Post radial keratotomy RGP fitting--a case study

ArticleinContact Lens & Anterior Eye 20(3):87-90 · February 1997with 83 Reads
The procedure of radial keratotomy produces an abnormal corneal topography, with the central cornea being flatter than the periphery. As a result, fitting the post-radial keratotomy (RK) patient with rigid gas permeable (RGP) lenses can be an enormously difficult task. Unlike standard lens designs, the Ortho-K series of lenses, originally designed for use in orthokeratology, possess a back peripheral radius (BPR) which is steeper than the back optic zone radius (BOZR). It is proposed that these lenses may provide a more acceptable fit than conventional RGPs for the post-RK patient.

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  • Article
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    Purpose: To report the refractive correction in a case of hyperopia and astigmatism following radial keratotomy. Methods: A case report. Results: A 47-year-old woman, who had undergone refractive surgery for radial keratotomy in both eyes 22 years before the present study, presented to our clinic with blurred vision. Her best corrected visual acuity, with spectacle correction of +3.50 DS/-1.50 DCX130° in the right eye and +3.75 DS/-1.50 DCX80° in the left eye, was 0.2 logMAR and 0.3 logMAR, respectively. Her keratometric readings were 35.75 D/36.75 D at 74° and 35.25 D/36.25 D at 61°, respectively. Prompted by intolerance to glasses, the patient requested for contact lenses. First, we applied a rigid, gas-permeable contact lens. However, we noted poor fitting due to central corneal flattening. Subsequently, we applied a conventional plus spherical soft contact lens (PSSCL), which is thick in the center and can therefore correct hyperopia and low-grade astigmatism simultaneously. The conventional PSSCL showed slightly inferior decentration, with good movement, and the patient was satisfied with it. After ascertaining the patient's living habits, we decided that a daily disposable soft contact lens would most meet her needs. The final prescription was a daily disposable PSSCL; the patient was satisfied with her corrected visual acuity of 0.0 logMAR in the right eye and 0.0 logMAR in left eye. Her daily disposable PSSCL-corrected visual acuity was stable during the 10-month follow-up. Conclusion: For patients displaying hyperopia with astigmatism following radial keratotomy, the PSSCL may confer better corrected visual acuity and acceptability.
  • Article
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  • Article
    Radial keratotomy (RK) is a well-known procedure for reducing myopia. However, the complications associated with the procedure and the development of newer technologies, such as photorefractive keratectomy and laser-assisted in situ keratomileusis, has resulted in the technique of RK falling out of favor. A number of patients who received RK during the 1980s are now experiencing a shift in their prescription and are presenting to primary care practitioners for contact lens fitting. These patients pose a significant challenge to the contact lens practitioner, and novel methods frequently are required to fit corneas that exhibit such abnormal topography. This article reviews the potential problems associated with fitting patients who have received RK and describes a case in which a novel lens design was used to achieve a successful lens fit.
  • Article
    Patients who have received Radial Keratotomy (RK) often require custom rigid gas permeable (GP) contact lenses to correct residual refractive errors post surgery. This paper is a long-term extension of a case report originally published in 1988 describing the course of a post-RK patient fitted with ortho-K design GP lenses. Visual acuities (VA), corneal curvatures, and refractive errors were collected from both the patient's medical record and the original case report published in 1988. These data were then plotted on graphs to observe the long-term effects of RK and rigid contact lens wear. Although there was substantial fluctuation in refractive errors, VAs, and corneal curvatures shortly following RK, the patient's long-term results post-RK have remained relatively stable for the past decade. Although RK decreased our patient's myopia for about 6 diopters per eye, ortho-K appeared ineffective for our patient over the long term. It is important for practitioners to know the process involved in treating post-RK patients and to understand that large overall lens diameters, sometimes reverse geometry design, GP lenses with good edge lifts, often provide reasonable mechanical and physiological fits while optimizing visual outcomes for these patients.
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    In 12 rabbits radial keratotomy was performed on one eye with no treatment to the contralateral eye. Cellulose acetate butyrate contact lenses were fitted bilaterally for extended wear. The eyes were monitored weakly for three weeks with a standardized slit-lamp grading method. Corneal neovascularization occurred earlier and progressed further in eyes that had radial keratotomy than in the control eyes (P less than .0025). These results suggested that patients who require contact lenses after radial keratotomy may be at higher risk for complications such as corneal neovascularization.
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    To select an appropriate base curve to use in fitting a contact lens in 16 eyes of 10 patients following radial keratotomy, we used a videokeratoscope that generates a 32-ring image, covering the entire cornea, to measure the midperipheral corneal curvature. We then based contact-lens selection on the curvature 3.5 mm superior to the visual axis. Photographic documentation of fluorescein patterns and subjective reports of the patients indicated a successful fitting in all cases.
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    Since the number of patients undergoing radial keratotomy has increased, more have required contact lens fitting to correct residual ametropia. A number of practitioners suggest that the postoperative changes stabilize after 12 months, so contact lens fitting on the unusual resultant corneal topography can begin. This paper discusses corneal and refractive changes that are revealed even when correctly fitting lenses are worn 1-5 years postoperatively. These changes indicate that lens wear may influence corneal topography and refraction even several years after radial keratotomy.
  • Article
    Thirty-two eyes of 28 patients who underwent radial keratotomy had a hyperopic overcorrection after the surgical procedure. Anisometropia, with associated aniseikonia and depth perception problems were present in many of these patients. The patients were subsequently fit with contact lenses. Conventional methods of fitting contact lenses in these patients were unsuccessful. A trial lens technique is used with the initial lens having a base curve equal to the preoperative keratometry measurements and the power equal to the preoperative spherical equivalent. Superficial neovascularization developed within the radial incisions in 33% of the eyes fitted with soft contact lenses. Gas permeable contact lenses offered patients the best-corrected visual acuity as well as minimal complications. In addition, the anisometropia was minimized, and fluctuating vision was eliminated in cases in which it was a problem.
  • Article
    To determine the long-term effects and stability of refraction following a standardized technique of radial keratotomy for myopia in the nine-center Prospective Evaluation of Radial Keratotomy (PERK) Study 10 years after surgery. Radial keratotomy using eight centripetal incisions was performed to reduce myopia of -2.00 to -8.75 diopters in 1982 and 1983. A mean of 10 years later, patients underwent a standardized ophthalmic examination similar to previous study examinations. Of 427 patients (793 eyes that underwent radial keratotomy), 374 patients (88%) (693 eyes) returned for the 10-year examination. Of 675 eyes with refractive data, 38% had a refractive error within 0.50 D and 60% within 1.00 D. For 310 first-operated eyes, the mean refractive error was -0.36 D at 6 months and changed in a hyperopic direction to + 0.51 D at 10 years. The average rate of change was +0.21 D/y between 6 months and 2 years and +0.06 D/y between 2 and 10 years. Between 6 months and 10 years, the refractive error of 43% of eyes changed in the hyperopic direction by 1.00 D or more. The hyperopic shift was statistically associated with the diameter of the clear zone. Uncorrected visual acuity was 20/20 or better in 53% of 681 eyes and 20/40 or better in 85%. Loss of spectacle-corrected visual acuity of 2 lines or more on a Snellen chart occurred in 3% of all 793 eyes that underwent surgery. Among 310 patients with bilateral radial keratotomy, 70% reported not wearing spectacles or contact lenses for distance vision at 10 years. The PERK technique of radial keratotomy eliminated distance optical correction in 70% of patients, with a reasonable level of safety. A shift of the refractive error in the hyperopic direction continued during the entire 10 years after surgery.
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