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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined 20 patients for the effect of a 3-mm sutureless temporal clear corneal incision cataract operation on corneal topography, as recorded with the computer-assisted video-keratoscope TMS-1 (Computed Anatomy, Inc., New York, New York). Each topographic image was cut into 178 fields in eight concentric rings. The refractive values of these fields were stored in a database. The mean differences between the preoperative and one-month postoperative findings were calculated and transformed into color-coded maps as output for the statistical analysis. The patients operated on showed a mean flattening of 0.4 to 1.0 diopter in the temporal region. This was statistically significant by paired Wilcoxon signed-rank tests. There was no significant vertical steepening or nasal flattening, except in two isolated fields. For control purposes, we twice examined 20 age-matched volunteers who were not operated on. The paired Wilcoxon tests of this group did not show significant changes. When compared with Cravy's vector analysis, induced topographic change analysis is better at evaluating surgically induced corneal shape changes.
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PMID:Computerized statistical analysis of corneal topography for the evaluation of changes in corneal shape after surgery. 805 63

The application of the 193 nm excimer laser for keratorefractive surgery promises to deliver a higher degree of precision and predictability than traditional procedures such as radial keratotomy. The development and evaluation of keratorefractive surgery have benefited from the parallel advances made in the field of corneal topography analysis. We used the Computed Anatomy Topography Modeling System (TMS-1) to analyze a Louisiana State University (LSU) Eye Center series of patients who had photorefractive keratectomy for the treatment of myopia with the VISX Twenty/Twenty excimer laser system. The excimer ablations were characterized by a relatively uniform distribution of surface powers within the treated zone. In the few cases that exhibited marked refractive regression, corneal topography analysis showed correlative changes. With topographical analysis, centration of the ablations relative to the center of the pupil could be evaluated. Marked improvement in centration occurred in the patients of LSU Series IIB in which the procedure to locate the point on the cornea directly over the pupil's center during surgery was refined. Corneal topographical analysis provides objective measures of keratorefractive surgical results and is able to measure the precise tissue removal effect of excimer laser ablation without the uncertainties caused by measuring visual acuity alone. Our observations forecast the need for improved aids to center the laser ablations and for the development of a course of treatment to prevent post-ablation stromal remodeling.
J Cataract Refract Surg 1993
PMID:Corneal topography of excimer laser photorefractive keratectomy. 845 Apr 33

Cataract surgery is known to induce refractive and corneal astigmatism, but little is known regarding the specific corneal topographic alterations produced by this surgery. We evaluated the corneal topographic effects of extracapsular cataract extraction (ECCE) performed with an 8- to 11-mm posterior limbal incision closed with interrupted sutures and subsequent selective suture removal. Corneal topography was analyzed in 15 eyes with the TMS-1 videokeratoscope preoperatively, before selective suture removal 4-6 weeks after surgery, 2-5 weeks after selective removal of sutures, and at 5 1/2-8 months after surgery. The Surface Regularity Index was significantly increased before suture removal and after suture removal but returned to normal at the final examination. The Irregular Astigmatism Index remained significantly increased at all examinations after surgery. Corneal asymmetry (Surface Asymmetry Index) continued to be significantly increased compared with the preoperative examination after suture removal and at 6 months after surgery. The standard deviation of powers (SDP) was significantly elevated before and immediately after suture removal, but was not significantly different at 6 months. Mean corneal astigmatism remained significantly increased (0.80 +/- 0.11 preoperatively, 1.39 +/- 0.24 at maximum follow-up, p = 0.04). Significant changes in corneal topography occurred in each patient between suture removal and final examinations. A few patients developed against-the-rule astigmatism ranging from 0.6 to 2.2 diopters. ECCE significantly altered corneal tomography compared with the preoperative contour in all patients. In those patients in whom surgically induced nonspherical and noncylindrical distortions occur (radially asymmetrical power distribution, lack of central corneal smoothness), corneal topography may provide information that is useful for management.
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PMID:Prospective study of corneal topographic changes produced by extracapsular cataract surgery. 892 69

This report details the case of a 65-year-old man with advanced cataract in which there was a large discrepancy between the K-readings taken with a keratometer and those taken with a TMS-1 videokeratoscope. It was suspected the discrepancy was caused by the advanced cataract in the presence of a dilated pupil. Repeat videokeratoscopic readings were close to the standard keratoscopic readings. This finding indicates that corneal topography can be affected by reflections other than those from the corneal surface.
J Cataract Refract Surg 1996 Dec
PMID:Effect of cataract on corneal topography results. 927 83

Keratometry and videokeratography are the most important means of evaluating induced corneal changes after surgery and have comparable sensitivities in the paracentral region of the cornea. When cataract surgery is planned, corneal topography can be used preoperatively in the calculation of IOL power, particularly in difficult cases, such as in patients who have undergone corneal refractive surgery or penetrating keratoplasty. A study published in the past year suggests that the mean power in ring 3 of the Tomey TMS-1 videokeratoscope (Cambridge, MA) appears to give the most accurate estimate of corneal power for the calculation of IOL power after radial keratotomy. In the case of PRK, traditional methods of determining the corneal power can lead to great amounts of anisometropia. Further research is needed to develop more accurate methods of calculating IOL power after PRK. Videokeratography can also be used before cataract surgery in planning the location and size of the incision. In general, smaller temporal incisions result in less astigmatism than do larger superior incisions. Postoperatively, videokeratography can be used to detect tight sutures, torsion of the wound, internal wound gape, and irregular astigmatism, as well as to guide suture removal or in cases where best-corrected visual acuity is not adequate and there are no other obvious causes for poor vision to determine if corneal irregularities are present.
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PMID:Corneal topography in cataract surgery. 1016 69