Hot Topics on the Ocular Surface

Just when you thought you’d read everything about dry eye and ocular surface disease, along comes the International Workshop on MGD report with an entire IOVS issue devoted to meibomian gland dysfunction and its effect on the eye, especially its association with ocular surface disease (Invest Ophthalmol Vis Sci. 2011;52[4]). As with all good evidence-based information, the report leads to more questions than answers, but offers a basis to organize our thinking about MGD.

Each upper eyelid has 30 to 40 meibomian glands, and the lower lid 20 to 30. Meibomian glands contribute about 0.3 % to 7% of the tear-film thickness. Disease of these glands is the cause of more than just dry eye; the condition is also the potential cause of the high drop-out rate from contact lens use. Only a few studies have evaluated the prevalence of MGD, with findings ranging from more than 60% to as low as 5%. Nearly 64% of patients with dry eye disease also have MGD.

Unlike clinical trials on dry eye disease, investigations of MGD have been few, and most are not rigorous, masked, randomized, controlled trials. The field is ripe for new thinking and new approaches to understanding and treating this common ailment.

Enjoy the two approaches presented in this issue of Dry Eye & Ocular Surface: the role of inflammation in MGD and the change in the tear-solute concentration (the solute gradient hypothesis). Read on, and next time you look at those lids you may be the one to figure out what causes MGD and how it relates to ocular surface disease.

Talking about hot topics, UV cross-linking is at the top of the list for new procedures with a growing roster of indications. Combining UV light with riboflavin eye drops to the cornea appears to “stiffen” the cornea and add stability to the corneal shape, thereby preventing progressive changes in corneal topography as seen in keratoconus and ectasia after laser refractive surgery. For years, we’ve heard of the harmful effects of UV light, including cataract formation and macular degeneration, but in the current UV cross-linking procedures, use of riboflavin causes the UV light to concentrate its effects to where the riboflavin is, i.e., in the corneal stroma, minimizing UV’s effect on the endothelium or other ocular tissue.

However, changes occur in the cornea, including apoptosis of corneal cells, keratocytes and changes in the confocal appearance of corneal tissues. Though this technique was first described more than a decade ago and is now standard treatment in Europe and Canada, the FDA had not approved its use in the United States.

Several trials are now underway that researchers hope will lead to FDA approval soon. In addition to stabilizing the corneal shape, UV cross-linking is being used to treat keratitis that does not respond to anti-infectious treatment and to decrease corneal edema associated with endothelial failure. Turn to page 6 to learn from presenters at the recent UV cross-linking meeting in Colorado about current thinking on this new procedure that may soon become the standard treatment for keratoconus.

Penny A. Asbell, MD, FACS, MBA