April 13, 2019
"Close monitoring of intraocular pressure in the early postoperative period after vitreoretinal surgery is common clinical practice. Whether there is a need for long-term monitoring for glaucoma after vitreoretinal surgery, however, is less clear," says Arthur J. Sit, M.D., with Ophthalmology at Mayo Clinic's campus in Rochester, Minnesota. "Confirming the risk of late-onset, primary open-angle glaucoma (POAG) after scleral buckling and vitrectomy, as well as baseline risk factors, can help facilitate earlier detection and treatment of POAG."
Dr. Sit and fellow researchers conducted a retrospective, population-based cohort study to determine the long-term risk of POAG after vitreoretinal surgery, published in American Journal of Ophthalmology in 2018.
The research team used data from the Rochester Epidemiology Project (REP) to identify all residents of Olmsted County, Minnesota, who underwent scleral buckling, vitrectomy or both between 2004 and 2015. A total of 344 eyes fulfilled the inclusion and exclusion criteria:
- 160 male and 184 female eyes with a mean age of 64.7 ± 11.1 years at the time of surgery (the fellow 277 nonoperative eyes were included in the comparison cohort)
- 58, 57 and 229 study eyes in the scleral buckling, scleral buckling with vitrectomy and vitrectomy-only cohorts, respectively
"Advantages of this study include its population-based nature and large sample size, which enabled calculation of incidence rates for POAG in various cohorts and comparison to an unexposed cohort, as well as expected rates for the general population," says Dr. Sit. "We were able to focus on open-angle glaucoma as our primary endpoint due to our long follow-up ― the mean follow-up was 62.1 ± 38.4 months ― and the availability of linked records through the REP. Furthermore, glaucoma suspects could be more fully evaluated, since diagnosis was based on findings recorded over all of the follow-up visits. Selection bias was likely very low, since it included all patients in the Olmsted County population undergoing vitreoretinal surgery."
- The 10-year probability of POAG was 17.5 percent and 10.0 percent in the scleral buckling with vitrectomy and the vitrectomy-only cohorts, respectively, compared with 1.0 percent in the nonoperative cohort.
- None of the eyes in the scleral buckling cohort developed glaucoma.
- The mean and median time intervals for development of POAG after surgery were 40.2 months and 46.1 months, respectively.
- The rates of POAG in operative eyes undergoing scleral buckling with vitrectomy and vitrectomy-only were significantly greater than the 1.0 percent rate of POAG for the Olmsted County general population.
"We found that there was a tenfold to seventeenfold increased risk of POAG in eyes after vitrectomy or scleral buckling with vitrectomy surgery when compared with fellow nonoperative eyes," says Dr. Sit.
Other risk factors for glaucoma
Researchers also compared the observed rate of glaucoma in the nonoperative cohort of eyes with the expected rates of POAG in the age- and sex-matched general population and found no difference. Further, the only other variable associated with an increased risk of POAG was higher baseline intraocular pressure. These results suggest that pre-existing risk factors for glaucoma may not be significant contributors to the increased risk of glaucoma after vitreoretinal surgery and that the development of POAG is due to risks related to the surgery itself.
Previous researchers have suggested that increased oxygen-free radical damage to the trabecular meshwork in vitrectomized eyes may lead to increased intraocular pressure and glaucoma. However, among the patients who developed glaucoma, 27 percent had normal-tension glaucoma. Further, among patients with suspected POAG, 61 percent had normal pressures but had optic disk or visual field findings that were suspicious for glaucoma. This outcome suggests that multiple mechanisms may be involved in the pathogenesis of POAG after vitrectomy, and not just elevated intraocular pressure.
"Whether or not it is appropriate to classify the glaucoma as POAG is therefore debatable," says Dr. Sit. "It may be more accurate to describe the disease as vitrectomy-associated glaucoma, but further research is required to clarify the mechanism of damage.
"In summary, the study results provide strong evidence for an increased risk of glaucoma after vitrectomy or vitrectomy with scleral buckling, but not scleral buckling alone. This finding is of particular concern, since the rates of vitrectomy are increasing and there is a trend toward vitrectomy replacing scleral buckling for management of retinal detachment," says Dr. Sit. "Our study suggests a need for more-frequent monitoring for glaucoma after vitrectomy and the discussion of glaucoma risk with patients prior to vitreoretinal surgery."
For more information
Mansukhani SA, et al. The risk of primary open-angle glaucoma following vitreoretinal surgery — A population-based study. American Journal of Ophthalmology. 2018;193:143.
Mayo Clinic. Rochester Epidemiology Project.