2020–2021 BCSC Basic and Clinical Science Course™
13 Refractive Surgery
Chapter 5: Photoablation: Techniques and Outcomes
Outcomes for Hyperopia
In myopic ablations, the central cornea is flattened, whereas in hyperopic ablations, more tissue is removed from the midperiphery than from the central cornea, resulting in an effective steepening (see Fig 5-1B). To ensure that the size of the central hyperopic treatment zone is adequate, a large ablation area is required for hyperopic treatments. Most studies have employed hyperopic treatment zones with transition zones out to 9.0–9.5 mm. FDA clinical trials of PRK and LASIK for hyperopia up to +6.00 D reported that 46%–59% of eyes had postoperative UCVA of 20/20 or better, 92%–96% had UCVA of 20/40 or better, and 84%–91% were within 1.00 D of emmetropia; loss of more than 2 lines of BCVA occurred in 1%–3.5%. The VISX FDA clinical trial of hyperopic astigmatic PRK up to +6.00 D sphere and +4.00 D cylinder reported an approximate postoperative UCVA of 20/20 or better in 50% of eyes, UCVA of 20/40 or better in 97%, and 87% within ±1.00 D of emmetropia, with loss of more than 2 lines of BCVA in 1.5%. For the same amount of correction, the period from surgery to postoperative stabilization is longer for hyperopic than for myopic corrections. Overall, studies with larger ablation zones have demonstrated good results for refractive errors up to +4.00 D for conventional treatments, but predictability and stability are markedly reduced with LASIK treatments for hyperopia above this level. Consequently, most refractive surgeons do not treat up to the highest levels of hyperopia that have been approved by the FDA for conventional treatments.
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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.