Capsulotomy size may shift effective lens position, data suggest

A larger anterior capsulotomy moved the intraocular lens (IOL) posteriorly in eyes with thin crystalline lenses and anteriorly in eyes with thick ones, shifting effective lens position (ELP) by roughly 120 µm in each direction, according to a prospective paired-eye study that earned Best Paper of Session at the ASCRS Annual Meeting earlier this year. David Folden, MD, of Twin Cities Eye Consultants presented the findings and told Ophthalmology Times that capsulotomy diameter may function as a modifiable refractive variable rather than a neutral surgical parameter.

Why does effective lens position resist prediction?

ELP cannot be measured directly before surgery. Biometry supplies axial length, anterior chamber depth (ACD), and other inputs, and formulas use them to predict where the optical plane of the IOL will settle. Formulas do not account for surgically created anatomy, Folden said, and the anterior capsule falls outside their inputs. Capsular contractile forces and the way the bag remodels around the implant can settle the IOL slightly anterior or posterior to the predicted position.

Folden routinely adjusts capsulotomy diameter intraoperatively based on pupil dilation, cataract density, and lens thickness, which prompted the question of whether that adjustment was itself influencing where the lens ultimately settled.

How was the study designed?

Folden conducted a prospective, randomized, contralateral paired-eye study of 40 eyes from 20 patients. A computer-generated sequence assigned one eye to a 4.6 mm capsulotomy and the fellow eye to a 5.6 mm capsulotomy. Both diameters remained within the optic border, preserving 360° of anterior capsule overlap. Every eye received the same single-piece acrylic IOL with a planar optic-haptic design and 6 mm optic. Postoperative ACD at 3 months served as the ELP proxy. Folden measured it with swept-source OCT imaging in dilated and undilated states and subtracted preoperative ACD from each eye.¹

What did the study find?

Across the full cohort, the larger capsulotomy positioned the IOL approximately 59 µm posterior. Stratifying by preoperative lens thickness reversed that picture. Among the 5 patients with the thinnest lenses, ACD increased from 1.468±0.23 mm to 1.581±0.44 mm with the larger capsulotomy, a posterior shift of 0.113 mm. Among the 5 with the thickest lenses, ACD decreased from 2.067±0.23 mm to 1.944±0.19 mm, an anterior shift of 0.123 mm. Folden described the split at a 5 mm lens thickness cutoff, reporting roughly 119 µm posterior movement in thin lenses and 123 µm anterior movement in thick lenses.

At a 20-diopter lens power, Folden estimated that a 120 µm positional change produces 0.10 to 0.15 D of refractive effect, scaling upward with higher-power lenses. He characterized the results as directional trends that established proof of principle without reaching statistical significance, and called for a larger, more powerful study.

What should surgeons do now?

"The capsulotomy diameter variability is not refractive neutral. That's what I would take home from this study," Folden told Ophthalmology Times.

For now, Folden recommended consistency over deliberate manipulation: use a repeatable anterior capsulotomy diameter, reanalyze postoperative outcomes, and optimize surgeon-specific IOL formula constants. A validated nomogram, he said, could eventually permit patient-specific customization of the diameter to tighten refractive results.

Reference
1. Folden D. The effect of capsulotomy size on effective lens position in robotic laser cataract surgery. Presented at: ASCRS Annual Meeting; April 10-13, 2026; Washington, DC.