“I’m really blind without my glasses.”
Everyday several people come into my office saying those words. What they mean is that they are very nearsighted or myopic. In fact about 41% of the US population (2004 data, ages 12-54) have some degree of myopia. Eye doctors quantify myopia and all other types of prescriptions in units called diopters (D). A diopter is simply a measurement that indicates the degree to which an optical system bends light. Most forms of myopia may be classified into three different categories:
Low myopia: -0.25D to -3.00D
Medium myopia: -3.00D to -6.00D
High myopia: -6.00D and greater
We correct myopia with glasses, contacts, or sometimes procedures like LASIK. For low and medium amounts this is typically the end of the story. However, with high myopia there are some other concerns beyond getting the right prescription. Most people with this type have high prescriptions due to longer axial lengths in the eye. The axial length is the distance from the very tip of the cornea the deepest tissue layers in the back of the eye. This puts a special type of tension on the retina, and statistically gives the patient a higher risk of developing a retinal detachment. That is when the retina pops off it’s supporting basement structures and can lead to severe vision loss.
What do we do about this? Unfortunately there is no way to completely prevent a retinal detachment from happening. However, we can help minimize the risks. Blows to the head are especially risky for high myopes. The sudden shock can cause the already threatened retina to cross a tipping point and detach. Two weeks ago I saw a girl with a -8.00 prescription. She hit her head ice skating and wisely came in to be examined (thankfully she was okay). One can’t live in a padded cage, but it’s important that people with these prescription be vigilant about protecting their head and eyes. If you wear -7.00 glasses then boxing may not be a good hobby. Patients with high myopia must immediately let their doctor know if they ever see flashes of light, experience any changes in their floaters, see “curtains” coming down, or any other odd visual occurrences. Both Dr. Bazan and I believe that it’s important for everyone to get an annual dilated exam. For high myopes, this is not only important – it’s critical. We do a very thorough dilation exam to ensure that the retina is healthy and that there are no signs of any impending detachments. Speed is the name of the game if a detachment is detected. There are a variety of procedures used to heal the retina based on the type and location of the detachment. An eye doctor will ensure that these procedure are done inside an appropriate time frame. With proper care the lasting effects of a retinal detachment can be very minimal.
I will include a special point for high myopes who have had LASIK or are considering LASIK. It’s true that post-LASIK you effectively have no prescription. However, the laser simply compensates for exceptionally long eyes by altering the curves of the cornea. The axial length of the eye never changes. LASIK is a fantastic option for many of these patients and their vision. It does not change the important of being dilated annually or lower the risk of a detachment.
Feel free to contact me if you have questions about high myopia, retinal detachments, or any other eye issues.
Spencer Ritenour, O.D.