Correction of pre-existing astigmatism by on-axis incision size modulation in manual small-incision cataract surgery.

Purpose: To study the effect of wound size modulation on pre-existing astigmatism by on-axis placement of incision in manual small-incision cataract surgery (MSICS).

Methods: In this prospective interventional study conducted at a tertiary care centre, 40 eyes of 40 consecutive senile cataract patients with 1.00-3.00 D corneal astigmatism were enrolled for the study. MSICS by modified Blumenthal's technique was performed through 6.0, 6.5, and 7.0 mm on-axis incision in 1.0-1.49 D (group A), 1.50-1.99 D (group B), and 2.00-3.00 D (group C) astigmatism, respectively. Surgically induced astigmatism (SIA) was calculated by vector analysis and double angle plots (DAP) at 12 weeks postoperatively.

Results: There were 22 males and 18 females with mean age of 58.12 ± 1.18 years. The mean SIA at 12 weeks was 0.85 ± 0.28 D in group A (17 eyes), 1.32 ± 0.65 D in group B (10 eyes), and 1.91 ± 0.69 D in group C (13 eyes). The overall median uncorrected visual acuity was 0.18 (IQR = 0 to 0.2). The mean astigmatism decreased from 1.95 ± 0.74 D to 1.04 + 0.57 D (P = 0.00) in superior incision and from 1.70 + 0.50 D to 0.92 ± 0.45 D (P = 0.00) in temporal incision group with central shift of centroid in all cases.

Conclusion: The customization of on-axis external incision size can be used to manage pre-existing corneal astigmatism of less than 3.00 D using both temporal and superior incisions effectively.