Latest posts
-
Axial length and corneal curvature, which affects fundus magnification more?
In the previous post, I hypothesised that a fundus-based DL model would have difficulty predicting the refractive component of ametropia, i.e. that part of refractive error attributable to corneal/ lens curvature. This is due not only to the absence of biologically meaningful features associated with corneal/ lens curvature in fundus images, but also because variation in corneal/ lens curvature gives rise to relatively small variation in fundus magnification. There is little information about corneal/ lens curvature in fundus images, so to speak. I discuss below how I arrived at this conclusion.
-
Why care about differentiating axial from refractive ametropia?
Refractive error (ametropia thereafter) arises from a mismatch between axial length (AL) and the equivalent power of the refractive components of the eye, i.e. cornea, crystalline lens. Such mismatch is often (predominantly) axial in nature. AL is typically high (>24mm as a fairly useful rule of thumb) in myopes. Importantly, axial elongation is mainly attributable to changes in vitreous chamber depth. This explains why myopia is associated with clinical features in the posterior segment of the eye, e.g. peripapillary atrophy (PPA), tesselation.
subscribe via RSS