For patients with high myopia (between -6.00 D and -10.00 D) flexible iris-fixated phakic intraocular lenses (pIOLs) may have superior long-term visual results to small-incision lenticule extraction (SMILE), according to newly published research from the Journal of Cataract and Refractive Surgery.1 While the pIOLs were associated with more statistically significant endothelial cell loss than SMILE surgery, no pIOLs were explanted over the course of this 6-year study.1 

The investigators reviewed 47 eyes of 32 patients that underwent the SMILE procedure and 52 eyes of 29 patients who had an iris-fixated pIOL implanted, all of which had high myopia.1 Mean postoperative follow-up was 63.75 (± 18.40) months in the SMILE group and 65.38 (± 16.22) months in the pIOL group (P =.71).1 At 6 years after surgery, refractive predictability was slightly better in the pIOL group, and the percentages of eyes within 0.50 D of the attempted correction was 83%.1 That percentage in the SMILE group was 77%.1 Mean uncorrected distance visual acuity (UCDVA) was 0.09 (± 0.05) LogMAR for the pIOL group.1 The eyes that underwent SMILE had a UCDVA of 0.12 (± 0.06) LogMAR. The pIOL group also had significantly higher safety and efficacy indices.1 

The pIOL group did, however, experience an average of 11.09% endothelial cell loss at 6 years after implantation, whereas the SMILE group showed no statistically significant ECL from preoperative baseline 6 years after the procedure.1 The average corneal endothelial cell count was 2712 (± 272) mm²/cell preoperatively to 2411 (± 281) mm²/cell 6 years postoperatively. None of the patients’ eyes lost 2 or more lines of corrected distance visual acuity, but 1 eye in the SMILE group did lose 1 line.1

The researchers point out that, for highly myopic patients, prior research shows a significant increase in corneal high-order aberrations after SMILE.1 Increased spherical aberrations will negatively affect visual quality and contrast sensitivity in mesopic conditions. Specifically, evaluation of the 5 mm zone of high-myopic patients in a 2015 study shows a significant increase in corneal HOA postoperatively.2 However, a 2016 research shows that the amount of aberration decreases over time — which researchers attributed to corneal restructuring following the procedure.3


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While high myopia patients may see successful outcomes, the researchers point out that the implantation of pIOL itself “is relatively difficult, and it can cause iris and corneal endothelium damage both pre- and post-operatively.”1

References

1. Yildirim Y, Cakmak S, Sucu M, et al. Comparative study of small-incision lenticule extraction and phakic intraocular lens implantation for the correction of high myopia: six-year results. J Cataract Refract Surg. Published online September 7, 2020. doi: 10.1097/j.jcrs.0000000000000418

2. Pedersen IB, Ivarsen A, Hjortdal J. Three-year results of small incision lenticule extraction for high myopia: refractive outcomes and aberrations. J Refract Surg. 2015;31:719–724. doi: 10.3928/1081597X-20150923-11.

3. Yıldırım Y, Alagöz C, Demir A, et al. Long-term results of small-incision lenticule extraction in high myopia. Turk J Ophthalmol. 2016;46(5):200–204. doi: 10.4274/tjo.22605.