Collagen Shrinkage Techniques

Alteration in corneal biomechanics can also be achieved by collagen shrinkage. Heating collagen to a critical temperature of 58°–76°C causes it to shrink, inducing changes in the corneal curvature. Thermokeratoplasty and conductive keratoplasty (CK) are avoided in the central cornea because of scarring but can be used in the midperiphery to cause local collagen contraction with concurrent central corneal steepening (Fig 1-19; see also Chapter 7).

Figure 1-18 Schematic illustrations showing placement of intrastromal corneal ring segments.

(Illustrations by Jeanne Koelling.)

Figure 1-19 Schematic diagrams of thermokeratoplasty and conductive keratoplasty. Heat shrinks the peripheral cornea, causing central steepening

(arrows).

Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.