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SLT may further reduce IOP in eyes with primary open angle glaucoma

Study shows that 360° SLT reduced intermediate-term IOP more effectively than 180° SLT.

Issue: May 2012

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Maho Shibata

Two forms of selective laser trabeculoplasty proved effective as an adjunct treatment for primary open-angle glaucoma and pseudoexfoliation glaucoma, a study found.

“SLT is effective in further lowering IOP in patients under anti-glaucoma medical treatment,” Maho Shibata, MD, the corresponding author, said in an email interview. “In addition, 360° SLT is more effective than 180° SLT; 360° SLT may be one of the choices of adjunctive treatment in patients whose IOP cannot be controlled by medical treatment.”

SLT was performed as an adjunctive procedure in patients already taking anti-glaucoma medications.

The study was published in the Journal of Glaucoma.

Patients and methods

The retrospective study included 69 eyes of 54 patients; 35 eyes of 29 patients underwent 180° SLT and 34 eyes of 25 patients underwent 360° SLT. Mean patient age was 70.2 years in the 180° SLT group and 66.4 years in the 360° SLT group.

“The decision of assignment to 180° and 360° subgroups was made by the treating physician without randomization,” Dr. Shibata said.

All patients were treated with the Coherent Selecta 7000 laser (Lumenis). The pigmented trabecular meshwork was targeted; non-overlapping laser spots were placed in the inferior 180° of the trabecular meshwork or the entire 360° of meshwork.

Initial laser energy was 0.8 mJ and was increased by 0.1 mJ increments until bubble formation occurred. Treatment was continued at the minimum energy level necessary for bubble formation.

After treatment, patients were evaluated at 1 week, 1 month, 3 months, 6 months and at subsequent 3-month intervals. Average follow-up was 19.5 months for the 180° SLT group and 17.9 months for the 360° SLT group.

Goldmann applanation tonometry was used to measure IOP at each follow-up visit.

Success was defined as an IOP reduction of at least 20% without additional medications or surgery.

Results and conclusions

Before treatment, mean IOP was 19.5 mm Hg in the 180° SLT group and 21 mm Hg in the 360° SLT group. The difference was not statistically significant.

The mean number of glaucoma medications used before treatment was three for patients in the 180° SLT group and 2.8 for patients in the 360° SLT group. The difference was not statistically significant.

Study results showed that 6 months after treatment, IOP was reduced 2.6 mm Hg in the 180° SLT group and 5.6 mm Hg in the 360° SLT group; the between-group difference was significant (P < .05).

In the 180° SLT group, mean IOP at 1 month and 18 months was significantly lower than pre-treatment IOP (P < .05). In the 360° SLT group, mean IOP at every follow-up point was lower than pre-treatment IOP (P < .01).

Pre-treatment IOP correlated strongly with IOP reduction rate in the 360° SLT group.

Success rates at 1 year were 46% in the 360° SLT group and 25% in the 180° SLT group. Two-year success rates were 29% in the 360° SLT group and 22% in the 180° SLT group. The between-group difference in long-term success approached statistical significance (P = .05).

“Higher success rates of 360° SLT … might be because of its higher IOP reduction rate,” Dr. Shibata said.

Dr. Shibata and colleagues hypothesized that the greater IOP reduction of 360° SLT may have resulted in part from an increase in cytokines released by trabecular meshwork endothelial cells.

“As previous reports described, 360° treatment may allow for increased cytokine release compared with 180° treatment, which may result in enhanced IOP reduction,” Dr. Shibata said.

Shortcomings of the study included the retrospective design and small patient sample, she said. – by Matt Hasson

Reference:

• Shibata M, Sugiyama T, Ishida O, et al. Clinical results of selective laser trabeculoplasty in open-angle glaucoma in Japanese eyes: comparison of 180 degree with 360 degree SLT. J Glaucoma. 2012;21(1):17-21.

For more information:

• Maho Shibata, MD, can be reached at Department of Ophthalmology, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki-shi, Osaka, 569-8686 Japan; email: mahosaru@iris.eonet.ne.jp.
• Disclosure: Dr. Shibata has no relevant financial disclosures.