Dry Eyes

Dry Eyes

The dry eye is often referred to as a condition, a syndrome, or a disease; and it is likewise known by a variety of terms. Keratoconjunctivitis sicca (KCS), or more commonly keratitis sicca, refers to any eye with some degree of dryness either by history or by objective clinical findings. The literature is confusing on this subject and often blurs the difference between the symptoms of dryness and clinical findings based on objective criteria. In similar fashion, the term dry eye syndrome is sometimes used interchangeably with dry eye symptoms, a lapse in descriptive terminology that unfortunately clouds the issue. Other descriptive terms for ocular dryness include xerophthalmia, which is used almost exclusively to describe the eye findings associated with vitamin A deficiency in children, and xerosis, which connotes the extreme ocular dryness and keratinisation that sometimes occurs after Stevens-Johnson syndrome, trachoma, and other causes of severe conjunctival cicatrisation. And then there is Sjögren’s syndrome, a generalised inflammatory disease that stands alone in its own category. Patients with Sjögren’s syndrome usually have dry eyes or KCS but they also have or may not have an associated rheumatological disease depending on whether they have primary Sjögren’s syndrome (without associated rheumatological findings) or secondary Sjögren’s syndrome (with an associated rheumatological disease). Having KCS does not necessarily imply that a patient has Sjögren’s syndrome, but the reverse with few exceptions is usually true.

The truth of the matter is that dry eyes, for which we can interchangeably use the term KCS, is a neglected orphan. Even though it has been recognised for 70 years, since Sjögren first described the syndrome that bears his name in 1933, progress has been frustratingly slow in agreement on the diagnostic criteria for Sjögren’s syndrome as well as on treatment for all forms of KCS. This situation exists because KCS is in reality a condition that occurs in a family of orphan diseases. To be sure, Sjögren’s syndrome sits at the head of the table, but the other orphans in the KCS family have a way of frequently showing up quite unexpectedly. After Sjogren’s syndrome, there is a second group of diseases that has already been mentioned that can also produce severe KCS. These are the conjunctival cicatrisation syndromes: Stevens-Johnson syndrome, trachoma, ocular pemphigoid, drug induced pseudopemphigoid, graft versus host disease, chemical burns, and conjunctival cicatrisation that occurs after severe membranous conjunctivitis. A third group consists of those individuals who have signs of KCS because of a specific ocular disease: dacryoadenitis, congenital absence of the lacrimal gland, Riley-Day syndrome, cholinergic blockade due to drugs such as atropine, chronic blepharoconjunctivitis, senile atrophy of the lacrimal gland, and even the current epidemic of presumed KCS that occurs after refractive surgery. And the fourth group includes those atypical dry eye “orphans” that appear to have clinical KCS but who in reality have adequate tear production: trigeminal nerve paralysis with loss of corneal sensation, facial sensory nerve paralysis, exposure keratitis, and vitamin A deficiency resulting in xerophthalmia.

So we are presented with a family of orphan diseases, all complicated, many posing as diagnostic dilemmas,and none that is easily treatable. Treatment is, indeed, the issue here. If we look at Sjögren’s syndrome alone, there have been 70 frustrating years of having to rely on partially successful ameliorative therapy for both the xerostomia and the KCS components of the syndrome. We still cannot “cure” Sjögren’s syndrome. We can only make patients more comfortable and, fortunately in the case of the eye component, we can usually prevent the complications related to microbial keratitis that led to blindness in some cases of KCS in the past. And yet our treatment is still ameliorative, not curative, and until we find a way to reverse the inflammatory component of Sjögren’s syndrome, just to name one of the orphans, millions of individuals, mostly women, will suffer daily discomfort and disability.

There is no therapeutic panacea for dry eyes. As a clinician taking care of dry eye patients on a daily basis, I find the treatments often frustrating and unrewarding. There are no “quick fixes,” and to know the various treatment options that are available for our patients is definitely not to love the choices. To be sure, we have learned a few important lessons in the supportive treatment of KCS over the past few years. For instance, we have become vigilant about recognising and controlling secondary infections. However, probably the most important lesson we have learned is that dry eye patients usually do not tolerate artificial tears on a long term basis, especially those that have preservatives in them. The dryer the patient’s eyes and the more frequently they need eye drops, the more important becomes the issue of preservatives. Dry eye patients with chronic epithelial keratitis were particularly susceptible to corneal infections, so the development of commercial preservative free artificial tears in individually packaged disposable containers was a godsend. However, development of the ideal solution that mimics human tears with all of their complicated constituents has remained elusive. One has only to look at a short list of artificial tear preparations that have been tried in the recent past to realise that there is no ideal solution. Exotic tear substitutes, including human serum albumin, fibronectin, vitamin A drops, and sodium hyaluronase, to name but a few, all purport to contain certain factors and antiproteases that mimic human tears, but all have proved disappointing. They are either too difficult to manufacture on a commercial basis or they are too expensive. Other topical medications based on their anti-inflammatory effects, such as corticosteroids and cyclosporine, are of questionable benefit especially in cases of severe ocular dryness.

Those of us who take care of patients with severe KCS have known for several decades that there are some individuals who cannot use any artificial tears, even preservative free, on a sustained long term basis without developing an allergic reaction or toxicity to the drops. We have also found anecdotally that the one tear substitute these patients can almost always tolerate is their own serum.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1772141/
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