The eye is covered in a tear layer, and we all know that tears can be increased with stress, sorrow, or even the wind, sometimes rolling down the cheek in a torrent. The tears both keep the eye clean and also are the critical front optical surface of the eye. What is less appreciated, is that a decrease in tears can actually result in blurred vision. This blurry vision is many times thought to be due to some other problem than a dry eye cause. We have to understand that the tears are actually made of three separate layers. The outer or lipid oil layer slows tear evaporation. The main layer is the liquid layer which is mostly water and some solutes such as sodium which is what makes tears salty. The inner layer which smoothly attaches the tears is a mucin or mucous layer, kind of the glue which attaches the tears to the front of the eye or cornea. If any of these layers don't work right, we can have a tear problem. These problems can make it more difficult to wear contact lenses which float on the tear layer and can become blurred and uncomfortable when there is a lack of proper tears.
It is important to understand that some other problems such as inflammation of the eyelids can cause something called blepharitis which is an inflammatory condition that can mimic dry eye and is helped by lid hygiene and sometimes antibiotics. Furthermore, recent advances have shown that dry eye itself many times has an inflammatory component. This means that anti-inflammatory agents can greatly help dry eye by both reduction of inflammation and the consequence this has on tear production.
There are many methods to analyze tear production, but the basic ones measure how much tear is produced and how well the front surface of the eye is wetted by the tears that exist. The Schirmer test is one basic test of tear production. Once tear deficiency is diagnosed, there are several treatment options.
Proper hydration, that is drinking enough water, can help with dry eye problems. Alcohol, coffee, and many medications are drying to the eyes and sometimes need to be avoided. Antihistamines, and some blood pressure medications reduce the normal production of tears. Since the lipid layer of tears has a dietary aspect, eating foods high in Omega fatty acids or taking supplements can in some cases be helpful. Most people get enough of these things in a healthy diet. Artificial tears can help temporary dry eye situations, such as after eye surgery, or on a windy day, but this is temporary and requires frequent drop installation. Another method is punctal plugs, which help to block the drainage of normal tears that end up going down the back of the throat, and this can provide great relief. There are four exit channels for the tears in both eyes so blocking either two of these, or in some cases all four has been useful. There are temporary punctal plugs which last for days to weeks or so called "permanent plugs" which are placed without surgery by your eye doctor and can last much longer.
Another new development is using a medication called Restasis, which is an anti-inflammatory that has proven useful in improving dry eye especially in women. It needs to be used every day for several weeks to months to achieve a benefit, but the results can continue even after the medication is stopped. There are other anti-inflammatory medications which also play a role in dry eye treatment.
We like to carefully evaluate patients for dry eye issues before LASIK vision correction surgery, because the procedure temporarily cuts small corneal nerves, and this can increase dry eye problems until the nerve endings grow back which usually takes about three months. For this reason we place temporary punctal plugs in all of our LASIK patients, and have them all use artificial tears during their healing period. This way we hope to prevent most problems that could be dry eye related. Besides some mild eye discomfort, dry eye problems can cause blurring of vision and redness of the eyes. We also have the patient evaluated carefully at all post operative visits to evaluate and treat any dry eye issues.
One interesting finding in recent studies is that LASIK performed by the all laser method have less dry eye problems than those performed with a microkeratome. This is probably related to less damage to the eye surface during the gentler procedure which keeps that delicate surface layer intact. Their are variable reports about PRK but we have found that overall PRK patients tend to have more dry eye problems than LASIK patients, all other things being equal. If you are concerned about dry eye and LASIK we suggest you come in for a no cost evaluation of your eyes where we can review these concerns with you in person.