Topography-guided transepithelial photorefractive keratectomy for irregular astigmatism using a 213 nm solid-state laser

Abstract

213 nm topography-guided transepithelial PRK was easy to perform and well tolerated by patients with irregular astigmatism. Most patients gained CDVA; however, increased haze responses were observed in post-keratoplasty cases.

Irregular Astigmatism After Corneal Transplantation—Efficacy and Safety of Topography-Guided Treatment

“…Undercorrection is generally recommended for TG-PRK, as significant irregular astigmatism can preclude an appropriate evaluation of manifest refraction, and differential ablation rates may contribute to additional uncertainty. 8,10 Altogether, our results and the remaining available small series suggest that TG-PRK offers a valuable option for irregular astigmatism in eyes post-CT. Ablating only the localized defects removes less tissue than correcting a similar amount of regular astigmatism. This sparing of corneal tissue allows treatment of high levels of irregular astigmatism, simultaneously achieving a regular smooth surface.…”

“…Interestingly, it was recently described 13 that eyes after CT can present higher UDVA gains than eyes with other diagnoses (such as decentered optic zone, among others), but that the gain of CDVA can present an opposite trend. 8 Actually, Allan and Hassan 8 observed that CDVA gain was lower in patients with irregular astigmatism after CT than after previous refractive surgery, describing a median gain of 0 lines for CT eyes. The authors justified these outcomes by the development of severe haze in a significant number of cases.…”

“…7 The new treatment protocols already take it into account, performing a final adjustment to the manifest refractive error, but a second procedure may be required to address it. 12 Despite the current evidence that TG ablation treatments are more suitable for highly irregular corneas 11 and therefore may represent the most appropriate option for post-CT eyes, only small limited series 4,8,11,[13][14][15] have been published, and it is not widely adopted.…”

Refractive surgery following corneal graft

“…The high volume of excimer laser systems and the short learning curve could explain this high popularity. One of the advantages of the excimer laser, in general, is the ability to treat the wide range of postkeratoplasty refractive errors, including the irregular ones [6,36,37]. Another unique advantage is the ability to remove visually significant subepithelial fibrosis and scarring 'phototherapeutic keratectomy (PTK)' [38].…”

“…Laser-assisted subepithelial keratectomy (LASEK), as an advanced surface ablation, has been also used in the past few years in an attempt to decrease the haze [6,41]. Customized topography-guided or wavefrontguided surface ablation has been tried for better refractive outcomes [35,37,[42][43][44].…”