Predicting pressure spikes after cataract surgery

Glaucoma
March 2011

by Tony Realini, M.D.

Cataract surgery may cause a spike in IOP immediately after surgery  Source: Jorge Alio, M.D.
Cataract surgery may cause a spike in IOP immediately after surgery
Source: Jorge Alio, M.D.

Cataract surgery is the most commonly performed surgery on adults in the United States, and it is among the safest procedures. One relatively common post-op complication is an acute rise in IOP within the first day or so after surgery. IOP spikes on the day after cataract surgery can be quite high, into the 30-40 mm Hg range.

“Cataract surgery often results in a long-term lowering effect on IOP,” said Philip Chen, M.D., University of Washington, Seattle. “In the immediate post-operative period, however, IOP may be acutely elevated due to retained viscoelastic devices, intraocular inflammation, or other factors.”

Consequences of IOP spikes

For the majority of healthy eyes, this moderate IOP increase poses no significant threat to long-term visual health. But for patients with glaucoma whose optic nerves may already be compromised, a significant post-op IOP spike can be dangerous.

“Although the clinical implications of a short-term IOP spike have not been clearly defined, elevated IOP remains a primary risk factor for glaucoma progression in patients with open-angle glaucoma,” Dr. Chen said.

“Cataract surgery results in a post-operative IOP spike in a significant proportion of both normal and glaucomatous eyes,” he said. “Identifying those patients at risk for an acute IOP spike would be clinically valuable, particularly in patients with known glaucomatous optic nerve damage.”

Robert Fechtner, M.D., director, glaucoma division, University of Medicine & Dentistry of New Jersey, Newark, agreed. “If we could identify ahead of time those patients most likely to experience a significant IOP rise in the peri-operative period, we would be in a position to provide aggressive prophylactic therapy to blunt the spike.”

Risk factors for IOP spikes

To address this relevant clinical issue, Dr. Chen and colleagues evaluated the post-op IOP profile of 80 patients with normal-tension glaucoma or high-tension open-angle glaucoma undergoing elective, uncomplicated cataract surgery performed by a single surgeon (Dr. Chen himself).

His customary peri-op practice is to ask patients not to use their IOP-lowering drops on the morning of surgery. “I worry about bacterial contamination from the bottles, so I do this as a measure of infection control,” he said. To control IOP in the peri-op period, Dr. Chen prescribes oral acetazolamide to all of his glaucoma patients to be taken six hours after surgery.

Overall, said Dr. Chen, 17 of the 80 patients (21%) exhibited an IOP spike of greater than 10 mm Hg from baseline on the first post-op day.

“The risk factors for an IOP spike were open angles, implantation of acrylic lenses, and refusal or forgetting to take the prophylactic acetazolamide,” he said.

He does not think that having open angles is a true risk factor for an IOP spike. Rather, he said, the patients with narrow angles tended to have lower IOP after surgery, which made having open angles look like a relative risk factor.

The use of acrylic lenses was of interest, he said. “Increased IOP following implantation of acrylic lenses has been reported in one of the two studies that looked at this issue,” he said. “There have been a few hypotheses as to the cause of this, including the higher likelihood of retained viscoelastic due to adhesion to the hydrophilic acrylic lenses, or perhaps even direct effects on the ciliary body’s production of aqueous. We are not aware of a definitive reason to explain this phenomenon, although the difference warrants further investigation.”

Several potential risk factors turned out not to be important in identifying the patients who had IOP spikes, said Dr. Chen. These included age, pre-op IOP, the number of IOP-lowering medications used, the need for intra-op iris manipulation, and whether or not the wound was sutured closed.

Preventing IOP spikes

Given this new data, has Dr. Chen changed his approach to managing IOP in his glaucoma patients undergoing cataract surgery?

“We are becoming more aggressive on this issue,” he said. “Our first step is to underscore the importance of taking the post-operative dose of acetazolamide. While 21% of patients spiked overall, five of the eight patients who didn’t take their acetazolamide had an IOP spike. That’s 63%. Clearly the acetazolamide helps, so we’ve been strongly encouraging patients to take it after surgery.”

He is also revisiting the practice of holding routine IOP medications on the morning of surgery.

“Perhaps we should provide sterile bottles in the pre-operative area and dose our glaucoma patients with their typical morning drops before surgery,” he said.

Dr. Fechtner agreed that prevention is the best approach to post-op IOP spikes. “Once the damage is done, it’s done,” he said. He found Dr. Chen’s results regarding acetazolamide encouraging. “It’s good to know that a single dose of acetazolamide given post-operatively can reduce the rate of IOP spikes from over 60% to less than 20%. It makes sense to remember to offer this protection from IOP spikes, especially for those with more advanced disease.”


Editors’ note

Drs. Chen and Fechtner have no financial interests related to their comments.

Contact information

Chen: pchen@uw.edu
Fechtner: fechtner@umdnj.edu