To compare the induced regular and irregular astigmatism after scleral and corneal tunnel incision.
University hospital outpatient cataract clinic.
One hundred phacoemulsification patients with less than 1.0 diopter (D) of preoperative astigmatism were randomly assigned to have a clear corneal incision (50 patients) or a scleral tunnel incision (50 patients). All incisions were 3.5 to 4.0 mm wide and were made in the steepest axis of the corneal astigmatism. The surgically induced astigmatism was analyzed by vector analysis from keratometric data, as well as by Fourier harmonic series analysis of the topographic data.
One day after surgery, the surgically induced astigmatism (vector analysis, keratometry) was 1.41 D ± 0.66 (SD) and 0.55 ± 0.31 D in the corneal incision group and the scleral incision group, respectively (P
< .01). Six months after surgery, the induced astigmatism was 0.72 ± 0.35 D and 0.36 ± 0.21 D in the two groups, respectively (P
< .01). The corneal topography data confirmed the regular astigmatism changes found by conventional keratometry. However, in addition, Fourier harmonic series analysis of the topography data showed significantly more irregular induced astigmatism with the corneal approach than with the scleral approach.
The clear corneal incision induces significantly more regular as well as irregular astigmatism than the scleral tunnel incision.