Relationship between ocular surface pain and corneal nerve loss in dry eye diabetics: a cross-sectional study in Shenyang, China

BACKGROUND: Diabetes mellitus has been associated with increased dry eye disease (DED) and exacerbates DED pathology. OBJECTIVE: To investigate the potential relationship between corneal nerve loss and ocular pain among diabetic patients with dry eye (DE). DESIGN: A cross-sectional study. SETTING: He Eye Specialist Hospital, Shenyang, China. PARTICIPANTS: This study recruited 124 eyes of 62 diabetic patients diagnosed with DED between August and October 2022. MAIN OUTCOME MEASURES: Best-corrected visual acuity, intraocular pressure, non-invasive tear breakup time, tear meniscus height, tear film lipid layer, conjunctival hyperaemia (redness score), conjunctivocorneal epithelial staining (CS score), central corneal sensitivity and vitro confocal corneal microscopy was assessed in all subjects. The Ocular Surface Disease Index Questionnaire assessed DE symptoms and ocular pain. RESULTS: The study’s final analysis included 26 patients (52 eyes) without ocular pain and 36 patients (72 eyes) with ocular pain. The corneal nerve fibre density (CNFD), corneal nerve branch density (CNBD) and corneal nerve fibre length (CNFL) in patients with ocular pain were significantly lower than those without (p<0.001, p=0.004, and p<0.001, respectively). CNFD, CNBD and CNFL negatively correlated with ocular pain (r=−0.385, r=−0.260, r=−0.358, respectively). Moreover, CNFD, CNBD and CNFL have a significant (p<0.05) positive correlation with corneal sensitivity (r=0.523, r=0.330, r=0.421, respectively). CONCLUSIONS: Corneal nerve loss was associated with ocular pain and decreased corneal sensitivity in diabetic patients with DE. Further studies into the neurological role of ocular surface diseases can elaborate diagnostics, prognosis and treatment of diabetic patients with DE. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (NCT05193331).