Ophthalmology & Optometry/Oxygen to Cornea
QUESTION: I have been wearing Scleral lenses for nine years and they have helped me tremendously. I have keratoconus and have had three corneal transplants 40 years ago. My transplants are not rejecting but I am now seeing rainbows around light sources from one of my eyes. My doctor told me that this is due to lack of oxygen to that cornea and told me to wear this lens for only six hours and then take it out for two hours. I have found that wearing an eye patch (black pirate-looking with elastic band) helps cut down on the strain and pain when not wearing the scleral lens. My question is: If my eye is shut under the eye patch, am I still getting the needed oxygen to that eye. Also, do eyes get oxygen when we they are closed as we are sleeping? Thank you for your help in answering these questions.
ANSWER: Dear Sandee,
Lack of oxygen to the cornea happens only at the times when you are wearing or using the scleral lens.
This is due the material of the lens itself, nothing to do with your eye.
Lens materials do not allow oxygen exchange to be at its optimal.
Cornea is that part of your eye where the coloured portion can be seen, sclera is the white portion.
Obviously, there is a better exchange of oxygen when using simple soft contact lenses. When the material becomes harder like RGP's, then the exchange is lesser, and same goes for scleral which covers a larger surface area.
Hence, the doctor has asked you to have more lens-free time for the eyes to maintain the health with better oxygenation.
when using glasses / patch etc, the oxygenation will be fine.
Again, when the eye is shut with the lid tight on it, oxygen exchange will be negligible.
I hope you understood the fundamentals of oxygen exchage on the cornea, to help you plan a practical routine.
---------- FOLLOW-UP ----------
QUESTION: From what I understand you saying is that I will still be getting oxygen when I wear the eye patch. But I'm wondering if this remains true if my eye is closed underneath the patch? And do I understand correctly that during all the hours of sleep my cornea is not receiving oxygenation because my eyelid is closed during that time...is that right? Thanks for your response.
Yes, you have understood correctly, however, it is not that the cornea receives absolutely no oxygen when eyes are closed or patched, When the eye is closed, the cornea receives oxygen from the blood vessels in the underside of the lids. Hence in waking hours better to allow maximum oxygen permeability.