Changes of bilateral tear film stability and corneal nerve in patients with unilateral neurotrophic keratitis

Objective : To observe the stability of the tear film bilaterally in patients with unilateral neurotrophic keratitis and the changes in corneal nerve and immune cells under confocal microscopy. Methods : Prospective cross-sectional study including 63 patients with confirmed neurotrophic keratitis (NK) and 40 normal controls of similar sex and age, the NK patients were divided into stage 1 and stage 2 according to the severity of the disease. The tear meniscus height (TMH), first non-invasive tear film break-up time (NIBUT-f), and corneal fluorescence staining were examined. Corneal sensitivity was accessed by Cochet Bonnet esthesiometer. The corneal subbasal plexus (SNP) and dendritic cells (DC) were scanned by in vivo confocal microscopy (IVCM), and SNP was analyzed using the fully automated corneal nerve analysis software “ACCmetric”. Results : Eyes with NK stage 2 showed worse performance in TMH, NIBUT-f, corneal fluorescein staining score, cornealsensitivity examination, SNP parameters, and DC density compared to NK stage 1 (all P < 0.001). And contralateral eyes of NK patients had significantly shorter NIBUT-f and significantly increased dendritic cell density compared to controls ( P < 0.001). Conclusion : The contralateral eyes of NK patients are more prone to dry eye signs than normal subjects and should be attended to and treated promptly. Increased numbers of dendritic cells in the contralateral eyes of NK patients suggest bilateral immune alterations in unilateral disease.