To evaluate whether intraocular pressure reduction by intravenous injection of mannitol before phacoemulsification-cataract surgery can have a protective effect on corneal endothelium.

Patients undergoing sequential bilateral cataract surgery were divided into 2 groups, 36 eyes with anterior chamber depth (ACD) < 2.50 mm (group A) and 44 eyes with ACD ≥ 2.50 mm (group B). In each group, preoperative intravenous injection of mannitol was performed in 1 randomly selected eye of the patient. The specular microscopic examination including cell density (ECD), coefficient of variation (CV), hexagonality (HA) of corneal endothelium, and corneal thickness was performed on postoperative 1 day, 2 weeks, and 5 weeks. In each group, the parameters were compared between the eyes with mannitolization and the contralateral eyes without mannitolization.

In group A, eyes with preoperative mannitolization showed significantly higher ECD at postoperative 1 day and 5 weeks and showed a significantly thinner cornea at postoperative 1 day than those without mannitolization (all p < 0.05). However, in group B, there was no significant difference of ECD, CV, HA, and corneal thickness between the eyes with and without mannitolization.

Preoperative intraocular pressure reduction by mannitolization before phacoemulsification can protect the corneal endothelial cells and recover the early postoperative period visual acuity in eyes with shallow anterior chamber.