This was done to achieve an outcome as close as possible to emmetropia. The purpose of this study was to compare two different methods of analysis of pre-operative reference marking for Toric IOL after marking with an electronic marker (e-marker) and also the accuracy of the electronic marker as a means of establishing the reference point for the final alignment of the Toric IOL. The amount of alignment error (in degrees) from the horizontal, by both methods was calculated. The reference marks were analysed by two different methods using Tracey iTrace Visual Function Analyser (version 5.1.1) and Adobe Photoshop (version 7). In our series, all patients had pre-operative marking of the eye done with an electronic pre-operative Toric IOL reference marker. Lastly, Toric IOL is implanted and rotated to match the alignment marks. Second step is intra operative, where an angular graduation instrument is used to align the axis of the toric IOL. Usually a reference marker or a slit lamp is used for this purpose. First step is the pre- operative marking where the horizontal axis (0 to 180 degrees) is marked with the patient in sitting position.
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6 However most methods follow a 3-step procedure. 5 Various methods have been described to align the toric IOL during cataract surgery. This is the most important step of surgery and IOL misalignment may take place either due to inaccurate IOL placement, or IOL rotation, or both. 4, 5 Alignment of the toric intraocular lens at the calculated alignment axis is necessary to achieve effective astigmatism correction. 3In today’s modern age, Toric intraocular lens (IOL) are an integral part of cataract and refractive surgery, and are commonly used to correct preexisting corneal astigmatism in cataract patients. These may be non surgical options like spectacles or contact lenses, or surgical options like photorefractive keratectomy, laser in situ keratomileusis, and laser-assisted sub epithelial keratomileusis astigmatic keratotomy using limbal or corneal relaxing incisions opposite clear corneal incisions (OCCI) and toric phakic or pseudophakic intraocular lens (IOL). 1, 2 Over the years, many treatment options have been described for correcting corneal astigmatism. Various studies have shown that the number of patients having pre existing astigmatism of more than 1.5 Dioptres ranges from 15% to 29%. Patients with cataract commonly have pre- existing astigmatism. Keywords:electronic reference marker, iTrace, toric IOL Abbreviations This can be further compounded by intra-operative marking errors and final placement of IOL in the bag. Both analysis methods showed an approximately 3° of alignment error, which could contribute to 10% loss of astigmatic correction of Toric IOL. No significant difference in absolute amount of rotation between eyes when analyzed by either method.Ĭonclusion: Difference in reference mark positions when analysed by two systems suggest presence of varying cyclotorsion at different points of time.
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72.7% eyes by Photoshop and 61.4% by iTrace had rotation error ≤3° (p=0.359) and 90.9% eyes by Photoshop and 81.8% by iTrace had rotation error ≤5° (p=0.344). Results: Mean absolute rotation error was 2.38☑.78° by Photoshop and 2.87☒.03° by iTrace which was not statistically significant (p=0.215). Amount of alignment error was calculated. Secondly, Tracey iTrace Visual Function Analyzer (version 5.1.1) was used for capturing corneal topograph exam and position of marks noted. Firstly, slit-lamp photographs taken and analyzed using Adobe Photoshop (version 7.0). Reference marks were placed at 3-and 9-o'clock positions. All patients had pre-operative marking done with an electronic pre-operative two step Toric IOL reference marker (ASICO AE-2929). Methods: 52 eyes of 30 patients planned for Toric IOL implantation were included. Setting/Venue: Cataract & Intraocular Lens Implantation Service, Shroff Eye Centre, New Delhi, India. Purpose: To compare two different methods of analysis of pre-operative reference marking for Toric IOL after marking with an electronic marker