Glaucoma is a chronic optic neuropathy characterized by retinal ganglion cell death resulting in damage to the optic nerve head and the retinal nerve fiber layer. Pigment dispersion syndrome is characterized by a structural disturbance in the iris pigment epithelium (the densely pigmented posterior surface of the iris) that leads to dispersion of the pigment and its deposition on various structures within the eye. Pigmentary glaucoma is a specific form of open-angle glaucoma found in patients with pigment dispersion syndrome.Topcial medical therapy is usually the first-line treatment; however, peripheral laser iridotomy has been proposed as an alternate treatment. Peripheral laser iridotomy involves creating an opening in the iris tissue to allow drainage of fluid from the posterior chamber to the anterior chamber and vice versa. Equalizing the pressure within the eye may help to alleviate the friction that leads to pigment dispersion and prevent visual field deterioration. However, the effectiveness of peripheral laser iridotomy in reducing the development or progression of pigmentary glaucoma is unknown.
The objective of this review was to assess the effects of peripheral laser iridotomy compared with other interventions, including medication, trabeculoplasty, and trabeculectomy, or no treatment, for pigment dispersion syndrome and pigmentary glaucoma.
We searched a number of electronic databases including CENTRAL, MEDLINE and EMBASE and clinical trials websites such as (mRCT) and ClinicalTrials.gov. We last searched the electronic databases on 2 November 2015.
We included randomized controlled trials (RCTs) that had compared peripheral laser iridotomy versus no treatment or other treatments for pigment dispersion syndrome and pigmentary glaucoma.
We used standard methodological procedures for systematic reviews. Two review authors independently screened articles for eligibility, extracted data, and assessed included trials for risk of bias. We did not perform a meta-analysis because of variability in reporting and follow-up intervals for primary and secondary outcomes of interest.
We included five RCTs (260 eyes of 195 participants) comparing yttrium-aluminum-garnet (YAG) laser iridotomy versus no laser iridotomy. Three trials included participants with pigmentary glaucoma at baseline, and two trials enrolled participants with pigment dispersion syndrome. Only two trials reported the country of enrollment: one - Italy, the other - United Kingdom. Overall, we assessed trials as having high or unclear risk of bias owing to incomplete or missing data and selective outcome reporting.Data on visual fields were available for one of three trials that included participants with pigmentary glaucoma at baseline. At an average follow-up of 28 months, the risk of progression of visual field damage was uncertain when comparing laser iridotomy with no iridotomy (risk ratio (RR) 1.00, 95% confidence interval (95% CI) 0.16 to 6.25; 32 eyes; very low-quality evidence). The two trials that enrolled participants with pigment dispersion syndrome at baseline reported the proportion of participants with onset of glaucomatous visual field changes during the study period. At three-year follow-up, one trial reported that the risk ratio for conversion to glaucoma was 2.72 (95% CI 0.76 to 9.68; 42 eyes; very low-quality evidence). At 10-year follow-up, the other trial reported that no eye showed visual field progression.One trial reported the mean change in intraocular pressure (IOP) in eyes with pigmentary glaucoma: At an average of nine months of follow-up, the mean difference in IOP between groups was 2.69 mmHg less in the laser iridotomy group than in the control group (95% CI -6.05 to 0.67; 14 eyes; very low-quality evidence). This trial also reported the mean change in anterior chamber depth at an average of nine months of follow-up and reported no meaningful differences between groups (mean difference 0.04 mm, 95% CI -0.07 to 0.15; 14 eyes; very low-quality evidence). No other trial reported mean change in anterior chamber depth. Two trials reported greater flattening of iris configuration in the laser iridotomy group than in the control group among eyes with pigmentary glaucoma; however, investigators provided insufficient data for analysis. No trial reported data related to mean visual acuity, aqueous melanin granules, costs, or quality of life outcomes.Two trials assessed the need for additional treatment for control of IOP. One trial that enrolled participants with pigmentary glaucoma reported that more eyes in the laser iridotomy group required additional treatment between six and 23 months of follow-up than eyes in the control group (RR 1.73, 95% CI 1.08 to 2.75; 46 eyes); however, the other trial enrolled participants with pigment dispersion syndrome and indicated that the difference between groups at three-year follow-up was uncertain (RR 0.91, 95% CI 0.38 to 2.17; 105 eyes). We graded the certainty of evidence for this outcome as very low.Two trials reported that no serious adverse events were observed in either group among eyes with pigment dispersion syndrome. Mild adverse events included postoperative inflammation; two participants required cataract surgery (at 18 and 34 months after baseline), and two participants required a repeat iridotomy.
We found insufficient evidence of high quality on the effectiveness of peripheral iridotomy for pigmentary glaucoma or pigment dispersion syndrome. Although adverse events associated with peripheral iridotomy may be minimal, the long-term effects on visual function and other patient-important outcomes have not been established. Future research on this topic should focus on outcomes that are important to patients and the optimal timing of treatment in the disease process (eg, pigment dispersion syndrome with normal IOP, pigment dispersion syndrome with established ocular hypertension, pigmentary glaucoma).