The Effect of Peribulbar Block Volume on Intraocular Pressure Change: A Randomized Prospective Study

Peribulbar block (PB) is a widely used anesthesia modality in ophthalmic surgical procedures globally. There are no evidence-based guidelines on PB best practices available. We studied the relationship between block solution volume, the change in intraocular pressure (IOP) and anesthesia effect to guide practice.

Prospective, controlled, 1:1 randomized, interventional study carried out at two ambulatory surgical centers.

Ambulatory male and female patients between age 18 and 79 years of age undergoing planned intraocular surgery with PB as the designated anesthesia modality per surgeon's instruction prior to study enrollment. Eyes with any previous ocular procedure or surgery, or any orbital surgery were excluded. Eyes with corneal scars or cornea edema were also excluded.

Prior to the scheduled ophthalmic surgery, the enrolled eye was randomized to either 4 mL or 7 mL block volume immediately before PB administration by one of the five anesthesiologists. A regimented 2-minute manual massage was performed by the same research assistant after every block. IOPs were measured with a freshly calibrated tonopen before-block, immediate after-block, and after-manual massage, twice at each time point. Immediately after the completion of the intended surgery, the surgeon was asked to fill the anesthesia satisfaction sheet while staying masked to the block volume.

IOP changes at each step and the surgeons' rating of the quality of anesthesia.

There were 50 eyes completed the trial with 25 eyes in each group. There was no statistically significant difference between the two groups in terms of IOP change after the block or after the massage; both groups' IOP decreased significantly after the ocular massage. The 7-mL group achieved a significantly higher surgeon satisfaction score.

7-mL PB was shown to be a safe and more effective method for ocular surgical procedures.