A Case Of Low Vault After Acrylic Posterior Chamber Phakic Iol

Determination of the cause of low vault in a patient after implantation of a posterior chamber acrylic PIOL

A 29-year-old man had high bilateral myopia. His CDVA was 0.6 LogMAR and 0.48 LogMAR in the right and left eyes, respectively. In the right eye, the SE was 15.88D; in the left eye, it was 15.63D. His IOP was 13.0/12.0mmHg, and his corneal endothelial cell density (ECD) was 2516/2556mm2

Posterior chamber acrylic PIOLs (EYECRYL Phakic Toric, Biotech), which are foldable hydrophilic acrylic one-piece posterior chamber IOL, were implanted in the both eyes of the patient in February 2021.

Anterior segment optical coherence tomography (CASIA II AS- OCT) was used to measure (WTW), angle-to-angle distance (ATA), anterior chamber width (ACW), crystalline lens rise (CLR), internal anterior chamber depth (ACD endo), trabecular iris angle (TIA 500). One month after the surgery. The PIOL size and the dioptric power were determined using the manufacturer's calculator. For the right eye the calculation made D-17.0cyl +2.0Ax90 with 13.0mm length; for the left eye it was D-16.0cyl +2.0Ax90 with 12.5mm length.

The patient’s vision one month after the surgery was as follows: UDVA - 0.4 LogMAR in both eyes. In the right eye, SE was +0.25D, and in the left eye, it was -0.25D; the IOP was 15.0/13.0 mmHg, the corneal endothelial cell density (ECD) was 2510/2525 mm2The vault in the right eye was 6μm and the left eye arch was 350μm, ASDendo was 2270μm in the right eye and 2220 in the left one.

Given the very low vault in the right eye, we have re-analyzed the preoperative anatomical parameters of the anterior segment of both eyes of the patient.

The examination of the right eyes showed 11.82mm WTW, 11.88mm ATA, 12.05mm ACW, 455µm CLR, 2.86 mm ACDendo. The left eye showed: 11.69mm WTW, 11.43mm ATA, 11.41mm ACW, 350µm CLR, 2.84mm ACDendo.  In the right eye, the PIOL implantation resulted in the narrowing of the anterior chamber angle with a minimum TIA opening of 18⁰; before the surgery it was 38⁰. In the left eye, the surgery made 27⁰angle opening; before the surgery it was 30⁰

In the right eye, WTW, ATA, ACW values were greater than in the left eye. Accordingly, a greater PIOL length was calculated for the right eye, but the vault turned to be very low. In our opinion, it was caused by the high CLR value. If an even larger PIOL is implanted, there will be a greater narrowing of the anterior chamber angle. Therefore, PIOL implantation in the right eye could not be recommended.