A Two-Pronged Approach to Keratoconus Management

In my specialty lens practice, deciding whether to recommend optical correction or corneal crosslinking (CXL) for my patients with progressive keratoconus (KC) is easy, as both are almost always needed. When patients cannot see 20/30 or better with glasses, I usually choose scleral lenses because they do not rub against the cornea and require less washout prior to CXL. I tell patients that scleral lenses will improve their vision but won’t stop the progression of their disease; only FDA-approved epithelial-off (epi-off) CXL can do that.

TWO IS BETTER THAN ONE

Studies show that epi-off CXL can stop KC progression about 95% of the time and stabilize the cornea for up to 10 years after treatment.^1,2 Patients who wore vision correction previously will still need glasses or contact lenses to see and, depending on the severity of the KC, will often need a specialty lens to achieve their best vision. The latest research suggests patients fit with scleral lenses prior to CXL can successfully resume wear of the same scleral lenses after CXL, with no significant differences, on average, in corneal measurements or refractive correction after the procedure.³

In addition, new advances in specialty lenses—such as impression-based lenses (Figure 1), scleral profilometry (Figure 2), and the Pentacam (Oculus) Corneal Scleral Profile (Figure 3)—may help improve the specialty lens fitting process, as they can precisely match the contour of the sclera to the scleral lens. The WaveDyn (WaveFront Dynamics; Figure 4) can detect and correct many of the visual aberrations commonly found in KC, including coma.

The patient’s age, stage and severity of KC, motivation, and visual function all factor into deciding which vision correction plan to pursue. In the early stages of KC, if the patient can see relatively well with glasses, I push them toward earlier CXL. Sometimes, we turn to contact lenses first because the patient hasn’t yet met the criteria for preauthorization for CXL, which typically includes at least one of the following: an increase of ≥ 1.00 D in steepest keratometry, an increase of ≥ 1.00 D of cylinder in subjective or manifest refraction, or a myopic shift of ≥ 0.50 D of spherical equivalent refractive error.⁴

Tomography is very helpful in diagnosing and monitoring KC because it can evaluate the posterior corneal elevation. For practitioners who don’t have tomography or wavefront devices, referring the patient to a doctor who does have one is an important first step whenever KC is suspected or a patient younger than 45 years of age inexplicably doesn’t correct to 20/20.

Case No. 1

A 14-year-old male patient with high astigmatism and a BCVA of 20/40 with glasses was referred to me by another optometrist who suspected possible refractive amblyopia or KC. The patient’s higher-order aberration root mean square value was 0.45 µm, which, for a 6.00-mm pupil and young age, is high.⁵ On the Pentacam, his Belin/Ambrósio Display final D score was 2.75, which would indicate prekeratoconus (D values ≥ 2.00 and < 3.00 are considered prekeratoconic).⁶ Corneal mapping did not show frank KC, and we did not yet have data points showing a clear change over time. Although he didn’t meet the diagnostic criteria for KC, we had a high suspicion that KC may develop. I fit him with scleral lenses to improve his vision to 20/20, and he will be followed with repeat tomography every 3 months to watch for signs of progression indicating the need for CXL.

Case No. 2

A 32-year-old male patient who was first diagnosed with KC at 18 years of age and was fit with scleral lenses elsewhere began seeing an optometrist in our practice 2 years ago. At that time, his BCVA was 20/20 with scleral lenses and 20/50 with glasses. In the 14 years since his diagnosis, he had never seen a cornea specialist, let alone undergone CXL.

Now in my chair, I found that his vision in the right eye could suddenly only be corrected to 20/30 with scleral lenses and that both eyes had lost several lines of vision with glasses. Also, his corneas were thin, with pachymetry of 404 µm (down from 414 µm the previous year), and he had high levels of higher-order aberration. The patient had progressed after a long period of stability, and I explained to him that the change in his vision meant he had progressed to a stage in which scleral lenses could no longer compensate for the induced aberrations from the cone. I recommended CXL as soon as possible, after which, we would be able to fit him in a more customized scleral lens with wavefront-guided optics to further improve his vision.

DO WHAT YOU CAN WITH WHAT YOU HAVE

I can’t perform epi-off CXL in California where I practice, but I can evaluate whether a patient has KC, document any signs of progression, and offer them guidance down the paths of specialty lenses and CXL. By pursuing both paths at the same time, we can achieve the dual goals of improved visual function and controlled disease progression.