Direct Selective Laser Trabeculoplasty: An Effective Iop-Lowering Therapy For Primary Angle Closure Disease

Trans-limbal direct selective laser trabeculoplasty (DSLT) (Alcon, Fort Worth, Texas, USA) is a new laser delivery method that targets the trabecular meshwork outflow pathway through the perilimbal sclera. This overcomes some limitations of SLT such as the need for a goniolens and the ability to overcome anatomical obstacles such as narrow angles. We aimed to measure the 6- month efficacy of DSLT in reducing intraocular pressure (IOP) in eyes with primary angle closure (PAC) or primary angle closure glaucoma (PACG). 

All patients were recruited from Singapore National Eye Centre, a tertiary care hospital in Singapore. 

Patients with a baseline diagnosis of PAC and PACG who had received prior laser iridotomy or cataract surgery were recruited in this prospective single-arm pilot trial. Post washout, they had to achieve an IOP ≥ 22mmHg but ≤ 35mmHg. 1 eye per subject received DSLT: 120 shots delivered over 2 seconds at an energy setting of 2.2mJ, circumferentially over 360 degrees. Patients were followed up at week 1, month 2, 4 and 6. All patients were prescribed nepafenac four times a day for a week after laser treatment.

Mean age was 63.7±9.3 years. 9 eyes had PAC, 12 had PACG. 19 eyes were on eye drops prior to DSLT treatment with a mean IOP at baseline of 24.0±2.7mmHg. 2 were treatment naïve whilst the rest were on either 1 or 2 eye drops. 4 eyes had prior cataract surgery.

2 months after treatment, mean IOP was 18.1±3.4mmHg (-24.6%,p<0.001). Month 4, mean IOP was 17.1±3.3mmHg (-28.8%;p<0.001) and Month 6, mean IOP was 15.3±2.5mmHg (-36.3%,p<0.001).

At Month 6, 16 patients (76%) achieved complete success (no medications) with an average IOP lowering of 8.3mmHg from baseline. 8 patients (38%) required re-treatment with DSLT by month 4, of which 4 did not require further treatment or medications; 4 were re-started on 1 eye drop. No serious events were noted. 

Automated DSLT is an effective and safe non-contact modality for reducing IOP in PAC and PACG eyes, with a significant proportion of eyes achieving good medication-free IOP at 6 months.