Ocular surface disorders and tear function changes in patients with chronic renal failure

BACKGROUND: Ocular surface changes, mainly squamous metaplasia of the conjunctival epithelium and corneoconjunctival calcification of unknown etiology, may develop in patients with chronic renal failure undergoing hemodialysis. An association between squamous metaplasia and corneoconjunctival calcification has been suggested. The purpose of this study was to investigate the relation between ocular surface disorders and tear function changes in patients with chronic renal failure undergoing hemodialysis. METHODS: In this prospective case-control study, 42 patients with chronic renal failure and 20 age- and sex-matched control subjects underwent full ophthalmologic examination, tear function tests (including Schirmer's test, tear film break-up time [BUT] test and rose bengal staining) and impression cytology to determine the degree of conjunctival squamous metaplasia. They also responded to a questionnaire regarding subjective ocular complaints. Corneoconjunctival calcification was graded on a scale of 0 to 5 according to the system proposed by Porter and Crombie. Impression cytology samples were graded on scale of 0 to 3 according to the Nelson classification. The relation between ocular surface disorders and tear function changes was evaluated. RESULTS: Of the 42 patients, 12 (28%) had grade 0 calcification, 10 (24%) had grade 1, 14 (33%) had grade 2, and 6 (14%) had grade 3 or higher. Four patients (10%) had grade 0 squamous metaplasia, 22 (52%) had grade 1, 12 (28%) had grade 2, and 4 (10%) had grade 3. The difference between the patient and control subjects in squamous metaplasia grades and corneoconjunctival calcification grades was statistically significant (p < 0.001 and p = 0.022 respectively). Abnormal tear film BUT (p = 0.002) and abnormal rose bengal staining (p = 0.023) were significantly more frequent in the patient group than in the control group. The grade of conjunctival squamous metaplasia was correlated with abnormal rose bengal staining (tau = 0.79, p < 0.001) and with the existence of subjective ocular complaints (tau = 0.32, p = 0.026). There was no correlation between corneoconjunctival calcification and tear function changes. INTERPRETATION: Abnormal rose bengal staining and the presence of subjective ocular complaints may be used as follow-up criteria for ocular surface disorders in patients with chronic renal failure regularly undergoing hemodialysis.