Journal of refractive and corneal surgery最新文献

{"title":"A surgical technique for the treatment of central corneal perforations.","authors":"M P Vrabec,&nbsp;J J Jordan","doi":"","DOIUrl":"","url":null,"abstract":"<p><strong>Background: </strong>Generally, corneal perforations of 2 mm in diameter or greater are treated using graft material for tectonic support. A surgical technique for the primary repair of such perforations without the use of any additional tissue is presented.</p><p><strong>Methods: </strong>This procedure is demonstrated by a case report. The technique involves creation of an elliptical defect out of a circular one, thus allowing for primary closure, with the addition of glue. A definitive penetrating keratoplasty was subsequently performed with several important modifications described herein.</p><p><strong>Results: </strong>A water-tight closure was obtained with this technique for 1 month while the inflammation subsided. Preoperative visual acuity was light perception. One year postoperatively, it was count fingers at 8 feet with mild irregular astigmatism.</p><p><strong>Conclusion: </strong>This technique is useful for perforations which are central, larger than 2 mm in diameter, and when corneal or scleral material is not readily available for patch grafting.</p>","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3","pages":"365-7"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18530970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A surgical technique for the treatment of central corneal perforations.","authors":"M. Vrabec, J. Jordan","doi":"10.3928/1081-597X-19940501-11","DOIUrl":"https://doi.org/10.3928/1081-597X-19940501-11","url":null,"abstract":"BACKGROUND\u0000Generally, corneal perforations of 2 mm in diameter or greater are treated using graft material for tectonic support. A surgical technique for the primary repair of such perforations without the use of any additional tissue is presented.\u0000\u0000\u0000METHODS\u0000This procedure is demonstrated by a case report. The technique involves creation of an elliptical defect out of a circular one, thus allowing for primary closure, with the addition of glue. A definitive penetrating keratoplasty was subsequently performed with several important modifications described herein.\u0000\u0000\u0000RESULTS\u0000A water-tight closure was obtained with this technique for 1 month while the inflammation subsided. Preoperative visual acuity was light perception. One year postoperatively, it was count fingers at 8 feet with mild irregular astigmatism.\u0000\u0000\u0000CONCLUSION\u0000This technique is useful for perforations which are central, larger than 2 mm in diameter, and when corneal or scleral material is not readily available for patch grafting.","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3 1","pages":"365-7"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70145565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Refractive surgery goes mainstream: establishing radial keratotomy services at a suburban community hospital.","authors":"R. Epstein","doi":"10.3928/1081-597X-19940501-14","DOIUrl":"https://doi.org/10.3928/1081-597X-19940501-14","url":null,"abstract":"","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3 1","pages":"378"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70145613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Induction of astigmatism by straight transverse corneal incisions, 45 degrees long, at different clear zones in human cadaver eyes.","authors":"M A Sabates,&nbsp;K A Buzard,&nbsp;M H Friedlander,&nbsp;M B Cortinas","doi":"","DOIUrl":"","url":null,"abstract":"<p><strong>Background: </strong>Two of the major factors affecting the amount of astigmatism correction are the length of the transverse incision and its distance from the center of the cornea. Many nomograms used in clinical practice have been created by varying the length or clear zone diameter of the incisions. A simplification of this situation has been suggested by Thornton, who has theorized that straight transverse incisions, subtending 45 degrees of arc, have equal astigmatic corrective effect at different clear zones. Our study tested Thornton's theory in human donor eyes.</p><p><strong>Methods: </strong>Ten eyes were tested at four clear zones: 5.0, 6.0, 7.0, and 8.0 mm. Paired straight transverse incisions, subtending an arc of 45 degrees (2.1 to 3.3 mm long), were centered on the 90-degree meridian. Preoperative keratometric readings at the 180- and 90-degree meridians were compared to the postoperative readings; the difference was the total astigmatism induced. We also calculated the coupling ratio.</p><p><strong>Results: </strong>Student's t-tests comparing clear zones 6.0 and 7.0 mm revealed a statistical difference (p = .0085) in total astigmatic induction, greater for the 6.0-millimeter zone. The coupling ratio decreased as the clear zone diameter increased, presumably as a result of diminished flattening effect along the incised meridian. One-way analysis of variance indicated that the groups were different (p = .0001), and that the theory noted above was incorrect.</p><p><strong>Conclusions: </strong>The effect of transverse incisions subtending the same angular length, drops off dramatically with clear zones larger than 6.0 mm, contrary to the theory of Thornton. This effect may be due to reduction in coupling as the clear zone diameter increases, suggesting that the greatest efficacy is achieved for transverse incisions placed between 5.0- and 6.0-millimeter zones.</p>","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3","pages":"327-32"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18528290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of night vision disturbances.","authors":"G. J. Florakis, D. A. Jewelewicz, H. E. Michelsen, S. Trokel","doi":"10.3928/1081-597X-19940501-06","DOIUrl":"https://doi.org/10.3928/1081-597X-19940501-06","url":null,"abstract":"BACKGROUND\u0000Evaluation of night vision disturbances has relied on subjective responses. We designed a test to more objectively measure night vision disturbances.\u0000\u0000\u0000METHODS\u0000The test consisted of projecting a small circle onto a visual acuity screen. The patient is asked to draw exactly what he sees on an Amsler grid. We evaluated 118 eyes in photopic and scotopic conditions and under different conditions of refractive correction.\u0000\u0000\u0000RESULTS\u0000Image degradation increased in scotopic conditions for myopes (p = .0001), hyperopes (p = .005), and emmetropes (p = .01). Myopic refractive error correlated with size of glare response (p = .001). Astigmatism correlated with decentration of glare response (p = .0001). Decentration increased in scotopic compared to photopic conditions (p = .002).\u0000\u0000\u0000CONCLUSION\u0000Our test offers a simple, convenient way to evaluate night vision disturbances and may offer a means of assessing night vision disturbances in patients considering refractive surgery.","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3 1","pages":"333-8"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70145460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corneal ectasia as a complication of repeated keratotomy surgery.","authors":"K. Wellish, B. Glasgow, F. Beltran, R. Maloney","doi":"10.3928/1081-597X-19940501-10","DOIUrl":"https://doi.org/10.3928/1081-597X-19940501-10","url":null,"abstract":"BACKGROUND\u0000Staged keratotomy surgery, or \"enhancement surgery,\" may allow a more predictable outcome, but also subjects the patient to additional surgical risks.\u0000\u0000\u0000METHODS\u0000A 39-year-old man underwent astigmatic keratotomy for myopic astigmatism, followed by 12 enhancement procedures for residual astigmatism.\u0000\u0000\u0000RESULTS\u0000These procedures effectively resulted in a double hexagonal keratotomy. The patient's best spectacle-corrected acuity deteriorated to counting fingers. Clinically, a conically-shaped protrusion of the central cornea, Munson's sign, diffuse subepithelial scarring, and central corneal thinning were noted. Penetrating keratoplasty was performed. Histopathologic examination showed central thinning, epithelial edema, disruption of Bowman's layer, marked stromal scarring, and focal areas of endothelial attenuation--findings consistent with keratoconus.\u0000\u0000\u0000CONCLUSION\u0000This case illustrates that multiple keratotomy procedures may result in corneal ectasia in apparently normal eyes and suggests that hexagonal keratotomy may be more likely to cause iatrogenic keratoconus.","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3 1","pages":"360-4"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70145533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biomechanical behavior of the cornea and its response to radial keratotomy.","authors":"G Simon,&nbsp;Q Ren","doi":"","DOIUrl":"","url":null,"abstract":"<p><strong>Background: </strong>Radial keratotomy reduces myopia by flattening the central cornea, but the mechanism remains a matter of controversy. In this article, we studied the biomechanical behavior of the cornea and its response to radial keratotomy.</p><p><strong>Methods: </strong>A human cadaver eye model without corneal epithelium was used in this study. We studied the effects which varying intraocular pressure (IOP) and corneal hydration would have on the keratometric power of unoperated eyes and eyes following radial keratotomy. For nonoperated eyes, first, normal corneal hydration was maintained while the IOP was varied. Second, the IOP was maintained at a constant level of 20 mm Hg while the corneal hydration was changed. The effects of separately varying the IOP and corneal hydration of postoperative eyes following an eight-incision radial keratotomy were studied in a similar fashion.</p><p><strong>Results: </strong>In the nonoperated eye, a very high IOP was associated with a general reduction of corneal astigmatism without significantly affecting the overall keratometric spherical equivalent refraction. A steepening change of less than 0.50 diopters (D) was obtained in all eyes when dehydrating the cornea from 700 +/- 50 microns (centrally) and 830 +/- 70 microns (peripherally), to 495 +/- 25 microns (centrally) and 655 +/- 45 microns (peripherally). Following radial keratotomy, changes in IOP within the physiological range were found to have minimal influence (< 0.50 D) on the radial keratotomy keratometric power. However, after hydrating the cornea with balanced salt solution for 30 minutes, we obtained a mean flattening of 10.00 D. When dehydrating these corneas with topical hyperosmotic solution over a period of 3.5 hours, the flattening reversed to near preoperative values. The change in keratometric power resulting from radial keratotomy was significantly modulated by varying the hydration state of the deepithelialized cornea: the greater the hydration, the flatter the central cornea; therefore, the unpredictable surgical outcomes and diurnal fluctuations observed after radial keratotomy may be affected by applying topical hyperosmotic agents.</p><p><strong>Conclusions: </strong>We hypothesize that the corneal stroma is an inelastic, anisotropic, layered collagen structure that distributes tensile stress unequally throughout its thickness as a function of the amount of hydration. IOP, within physiological levels, did not have a significant effect on corneal flattening.</p>","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3","pages":"343-51; discussion 351-6"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18530969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of nitrogen flow on recovery of vision after excimer laser photorefractive keratectomy without nitrogen flow.","authors":"E. Maguen, A. Nesburn, T. Papaioannou, J. Salz, J. Macy, C. Warren","doi":"10.3928/1081-597X-19940501-04","DOIUrl":"https://doi.org/10.3928/1081-597X-19940501-04","url":null,"abstract":"BACKGROUND\u0000Excimer laser (VISX) photorefractive keratectomy was performed using nitrogen flowing through the ocular fixation ring. It was felt that eliminating nitrogen flow may provide faster early visual rehabilitation.\u0000\u0000\u0000METHODS\u0000Two groups of 50 consecutive eyes underwent photorefractive keratectomy with (N2 flow) and without (no N2 flow) nitrogen flow, and were evaluated at 1 month postoperatively.\u0000\u0000\u0000RESULTS\u0000There were more under- or overcorrections exceeding 1.00 diopter (D) in the N2 flow than in the no N2 flow groups. Eighteen eyes in the N2 flow and 11 in no N2 flow groups saw 20/50 or less, without correction. Fourteen eyes in the N2 flow and nine eyes in the no N2 flow groups lost two or more lines of best spectacle-corrected visual acuity. Four eyes in the N2 flow and none in the no N2 flow groups increased more than 1.00 D of astigmatism.\u0000\u0000\u0000CONCLUSION\u0000The elimination of nitrogen flow in photorefractive keratectomy performed with the VISX laser appears to improve visual results in the early postoperative period.","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 3 1","pages":"321-6"},"PeriodicalIF":0.0,"publicationDate":"1994-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70145878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corneal power correction factor for photorefractive keratectomy.","authors":"R B Mandell","doi":"","DOIUrl":"","url":null,"abstract":"<p><strong>Background: </strong>Studies of corneal power changes resulting from photorefractive keratectomy generally rely on keratometer or videokeratograph measurements. These instruments convert corneal radius of curvatures values to optical powers by means of the single refracting surface formula, which incorporates an index of refraction value of 1.3375. This index approximates that of the tears but not the 1.376 index of the corneal epithelium or stroma. A hypothetical optical model was used to determine the most appropriate index to be chosen with respect to corneal power calculations relative to photorefractive keratectomy.</p><p><strong>Methods: </strong>The contribution of each refractive element in the tear lens-corneal surface to the total power of the eye was calculated in order to identify which index of refraction was most appropriate for the corneal power calculation.</p><p><strong>Results: </strong>The outer tear surface has significant optical power but the tear layer as a whole has nearly zero power due to the offsetting negative power of the posterior test surface. There is no significant difference in the effective power of light leaving the corneal anterior surface when considered with or without the tear layer. Photorefractive keratectomy changes the epithelium and anterior surface of the corneal stroma, but does not affect the posterior stroma or other ocular media. Hence the refractive index for the corneal epithelium or stroma of 1.376 should be used in converting radius to optical power values. The error in assuming a corneal index of 1.3375 is a constant proportion equal to 11.4% of the corneal power reading.</p><p><strong>Conclusions: </strong>Photorefractive keratectomy presents a situation in which the actual corneal refractive index of 1.376 should be used for correct corneal radius to power conversions. This may be accomplished by changing the index value in the instrument algorithm for keratometry and videokeratography to 1.376 or by adding a correction factor of either 11.4% of the regular reading to its value or multiplying by the factor 1.114. In other applications of keratometry or videokeratography, the index 1.3375 may be more appropriate.</p>","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 2","pages":"125-8"},"PeriodicalIF":0.0,"publicationDate":"1994-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18525464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cytotoxicity of viscoelastics on cultured corneal epithelial cells measured by plasminogen activator release.","authors":"Thomas D. Lindquist, Michael Edenfield","doi":"10.3928/1081-597X-19940301-08","DOIUrl":"https://doi.org/10.3928/1081-597X-19940301-08","url":null,"abstract":"BACKGROUND\u0000Plasminogen activator has been shown to be released by epithelial cells following corneal injury. The demonstration of the release of plasminogen activator from cultured corneal epithelial cells has been used for developing a cytotoxicity test, the Corneal Epithelial Plasminogen Activator test, which compares changes in the level of plasminogen activator in tissue culture media following chemical exposure as an index of chemical injury.\u0000\u0000\u0000METHODS\u0000Cultured rabbit corneal epithelial cells were exposed to varying concentrations of several viscoelastics for 1 hour. Release of plasminogen activator into the tissue culture media following exposure to the viscoelastic agent was studied as an index of chemical injury.\u0000\u0000\u0000RESULTS\u0000The least cytotoxicity to cultured rabbit epithelium was associated with those viscoelastic agents containing methylcellulose. A 1-hour exposure to most concentrations of methylcellulose and chondroitin sulfate (Phacote) and methylcellulose (Occucoat) demonstrated release of greater amounts of plasminogen activator than was seen following a similar exposure to balanced salt solution, suggesting the greatest protective effect of these two viscoelastics. In contrast, sodium hyaluronate and chondroitin sulfate (Viscoat) showed decreased amounts of plasminogen activator release after a 1-hour exposure to cultured corneal epithelial cells demonstrating cytotoxicity. Polyacrylamide (Orcolon) and most diluted preparations of sodium hyaluronate (Healon and Healon Yellow) showed only mild reductions in the release of plasminogen activator, whereas undiluted sodium hyaluronate preparations were nearly as cytotoxic as Viscoat.\u0000\u0000\u0000CONCLUSIONS\u0000This study suggests that viscoelastic agents containing methylcellulose (Phacote and Occucoat) may be most protective of the corneal epithelium during ophthalmic surgery. The clinical success of several dilute viscoelastic solutions as tear substitutes was corroborated by the lack of cytotoxicity seen in this study. Viscoat and undiluted sodium hyaluronate preparations showed the greatest cytotoxicity to cultured rabbit corneal epithelium.","PeriodicalId":79348,"journal":{"name":"Journal of refractive and corneal surgery","volume":"10 2 1","pages":"95-102"},"PeriodicalIF":0.0,"publicationDate":"1994-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70144485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}