Purpose:
Selective Laser Trabeculoplasty (SLT) is now widely used as a treatment option for primary open angle glaucoma (POAG) and ocular hypertension (OHT) either adjunctively or instead of medical treatment . The mechanism of action of SLT is thought to be via the laser effect on the trabecular outflow. However, the response to SLT is not universal and most studies have quoted response rate of between 60-70% in these groups of patient. We speculate that the level of intraocular pressure (IOP) response from SLT treatment may be related to the baseline tonographic outflow facilities.
Methods:
Retrospective observational study. All newly diagnosed patients with POAG/OHT attending our department have been offered to have baseline outflow facility measurement as part of their glaucoma investigations since June 2007. We identified patients who had baseline outflow facility and subsequent treatment with 360 degree SLT from our database. The notes of these patients were then retrieved and reviewed, only those with minimum of 3 month follow up were included in this analysis.
Results:
A total of 74 patients were identified to have baseline outflow facility, subsequent primary 360 degree SLT treatment, and minimum of 3 month follow up. Of which, 80 eyes of 48 patients were found to have reliable tonography and were included in this analysis.The mean baseline tonographic outflow facility were 0.11±0.06 µl/min/mmHg (Table) and IOP was 25.7±3.74 mmHg and following SLT treatment; 17.9 ± 3.4 (p<0.001*) at 3 month (n=80), 17.5 ± 3.3 (p<0.001*) at 6 month (n=49) and 17.5 ± 3.6 (p<0.001*) at 12 month(n=44). There is a strong negative correlation between baseline tonographic outflow facility and IOP reduction after 12 month follow up (p<0.001*)(Graph).
Conclusions:
Our observation revealed that baseline tonographic outflow facility can predict the the level of IOP reduction after SLT treatment. It suggests that the lower the baseline tonographic outflow facility, the higher IOP reduction at 12 month follow up would be expected.
Keywords: intraocular pressure • laser • outflow: trabecular meshwork