Diagnostic Yield of Keratoconus Among Patients Presenting with Astigmatism≥ 1D at A Tertiary Eye Hospital in Uganda

Purpose To determine the diagnostic yield of keratoconus and associated factors among patients with astigmatism attending a tertiary eye hospital in Kampala, Uganda. Design This was a prospective cross-sectional study. Subjects A total of 252 patients aged ≥12 years with astigmatism (≥1.00 D) attending Georgina Eye Hospital, Kampala, between December 2022 and May 2023 were recruited for the study. Patients with prior ocular trauma or surgery were excluded. Methods All systematically selected participants that consented/assented underwent detailed systemic and ophthalmic evaluation. Keratoconus diagnosis was confirmed using Scheimpflug imaging reviewed by 2 corneal specialists. The diagnostic yield of keratoconus was estimated as proportions with 95% confidence intervals, stratified by age group. Associated factors were assessed using modified Poisson regression. Results A total of 252 patients (52.0% male, 48.0% female) were enrolled. A majority (52.0%) were younger than 25 years, and 8.3% were above 50 years. Keratoconus was diagnosed in 105 [41.7% (95% CI: 35.7-47.9)] participants, majority of whom were unilaterally affected: 69(65.7%). Among keratoconus cases (n=105), allergic conjunctivitis was present in 78.1% versus 60.5% in non-keratoconus patients; frequent eye rubbing in 60.0% versus 15.0%; and contact lens use in 31.4% versus 2.7%. Multivariable analysis revealed significant associations with frequent eye rubbing (aPR = 2.76, 95% CI: 1.72-4.41, p<0.001) and contact lens use (aPR = 1.90, 95% CI: 1.49-2.41, p<0.001). Conclusions Approximately 4 in every 10 patients with refractive astigmatism ≥1.00 D presenting to a tertiary eye hospital had keratoconus, confirming a high clinic-based diagnostic yield in this high-risk population. The associations with eye rubbing and contact lens use are consistent with existing literature and should be interpreted as clinical correlates rather than established causal risk factors.