The effect of intraocular pressure during phacoemulsification in patients with either diabetic retinopathy or glaucoma; a randomized controlled feasibility trial.

Purpose: To investigate whether performing phacoemulsification with a lower infusion pressure using the Centurion active sentry system affects surgical efficiency, complications and a range of clinical and imaging parameters compared to the higher pressures routinely used in patients with cataract and concomitant diabetic retinopathy and glaucoma.

Setting: Sunderland Eye Infirmary, Sunderland, United Kingdom.

Design: Masked observer randomized controlled feasibility trial.

Methods: Patients with cataracts undergoing routine phacoemulsification with either diabetic retinopathy or primary open-angle glaucoma of any severity were included and randomized to an infusion pressure of 30 ('LOW') or 60 ('HIGH') mmHg. All other fluidic settings were standardized. Surgical metrics and a range of imaging and clinical variables were measured pre- and postoperatively on days 1, 21 and 40.

Results: Seventy eyes from 70 patients underwent surgery and completed follow-up. Forty-one patients had diabetic retinopathy and 29 had glaucoma. There was no difference in any of the recorded surgical metrics including cumulative dissipated energy (CDE) between the two randomization groups (mean CDE 6.5 versus 6.1 percent seconds in the HIGH and LOW groups respectively, p = 0.68). There were no patients in either group with posterior capsule rupture or other intraoperative complications. There was no significant difference in the number of patients with raised intraocular pressure (IOP) on day 1. Seven (21.2%) patients in the LOW and 5 (13.3%) in the HIGH group had slit lamp detectable corneal oedema on day 1, which had all resolved by day 21. There were no between group differences for visual acuity, IOP, corneal thickness, and any of the optical coherence tomography (OCT) acquired measures at any of the time points. The foveal avascular zone perimeter and area were significantly smaller on day 21 than at baseline in the HIGH group as compared to the LOW group (P = 0.03 and 0.04 respectively), with a corresponding increase in the superficial vascular plexus density (p = 0.04).

Conclusion: Using an infusion pressure of 30mmHg with standardized aspiration fluidic settings on the Centurion active sentry system did not decrease surgical efficiency or increase complication rates compared to a pressure of 60mmHg. The lower infusion pressure may cause fewer short-term changes in the retinal microvasculature, the long-term significance of which is unknown.

Key messages: What is known Traditionally, phacoemulsification has been carried out under relatively high intraocular pressure (IOP) to mitigate the effects of post occlusion aspiration surge during lens removal.  A new enhanced phacoemulsification fluidics system has reduced surge allowing surgeons to operate at considerably lower, and more physiological IOP levels. What is new In patients undergoing phacoemulsification for moderate cataracts with either co-existing diabetic retinopathy or glaucoma, an IOP of 30 mmHg using the Centurion active sentry system did not result in any decrease in surgical efficiency or increase in complication rates compared to a higher pressure of 60 mmHg. Lower IOP phacoemulsification caused less short-term changes in the retinal microvasculature than higher pressure, the long-term significance of which is unknown and further study is needed.