The Dry Eye Zone

Rebecca's Blog

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Abstract: Lasik study (cough, choke)

If you didn't notice the date of this study or the word 'wavefront', you might be forgiven for having assumed it came straight out of the Dark Ages of LASIK in the 90s when the only thing anybody (well, any ophthalmologist) knew or cared much about was UCVA and BCVA after surgery.

I know the profession has made considerable progress since then in recognizing the significance of things like vision quality and ocular surface pain. So what gives here?

I don't know whether to laugh, cry or bust someone's chops (I'm inclining to the latter, I'm afraid) when I read in a study of this scope a dry eye rate of 0.18%. I recalculated it to make sure the decimal was in the right place.

You are seriously claiming to have seen no more dry eye in your patients than DLK?

You have got to be kidding me.

How'd you measure dry eye? ("Quick, stick a Schirmer strip in there while the anaesthetic drop is still sloshing around.")

The real explanation of course is in the abstract: "Complications were tabulated using all available data." In a study stating a dry eye rate far lower than almost any recent research would put it by almost any measure of dry eye symptoms and/or signs, I can only conclude that dry eye data was unavailable for the majority of these patients because no one bothered to gather it.

One-month outcomes of wavefront-guided LASIK for low to moderate myopia with the VISX STAR S4 laser in 32,569 eyes.
Schallhorn SC, Venter JA.

J Refract Surg. 2009 Jul;25(7 Suppl):S634-41.

PURPOSE: To determine the safety and efficacy of wavefront-guided LASIK for the correction of low to moderate myopia, as performed by surgeons employed by Optical Express, a large corporate provider.

METHODS: Data were extracted from the Optical Express central database on 22,900 patients (42,143 eyes) who underwent primary LASIK to treat low to moderate myopia and/or astigmatism. All treatments used a wavefront-guided ablation profile and had a refractive target of emmetropia. Outcomes were evaluated using 1-month follow-up data, which were available for 32,569 eyes of 17,713 patients (77% follow-up). Complications were tabulated using all available data.

RESULTS: The mean manifest spherical equivalent (MSE) was reduced from -2.97 +/- 1.33 diopters (D) (range: -0.37 to -6.00 D) to -0.03 +/- 0.29 D (range: -3.50 to +4.50 D) 1 month after surgery. Ninety-four percent of eyes were within 0.50 D of the intended correction, and the correlation coefficient of the attempted versus achieved MSE was 0.96. Uncorrected visual acuity (UCVA) of 20/20 or better was achieved in 92% of eyes; 99% of eyes achieved UCVA of 20/40 or better. Among patients who had bilateral laser vision correction, 98% achieved 20/20 uncorrected binocular vision. Average best spectacle-corrected visual acuity (BSCVA) improved slightly 1 month after surgery (mean change: +0.01 logMAR). There were 210 (0.67%) eyes that lost 2 or more lines of BSCVA; however, all eyes were 20/40 or better. Intraoperative complications occurred in 25 eyes (0.06%; 1:1686), and postoperative complications occurred in 210 eyes (0.64%; 1:155). The most common complications were dry eye (n=58; 0.18%; 1:562) and mild diffuse lamellar keratitis (grade 1 or 2) (n=58; 0.18%; 1:562).

CONCLUSIONS: Wavefront-guided LASIK can safely and effectively correct low to moderate myopia, as demonstrated by 1-month postoperative visual outcomes from a large number of patients.
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