Trabeculectomy for normal tension glaucoma
Reviewed by Jonathan Chan

This is a retrospective consecutive, non-comparative case series of 131 eyes of 98 patients undergoing trabeculectomy between 2007 and 2013 in a normal tension glaucoma (NTG) clinic. Assessment of the clinical outcomes include intraocular pressures (IOP) reduction, bleb formation, final visual acuity, evidence of glaucoma progression, postoperative complications and further surgical intervention. Surgical failure was defined as a failure to meet specified IOP-related criteria, the need to undergo further glaucoma surgery for raised intraocular pressure or loss of light perception vision. A further analysis was also performed which considered failure as glaucoma progression following surgery. The outcomes were evaluated using the Kaplan-Meier life-table analysis. The criteria required for a diagnosis of NTG to be made included: 1) mean untreated IOP of <21mmHg from hourly diurnal phasing prior to commencing any IOP lowering treatment, with no individual IOP exceeding 21mmHg; 2) the presence of characteristic glaucomatous optic disc changes; 3) field defect characteristics of nerve fibre layer loss with at least one locus of a central 24° field depressed by >10 dB; 4) open drainage angles of gonioscopy and 5) no other cause identified for the visual loss.
The standard surgical techniques were performed by the use of a fornix-base conjunctival peritomy, adjunctive use of mitomycin-C in the subconjuctival space and three partial thickness releasable 10/0 nylon sutures to the scleral flat with the aim of observing no aqueous flow at the end of the procedure when checked with 2% fluorescein. The cumulative percentages of unqualified success as defined by a ≥30% reduction of IOP from baseline preoperative maximum at one, two, three and four years after surgery were 91.1%, 74.1%, 64.8% and 62.1% respectively. At two years of follow-up there was no significant association between previous cataract surgery or ethnicity and failure. Cumulative percentages of unqualified success at four years after surgery as defined by a filtering trabeculectomy bleb or absence of glaucoma progression were 91.6% and 92.3% respectively. Postoperative complications such as early (2.3%) and late (0.8%) hypotony were significantly lower than suggested by the current literature. The authors concluded that trabeculectomy in NTG patients undertaken using contemporary surgical techniques and intensive postoperative management is associated with more successful long-term outcomes and fewer complications than the currently available literature suggests. The limitations of the study include: 1) retrospective nature of the data collection; 2) limited by the reduced numbers of eye studies at the later time and 3) potential impact of the intensive postoperative regime for the quality of life parameters for patients. 

Trabeculectomy for normal tension glaucoma: outcomes using the Moorfields safer surgery technique.
Jayaram H, Strouthidis NG, Kamal DS.
BRITISH JOURNAL OF OPHTHALMOLOGY
2016;100:332-8.