A central island is defined as a steepening of at least 1.00 D with a diameter of less than 1 mm compared with the paracentral flattened area. A central island appears on computerized corneal topography as an area of central corneal steepening surrounded by an area of flattening that corresponds to the myopic treatment zone in the paracentral region (Fig 6-2). Central islands may be associated with decreased visual acuity, monocular diplopia and multiplopia, ghost images, and decreased contrast sensitivity.
Figure 6-2 Corneal topography findings of a myopic ablation (blue) with a central island (yellow) in the visual axis.
(Courtesy of Roger F. Steinert, MD.)
The occurrence of central islands has been reduced significantly through the use of scanning and variable-spot-size lasers and is now rarely encountered with modern laser technology. Fortunately, most central islands diminish over time, especially after surface ablation, although resolution may take 6–12 months. Treatment options such as topography-guided ablations may be helpful in treating persistent central islands.
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.