CLINICAL

  ANTERIOR

BATTLE OF THE CORNEAL BULGE

WIN THE WAR BY EDUCATING PATIENTS ABOUT CORNEAL CROSSLINKING

JOSH JOHNSTON, O.D., F.A.A.O.

“NOTHING MORE can be done” is a phrase that both doctors hate saying and patients fear hearing. Unfortunately, we know all too well that many of the ocular diseases we diagnose and manage often require this phrase. The good news: Eye care practitioners are saying this less to corneal ectasia patients, thanks to corneal crosslinking (CXL).

Here, I provide an overview of the procedure, ideal candidates and the O.D.’s role.

PROCEDURE

CXL uses riboflavin drops combined with UVA light to strengthen the cornea by increasing corneal rigidity, collagen fiber thickness and increasing resistance to enzymatic degradation (that leads to corneal weakness). Thus, the procedure is designed to halt the corneal ectasia progression seen in keratoconus, pellucid marginal degeneration and Terrien’s marginal degeneration.

Two forms of CXL exist: epithelium (“epi”)-off and “epi”-on. The only FDA-approved CXL procedure is the Avedro KXL, which is an epi-off procedure for the treatment of progressive keratoconus (approved in April) and corneal ectasia post-refractive surgery (approved in July). Avedro rerecently announced it began shipping the drugs used with the KXL system.

“Epi”-off CXL is comprised of removing the corneal epithelium and dropping 0.146% of Photrexa viscous riboflavin solution on the cornea for 30 minutes, followed by roughly 15 minutes of UVA irradiation to the cornea with a wavelength of 370 nm and a power of 3 mW/cm2.

The non-FDA approved “epi”-on procedure (used in Europe) leaves the corneal epithelium intact. Dosage and procedure techniques will vary with this form, but usually one drop of riboflavin solution is instilled on the cornea every 2 minutes for 30 minutes. Once flare is observed in the anterior chamber, indicating corneal penetration and absorption, 30 minutes of UVA irradiation is applied to the cornea with a wavelength of 365 nm and a power of 3mW/cm2.

The possible adverse events for both “epi”-on and “epi”-off are corneal haze after the procedure, inflammation and damage to the endothelium, such as corneal striae, punctate keratitis and ulcerative keratitis. When performed successfully, both procedures promise lasting efficacy, but long-term data is still needed. (See “Future Treatments,” p.27.)

IDEAL CANDIDATES

Several methods exist to evaluate and document corneal ectasia progression, but there’s no consistent or clear definition to define progression. Experts agree that progression can be viewed as “a consistent change in at least two of the following parameters: steepening of the anterior corneal surface, steepening of the posterior corneal surface and thinning and/or thinning changes in the pachymetric rate of change,” according to the March 2016 issue of Eye and Vision. In these cases, refer patients for the procedure.

A caveat: Progression is rare among patients older than age 40, so, the younger and the earlier any ectatic disease is diagnosed and CXL is done, the better.

O.D.’S ROLE

Individual state scope-of-practice laws dictate whether we, as optometrists, can perform the FDA-approved procedure, as it requires removal of the corneal epithelium.

Patient undergoing CXL.

Should your state law determine the Avedro KXL is out of your scope, you can still play a co-management role. Specifically, you will remove the bandage contact lens once the epithelial defect (from the epithelium removal) is resolved, which usually takes about 5 days. You will also want to watch for signs of any of the adverse events listed in “Procedure.” Next, prescribe topical antibiotics, such as fluoroquinolones q.i.d. until re-epithelialization. Then, prescribe non-preserved artificial tears for comfort and to help promote epithelial healing, a topical steroid, which should be tapered over a few weeks and a topical NSAID q.d. for pain and inflammation.

With regard to follow-up, follow CXL patients the same as you would PRK patients. Specifically, see them on day 1, day 5, day 14 and at one month. In terms of refractive correction, patients can return to glasses post procedure and contact lenses after the epithelium is fully healed and steroids have been discontinued. Be sure to perform a refraction once the patient has healed to adjust for any refractive error changes that might require a contact lens or glasses prescription change.

ENDING SUFFERING

Once diagnosed, corneal ectasia patients now have this treatment option available, so we no longer have to say, “nothing more can be done,” and they no longer have to suffer debilitating vision loss. OM

DR. JOHNSTON practices at Georgia Eye Partners. He focuses on ocular surface disease and has extensive experience in co-managing cataract and refractive surgery patients. Email him at drj@gaeyepartners.com, or visit tinyurl.com/OMcomment to comment.