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Michael Rosman, Alon Skaat, Sung Chul Park, Jason L Chien, Mark Ghassibi, Siddarth Rathi, Robert Ritch, Jeffrey M Liebmann; Cyclopentolate 1% Decreases Schlemm’s Canal Dimension in Normal Subjects. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4986.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the in vivo effect of cyclopentolate 1%, an anticholinergic agent, on the structure of Schlemm’s canal (SC) in normal eyes.
Healthy subjects with no ocular or systemic diseases known to affect the iridocorneal angle or trabecular aqueous outflow structures were prospectively recruited. Eighty-one serial horizontal enhanced depth imaging (EDI) optical coherence tomography (OCT) B-scans (interval between B-scans, ~35 µm) of the nasal corneoscleral limbal area were obtained before and 1 hour after cyclopentolate 1% administration. With conjunctival vessels and iris anatomy as landmarks, the same limbal area was scanned before and after cyclopentolate administration. The SC cross-sectional area was measured in each selected EDI OCT B-scan. After three-dimensional reconstruction, SC volume was determined.
Eight eyes (5 men, 3 women; mean age, 27±4 years) were included. Mean intraocular pressure was 13.4±1.3 mmHg before and 13.8±1.1 mmHg after cyclopentolate administration (p=0.17). All patients developed mydriasis after administration. Schlemm’s canal was continuous in the scanned area in all eyes and was successfully delineated and reconstructed 3-dimensionally pre- and post cyclopentolate administration. Mean SC cross-sectional area decreased after cyclopentolate administration (6855±658µm2 vs. 5848±791µm2; p<0.01). Mean SC volume also decreased (11852607±1145016 µm3 vs. 10117350±1368343 µm3; p<0.01).
Cyclopentolate 1% decreases SC dimension in healthy subjects. Whether this results from a direct anticholinergic effect on the canal or secondarily from its effect on the ciliary musculature and/or decreased trabecular outflow remains to be determined. EDI OCT of Schlemm’s canal may prove useful in evaluating the mechanisms of action of pharmacologic agents in glaucoma.
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