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Alon Skaat, Sung Chul Park, Ruojin Ren, Jeffrey M Liebmann, Robert Ritch; Pilocarpine Expands Schlemm’s Canal in Normal Subjects. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5682.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the in vivo effect of pilocarpine on the structure of Schlemm’s canal in normal eyes.
Serial horizontal enhanced depth imaging optical coherence tomography (EDI OCT) B-scans of the nasal corneoscleral limbal area were obtained before and one hour after administration of pilocarpine 1% in normal subjects (50 B-scans; interval between scans, ~35 µm). With conjunctival vessels and iris anatomy as landmarks, the same limbal area was scanned before and after pilocarpine administration. Schlemm’s canal was manually delineated in each EDI OCT B-scan. After three-dimensional reconstruction, Schlemm’s canal volume was determined.
Nine normal eyes (9 subjects; mean age, 32±6 years) were included. The right eye was tested in all subjects. Schlemm’s canal was continuous in the scanned area in all eyes and was successfully delineated (Fig 1) and reconstructed 3-dimensionally. Following pilocarpine 1% administration, mean Schlemm’s canal volume increased by more than 60% (from 15556563±5179705 µm3 to 25501096±11844193 µm3, p=0.04).
Pilocarpine expands Schlemm’s canal. Whether this results from a direct pilocarpine effect on the canal or secondarily from its effect on the ciliary musculature and/or increased trabecular outflow remains to be determined. EDI OCT of Schlemm’s canal may prove useful in evaluating the mechanisms of action of pharmacologic agents and surgical devices in glaucoma.
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