Intacs to stabilize diurnal variation in refraction after radial keratotomy

Intraocular lens power calculation after two different successive corneal refractive surgeries

Purpose

To report two challenging intraocular lens power calculation cases with patients each underwent different successive corneal refractive surgeries, respectively.

Observations

Biometry data, including the Back to Front corneal radii ratio (B/F ratio), were collected by Lenstar, IOL Master, and Pentacam AXL for Case 1 (received radial keratotomy (RK) and photorefractive keratectomy (PRK)) and Case 2 (received RK and laser-assisted in situ keratomileusis (LASIK)). The IOL power calculation was determined by several methods, including Shammas, Haigis-L, and Barrett True-K, which are available in the American Society of Cataract and Refractive Surgery online calculator and Pentacam AXL. The Barrett True-K (no history, post-RK) was more accurate in Case 1 (increased B/F ratio), whereas the Shammas, Haigis-L, and Barrett True-K (no history, post-LASIK/PRK) were more accurate in Case 2 (decreased B/F ratio).

Conclusion and importance

The B/F ratio may be a factor to be considered when selecting the IOL power calculation formula for patients who undergo two different corneal refractive surgeries. The further study focusing on this issue should be performed to clarify the results in the future.

[On the question of progressive hyperopia correction after radial keratotomy]

Progressive hyperopia development in the long-term period after radial keratotomy (RC) is associated with not only surgical effects, but also individual biomechanical features of the fibrous tunic of the eye, its age-related changes, and hydrodynamic disturbances. When choosing a method of correction, one should take into account a number of features characteristic of this induced refractive disorder: instability and irregularity of refraction, coexisting presbyopia, and, in some cases, anisometropia. Correction of progressive hyperopia after RC can be achieved with eyeglasses, or contacts, or intraocular lenses depending on the subjective factor - the so-called patient adherence. The most effective in terms of functionality is contact correction with scleral rigid gas-permeable lenses, and in the presence of pronounced lens opacities - intraocular correction.