Effect Of Incision Location And Keratometric Astigmatism On Surgically Induced Astigmatism After Implantable Collamer Lens Implantation

To evaluate surgically induced astigmatism (SIA) in eyes after implantable collamer lens (ICL) implantation through superior and temporal corneal incisions for different keratometric astigmatism.

Eye and ENT Hospital of Fudan University, China.

The cohort study included 151 eyes of 91 consecutive patients who underwent ICL implantation. An ocular examination was performed preoperatively, 1 and 6 months postoperatively. The magnitude and axis of corneal astigmatism were assessed with keratometry (Astig_K) and total corneal refractive power (TCRP, Astig_TCRP) measured using a Scheimpflug camera, whereas SIA obtained from keratometry (SIA_K) and TCRP (SIA_TCRP) were evaluated using vector analysis.

 At 6 months, Astig_K significantly decreased from 1.45±0.72 D to 1.16±0.74 D in superior incision group, whereas increased from 1.81±0.80 D to 2.00±0.85 D in temporal incision group (both P<0.001). Astig_TCRP significantly decreased from 1.32±0.73 D to 1.11±0.80 D in superior incision group, whereas increased from 1.73±0.84 D to 1.96±0.93 D in temporal incision group (both P<0.001). SIA_K was 0.54±0.31 D and 0.36±0.24 D in superior and temporal incision groups, respectively, whereas SIA_TCRP was 0.50±0.28 D and 0.41±0.26 D in the two groups. SIA_K and SIA_TCRP were larger in superior incision group than those in temporal incision group for low- (P=0.001 for SIA_K, P=0.145 for SIA_TCRP) and high-astigmatism (P=0.006 for SIA_K, P=0.011 for SIA_TCRP).

Superior incision had a larger SIA than temporal incision, especially for high keratometric astigmatism, with corneal flattening shifting towards the direction of incision site. Surgeons should optimize incision location according to preoperative astigmatism and consider SIA when selecting TICL cylindrical power.