Minimally Invasive surgery reduces IOP, halts glaucoma progression: GEMINI Study
Glaucoma is a progressive optic neuropathy that, if unchecked, can result in blindness. Treatment is aimed at preventing or retarding the rate of vision loss such that good visual function is maintained over a patient's lifespan. Elevated intraocular pressure (IOP) is the most important risk factor for development and progression of glaucoma and the only one that can be modified.
IOP has a normal circadian cycle with pressure generally increasing at night, peaking in the early morning hours, and then declining during the daytime, although peak IOP timing may vary. Diurnal fluctuation, particularly where peak IOP is relatively high, has been implicated as an important risk factor for glaucoma progression, independent of IOP alone. Therapies that temper or damp peak fluctuations could thus be of great value in reducing the rate of glaucoma progression.
Implant and depot delivery of IOP-lowering drugs have sought to provide long-term IOP control with lower peak amplitude while mitigating the problems associated with daily dosing and patient adherence. Surgical intervention can also provide for long-term IOP control but, due to the risk and complication profile, was previously reserved for advanced glaucoma where significant and permanent damage had already occurred. The advent of minimally (or micro) invasive glaucoma surgery (MIGS) has, and continues, to change the thinking regarding the place of surgery in glaucoma treatment with surgical intervention becoming increasingly common for mild–moderate glaucoma treatment
Continuous IOP control that is not reliant on adherence to a dosing regimen should result in a more even and predictable IOP profile over time. The aim of the present study done by Pyfer et al was to challenge this assumption, whether MIGS surgery results in an overall decreased amplitude in the diurnal IOP profile when compared to the diurnal IOP profile in the same patients presurgically?
This study was a post hoc analysis of diurnal IOP data collected from patients treated with the OMNI Surgical System as participants in the multicenter, historically controlled GEMINI study. The study was a 12-month study with preoperative and terminal medication washouts.
Fifteen ophthalmology practices and surgery centers located in 14 states in the United States were included. It was a prospective, multicenter, IRB approved study. Patients were treated with canaloplasty (360°) and trabeculotomy (180°). Patients had cataract and mild–moderate OAG with intraocular pressure (IOP) ≤33 mmHg on zero to four hypotensive medications.
Analysis included comparison of IOP preoperatively and at month 12 for each of the diurnal time points, 9AM, 12PM, 4PM, change in magnitude of spread between the maximum IOP and minimum IOP for each patient and the proportions of patients preoperatively and at month 12 with IOPs at or below 25, 21, 18, and 15 mmHg, average variability (standard deviation of the 9AM, 12PM, and 4PM IOP) preoperatively and at month 12.
- A total of 128 patients were included in this analysis. IOP at each diurnal time point was significantly lower postoperatively (p<0.0001).
- The difference between highest and lowest IOP measurement for each patient averaged 2.8 mmHg preoperatively (SD 2.4, MAX 14, MIN 0) and 1.8 mmHg (SD 1.7, MAX 10, MIN 0) month 12 (P<0.0001).
- The proportion with IOP ≤ to 25, 21, 18, and 15 mmHg increased; 75%–97%, 27%–88%, 1%–79%, and <1%–56%, respectively. The average variability was greater at all time points preoperatively (P<0.0001).
The analysis of GEMINI data shows that in addition to significant overall mean IOP reduction, the amplitude of mean IOP was reduced at each of the diurnal time points where IOP was measured. Moreover, 95% of patients had diminished peak IOP post-surgically when compared to the preoperative measurements.
Glaucoma is a pernicious disease that can cause substantial and significant damage before it is detected. This fact, and the development of surgical treatments with favorable safety profiles, has led to an increasing willingness to intervene as early as possible in the course of the disease.
While lowering IOP is universally acknowledged to be key in limiting progressive glaucomatous damage, modulation of peak 24-hour IOP has been increasingly recognized as important. IOP fluctuation and peak IOP have been shown to be significant risk factors for progression of glaucoma.
Evidence that IOP increases during the night, likely due to both circadian factors as well as supine body position suggests that any effort directed at IOP reduction should also attempt to provide 24-hour efficacy. The results from the present study show peak IOP reduced by over 8 mmHg and a reduction in fluctuation of 1 mmHg (from 2.8 to 1.8) suggesting that the risk of visual field progression may have been ameliorated, particularly in comparison to their pre-study, unmedicated status.
The present study demonstrates that eyes with primary open-angle glaucoma can benefit from an overall decreased IOP and degree of IOP fluctuations for as long as 12 months after surgical treatment with canaloplasty and trabeculotomy. Further study with a greater sample size and longer follow-up are needed and ongoing. Study using other MIGS procedures to determine the generalizability of these results are also needed.
Source: Pyfer et al; Clinical Ophthalmology 2021:15 3931–3938