Vector analysis of astigmatism correction after toric intraocular lens implantation

PURPOSE: To determine astigmatic changes by vector analysis and postoperative refractive and visual outcomes after implantation of the monofocal aspheric bitoric AT Torbi 709M toric intraocular lens (IOL). SETTING: Three centers in Salzburg, Austria, and Alicante and San Sebastián, Spain. DESIGN: Prospective interventional case series. METHODS: Preoperative and postoperative visual acuity, subjective and objective refractions, and corneal radii using a topographer were examined in all patients. All patients had postoperative examinations within the first week and at 6 to 12 weeks. Astigmatic changes were evaluated using the Alpins vector method based on 3 fundamental vectors as follows: target induced astigmatism (TIA), surgically induced astigmatism (SIA), and difference vector. The various relationships between these 3 vectors were calculated, providing an extensive description of the astigmatic correction achieved. RESULTS: Eighty-eight eyes (71 patients) were included. Postoperatively, refractive cylinder was reduced significantly (P < .001), concurrent with visual improvement. The mean magnitude of the SIA vector (2.54 diopters [D] ± 1.21 [SD]) was slightly higher than the mean magnitude of the TIA vector (2.37 ± 1.15 D) at the last follow-up. The mean difference vector was 0.46 ± 0.46 D, the mean magnitude of error was 0.16 ± 0.46 D, and the mean correction index was 1.09 ± 0.21, all indicating minimal overcorrection at 3 months that remained stable during the follow-up. CONCLUSION: Implantation of the toric IOL was safe and effective for the treatment of eyes with cataract in combination with preexisting regular corneal astigmatism over a short-term follow-up. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.