Could it be KC (KERATOCONUS)?
KC File #1: The Patient
Who Corrects to 20/20
Mitch “Private Eye” Ibach OD, FAAO, Vance Thompson Vision
A 29-year-old patient came to our office for a LASIK consult because she was unhappy with fluctuating vision in her contact lenses. The patient had ocular allergies but had no other ocular diagnoses.
Her entering glasses prescription was a modest one and we were able to refract her to 20/20. However, the refraction in the right eye was our first clue that something was not quite right.
Not only is >2.00 D of refractive cylinder a warning signal for keratoconus, but the oblique axis is also unusual. About 90% of young corneas have with-the-rule (WTR) astigmatism.1 The change in myopic spherical equivalent (SE) from baseline (the glasses prescription) was not what we would expect to see in an adult patient, either.
Refraction and exam findings
| Right Eye | BCVA | Left Eye | BCVA | |
|---|---|---|---|---|
| Lensometry | -0.50 -1.50 x31 | 20/30 | -1.50 -0.50 x172 | 20/20- |
| Refraction at Phoropter | -0.75 -2.25 x34 | 20/20 | -1.75 -0.75 x160 | 20/20+ |
| Pachymetry | 478 μm | 483 μm | ||
| Autokeratometry | 45.5 / 47.50 x 112 | 44.9 / 46.75 x 80 |
Autokeratometry from her referring optometrist was on the steeper side of normal, and our pachymetry measurements showed that both eyes had borderline thin corneas. Upon further questioning, the patient recalled that her sister had keratoconus. Having a first-degree relative (a parent, sibling, or child) with keratoconus increases the risk of developing the disease by 15- to 67-fold.2
At this point, we have some risk factors, but not a clear diagnosis. A closer look at topography, tomography, and anterior segment OCT epithelial mapping provided further information to make a decisive diagnosis of progressive keratoconus in the right eye.
This case illustrates that patients who see 20/20 at the phoropter can still have keratoconus. At 29, our patient was at an age where there is greater risk of progression,3 and her ocular allergies and family history elevate that risk. She was fortunate to be diagnosed and treated early in the course of her disease, while she was still correctible to 20/20.
Simply by following the KC clues that are hiding in plain sight, you can help patients like this one preserve their vision by referring them to a corneal specialist. If further testing confirms the patient has progressive KC, iLink® cross-linking could slow or halt its progression.
REFERENCES
- Kojima T, et al. Am J Ophthalmol 2020;215:127-34,
- Wang Y, et al. Am J Med Genet 2000;93(5):403-9.
- Ferdi AC, et al. Ophthalmology 2019;126(7):935-45.