IOLMaster® uses a partial coherence interferometer to determine the anterior corneal curvature by projecting six lights in a hexagonal array onto 2.3 to 2.5 mm diameter from the corneal apex. Partial Coherence Interferometer – (IOLMaster®) Exclusion criteria included smokers, history of intake of lutein and zeaxanthin, presence of significant media opacity (corneal scar, cataract, vitreous hemorrhage), findings of AMD, other ocular diseases like optic atrophy and retinopathies, previous retina lasers or surgeries, and history of intake of chloroquine, hydroxychloroquine, ethambutol, and tamoxifen.Ī. Study Operational Definitions: They were at least 18 years old with corrected visual acuity of at least 20/20. This study determines if there is a significant difference between the keratometry values and computed IOL power calculation between the two machines through a retrospective chart review of patients who had undergone keratometry measurements using both IOLMaster® and iTrace® in an outpatient surgicenter. As with any new device introduced into clinical practice, studies that compare it with the most common clinically accepted device are warranted. In this study, we compared the keratometry values of iTrace® (Tracey™ Technologies, Texas, 1999) and IOLMaster® (Carl Zeiss Meditec, Germany, 1999), using the latter as the gold standard. In calculating an accurate IOL power, biometry data – which include axial length (AL), keratometry (K) values and anterior chamber depth (ACD) – are necessary.3 With improvements in measuring axial length, keratometry is the next important source of potential biometry error.4 Keratometry involves determination of the curvature of the anterior corneal surface, expressed in diopters (D) or in mm of radius of curvature.5 The automated keratometer (IOLMaster®), currently the gold standard for biometry, measures anterior curvature using six points of light arranged in a hexagonal pattern within a 2.3 to 2.5 mm diameter ring compared to ray tracing (iTrace®) which measures the anterior curvature within the zone of 3 mm.6 Because the IOLMaster® measures only six points on a 2.5 mm ring and does not use Snell law, it overestimates the power within the zone below 4.5 mm and then underestimates the zonal power above 4.5 mm.4 In order to minimize measurement errors and improve patient satisfaction, it was hypothesized that iTrace®, which obtains zonal average keratometry values, will then give a different representation of the central refractive power of the cornea. Despite the introduction of optical biometers, residual spherocylindrical refractive error after surgery is not uncommon.2 Phacoemulsification is one of the most successful and commonly performed cataract surgeries worldwide.1 With the advent of toric intraocular lenses (IOLs) IOLs and refractive surgical techniques, patients now demand for independence from spectacles after cataract surgery.
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