A 24-year-old college student and his parents were referred by his optometrist after noticing worsening vision in both eyes due to increased astigmatism. This is often a high-anxiety situation and requires a thorough explanation of the imaging tests performed and the reason for the pathology.
The working diagnosis in this patient, keratoconus, was confirmed by increased inferior steepening on topography and irregular astigmatism. Based on his prior records, it was evident the refraction increased from 3 diopters to 5 diopters of astigmatism over the course of 1 year. Previously, we had nothing to offer these patients except observation and a hard contact lens. However, now we can perform FDA-approved corneal crosslinking to potentially stop the progression of keratoconus. The patient and family were educated regarding the risks and benefits. The main risks of this procedure include corneal haze and bacterial keratitis. However, I always explain that, if monitored closely and carefully, the procedure is safe and effective.
A Safe, Effective Procedure
Preoperatively, we perform a thorough slit lamp exam, corneal topography and tomography, as well as anterior segment OCT with Epithelial Thickness Mapping (ETM) to help correlate the epithelial thickness with pachymetry. The epithelium is typically thinnest over the steepest part of the cornea. The corneal thickness should be at least 400 microns for safe cross-linking. Throughout the process, highly trained technicians who are partners in the cross-linking preparation and procedure give patients a great deal of information and comfort.
One pearl to avoid excessive dehydration of the cornea is to remove the lid speculum and close the eye during the loading of the riboflavin. If we were to keep the eye open with the speculum during the loading process, the cornea would dehydrate, causing the thickness to be <400 microns. If this occurs, we need to swell the cornea using Photrexa® (Avedro) until the corneal pachymetry measures >400 microns. Postoperatively, we customize care, but it always includes a topical antibiotic and a slow tapering of topical steroid. We bring patients back often, starting at day 1, day 3, and then 1 week. Once the epithelium heals, everyone can breathe a little easier, as the risk of infection is negligible.
Averting Corneal Haze and Bacterial Keratitis
The two things physicians should monitor for after cross-linking are corneal haze and bacterial keratitis. In addition to long-term low-dose steroid loteprednol ointment for 3 months, we bundle PROKERA into the cross-linking cost, so patients will also have the benefits of its anti-inflammatory effect.
My colleagues and I did an internal retrospective review of some cross-linking patients. Of 47 subjects, 24 had a bandage contact lens (BCL), while 23 patients received PROKERA immediately after surgery. PROKERA or the BCLs were all removed at day 4. We found that the PROKERA group epithelialized faster at day 7 (PROKERA 86%; BCL 73%). When we evaluated persistent corneal haze (grade 1+) at 3 months, we saw it affected 21% of eyes in the BCL group, but only 9% of PROKERA patients. The sample size is too small to be statistically significant, but the results are intriguing.
Patients who use PROKERA Slim will feel as if something is in their eye. The key is to give appropriate expectations and be there for patients if they are having trouble. I prepare patients in advance, telling them, “For 4 days, you’re going to feel like something’s in your eye. I’m here with you. If you really can’t handle it, I’ll take it out. But, please try to see it through.” When they understand how this approach benefits their eye health, they are more motivated to use the technology.
Case Presentation: 1 month post operatively
These OCTs represent bilateral eyes of a patient who had PROKERA in the first eye and a BCL in the second eye. The patient had significantly more haze in the BCL eye and needed prolonged steroid treatment to clear the corneal haze.
An Exciting Future
Tying it all together, I think these technologies help us care for patients in a more systematic and clinically relevant way. We will use ETM as a baseline, and we’ll look at topography and tomography. Then, we’ll use epithelial thickness mapping again for post-op surveillance. It is exciting to see what we can do for patients with today's innovations. ❖
DISCUSSION
DR. RAJPAL: Dr. Fram, you apply PROKERA in the OR on the day of the cross-linking procedure and bundle it. But cross-linking doesn’t have a global post-op period. Do you sometimes apply it in the follow-up visits if the epithelium isn’t healing? If so, are you able to bill for both separately?
DR. FRAM: If we need to, we can charge separately for PROKERA. In many cases, we will bundle this into our pricing to avoid issues with billing. Alternatively, one can apply PROKERA on day 1 or 2, noting a non-healing epithelial defect and billing the patient’s insurance appropriately.
DR. RAJPAL: Dr. Mattheis, how has OCT enhanced your ability to follow your patients?
DR. MATTHEIS: When we treat dry eye prior to LASIK, we can flip through patients’ repeated OCT maps each time they come back and say, “This is what you started out with. It is getting better, but not completely resolved.” We can do the same thing if patients have dry eye post-LASIK. It’s an objective tool for following patients, and the graphic colors and numbers make any differences very clear. We can even see very quick responses with artificial tears or prescription dry eye medications.
DR. RAJPAL: Dr. Fram, are you using Pentacam (Oculus) for the diagnosis of keratoconus as well as monitoring for progression?
DR. FRAM: Yes, I think Pentacam is the standard of care. It’s important to understand how to correlate the steepening of topography with the thinning in the pachymetry, and now the epithelial thickness mapping that matches the thin area on pachymetry is important. I think we’re providing a better level of care because we have this technology.
DR. RAJPAL: Whether we’re using OCT or topography or Pentacam in particular for diagnosis, we all agree that early diagnosis is beneficial, as is following patients afterward.
DR. PARIKH: I encourage local optometrists that if they see new onset myopia or hyperopia refractive error, especially in a younger patient, they should perform or refer for a baseline topography and epithelial thickness map. If it doesn’t reveal a problem, the patient should have a second one a few years later.
DR. RAJPAL: I’ve started telling some of the doctors we work with that if they see an increasing refractive shift — more cylinder or a dramatic increase in myopia — they should send those patients to me for imaging. And I think epithelial thickness mapping is going to help us diagnose keratoconus even earlier.
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