These four conditions are referred to as refractive errors. Did you know that you can have 3 of these four refractive errors at the same time? The terms describing the various vision conditions can be pretty confusing, especially when you are told that you have more than one of these! Let’s break down each in turn and explain how they affect the way you see the world.
First, let’s translate these words into English. The suffix “-opia” is Greek for “of the eye”. “Myo-“ comes from the Greek for “closed” or “shut”. Myopia, or nearsightedness, occurs when an eye is larger than normal, causing it to be naturally focused up close. Reading vision is usually great without glasses but distance vision is blurred.
The prefix “Hyper-” means “above”, “higher”, or” further”. Hyperopia means “further out vision”, or farsightedness. This typically occurs when the eye is smaller than average, and causes its natural focus to be way out in the distance – too far to be clear at any distance. People with hyperopia often cannot see up close or even at medium-to-long range without glasses or contact lenses. The natural lens in young individuals can adjust for and “fight” mild and moderate degrees of hyperopia, allowing a person to see well for both distance and near. Once a person enters his/her 40s, however, the natural lens becomes less flexible and can no longer counter hyperopia. Reading becomes difficult without glasses, and soon thereafter, distance starts to blur. This is the beginning of Presbyopia.
The Greek word “presbys” means “old man”. As we all age, our natural lenses harden and lose their ability to focus up close. Presbyopia occurs in everyone, regardless of whether they are myopic, hyperopic, or do not need lenses for distance. Myopic patients have the advantage of being naturally focused for near, so as they age they still can retain reading vision without glasses, often into their 60s and beyond. But eventually, they too may end up needing reading glasses.
The last refractive error term is Astigmatism, which occurs when the front window of the eye – the cornea – is oblong or “football”-shaped, rather than circular. This creates distortion in the vision and can occur alone or together with myopia, hyperopia, or presbyopia. In fact, you can see that it is possible to have myopia or hyperopia along with astigmatism and presbyopia. Correcting astigmatism alone does not improve the other conditions, and is often achieved with glasses and contact lenses.
Fortunately, vision correction procedures such as laser cataract and lens surgery can permanently treat all four of these conditions, eliminating the need for glasses for both distance and near!