Surgically Induced Astigmatism Following Combined Phakic Intraocular Lens Explantation And Cataract Surgery Through The Same Corneal Incision

Surgically induced astigmatism (SIA) has been discussed as the variation in corneal astigmatism resulting from corneal incisions. Despite growing evidence regarding SIA in phakic intraocular lens (pIOL) implantation, there is little evidence regarding SIA after pIOL explantation. When pIOL explantation requires an incision larger than 5 mm, most surgeons choose the scleral approach because of theoretical induction of greater astigmatism through corneal incisions. However, there is no scientific evidence to quantify this astigmatism and its predictability. Thus, the purpose of this work was to study the variation in corneal power after pIOL explantation combined with standard phacoemulsification surgery through the same corneal incision.

Refractive Surgery Unit of the Ophthalmology Department of Unidade Local de Saúde de Santo António (ULSSA), a tertiary hospital in Oporto, Portugal.

We conducted a vector analysis of a dataset of 146 eyes from 101 patients submitted to phakic IOL explantation combined with phacoemulsification surgery. All patients had been previously implanted with Artisan Myopia 206 (Ophtec). Surgical technique consisted of a 90º clear corneal 5.2 mm incision, which was used for pIOL explantation. Corneal tomography was performed with Scheimpflug camera (Pentacam® - Oculus) preoperatively and at 6, 12 and 24 months after surgery. Total corneal refractive power in 2 mm, 3 mm, and 4 mm diameter was considered to calculate the centroid value of the SIA according to the method published by Koch et al. Higher and lower order aberrations regarding anterior and posterior corneal surfaces were also compared.

The centroid value was 1.14 ± 0.76 D, 0.98 ± 0.69 D, and 0.94 ± 0.63 D in the vertical meridian in the 1 mm, 2 mm, and 4 mm radius, respectively. With the corneal incision at 12 o'clock position, the flattening in the 90º meridian results in a SIA of around 1.0 D in most patients, independent of diameter measured. There were no significant differences regarding root mean square higher order aberrations (RMS-HOA) regarding both the anterior (mean ± standard deviation 1.05 ± 0.23 vs. 1.32 ± 0.26, respectively, p=0.532) and posterior corneal surface (0.37 ± 0.06 vs. 0.40 ± 0.07, respectively, p=0.830).

Phakic IOL explantation combined with cataract surgery through the same incision induces a predictable degree of 1.0 D of against-the-rule astigmatism. There seems to be no relevant induction of higher-order aberrations. If this is taken into consideration during IOL power calculation, these patients may be candidates to premium IOL implantation while maintaining spectacle independency.