Contact lenses and dry eye - Part 1
EyeThera dry eye special segments
How can contact lenses contribute to dry eye misery?
Remember that good blinks are important because they work tear oil (Meibomian) glands, while simultaneously washing old tears away and bringing fresh, new tears up from the lower lid "gutter" (or fresh "tear well") to cover the surface of the eye.
Dryness triggers the blink reflex - but wearing a contact lens can shield the surface from recognizing it is becoming dry. Average "normal" blinking rates vary from 10 to 20 times a minute but becomes far less wearing contact lenses (as little as 5 or less times a minute). Those contact lens-shielded blinks also have a greater tendency to be what we can call "poor" or "partial“ blinks, which teach the oil glands not to work. Also importantly, these partial blinks expose the contact lens to greater evaporation. This can lead to more salt and protein deposits on the surface of the contact lens, making the contact lens less tolerable to wear and leading to inflammation of the eye. This can cause the eye to "reject" them, while leading to more dry eye problems at the same time.
Because soft contact lenses are little sponges, allowing oxygen and tears to work into and around them, they also catch and soak up pollutants, allergens like pollen, as well as finger-and airborne germs that get into and onto them. This can add to the irritation, inflammation and “rejection" of the contact lenses, as well as damaging the tear producing glands. This is why cleaning and proper fitting of contact lenses is required. Ironically, many of the cleaning products and protocols used to care for contacts can also lead to dry eye problems! (More on this below).
Some contact lenses are prescribed specifically to help dry eye patients. These are generally hard contacts called scleral lenses. They "vault" over the sensitive surface of the eye and hold some salty tear water over that cornea, so it doesn't dry out. Now the surface of the eye becomes the plastic of the contact lens instead of the sensitive cornea - so this can help in extreme cases of dry eye, while also correcting the need for glasses.
So why don't we put all of our dry eye patients into these little "fish bowls?" Remembering that the cornea needs more than salty water to best survive, some who make very poor tears may need to add more "human" products to the tear water kept under these lenses. This is often accomplished by using Autologous Serum Tears (ASTs) - an artificial tear made more human-like by processing vials of your blood (the autologous part) and adding the health factors to the artificial tear. This generally means you need to give your blood by way of needle sticks, into a number of vials every few months. A lab processes out the red blood cells and mixes up the ASTs, freezes them and provides them in little dropper bottles that should remain frozen until they are used by you over those months. The cost is not covered by most insurance plans and can run three to four hundred dollars a month, in addition to the cost of the contact lenses (which may be covered under some insurance plans - check with your doctor on this if you're interested).
These specialty contact lenses need frequent removal, cleaning and replenishment of the salty water and/or ASTs throughout the day - so they can be a major nuisance to use - but can also be a lifesaver (or sightsaver) when used in the more advanced - or end-stages of dry eye disease. ASTs can also be used without these lenses and can help to add necessary components to improve the quality of poor tears. Ask your dry eye specialist if you qualify - but also remember that if you take good care of your tear glands, then it becomes less likely you will ever need this degree of special (expensive and inconvenient) dry eye care.