After Collamer Lens Implant, Anterior Structures Stabilize Earlier Than Thought

Traditionally, research has suggested clinicians examine anterior chamber angles (ACAs) of patients with new implantable collamer lenses (ICLs) starting at 1 month. Now, investigators suggest anterior parameters stabilize earlier, and that evaluating status of structures, along with nasal and temporal angles individually, as soon as 1 week may be best to avoid complications, according to data reported in BMC Ophthalmology.

The prospective, single-arm case study assessed 62 right eyes of 62 individuals (mean age, 26.0±4.6 years) with myopia who received Visian^® ICL™ V4c (STAAR Surgical Company) — sphere up to -18.0 D and cylinder better than -6.0 D — at a university hospital in Shanghai, China between February 2021 and May 2021. Preoperative evaluation included anterior segment optical coherence tomography (AS-OCT), ultrasonic biomicroscopy, and others. The follow-up period was 6 months.

In 8 eyes, postoperative intraocular pressure (IOP) was high at 2 hours, but successfully treated. All eyes achieved normal IOP at 4 hours and subsequent visits. Six months postoperatively, mean endothelial cell density (ECD) was similar to baseline (P =.204). Central anterior chamber depth (ACD) and anterior chamber volume decreased significantly at all examinations, compared with preimplant (P <.001), but central ACD stabilized approximately 1 day after surgery, and anterior chamber volume at 1 month. Posterior vault also decreased at 1 day, 1 week, and 1 month, then was stable.

Nasal ACA and temporal ACA decreased significantly at 1 day and 1 week (P <.001), but remained stable starting at 1 month, with the temporal angle marginally wider than nasal ACA. Postsurgical ACA measurements significantly, positively correlated with preoperative central ACD, anterior chamber volume, and ACA. These associations suggest individuals with shallower ACD or angles less than 20° should be cautious when selecting ICLs, according to the researchers.

Previous studies established ideal vaults at 250 μm to 750 μm, acceptable to 1000 μm. In the current analysis, 90.3% of eyes achieved the ideal range, and 9.7% were within 750 μm to 1000 μm. Vault height is reduced as sodium hyaluronate metabolizes and aqueous circulates, the research explains, and abnormalities may be caught before 1 month. “Specifically, the evaluation of the relative stability of the vault within 1 week after ICL V4c implantation is particularly crucial to guide the early replacement with more appropriate ICL if there is a risk of cataract,” the researchers report.

Early widening of the temporal angle may result from incision location, including remaining viscoelastic on that side, the analysis notes. Differences in nasal and temporal angles resolve upon healing, and investigators advise monitoring ACA parameters at 1 week to notice changes such as angle adhesion or pigment dispersion. 

This investigation is limited by lack of comparison for both eyes of the same participant, a cohort all younger than 40 years of age, and no data for various ICL diameters. Statistical difference was shown, but not clinical significance. Strengths involve AS-OCT imaging in the same lighting intensity for baseline and post-implantation visits, and inclusion of those with wide-ranging spherical equivalent refraction, from -3.0 D to -11.5 D.