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Biomedical subjects

W Culbertson

Publications and source records attributed to W Culbertson.

15 recordsLinked to original sources
PubMed2001

Reduction in corneal haze and apoptosis by amniotic membrane matrix in excimer laser photoablation in rabbits.

PURPOSE: To determine whether preserved human amniotic membrane can reduce corneal haze and keratocyte apoptosis induced by excimer laser photoablation in rabbit corneas. METHODS: Excimer photoablation was performed bilaterally in 30 rabbits with a 6.0 mm ablation zone and 120 microm depth using the VISX Star laser with the phototherapeutic keratectomy (PTK) mode. One eye was randomly covered by preserved human amniotic membrane secured with 4 interrupted 10-0 nylon sutures, and the other eye served as the control. The amniotic membranes were removed at 1 week, and corneal haze was graded with slitlamp biomicroscopy by 3 masked corneal specialists biweekly for the ensuing 12 weeks until the rabbits were killed. Another 18 rabbits were divided into 4 subgroups and received PTK alone, PTK with membrane, PTK with sham sutures, or PTK with tarsorrhaphy. All eyes were studied histologically, and 3 eyes in each group were studied by in situ terminal deoxynucleotidyl transferase deoxy-UTP-nick end labeling assay at 1, 3, and 7 days and 12 weeks, respectively. RESULTS: A consistent grading of differences in corneal haze scoring between the control corneas and the amniotic-membrane-covered corneas was noted among the 3 masked observers. Organized reticular post-PTK corneal haze peaked at 7 weeks in both groups, and the corneal haze score in the amniotic-membrane-covered group was significantly less than in the control group from 7 to 12 weeks (all P < .001). Compared to the control corneas, the amniotic-membrane-covered corneas had less inflammatory response at 1 and 3 days, less keratocyte apoptosis in the ablated anterior corneal stroma at 1, 3, and 7 days (P < .001), and less stromal fibroblast cellularity and epithelial hyperplasia at 12 weeks. CONCLUSIONS: Amniotic membrane matrix introduced at an early stage of the corneal wound healing process effectively reduced corneal haze induced by excimer laser photoablation in rabbits. Studies linking suppression of apoptosis in the acute wound-healing process with reduction of subsequent corneal scarring may have useful clinical applications.

Amnion↗
PubMed1994

Ultraviolet solid-state laser (213-nm) photorefractive keratectomy. In vivo study.

BACKGROUND: The pulsed ultraviolet 213-nm solid-state laser has been demonstrated as an alternative to the gas argon-fluoride 193-nm excimer laser for photorefractive keratectomy (PRK). The authors studied the clinical course and histopathologic changes occurring in rabbit corneas after PRK with a 213-nm solid-state laser. METHODS: The 213-nm output of neodymium:YAG frequency-quintupled laser was used to create 5-mm optical zone ablations in seven pigmented rabbit corneas. The radiant exposure was 250 mJ/cm2 delivered through a computer-controlled scanning delivery system with a spot size of 0.5 mm. The target ablation was 4.0 diopters with an estimated ablation depth of 40 microns. A clinical estimate of corneal epithelial healing and stromal haze was made at intervals over the 3-month study period. Animals were killed immediately after ablation, or at 10 days, 1 month, or 3 months after ablation. Corneal tissue was preserved for light microscopy and transmission electron microscopy at each study interval. RESULTS: All corneas re-epithelialized within 10 days postoperatively. Anterior stromal haze was clinically visible at 3 days, increased until approximately 1 month, and then gradually decreased over the succeeding 2 months. Residual subepithelial haze was visible at 3 months. Results of histopathologic study documented normal epithelium healing over time; the basement membrane retained its regular thickness and hemidesmosomes were abundant at 3 months. The anterior stroma had an increased number of fibroblasts at 10 days, many of which remained until 1 month. A mild, transient, cellular reaction occurred throughout the thickness of the stroma and the endothelium. CONCLUSION: Using the 213-nm ultraviolet solid-state laser with a scanning delivery system, PRK shows a similar clinical course and histopathologic findings to the 193-nm excimer PRK study in rabbits. It is a clinically viable procedure for refractive surgery and requires further human clinical trails to determine its efficacy.

Animals↗
PubMed1992

Causes of reduced visual acuity on long-term follow-up after cataract extraction in patients with uveitis and juvenile rheumatoid arthritis.

We reviewed the long-term follow-up on a consecutive series of 16 eyes from ten patients with juvenile rheumatoid arthritis-associated cataracts that were removed by using pars plana lensectomy and vitrectomy. All patients had prominent cataracts, chronic uveitis, posterior synechiae, and vitreitis preoperatively, and had at least 12 months of follow-up postoperatively. The median length of follow-up was 51 months (range, 12 months to ten years). In the early postoperative period, a visual acuity of 20/70 or better was obtained in 13 of 16 eyes (81%). With longer follow-up, the final visual acuity was 20/70 or better in only nine of 16 eyes (56%). The primary categories of delayed visual loss in these cases were glaucoma and macular disease (chronic cystoid macular edema, macular hole, hypotony maculopathy, and recurrent macular pucker). Despite these limitations in maintaining good visual acuity, a pars plana lensectomy and vitrectomy approach is effective for cataracts in these patients with uveitis.

Adolescent↗
PubMed1991

Stability of refraction during four years after radial keratotomy in the prospective evaluation of radial keratotomy study.

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.

Adult↗
PubMed1991

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study five years after surgery. The Perk Study Group.

In the Prospective Evaluation of Radial Keratotomy (PERK) Study, 793 eyes of 435 patients with 2 to 8 diopters (D) of myopia received a standardized surgery consisting of 8 incisions with a diamond-bladed knife set at 100% of the thinnest paracentral ultrasonic corneal thickness measurement and a diameter of the clear zone of 3.0 to 4.5 mm; 97 eyes (12%) received an additional 8 incisions. There were 757 eyes (95%) followed for 3 to 6.3 years. After surgery, uncorrected visual acuity was 20/40 or better in 88% of eyes. The refractive error was within 1 D of emmetropia for 64% of eyes; 19% were myopic and 17% were hyperopic by more than 1 D. Between 6 months and 5 years after surgery, 22% of the eyes had a refractive change of 1 D or more in the hyperopic direction. For 25 eyes (3%) there was a loss of 2 or more lines of best spectacle-corrected visual acuity.

Adult↗
PubMed1991

Corneal topography as a predictor of refractive change in the prospective evaluation of radial keratotomy (PERK) study.

The first operated eyes of 435 patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were evaluated by photokeratography to document the preoperative and postoperative corneal shape. We determined by regression analysis and analysis of variance that the corneal shape preoperatively improved the prediction of the corneal shape 6 months postoperatively in the 3-mm-clear-zone population. The reduction of myopia in all 435 eyes ranged from 1.25 to 9.75 diopters. We studied the effect of the preoperative corneal shape on this variability in the outcome of the surgery using rings 2 and 7 on photokeratography and corneal diameter. In the 3-mm-clear-zone group, eyes with flat prolate corneas had a greater reduction in myopia (4.65 D); those with steeper, more spherical corneas had less reduction in myopia (3.48 D). In addition, eyes with a 3-mm clear zone and flat central corneas alone (8.0 mm = 42.19 D) flattened approximately 0.75 D more than those with steep central corneas (7.0 mm = 48.21 D). In the 3.5-mm and 4.0-mm clear zone groups, the change in corneal curvature was not related to the preoperative curvature. A stepwise regression analysis of the 151 eyes in the 3.0-mm-clear-zone population demonstrated the following predictive equation for radial keratotomy; change in cycloplegic refraction = -14.55 + [-2.097 x average ring-2 radius] + [3.605 x average ring-7 radius] + [0.69 x horizontal corneal diameter] + [0.079 x age] + [-0.379 x spherical equivalent cycloplegic refraction]. There was a 1.17-D observed difference in the effect of radial keratotomy between those eyes with a steep/steep corneal topography (7.2% of the 3.0-mm-clear-zone population) and the flat/flat topography (29% of the 3.0-mm-clear-zone PERK population). A knowledge of corneal topography provides an additional tool for understanding the operative variability of radial keratotomy.

Cornea↗
PubMed1990

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 4 years after surgery for myopia. Perk Study Group.

The Prospective Evaluation of Radial Keratotomy Study is a nine-center clinical trial of a surgical technique to reduce simple myopia by making incisions in the cornea. There were 435 patients (one eye per patient is reported) enrolled in the study with a 91% follow-up rate at 4 years after surgery. After surgery, uncorrected visual acuity was 20/40 or better in 76% of eyes. Fifty-five percent of the eyes had a refractive error within +/- 1.00 diopter; 28% were undercorrected, and 17% were overcorrected by more than 1.00 D. The width of the prediction 90% interval for the refractive change was 4.42 D, indicating a lack of predictability. The refractive error was not stable in some eyes; between 6 months and 4 years after surgery, 23% of eyes had a continued effect of the surgery of more than 1.00 D. For 323 patients with both eyes operated on, 64% stated they wore no optical correction. There were few serious complications. Eleven eyes (3%) lost two or three lines of best corrected visual acuity. Two eyes developed delayed bacterial keratitis without significant loss in best corrected visual acuity.

Adult↗
PubMed1987

Three-year results of the Prospective Evaluation of Radial Keratotomy (PERK) Study.

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refractive error between -2.00 and -8.00 diopters (D). The authors report results for one eye of each patient. The surgical technique consisted of eight incisions using a diamond micrometer knife with the blade length determined by intraoperative ultrasonic pachymetry and the diameter of the central clear zone determined by the preoperative refractive error. At 3 years after surgery, 58% of eyes had refractive error within 1.00 D of emmetropia; 26% were undercorrected and 16% were overcorrected by more than 1.00 D. Uncorrected visual acuity was 20/40 or better in 76% of eyes. The operation was more effective in eyes with a preoperative refractive error between -2.00 and -4.37 D. Between 1 and 3 years after surgery, the refractive error changed by 1.00 D or more in 12% of eyes, indicating a lack of stability in some eyes. In the 435 eyes, there was a small number of complications including six eyes that lost two or three lines of best-corrected acuity, 16 that experienced vascularization of the incisions, 2 that had delayed bacterial keratitis, and 4 that had recurrent epithelial erosions.

Follow-Up Studies↗
PubMed1985

Late onset endophthalmitis associated with filtering blebs.

Thirty-six cases of late onset endophthalmitis in patients with filtering blebs are presented. Onset of endophthalmitis ranged from 4 months to 60 years after bleb formation. Possible contributing factors could be identified only in a minority of patients. Aqueous, vitreous or both were cultured in all cases. Eighty-three percent of eyes were culture positive. Streptococci were the most frequent causative organisms, isolated from 57% of culture positive eyes. Twenty-three percent of eyes grew Hemophilus influenzae. Only two cases were caused by staphylococci. In general, the visual outcome was poor, probably primarily due to the virulence of the infecting organisms. Endophthalmitis remains a risk even many years after creation of a filtering bleb. The microbiologic spectrum in this clinical setting is considerably different from that of recent postoperative endophthalmitis. Based on the bacteriology and clinical course of the patients presented, recommendations for management are discussed.

Adolescent↗
PubMed1984

Visual loss associated with orbital and sinus diseases.

Visual loss associated with orbital and sinuses diseases is mainly due to infectious processes, trauma and neoplasm. From 1975 to 1983, we have encountered 34 such cases. The most common cause in our series was infectious processes, either due to aerobic or anaerobic bacteria or fungi (aspergillosis and phycomycosis). Iatrogenic trauma resulting in complete unilateral irreversible blindness was the second most common etiology in the series of cases that came to our attention for several reasons. Three of our patients with complete blindness, even with documented absence of light perception, secondary to infections or mucocele, underwent emergency surgical treatment with successful restoration of vision. Other patients with various degrees of visual loss experienced improvement, often to normal levels, when timely appropriate surgical treatment was applied. Orbital or optic nerve decompression was used according to pathologic findings encountered. High resolution CT scan has been very helpful in precisely pinpointing the lesion. It is also indispensable in the follow-up of orbital abscesses in order to rule out intracranial complications. Blindness with immediate onset secondary to either external or iatrogenic trauma, with rare exceptions, has a dismal prognosis. Early diagnosis and prompt treatment are essential for salvage of vision or even lives of patients affected by such dreadful complications.

Adolescent↗
PubMedDate not supplied

Stability of refraction and visual acuity during 5 years in eyes with simple myopia. The PERK Study Group.

BACKGROUND: Normal ranges of variability of refraction and visual acuity in adult myopic eyes are needed as a reference standard for assessing the stability of refractive corneal surgery. METHODS: We measured the changes in spectacle-corrected visual acuity and cycloplegic refraction during 5 years for the unoperated eye of 82 patients aged 21 to 57 years in the Prospective Evaluation of Radial Keratotomy Study. The changes were compared for contact lens and non-contact lens wearers. We also compared the 5-year cycloplegic and manifest refractions for these unoperated eyes. RESULTS: Of 77 eyes, 44% gained or lost one Snellen line and 48% experienced no change in spectacle-corrected visual acuity between baseline and 5 years. Only one eye (1%) lost two lines, and 7% gained two lines. The refractive change was less than 1.00 D for 84% of the 37 non-contact lens wearing eyes. Only 13% became more myopic by at least 1.00 D (maximum increase in myopia, 2.00 D), and 3% became less myopic by 1.00 D. Of 45 contact lens wearing eyes, 38% became more myopic by at least 1.00 D. The 5-year manifest refraction was 0.50 D to 1.50 D more myopic than the cycloplegic refraction for 37% of eyes. CONCLUSIONS: We recommend using two or more Snellen lines as the standard for a meaningful change in spectacle-corrected visual acuity in operated eyes, and 1.00 D as a meaningful cutoff for stability of refraction. The wearing of contact lenses can confound the results of stability studies. The difference between the cycloplegic and manifest refractions suggests that the cycloplegic refraction should be used in planning for refractive surgery.

Adult↗
PubMedDate not supplied

Three year results of the Prospective Evaluation of Radial Keratotomy (PERK) study.

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refractive error between -2.00 and -8.00 diopters (D). We report results for one eye of each patient. The surgical technique consisted of eight incisions using a diamond micrometer knife with the blade length determined by intraoperative ultrasonic pachymetry and the diameter of the central clear zone determined by the preoperative refractive error. At three years after surgery, 58% of eyes had refractive error within one diopter of emmetropia; 26% were undercorrected, and 16% were overcorrected by more than one diopter. Uncorrected visual acuity was 20/40 or better in 76% of eyes. The operation was more effective in eyes with a preoperative refractive error between -2.00 and -4.37 diopters. Between one and three years after surgery, the refractive error changed by 1.00 diopter or more in 12% of eyes, indicating a lack of stability in some eyes.

Astigmatism↗
PubMedDate not supplied

Symmetry of refractive and visual acuity outcome in the Prospective Evaluation of Radial Keratotomy (PERK) study.

In the Prospective Evaluation of Radial Keratotomy (PERK) study, the symmetry of refractive and visual acuity outcome was analyzed in 269 patients with bilateral radial keratotomy with a single operation in each eye. Patients were required to wait 1 year after surgery on the first eye before having surgery on the second eye. At 1 year after surgery on the second eye, 98% of patients had 3.00 diopters or less difference between their two eyes in the spherical equivalent of the cycloplegic refraction (100% before surgery), and 96% of patients had 3.00 D or less difference between their two eyes in the amount of refractive power in the vertical meridian (100% before surgery). Thus, surgically induced refractive anisometropia was not a major complication in the PERK study. However, 14% of patients had four to eight Snellen lines difference in the uncorrected visual acuity between their two eyes (1% before surgery), emphasizing that induced asymmetry of refraction is a potential clinical problem for some patients.

Adult↗
PubMedDate not supplied

Intraocular HIV-1-specific IgG synthesis in a patient with CMV retinitis.

A sight-threatening cytomegalovirus (CMV) retinitis is often associated with acquired immune deficiency syndrome (AIDS). We report the detection and quantitation of antibodies specific for CMV and human immunodeficiency virus type 1 (HIV-1) in the vitreous fluid and serum of an AIDS patient suffering from bilateral CMV retinitis. The ratio of the concentrations of HIV-1-specific immunoglobulin G (IgG) to total IgG in the vitreous fluid was found to be higher than that of the peripheral blood, indicating a local production of HIV-1-specific IgG synthesis within the ocular compartment. In contrast, CMV-specific IgG levels in serum were found to be higher than that of vitreous fluid, indicating an intact blood-ocular barrier. CMV and HIV were also isolated from the ocular tissues of this patient. These findings are consistent with the hypothesis that CMV retinitis may be associated with HIV-1 infection of the ocular tissues, which evokes an HIV-1-specific humoral immune response locally within the ocular compartment.

Acquired Immunodeficiency Syndrome↗