Managing keratoconus requires thorough and early corneal analysis. You can use different techniques but it can be challenging to diagnose, especially in young patients. Here are some of the best ways to assess the health of a cornea.
What Is Keratoconus?
Keratoconus is a progressive, noninflammatory corneal ectatic disorder that typically affects individuals starting in adolescence and progresses throughout the second and third decades of life.
It is characterized by progressive stromal corneal thinning, typically inferiorly or centrally in the cornea, creating a corneal bulge known as a cone. The condition may begin unilaterally but is bilateral in nearly 96% of cases and can be asymmetric in severity and progression between the two eyes over time.
Genetic predisposition may play a role in about 20% of patients; however, eye rubbing is a big independent risk factor. In addition, systemic comorbidities such as atopy, Down syndrome and connective tissue disorders, among others, can be linked to the development of keratoconus.
How to Detect It Early
Early diagnosis of keratoconus can be challenging clinically. Subtle changes in corneal curvature can often be hard to detect at the slit lamp. It is easier to see more advanced signs of keratoconus, such as marked corneal stromal thinning, Fleischer rings (iron deposition in the basal epithelium), Vogt’s striae (vertical lines in the posterior stroma and Descemet’s membrane at the apex of the cone), Munson’s sign (protrusion of the ectatic cornea causing pushing out of the lower eyelid) or hydrops (swelling in the cornea due to breaks in Descemet’s membrane).
Imaging with corneal topography and tomography is the preferred method for early detection of keratoconus. Subtle changes in posterior corneal elevation seen on tomography can be the first signs of this condition. Images should also be carefully analyzed for irregular astigmatism, abnormal keratometric steepening and anterior corneal cones (i.e., inferior steepening with an asymmetric bowtie appearance and/or central steepening).
Corneal collagen cross-linking has been a paradigm shift in the treatment of keratoconus. Epithelium-off cross-linking with the Dresden protocol was Food and Drug Administration-approved in the United States in 2016 to treat progressive keratoconus.
In this procedure, patients are given topical anesthesia, the corneal epithelium is removed and riboflavin is administered to the corneal stroma. After adequate riboflavin administration and ensuring the cornea is of adequate thickness (at least 400 microns), the cornea is exposed to ultraviolet A light. This photochemical reaction induces covalent bonds and cross-links or strengthens the corneal collagen fibers. Modified and accelerated epithelium-off techniques are used to shorten the duration of the procedure by often increasing the intensity of the ultraviolet light. These are used more often internationally but would be considered off-label in the United States.
Other cross-linking treatments on the horizon include approved epithelium-on techniques in which riboflavin is administered with an intact epithelium via the addition of supplemental oxygen. These techniques can reduce postoperative risks of pain and the delayed epithelial healing, infection and scarring risks often associated with epithelial removal. However, the efficacy of these methods compared to epithelium-off techniques still needs to be established.
It is important to emphasize to patients that corneal cross-linking is not a reversal procedure but rather a freezing procedure. I advise patients that my goal with the cross-linking treatment is to prevent future progression, not regain lost vision or corneal architecture. Clear expectation setting is important in order for these patients to succeed.
Once stability is achieved, I recommend patients get fit for glasses or custom contact lenses to improve their visual acuity and image quality with the help of my optometric colleagues. A collaborative approach is key.
What Signs Should YOs Look for in Keratoconus Patients?
As you examine patients in clinic, look for subtle and overt signs of keratoconus. If patients have atypical changes in their vision or manifest refractions, obtain a screening topography or tomography.
The condition is often missed in young patients when progression is most common because they will not articulate or do not realize they have vision changes. Instituting screening protocols in pediatric offices or schools can be integral to ensure early cases are detected and not missed. These protocols can include vision checks, obtaining auto-refractions to assess for high refractive error (i.e. high astigmatism) and also performing tomographic images.
If you are not sure of the diagnosis, have a corneal specialist review the case or images with you. I often proactively offer my keratoconus patients’ family members (i.e., siblings, young children, etc.) exams and imaging to help screen for this condition.
Also, always emphasize the importance of not rubbing eyes. When I meet patients with keratoconus, my goals are to diagnose them expediently, offer cross-linking, if possible, establish a partnership with an optometrist to optimize their spectacle or contact lens corrections and ultimately prevent disease progression and corneal transplantation.
||About the author: Nandini Venkateswaran, MD, is a cataract, cornea and refractive surgery specialist at the Massachusetts Eye and Ear in Waltham, Mass. She is also a clinical instructor of ophthalmology at Harvard Medical School. She joined the YO Info editorial board in 2020.