Natural Course In Fellow Eyes Of Patients With Unilateral Keratoconus

To evaluate the natural progression of corneal morphology and biomechanics in fellow eyes of unilateral keratoconus patients through mid-to-long-term follow-up.

Single-center retrospective cohort study.

Sixty-six fellow eyes with pre-clinical keratoconus were followed for 34.24±22.59 months. Progression was defined as: thinnest corneal thickness reduction ≥20μm, maximum anterior curvature increase ≥1.5D, or BAD-D increase ≥0.42. Kaplan-Meier analysis calculated cumulative progression rates.

21.21% of eyes progressed during follow-up. Cumulative progression rates reached 15.46% at 36 months and 37.16% at 60 months. BAD-D showed the highest 60-month progression rate (30.38%). Most Pentacam parameters significantly worsened at final follow-up, while biomechanical parameters showed heterogeneous evolution patterns. The progression group demonstrated significantly greater worsening in spherical equivalent, maximum anterior curvature, anterior/posterior surface elevations, PPIave, BAD-D, and TBI. No significant differences were found between forme fruste and subclinical keratoconus groups.

Fellow eyes in unilateral keratoconus represent high-risk entities with 37.16% 5-year progression risk. BAD-D, PPIave, and TBI changes are key predictors for progression risk. Lifelong regular monitoring incorporating both topographic and biomechanical examinations is recommended for all fellow eyes.