BLOG: Corneal cross-linking a collaboration among ophthalmology, optometry, industry
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Optometrists are often first to diagnose a patient with keratoconus and hold a great responsibility for referring patients for corneal cross-linking in a timely manner.
In addition to early diagnosis of the condition, optometrists are responsible for educating the patient, managing appropriate referrals and staying up-to-date with the latest literature.
The optometrist’s role, perspective
Early diagnosis is the key to offering optimal care and management for patients with keratoconus. Optometrists should be playing detective for patients with increasing myopia or astigmatism, scissoring retinoscopy reflexes or abnormal autorefraction mires. Topography is critical in making the diagnosis. Tomography can play an even greater role in diagnosing the condition sooner. Features like the Belin/Ambrósio Enhanced Ectasia display on the Pentacam (Oculus) help the optometrist diagnose cases earlier than Placido-based topography. In addition, epithelial thickness mapping on OCT can also help in early diagnosis. Optometrists should no longer wait for decreased visual acuity or corneal signs on slit lamp findings.
After the diagnosis is made, strong patient education is crucial. This should include the progressive nature of the condition and the management of the condition, including both CXL and optical correction. Patients should not only learn what CXL does, but also what it does not do. They should leave the office with the knowledge that CXL can stop the condition and strongly reduce the likelihood of a corneal transplant, but that it does not reverse the condition. Patients who better understand keratoconus and its progressive course are more likely to schedule an appointment for CXL.
The next step is making the referral in both an educated and smooth manner. This includes making a case-by-case clinical analysis, knowing your local referral network and supplying the appropriate referral materials. In my practice, I educate every patient with keratoconus, no matter the age, on CXL. Early-onset keratoconus is more aggressive, and a speedy referral for CXL is imperative. The probability of keratoconus progression strongly declines after age 40, but it never goes to zero (Anitha et al.). Close monitoring of all patients with keratoconus is important even in the later decades, and referrals for progressive cases should be made.
For a smooth and easy referral, optometrists should know the ophthalmologists in their area who perform CXL. This includes which doctors do on-label only procedures and those who perform off-label procedures as well. Referring the patient with their records, summary of any previous refractions and K values, including steep K and maximum keratometry (Kmax), can be particularly helpful in case analysis and for timely insurance coverage.
Staying up-to-date in the world of CXL — on current protocols and those in the pipeline —is the final role of an optometrist. Knowing about CXL and how to manage your patients who may need it will help the optometrist best serve their patients.
With less advanced cases of keratoconus, enhanced visual results in the optometrist’s office can be achieved through spectacle correction and custom contact lenses, like scleral lenses.
The ophthalmologist’s role, perspective
Imagine a 23-year-old man coming in for blurred vision in his right eye. His visual acuity is 20/100 without correction. His manifest refraction is –9.00 D + 6.75 D x 73, with best corrected visual acuity of 20/40. IOP is normal. The cornea has an abnormal shape, but otherwise the fundus exam is unremarkable. A topography demonstrates inferior steepening with Kmax greater than 50 D — an undeniable diagnosis of keratoconus is made. Yet, as this diagnosis settles in, a crucial question looms: What course of action should be pursued next?
Keratoconus, a bilateral and noninflammatory corneal ectasia, has the propensity to progress into severe corneal thinning. This progression manifests as conical protrusion, ultimately resulting in a significant reduction in BCVA due to a trifecta of factors: high myopia, irregular astigmatism and apical corneal scarring. The disease typically affects people in their second to third decades and can be associated with excessive eye rubbing. Patients present with painless blurred vision and require frequent prescription changes as the disease evolves.
Once traditional corrective measures such as spectacles, soft contact lenses and gas permeable lenses fall short in achieving functional BCVA, the management shifts to scleral lenses, which vault over the cornea and overcome the irregular astigmatism. For patients who cannot tolerate contact lenses, intrastromal corneal ring segments may be implanted. However, none of these approaches halt the underlying disease progression.
Enter CXL, a noninvasive treatment modality introduced in the late 1990s that aims to arrest keratoconus progression prior to requiring lamellar or penetrating keratoplasty. CXL strengthens corneal collagen fibers through a photochemical reaction involving ultraviolet-A light on a riboflavin-saturated corneal stroma, forming covalent bonds between collagen molecules and proteoglycans. Multiple studies have shown that CXL can achieve long-term corneal stabilization, improve BCVA by one to two lines and reduce maximum keratometry by 1 D to 3 D (Raiskup et al, Raiskup-Wolf et al, Wollensak et al).
FDA approved as an epi-off procedure in 2016, traditional CXL involves removing the corneal epithelium before applying UVA light, enhancing riboflavin absorption for a deeper therapeutic effect. Despite its effectiveness, the risks of epi-off include pain, infection, haze and corneal scarring. Recent attention has focused on the epi-on technique, essentially the same CXL procedure without corneal epithelial removal. Proponents argue for its safety, with less pain and reduced risks for infection and corneal scarring. However, studies yield mixed results, with some indicating equivalent effectiveness and others showing a superior reduction in mean keratometry with the epi-off method (Cifariello et al, Wen et al).
As we return to our patient — a young man with a moderate stage of keratoconus — there exists a divergence in the approach among ophthalmologists. Some advocate for close observation, with repeat refraction and topography measurements in short intervals, opting for CXL if any progression is detected. On the contrary, others assert that in moderate to severe cases exhibiting diminished BCVA, immediate intervention is indicated. The absence of a one-size-fits-all approach underscores the importance of a detailed discussion with the patient.
In the collaborative landscape of eye care, our optometric colleagues often take the lead in initial diagnoses, while our industry collaborators ensure that cutting-edge technologies for CXL remain at the forefront. Within the Women in Eyecare initiative, the fusion of ophthalmic, optometric and industry perspectives propel the field forward, fostering innovative solutions in the battle against keratoconus.
References:
- Anitha V, et al. Indian J Ophthalmol. 2021;doi:10.4103/ijo.IJO_1263_20.
- Cifariello F, et al. J Ophthalmol. 2018;doi:10.1155/2018/4947983.
- Diagnosis and management of keratoconus. https://www.aao.org/eyenet/article/diagnosis-and-management-of-keratoconus. Published September 2020. Accessed Feb. 23, 2024.
- Hashemi H, et al. Cornea. 2020;doi:10.1097/ICO.0000000000002150.
- Hersh PS, et al. J Cataract Refract Surg. 2011;doi:10.1016/j.jcrs.2010.07.030.
- Koller T, et al. J Cataract Refract Surg. 2009;doi:10.1016/j.jcrs.2009.03.035.
- Kollros L, et al. Cont Lens Anterior Eye. 2023; doi:10.1016/j.clae.2022.101792.
- Rabinowitz Y. Surv Ophthalmol. 1998;doi:10.1016/s0039-6257(97)00119-7.
- Raiskup F, et al. J Cataract Refract Surg. 2015;doi:10.1016/j.jcrs.2014.09.033.
- Raiskup-Wolf F, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2007.12.039.
- Wen D, et al. Cornea. 2018;doi:10.1097/ICO.0000000000001632.
- Wollensak G, et al. Am J Ophthalmol. 2003;doi:10.1016/s0002-9394(02)02220-1.
For more information:
Daniela P. Reyes-Capo, MD, practices at the Center for Excellence in Eye Care in Miami.
Stacy Zubkousky, OD, FAAO, FSLS, is an assistant professor at Nova Southeastern University College of Optometry.
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