はしだ眼科クリニック

It is surprising to find the remarkable number of patients who wear their contact lenses for extended periods of time, as well as their abusive use of disposable lenses. Wearing the contact lenses for 12 hours a day is horrible enough but not the worst. I even encounter patients who wear their lenses for longer than 15 hours or until they go to bed, and they make it their everyday habit. Some are using disposable lenses for 2 straight weeks although they are only for one-day use. I have also met a patient who kept the lenses on for over a year!

In order to avoid damage to their eyes, we advise our patients to minimize the use of contact lenses and to take them off as soon as they get home at the end of the day. We also recommend them to wear glasses at least one or two days a week instead of the contact lenses (we also find it surprising that many contact lens users do not own eye glasses).

Here are some explanations of why the over use of contact lenses can cause damages:

When you keep the lenses in your eyes for long hours, it will induce many troubles such as dry eyes, scratches on the surface of cornea, many types of conjunctivitis caused by allergies and bacteria, pinguecula, ptosis, etc. These troubles will cause pain and are easy for patients to recognize and seek medical care. These disorders can most likely be cured by discontinuing the use of contact lenses followed by proper treatment (there are exceptions depending on each case).

However, there is a disease that can remain unnoticed until it reaches the advanced stage, such as decreased corneal endothelium. Many contact lens users may think it is ok to wear the lenses as long as they want or even go to sleep with them in their eyes if they do not feel any symptoms or abnormalities. But in truth, these people may already suffer from corneal damages (decreased corneal endothelium) by such habits. This is more serious than people think. Please refer to the pictures below:

Healthy corneal endothelium: all in same sizes.

Abnormal corneal endothelium: noticeably differ in sizes

Now, what is corneal endothelium? These are the cells found in the most inner layer of the cornea, where the corneal breathing and metabolism take place. These cells play a very important role in keeping the transparency of the cornea. They will not increase or regenerate once they are depleted, meaning they will not return to the normal state even if you discontinue to wear the contact lenses. In case they decrease below the ideal number, they will be unable to keep the transparency of the cornea and this will cause edema and dullness associated with pain. At this point, the only choice of treatment will be corneal transplantation, which still cannot return the cornea to the original healthy condition.

In our clinic, we usually perform the corneal endothelium measurement for the patients who have been using contact lenses for 10 years or longer, or those who keep the lenses on for long hours. My staff and I are surprised on a daily basis that so many patients are seen with decreased corneal endothelium. Ideally, 2500 to 3000 cells should be seen, but there are many patients with lower than 2000. Just the other day we saw a patient with only 500 corneal endothelium even though the patient is still in his 20's.

These cells will deplete with age, however, there are many young people who have a lower number of corneal endothelium than those in their 60's or even 80's. When these cells are tremendously depleted, certain eye surgeries such as that for cataract can no longer be performed. Since most elderly people nowadays did not wear contact lenses in their young age, it is rare to see them with an excessive depletion of endothelium.

Personally, I am very concerned that there will be more patients in the future who can not have surgeries due to depleted endothelium and the only procedure available for them will be corneal transplantation.

For those of you who wear contact lenses, please try to minimize the contact lens usage to as little as possible, and wear your eye glasses at least one or two days a week! Wearing the contact lenses in sleep or keeping the disposable lenses on for days (or years!) can cause the worst damages you can imagine. It may be hard to realize something invisible, but please make conscious changes for the better starting today.

I will be most grateful if this article could contribute in any way to improving the future health of your eyes.