Making Sense of Refractive Surgery in 2001: Why, When, for Whom, and by Whom?

Department of Ophthalmology, University of California Davis, Sacramento, USA.
Mayo Clinic Proceedings (Impact Factor: 6.26). 09/2001; 76(8):823-9. DOI: 10.1016/S0025-6196(11)63227-8
Source: PubMed


Surgical alteration of the focusing or refractive properties of the eye has been performed on millions of patients. An array of procedures to correct myopia, hyperopia, astigmatism, and presbyopia have been introduced over the past 25 years with varying degrees of success. Improved technology has increased patient and physician satisfaction and enthusiasm. Currently available surgical procedures can be categorized as incisional, surface-altering, lamellar, and intraocular. The choice of procedure depends on individual patient indications and contraindications based on results of ocular examinations, eg, corneal pachymetry to measure corneal thickness, keratometry to measure the corneal curvature, basal tear secretory rate, and dark-adapted pupil size. The postoperative uncorrected visual acuity depends, in large part, on the quality of the preoperative evaluation and refraction. Before scheduling a patient for surgery, the ophthalmologist must ensure that the patient understands the potential risks of the procedure and has realistic expectations for the postoperative level and quality of uncorrected visual acuity. Postoperative complications include corneal flap displacement, undercorrection and overcorrection, and epithelial ingrowth under the corneal flap and inflammatory keratitis. Postoperative dry eye, infection, and inflammation are usually treated medically. Ongoing technological innovations to customize the surgical approach to an individual patient's eye continue to improve outcomes.

Full-text preview

Available from:
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To identify differentially expressed genes in healing mouse corneas by using cDNA microarrays. Transepithelial excimer laser ablations were performed on mouse corneas, and the wounds were allowed to heal partially in vivo for 18 to 22 hours. Total RNA was isolated from both normal and healing corneas and was used for synthesis of cDNA probes. 33P-labeled exponential cDNA probes were hybridized to mouse cDNA nylon arrays. Of the 1176 genes on the nylon arrays, the expression of 37 was upregulated and that of 27 was downregulated more than fivefold in the healing corneas compared with the normal, uninjured corneas. Interleukin (IL)-1beta, laminin-5, and thrombospondin-1, which have been shown to be upregulated in healing corneas, were all found to be induced in the corneas in response to excimer laser treatment. Many genes were identified for the first time to be differentially regulated during corneal wound healing. Among the upregulated genes were intercellular adhesion molecule (ICAM)-1, macrophage inflammatory proteins, suppressors of cytokine signaling proteins (SOCS), IL-10 receptor, and galectin-7. Among the downregulated genes were connexin-31, a gap junction protein; ZO1 and occludin, tight junction proteins; and Smad2, a key component in the TGFbeta signaling pathway. Microarray data were validated on a limited number of genes by semiquantitative RT-PCR and Western blot analyses. Gene array technology was used to identify for the first time many genes that are differentially regulated during corneal wound healing. These differentially expressed genes have not previously been investigated in the context of wound healing and represent novel factors for further study of the mechanism of wound healing.
    Investigative Ophthalmology &amp Visual Science 10/2002; 43(9):2897-904. · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To compare flap thickness and reproducibility of four different types of microkeratomes during LASIK. Retrospective, nonrandomized, comparative case series. Four hundred ninety consecutive eyes underwent LASIK and were evaluated by measuring the central flap thickness by subtractive pachymetry. All flaps were created using the Bausch & Lomb (Miami, FL) Hansatome 180 head, the Alcon (Fort Worth, TX) Summit Krumeich Barraquer Microkeratome 160 head, the Moria (Antony, France) Carriazo Barraquer (CB) 130 head, or the Moria M2 110 head. The flap thickness measurements differed according to the microkeratome used and were 131+/-28 microm in 41 eyes (8.4%) with the Bausch & Lomb Hansatome 180 head, 162+/-21 microm in 127 eyes (25.9%) with the Alcon Summit Krumeich Barraquer Microkeratome (SKBM) 160 head, 157+/-40 microm in 65 eyes (13.3%) with the Moria CB 130 head, and 134+/-23 microm in 257 eyes (52.4%) with the Moria M2 110 head. The central flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with the Moria CB (P< 0.0005). There is no correlation between flap thickness reproducibility and age, corneal thickness, or corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender (P<0.02). Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2 microkeratomes, which both use a second motor for advancement. The greatest variability, noted with the Moria CB, was likely due to the manual translation feature and places further importance on the safety of the second motor and automation when performing LASIK.
    Ophthalmology 10/2003; 110(10):1931-4. DOI:10.1016/S0161-6420(03)00786-3 · 6.14 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Radio-frequency thermokeratoplasty (RF-TKP) is a technique used to reshape the cornea curvature by means of thermal lesions using radio-frequency currents. This curvature change allows refractive disorders such as hyperopia to be corrected. A new electrode with ring geometry is proposed for RF-TKP. It was designed to create a single thermal lesion with a full-circle shape. Finite element models were developed, and the temperature distributions in the cornea were analysed for different ring electrode characteristics. The computer results indicated that the maximum temperature in the cornea was located in the vicinity of the ring electrode outer perimeter, and that the lesions had a semi-torus shape. The results also indicated that the electrode thickness, electrode radius and electrode thermal conductivity had a significant influence on the temperature distributions. In addition, in vitro experiments were performed on rabbit eyes. At 5 W power, the lesions were fully circular. Some lesions showed non-uniform characteristics along their circular path. Lesion depth depended on heating duration (60% of corneal thickness for 20 s, and 30% for 10 s). The results suggest that the critical shrinkage temperature (55-63 degrees C) was reached at the central stroma and along the entire circular path in all the cases.
    Medical & Biological Engineering & Computing 12/2003; 41(6):630-9. DOI:10.1007/BF02349970 · 1.73 Impact Factor
Show more