Refractive Outcome, Lens Power Calculation, and Surgically Induced Astigmatism After Four-Flanged Intrascleral Intraocular Lens Fixation.

Purpose: To evaluate the refractive prediction error of common intraocular lens (IOL) power calculation formulas in patients who underwent intrascleral IOL fixation using the four-flanged technique.

Methods: This prospective, longitudinal, single-site, single-surgeon study's setting was the Department for Ophthalmology and Optometry, Medical University of Vienna, Austria. Patients who received IOL implantation via the four-flanged technique were followed up to 3 months after the operation. Refraction was measured using the Early Treatment of Diabetic Retinopathy Study visual acuity test at 4 m. Lens decentration, tilt, and aqueous anterior chamber depth were evaluated using anterior segment optical coherence tomography. The SRKT, Holladay 1, and Hoffer-Q formulas were used to assess prediction error (PE) and absolute error (AE). Correlations between axial length, keratometry, and white-to-white distance were subsequently evaluated.

Results: A total of 28 eyes of 28 patients were examined in this study. The application of all formulas resulted in a hyperopic PE (SRKT: 0.35 ± 0.86 diopters [D], Holladay 1: 0.36 ± 0.78 D and Hoffer-Q: 0.37 ± 0.73 D). There was no variation between the PE of different formulas discovered (P > .05). The AE was within 0.50 D in 54% to 61% and within 1.00 D in 79% of eyes, depending on the formula used. Furthermore, Cochrane's Q test detected no significant distinctions between formulas (P > .05). The PE of each formula demonstrated a significant correlation to the axial length of the eyes (P < .05). The correlation estimates ranged from -0.25 D/mm to -0.39 D/mm, subject to the applied formula.

Conclusions: This study demonstrates that the four-flanged technique for scleral IOL fixation yields reliable outcomes. PE was closest to zero using the Hoffer-Q formula, although there was no statistically significant difference compared to the other formulas. Axial length emerged as the most pertinent factor for PE. Short eyes resulted in a more hyperopic outcome, whereas longer eyes resulted in a more myopic outcome than intended. This myopic and hyperopic shift was due to the standardized surgical technique with an externalization of the haptics 2.5 mm behind the limbus resulting in a consistent aqueous anterior chamber depth across all eye lengths, coupled with a reduction or increase in the distance from the IOL to the macula, which is dependent on the length of the eye. [J Refract Surg. 2024;40(12):e985-e993.].