Incidence of keratoconus following allergic conjunctivitis: a multicenter retrospective cohort study using a U.S....

To evaluate the risk of keratoconus and related corneal complications in patients with allergic conjunctivitis, using a large, multicenter real-world dataset.

A retrospective cohort study was conducted utilizing the TriNetX US Collaborative Network. Patients aged 5-25 years with allergic conjunctivitis were matched to patients with non-allergic conjunctivitis using 1:1 propensity score matching. The primary outcome was incident keratoconus. Secondary outcomes included corneal topography, advanced corneal diagnostic procedures (e.g., pachymetry and scanning computerized ophthalmic imaging), keratoconus-specific contact lens fitting, corneal cross-linking, keratoplasty, recurrent corneal erosion, and acute corneal hydrops. Survival analysis was performed using Kaplan-Meier curves and Cox proportional hazards models.

After matching, 174,443 patients were included in each cohort. Allergic conjunctivitis was associated with a significantly increased risk of keratoconus (HR 1.6; 95 % CI, 1.18-2.18; p = 0.0024), with 118 patients developing the condition versus 62 in the control group. Corneal erosion was significantly associated with allergic conjunctivitis as well with HR of 1.87 (95 % CI 1.05-3.34; p = 0.0305). Corneal topography and advanced corneal diagnostic procedures were also more frequent in the allergic group with HRs of 1.94 (95 % CI 1.58-2.38; p < 0.0001) and 2.05 (95 % CI 1.74-2.4; p < 0.0001), respectively.

Allergic conjunctivitis is associated with an elevated risk of keratoconus and an increased need for corneal diagnostic evaluation in children and young adults. These findings support the implementation of enhanced screening and proactive allergy management in this population.