A new study conducted in Brazil has found that wavefront-guided wavefront-guided LASIK for the correction of moderate myopia.
Eighty-eight eyes of 44 patients with moderate myopia were randomly selected to undergo either wavefront-guided (custom) PRK or custom LASIK. The mean amount of pre-operative myopia was -3.85 diopters (D) among the PRK eyes and -3.99 D among the LASIK eyes.
For eyes undergoing custom PRK, a 0.002 percent solution of MMC was applied to the exposed corneal tissue for a period of one minute immediately following the excimer laser treatment.
Mitomycin C is a chemical agent frequently used during PRK surgery to decrease the risk of clouding of the cornea during the healing process. This loss of transparency is commonly referred to as corneal haze.
Post-operative corneal haze is potential side effect of PRK surgery that can decrease vision. Though mitomycin C has been proven effective in reducing corneal haze after PRK eye surgery, overexposure to the agent can be toxic to the cornea.
At one year after surgery, the mean uncorrected visual acuity (UCVA) of eyes in both groups was better than 20/20, but more custom PRK eyes (52 percent) than custom LASIK eyes (31 percent) achieved UCVA of 20/12.5 or better.
Evaluation of best spectacle-corrected visual acuity (BSCVA) after surgery revealed more eyes in the PRK group (74 percent) than in the LASIK group (43 percent) gained one or more lines of BSCVA on a standard eye chart, compared with BSCVA of the same eyes prior to surgery.
Eyes in the PRK group also demonstrated better contrast sensitivity under moderate and bright light than eyes in the LASIK group.
When surveyed a year after surgery, more patients in the PRK group (74 percent) than in the LASIK group (64 percent) reported having “excellent vision” as a result of their vision correction procedure.
No eye in the custom PRK group demonstrated clinically significant corneal haze at the end of the study.
The researchers concluded that in this study, wavefront-guided PRK with application of 0.002 percent MMC was more effective than wavefront-guided LASIK for the correction of moderate myopia when evaluated one year after surgery.
They cautioned, however, that further research is necessary to determine the optimal mitomycin C concentration and exposure time, and to evaluate possible long-term corneal side effects of MMC exposure, before 0.002 percent MMC is widely adopted for use in PRK eye surgery.
SOURCE: One-year outcomes of a bilateral randomized prospective clinical trial comparing PRK with mitomycin C and LASIK. British Journal of Ophthalmology. December 2009.