Hi everyone ! So this is a short post on the Second Sight or the Myopic Shift seen in Cataract.
So in people who have a hypermetropic / presbyopic power , tend to experience a reduction in their refractive errors when Cataract starts to develop. This is called Myopic Shift or Second sight.
This occurs most commonly in nuclear cataracts. Now why this occurs is , the lens in early stages of Cataract undergoes sclerosis. That increases the Power of the lens ( this increases the refractive index).
Thus it makes the lens slightly more Powerful , or Convex. Due to this it acts as a correction for Hyperopia/ Presbyopia (Where the error was due to a weaker lens. )
This transient Myopic nature of the eye is called the Myopic Shift.
It does go away when the Cataract progresses as the sclerosis begins to reduce refractive surface in the lens.
Hope this helped! Stay awesome !
Happy Studying :)