One of the most commonly asked questions in an eye exam comes right after the refraction, or glasses prescription check: “What is my vision?”

Almost invariably, people know the term “20/20”. In fact, it’s a measure of pride for many people. “My doctor says I have 20/20 vision.” Or, on the other side of that same coin, having vision that is less than 20/20, say 20/400, can be a cause of great concern and anxiety. In this discussion I will describe what these terms actually mean.

To lay the foundation, let’s discuss some common terms. Visual acuity (VA) is clarity or sharpness of vision. Vision can be measured both corrected (with glasses or contact lenses) and uncorrected (without glasses or contact lenses) during the course of an eye exam. The result of an eye exam boils down to two different but related sets of numbers: your VA and your actual glasses prescription.

The notation that doctors use to measure VA is based off of a 20-foot distance. This is where the first 20...

Diabetic retinopathy is an eye condition that can affect the retina of people who have diabetes.

The retina is the light-sensitive tissue that lines the back of the eye, and it detects light that is then processed as an image by the brain. Chronically high blood sugar or large fluctuations in blood sugar can damage the blood vessels in the retina. This can result in bleeding in the retina or leakage of fluid.

Diabetic retinopathy can be divided into non-proliferative or proliferative diabetic retinopathy.

Non-proliferative diabetic retinopathy:  In the early stage of the disease, there is weakening of the blood vessels in the retina that causes out-pouching called microaneurysms. These microaneurysms can leak fluid into the retina. There can also be yellow deposits called hard exudates present in the retina from leaky vessels.

Diabetic macula edema is when the fluid leaks into the region of the retina called the macula. The macula is important for the sharp central...