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Evidence supports the long-term safety, efficacy, and stability of foldable iris-fixated phakic intraocular lenses (pIOLs) after a 6-year follow-up, according to study results published in Journal of Cataract and Refractive Surgery.1
Investigators evaluated the visual and refractive results of these devices, as well as structural complications — especially endothelium cell density loss after implantation — for the correction of moderate to high myopia.1
In cases of myopia cases greater than -8.00 D, patients are unlikely to find the results they’re looking for with refractive surgery and, as a result, surgeons offer patients phakic intraocular lens (pIOL) implants.2-4 Historically, pIOLs that are implanted into the posterior chamber have been associated with cataract formation.1 Angle-supported pIOLs have also been associated with complications.1 These can include severe chronic endothelial cell loss and a high incidence of corneal decompensation (leading to the necessity of corneal keratoplasty).1,5,6 These complications were common enough to warrant the withdrawal of all previous angle-supported pIOLs from clinical application.1,5,6
A third option, iris-fixated pIOLs, have shown satisfactory results for patients with myopia and astigmatism — especially since the development of foldable models helped resolve any issues of surgical incision size.1,7
The researchers in this case reviewed records of 177 eyes of 98 patients with a mean age of 32.33 (± 7.13 years), who had iris-fixated pIOLs implanted between January 2010 and December 2013.1 Follow-up evaluations were performed 6 months after surgery, and every 12 months for 6 years.1 Investigators gathered preoperative and follow-up data on uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA), manifest refraction, endothelial cell density (ECD), and anterior chamber depth (ACD).1
They noted significant improvement in CDVA from 0.09 (± 0.02) logMAR preoperatively to 0.04 (± 0.02) logMAR (P <.0001) at 6 years postoperatively.1 Patients spherical equivalent also demonstrated a significant improvement from -9.50 (± 2.93) D to -0.41 (± 0.45) D at 6 years. A year after surgery, 70% of eyes that received the iris-fixated pIOL implant had equal or better UDVA than preoperative CDVA.1
Regarding complications of ECD loss, a mean loss of 31.77 cells/mm2 (1.19%) was observed each year until the sixth year.1 The overall mean ECD loss after correction for the physiologic loss was 3.02% after 6 years.1 No correlations were observed between the mean ECD loss and the preoperative ACD.1
Mean preoperative ACD was higher in this study than the value usually reported (3.26 ± 0.24 mm).1 In this study, 54.80% of patients had a preoperative value of 3.20 mm or higher, and 88.71% had a preoperative ACD of 3.00 mm or higher, measured from the corneal endothelium.1 The mean ACD significantly decreased (P <.001) after 1 year to 3.15 (± 0.27) mm and remained stable until year 5.1 Between the 5-year and 6-year follow-up visits, the researchers identified another significant decrease in ACD (P <.001) to 3.01 (± 0.27) mm.1 The mean ACD reduction was 7.68% at the end of the 6 years.1
Additionally, researchers noted pigment deposits in 10.87% of eyes. Previous research on the iris-fixated pIOLs showed pigment deposits ranging from 10.2% to 14.8% of eyes.1
This research is unique in that only a few studies investigate the outcomes of foldable iris-fixated pIOL results greater than 2 years.1
The researchers advised that “the preoperative value of ACD used as an inclusion criterion should always be measured to the corneal endothelium, which better describes the real anterior chamber anatomy.” The added that “a minimum ACD value of 3.00 mm (to the endothelium) appears to be a safer indication for the iris-fixated [pIOLs].”1
References
1. Monteiro T, Correia F, Franqueira N, Mendes J, Pinto C, Vaz F. Long-term efficacy and safety results after iris-fixated foldable phakic intraocular lens for myopia and astigmatism: 6-year follow-up. J Cataract Refract Surg. Published online September 7, 2020. doi:10.1097/j.jcrs.0000000000000419
2. Ikeda T, Shimizu K, Igarashi A, Kasahara S, Kamiya K. Twelve-year follow-up of laser in situ keratomileusis for moderate to high myopia. Biomed Res Int.
2017;2017:9391436. doi: 10.1155/2017/9391436.
3. Reinstein D, Carp G, Archer T, Lewis, T, Gobbe M, Moore J, Moore T. Long-term visual and refractive outcomes after lasik for high myopia and astigmatism from -8.00 to -14.25 D. J Refractive Surg. 2016;32(5):290-297. doi: 10.3928/1081597X-20160310-01.
4. Santhiago MR, Smadja D, Gomes BF, et al. Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative
topography. Am J Ophthalmol. 2014;158(1):87-95 e81. doi: 10.1016/j.ajo.2014.04.002.
5. Kohnen T, LaFontaine L, Andrew R, et al. Long-term safety follow-up of an anterior chamber angle-supported phakic intraocular lens. J Cataract Refract Surg. 2017;43(9):1163-1170. doi: 10.1016/j.jcrs.2017.06.035.
6. Pechmeja J, Guinguet J, Colin J, Binder P. Severe endothelial cell loss with anterior chamber phakic intraocular lenses. Journal of cataract and refractive surgery. J Cataract Refract Surg. 2012;38(7):1288-1292. doi: 10.1016/j.jcrs.2012.04.022.
7. Lee J, Lee H, Kang D, Choi J, Kim E, Kim T. Comparison of toric foldable iris-fixated phakic intraocular lens implantation and limbal relaxing incisions for moderate-to-high myopic astigmatism. Yonsei Med J. 2016 Nov 1; 57(6): 1475–1481. doi: 10.3349/ymj.2016.57.6.1475
