In addition, some reports have shown that Lenstar and iTrace are also commonly used to estimate angle kappa. Pentacam has been increasingly popular in measuring angle kappa for the past few years. With the improvements of higher precision in biometers, newer instruments measuring angle kappa are applied in clinical practice. The exact angle kappa is commonly measured using a synoptophore or major amblyoscope which has not become commercially available. Many devices have been commercially released for measuring angle kappa. Therefore, angle kappa is clinically significant to consider in the preoperative assessment of patients. Similarly, during intraocular refractive surgery implantation of the intraocular lens (IOL), especially the multifocal intraocular lens (MIOL), a large angle kappa can increase the risk for photic phenomena including halos, glare, and dysphotopsia. In keratorefractive surgery with a large angle kappa, there is a greater chance of the decentration of ablation zones, and it may lead to negative visual effects such as irregular astigmatism and undercorrection. Īngle kappa is a crucial examination for some surgical decisions in ophthalmology. A positive angle kappa of 5.0° on average is generally found in the normal human eye. Additionally, angle kappa can be classified as horizontal or vertical on the basis of X and Y Cartesian values of angle kappa. According to the light reflex located in the pupillary center, angle kappa can be classified as positive (nasal) or negative (temporal). The visual axis connects the fovea with the fixation point this line passes the nodal, and the pupillary axis is the line passing through the center of the pupil perpendicular to the cornea. The measurement of preoperative angle kappa in the eyes of patients with cataracts by Pentacam and Lenstar has good agreement.Īngle kappa represents the angle between the visual axis and the pupillary axis. The 3 devices provided high intraoperator repeatability and interoperator and intersession reproducibility for angle kappa measurements.
Positive angle kappa (nasal light reflex) was found in most cataract patients (79.25% to 84.91%) through 3 different devices in both eyes. Angle kappa was not significantly different between Pentacam and Lenstar ( P > 0.05), while angle kappa was significantly different between Pentacam and iTrace and between Lenstar and iTrace ( P 0.05). Intraoperator repeatability and interoperator and intersession reproducibility of angle kappa showed an Sw of less than 0.05 mm, a 2.77 Sw of 0.14 mm or less, and an ICC of more than 0.96.
The difference, correlation, and agreement between devices were evaluated by paired t-tests, Pearson tests, and Bland-Altman analysis, respectively. The repeatability and reproducibility were evaluated using the within-subject standard deviation (Sw), repeatability (2.77 Sw), and intraclass correlation coefficient (ICC). When considering dependent eyes for one individual, angle kappa in both right eyes and left eyes should be analysed separately. Each eye was examined 3 times using all devices to obtain angle kappa and pupil diameter. One hundred thirteen eyes of 113 patients with cataracts were included.
This study aims to compare preoperative angle kappa in the eyes of cataract patients obtained from the Pentacam Scheimpflug system (Pentacam), optical low-coherence reflectometry (Lenstar), and ray-tracing aberrometry (iTrace). Large angle kappa is related to a higher risk of postoperative photic phenomena. Angle kappa plays a vital role in the implantation of multifocal intraocular lens (MIOL).
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