Commentary: Prophylactic laser barrage before laser-assisted in-situ keratomileusis.

Abstract

The debate on prophylactic laser barrage, especially before refractive surgery, continues to divide retina specialists. There are surgeons who believe that every predisposing lesion must be treated, while some are sceptical about the preventive role of laser to the retinal lesions. Rhegmatogenous retinal detachment (RD) is common in myopes in eyes with lattice degeneration and posterior vitreous detachment (PVD).[1] Low myopes (−1.00 to −3.00 D) have a fourfold increased risk of RD over emmetropic patients. This risk increases significantly when the patient’s refractive error exceeds −3.00 D.[2] Lattice degeneration is present in 6–8% of the population and increases the risk of retinal detachment. Myopes, in addition to having peripheral retinal degenerations and lattice, have PVD at a younger age compared to emmetropes. The procedure of laser-assisted in-situ keratomileusis (LASIK) increases the risk of RD due to sudden fluctuation in the intraocular pressure (IOP) during the procedure. The increase in IOP that occurs during suction prior to engaging the microkeratome, and rapid lowering of IOP when the suction ring is decompressed, or the shock wave generated by the excimer laser may lead to PVD resulting in retinal tears.[3] Hence, LASIK patients should undergo an extensive retinal evaluation with prophylactic photocoagulation of lattice degeneration, atrophic holes, and/or flap tears in an attempt to reduce any risk of an RD. The prophylactic treatment of high-risk lesions is believed to prevent RD. Ruiz-Moreno et al. retrospectively studied 1554 consecutive eyes (878 patients) undergoing LASIK and reported a low incidence (0.25%) of RD in their patients after prophylactic barrage laser to lesions predisposing to RD.[4] Several other studies have reported a higher incidence of RD in patients who had undergone prior LASIK than would be predicted from myopia alone.[5] Till date, there have been no prospective studies directly comparing prophylactic treatment versus nontreatment and showing any definite RD risk reduction for asymptomatic retinal lesions in general. In a recent study by Srinivasan et al., of the 694 eyes that had undergone LASIK, 5 eyes (0.7%) developed RD over 7 years.[6] Increased risk of RD was not associated with age at LASIK surgery, gender, laterality and spherical equivalent. While RD was statistically significantly higher in eyes which had prior prophylactic laser photocoagulation, the number of eyes who developed RD was so low that it could not be clinically meaningful, with very wide confidence intervals of the hazard ratio. Only three eyes had lattice degeneration prior to LASIK which were lasered, and one eye with lattice was unlasered. Ideally, a study should compare a substantial number of eyes which had lattice degeneration prior to LASIK and assign them to prophylactic laser or no laser. Hence, it cannot be conclusively proven from this study that prophylactic laser adversely increases the risk of RD after LASIK. Proliferation of the epiretinal membrane (ERM) or macular pucker has been occasionally observed following treatment for a retinal break. However, a direct cause-and-effect relationship of treatment of a retinal break to ERM remains unclear. After laser photocoagulation of the retinal lesions, the adhesive force between the retina and choroid increases over a few days to 2 weeks. Hence, refractive surgery is recommended after at least 7 days following laser photocoagulation. Patients at high risk should also be educated about the symptoms of PVD and retinal detachment as well as about the value of periodic follow-up examinations. Patients should be counselled that the refractive surgery does not reduce the risk of RD, even though the refractive error may be cured after LASIK. In conclusion, all patients should have a thorough dilated indirect ophthalmoscopy with scleral depression prior to refractive surgery. Treatment of any retinal lesion predisposing to the development of RD is mandatory.