Immediate Postoperative Intraocular Pressure Adjustment Reduces Risk of Cystoid Macular Edema after Uncomplicated Micro Incision Coaxial Phacoemulsification Cataract Surgery

Abstract

Purpose: To determine the accuracy of visual estimation of immediate postoperative intraocular pressure (IOP) following microincision cataract surgery (MICS) and the effect of immediate postoperative IOP adjustment on prevention of cystoid macular edema (CME).

Setting: Ambulatory surgical center.

Methods: Prospective, randomized analysis of 170 eyes in 135 patients with MICS, performed in a Medicare approved outpatient ambulatory surgery center. Surgical parameters included a keratome incision of 1.5 mm to 2.8 mm, topical anesthetic, case completion IOP estimation by palpation and patient visualization of light, and IOP adjustment before exiting the operating theater. IOPs were classified into three groups: low (<16 mmHg), normal (16 to 21 mmHg), and elevated (>21 to 30 mmHg). IOP measurements were repeated 1 day after surgery. Optical coherence tomography (Stratus OCT, Zeiss) was measured at 2 weeks. An increase in foveal thickness greater than 15 µm was used to indicate CME. Statistical analysis was performed using one- and two-tailed Student's t-tests.

Results: Mean minimal foveal thickness averaged 207.15 µm in the low pressure group, 205.14 µm in the normal IOP group, and 210.48 µm in the elevated IOP group 2 weeks following surgery. CME occurred in 14 of 170 eyes (8.2%) at 2 weeks (low IOP, 35.7%; normal IOP, 14.2%; elevated IOP, 50.0%). Change in IOP from the operating theater to 1 day after surgery was within +/-5 mmHg in 54 eyes (31.7%), elevated by 6 to 15 mmHg in 22 eyes (12.9%), and elevated more than 15 mmHg in four eyes (2.3%). IOP was reduced by 6 mmHg to 15 mmHg in 39 eyes (22.9%) and reduced by more than 15 mmHg in nine eyes (5.3%).

Conclusions: Immediate postoperative adjustment of IOP may prevent CME in MICS. Physicians can improve their ability to estimate postoperative IOP with experience in tonometry to verify immediate postoperative IOP. There are patient safety and economic benefits to immediate IOP adjustment in the operating theater.

Synopsis: Immediate postoperative IOP adjustment following cataract surgery before the patient leaves the operating theater may reduce the incidence of CME and provide patient safety and economic benefits.

Keywords: CME; Cystoid; Edema; MICS; Pressure.

Fig. 1. Case completion estimated intraocular pressure by surgeon. Immediate unadjusted postoperative intraocular pressure estimates varied by surgeon and were initially inconsistent. These estimates improved with surgeon experience over the course of the study.

Fig. 2. Change in intraocular pressure (IOP) from case completion to 1-day postop. Change in adjusted IOP from the operating theater to 1-day postop. Note the distribution showing little change in IOP in the majority of cases from the IOP adjusted on the operating room table to the next day postop. postop = postoperative.

Fig. 3. Cystoid macular edema (CME) by intraocular pressure (IOP) group. Two week macular thickness in the adjusted IOP group. CME grouped by adjusted postoperative IOP. Note that IOP values greater than 22 mmHg were responsible for 50% of the cases of CME, while normally adjusted IOP had the lowest incidence. ^*Patients considered to have macular edema if surgical eye is 15 or more microns thicker than non-surgical eye.

Fig. 4. Rebound or “relative hypotony.” Illustration depicting rebound or relative hypotony from low intraocular pressure values. CME = cystoid macular edema.