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Biomedical subjects

T C Prager

Publications and source records attributed to T C Prager.

54 records · Page 3Linked to original sources
PubMed1987

Management of increased intraocular pressure after cataract extraction.

We measured the change in intraocular pressure prospectively after extracapsular cataract extraction in 80 eyes after treatment with either pilocarpine gel, pilocarpine 4% solution, timolol 0.5% solution, or placebo. Intraocular pressure, pupil size, and anterior chamber cellular reaction were measured in a masked fashion on the first day after surgery. A significant increase in intraocular pressure was found in all groups postoperatively when compared with baseline values (P less than .001). Eyes treated with pilocarpine gel had an average intraocular pressure increase of 4.2 +/- 2.1 mm Hg (mean +/- 1 S.E.), eyes treated with pilocarpine 4% eyedrops had an average increase of 9.8 +/- 2.8 mm Hg, and eyes treated with timolol demonstrated an intraocular pressure increase of 8.25 +/- 3.19. The intraocular pressure in untreated eyes (controls) increased by an average of 12.9 +/- 2.7 mm Hg. Only the difference in intraocular pressure change between the eyes treated with pilocarpine gel and control eyes was statistically significant (P = .025). Postsurgical intraocular pressure exceeding 25 mm Hg was observed in three of 20 pilocarpine gel treated eyes (15%) and 11 of 20 control eyes (55%). Pilocarpine treatment was not associated with noticeable changes in intraocular inflammatory response, nor were significant ocular or systemic adverse reactions observed. A single administration of pilocarpine gel is effective in reducing increased intraocular pressure for the first 24 hours after extracapsular cataract extraction.

Cataract Extraction↗
PubMed1987

Effectiveness of botulinum toxin therapy for essential blepharospasm.

The effectiveness of Botulinum toxin (Oculinum) therapy in 76 patients with the diagnosis of essential blepharospasm was analyzed. Botulinum offers relief to almost all patients suffering from essential blepharospasm, however, this relief is usually temporary. The response time for repeated treatments tended to be longer than the first treatment. Patients with mild blepharospasm responded significantly longer to Botulinum injection, than those with severe spasms. The response to Botulinum was not significantly different in patients with Meige syndrome than in patients with only essential blepharospasm. Patients previously treated surgically for essential blepharospasm did not respond differently than those patients with no previous surgical therapy. The authors believe that Botulinum toxin injection is an effective, although temporary, mode of therapy for the signs and symptoms of this focal dystonia. The authors recognize that there may be psychologic factors affecting the response.

Blepharospasm↗
PubMed1987

Brightness acuity test and outdoor visual acuity in cataract patients.

The disparity between functional outdoor vision and the acuity measured in the standard refracting lane is well known among clinicians. A simple device, the brightness acuity tester (B.A.T.), was developed to predict a patient's functional outdoor acuity. The B.A.T. has an illuminated hemispheric bowl, 60 mm in diameter, with a 12-mm aperture. Fourteen normals and 50 patients with cataracts were tested using the B.A.T. and then tested outside in bright sunlight. The B.A.T. correlated extremely well (r = +0.84, P less than .0001) with the acuities measured outside. There was no decrease in visual acuity in the 14 normal patients, but there was a one to ten line decrease in vision among the cataract patients. Upon retesting, the B.A.T. scores did not vary, while outside testing scores did change due to variable outdoor ambient light levels on sunny days. The B.A.T. is a simple, repeatable, useful test for predicting functional outdoor acuity.

Cataract↗
PubMed1987

Epikeratophakia without annular keratectomy.

Nineteen patients (20 eyes) underwent epikeratophakia for correction of high myopia. In contrast to the conventional surgical method utilizing an annular keratectomy, no keratectomy was performed in these patients. The surgical procedure is discussed. Preliminary results (up to six months) indicate that the omission of an annular keratectomy has no effect on graft clarity or viability. The weighted-average percent correction over six months postoperatively was 102%.

Cornea↗
PubMed1987

The use of thiphenamil hydrochloride (Trocinate) to control wound contraction after radial keratotomy.

We studied the efficacy of a topical smooth muscle antagonist, thiphenamil hydrochloride (Trocinate), in inhibiting wound contraction in ocular tissue. Fifteen New Zealand white rabbits underwent standard eight-incision radial keratotomy (RK), and eyes were randomly assigned to treatment or control groups. As demonstrated by slit lamp corneal photographs and by ocular histology, transient inhibition of wound contraction lasted approximately one week in all treatment eyes. We conclude that thiphenamil has a temporary, but specific, effect in controlling wound contraction after ocular surgery. Smooth muscle antagonists may be useful for managing cicatricial conditions of the eye.

Animals↗
PubMed1986

Improving the predictability of intraocular lens power calculations.

We reviewed the intraocular lens power calculations on 512 posterior chamber lens implantations and determined four ways to reduce the estimated 5% incidence of large postoperative refractive "surprises" (greater than 2 diopters [D]): First, preoperatively identify those patients who have greater than a 1-D difference between the theoretical and linear regression formulas. Second, repeat axial length and corneal power measurements in these patients to eliminate random error. Third, develop an individualized theoretical formula that accounts for constant bias. Fourth, encourage manufacturers to improve instrumentation for measuring corneal power and axial length. We also examined the disparity between the linear regression formula and the curvilinear theoretical formula.

Anterior Chamber↗
PubMed1985

Determining intraocular lens power within the eye.

A method is described for determining the power of an intraocular lens (IOL) within the eye by measuring the horizontal dimension of the corneal reflected image (Purkinje-Sanson I) and the anterior IOL reflected image (Purkinje-Sanson III) as seen through a standard slitlamp with a target positioned 68 mm anterior to the focal plane of the biomicroscope. The horizontal K-reading (at 180 degrees) and the anterior chamber depth are the two other parameters necessary to calculate the exact power of the IOL. Seven tables that use these four measurements have been provided, eliminating the need for complex calculations. To determine the accuracy of this technique, ten implanted IOLs ranging from 9 diopters (D) to 27 D were chosen and their powers calculated; these calculated values were then compared to the actual IOL powers. The largest error was 0.5 D and the average error was 0.17 D.

Anterior Chamber↗
PubMed1983

Goldmann applanation tonometry in patients with regular corneal astigmatism.

By averaging vertical and horizontal applanation readings from the Goldmann tonometer, we developed a simple technique that accurately measures intraocular pressure in patients with regular corneal astigmatism. This procedure eliminates the need for keratometry and oblique alignment of the applanator. When the applanator is oriented normally, with the mires displaced horizontally, intraocular pressure is underestimated for with-the-rule corneal astigmatism and overestimated for against-the-rule corneal astigmatism. The error is approximately 1 mm Hg for every 4 diopters of astigmatism. For oblique axis corneal astigmatism, the error is smaller and approaches zero when the axis is either 45 or 135 degrees.

Analysis of Variance↗
PubMed1983

The use of vitreous fluorophotometry to distinguish between diabetics with and without observable retinopathy: effect of vitreous abnormalities on the measurement.

Ten age-matched normals, diabetics with retinopathy, and diabetics without observable retinopathy were evaluated by vitreous fluorophotometry (VFL) using a 0.15 mm and a 0.45 fiberoptic probe in a photomultiplier system as well as a commercially available photodiode instrument to determine whether differences in intraocular sodium fluorescein levels could be detected among the three groups. Each subject was injected in the antecubital vein with 7 mg/kg of sodium fluorescein (25% solution) and measurements were taken 1 hr postinjection at 4.5 mm and 7.5 mm from the retina. The influence of choroidal fluorescein and ocular pigmentation are reduced at these locations. We found that a breakdown in the blood-ocular barrier may not be present early in the course of diabetes. Furthermore, no significant difference was found between normals and diabetics without retinopathy. Although the mean value for vitreous fluorescein was significantly higher in diabetics with retinopathy compared to normals, several of the diabetics with retinopathy had values in the normal range. These results differ from those previously reported in the literature. However, our studies took into consideration several factors not considered by other investigators, such as ocular pigmentation, choroidal fluorescence, slit width, and vitreous changes, that may have significant effects on the fluorophotometry values.

Adolescent↗
PubMed1983

Quantitative endothelial biomicroscopy.

Twenty patients were evaluated by quantitative endothelial biomicroscopy and the resulting endothelial cell densities compared with those from a specular microscope. Estimated cell densities by this technique, when compared with the specular microscope, demonstrated a Pearson correlation coefficient of +0.977, an average error of -7% and an absolute error of 12%. There were no errors greater than 26% except for one extremely low cell density of 318 cells/mm2 for which the estimate was 476 cells/mm2. This rapid, inexpensive technique requires counting the number of endothelial cells seen across the horizontal diameter of the 0.2-mm projected spot beam of a standard biomicroscope. From this count and the known spot size the endothelial cell density may be accurately calculated. A simplified four-step technique for performing specular microscopy using only the standard biomicroscope and a method for accurately measuring the size of the projected slit lamp spot beam are explained.

Adult↗
PubMed1982

The influence of vitreous change on vitreous fluorophotometry.

Thirteen patients with retinitis pigmentosa were graded in terms of vitreous change and compared by vitreous fluorophotometry to an equal number of normal patients. A highly significant difference was found between groups. A high correlation was also noted between severity of vitreous change and midvitreous fluorophotometry values. Certain types of vitreous detachments appear to produce a characteristic "cancer hump" in the resultant data. A possible explanation for the increased values is discussed.

Adult↗
PubMed1981

Vitreous fluorophotometry: identification of sources of variability.

Slit-lamp vitreous fluorophotometry (VF) has been used by several investigators to document the early breakdown of the blood-ocular barrier. After an injection of fluorescein, levels of fluorescein in the vitreous humor are reported to be elevated in diabetic patients compared with controls even when there is no retinal pathologic condition discernible by angiography or ophthalmoscopy. We have examined the technique of VF in normal persons and have identified several potential sources of error in the determination of vitreous fluorescein levels. Fluorescein in the choroidal circulation significantly influences VF readings taken at the retinal surface and in the posterior vitreous. This effect is modulated by ocular pigmentation, with heavy pigmentation of dark-eyed normals more effectively screening out choroidal fluorescence than the light pigmentation of blue-eyed subjects. Influence of choroidal fluorescein extends toward the midvitreous, and the range of influence is directly related to the slit width of the exciting light. At narrow slit widths the effect is diminished but can never be completely eliminated. Blood fluorescein levels decrease with time, and since choroidal fluorescein contributes to VF values, the time after injection that VF reading are taken is a critical parameter.

Adult↗
PubMedDate not supplied

A practice pathway for the initial diagnostic evaluation of isolated sixth cranial nerve palsies.

PURPOSE: To define a practice pathway for the evaluation of sixth-nerve palsies (SNPs) and to determine its cost-effectiveness and validity in a retrospective chart review. METHODS: A Medline search of the English-language literature from 1966 to 1995 was performed to define the available clinical evidence and develop the practice pathway. The authors retrospectively reviewed 407 charts with the diagnosis of SNP seen at three centers. Information obtained included: etiologic diagnosis if known; development of new neurologic or ophthalmologic findings; and results and costs of neuroimaging studies, if performed. RESULTS: Of the 407 patients, 98 underwent computed tomography scans and 212 underwent magnetic resonance imaging of the head. Eighty cases were non-isolated, 317 were isolated SNP, and ten could not be classified from chart information. Of the 317 cases of isolated SNP, 49 were classified as traumatic; 5, congenital; 158, vasculopathic; 63, nonvasculopathic; and 42, progressive or unresolved. Following the recommendations of the practice pathway, the 158 patients classified as having vasculopathic SNP would not have undergone neuroimaging studies, realizing a savings of $100,000 in this study population of 407 patients. CONCLUSION: The recommendations of the practice pathway are supported by review of the literature and the retrospective review of these cases. However, a prospective study with a matched control group is needed to demonstrate regional and specialty-specific variations in care and to strengthen the clinical certainty of the pathway recommendations.

Abducens Nerve↗
PubMedDate not supplied

Pediatric ocular trauma: a retrospective survey.

A retrospective, cross-sectional survey was conducted of all pediatric trauma cases seen by the ophthalmology department at our institution from January 1986 to December 1991. The study included 504 patients who were 15 years old or younger. The purpose of this study was to determine risk factors for ocular injury, especially injury resulting in severe visual impairment, and to identify trends and preventable causes. Our results were consistent with the findings of other similar studies: male patients predominated, penetrating injuries resulted in poor visual outcomes, and many of the causes of severe visual deficit were preventable with more adequate adult supervision.

Adolescent↗
PubMedDate not supplied

Stability of refraction during two years after myopic epikeratoplasty.

A series of 54 consecutive myopic epikeratoplasty procedures was performed by three surgeons between November 1986 and August 1987. To evaluate the stability of the myopic epikeratoplasty procedure, this study was limited to the 33 eyes that had data 24 months after surgery. One year after surgery, 68% (19/28 eyes) had 20/40 or better uncorrected visual acuity and after two years, 57% (17/30 eyes) had 20/40 or better uncorrected visual acuity. Significant loss of surgical effect (increasing myopia) did not occur during the first six postoperative months (r = 0.09, P = NS). This was due to the large amount of variability in spherical equivalent refraction during this interval. However significant regression was detected between 6 and 12 months after surgery (r = 0.27, F = 4.74, P = 0.03). Even though there was further reduction in variability from 12 to 24 months, significant regression was not found (r = 0.07, P = NS). This suggests stabilization of refraction by approximately 12 months for this population.

Adolescent↗