GLAUCOMA SURGERY

Eight to 10 years after deep sclerectomy, patent decompression chambers in intrascleral space were maintained in most cases, and suprachoroidal aqueous flow was frequently detected on ultrasound examination, Pierre-Yves Santiago MD, of Clinique Sourdille, Nantes, France, told the XXX Congress of the ESCRS. But while the consistent finding of suprachoroidal outflow is intriguing, its significance is unclear, Dr Santiago said. “Subconjunctival filtration has long been considered the main IOP-lowering mechanism, in many cases diffusing posteriorly. Suprachoroidal outflow is often observed, but we are not sure if it is a mechanism or a consequence of IOP lowering.â€

The study, which also examined intraocular pressure (IOP), topical treatment requirements and re-operation rates, is thought to be the first 10-year study of filtration architecture following deep sclerectomy. Outcomes of patients with and without implants, and with and without anti-metabolite treatment were compared. Dr Santiago recommended further studies beyond the select group of patients he imaged, all of whom had successful procedures. Confirmation of suprachoroidal outflow as an IOP-lowering mechanism could lead to new filtration surgery approaches that are long-lasting and less prone to bleb-related failures and complications.

Long-term outcomes

Patients for the outcomes study were selected at random between February and June 2012. From these, a subset of patients with favourable outcomes were imaged to investigate the possible role of suprachoroidal outflow in IOP lowering, Dr Santiago said. In a comparison involving 47 eyes in 31 patients with a mean follow-up of 127 months, outcomes for those that received a hyaluronate implant at surgery were broadly similar to those that did not, though mean IOP was slightly lower while mean topical medications and re-operation rates were higher in the implant group. The 22 eyes in the implant group fell from mean IOP of 22.0 mmHg and 1.77 topical drugs pre-op to 13.8 mmHg and 0.84 topical drugs with four re-operations, or 18 per cent, at 132 months mean follow-up. The 25 eyes in the non-implant group fell from mean IOP of 22.3 mmHg and 1.12 topical drugs pre-op to 14.7 mmHg and 0.44 topical drugs with three re-operations, or 12 per cent, at 122.7 months follow-up, Dr Santiago reported.

Similarly, in a group of 54 eyes in 40 patients, all with hyaluronate implants operated by the same surgeon, and 14 treated with mitomycin-C and four with 5-flourouracil, outcomes were nearly identical in the anti-metabolites and non-anti-metabolite treated groups, Dr Santiago reported. Mean IOP fell from 24.3 mmHg and 1.6 mean topical treatments pre-op to 14.8 mmHg and 0.9 topical drugs at 101.5 months mean follow-up, with 26 per cent treated for cataracts, 11 per cent re-operated for glaucoma and 3.6 per cent receiving selective laser trabeculoplasty. “In summary these are satisfactory outcomes at 10 years,†Dr Santiago said. Medical treatments when necessary were about half pre-op levels, with the added advantage of achieving IOP control, with the need for re-operations due to uncontrolled pressure running 11 per cent to 14 per cent.

Suprachoroidal outflow

To illustrate the possible role of suprachoroidal outflow in IOP lowering, Dr Santiago randomly selected 21 eyes of 12 patients from those with favourable outcomes. Of these, 14 eyes had hyaluronate implants and nine were treated with anti-metabolites. Mean pre-op IOP of 20 mmHg and 2.0 topical treatments were reduced to 12.6 mmHg and 0.33 treatments at a mean follow-up of 108 months for the entire group. These patients were examined using 50 MHz ultrasound biomicroscopy probe. UBM is the only technology currently available capable of imaging deep scleral architecture and function, Dr Santiago said. Because ultrasound is dynamic, it makes static measurements difficult. Nonetheless, bleb and decompression chamber volumes were recorded, with a mean of 86.6 cubic mm for filtration blebs and 14.6 cubic mm for decompression chambers.

Dr Santiago also imaged suprachoroidal outflow channels and aqueous outflow, though it is sometimes difficult to do so. Of the 21 eyes, suprachoroidal outflow was definitely detected in 10, appeared probable in six and was definitely not present in five patients. But while it might be expected that adding suprachoroidal outflow to subconjunctival blebs and intrascleral channels would further reduce IOP, no correlation was found between IOP and the presence of suprachoroidal outflow, Dr Santiago reported.

Dr Santiago presented ultrasonograms of several cases with and without suprachoroidal flow, all of which had stable IOP for seven years or more, often in the 10 to 12 mmHg range. Indeed, 12 years after surgery, one patient had nearly identical pressure in both eyes with one showing clear suprachoroidal outflow and the other with no detectable flow. These results raise a question as to whether suprachoroidal outflow is a real outflow mechanism, or merely a consequence of surgically induced hypotony, he said.

Dr Santiago noted a similar question arising from studies of circular cyclocoagulation of the ciliary processes in rabbits. As the processes atrophy after treatment, uveoscleral gaps are created. “It was noticed on histological analysis, and in vivo we can see suprachoroidal outflow that can participate to lower IOP as a consequence of hypotony.†Since this is the first long-term investigation of filtration architecture with a 10-year follow-up, and the patient population was narrow, Dr Santiago recommended additional, broader studies.