Figure 6-4 A, Schematic illustration of myopic photorefractive keratectomy. The shaded area refers to the location of tissue subtraction. More stromal tissue is removed in the central than in the paracentral region. B, Schematic illustration of hyperopic laser in situ keratomileusis. A superficial corneal flap is raised. The shaded area refers to the location of tissue subtraction under the thin flap. After treatment, the flap is repositioned. (Used with permission from Poothullil AM, Azar DT.

Terminology, classification, and history of refractive surgery. In: Azar DT, ed. Gatinel D, Hoang-Xuan T, associate eds. Refractive Surgery. 2nd ed. St Louis: Elsevier-Mosb y; 2007:5–6. Figs 1-4, 1-5.)

Azar DT, ed. Gatinel D, Hoang-Xuan T, associate eds. Refractive Surgery. 2nd ed. St Louis: Elsevier-Mosby; 2007.

Azar DT, Primack JD. Theoretical analysis of ablation depths and profiles in laser in situ keratomileusis for compound hyperopic and mixed astigmatism. J Cataract Refract Surg. 2000;26(8):1123–1136.

Klyce S. Night vision after LASIK: the pupil proclaims innocence. Ophthalmology. 2004;111(1):1–2.

Munnerlyn CR, Koons SJ, Marshall J. Photorefractive keratectomy: a technique for laser refractive surgery. J Cataract Refract Surg. 1988;14(1):46–52.

Angle Kappa

As discussed in Chapter 2, the pupillary axis is the imaginary line that is perpendicular to the corneal surface and passes through the midpoint of the entrance pupil. The visual axis is the imaginary line that connects the point of fixation to the fovea. The angle kappa (κ) is defined as the angle between the pupillary axis and the visual axis. A large angle kappa results from a significant difference