Myopia Laser Treatment
Why does it matter? The prevalence of Myopia or nearsightedness is estimated to be about 20% of the population in the US [1]. With myopia, the eyeball is too long, or the cornea is too steep. About 80% of the myopia cases can be corrected with a diopter reduction of 6 (average of ~3.5) or less. Myopia can be corrected through corrective lenses, such as glasses and contact lenses. It can also be corrected by LASIK, but this does have a number of risks and side effects [2]. Also, in cases where the cornea is not thick enough (keratoconus, for eg.), LASIK is not a viable option. Treatments using heat to shrink collagen and achieve corneal shape change has been performed using lasers and radio frequency probes in the past [3,4]. However, it required damaging the corneal tissue and the results shows to be transient in many cases. Thermal treatments using lasers potentially involve no contact, is attractive in terms of recovery time, patient comfort and procedure time.
What is our solution? Refractive power correction is obtained by reshaping the cornea, of which the major constituent is collagen (after water). The primary goal of our laser thermal procedures is to heat the collagen, which will cause the collagen structure to shrink and ultimately change the shape of the cornea. Current techniques target the water absorption to provide the necessary temperature increase to achieve the same result. As a result, the water is heated first and the heat is transferred to the collagen to cause the required reshaping effects. However, this often results in We hypothesize that by using wavelengths at ~1720 nm that target the collagen directly [5], we should be able to get the required collagen shrinkage and corneal reshaping with lower power and less or no collateral damage to the surrounding tissue. We have performed preliminary in vitro experiments using our ~1710 nm laser to reshape bovine and porcine eyes. The histological analysis performed showed that the cornea can be reshaped and flattened without any apparent damage, as indicated by the absence of hazy or whitish region in the cornea post laser treatment. The video below shows in vitro bovine corneal reshaping using the ~1710 nm laser.
[1] Susan Vitale, Leon Ellwein, Mary Frances Cotch, Frederick L. Ferris III, Robert Sperduto, “Prevalence of Refractive Error in the United States, 1999-2004” Archives of Ophthalmology, Vol. 126, No. 8, pp 1111-1119 (2008); Anne D. Walling, “Shortsightedness: a review of causes and interventions,” American Family Physician, September 15, 2002.
[2] S.A Melki, D. T. Azar, “LASIK Complications: Etiology, Management, and Prevention”,Survey Opthalmol Vol. 46, pp 95-116, (2001)
[3] Douglas D. Koch, Adrian Abarca, Rogelio Villarreal, Richard Menefee, Thomas Kohnen, Arthur Vassiliadis, Michael Berry, “Hyperopia Correction by Noncontact Holium: YAG Laser Thermal Keratoplasty Clinical Study with Two-year Follow-up” Ophthalmology, Vol. 103, Number 5, pp 731-740 (1996)
[4] Penny A. Asbell, Robert K. Maloney, Jonathan Davidorf, Peter Hersh, Marguerite McDonald, Edward Manche, the Conductive Keratoplasty Study Group, “ Conductive Keratoplasty for the correction of hyperopia”, Tr. Am. Ophth. Soc., Vol. 99, pp 79-87 (2001)
[5] Urbas, A.A. and R.A. Lodder, “Near-Infrared Spectromery in Cardiovascular Disease,” Chapter 34, pp. 657-670, Handbook of Near-Infrared Analysis, 3rd ed. Edited by D.A. Burns and E.W. Ciurczak, CRC Press (2008).