This cross-sectional study enrolled patients who underwent unilateral implantation of an IC-IOL (Artisan®; Ophtec, Groningen, The Netherlands) at the Ophthalmology unit of the University Hospital of Parma (Parma, Italy). The study protocol was approved by the local ethics committee (#483/2018). The study was conducted in accordance with the Declaration of Helsinki, and written informed consent was obtained from all patients. The study included patients aged ≥ 18 years who underwent PC implantation of an IC-IOL in an aphakic eye 6 months to 3 years before data collection. We excluded patients with history of traumatic aphakia, perioperative IC-IOL disenclavation, postoperative conditions that prevent visualization of the anterior segment, bilateral IC-IOL implantation, extended iris atrophy, or iridodialysis. The medical history of the patients was reviewed to identify drug use that may affect pupillary motility. The patients were examined to record the best corrected visual acuity (BCVA) using the Early Treatment of Diabetic Retinopathy Study chart placed at 4 m, slit-lamp examination findings, intraocular pressure using pneumotonometry, and AS-OCT findings.

After removing the remnants of the lens material or unsuitable IOL, if needed, limbal paracentesis was performed at the 3 o’clock position (both study surgeons, PM and ST, are right-handed), and the viscoelastic medium was injected. A clear corneal 5.5-mm incision was made superiorly, and the IC-IOL (with the vault facing down) was inserted into the anterior chamber. The IOL was rotated so that the haptics were located at the 3 and 9 o’clock positions, and then pushed behind the undilated pupil. After making the appropriate centration adjustments, the haptics were alternately slightly pushed against the mid-peripheral iris stroma and enclavated using a smooth microspatula. Finally, the corneal incision was sutured using a non-continuous 10–0 non-absorbable nylon, which was removed 6–9 weeks after surgery. Postoperatively, conventional antibiotics and nonsteroidal anti-inflammatory eye drops were administered for 5 weeks. An Artisan® IOL (Ophtec, Groningen, The Netherlands) was implanted in all cases. The IOL power was selected to achieve emmetropia and was calculated using the SRK/T formula with an A constant of 117.1.

The patients underwent MS-39 imaging (Phoenix v.4.0.1.8; CSO, Florence, Italy) of both eyes. This device performs spectral domain OCT (SD-OCT) and placido-disk corneal topography to provide automated measurements of the anterior segment of the eye. After autocalibration, the scanning tool performs keratoscopy, measurements of the iris front profile for pupil identification, and a series of 25 radial scans within approximately 1 s. The device performs pupillography using a superluminescent light emitting diode source placed at 950 nm and provides an axial resolution of 3.6 μm in tissue and transversal resolution of 35 μm in air [15]. The device is equipped with built-in software for the measurement of the PD under three light conditions: scotopic (S, 0.04 lx), mesopic (M, 4 lx), and photopic (Ph, 50 lx). The quality of the acquired scans was confirmed by the study operators, and measurements were obtained for both eyes. The IC-IOL eyes were included in the IC-IOL group, and the fellow eyes (phakic or pseudophakic) were included in the control group. During mesopic assessment, also pupil circularity was estimated by calculating the ratio between the major and minor axes of the pupil. The PD was then measured with the eyes under pharmacological mydriasis, obtained referring to a known scheme [16]: 1% tropicamide eye drop followed by 10% tropicamide + 0.5% phenylephrine eye drop after 5 and 30 min; the mydriasis assessment was performed after 45 min.

Two weeks later, the examination was repeated with pharmacological miosis of the involved eyes (study and control group) obtained using the instillation of commercial 2% pilocarpine eye drops.

Descriptive statistics (i.e., mean and standard deviation [SD]) are provided for variables of interest. The Shapiro–Wilk test was used to determine the normality of the distribution of the data. A paired t-test was used to evaluate differences between the IC-IOL and control groups. Statistical analyses were performed using SPSS (version 28.0.0; IBM Corp, Armonk, NY, USA), and p < 0.05 was considered statistically significant.