Uncomplicated vitrectomy may cause primary open-angle glaucoma

Chicago-Uncomplicated vitrectomy has been implicated in the development of primary open-angle glaucoma (POAG), according to Stanley Chang, MD, who presented the Jackson Memorial Lecture Sunday at the American Academy of Ophthalmology annual meeting.

This is an important finding because vitrectomy is the third most frequently performed ophthalmologic procedure. Dr. Chang’s hypothesis for the development of POAG is that oxygen causes oxidative stress, which impairs the functioning of the trabecular meshwork.

In his practice, Dr. Chang noticed that some patients who underwent uncomplicated vitrectomy developed POAG over extended periods in the operated eye only. This observation prompted a retrospective review of 1,156 charts of patients who underwent vitrectomy since 1995.

Of these, 68 eyes of 65 patients with follow-up longer than 6 months were identified that developed POAG: group 1, 10 patients were glaucoma suspects who had an IOP level in the operated eye that was more than 4 mm Hg higher than the fellow eye; group 2, 40 patients had new onset glaucoma with IOP levels over 30 mm Hg and optic disc changes and visual field changes; and group 3, 15 patients had been diagnosed with glaucoma and treated before vitrectomy who were studied to observe the effect of glaucoma on the operated eye, Dr. Chang explained. He is the chairman of the department of ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York.

Interesting findings were that in group 1, the mean IOP in the operated eye was significantly higher than in the fellow eye; in group 2, the mean time to glaucoma development in vitrectomized eyes was significantly longer in phakic (45 months) versus aphakic (18 months) eyes, and in group 3, there was no difference between the operated and fellow eyes.

“When new glaucoma was diagnosed and treated, it was usually in the vitrectomized eye. The time to glaucoma diagnosis was longer in phakic eyes compared with aphakic eyes, suggesting that the lens may have a protective role in delaying the onset of glaucoma,” he reported.

Dr. Chang proposed that after the vitreous is removed, a diffusible factor appears that alters the biochemical environment.

“That factor initially causes progressive nuclear sclerosis in the lens and after cataract surgery an increase in resistance to aqueous outflow, resulting in glaucoma,” he said. “I suggest that this factor is increased oxygen, which results in oxidative stress. Long-term follow-up of patients who have undergone vitrectomy is mandatory to detect and treat glaucoma early.”