Singapore study assesses success trajectory of LASIK for myopia
The success of laser-assisted in situ keratomileusis (LASIK) for myopia has been improving over the years, according to an 18-year, single-centre study from Singapore.
“Our study shows a consistent, progressive improvement in the efficacy of LASIK for myopia over time,” said the researchers.
This prospective study involved 27,312 patients (median age 31.6 years, 35.5 percent male, 87.4 percent Chinese) who had undergone myopic LASIK (53,731 eyes) between 1998 and 2015 at the Singapore National Eye Centre. Post-procedure examinations included uncorrected Snellen visual acuity (UCVA), best-corrected Snellen visual acuity (BCVA), and slit-lamp biomicroscopy, and were carried out at 1 day, 1 week, 1 month, and 3 months post-procedure. Patients were followed up for a mean 78 days.
The percentage of flaps created using the femtosecond laser increased from 30 percent in 2008 to 86 and 100 percent in 2009 and 2011, respectively.
The overall rate of UCVA ≥20/40 and ≥20/20 was 97.3 and 68.7 percent, respectively, with UCVA ≥20/40 increasing from 98.6 to >99 percent between 2006 and 2010 onwards, while UCVA ≥20/20 increased from 67.9 to >78.1 percent of eyes in the same time frame. In 2015, UCVA ≥20/40 and ≥20/20 was achieved in 99.7 and 80.1 percent of eyes, respectively. [Br J Ophthalmol 2018;doi:10.1136/bjophthalmol-2018-312587]
The procedure appeared to be most efficacious among patients with low myopia (spherical equivalent < -5.0 D), with 99.2 and 79.6 percent achieving UCVA of ≥20/40 and ≥20/20, respectively.
About 95 percent of eyes did not experience postoperative vision loss, while 4.2 and 0.40 percent experienced loss of one and ≥2 lines of BCVA, respectively. The safety index exceeded 1.05 from 2010.
About 90 and 65 percent of eyes achieved ±1.0 and ±0.5 D target refraction, respectively, with refractive predictability increasing from 92.5 to 97.6 percent between 2009 and 2015 for ±1.0 D post-procedure target refraction.
The retreatment rate was low at 2.55 percent and has been <1.2 percent since 2010, with 98.4 percent of eyes achieving ≥20/40 and 63.5 percent achieving ≥20/20 UCVA following retreatment.
According to the researchers, increase in experience among surgeons, ablation nomograms that prevent undercorrection, and improvement in excimer laser systems could be among the reasons for the low retreatment rate.
The overall complication rate was also low at 0.98 percent, with an annual complication rate of <0.8 percent from 2010 onwards. Most complications were flap-related, accounting for 78.6 and 66.9 percent of intra- and postoperative complications, respectively. Except for an increase in complication rate in 2007 due to a surge in diffuse lamellar keratitis cases, complication rate reduced over the study period.
There were 12 cases of ectasia that occurred before 2007, all of which occurred among patients who underwent LASIK with mechanical microkeratome.
The researchers acknowledged that incidences of late-onset keratectasia may have been missed in this study, and also alluded to several other limitations including the short follow-up period and the lack of assessment of post-LASIK dry eye.
“[W]e found that the outcomes of LASIK have continued to improve over the 18-year period with higher efficacy, refractive predictability, and safety outcomes while maintaining a low rate of retreatment and complications and thus is a safe and effective modality which is anticipated to remain as a mainstay of laser refractive surgery,” they concluded.