The changing face of refractive surgery.
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Humans↗
SEARCH · PubMed Health
Results for “Refractive Surgical Procedures”
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In vivo confocal microscopy for evaluation of wound healing following corneal refractive surgery.
Understanding of corneal wound healing plays an important role, not only in management of corneal infections, but especially in refractive surgery. A better control of wound healing mechanisms might improve the results of such resculpturing techniques and help to avoid complications arising from these procedures. While studies have been focused in different aspects of corneal wound healing, our knowledge has increased greatly during the last years. Many problems associated with corneal healing also contribute to clinical pathology following corneal surgery. Understanding of such conditions has been augmented by the continuously developing corneal imaging techniques. We have used in vivo confocal microscopy (IVCM) for assessing corneas subjected to refractive surgery as well as corneas with common complications resulting from such procedures. IVCM has become a powerful tool for examining corneal cells, nerves, inflammations and infections. It allows information to be acquired repeatedly and at subbiomicroscopic levels that earlier had been obtainable only by invasive microscopic methods. Pre-examining corneas preoperatively by IVCM in order to reveal diseases or conditions in which elective refractive surgical procedures should not be undertaken or to select the ideal operation technique may help to avoid complications in the future. Measurement of the thickness of corneal sublayers or estimation of the thickness of a laser in situ keratomileusis flap or wound bed are other applications in which confocal microscopy may be valuable. In this article we attempt to describe the in vivo confocal findings of common refractive procedures and their complications, and discuss their biology in light of the existing knowledge on wound healing phenomena.
Animals↗
Cataract and refractive surgery: reflecting on journal impact factors and influence.
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Bibliometrics↗
[Scientific evaluation and quality assurance in refractive surgical interventions. Evaluation of the Datagraph med computer program].
BACKGROUND: During recent years refractive surgical procedures have been increasingly used to correct refractive errors. Exact saving and assessment of pre-, intra- and postoperative results for scientific evaluation are desired and are necessary for quality management. The purpose of this investigation was to evaluate the database program Datagraph med (version 2.5) which has been developed for data processing and assessment in refractive surgery. MATERIAL AND METHODS: Pre-, intra- and postoperative data of 169 eyes treated with different refractive surgical methods (laser in situ keratomileusis, photorefractive keratectomy, laser thermal keratoplasty, phacic IOL) were collected, entered in the database and then evaluated by the above-mentioned program (with a follow-up of up to 12 months). The exactness of the Datagraph results was compared by means of manual recalculation. RESULTS: Datagraph med was able to precisely process the patient data and save them in a database. Statistics and graphs presented by Datagraph were as data has been entered. Furthermore all standard graphs requested by the international consensus for evaluation of refractive surgical data (stability, predictability, efficacy, safety and complications) could be imaged. CONCLUSIONS: Datagraph med is a helpful and precisely functioning program for processing and evaluation of refractive surgical data. It can be used for both scientific studies and for quality control. A continuous development and improvement of the program as well as the addition of statistical functions will be necessary due to the on-going progress in refractive surgery.
Adult↗
PTTL method applied to UV radiation detection during refractive surgery using excimer laser.
The method of phototransferred thermoluminescence (PTTL), using CaSO(4):Dy pellets produced at IPEN as sensitive material, was used to detect the spread laser radiation inside the surgery room during refractive surgical procedures using ArF excimer lasers. The purpose of this work was to study the viability of performing the ultraviolet radiation (UVR) exposure detection of patients and the hospital's surgical staff during a refractive surgery. The CaSO(4):Dy pellets were positioned at different distances from the laser source inside the surgery room: patient's ( congruent with 0.15 m), surgeon's ( congruent with 0.5 m) and nurse's ( congruent with 1.0 m) foreheads, lateral ( congruent with 1.5 m) and back ( congruent with 4.0 m) walls. The measurements of PTTL were carried out at two different conditions: five surgeries, each one taking approximately 10 min, and during a period of 4 h (cumulative), when several operations were performed. The detectors positioned as far as 4.0 m from the UV laser source were sensitised, making the UVR detection feasible at large source-detector distances. The absorbed energy was detected in the range from 40 microJ to 30 mJ during a surgery. This result indicates that the method studied can be used to detect the spread UVR.
Body Burden↗
Refractive surgery and cornea: the never-ending spiral of technology.
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Cataract Extraction↗
Effects of topical vitamin E on keratocyte apoptosis after traditional photorefractive keratectomy.
PURPOSE: To evaluate the keratocyte apoptosis and effects of topical vitamin E on keratocyte apoptosis after photorefractive surgery. METHODS: Rabbits were divided into 7 groups, and all groups were compared with controls after epithelial scraping, epithelial scrape and photorefractive keratectomy (PRK) (traditional PRK), transepithelial PRK, production of a corneal flap with microkeratome and laser-assisted in situ keratomileusis (LASIK). The effects of topical Vitamin E treatment were investigated in the traditional PRK group. The terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay (to detect DNA fragmentation in situ) and light microscopy have been used to detect apoptosis in rabbit cornea. RESULTS: Transepithelial PRK induced minimal keratocyte apoptosis, less than in all other refractive surgical procedures. The greatest amount of keratocyte apoptosis was observed after traditional PRK (p = 0.001), therefore we tested the effects of topical vitamin E in this group. The number of apoptotic keratocytes significantly reduced after vitamin E therapy (p < 0.005). CONCLUSION: Keratocytes undergo apoptosis after refractive surgery in response to mechanical epithelial removal, preparing of corneal flap and excimer laser stromal photoablation. The topical application of vitamin E immediately after surgery can prevent keratocyte apoptosis, and this result suggests that free radicals may be partly responsible for keratocyte apoptosis after excimer laser keratectomy.
Administration, Topical↗
Is intraoperative topography predictive of postoperative topographical changes following refractive surgery?
PURPOSE: To evaluate the usefulness of measuring corneal topography intraoperatively by Intraoperative PAR Corneal Topography System (IOPAR CTS) to predict the postoperative topographical changes in patients undergoing refractive surgery. METHODS: Topographical measurements of 9 eyes of 9 patients were taken by IOPAR CTS: 6 immediately after Intrastromal Corneal Ring Segments (ICRS) placement surgery and 3 immediately after Photorefractive Keratectomy (PRK) surgery. The topographical images taken by IOPAR CTS were analyzed to determine the quality of the image produced and the correlation of the keratometric data from the central 3 mm of cornea with measurements taken from an autokeratometer (Auto-Km) and the EyeSys Corneal Analysis System (CAS) for the same eyes taken three months following the procedure. RESULTS: At the 3-month postoperative exam, the correlation coefficients for flat (K1), steep (K2), and average keratometry (AK) readings produced by the Auto-Km and the EyeSys CAS were quite high. However, the correlation coefficients for K1, K2, AK, As or steep meridian axis (Ax) readings taken intraoperatively by IOPAR CTS were quite low when compared to the readings taken by either the Auto-Km or EyeSys CAS three months postoperatively. CONCLUSION: We found IOPAR CTS, relatively difficult to perform in the operating room during refractive surgical procedures and not useful clinically in predicting the postoperative topographical changes induced by ICRS or PRK procedure. Further studies are required to establish the efficacy and reproducibility of the instrument.
Adult↗
Night vision disturbances after corneal refractive surgery.
A certain percentage of patients complain of "glare" at night after undergoing a refractive surgical procedure. When patients speak of glare they are, technically, describing a decrease in quality of vision secondary to glare disability, decreased contrast sensitivity, and image degradations, or more succinctly, "night vision disturbances." The definitions, differences, and methods of measurement of such vision disturbances after refractive surgery are described in our article. In most cases of corneal refractive surgery, there is a significant increase in vision disturbances immediately following the procedure. The majority of patients improve between 6 months to 1 year post-surgery. The relation between pupil size and the optical clear zone are most important in minimizing these disturbances in RK. In PRK and LASIK, pupil size and the ablation diameter size and location are the major factors involved. Treatment options for disabling glare are also discussed. With the exponential increase of patients having refractive surgery, the increase of patients complaining of scotopic or mesopic vision disturbances may become a major public health issue in the near future. Currently, however, there are no gold-standard clinical tests available to measure glare disability, contrast sensitivity, or image degradations. Standardization is essential for objective measurement and follow-up to further our understanding of the effects of these surgeries on the optical system and thus, hopefully, allow for modification of our techniques to decrease or eliminate post-refractive vision disturbances.
Contrast Sensitivity↗
Pediatric refractive surgery.
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Adolescent↗
Radial keratotomy and excimer laser photorefractive keratectomy for the correction of myopia.
PURPOSE: To compare our current knowledge of the two most common current refractive surgical procedures for the correction of myopia. METHODS: I reviewed the scientific literature and my personal experience with radial keratotomy and excimer laser photorefractive keratectomy to compare these two modalities. RESULTS: Both radial keratotomy and photorefractive keratectomy are capable of permanently correcting myopic refractive errors. However, each procedure has its individual advantages and disadvantages, with the greatest concern currently being the effect of wound healing on refractive outcome. The procedures are not mutually exclusive. CONCLUSIONS: Both radial keratotomy and photorefractive keratectomy will be used to surgically correct myopia for the next several years until newer technology is developed to improve the predictability and stability of refractive results currently achieved with each procedure.
Cornea↗
New instrument for revision lamellar refractive surgery.
A new instrument that aids in retreating or revising lamellar refractive surgery is described. The edge delineator and lifter can both delineate and lift the edge of a previously made corneal flap.
Cornea↗
[Possible reasons for hypercorrection and incomplete correction of refractive anomalies using photorefractive surgery].
Probable variants of relationships between the major parameters of the eyeball, such as thickness of the cornea, its curvature radius, limbus diameter, and length of the anteroposterior axis of the eye are analyzed on a model representing the structure of external capsule of the eye with the use of schemes. Numerous combinations of these parameters of anatomical structures of the eye are responsible for hypercorrection and poor correction of refraction by examer laser surgery, by photorefraction keratectomy in particular. Along with well-known factors causing regression in remote periods after photorefraction keratectomy (corneal regeneration, effect of ophthalmic tone, accommodation spasm, etc.), individual variants of eye anatomy, neglected during laser exposure planning, can lead to unsatisfactory results of laser treatment.
Humans↗
Everett Kinsey Lecture. Keratocyte apoptosis in refractive surgery.
PURPOSE: The purpose of this paper is to review the relevance of keratocyte programmed cell death (apoptosis) in response to epithelial injury to corneal wound healing following refractive surgery and the pathogenesis of corneal diseases such as keratoconus. METHODS: The TUNEL assay (to detect DNA fragmentation in situ) DNA laddering assay, and transmission electron microscopy have been used to detect apoptosis in human and animal corneas and cultured corneal cells. Molecular and cell biologic techniques have been used to study the cytokine-receptor systems that are involved in modulating apoptosis in the cornea. RESULTS: Keratocyte apoptosis, mediated through the release of cytokines such as soluble Fas ligand and interleukin-1 from the injured epithelium, occurs following refractive surgical procedures like photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Keratocytes that die in the anterior stroma following PRK or along the lamellar cut following LASIK are replenished in 2 to 4 days by proliferation and migration. The replenishing cells are activated myofibroblastic keratocytes that produce collagen, hyaluronic acid, growth factors modulating epithelial healing, and other components of the wound healing response. Keratocyte apoptosis can be inhibited by transepithelial PRK (probably by photodisruption of the apoptotic cytokines in the epithelium) or pharmacologic agents. CONCLUSIONS: Keratocyte apoptosis may be an initiator of the wound healing response in the cornea. Control of this response has the potential to regulate wound healing in the cornea in response to PRK or LASIK. Recent evidence suggests that keratocyte apoptosis mediated by chronic epithelial injury could have a role in the pathogenesis of keratoconus.
Animals↗
Keratocyte apoptosis and corneal antioxidant enzyme activities after refractive corneal surgery.
PURPOSE: Refractive corneal surgery induces keratocyte apoptosis and generates reactive oxygen radicals (ROS) in the cornea. The purpose of the present study is to evaluate the correlation between keratocyte apoptosis and corneal antioxidant enzyme activities after different refractive surgical procedures in rabbits. METHODS: Rabbits were divided into six groups. All groups were compared with the control group (Group 1), after epithelial scraping (Group 2), epithelial scrape and photorefractive keratectomy (PRK) (traditional PRK: Group 3), transepithelial PRK (Group 4), creation of a corneal flap with microkeratome (Group 5) and laser-assisted in situ keratomileusis (LASIK, Group 6). Terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay (to detect DNA fragmentation in situ) and light microscopy were used to detect apoptosis in rabbit eyes. Glutathione peroxidase (Gpx) and superoxide dismutase (SOD) activities of the corneal tissues were measured with spectrophotometric methods. RESULTS: Corneal Gpx and SOD activities decreased significantly in all groups when compared with the control group (P<0.05) and groups 2, 3 and 6 showed a significantly higher amount of keratocyte apoptosis (P<0.05). Not only a negative correlation was observed between corneal SOD activity and keratocyte apoptosis (cc: -0.3648) but Gpx activity also showed negative correlation with keratocyte apoptosis (cc: -0.3587). CONCLUSION: The present study illustrates the negative correlation between keratocyte apoptosis and corneal antioxidant enzyme activities. This finding suggests that ROS may be partly responsible for keratocyte apoptosis after refractive surgery.
Analysis of Variance↗
The wound healing response after laser in situ keratomileusis and photorefractive keratectomy: elusive control of biological variability and effect on custom laser vision correction.
Biological diversity in the wound healing response is thought to be a major factor limiting the predictability of the outcome of refractive surgical procedures such as laser in situ keratomileusis and photorefractive keratectomy. Corneal wound healing is critical to the success of topography-linked or wave front-linked excimer laser ablation to optimize visual performance. This is because of the importance of retaining subtle features of custom ablation and the tendency of epithelial hyperplasia and stromal remodeling to obscure these features following either procedure. The corneal wound healing response is exceedingly complex. Keratocyte apoptosis, which occurs in response to epithelial injury, is the earliest observable event in the wound healing cascades and is therefore an excellent target for pharmacological intervention. Alterations of surgical technique can be designed to limit keratocyte apoptosis and the subsequent events in corneal wound healing. Abnormalities of the cascades could contribute to the pathogenesis of corneal diseases. For example, recent data have suggested that perturbation of the keratocyte apoptosis/mitosis balance could underlie the development of keratoconus in a proportion of patients.
Animals↗
[Piggyback lens implantation for anisometropia in pseudophakic eyes].
OBJECTIVE: Long standing pseudophakia or previous laser capsulotomy make lens exchange for anisometropia or incorrect target refraction difficult. Piggyback lens implantation might be a less traumatic surgical alternative. PATIENTS AND METHODS: Eight patients had a secondary posterior chamber lens implant (PMMA) into the ciliary sulcus. Lens power was estimated by the preoperative refraction according to the refractive vergence formula and was controlled intraoperatively by an automatic refractometer. Surgical access minimized preoperative astigmatism. RESULTS: All patients had disturbing anisometropia of 4.57+/-2.86 D and had undergone cataract surgery 1-13 years previously. Piggyback lens implantation was combined with surgical aspiration of the secondary cataract in three patients. Due to recurrent PVR retinal detachment, one patient received a silicon oil refilling procedure and piggyback lens implantation. The preoperative spherical equivalent was -3.34+/-4.9 D. Mean follow up time was 16.6 months. Postoperative anisometropia was reduced to 1.1+/-1.01 D. The mean absolute deviation from target refraction was 0+/-0.92 D. Elevated IOP or secondary cataract formation in the lens interface were not observed. One patient developed pigment dispersion. CONCLUSION: Secondary piggyback lens implantation into the ciliary sulcus in front of an existing posterior chamber lens is a safe and effective refractive surgical procedure for special cases with predictable refraction.
Aged↗
One-year results of excimer laser photorefractive keratectomy for myopia.
BACKGROUND: Excimer laser photorefractive keratectomy for the correction of myopia is presently under investigation in the United States by the Food and Drug Administration (FDA). The Phase II-B FDA study is being conducted on 75 normally sighted myopic eyes utilizing three currently available excimer lasers. This report presents the 1-year results on 12 myopic eyes treated with the VISX excimer laser system at the Ellis Eye Center at Cedars-Sinai Medical Center in Los Angeles under the Phase II-B FDA protocol. METHODS: Twelve eyes of 12 patients with myopia between -1.75 and -5.00 diopters underwent 193 nm argon/fluoride excimer laser photorefractive keratectomy. The epithelium was mechanically removed, and fixation was accomplished with a suction ring which provided nitrogen flow across the corneal surface. The computer controlled corneal ablations were 5.00 mm in diameter and were accomplished with an iris diaphragm closing from large to small. RESULTS: The preoperative spherical equivalent myopia was -3.50 D (SD = 1.02) and the postoperative myopia was -0.25 (SD = 0.48). Eleven of the 12 patients achieved an uncorrected visual acuity of 20/30 or better and were corrected to within +/- 0.50 D of emmetropia. All corneas demonstrated a mild reticular subepithelial haze which was barely visible at 1 year. There were no vision-threatening complications and none of the eyes experienced a loss of best corrected visual acuity. CONCLUSIONS: In this small trial, the excimer laser appears to be capable of accurately changing the refractive power of the cornea for the correction of myopia with minimal side effects. Only when larger numbers of patients undergo the procedure will we be able to determine the safety and efficacy of photorefractive keratectomy as a refractive surgical procedure.
Adult↗