Impression cytology of the conjunctival epithelium in patients with chronic renal failure

Aims-To assess ocular surface changes in patients with chronic renal failur e (CRF), to compare the results with the degree of corneo-conjunctival calc ium deposits, and to determine whether precipitation of calcium salts predi sposes ocular surface modifications. Methods-Impression cytology from 50 CRF patients on regular haemodialysis a nd 22 age and sex matched control subjects were studied. Specimens were obt ained from the temporal bulbar conjunctiva using cellulose acetate filter p aper. The samples were fixed in 95% ethanol, stained with the periodic acid Schiff (PAS) stain, and evaluated by light microscopy and were graded by a masked observer. Corneo-conjunctival calcification was graded by the Porte r and Crombie classification. Results-In the study group, three patients (6%) disclosed grade 0, 14 patie nts (28%) grade 1, and 33 patients (66%) grade 2-3 cytological changes. The re was a statistically significant difference between the patient and the c ontrol groups (p= 0.0007), but no correlation could be found between the im pression cytology grades and the calcium deposit grades (p=0.62). Conclusion-The ocular surfaces of CRF patients differ significantly fi om t hose of normal individuals, and it can be detected using impression cytolog y. These data suggest that the severity of conjunctival changes are not rel ated to the presence or extent of calcium deposition.