These cataracts are spoke-like opacities (or spokes of darkness) radiating from the periphery, or edge, of the lens towards the centre of the lens. We don’t really know what causes them.
It could be that they are a result of constant, lifelong stretching of the lens that occurs every time we attempt to focus our eyesight from the distance to near. This process is called “accommodation”. It involves a muscle inside the eye, called the ciliary body, pulling on our lens. This changes the shape of the lens, to bring what we are looking at into focus.
The constant stretching and relaxation of the lens shape stresses protein fibres within the lens. This trauma causes clefts (splits) of water to form within the lens, and the degeneration of lens proteins. Eventually, spoke-like calcifications of the lens occur.
If you have cortical cataracts, you will notice blurred vision, as well as seeing halos and streaks around lights.
Posterior subcasular cataracts
Posterior subcapsular cataracts appear like a plaque on the back surface of the lens. These cataracts develop rapidly, and can profoundly reduce vision. It is not uncommon for a patient with posterior subcapsular cataract to lose all functional vision in the affected eye within just six months.
Posterior subcapsular cataract is caused by cells inside the lens suddenly growing in a disorganized fashion. These cells migrate to the back surface of the lens, where they are known as ‘Bladder cells’ or ‘Wedl cells’. Instead of growing as translucent, thin strands, these cells grow as dense, round clumps. This gives the appearance of an opaque plaque on the back surface of the lens.