SEARCH · PubMed Health

Results for “Refractive Surgical Procedures”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources

PubMed1993

Retinal detachment as a potential hazard in surgical correction of severe myopia with phakic anterior chamber lenses.

Phakic anterior chamber lenses have been proposed as an effective refractive surgical procedure for the correction of severe myopias. We managed three cases of retinal detachment that complicated this operation. Two patients had retinal detachment in the immediate postoperative period at the fourth and sixth weeks, respectively. Both patients had preoperative equatorial lattice degeneration, which was prophylactically managed with argon laser in one case. The third patient developed retinal detachment at the eighth postoperative month and was associated with a severe fibrinoid uveitis and a combined exudative and rhegmatogenous retinal detachment. This third patient did not have any previous retinal degenerative lesion. Scleral buckling was successful in two of the patients, whereas the patient with preoperative inflammation required vitreous surgery because of proliferative vitreoretinopathy. The retinas were reattached in all three patients without explanting the phakic anterior chamber lens, but severe loss of visual acuity occurred in one patient. Retinal detachment should be regarded as a potentially important hazard in this type of refractive surgery.

Adult↗

PubMedDate not supplied

Differences in keratocyte apoptosis following transepithelial and laser-scrape photorefractive keratectomy in rabbits.

BACKGROUND: Anterior stromal keratocyte cells undergo programmed cell death (apoptosis) in response to corneal epithelial injury. Keratocyte apoptosis may be an initiator of the corneal wound healing response that includes keratocyte proliferation and activation, as well as changes to the overlying epithelium, occurring following refractive surgical procedures such as photorefractive keratectomy (PRK). This study compared the effect of laser-scrape and transepithelial PRK on keratocyte apoptosis. METHODS: Photorefractive keratectomy was performed in both eyes of 10 New Zealand white rabbits using the Summit Apex excimer laser. Surgery was performed using transepithelial PRK in one eye and laser-scrape PRK in the other. The central cornea was analyzed at 4 hours after surgery using a quantitative TUNEL assay that detects fragmented DNA characteristic of apoptosis. Hepatocyte growth factor (HGF) production by keratocytes was detected by immunocytochemistry. RESULTS: Average apoptotic cells per 400X microscopic field determined by 2 independent masked observers were 0.9 +/- 0.5 (scanning electron microscopy) and 0.2 +/- 0.2 in the transepithelial PRK group compared with 5.1 +/- 2.9 and 4.1 +/- 3.2 in the laser-scrape group. The difference between the two groups was statistically significant for both observers (P < .05, ANOVA). HGF was detected within keratocytes throughout the corneal stroma. Less HGF was detected in the anterior stroma in the laser-scrape group at 4 hours after surgery, consistent with more anterior keratocyte apoptosis in this group. CONCLUSIONS: Transepithelial PRK induced less anterior keratocyte apoptosis in rabbits than laser-scrape PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and subepithelial scarring.

Animals↗

PubMed1996

An ultrasonic technique for the measurement of the elastic moduli of human cornea.

In the hopes of reducing the unpredictability associated with refractive surgical procedures and ultimately improving surgical techniques, many investigators have attempted to determine the elastic moduli of the cornea. Techniques such as stress-strain tests of corneal strips and the measurement of mercury drop displacement in a whole eye under increasing pressure have resulted in a range of values for Young's modulus from 10(5) to 10(7) Nm-2. Both of these methods are limited because these mechanical tests cannot be performed in the physiological state and because of the large amount of force applied during testing. We used an ultrasonic technique to determine the elastic moduli of the human cornea. Two groups of six corneas prepared under different conditions (in saline and in dextran) were examined separately and the shear waves were generated and detected in these 12 human eye bank eyes. All the waveforms were digitized and saved in files of binary format. Fast Fourier transformation (FFT) was applied to calculate the speed and attenuation of the shear wave. Using the resulting wave speeds and attenuation coefficients, the Young's moduli of the corneal samples were calculated as (5.3 +/- 1.1) x 10(6) Nm-2 and (2.0 +/- 1.0) x 10(7) Nm-2 for cornea samples prepared in saline and in dextran at 2.25 MHz, respectively.

Aged↗

PubMed1991

Gel injection adjustable keratoplasty.

Gel injection adjustable keratoplasty (GIAK) is a new refractive surgical procedure designed for the correction of myopia by injection of a gel substance into the peripheral corneal stroma. This paper describes the GIAK technique and reports the results obtained in 21 fresh cadaveric eyes using the procedure. After a deep interlamellar canal has been dissected with a helicoid spatula surrounding the visual axis, the gel is injected under keratometric control. In the 1st group of 14 eyes, the degree of correction varied from 2.2 to 12.8 D; there was a direct relationship between the amount of gel injected and the keratometric change. In the 2nd group of 7 eyes, the adjustability of the procedure was demonstrated. Through partial extraction of the gel and subsequent modification of the corneal curvature, the previously induced keratometric changes could be reversed or altered to a specific extent. Following the initial injection of gel to a targeted flattest meridian power of 35 D, an average value of 35.8 +/- 0.5 D was achieved in these eyes. We subsequently attempted to increase the flattest meridian to 40 D by partial removal of the gel and achieved a mean value of 40.2 +/- 0.4 D. Average presurgical astigmatism of 1.497 +/- 0.737 D was reduced to a postsurgical reading of 0.941 +/- 0.590 D (P = 0.005, Student's paired t-test), indicating an autocorrection by autodistribution of the gel inside the canaliculus (Laplace's law). GIAK is a simple, inexpensive procedure designed for the correction of myopia that has the added advantage of reducing preexisting astigmatism without encroaching on the visual axis.

Astigmatism↗

PubMed2005

Microincisional cataract surgery and Thinoptx rollable intraocular lens implantation.

BACKGROUND: Microincisional cataract surgery is a safe procedure with a very short learning period for an experienced cataract surgeon and rollable ultrathin intraocular lenses eliminate the need for enlargement of corneal incision. The purpose of the study was to evaluate the safety and efficacy of cataract surgery through a corneal microincision and implantation of rollable ultrathin intraocular lenses. The setting was Dokuz Eylul University Medical Faculty, Ophthalmology Department, Izmir, Turkey and SSK Okmeydani Hospital, Ophthalmology Clinic, Istanbul, Turkey. PATIENTS AND METHODS: Ninety eyes in 85 patients were operated on through clear corneal microincisions with sleeveless phacoemulsification and rollable intraocular lenses were implanted. Forty-six of the patients were men and 39 were women between the ages of 27 and 83, with a mean of 51 years. Two eyes had atrophic senile macular degeneration, 4 eyes had nonspecific retinal pigment epithelial changes with chorioretinal atrophy, and 4 patients had diabetes mellitus without retinopathy. Three eyes had posterior capsular opacifications of unknown etiology. Two eyes had primary open angle glaucoma (PAAG) with cup to disc ratios of about 0.5. Three eyes had dense nuclear sclerosis of grade 4 with very low visibility of retinal structures. Other patients had no ocular or systemic pathology other than nuclear/corticonuclear cataract of grade 2-3. Uncorrected and best spectacle-corrected distance and near visual acuities, keratometric values, and refractive status were noted preoperatively and 1 week, 1 month, and 6 months postoperatively. Statistical analysis of keratometric changes between preoperative and postoperative findings was performed using the paired samples t test. RESULTS: At 6 months postoperatively, 1 patient had a best spectacle-corrected visual acuity (BSCVA) of 0.2, the patient with atrophic senile macular degeneration. The rest of the eyes achieved a BSCVA of 0.63 or better. At 6 months postoperatively, 55 (61.11%) eyes had uncorrected visual acuities (UCVA) equal to or better than 0.8 and 83 (92.22%) eyes had BSCVA equal to or better than 0.8 according to the Snellen chart. The mean postoperative corneal astigmatisms at 1 week, 1 month, and 6 months were 0.69+/-0.43 D, 0.66+/-0.46 D and 0.65+/-0.48 D respectively. Statistical analysis revealed a significant change in corneal astigmatisms at the 1st week visit (p<0.05), but not at the 1st and 6th month visits (p>0.05) compared with preoperative findings. CONCLUSION: Based on the limited data in the literature and in this study, it is not possible to make concrete decisions about the benefits and disadvantages of the ThinOptx IOL for longer durations. Intraoperatively, this IOL apparently eliminates the need for enlargement of the corneal incision during implantation. However, the statistical insignificance of induced astigmatisms after microincisions and classical phacoincisions should also be taken into consideration. We conclude that ThinOptx IOL is a pioneering intraocular lens implant that will contribute to the exciting future of cataract refractive surgical procedures. However, both clinical and laboratory investigations are needed to clearly describe the long-term effectiveness of this new rollable IOL.

Adult↗

PubMedDate not supplied

[Excimer laser subepithelial ablation (ELSA) or laser epithelial keratomileusis (LASEK) - a new kerato-refractive procedure for myopia. Surgical technique and first clinical results on 24 eyes and 3 months follow-up].

BACKGROUND: Laser epithelial keratomileusis (LASEK) is a new keratorefractive surgical procedure to treat myopia and possibly other refractive errors, which combines the advantages while eliminating the disadvantages of both PRK (pain, corneal haze) and LASIK (flap complications, interface complications). Our results with LASEK are very promising and because this technique is currently not very popular in Germany we here with introduce the surgical technique and our first clinical results. PATIENTS AND METHODS: We treated 24 eyes (18 patients) by LASEK. The preoperative myopia was between - 1.50 and - 6.00 D with an astigmatism less than 1.00 D. Surgery starts with an incision in the epithelium by using a special microtrephine. After the application of 20 % ethanol for 20 seconds a hinged epithelial flap is created and the laser ablation performed with a Keracor 117 excimer laser. Finally, the epithelial flap is repositioned and secured using a bandage contact lens and artificial tears for 3 days. RESULTS: In all eyes the creation of the epithelial flap and its repositioning presented no problems. None of the eyes showed any postoperative epithelial instability. However, one eye lost the contact lens and the epithelial flap during the first postoperative day. Postoperatively, none of the patients complained of significant pain; however, the contact lens caused some foreign body sensation. After 3 months all eyes were within +/- 1.0 D and 20/24 eyes (84 %) within +/- 0.50 D of emmetropia (spherical equivalent). None of the eyes showed significant haze. CONCLUSIONS: Although, the number of treated eyes is small and the postoperative follow-up is short LASEK seems to be an effective and safe procedure for the treatment of myopia.

Adult↗

PubMed1983

Refractive keratoplasty. Tissue dyes and cryoprotective solutions.

The cryoprotective dye solution KM-26 (0.25% kiton green, 8% glycerin, and 4% dimethyl sulfoxide), which is presently used for all lamellar refractive surgical procedures, was evaluated and compared to other dyes that can stain corneal tissue. With the use of canine and human eye bank tissue, we found kiton green and light green to produce the least tissue alteration and to destain readily. Glycerin with or without dimethyl sulfoxide or dye was deleterious to the endothelium in the area under the keratectomized recipient bed. On the basis of our findings, glycerin and dimethyl sulfoxide should be deleted from the cryoprotective solution and a 0.1% concentration of light green in balanced salt solution or M-K medium should be used and the frozen tissue should be thawed in a balanced salt solution or M-K medium to eliminate potential damage to the recipient corneal endothelium.

Animals↗

PubMed1985

Histopathology of a case of epikeratophakia (aphakic epikeratoplasty).

An epikeratoplasty button was removed by penetrating keratoplasty 31 months following an aphakic epikeratoplasty. The epithelium over the donor cap was thickened with numerous surface abnormalities. Bends and fractures in the donor Bowman's membrane were found throughout the length of the specimen. A significantly decreased number of keratocytes were found in the anterior half of the donor lenticule; the posterior half of the lenticule was acellular. The interfibrillar collagen distance of the donor lenticule was significantly increased compared with that of the recipient host cornea. The central thickness of the lenticule increased the total corneal thickness by 56%. Abnormal keratocytes were found in the underlying recipient corneal stroma. Based on this study, the histopathologic features of epikeratoplasty appear to be similar to those documented in the other lamellar refractive surgical procedures of keratophakia and keratomileusis.

Adult↗

PubMed1998

Assessment of stress fiber orientation during healing of radial keratotomy wounds using confocal microscopy.

Radial keratotomy (RK) is a refractive surgical procedure in which partial thickness incisions are made in the cornea in order to alter its shape. Previous studies suggest that RK wounds undergo changes in wound gape in response to the ingrowth of myofibroblasts which mediate subsequent wound contraction and may modulate changes in corneal curvature seen after RK. A recent quantitative analysis of f-actin organization in full-thickness incisional wounds in the rabbit demonstrated that microfilament bundles (stress fibers) present in myofibroblasts align parallel to the long axis of the wound during wound contraction. To investigate whether the same pattern of alignment occurs after RK, a similar analysis of f-actin organization was undertaken using the cat RK model. Radial keratotomy wounds were studied from 10 to 28 days after surgery using en block staining with fluorescein isothiocyanate (FITC) phalloidin, and three-dimensional (3-D) datasets (z-series of en face optical sections) were collected using laser confocal microscopy at various regions within the wound. In addition, conventional en face sections were double-labeled using combinations of phalloidin and antibodies to fibronectin and alpha 5 beta 1 integrin. Myofibroblast ingrowth started in the bottom of the wound and progressed anteriorly. At 10 to 14 days, f-actin was predominantly distributed in long, thick bundles (stress fibers) within the wound. These fibers appeared to be randomly oriented anteriorly, but became progressively more aligned with the long axis of the wound posteriorly. At 21 days, the stress fibers were predominantly oriented parallel to the long axis of the wound at all levels. F-actin, fibronectin and integrin were coaligned at both the 14 and 21 day time points. Since the majority of wound closure occurs between 14 and 28 days after surgery, we conclude that parallel alignment of the actin filament-fibronectin-integrin assembly in the cat RK model is associated with wound contraction.

Actin Cytoskeleton↗

PubMed1992

Corneal sensitivity after photorefractive keratectomy.

Corneal anesthesia or hypesthesia can complicate refractive surgical procedures such as epikeratophakia and radial keratotomy. An esthesiometer was used to measure the corneal sensitivity in unoperated-on corneas and fellow corneas after excimer laser photorefractive keratectomy. Decrease in corneal sensitivity was noted within six postoperative weeks, with mean sensitivity being 75.2% +/- 13.3% of normal. Within the first three postoperative months, the patients operated on for correction of compound astigmatism recovered 95.7% +/- 5.3% of the corneal sensitivity, whereas the patients operated on for correction of severe myopia recovered 86.2% +/- 11.2% (P = .07). None of the patients had delayed epithelial healing or recurrent corneal erosions during the time of decreased corneal sensitivity. In otherwise normal myopic eyes, photorefractive keratectomy measurably reduced corneal sensitivity for several postoperative weeks.

Adult↗

PubMed1993

Corneal topographic alterations in normal contact lens wearers.

PURPOSE: The purpose of this study is to investigate the corneal topography of visually normal asymptomatic eyes that wore rigid and soft contact lenses compared with visually normal eyes that had never worn contact lenses. METHODS: Thirty-seven normal corneas and 74 corneas in asymptomatic eyes that wore rigid (12 polymethylmethacrylate and 23 gas-permeable) and soft (26 daily-wear and 13 extended-wear) contact lenses for refractive correction underwent slit-lamp examination, keratometry, computer-assisted topographic analysis, refraction, and rigid contact lens over-refraction. RESULTS: Topographic abnormalities tended to be more common and more severe in corneas that wore rigid contact lenses, but significant changes were noted in some eyes that wore daily-wear or extended-wear soft contact lenses. A number of eyes in the rigid polymethylmethacrylate (9 of 12) and rigid gas-permeable (6 of 23) contact lens groups had a correlation between the most frequent resting position of the contact lens and the corneal topography, with relative flattening of the corneal contour beneath a decentered lens. A total of 10 eyes in the rigid contact lens groups had a 1-line decrease in best spectacle-corrected visual acuity attributable to contact lens-induced topographic abnormalities. CONCLUSIONS: Corneal topographic alterations are common in asymptomatic contact lens wearers and are frequently detectable only with computer-assisted topographic analysis. It is important that topographic abnormalities be excluded in contact lens wearing eyes before refractive surgical procedures.

Contact Lenses↗

PubMed1997

Unilateral keratoconus. Incidence and quantitative topographic analysis.

OBJECTIVE: This study was designed to determine the incidence of unilaterality in a population of patients with clinical keratoconus and to compare quantitative descriptors of topography between affected corneas from patients with unilateral keratoconus and corneas of patients with bilateral disease. DESIGN: Retrospective clinical study with new evaluation of some patients. PARTICIPANTS: One hundred sixty-four patients from the University of Texas South-western Medical Center and Wills Eye Hospital who were diagnosed to have moderate-to-advanced keratoconus on the basis of characteristic topographic patterns associated with corneal thinning. INTERVENTION: Corneal topography was evaluated in both eyes of each patient. MAIN OUTCOME MEASURES: Quantitative descriptors of corneal topography were compared between 5 affected corneas of patients with unilateral keratoconus (combined cases from University of Texas Southwestern, LSU Eye Center, and Wills Eye Hospital) and 15 corneas of patients with moderate-to-advanced bilateral keratoconus (1 cornea from each patient). Indices selected for statistical analysis were the Keratoconus Predication Index (KPI), Surface Asymmetry Index (SAI), and Surface Regularity Index (SRI). RESULTS: Three (1.83%) of 164 patients with moderate-to-advanced keratoconus had no topographic evidence of keratoconus in the opposite eye. There were no statistically significant differences in KPI, SRI, or SAI values between the affected corneas of patients with unilateral and bilateral keratoconus. Over a period of 4 years of observation, signs of keratoconus in the previously normal eye developed in a patient with unilateral keratoconus. CONCLUSIONS: The authors found no differences in the quantitative descriptors of corneal topography between corneas with keratoconus from unilateral and bilateral cases. The authors' results suggest that the incidence of "unilateral" keratoconus is very low. Patients initially diagnosed with unilateral keratoconus, if observed for a sufficient period, commonly had signs of keratoconus develop in the opposite eye. The possibility that all cases of unilateral keratoconus may eventually become bilateral cannot be excluded. Therefore, refractive surgical procedures should not be performed on apparently normal corneas when keratoconus is detected in the opposite eye.

Cornea↗

PubMed2006

[Reactivation of ocular toxoplasmosis after laser in situ keratomileusis].

Laser in situ keratomileusis (LASIK) is a safe and efficient refractive surgical procedure that provides excellent results in most cases. Several complications have been reported, most of them related to the posterior segment of the eye. Although they are quite rare, a growing number of vitreoretinal pathologic conditions after LASIK have been reported. To date no article has reported an inflammatory or infectious disease of the posterior segment after a LASIK procedure. We report a case of reactivation of toxoplasmic chorioretinitis that occurred 5 days after a LASIK procedure. Clinical outcome was spontaneously favorable after 1 month, with no loss of vision. Although a causal effect between LASIK and toxoplasmic chorioretinitis reactivation cannot be proven with a single case report, we stress the importance of dilated fundus examination in LASIK preoperative assessment: our case suggests that in the presence of preoperative toxoplasmic chorioretinitis scars, increased retinal monitoring is required.

Adult↗

PubMed1993

Effective spherical aberration of the cornea as a quantitative descriptor in corneal topography.

Following excimer laser photorefractive keratectomy and other refractive surgical procedures, complaints of halos, glare, and monocular diplopia are common. These procedures increase the asphericity of the cornea, which may cause the optical distortions. We used ray tracing techniques to estimate the longitudinal monochromatic aberration of the cornea from the measured corneal topography (effective spherical aberration) in 15 normal eyes with varying degrees of astigmatism and in ten eyes after photorefractive keratectomy. Best spherical corrected visual acuity in the astigmatic eyes was highly correlated with effective spherical aberration (r = -0.9527, P < .001). In the eyes that had photorefractive keratectomy, the effective spherical aberration was highly correlated with measured glare visual acuity (r = 0.875, P < .002). These results suggest that effective spherical aberration is a valuable topographic measure that provides information about the optical performance of aspheric corneas.

Astigmatism↗

PubMed2006

[Posterior segment complications of laser in situ keratomileusis (LASIK)--a survey of the literature].

During the past years refractive surgical procedures and particularly laser IN SITU keratomileusis (LASIK) have become established by clinical and experimental studies and are performed worldwide in a high number. This paper provides a survey of the published posterior segment complications of LASIK that may occur albeit very rarely. Additionally, current clinical and experimental hypotheses regarding the pathogenesis of those complications are discussed. Currently a cause-effect relationship between LASIK and reported posterior segment complications has not been proven although a very high number of LASIK procedures have been performed worldwide.

Choroid↗

PubMed1996

[Biomechanical study of corneal stability after radial keratotomy].

BACKGROUND: Radial Keratotomy is one of the most frequent refractive surgical procedures performed worldwide. It results in considerable alterations of the corneal structure. What does this mean for the mechanical properties of the cornea? METHODS: Intraocular pressure was increased via a 180 degrees tilt. Before and during this procedure, corneal topography was measured by photokeratoscopy. We examined 36 patients after RK and 25 controls who had not undergone any surgical procedure. RESULTS: The corneal center flattened by 0.523 +/- 0.054 dpt (p < 0.01) in the RK patients and by 0.187 +/- 0.045 dpt (p < 0.05) in the control group. CONCLUSION: Even several years after radial keratotomy, corneal stability is still decreased.

Adult↗

PubMed2003

Retinal complications of phakic intraocular lenses.

High myopia has always been a challenge for refractive correction. Current laser surgical techniques, however, fall short of correcting high refractive errors due to lack of predictability, regression, corneal ectasia, and introduction of high order optical aberration. Phakic intraocular lenses (IOL) have been proposed as an effective refractive surgical procedure for the correction of severe myopia, but, despite recent advances in implant material technology and design, their concept is still under clinical investigation. Most of the concern regarding the complications of phakic IOLs focuses on the anterior segment of the eye. This review examines the posterior segment complications associated with phakic IOL implantation, evaluates possible pathogenetic mechanisms and discusses posterior segment complications, prevention and management.

Animals↗

PubMed2004

Choroidal neovascularization following hyperopic LASIK surgery.

Laser in situ keratomileusis (LASIK) is a well-accepted refractive surgical procedure; however, reports of complications of hyperopic surgery are scarce. This is the first report of bilateral macular choroidal neovascular membrane following bilateral hyperopic LASIK surgery. It highlights important considerations in older patients undergoing the procedure.

Choroidal Neovascularization↗