Comparative evaluation of toric intraocular lens alignment and visual quality with image-guided surgery and conventional three-step manual marking

Purpose: To compare toric intraocular lens (IOL) alignment assisted by image-guided surgery or manual marking methods and its impact on visual quality. Patients and methods: This prospective comparative study enrolled 80 eyes with cataract and astigmatism >= 1.5 D to undergo phacoemulsification with toric IOL alignment by manual marking method using bubble marker (group I, n=40) or Callisto eye and Z align (group II, n=40). Postoperatively, accuracy of alignment and visual quality was assessed with a ray tracing aberrometer. Primary outcome measure was deviation from the target axis of implantation. Secondary outcome measures were visual quality and acuity. Follow-up was performed on postoperative days (PODs) 1 and 30. Results: Deviation from the target axis of implantation was significantly less in group II on PODs 1 and 30 (group I: 5.5 degrees +/- 3.3 degrees, group II: 3.6 degrees +/- 2.6 degrees; p=0.005). Postoperative refractive cylinder was -0.89 +/- 0.35 Din group I and -0.64 +/- 0.36 Din group II (p=0.003). Visual acuity was comparable between both the groups. Visual quality measured in terms of Strehl ratio (p<0.05) and modulation transfer function (MTF) (p<0.05) was significantly better in the image-guided surgery group. Significant negative correlation was observed between deviation from target axis and visual quality parameters (Strehl ratio and MTF) (p<0.05). Conclusion: Image-guided surgery allows precise alignment of toric IOL without need for reference marking. It is associated with superior visual quality which correlates with the precision of IOL alignment.