Abstract
Purpose: :
Proper positioning of TORIC intraocular lenses (IOLs) depends upon pre-operative determination of the axis of astigmatism. We sought to validate a new pre-operative axis marking system for toric intraocular lens (IOL) implantation. We hypothesize that our method will provide accurate axis markings, while reducing costs and increasing operating room efficiency.
Methods: :
We added a calibrated decal to a Haag-Streit slitlamp so we could accurately set the slit at any angle, 0-180º. Typically, the axis for the insertion of the toric IOL is calculated using pre-operative keratometry and biometry. Arbitrary axes were set in our test models. To mark a selected axis on the eye, the slit-beam was positioned so that one end abutted the visual axis, and the other fell on the corneal limbus. With the slit-beam set to the desired angle, it was used to guide a linear superficial epithelial abrasion using a 30-gauge needle at the corneal limbus. For validation purposes, the horizontal axis was marked in the same way. We assessed the accuracy of this technique in two ways: A masked independent observer, blinded to the intended axis, was asked to find the superficial mark and to determine the axis using only the calibrated slit-lamp. We also compared the axis markings made with our method to a currently used intra-operative axis marker (beveled degree gauge, ASICO®).
Results: :
The average error between measurements set by the marker and those estimated by the independent observer was 3.2º (SD= 2.6º). When angles set with the calibrated slitlamp were assessed using the protractor, there was no difference between the intended and the measured axis.
Conclusions: :
The technique outlined can accurately mark the axis for TORIC IOL implantation. It also obviates the need for sterile instrument sets for pre- and intra-operative marking. The technique is thus a simple, adaptable, inexpensive, and accurate method for surgeons interested in offering TORIC IOL technology to their patients.
Keywords: cataract • intraocular lens • astigmatism