A systematic review of these studies revealed that, in patients with significant hyperopia, centering on the corneal light reflex results in better corrected and uncorrected visual acuity, less decentration of the ablation zone, and less higher order aberrations. Studies have looked at outcomes in LASIK surgery when focusing on 1) the center of the pupil, 2) the corneal light reflex, 3) the corneal vertex, and 4) halfway between the center of the pupil and the corneal light reflex in patients with a large angle kappa. ![]() In patients with significant hyperopia refractive surgery outcomes can differ depending on where the laser focuses during the procedure. Clinical Implications of Angle Kappa Refractive Surgery ![]() One study showed that angle kappa decreases with age, but the decrease does not appear to be clinically significant. Additionally, angle kappa tends to be larger in left eyes than right eyes, and in exotropes compared to esotropes. Īngle kappa tends to be larger in hyperopic eyes compared to myopic eyes, which can be clinically significant as will be discussed in the following section. The angle kappa has been further measured by different corneal topography systems, including Syntophore and Orbscan (Bausch and Lomb, Rochetser, NY). The optical axis, the visual axis, and the angle kappa are represented on physical exam by the distance between the pupillary center and the corneal light reflex. CW chord refers specifically to the angle between the subject-fixated coaxially sighted corneal light reflex to the pupil center.įIGURE 2 – CW-chord values as output by SWEPT-source optical biometry – courtesy of Hoon Jung, MD In other literature angle kappa has been called angle lambda and, more recently, CW (Chang-Waring) chord (Figure 2). įIGURE 1 – schematic of eye with optical axes labeled (Courtesy of Randy Lu) ![]() Due to the fact that the fovea lies temporal to where the pupillary axis intersects the posterior pole, a positive angle is formed between the two axes, which is called angle kappa (FIGURE 1). The visual axis has also been referred to as the foveal-fixation axis. In comparison, the visual axis is an imaginary line that connects the object in space, the center of the entrance and exit pupil, and the center of the fovea. The optical axis is composed of an imaginary line perpendicular to the cornea that intersects the center of the entrance pupil. There are two significant optical axes of the eye – the optical axis and the visual axis, which are also referred to in literature as the pupillary axis and the line of sight, respectively.
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