Dry eye definition:
is the common disease that is widely over-diagnosed and under diagnosed.
In chronic diseases, with variable course and severity like dry eye and POAG we tend to forget the “philosophy of the disease”.
One aspect of this philosophy is “why do i treat this disease”?
Is it because of SYMPTOMS? Or fear of COMPLICATIONS? So i must clearly have symptoms or potential complications to treat otherwise the benefit/risk ratio is disturbed or there is no advantage to the patient’s QOL (quality of life)
Dry eye is not about TEARS, it is about corneal EPITHELIUM and the aim of treatment is protection of the epithelium. When the epithelium suffers, nerves are irritated and symptoms arise.
When dealing with dry eye, i have to know clearly where the defect is and go back to the basic physiology.
1)Is there a problem with the lipid layer? Meibomian gland disease? What is the problem with the glands? Infection? Or altered secretion or age changes?
2)is there a deficiency of the aqueous layer? Why? Is there a collagen disease esp RA, Sjogren? Is it gender-related (post menopausal estrogen deficiency)?
3)is there a problem with the mucin layer? Trachoma? Topical medications that destroy goblet cells? Immune damage?
4)or the problem is in the epithelial cells themselves? Corneal stem cell deficiency, anti-epithelial Abs in OCP, post-Lasik and other causes of deficiency of neurotrophic factors.
Why is identifying the cause important?
Because you cannot treat one cause with the treatment of another (of course you can always prescribe artificial tears for ALL cases as most do but do not talk to me about Dry Eye)
This forward is very important because the practice of dry eye is one of the most difficult in ophthalmology yet it is the most lightly taken
Exactly like uveitis where everyone is given big dose of corticosteroids then gradually withdrawn, everyone complaining of ocular surface irritation is given artificial tears and the pockets of the drug companies are getting loaded.
You can easily judge the economic size of a drug market by looking into the number of products in the field/available clinical tests to assess drug effect. What protects the glaucoma drug field is the presence of a practical way to measure drug efficacy (IOP)
We critically need a practical way to assess the efficacy of dry eye medications. Till this test is available we will loom in darkness.