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Hyperopic corneal refractive surgery was first published by Dausch et al1 in 1993. The U.S. Food and Drug Administration approved laser in situ keratomileusis (LASIK) for hyperopia in 2000.2 However, the predictability and stability of earlier attempts were compromised once the corrected refraction exceeded +3.00 diopters (D).3,4 There have been significant improvements in LASIK for high hyperopia using a larger optical zone and transition zone, updates to the ablation profile design, and the introduction of flying-spot lasers. However, as expected, the refractive stability still decreases for higher corrections along with a reduction in corrected distance visual acuity.5–7 The use of epithelial thickness monitoring has been shown to improve the safety of high hyperopic LASIK.6
By the early 1980s, refractive lamellar keratoplasty was being investigated as a tissue additive procedure to alter corneal refractive power to correct high hyperopic aphakia,8–10 following the descriptions by Barraquer and Rutllán11 of epikeratophakia, in which the lenticule is placed on top of the cornea after epithelium removal. Currently, femtosecond laser technology can accurately create a refractive lenticule. The refractive lenticule extracted from myopic small incision lenticule extraction (SMILE) can be used to correct a refractive error-matched hyperopic correction in a recipient patient according to Barraquer's law of thicknesses.12 Several surgical techniques of refractive lenticular implantation have been developed. Thus, a second method of correcting hyperopia by an additive procedure is endokeratophakia, in which the lenticule is implanted into an intrastromal pocket.13 A third method is femtosecond laser–assisted lenticule intrastromal keratoplasty (LIKE), in which the lenticule is implanted under a corneal LASIK flap.
In 2013, Pradhan et al13 described the endokeratophakia procedure to correct high hyperopia of an aphakic amblyopic eye with +10.50 D. The postoperative refraction at 1 year only reached 50% of the intended correction. Other studies also found there was an undercorrection for high hyperopic treatments using this method.14 The posterior corneal changes were thought to be an important factor for causing the undercorrection, which was also predicted by finite element modeling.15 In a subsequent study, it was postulated that the retention of Bowman's membrane contributed to the posterior cornea changing shape more than the anterior cornea, as originally described by Arffa.16
This phenomenon may be lessened or avoided with epikeratophakia or LIKE as Bowman's layer is severed....