Implantable Collamer Lens Geometry Has Limited Impact on Vault Differences

Implantable collamer lens (ICL) geometry has a limited influence on the vault, according to a report published in BMC Ophthalmology.

Researchers conducted a retrospective case series to evaluate the influence of ICL geometry — spherical and toric — on the vault and reported refractive and visual outcomes achieved by patients bilaterally implanted with a spherical ICL (sICL) in an eye and an equal sized toric ICL (tICL) in the fellow eye. “[T]he present results do not show significant influence of tICL geometry on the vault, suggesting that ICL geometry plays a minor role in vault magnitude,” researchers report.

The team assessed anatomical and ICL-related parameters using anterior-segment optical coherence tomography and optical coherence tomography. They used generalized estimating equations incorporating inter-eye correlations to determine the influence of these parameters on the vault.

A total of 41 patients (mean age of 31.9±8.1 years [range, 21-50]; 56.1% women, 43.9% men), were included in the study. The researchers reported implantation of 12.6 mm ICLs in 9 patients, 13.2 mm ICLs in 24 patients, and 13.7 mm ICLs in 8 patients.

The team found the postoperative spherical equivalent was within ±0.50 diopter in 66% of eyes implanted with sICL and 83% of eyes implanted with tICL. They reported an efficacy index of 1.06 in the sICL eyes and 1.14 in the tICL eyes. 

The researchers found a mean inter-eye vault difference of -1.46 µm and demonstrated similar associations of anatomical and ICL-related parameters with the vault for sICL and tICL. Using generalized estimating equations, they found the ICL size minus the anterior chamber width (ATA; B-unstandardized coefficient [B], 386.53; 95% confidence interval [CI], 215.96-557.10; P <.0001), ICL spherical power (B, -21.96; 95% CI, -39.13 to -4.79; P =.013), and ICL central thickness (B, 2.84; 95% CI, 0.60-5.83; P =.034) were significant factors influencing the vault.

“[T]he selection of the ICL size should follow a hierarchical approach with factors such as the ICL size minus the ATA and the ICL power assuming higher relevance. In borderline cases, where two ICLs sizes would be adequate the rotation stability of the tICL needs to be considered and combined with higher hierarchical factors to select the adequate ICL size,” according to the researchers.

Limitations of the study included the retrospective design, lack of a planned randomization process, and relatively small sample size.