Dr. Ganesh Venkataraman, Dr. Premanand Chandran, Dr. VINOTH ARUNACHALAM, Dr. Varsha Ramachandra
Aim:
To report the effectiveness of selective laser trabeculoplasty (SLT) in South Indian population Methods: Retrospective review of patients who underwent SLT between January 2015 and December 2016. Patients diagnosed with ocular hypertension (OHT), and primary open angle glaucoma (POAG) with mean deviation < -12dB were included. Primary outcome measures were intraocular pressure (IOP) and antiglaucoma medication (AGM). Success was defined as IOP reduction of atleast 20% from baseline.
Results:
The study included 103 eyes with OHT and 36 eyes with POAG. Mean age was 47.9 years. Mean IOP reduced from 22.4 to 17.3 mm Hg at 3 months, and 17.5 mm Hg at 6 and 12 months after SLT (P < 0.001). Mean number of AGM reduced from 0.8 to 0.04 at 1 year post SLT (p < 0.001). Success rate was 68% and 65% at 6 months and 1 year respectively. Conclusion:SLT reduces IOP significantly and is a promising treatment option for patients with OHT and mild to moderate open angle glaucoma.
Glaucoma, a optic neuropathy of multifactorial cause, is the leading cause of irreversible blindness. Intraocular pressure (IOP) is the only modifiable risk factor. Reduction of intraocular pressure is the mainstay of treatment, and that can be achieved by laser therapy, medical therapy and or surgery.
Selective laser trabeculoplasty has been in vogue from 2001. However it has not gained poplarity due to the laser being expensive in the developing countries and also due to negative social marketing and lack of data available in our population.
Aim:
To report the effectiveness of selective laser trabeculoplasty (SLT) in South Indian population
Methods:
This was a retrospective study conducted at Aravind Eye hospital, Coimbatore after clearance from Institutional review board. Case records of all patients who underwent SLT from Jan 2015 to December 2016 were reviewed.
Inclusion criteria:
- Ocular hypertension
- Mild to moderate degree primary open angle glaucoma
Exclusion criteria:
- Advanced open angle glaucoma and/or Split fixation seen on perimetry
- Secondary open angle glaucoma
- Previous glaucoma surgery
- Patients with less than 6 months follow up
The data collected was age, gender, best corrected visual acuity, baseline IOP, central corneal thickness, gonioscopy, diagnoses, number of anti-glaucoma medications, cup disc ratio and mean deviation on visual field. The visual acuity was checked with Snellen chart. Intraocular pressure was measured with Goldmann applanation tonometry and gonioscopy was assessed with four-mirror Sussman type goniolens. The visual field was evaluated with Humphrey’s perimetry using SITA-standard 24-2 strategy and optic disc changes with slit lamp biomicroscopy.
SLT technique:
A drop of Proparacaine (1%) was administered in the eye. Latina single-mirror gonio lens with coupling agent was placed in the eye. He-Ne laser aiming beam is focused on the entire trabecular meshwork. The laser energy was initially set at 0.8 mJ and laser pulse was delivered. If a cavitation bubble is not seen, the pulse energy was increased by increments of 0.1 mJ until bubble formation is seen. 80-100 shots were applied consecutively 360 degrees around the TM.
The postoperative data collected was IOP, number of anti-glaucoma medications and any adverse effects, if noted. The follow up visits were at 2 weeks, 6 weeks, 3 months, 6 months and 1 year post SLT.
Outcome measures:
- Comparison of IOP reduction in OHT vs POAG at 2 weeks, 6 weeks, 3 months, 6 months and 1 year.
- To evaluate whether SLT worked better in treatment naïve versus patients who were already on AGM
- Success criteria was defined as post laser IOP reduction of atleast 20% from baseline IOP.
- To evaluate the various parameters that affected the success of SLT
- Study population:
- 139 patients were included for statistical analysis with 68 patients completing 1 year follow up. The study population included patients having ocular hypertension (74.1%) and primary open angle glaucoma (25.9%). The mean age of the study population was 47.87 years. P value of 0.993 showed no significant difference in the age between the OHT and POAG patients. Student’s t-test was used to find out if there is any significant difference between diagnoses in age. P-value 0.993 (> 0.05) showed that there was no significant difference between age in OHT and POAG. Our study population included 103 males and 36 females. The mean (SD) for BCVA was 0.02 and median of 0.00. Mann-Whitney U test was used to find out if there is any significant difference between two groups. The p-value 0.768 (>0.05) showed that there was no significant difference between the mean BCVA of the two groups.
- MeanCCT value was observed to be 534.40 microns. Student’s t-test was used to find out if there was any significant difference between two groups. The p-value 0.502 (>0.05) showed that there was no significant difference between the CCT values of the two groups. Mean cup disc (CD) ratio in our study population was 0.54. P value of < 0.001 showed that there was a significant difference between OHT and POAG in CDR values. The Mean IOP was 22.43 mmHg. P value of 0.810 showed that there was no significant difference between the two groups. Mean number of AGM observed was 0.76. The p-value <0.001 (<0.05) using Mann-Whitney U test showed that there was a significant difference between OHT and POAG in AGM Pre-op. The mean mean deviation (MD) on Humphrey’s visual field analysis was –46. The p-value 0.155 (>0.05) showed that there was no significant difference between OHT and POAG in HFA.
- In our study we observed that the mean no. of AGM reduced significantly (p value <0.001) from 0.76 to 0.004. OHT group showed significant reduction in mean no. of AGM from 0.60 to 0.02. (p value <0.001) whereas the POAG group showed reduction from 1.22 to 0.09 (p value < 0.001). There was a significant difference between the groups before SLT while post SLT no significant difference was observed between the groups. (p value =0.236).
- Our study showed a significant reduction of IOP at each post SLT visits in both the groups (p value <0.001) . The p-valuet (>0.05) using independent t-test, showed that there was no significant difference between OHT and POAG at each follow-up visits. The p-valuep (<0.05) using paired t-test showed that there was a significant difference in OHT and POAG between IOP baseline and at each follow-up visits (IOP baseline vs. 2weeks, 6weeks, 3months, 6months, 12 months).
Discussion
The present study was done to evaluate whether SLT could be considered as primary option of treatment in ocular hypertension and primary open angle glaucoma.
Mean baseline IOP was 22.43 mm Hg in our study. We observed a statistically significant IOP reduction in both the POAG and the OHT group at 6 months and 1 year post SLT in comparison to the baseline IOP. There was no statistically significant difference between POAG group and OHT group at each follow up visit.
Our study showed an overall statistically significant IOP reduction from 22.43 mm Hg to 17.53 mm Hg at 6 months and 17.44 mm Hg at one year. IOP reduction in our study was observed to be 21.61% (23.23 % in OHT group and 16.37 % in POAG group) at 6 months while that after 1 year was 19.79 % (19.84 % in OHT group and 19.61 % in POAG group).
We also evaluated the various factors that may influence the success of SLT. Univariate analysis showed that the baseline IOP was the only factor which influences the final IOP. Other factors like age, gender, CCT and prior anti-glaucoma medication use did not influence the final IOP. Koucheki and Hashemi also found a similar correlation with baseline IOP in their study. (4) Hodge et al also found a similar result. Some studies found correlation between age and success of IOP. (9) Lee et al reported that SLT worked better in older age. Multivariate analysis also showed baseline IOP as the most important factor that influence the IOP reduction. A unique result found was that SLT worked better in females than males but was not statistically significant. This has not been noted in any of the other studies.
The limitations of the present study was the small sample size with 71 patients who were lost to follow up. Humphrey’s visual field analysis was not done in all patients to evaluate the stability after SLT.
Conclusion :
SLT is as effective as topical anti-glaucoma medication in POAG/OHT patients. Moreover, it is easier to deliver, hence can be used as primary treatment. It has been shown to reduce IOP significantly in both POAG and OHT patients. Adverse events are uncommon but most of these are transient and self-limiting. SLT has been shown to be a cost-effective option for primary treatment of glaucoma patients and seem to offer better quality of life. Hence we recommend SLT as a primary treatment in open angle glaucoma patients in south Indian population.
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