My name is Dr. Robert Melendez. I am an ophthalmologist in private practice at the Juliette Eye Institute in Albuquerque, New Mexico, where I specialize in advanced cataract and refractive surgery. My colleagues and I recently conducted an investigator-initiated trial comparing the performance of two swept-source optical tomography (or SS-OCT) devices: the ARGOS® SS-OCT biometer and the IOLMaster^ 700. The goal of the study was to evaluate the prediction accuracy of these two biometers with respect to toric intraocular lens power selection. To do this, we carried out a retrospective chart review of 61 eyes with corneal astigmatism from 45 patients who underwent either cataract surgery or refractive lens exchange. Measurements were collected with both biometers prior to surgery, and pre-operative toric IOL power and orientation calculations were performed on all patients using the Barrett TK Toric formula. All study eyes were planned for implantation with a toric IOL, however one eye received a non-toric IOL based on intraoperative aberrometry results. Cylinder and manifest refraction spherical equivalent prediction errors were measured one month after IOL implantation. Mean cylinder prediction accuracy differed statistically between ARGOS® and the IOLMaster^ 700, but this difference was not judged to be clinically significant. The ARGOS® biometer tended to underestimate post-operative cylinder, while the IOLMaster^ 700 tended to overestimate this measure. Overall, however, the magnitude of the error with each biometer was approximately the same, and there was no significant difference in the proportion of eyes with cylinder prediction error within 0.50 D. The magnitude of the manifest refraction spherical equivalent prediction error with ARGOS® and the IOLMaster^ 700 also differed statistically, but this difference was also judged to be clinically insignificant. The percentage of eyes with MRSE prediction within 0.50 D, however, was significantly greater with ARGOS®. Overall, 80.3% of eyes were within 0.50 D for ARGOS, versus 59% of eyes with the IOLMaster^ 700. The presence of clinically meaningful astigmatism is common among cataract patients, and if this refractive error is not adequately corrected, post-operative vision can suffer. Toric IOLs provide an opportunity for excellent astigmatism correction when refractive outcomes are accurately predicted. Therefore, finding ways to optimize biometric measurement of astigmatic eyes and toric IOL power selection is crucial. The technical principles behind SS-OCT biometry enable rapid and accurate acquisition of biometric measurements. ARGOS® is unique among SS-OCT biometers — it uses 1060 nm wavelength light and specific refractive indices of the cornea, lens, aqueous, and vitreous segments for its biometric measurements. Most notably, our study revealed that using the ARGOS® biometer produced a greater percentage of eyes with MRSE prediction error within 0.50 D than the IOLMaster 700^. We also found no clinically significant difference in the cylinder prediction accuracy of these two SS-OCT biometers. Broadly, our findings suggest that the ARGOS® biometer can help cataract surgeons improve their overall toric IOL power selection accuracy for patients with cataract and corneal astigmatism.
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