Scanning electron microscopy applied to impression cytology for conjunctival damage from glaucoma therapy

To apply scanning electron microscopy to impression cytology (IC) to evaluate conjunctival damage in patients undergoing topical glaucoma therapy.

All patients undergoing glaucoma therapy and without ocular surface disorders between September 2012 and January 2013 were enrolled. An age- and gender-matched group without glaucoma served as the control group. Conjunctival epithelium was evaluated with the ferning test (FT), impression cytology with light optic microscopy (ICOM), and impression cytology with scanning electron microscopy (ICSEM).

Twenty patients (40 eyes; 11 men and 9 women, mean age 59.9 ± 11 years) constituted the treated group. The mean duration of glaucoma therapy was 25.5 ± 13.8 months (range, 6-48 months). The mean FT, ICOM, and ICSEM grades were 2.52 ± 0.5, 2.52 ± 0.6, and 2.55 ± 0.7, respectively. Treatment duration was not significantly correlated with FT/IC grade (P = 0.1), whereas it was significantly correlated with microvilli count at ICSEM (P = 0.01). The mean FT, ICOM, and ICSEM grades were significantly lower in the control group (40 eyes; 11 men and 9 women, mean age 61.1 ± 7.12 years) than in the treated group (1.22 ± 0.4, 1.25 ± 0.4 and 1.15 ± 0.3, respectively, P < 0.001).

The FT, ICOM, and ICSEM grades were lower in eyes undergoing glaucoma therapy than in control eyes. Treatment duration was significantly associated with a reduced microvilli count at ICSEM, but not with FT or ICOM grades. Reduction of microvilli could be the first sign of cellular damage during chronic glaucoma therapy.