Refractive surgeons have reduced the need for retreatment in recent years—from 4.52% in 2005 to just 0.18% in 2012—but older patient age, higher degree of astigmatism, the presence of hyperopia, surgeon inexperience and colder operating room temperature increase the likelihood of an enhancement procedure. So says a retrospective review of 21,313 LASIK and PRK patients published online in Cornea.1

Though research comparing the safety and efficacy of laser in-situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) exists, data on the factors that dictate need for retreatment remain scarce.2,3

Researchers at Ben-Gurion University of the Negev and Care-Vision Laser Centers in Tel Aviv, Israel analyzed data from patients who had undergone either LASIK or PRK at the latter institution between January 2005 and December 2012. Patients were separated into one of two groups according to whether they had undergone additional refractive surgery after the initial procedure. A total of 41,504 eyes were evaluated. LASIK flap creation was performed with a Moria microkeratome. 

Data indicated that during the during the study period, 2.1% of eyes underwent a single retreatment, while 0.05% of eyes underwent two retreatments and a single eye underwent three retreatments. All retreated patients (compared with those who only underwent their initial refractive procedure) exhibited significantly older age, better initial best-corrected visual acuity (BCVA) and higher preoperative Kmax, sphere and degree of cylinder values. Curiously, both patients with better BCVA (>1.35 logMAR) and worse BCVA (<0.45 logMAR) demonstrated higher retreatment rates, possibly due patient misconceptions regarding what outcomes to expect, the researchers say. The correlation between retreatment and patient age may reflect “the use of conservative nomograms, which attempt to avoid overcorrection in older patients,” the researchers wrote.

Additionally, patients requiring retreatment are also more likely to have a preoperative clinical cylinder greater than 1D; hyperopia rather than myopia; a 6.5mm optical zone (rather than 7mm) treatment; have undergone PRK (rather than LASIK); and been treated in higher humidity, lower temperature operating rooms. These results, the researchers say, could occur because “current methods, including the nomograms applied, are less accurate when it comes to treating astigmatism, as opposed to sphere.”

The team also noted that while no significant differences in mean K power were detected in the patient population, those with greater than 46D exhibited higher retreatment rates. Patients treated with ablation depths less than 30μm and greater than 120μm, as well as those who were treated by less experienced surgeons, exhibited the same.  

1. Mimouni M, Vainer I, Shapira Y, et al. Factors predicting the need for retreatment after laser refractive surgery. Cornea. 2016. [epub ahead of print].
2. Shortt AJ, Allan BD, Evans JR. Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive kerectomy (PRK) for myopia. Cochrane Database Syst Rev. 2013;1:CD005135.
3. Settas G, Settas C, Minos E, et al. Photorefractive keratectomy (PRK) versus laser-assisted in situ keratomileusus (LASIK) for hyperopia correction. Cochrane Database Syst Rev. 2012;6CD007112.