Humidity may affect LASIK surgery

A period of high humidity before surgery to correct nearsightedness can boost the chance that a person will need a follow-up operation, a new study of the procedure shows. Humidity apparently makes the cornea swell temporarily. That may induce a surgeon to remove less of that tissue than is needed to fully correct an individual’s eyesight, researchers report in the April Journal of Cataract and Refractive Surgery.

In laser-assisted in situ keratomileusis (LASIK) surgery, a doctor peels back the outer layer of the cornea, the clear shield that covers the eye, and then uses laser pulses to vaporize portions of the inner cornea, or stroma, to reshape it before replacing the corneal flap.

During 2000, ophthalmologist Keith A. Walter of the Wake Forest University School of Medicine in Winston-Salem, N.C., recorded details of LASIK surgeries he performed on 191 nearsighted patients. About 20 percent of patients required a follow-up procedure mainly because Walter hadn’t removed enough stroma. Follow-up LASIK—also called touch-up surgery—took care of the discrepancy, Walter says.

He reports that the patients needing touch-ups were more likely than others to have had their initial surgery after 2 weeks of humid weather. The moisture presumably caused people’s stromas to swell and led Walter to remove less tissue than necessary.

Walter concludes that physicians should pay attention to humidity and adjust stroma removal during LASIK accordingly.