Rapid visual recovery after low energy, thin flap femtosecond LASIK1

BackgroundOne of the distinctive features of modern thin-flap LASIK is the speed with which patients recover their vision fol-lowing surgery. The refractive literature has established that excellent visual outcomes by 1 month and even 1 week following LASIK have become the rule rather than the exception, a fact that stands in contrast to the imme-diate postoperative results of refractive techniques such as surface ablation. Although refractive surgeons are accustomed to seeing patients reach uncorrected distance visual acuity (UDVA) of 20/20 or better on postoperative day 1, the speed with which this visual recovery takes place during the first postoperative hours has not been established. The purpose of this study is to quantify the speed of visual recovery and document important func-tional milestones, such as when a patient feels comfort-able driving or text messaging after thin flap LASIK per-formed by the low energy FEMTO LDV.

MethodsThis single center, prospective pilot study evaluated patients who underwent bilateral simultaneous LASIK. Twenty eyes from 10 study patients underwent the same pre-op complete ocular examination to include UDVA; CDVA including manifest and cycloplegic refractions; meso-pic pupillometry; corneal anterior segment OCT; and mon-ocular mesopic contrast sensitivity. Inclusion criteria con-sisted of -1.00 to -7.00 diopters (D) of spherical equivalent myopia, with up to 3.00 D of refractive astigmatism; a stable refraction; CDVA of at least 20/20 in each eye; and a residual LASIK bed thickness of ≥250 μm in each eye. The FEMTO LDV Crystal Line laser was used to create a superior hinge flap with a hinge length of 3.7 mm and hinge width of 0.4 mm. All flaps were 9.0-mm diameter, round, and with intended flap thickness of 110 μm in depth. Energy levels were standardized for the planar cut. Post-op exam-inations were performed immediately at the conclusion of surgery and at 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 1 day, and 1 month post-op. The target for all sur-geries was emmetropia. Statistical analysis was performed using the two-sample for means paired t test P values <0.05 were considered significant.

ResultsSnellen visual acuity: For monocular UDVA, 100% of eyes were 20/40 at 1 hr and 20/25 at 4 hrs. Ninety-five percent of eyes were 20/20 at 1 d. For binocular UDVA, 100% of patients achieved 20/32 by 30 min, 20/20 by 4 hrs, and 20/16 by 1 d. At 1 mo, 100% of patients achieved binoc-ular UDVA of 20/16 or better; 60% of these patients were 20/12.5 or better. No eye lost ≥2 lines of CDVA.Contrast sensitivity: Low frequency contrast sensitivity returned to pre-op baseline by 1 hr (P=.73), and showed a statistically significant improvement over baseline by 4 hrs (P=.01). High frequency contrast sensitivity decreased post-op (P<.01) but returned to pre-op baseline by 4 hrs (P=.48). One month post-op contrast sensitivity data were significantly improved over the pre-op values at all spatial frequencies.

DiscussionExcellent monocular and binocular visual acuities were obtained within hours of myopic thin-flap LASIK with the FEMTO LDV. One-hundred percent of patients had binoc-ular UDVA of 20/32 or better within 30 min of surgery. By 2 hrs, 100% of patients had binocular UDVA of 20/40 or better with 50% of these patients reporting that they would be comfortable driving. At 4 hrs, all patients were legal to drive and felt comfortable driving. Studies suggest that the speed of visual recovery following LASIK is related to the smoothness of the optical interface cleaved by the femtosecond laser during the flap-making process. Using the FEMTO LDV, we found patients had functional visual acuity enabling them to carry out common tasks within hours of receiving LASIK.

References:

1 Durrie DS, Brinton JP, Avila MR, Stahl ED. Evaluating the speed of visual recovery following thin-flap LASIK with a femtosecond laser. J Refract Surg. 2012 Sep. 28 (9):620-4.

Clinical study

FEMTO LDV LASIK

Ziemer Ophthalmic Systems AG, CH-2562 Port, Switzerland | www.femtoldv.com | clinicals@ziemergroup.com The

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Percentage of patients comfortable driving or texting after LASIK

Time period Driving Text messaging % of patients % of patientsImmediate 12.5 87.515 min 12.5 87.530 min 12.5 1001 hr 25 1002 hr 50 1004 r 100 1001 d 100 100