The Prevalence of Lower Eyelid Fornix Fat Prolapse: A Diagnostic Measure of Involutional Entropion

Purpose: In our experience, lower lid involutional entropion is commonly associated with inferior fornix fat prolapse and non‑eversion of the tarsal plate. We aimed to assess the prevalence of this sign as an early diagnostic indicator of lower lid involutional entropion in symptomatic and control groups. Methods: Prospective, comparative, observational case series. Fornix fat prolapse and failure of tarsal eversion in patients with involutional entropion were studied. Fornix fat prolapse was assessed by pulling the lower lid margin to the inferior orbital rim and comparing the meniscus of the protruding fat. The absence of tarsal eversion and lid laxity were also assessed. Patients were reassessed following correction using radiofrequency entropion surgery. Results: Sixty eyes of 50 Caucasian patients with involutional entropion underwent entropion correction. Fornix fat prolapse was found preoperatively in 83.3% (50 eyes), with complete reversal of fat prolapse in 76% (38 eyes) over a mean follow‑up of 18.9 months, after successful surgery (P < 0.01). None of the 100 eyes (50 patients) in the control group showed fornix fat prolapse or absence of lower lid tarsal eversion (P < 0.01). Conclusion: There is high prevalence of fornix fat prolapse and failure of tarsal eversion (BB sign) in involutional entropion, with reversal after successful eyelid surgery. The absence of fornix fat prolapse in normal controls suggests that this is an important, underlying anatomical etiology, with diagnostic and prognostic value.