At A Glance
- The risk of keratoconus progression is high in young patients, but progression can take place even later in life; therefore, monitoring patients over time is necessary.
- Corneal crosslinking can halt progression of keratoconus, but specialty contact lenses may be needed after the procedure to provide patients with their best vision.
- Patients with mild keratoconus can have adequate vision with glasses alone, and the optometrist’s goal should be to keep them that way.
A 26-year-old man drove more than an hour and a half to our clinic for a LASIK evaluation due to what he described as unacceptable vision with glasses and contact lenses. His entering UCVA was 20/60 in the right eye (OD) and 20/70 in the left (OS). He was not wearing glasses or contact lenses, and his autorefraction was OD -6.00 -3.00 x 038 and OS -10.25 -9.00 x 116. His topography confirmed a diagnosis of keratoconus in each eye (OU) (Figure).
Figure. Corneal topography showing evidence of keratoconus in this 26-year-old patient’s right (A) and left (B) eyes.
The question then was: Do we refer this patient to an optometrist for specialty contact lenses, or do we perform corneal crosslinking (CXL) first? This article discusses the decision-making process involved in determining the answers to those questions.
Keratoconus, with a prevalence of about one per 2,000 people, causes the central or paracentral cornea to progressively thin and bulge so that the cornea takes on the shape of a cone and induces irregular astigmatism.1 As the disease progresses, patients can have extreme irregular astigmatism or corneal scarring that can lead to the need for a corneal transplant. However, there is a high likelihood of patients rejecting a corneal graft over time. Thus, our goal in patients with keratoconus is to halt the progression of the disease and avoid a corneal transplant.2
Who Is at Risk?
Approximately one-fifth of patients with keratoconus progress to the point at which a corneal transplant is needed. Because young patients are at greater risk for progression compared with older patients, we must diagnose keratoconus early. The risk of progression is 90% for individuals less than 20 years old, 33% for individuals less than 50 years old, and 18% for individuals over age 50 years (Table 1).
Although the eye becomes naturally crosslinked with age, patients with keratoconus can still progress; therefore, they must be followed past age 50 to watch for progression. We recommend monitoring patients annually to biannually with BCVA, topography or tomography, and epithelial thickness mapping (Table 1).
In 2016, the FDA approved the Avedro KXL System and that company’s Photrexa riboflavin solutions for the performance of epithelium-off (epi-off) CXL to treat patients with progressive keratoconus and postsurgical ectasia (see What is Progression?). This approval changed our treatment strategy, as we now have the ability to halt the progression of the disease. Specialty contact lenses are also still an option to address irregular astigmatism and, as a last resort, corneal transplantation.
The goal of all eye care providers should be to recognize keratoconus as early as possible and to send patients to a center where they can have a one-time treatment of CXL to halt disease progression (Table 1). These patients still typically need specialty contact lenses to maximize their overall visual potential.
But the question remains: Which should come first, scleral lenses or CXL?
SCLERAL LENSES OR CXL?
The answer is … it depends. First, not all keratoconus patients need scleral lenses. Patients with mild keratoconus can have adequate vision with glasses alone, and our goal should be to keep them that way (Table 1).
Patients who still have BCVA better than 20/40 with glasses or soft contact lenses or any current pair of specialty contact lens and who show any signs of progression should have CXL in both eyes (Table 1). Epi-off CXL is performed bilaterally, with 3 months between procedures (Table 2). We then consider refitting glasses, soft contact lenses, or specialty contact lenses (Table 2).
The FDA approval covers only epi-off CXL, which means that it will take some time for the epithelium to heal, and therefore patients’ vision will be diminished while the eye is healing. Most patients with keratoconus have busy lives. Separating the procedures by 3 months allows the first eye to completely heal before proceeding with the second eye. However, in more aggressive forms of keratoconus, progression can occur while we wait for that second eye procedure, so a shorter time interval can be considered (Table 2).3
If progression is noted but the patient has only one eye with BCVA better than 20/40, CXL is performed on the worse eye first (Table 2). When that eye is healed, we have one of our referring optometrists fit the patient in a specialty contact lens, typically a scleral lens, to see if the visual acuity can be improved (Table 2). Once the eye has undergone CXL and has improved vision, CXL is then performed in the better-seeing eye. Once the second eye is healed, the patient is refit for specialty contact lenses (Table 2).
The Case for Fitting Sclerals First
When a patient presents with both eyes uncorrectable to 20/40, we recommend fitting him or her with specialty contact lenses, most often with scleral lenses (Table 2). Once the patient has been corrected in scleral lenses, we then consider performing CXL as soon as possible. It is important for everyone, patients included, to understand that flattening of the cornea is going to happen after CXL and that it is likely that the patient will need to be refitted for scleral lenses after CXL.
Some may consider recommending CXL first in these patients, but remember that our patient mentioned above was driving with subpar vision. Thus, for the safety of all Texans, correcting his vision was vital. The patient was fit in a Jupiter 16.0 mm scleral lens (Visionary Optics) OU, and he was corrected to 20/20.
Don’t Forget CXL
The only downside to first fitting patients in specialty contact lenses is that they may forget about CXL because they are amazed at their vision with their new lenses. Keep in mind, however, that 10% to 20% of patients with keratoconus who do not undergo CXL will progress to needing a corneal transplant. It is important for optometrists to remind patients about the bigger picture and the possible course of the disease.
TEAMWORK IS KEY
The clinical results of CXL overall have been promising. Several well-designed clinical trials have demonstrated significant improvements in BCVA, significant decreases in mean keratometry, and stabilization of the cornea after CXL.4-10
The fact is, until proven otherwise, any patient with keratoconus who is younger than age 40 should have CXL to halt the disease progression. After CXL, these patients will need specialty contact lenses in order to obtain their best vision (Table 1).
CXL has a global period of 0 days, so optometrists may involve themselves in the postoperative period. However, they should be aware of the delayed healing of the epithelium and potential complications including microbial keratitis and stromal haze.
Whether CXL or scleral lenses come first, there are multiple ways for the modern optometrist to be involved in the treatment and management of patients with keratoconus. These patients require a team approach. By using everyone’s strengths, we can deliver a potential cure for this disease, improvement in overall VA, and a means to decrease patients’ risk of ever needing a corneal transplant.
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- 3. Romano V, Vinciguerra R, Arbabi EM, et al. Progression of keratoconus in patients while awaiting corneal cross-linking: a prospective clinical study. J Refract Surg. 2018;34(3):177-180.
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- 9. Wittig-Silva C, Chan E, Islam FM, Wu T, Whiting M, Snibson GR. A randomized, controlled trial of corneal collagen cross-linking in progressive keratoconus: three-year results. Ophthalmology. 2014;121(4):812-821.
- 10. Hersh PS, Greenstein SA, Fry KL. Corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. J Cataract Refract Surg. 2011;(37):149-160.