Uveo-scleral outflow pathways after ultrasonic cyclocoagulation in refractory glaucoma: an anterior segment optical coherence tomography and in vivo confocal study

AIMS: To evaluate, using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM), the uveo-scleral aqueous humour (AH) outflow pathways after ultrasonic circular cyclocoagulation (UCCC). METHODS: Forty-four patients with refractory glaucoma underwent 4 or 6 s UCCC (group 1, 24 eyes; group 2, 20 eyes). UCCC was successful when the preoperative intraocular pressure (IOP) reduced by one-third. AS-OCT and IVCM were performed at baseline and at month 1 to evaluate the sclera and conjunctiva. The main outcomes were mean intra-scleral hyporeflective spaces area (MIHSA: mm2) at AS-OCT, mean density and area of conjunctival microcysts (MMD: cysts/mm2; MMA: µm2) at IVCM. The relations between MIHSA, MMA and MMD with IOP were analysed. RESULTS: Mean baseline IOP was 26.9±2.8 mm Hg in group 1 and 27.5±4.0 in group 2. Intra-scleral hyporeflective spaces and microcysts were observed in both groups, without significant differences in MIHSA, MMA and MMD. At month 1, UCCC was successful in 63.6% of patients (41.6% in group 1, 80% in group 2), and IOP reduced to 18.8±3.2 (30.1%) and 17.1±2.7 mm Hg (38.7%), respectively (p<0.001). MIHSA showed a twofold and threefold increase in group 1 and 2 (p<0.05), with a significant difference between groups (p<0.05). MMA and MMD increased in both groups (p<0.05), with values higher in group 2 (p<0.05). Significant relations were found between MIHSA and IOP in both groups (p<0.01). CONCLUSIONS: UCCC induced anatomical modifications of sclera and conjunctiva, which suggested that the trans-scleral AH outflow enhancement is one of the possible mechanisms exploited by ultrasounds to reduce IOP. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.