Primary observations of EVO ICL implantation for high myopia with concave iris.

Purpose: To investigate the morphological changes of concave iris in myopic patients after EVO implantable collamer lens (ICL) implantation.

Methods: EVO ICL candidates with posterior bowing iris were observed using ultrasound biometric microscopy (UBM) in this prospective nonrandomized observational study. Forty patients were enrolled, with 20 patients in the concave iris group and the other 20 patients in the control group. None of the patients underwent laser peripheral iridotomy. All patients received preoperative and postoperative examinations, which included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), subjective manifest refraction and intraocular pressure. UBM was used to observe iris curvature (IC), irido-corneal angle (ICA), posterior chamber angle (PCA), iris-lens contact distance (ILCD), iris-zonule distance (IZD) and ciliary process length (CPL). Anterior chamber angle pigment was observed by gonioscopy. The preoperative and postoperative data were analyzed using SPSS.

Results: The average follow-up period was 13.3 ± 5.3 months. The mean efficacy indices were 1.10 ± 0.13 and 1.07 ± 0.11 (P = 0.58), and the safety indices were 1.19 ± 0.09 and 1.18 ± 0.17 in the control group and the concave iris group (P = 0.93), respectively. The IOP postoperatively were 14.13 ± 2.02 mmHg and 14.69 ± 1.59 mmHg in control and concave iris groups (P = 0.37). Preoperatively, the concave iris group was presented with greater IC (P < 0.0001), longer ILCD (P < 0.0001), wider ICA (P = 0.004), narrower PCA (P = 0.01), and shorter IZD (P = 0.03) than the control group. In the concave iris group, IC, ILCD and ICA were significantly decreased after ICL implantation (P < 0.0001), while PCA and IZD were significantly increased (P = 0.03 and P = 0.04, respectively). Postoperative IC, ILCD, ICA, PCA and IZD were not statistically different between groups (P > 0.05). There was no significant difference in pigment deposition grades between the two groups (P = 0.37).

Conclusion: After EVO ICL implantation, the morphology of concave iris was significantly improved, which may reduce the risk of intraocular pigment dissemination caused by iris concavity. The concave iris has no impact on the safety of EVO ICL surgery during the follow-up.