The importance of checking for keratoconus prior to starting myopia management

Patient A, a 14-year-old male, presented to clinic for an annual eye examination with subjective blur at distance in the left eye. The patient’s parent voiced concerns about a potential increase in nearsightedness and was interested in learning more about myopia management.  

Comparison of the axial length measurements with gender and age-matched growth curves¹ indicated that the axial length corresponded to the 70th percentile, associated with an ~60% chance of myopia as an adult.  

Keratoconus is often diagnosed and monitored using corneal topography, an imaging tool that maps the corneal surface to detect irregularities such as asymmetric steepening or cone-shaped distortions characteristic of keratoconus.²

Patient A's corneal topography were obtained using the Topcon MYAH and are as follows:

Patient A’s corneal topography findings were suggestive of bilateral keratoconus, more advanced in the left eye. Of note is the variable corneal astigmatism between 3mm, 5mm and 7mm zones, many corneal indices falling outside the normal range, the compatibility of the cornea with keratoconus metrics, and a longer axial length in the left eye. Patient A had surprisingly small photopic pupils (3.7mm) which may explain his limited symptoms. The patient was referred for cross-linking treatment in both eyes. Regular follow-up examinations demonstrated topographic stability and the patient’s refractive error and axial length are being monitored, but myopia management does not seem appropriate at this stage. 

Prompted by these findings, Patient A's asymptomatic younger sibling, Patient B, a 12-year-old male, underwent a comprehensive ocular examination. His ocular history was unremarkable, with uncorrected visual acuities of 20/20 OD and 20/20 OS. However, there was significantly more corneal astigmatism in the right eye than the left eye. Corneal topography confirmed keratoconus in the right eye. He was also referred for cross-linking treatment and continues regular monitoring.

This case highlights the importance of diagnostic screening for keratoconus, including in asymptomatic individuals and myopia management candidates. Screening with a device that collects topography, axial length, and pupil data is important for developing a full clinical picture and differentiating between progressive myopia due to increased axial length, keratoconus, or a combination of both. Prompt detection allows for early intervention with corneal cross-linking, which is critical in preventing/minimising disease progression and preserving long-term visual health. Comprehensive assessment is pivotal for diagnosing keratoconus in both symptomatic and asymptomatic individuals, particularly in familial cases. The successful outcomes from this case following corneal collagen cross-linking underscore the potential benefits of early intervention in preserving vision and improving prognosis. Therefore, proactive diagnostic screening for keratoconus is imperative for optimising patient outcomes and enhancing quality of life.