The effect of micro-incision and small-incision coaxial phaco-emulsification on corneal astigmatism

To evaluate the effect of micro-incision (2.2 mm) and small-incision (2.6 mm or 3.0 mm) coaxial phaco-emulsification on surgically induced astigmatism (SIA).

Cataract patients (n = 83, 129 eyes) were randomized into three groups: 43 eyes in the 2.2-mm incision group, 42 eyes in the 2.6-mm group and 44 eyes in the 3.0-mm group. Torsional phaco-emulsification was followed by intraocular lens implantation via the Monarch II injector with the C cartridge (Alcon Laboratories Inc., Fort Worth, TX, USA). Corneal astigmatism, SIA and uncorrected distance visual acuity were assessed 30 and 90 days after cataract surgery.

At 30 and 90 days postoperative, SIA of the 3.0-mm group was greater than SIA of the 2.2-mm and 2.6-mm groups (P < or = 0.015), but SIA was similar between the 2.2-mm group and the 2.6-mm group. Timewise, mean SIA at 30 days was greater than SIA at 90 days in the 3.0-mm group (P = 0.04), while SIA did not change with time for the 2.2-mm and 2.6-mm groups. Postoperative uncorrected distance visual acuity tended to be better with the smaller incisions, but this trend did not reach statistical significance (P > or = 0.07).

Incision size contributed to postoperative corneal astigmatism. When incision size was reduced from 3.0 mm to 2.6 mm, SIA was reduced and refractive stabilization was faster. Reduction of incision size from 2.6 mm to 2.2 mm offered no greater reduction of SIA when using the C cartridge; however, the D cartridge (designed for 2.2-mm incisions) should be evaluated.