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Discussion by David R. Hardten, MD
Ophthalmology Volume 107, Number 1, January 2000 Discussion by David R. Hardten, MD Dr. Maldonado and co-authors describe an exciting new use of OCT in this article. One of the major issues with LASIK is understanding why certain patients are undercorrected or overcorrected after LASIK and precisely measuring the thickness of the corneal flap. The information presented in their article will set the foundation for further studies addressing these issues. The thickness of the corneal flap produced with the microkeratome appears to vary from patient to patient and may depend on a variety of factors. These factors are still not well understood because we have not had a good way of measuring the flap thickness. Pachymetry before and after the flap is cut can give some idea of the flap thickness but is not precise.1 This information is important, because if the flap is thicker, then there is a greater risk of ablating near the endothelium and leaving inadequate tissue posteriorly to prevent corneal ectasia. Several factors probably determine flap thickness. Of course, the distance between the microkeratome block and the blade is one factor. The intensity of the suction and intraocular pressure also probably play some role.
From Minnesota Eye Consultants, 710 East 24th Street, Suite 106, Minneapolis, MN 55404.
The central and peripheral corneal curvatures and corneal diameter may also be important. Corneal thickness may also be related to flap thickness. These factors can now be studied more intensely with this new measurement technique. Regression of refractive effect can be seen after LASIK, but the cause of this regression is not totally understood.2 With OCT, the thickness of the cornea posterior to the flap can be measured to help distinguish between epithelial hyperplasia and stromal remodeling as causing the refractive regression. This well-designed study confirms the usefulness of OCT as a technique to study patients undergoing refractive surgical procedures. This new tool will help to further our goal of providing safe, accurate surgical correction of refractive errors for our patients. References 1. Casebeer JC, Slade SG, Dybbs A, Mahanti RI. Intraoperative pachometry during automated lamellar keratoplasty: a preliminary report. Refract Corneal Surg 1994;10:41–3. 2. Lindstrom RL, Hardten DR, Chu YR. Laser in situ keratomileusis (LASIK) for the treatment of low, moderate, and high myopia. Trans Am Ophthalmol Soc 1997;95:285–96.
Historical Image Color prints on paper, ca 1840 artist L. Boilly
These delightful prints make fun at characterizing the use of various vision aids. * Courtesy of the Museum of Ophthalmology, Foundation of the American Academy of Ophthalmology, San Francisco, California.
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From Minnesota Eye Consultants, 710 East 24th Street, Suite 106, Minneapolis, MN 55404.
The central and peripheral corneal curvatures and corneal diameter may also be important. Corneal thickness may also be related to flap thickness. These factors can now be studied more intensely with this new measurement technique. Regression of refractive effect can be seen after LASIK, but the cause of this regression is not totally understood.2 With OCT, the thickness of the cornea posterior to the flap can be measured to help distinguish between epithelial hyperplasia and stromal remodeling as causing the refractive regression. This well-designed study confirms the usefulness of OCT as a technique to study patients undergoing refractive surgical procedures. This new tool will help to further our goal of providing safe, accurate surgical correction of refractive errors for our patients. References 1. Casebeer JC, Slade SG, Dybbs A, Mahanti RI. Intraoperative pachometry during automated lamellar keratoplasty: a preliminary report. Refract Corneal Surg 1994;10:41–3. 2. Lindstrom RL, Hardten DR, Chu YR. Laser in situ keratomileusis (LASIK) for the treatment of low, moderate, and high myopia. Trans Am Ophthalmol Soc 1997;95:285–96.
Historical Image Color prints on paper, ca 1840 artist L. Boilly
These delightful prints make fun at characterizing the use of various vision aids. * Courtesy of the Museum of Ophthalmology, Foundation of the American Academy of Ophthalmology, San Francisco, California.
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