A recent study published in Vision sought to determine the optimal timing for measuring intraocular pressure (IOP) following phacoemulsification cataract surgery.
Give me some background.
IOP spikes are a common complication after cataract surgery and can result in adverse events, such as:
- Pain
- Nausea
- Vomiting
- Corneal edema
- Blurred vision
As such: Assessing IOP is an essential element of post-operative checks.
Are there current guidelines for checking postoperative IOP levels?
In 2021, the American Academy of Ophthalmology (AAO) recommended that IOP be measured within the first 48 hours after surgery in patients with low-risk surgeries and no signs or symptoms of possible postoperative complications.
Conversely: Functionally monocular patients and those at high risk of early postoperative complications should have their IOP measured within the first 24 hours after surgery.
However: The study authors noted that there are not more specific recommendations currently indicated—resulting in the timing of IOP checks often being a matter of convenience for the surgeon rather than when the undesired outcome is most likely to be detected.
Now talk about the study.
In this systematic review and meta-analysis, investigators performed a comprehensive literature search on MEDLINE and EMBASE for articles that reported IOP measurements after uncomplicated cataract surgery.
They also recorded certain features of the cataract surgeries, including:
- The use of ophthalmic viscosurgical devices (OVDs)
- The surgical procedure utilized during cataract extraction
- Medications administered
In total, the study included 57 randomized clinical studies involving 6,318 participants (43.7% male, mean age: 68.4 years) and 7,089 eyes.
Findings?
The researchers found that specific postoperative hours were associated with different IOP levels, such as:
- Hour 1: Significant decrease in IOP from baseline (-2.08 mmHg)
- Hour 2: Nonsignificant increase in IOP from baseline (+0.81 mmHg)
- Hours 4, 6, and 8: The only time points with a significant increase in IOP after cataract surgery (+1.38, +0.83, and +0.93 mmHg, respectively)
Further, postoperative day 1 had no significant change in IOP, while day 2 had a nonsignificant decrease (-0.36 mmHg)—suggesting that the optimal time to measure IOP is within the first 4-8 hours after cataract surgery.
Expert opinion?
The study authors outlined additional findings from the study, including:
- Measuring IOP sooner than 2 hours may be misleading because IOPs were found to be lower than baseline—likely connected to surgical techniques to manage wound closure after aspiration of OVD
- Based on 54 studies, there remains significant variability in peri-operative medications:
- The most common preoperative medications were either an antibiotic or nonsteroidal anti-inflammatory drug (NSAID)
- The most common intraoperative medication was either an antibiotic, carbachol, and/or a steroid
- Postoperatively, the majority of studies utilized a combination of an antibiotic, steroid, and/or NSAID
- 10 studies reported using an IOP-lowering medication prophylactically, such as carbonic anhydrase inhibitors, beta-blockers, prostaglandin analogs, or alpha agonists,
- These were used to prevent IOP elevations, lower IOP in patients who were actively experiencing a dangerous spike, or as routine treatment for glaucoma patients
Limitations?
These included:
- There was variability in the quality of scoring of the included studies
- Asymmetry of a few funnel plots at various post-operative follow-up time points—potentially due to difficulty in the interpretation of the funnel plot for a small group of studies, high heterogeneity, and small effect sizes
- Only one study corrected for the effect of clear corneal thickness (CCT) values on IOP measurements
- No studies reported patient position during IOP measurement
- There was significant heterogeneity at all postoperative time points except for 8 hours after cataract surgery
Take home.
These findings suggest that the best time to measure IOP is within the first 4-8 hours after cataract surgery, as taking measurements too soon or too late may result in missed IOP spikes.