Posterior lenticonus/lentiglobus is caused by thinning of the central posterior capsule. This thinning initially causes an “oil droplet” appearance on red reflex examination. With time, as the outpouching of the lens progresses, the cortical fibers stretch and gradually opacify. This process can take many years, but if the capsule tears, rapid total opacification of the lens can occur (Fig 21-4).
Posterior lenticonus opacities are almost always unilateral, and the affected eye is equal in size to the unaffected eye. These opacities are not typically inherited, and although the weakness in the posterior capsule may be congenital, the cataract usually does not form until later and therefore behaves like an acquired cataract. Visual prognosis after surgery can be favorable.