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Biomedical subjects

P Asbell

Publications and source records attributed to P Asbell.

9 recordsLinked to original sources
PubMed2001

Effect of external ocular surgery and mode of post-operative care on plasminogen, plasmin, angiostatins and alpha(2)-macroglobulin in tears.

PURPOSE: To determine whether corneal surgery and the mode of post-surgical treatment influence the distribution of plasminogen, plasmin, angiostatins and alpha(2)-macrogobulin in tear fluid. METHODS: Subjects underwent either photorefractive keratectomy (PRK), insertion of intra-stromal corneal rings (ICR), or cataract ablation followed by insertion of an intra-ocular lens (IOL). Post-surgical treatment consisted of prophylactic use of antibiotic and anti-inflammatory agents followed either by patching for 24 hours, or covering the wounded cornea with a bandage soft contact lens. Open eye tear fluid (OTF) was obtained prior to surgery and 10 minutes after patch removal or 24 hours after surgery and thereafter with the bandage lens still in place. After centrifugation, supernatants and controls were western blot analyzed using a protocol designed to allow the simultaneous semi- quantitative detection of alpha2-macroglobulin, plasminogen, plasmin, angiostatins and interleukin-8 (IL-8). RESULTS: No obvious differences were apparent in OTF recovered from contralateral control eyes compared to the surgical eyes in individuals who underwent PRK surgery and whose eyes were covered with a bandage contact lens. In contrast, OTF samples recovered 10 minutes after patch removal from all individuals contained elevated levels of alpha2-macroglobulin and a diverse mixture of elevated levels of plasminogen/plasmin, angiostatins and possibly a plasmin-a1-antiplasmin complex. All of these changes were seen, albeit to a lesser extent, in the patched control OTF samples. IL-8 could not be detected in any sample. The composition of the tear film returned to near normal on subsequent sampling 24 hours after patch removal. CONCLUSIONS: Patching results in a marked increase in the concentration of various proteins which could modulate inflammation and wound healing.

Angiostatins↗
PubMed1997

A double-masked, placebo-controlled evaluation of the efficacy and safety of loteprednol etabonate in the treatment of giant papillary conjunctivitis.

PURPOSE: To evaluate the safety and effectiveness of loteprednol etabonate 0.5% ophthalmic suspension (LE) for reducing the ocular signs and symptoms accompanying contact lens associated giant papillary conjunctivitis (GPC). We conducted a randomized, double-masked, placebo-controlled, parallel study at 11 U.S. academic or private practice clinics. METHODS: Two hundred and twenty adults with contact lens associated GPC were enrolled in this study. Patient were treated with either LE or the loteprednol etabonate vehicle (placebo), q.i.d. for 6 weeks. Papillae, itching, lens intolerance, as well as other signs and symptoms of GPC (0 to 3 or 0 to 4 point severity scales), and intraocular pressure were measured. RESULTS: The proportion of patients treated with LE demonstrating an improvement in papillae of at least one grade (75%) was significantly greater than the proportion of those treated with placebo (50%, P < 0.001). A treatment difference favoring LE was also seen with improvement in itching (92% vs. 76%, P = 0.001) and lens intolerance (84% vs. 66%, P = 0.002). Three patients (all on LE) had an intraocular pressure (IOP) elevation of 10 mm Hg or higher from baseline on at least one on-treatment visit. Cessation of therapy was required in one of these patients. CONCLUSIONS: Both treatments were well tolerated and no serious, unexpected, treatment-related medical events were reported. The rapid therapeutic response, combined with the low incidence, late development, and transient nature of any IOP elevation suggests that LE may be helpful in treating GPC.

Administration, Topical↗
PubMed1994

Clinical evaluation of Purilens, an ultraviolet light contact lens care system.

Purilens is a new contact lens care system that uses ultraviolet light and subsonic turbulence for lens cleaning and disinfection. In a single hands-off process using only preservative-free sterile saline, the lenses are ready to wear after a 15-minute cycle. This study was designed to test the safety of this contact lens care system. A total of 84 contact lens wearers from six centers were enrolled in the 3-month study, which comprised an initial visit and follow-up visits at 1, 2, 4, 8, and 12 weeks. At the end of the study, lenses and units were collected and a questionnaire was completed. Seventy-six of the 84 subjects (168 eyes) completed the study. No severe eye complications were reported, and no patients were removed from the study because of ocular problems or complications associated with the device or its use. Four patients were removed from the study for noncompliance with follow-up. Another four patients were active for 2 months, but were requested by the sponsor to complete the study 1 month early to complete data collection. Patient satisfaction was high. The study suggests that Purilens may be considered as an alternative for contact lens cleaning and disinfection.

Adolescent↗
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↗
PubMed1986

Radial keratotomy and glare effects on contrast sensitivity.

After radial keratotomy (RK) to correct myopia, some patients complain of 'glare'. Effects of a glare source on contrast sensitivity were measured in fifteen patients after unilateral RK. With each eye, determinations were made of the contrast required for detection of steady gratings (spatial frequencies of 0.7 and 2.9 cycles/deg), and for detection of flicker (unpatterned field flickering at rates of 8, 16, and 32 Hz). Grating or flicker was presented on a centrally fixated 4 deg test target (34 cd/m2 mean luminance), surrounded by a diffuse glare source (1700 cd/m2 mean luminance). For each stimulus, contrast thresholds were determined with glare-source off and with glare-source on. 'Glare loss' was defined as the decrement in contrast sensitivity measured with the glare source on. Significant findings were: (1) Both eyes showed glare losses for detection of gratings and for detection of flicker; (2) Spectacle lenses increased glare losses both for gratings and for flicker; (3) The RK eye showed a larger glare loss for flicker than the unoperated eye, but a smaller glare-loss for gratings; (4) For both flicker and gratings, glare loss tended to be greater in the RK eye, compared to the unoperated eye, in subjects who had larger pupil diameters in the testing situation; (5) The psychophysical measurements obtained in this study were not significantly correlated either with a questionnaire index of glare complaints or with the score obtained with the Miller-Nadler GlareTester.

Adult↗
PubMed1982

Ulcerative keratitis. Survey of 30 years' laboratory experience.

During a 30-year period, causative organisms were identified on Gram's stain and culture in 547 of 677 cases of infectious corneal ulcers. Even if no organisms were seen on Gram's stain, culture results were often positive. Staphylococcus was the most common isolate; Moraxella, Pseudomonas, and Streptococcus pneumoniae were the next most frequent pathogens. Only 1% of cases were fungal. Of some help in identifying the causative organism were locations, presence or absence of hypopyon, and perforation of the ulcer. Most marginal lesions were a result of staphylococcal infection; central lesions were more likely to be Gram-negative ulcers. Fungal ulcers were identified by laboratory workup and not by clinical characteristics. Moraxella infection was observed almost exclusively in malnourished patients. Pseudomnas ulcers were often seen in patients with large body burns or patients receiving respiratory assistance. Gentamicin and neomycin were the most effective treatments.

Adolescent↗
PubMed1981

Relative blue-light extinction in lens nucleus related to age and cataract.

The extent of visual function loss from nuclear cataractous change can be estimated by observing the extinction of blue light compared to white light as a function of sagittal lens depth in standard slit lamps. Apparent extinction (loss of transmissivity) of 50% or more of the depth of the lens in blue light of maximal intensity compared to white light at minimal intensity is associated with marked visual loss. However, this transmissivity ratio of 0.5 or less also applies if light intensity remains constant and the blue filter is simply moved in and out of the light beam. Therefore, if 50% or more of the lens appears dark to blue-filtered light, nuclear changes have significantly decreased effective visual acuity. Relative blue-light extinction associated with nuclear change that may be amenable to surgical correction can thus be distinguished from the extinction effect caused by age alone.

Adolescent↗
PubMedDate not supplied

Disposable hydrogel contact lenses for extended wear.

Nine ophthalmologists and nine optometrists conducted a premarket study of the Acuvue disposable contact lens manufactured by Vistakon, Inc. Of the 812 patients offered the lens, 733 accepted it and were enrolled in the study. These patients were fitted with the lens and followed for a period of 8 months. Over 98% of these patients had 20/25 or better vision on initial fitting; and subjective ratings of lens comfort were very good. Only 3.7% (27 of 733) discontinued wearing their lenses during the study period. Thirty-four patients (5.6%) experienced a problem while wearing their contact lenses.

Adolescent↗