in retinal degrees, and subtend a nearly constant 16.6 degrees of visual angle, even with changes in posterior chamber size. The change in posterior chamber size, however, moves the optic disc further away from the posterior apex of the vitreous chamber. The effect of this is to move the fovea closer to the optical axis as the eye lengthens with increasing myopia. This causes the alpha angle to shrink in good agreement with empirical measurements.