More People With Keratoconus Than Originally Thought
Prevalence of Keratoconus Based on Scheimpflug Imaging
- Using Scheimpflug imaging, the authors determined the prevalence of keratoconus in a young adult population of primarily Caucasian Australians to be 1 in 84, significantly higher than previously reported in population studies.
- The authors suggest that more frequent screening of young adults would allow for earlier treatment (corneal cross-linking).
PURPOSE
To describe the prevalence and systemic associations of keratoconus in young adults in Perth, Western Australia.
DESIGN
Cross-sectional study PARTICIPANTS: 1,259 participants, aged 20 years old METHODS: The Raine Study is a multi-generational, longitudinal cohort study based in Perth, Western Australia. This study represents a cross-sectional analysis of the birth cohort, when they returned for their 20-year follow-up. Participants underwent a detailed ophthalmic examination, including visual acuity assessment and Scheimpflug imaging using the Pentacam (Oculus, Germany) and completed a health questionnaire. Keratoconus was defined as a BAD-D score of ≥2.6 in either eye based on Pentacam imaging.
MAIN OUTCOME MEASURES
Prevalence of keratoconus in this cohort.
RESULTS
Of the 1,259 participants, 50.8% were female, and 85.7% were Caucasian. Fifteen participants had keratoconus in at least one eye, giving a prevalence of 1.2% (95% confidence interval, CI [0.7, 1.9]), or 1 in 84. There was a significant difference in the best corrected visual acuity (0.01 vs -0.05 logMAR, p=0.007), cylinder (1.25 vs 0.25 diopters cylinder, p<0.001) and spherical equivalent (-1.42 vs -0.50 diopters sphere, p=0.02) on objective refraction, mean keratometry of the steep meridian (45.19 vs 43.76 diopters, p<0.001) and mean corneal thickness at the thinnest point (475 vs 536μm, p<0.001) between those with and without keratoconus. Keratoconus was associated with regular cigarette smoking (38.5% vs 14.6%, p=0.04), but no association with sex, race, body mass index, use of spectacles or contact lenses, history of allergic eye disease or pregnancy was observed.
CONCLUSION
The prevalence of keratoconus in our Australian population-based study of 20-year-old adults was 1.2% (95% CI [0.7, 1.9]), or 1 in 84, which is one of the highest reported in the world. This has important implications for screening individuals at a younger age so treatment can be initiated before disease progression.
Additional Info
Disclosure statements are available on the authors’ profiles:
Despite a number of studies to date, the prevalence of keratoconus is not known with certainty. A variety of measures for keratoconus have been used to study a range of populations. Chan et al report the prevalence of keratoconus in their Australian population-based study of 20-year-old adults to be 1.2% (95% CI, 0.7–1.9), or 1 in 84; this prevalence is one of the highest reported globally. The Raine Study utilized a well-characterized, multigenerational, longitudinal cohort from Western Australia. The authors evaluated Scheimpflug imaging with the Pentacam (Oculus, Germany) from 1259 participants aged 20 years old. A BAD-D score of ≥2.6 (sensitivity of 80%) in either eye was used to define keratoconus. The BAD-D uses the anterior and posterior elevation, pachymetric data, an “enhanced reference surface,” Kmax, and ARTmax.
Of the 1259 participants in the study, 50.8% were female, and 85.7% were Caucasian. There was no association with sex, race, body mass index, use of spectacles or contact lenses, history of allergic eye disease, or pregnancy. Regular cigarette smoking (38.5% vs 14.6%; P = .04), however, was associated with keratoconus. Interestingly, no patient had had crosslinking as the data were collected between 2010 and 2012 (before the procedure was widely available in Western Australia). The study population was predominately Caucasian, and the authors acknowledge that the BAD-D score is usually insufficient on its own for the diagnosis of keratoconus because the global prevalence of keratoconus remains unknown. As keratoconus can progress reducing vision, their data highlight that screening may be needed at a younger age. Earlier detection of keratoconus and its progression may allow for crosslinking to stabilize the cornea.