Keratoconus Risk Higher for Young Adults With Sleep Apnea, High Astigmatism

Western Australia has one of the highest prevalences (3.4%) and incidences (2.2%) of keratoconus in young adults in the world, according to findings published in Ophthalmology. Researchers say the study emphasizes the importance of early keratoconus screening for individuals aged 20 to 28 years old. A study shows these patients are more likely to display a number of clinical findings years before keratoconus development, including short axial lengths and myopia. The researchers also note an association between keratoconus and obstructive sleep apnea.

The researchers used data from participants of The Raine Study, a multi-generational cohort study based in Perth, Australia. Specifically, they collected data from the Gen2 cohort, with 20-year (conducted 2010-2012) and 28-year (2018-2020) follow-up visits.. The study reviewed the participants’ ophthalmic examinations, including Scheimpflug imaging and completed a health questionnaire. A Belin/Ambrosio Enhanced Ectasia Display (BAD-D) score of at least 2.6 was used to define tomographic evidence of keratoconus. Corneal specialists further analyzed all scans with a BAD-D of 2.6 or higher for false positives. 

Using these results, the researchers were able to identify potential ocular and nonocular risk factors at the 20-year followup, including the sun exposure-related variables serum 25-hydroxyvitamin D concentration [25(OH)D] — measured using liquid chromatography tandem mass spectrometry and deseasonalized for month of collection — and total conjunctival ultraviolet autofluorescence (CUVAF) in both eyes. 

The researchers also assessed apnea-hypopnea index (AHI, events/hour), minimum and mean peripheral capillary oxygen desaturation, and T90 (time where peripheral capillary oxygen saturation was <90%), measured at a sleep study performed at the 22-year followup. 

The study shows, of the 755 participants at the 28-year follow up included in the study, 26 (3.4%) were diagnosed with keratoconus. Compared with those without keratoconus, based on the BAD-D threshold of 2.6 at the 28-year followup, participants with keratoconus were more likely to be men (P =.045), have a shorter axial length (P <.001), have poorer visual acuity (P =.002), and have higher astigmatism (P <.001) and myopia (P =.01) on cycloplegic autorefraction. In addition, significant differences were identified in multiple parameters including keratometric and pachymetric indices on Scheimpflug imaging.

Imaging data was available for 669 participants at both the 20- and 28-year follow-up visits, after excluding 8 participants who were diagnosed with keratoconus at the 20-year follow up. Mean follow-up time was 8.3 years. From this group, 15 participants were identified as having a new onset of keratoconus (8 bilateral, 7 unilateral cases). Incidence of keratoconus spanning the 8 years was 2.2% (95% CI, 1.12-3.36).

“We did not identify any association between keratoconus and self-reports of allergic diseases (asthma, allergic rhinitis or ocular allergies) or body mass index,” the researchers explain.

The study also confirmed associations between keratoconus and mild obstructive sleep apnea (OSA, P =.09), moderate OSA (P =.02), and severe OSA (P =.007) via analysis of AHI. The researchers highlight that the study’s findings should inform clinical decision making depending on patients’ risk factors.