New Study Shows No Effect of LASIK Flap Hinge Position on Dry Eye Outcomes. In my last blog, we looked at the fact that the LASIK flap diameter does not influence the development of dry eye after LASIK. This blog looks at the LASIK flap hinge and whether its position affects dry eye after LASIK laser vision correction.
The flap we use in LASIK surgery has a hinge, allowing it to be folded back before the excimer laser is applied and then returned into position after the laser sculpting is completed. Surgeons have debated where the best position is for the LASIK flap’s hinge. Some surgeons have advocated using a superior flap, located at the top. Other surgeons instead have advocated putting the hinge nasally, meaning on the side of the cornea toward the nose. Much of the debate has been over whether one hinge position produces more or less dry eye after LASIK than the other.
A very recent study in the September 2012 issue of the Journal of Refractive Surgery appears to settle this debate: it shows that hinge position simply does not affect dry eye occurance after LASIK. Surgeons at the Chang Guang Memorial Hospital in Taiwan looked at results in 43 patients who had LASIK in both eyes for correction of nearsightedness. In each patient, one eye had a superior hinge and the other eye had a nasal hinge. This method of study is called a “contralateral eye study.” Contralateral eye studies are considered particularly accurate since individual patient characteristics are controlled for in that both eyes are in the same patient.
The authors of the study examined both corneal sensation after surgery, as well as markers for dry eye. Corneal esthesiometry, Schirmer basic tear secretion testing (BST), tear break-up time (TBUT), and ocular surface staining were measured. The Ocular Surface Disease Index (OSDI) was administered as well.
No significant differences were noted in any of these parameters or tests between eyes with a superior hinge and a nasal hinge, leading the authors to conclude that hinge position did not affect corneal sensation or dry eye parameters after LASIK.
Personally, although I have performed thousands of cases with each type of hinge position, I generally prefer a superior hinge position as the downward force of blinking serves to smooth the flap. With a nasal hinge, the downward force of blinking, at least theoretically, could apply forces perpendicular to the hinge position. Additionally, my personal clinical experience concurs with this study: the location of the hinge does not seem to affect dry eye outcomes.
See Also
Effect of Hinge Position on Corneal Sensation and Dry Eye Parameters after LASIK
Study looks at the effect on hinge position on corneal sensation and dry eye after LASIK.
Chang Guang Memorial Hospital, Taiwan
Website for the Chang GUang Memorial Hospital in Taiwan, the center that carried out the study on temporal versus nasal LASIK flap hinge position.
The Effect of Hinge Position on Corneal Sensation and Dry Eye After LASIK
Another study looking at the effect of LASIK flap hinge position on corneal sensation and dry eye after LASIK.
Effect of Hinge Location on Corneal Sensation and Dry Eye After Laser In Situ Keratomileusis for Myopia
A study examining the effect of LASIK flap hinge position on dry eye and corneal sensation after LASIK laser vision correction eye surgery.
The Incidence and Risk Factors for Developing Dry Eye After Myopic LASIK
A review of the risk factors for the development of dry eye syndrome after LASIK laser eye surgery for correction of nearsightedness.
Effect of Hinge Position on Corneal Sensation and Dry Eye after Laser In Situ Keratomileusis (LASIK) using a Femtosecond Laser
The role of LASIK flap hinge position on corneal sensation after LASIK is examined.
Dry Eyes and Corneal Sensation after Laser In Situ Keratomileusis with Femtosecond Laser Flap Creation: Effect of Hinge Position, Hinge Angle, and Flap Thickness
Dry eye and corneal sensation are examined after LASIK using a femtosecond laser (Intralase) to make the LASIK flap.
The Effect of Hinge Position and Depth Plate on the Rate of Corneal Sensation Following LASIK
The effect of hinge position on corneal sensation after LASIK using a mechanical microkeratome to make the LASIK flap.
Corneal Reinnervation After LASIK: Prospective 3-Year Longitudinal Study
A scientific study of the regeneration of superficial corneal nerves after LASIK flap creation over a three year period.
Effect of Laser In Situ Keratomileusis on Tear Stability
The effect of LASIK on tear stability and dry eye.
Schirmer Test and Break-Up Time of Tear Film in Normal Subjects
The role of using Schirmer testing to determine dry eye, which has application for dry eye testing before LASIK (pre-operative testing) and after LASIK (post-operative testing).