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CHICAGO -- Traditional glaucoma surgery more than doubled the likelihood of treatment success for elevated intraocular pressure (IOP) as compared with the more widely used minimally invasive glaucoma surgery (MIGS), but with more complications, according to data from a national registry.

More than half of patients who had traditional incisional glaucoma surgery (TIGS) met criteria for treatment success at 1 year, as compared with about a fourth of patients who had MIGS procedures. The between-group differences were similar at 2 and 3 years. Investigators defined success as an IOP ≤18 mm Hg plus a reduction of ≥20% from baseline, with no hypotony (IOP ≤5 mm Hg), reoperation for glaucoma, or loss of light perception.

Both types of procedures significantly reduced IOP from baseline, but TIGS led to substantially larger decreases. The notable downside of TIGS was a higher rate of complications, including severe complications, said Shan Lin, MD, of the Glaucoma Center of San Francisco, during the American Academy of Ophthalmology (AAO) meeting.

"We're not very surprised [by the results]," said Lin. "MIGS real-world success is probably less than what we see in the published literature, randomized clinical trials. "There are many reasons for that, but we don't have time to go into that. There is a significant lowering of intraocular pressure [with MIGS] and medication use stayed about the same."

During a discussion that followed his presentation, Lin acknowledged that most MIGS procedures included placement of trabecular meshwork bypass stents, which could have influenced the impact of the surgery. Additionally, many of the patients treated with MIGS had cataract surgery at the same time, and studies have shown that cataract surgery alone has an IOP-lowering effect.

A member of the audience also pointed out that stents have improved over time and many of the devices included in the analysis "are no longer in play," which could have influenced the results with MIGS.

"That's a really good point," said Lin. "We're probably going to have better results with the newer MIGS."

The analysis involved data from the AAO's (IRIS) Registry, the nation's first comprehensive eye disease registry based on electronic health records contributed by 7,200 practicing ophthalmologists. The analysis included procedures performed from Jan. 1, 2014 through Dec. 31, 2018, allowing for 3 years of follow-up in all cases. Eligible patients were 18 or older and had a diagnosis of primary open-angle glaucoma (POAG).

In addition to the primary outcome, two alternate analyses were performed with different IOP criteria: ≤21 mm Hg and ≤14 mm Hg.

Data analysis included 60,031 eyes, comprising 16,890 in the TIGS group and 43,141 in the MIGS group. TIGS procedures consisted of 9,666 trabeculoplasties and 7,224 tube shunts. In the MIGS group, 29,938 procedures included a bypass stent.

The patients had a median age of 71-73, women accounted for about 60% of the total population, and two-thirds of patients were white. In the TIGS group, 17.4% of procedures included concurrent cataract surgery, whereas 98.8% of MIGS procedures included cataract surgery. A majority (54.5%) of eyes in the TIGS group had severe POAG, and 87% of the MIGS group had mild or moderate POAG.

The primary analysis showed that 54.6% of TIGS procedures met success criteria as compared with 26.2% of the MIGS group. Mean IOP decreased from 24 to 14 mm Hg (a 42% reduction) in the TIGS group versus 17 to 15 mm Hg (10%) with MIGS, both of which represented significant improvement from baseline (P<0.001). Medication use decreased significantly (P<0.001) in the TIGS group after surgery and remained unchanged in the MIGS group, which had lower baseline medication use.

The most common reason for not achieving treatment success was failure to reduce IOP by ≥20% from baseline in both the TIGS (69%) and MIGS (97%) groups. In about a third of TIGS cases, IOP did not decline to ≤18 mm Hg as compared with a fourth of the MIGS group. Hypotony rates were 12% with TIGS and 0.4% with MIGS, reoperation rates were 14% versus 3%, and loss of light perception occurred in 2% and 0.1%, respectively.

Two years after surgery, 50.8% of the TIGS group still met criteria for treatment success as compared with 25.5% of the MIGS group, and the 3-year success rates were 46.6% versus 24.9%. When IOP reduction ≥20% from baseline was excluded from the success criteria, rates of treatment success at 1 year were 75% with TIGS and 83% with MIGS.

Severe complications (such as endophthalmitis, retinal detachment, and suprachoroidal hemorrhage) occurred more often with TIGS but were infrequent in both groups.

Lin acknowledged several limitations of the analysis: the lack of visual field data, multiple variables with a substantial "unknown" component, the potential for miscoding in data entry, and possible underreporting of complications and adverse events.

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