Cataract development and optical prescription

As cataracts are developing we often see a change in the optical prescription. Someone who was +4.00 in each eye might end up +3.00 by the time they are ready to have their cataracts removed. Some may declare that their vision has ‘improved’. The reality is that this is a bit of a stretch. Whilst the best correction may have become less, their vision will have become worse with the advancing cataracts. Before the cataracts developed, they may have been able to read the bottom line of the eye chart with their +4.00 glasses on. By the time they are needing cataracts done, they might only be seeing the third or fourth line up from the bottom, even though their best prescription had become less!
The reason I thought to write on this was because I had a patient come in today, saying that his vision was now better in the distance when he takes his glasses off.
He said that he has been eating wild blueberries and that he had heard they were good for the eyes, and this must be the reason why his vision had ‘improved’.
Of course the real reason is that he does have early cataracts and they must have developed further in the few months since his last examination, causing a myopic shift and subsequent feeling that his current prescription is now too strong and blurring his vision. What he perceived as an improvement in his vision is really a degradation. With his best correction, it is guaranteed that his vision will now be worse than it was with his best correct at the last examination.
So in summary, the strength of the prescribed lenses has little to do with with your best corrected visual acuity.