My grandma wears spectacles for her life long and now her eye sight back to norm!
Question:
My grandma wears spectacles for her life long and now her eye sight back to normal...strange?
Answers:
"Second Sight" is a common phenomenon as we age. It is caused by a combination of natural changes within the eye.
When we are young the natural crystalline lens within the eye changes shape to allow us to focus on objects near. This is called accommodation. In its natural relaxed state the normal eye is focused to infinity – all objects beyond about 20 feet with the same clarity. To see objects closer than about 20 feet, our eyes need to accommodate.
As we become older, the crystalline lens becomes stiff and less able to change shape. This is called presbyopia and normally becomes problematic at around age 40. Presbyopia is when reading glasses or bifocals are needed to see objects close. Distance vision beyond 20 feet is commonly unaffected. Your grandmother is undoubtedly presbyopic.
Another natural occurrence is a cataract. Age-related cataract (Nuclear Sclerosis) is when the crystalline lens becomes cloudy. A first step in the process of an age-related cataract is slight thickening of the central portion of the crystalline lens. This thickening changes the refractive power of the lens, making the person more myopic (nearsighted, shortsighted).
There are two ways to describe myopia. One is that you cannot see distant objects very well. The other is that you can see near objects quite well. My bet is that your grandmother is seeing an improvement in her near vision, but a slight degradation in her distance vision.
As your presbyopic grandmother is becoming more myopic because of the beginning of a cataract, she is more able to see near objects because here eye in a natural relaxed unaccommodating state is focused or objects near.
An additional contributor to Second Sight is that as we become older our pupils tend to become smaller. The smaller the pupil, the greater the depth of focus. Depth of focus is the range from the patient where vision is clear (i.e. 3-5 feet away in focus). This optical process is exactly like a camera. If the iris of the camera is small, objects near and far are in focus. If the iris of the camera is large, only objects at one distance are in focus.
Your grandmother may have been hyperopic (farsighted, longsighted) before the process of presbyopia and age-related cataract. Progressive myopia from the developing cataract will counter the effects of hyperopia.
A comprehensive examination by a competent eye doctor will be able to tell your grandmother exactly why her vision is changing, but it is very probably because she is developing a cataract that is causing her to become myopic and reducing the effects of presbyopia.
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