51
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Rowsey JJ, Waring GO, Monlux RD, Balyeat HD, Stevens SX, Culbertson W, Barron B, Nelson D, Asbell P, Smith R, Arentsen J, Cowden J, Lynn MJ. Corneal Topography as a Predictor of Refractive Change in the Prospective Evaluation of Radial Keratotomy (PERK) Study. Ophthalmic Surg Lasers Imaging Retina 1991. [DOI: 10.3928/1542-8877-19910701-04] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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52
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53
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Waring GO, Lynn MJ, Strahlman ER, Kutner MH, Culbertson W, Laibson PR, Linstrom RD, McDonald MB, Myers WD, Obstbaum SA. Stability of refraction during four years after radial keratotomy in the prospective evaluation of radial keratotomy study. Am J Ophthalmol 1991; 111:133-44. [PMID: 1801760 DOI: 10.1016/s0002-9394(14)72250-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Prospective Evaluation of Radial Keratotomy Study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refraction between -2.00 and -8.00 diopters. We studied the stability of the refractive error during four years after surgery for each of 341 eyes first operated on that had a single surgical procedure. Between baseline and two weeks after surgery, all eyes became less myopic; between two weeks and three months, 161 eyes (59%) lost 1.00 D or more of the initial effect; and between three and six months, 266 eyes (95%) had a stable refraction with less than 1.00 D change. The change from six months to four years was less than 1.00 D for 246 eyes (72%). There was 1.00 D or more decrease in surgical effect (increased minus power) for 13 eyes (4%), and 1.00 D or more increase in surgical effect (decreased minus power) for 82 eyes (24%). Eyes with larger amounts of preoperative myopia and smaller diameter of the clear zone were more likely to have an increasing effect of the surgery. The duration of this continued increasing effect of the surgery is unknown.
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Affiliation(s)
- G O Waring
- Department of Ophthalmology, Emory Eye Center, Atlanta, GA 30322
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54
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Lindquist TD, Williams PA, Lindstrom RL. Surgical Treatment of Overcorrection Following Radial Keratotomy: Evaluation of Clinical Effectiveness. Ophthalmic Surg Lasers Imaging Retina 1991. [DOI: 10.3928/1542-8877-19910101-05] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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55
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Abstract
Recent advances in topographic analysis have provided powerful tools for detecting subtle, but clinically significant, alterations of corneal contour. This article compares keratometry, keratoscopy, and computer-assisted topographic analysis and provides specific examples of the sensitivity of computer-assisted systems in revealing topographic alterations that were not previously discernable. Quantitative descriptors of corneal topography such as the surface asymmetry index, the surface regularity index, and simulated keratometry value augment the information provided by color-coded topographic maps.
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Affiliation(s)
- S E Wilson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas
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56
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57
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58
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59
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Bloom HR, Sands J, Schneider D. Corneal Rupture From Blunt Trauma 22 Months After Radial Keratotomy. J Refract Surg 1990. [DOI: 10.3928/1081-597x-19900501-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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60
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Pallikaris IG, Papatzanaki ME, Stathi EZ, Frenschock O, Georgiadis A. Laser in situ keratomileusis. Lasers Surg Med 1990; 10:463-8. [PMID: 2233101 DOI: 10.1002/lsm.1900100511] [Citation(s) in RCA: 345] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A new laser refractive procedure is being developed in a rabbit model. With a modified microkeratome, central corneal flaps were created. An ArF excimer laser was used to produce 3-mm-diameter circular ablations on the central part of the exposed stromal bed. One group of animals was sacrificed immediately postoperatively, and both the dissected and ablated areas were studied using scanning electron microscopy. A second group of animals was sacrificed 4 weeks postoperatively. In this group, the subsequent healing of the corneas was studied using light microscopy. At 3 days, the wounded stromal areas showed some degree of haze. Haze was progressively reduced over 1 month, but it could be still discerned biomicroscopically. A hemicircular opacification corresponding to the flap edges was also apparent on slit-lamp examination. Microscopic observation showed that the epithelium was normal, except at the flap margins, where it was thickened. An increased number of keratocytes was observed in the interface between the flap stroma and the ablated area. The procedure might induce stable corneal changes because of the preservation of the anterior layers of the cornea.
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Affiliation(s)
- I G Pallikaris
- Department of Ophthalmology, School of Health Sciences, University of Crete, Greece
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61
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Koch DD, Liu JF, Hyde LL, Rock RL, Emery JM. Refractive complications of cataract surgery after radial keratotomy. Am J Ophthalmol 1989; 108:676-82. [PMID: 2596547 DOI: 10.1016/0002-9394(89)90860-x] [Citation(s) in RCA: 134] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Four patients underwent cataract extraction with posterior chamber lens implantation several years after radial keratotomy. All four patients experienced an initial hyperopic shift caused by an early postoperative corneal flattening of greater than or equal to 1 diopter. This flattening partially regressed, leaving the patients with a mean of 0.42 diopter of persistent corneal flattening. We found the Binkhorst and the Holladay intraocular lens calculation formulas to be more accurate than the SRK II for these patients. Corneal curvature measured with the keratometer was less accurate for intraocular lens calculations than was a value derived by subtracting the refractive change induced by the radial keratotomy from the patients' keratometric measurements obtained before radial keratotomy.
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Affiliation(s)
- D D Koch
- Cullen Eye Institute, Baylor College of Medicine, Houston, Texas
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62
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Harris DJ, Waring GO, Burk LL. Keratography as a guide to selective suture removal for the reduction of astigmatism after penetrating keratoplasty. Ophthalmology 1989; 96:1597-607. [PMID: 2616145 DOI: 10.1016/s0161-6420(89)32679-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
After penetrating keratoplasty in 52 eyes, keratography refraction and keratometry were used to select appropriate interrupted sutures for removal in order to reduce astigmatism. All eyes had one continuous and either 12 or 16 interrupted nylon sutures. The keratographs were examined retrospectively and separated into six groups on the basis of similar mire patterns. The removal of single sutures associated with three of these patterns reduced astigmatism by the following average amounts: symmetrical oval pattern, 0.44 diopters (D); D-shaped oval pattern, 2.07 D; and focal indentation pattern, 6.60 D. The other three patterns--mildly disrupted mires, incomplete mires, and uninterpretable mires--did not allow quantification of results. Examples of these keratographic patterns are presented and recommendations are made for their use in the management of astigmatism following penetrating keratoplasty.
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Affiliation(s)
- D J Harris
- Department of Ophthalmology, Emory University School of Medicine, Atlanta
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63
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Abstract
Monocular diplopia secondary to radial keratotomy was investigated in a 42-year-old ophthalmologist. Under certain conditions, the patient observed a ghost image, loss of contrast, and variability in the subjective refraction. The objective findings were scissoring of the retinoscopic reflex, a prominent iron line, and localized flattening of the cornea.
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64
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Abstract
Radial keratotomy for myopia and transverse keratotomy for astigmatism are the most commonly performed refractive surgical procedures. A decade of experience with modern techniques has produced considerable literature on the complications of keratotomy. Vision-threatening complications (bacterial keratitis, traumatic rupture of the globe through weakened keratotomy scars, endophthalmitis, cataract formation from surgical trauma to the lens) are quite rare, occurring in less than 1% of eyes in published series. The most common side effects affect most patients in the first few months after surgery: pain for 24 to 48 hours, transient glare and light sensitivity, and fluctuating visual acuity. The most common persistent complications are overcorrection and undercorrection. Persistent irregular astigmatism occurs in almost all cases in the region of the incision scars, but it is rarely severe enough to reduce spectacle acuity. Most individuals have mild glare, but this is rarely disabling. Diurnal variation of refraction in visual acuity occurs commonly, but the magnitude of the fluctuation is seldom enough to require multiple pairs of spectacles. Longterm refractive stability occurs in approximately half of eyes by six months, but approximately one in four eyes will experience continued change over six months to four years. Complications, such as scarring from intersecting keratotomy incisions, irregular astigmatism resulting from multiple reoperations, and overcorrections with the attendant early onset of symptomatic presbyopia are becoming much less frequent.
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Affiliation(s)
- E R Rashid
- Department of Ophthalmology, Wilford Hall Medical Center, San Antonio, Texas
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65
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Hachicha A, Simon S, Samson J, Hanna K. The use of gray-level information and fitting techniques for precise measurement of corneal curvature and thickness. ACTA ACUST UNITED AC 1989. [DOI: 10.1016/s0734-189x(89)80004-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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66
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Bauerberg J, Sterzovsky M, Brodsky M. Radial Keratotomy in Myopia of 6 to 12 Diopters Using Full-Length Deepening Incisions. J Refract Surg 1989. [DOI: 10.3928/1081-597x-19890501-08] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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68
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Lynn MJ, Waring GO, Nizam A, Kutner MH, Culbertson W, McDonald MB, Meyers WD, Naidoff MA, Nelson JD, Obstbaum SA, Rowsey JJ, Salz JJ. Symmetry of Refractive and Visual Acuity Outcome in the Prospective Evaluation of Radial Keratotomy (PERK) Study. J Refract Surg 1989. [DOI: 10.3928/1081-597x-19890301-04] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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69
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Abstract
Eleven eyes of six patients, who had been referred for management of irregular astigmatism after receiving crossed incisions for myopic astigmatism, had moderate to marked irregular corneal astigmatism with marked flattening in the meridians of intersecting incisions. All six patients had a decrease in best-corrected visual acuity with spectacles after surgery. Visual acuity with spectacles was 20/40 in five of 11 eyes; with contact lenses it reached 20/40 in ten of 11 eyes. However, two patients could not wear the contact lenses because of lens decentration caused by the marked distortion in corneal topography. Even with contact lenses, visual acuity could only be improved to 20/25 or better in six of 11 eyes.
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Affiliation(s)
- P J McDonnell
- Doheny Eye Institute, University of Southern California, School of Medicine, Los Angeles
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70
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71
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Abstract
A high resolution photokeratoscope using digital video image acquisition and computer graphics was used to describe anterior corneal topography before and after radial keratotomy. After radial keratotomy, the entire cornea is flattened, but this effect is more pronounced centrally. The flat central "optical zone" varies in size, shape, and location. Regional variations in corneal power may explain phenomena observed after radial keratotomy, such as visual acuity that is better than would be expected on the basis of refractive error, and the occurrence of ghost images.
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72
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McDonnell PJ, Garbus J, Lopez PF. Topographic analysis and visual acuity after radial keratotomy. Am J Ophthalmol 1988; 106:692-5. [PMID: 3195648 DOI: 10.1016/0002-9394(88)90702-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Using a computerized corneal topographic mapping system that allows detailed examination of the corneal curvature in the vicinity of the visual axis, we identified separate regions of differing corneal curvature in three of 11 eyes after radial keratotomy. In these eyes, the excellent uncorrected visual acuity appeared to be inconsistent with the postoperative spherical equivalent as determined by refraction and corneal curvature by standard keratometer measurements. The distinct regions of corneal curvature appeared to serve as alternative effective optical zones, thus allowing the patients to have excellent visual acuity. In essence, the cornea became a multifocal lens. Although degradation in the contrast of the image as well as monocular diplopia are possible, our patients had no significant complaints.
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73
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Hanna KD, Jouve F, Bercovier MH, Waring GO. Computer Simulation of Lamellar Keratectomy and Laser Myopic Keratomileusis. J Refract Surg 1988. [DOI: 10.3928/1081-597x-19881101-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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74
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75
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Santos VR, Waring GO, Lynn MJ, Schanzlin DJ, Cantillo N, Espinal ME, Garbus J, Justin N, Roszka-Duggan V. Morning-to-evening change in refraction, corneal curvature, and visual acuity 2 to 4 years after radial keratotomy in the PERK Study. Ophthalmology 1988; 95:1487-93. [PMID: 3211457 DOI: 10.1016/s0161-6420(88)32981-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The authors previously reported morning-to-evening changes in ophthalmic measurements at 3 months and at 1-year after radial keratotomy in a self-selected group of patients in the Prospective Evaluation of Radial Keratotomy (PERK) study. Fifty-two patients included in the earlier study were examined again between 2 1/2 and 4 years after surgery before 10:00 AM and after 5:30 PM on the same day to determine if the changes persisted beyond 1 year after surgery. Between the morning and evening examinations, 31% of the eyes had an increase in minus spherical equivalent power of the manifest refraction of 0.50 to 1.50 diopters; 12% had a change in cylinder power of 0.50 to 1.00 D; 19% had a decrease in uncorrected visual acuity of two to five Snellen lines; and 29% showed central corneal steepening by 0.50 to 1.00 D. Thus, in some patients, morning-to-evening fluctuation persisted until 2 1/2 to 4 years after radial keratotomy.
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Affiliation(s)
- V R Santos
- PERK Coordinating Centers, Emory University, Atlanta, GA
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76
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Abstract
A prospective study was set up to determine the effectiveness, predictability, stability, safety and feasibility within the National Health Service of radial keratotomy. The methods adopted include a new simplified guide to surgery with a predicted accuracy in 84 of 100 operations. Ninety-six percent of eyes with myopia of -6.0D or less preoperatively were seeing 6/12 or better six months after surgery. Refraction remained stable within a range 0.5D spherical equivalent between the first and sixth postoperative months in 96%, between the first and twelfth postoperative months in 90% and between the first and second years in 100% of eyes examined. There were no cases of progressive hypermetropia. Sixty-four percent of the 61 patients admitted to postoperative symptoms. Three percent of eyes lost best corrected vision. The disappointments were few but were analysed in detail. The least reliable were found to be associated with the higher myopes requiring a 3.0 mm clear optical zone.
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Affiliation(s)
- S P Percival
- Department of Ophthalmology, Scarborough Hospital, Yorkshire
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77
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78
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Stern GA. Update on the medical management of corneal and external eye diseases, corneal transplantation, and keratorefractive surgery. Ophthalmology 1988; 95:842-54. [PMID: 3062533 DOI: 10.1016/s0161-6420(88)33119-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- G A Stern
- Department of Ophthalmology, University of Florida College of Medicine, Gainesville 32610
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79
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Salz JJ, Salz MS. Results of Four- and Eight-Incision Radial Keratotomy for 6 to 11 Diopters of Myopia. J Refract Surg 1988. [DOI: 10.3928/1081-597x-19880301-05] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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80
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Halliday BL. Refractive surgery. BMJ : BRITISH MEDICAL JOURNAL 1988; 296:62. [PMID: 3122931 PMCID: PMC2544667 DOI: 10.1136/bmj.296.6614.62-b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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