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Biomedical subjects

T H Mader

Publications and source records attributed to T H Mader.

At least 37 records · Page 2Linked to original sources
PubMed1993

Ocular and ocular adnexal injuries treated by United States military ophthalmologists during Operations Desert Shield and Desert Storm.

BACKGROUND: Ocular and ocular adnexal injuries, both combat-related and accidental, are common during wartime. In a combat setting, the eye is particularly vulnerable to serious injury from tiny flying particles that might minimally affect other parts of the body. The purpose of this study is to examine the incidence of serious ocular and ocular adnexal injuries that occurred during Operations Desert Shield and Desert Storm. METHODS: The authors retrospectively reviewed serious ocular and ocular adnexal injuries treated by United States Army and Navy ophthalmologists that occurred during Operations Desert Shield and Desert Storm. Only those injuries that resulted in, or would have resulted in, hospital admission because of the ocular or ocular adnexal injury alone are presented. RESULTS: During Desert Shield, 20 patients (23 eyes) suffered serious ocular or ocular adnexal injuries compared with 160 patients (198 eyes) in Desert Storm. During Desert Storm, 78% of all serious injuries were caused by blast fragmentation from munitions. More than one third of the 98 globe lacerations reported in this article were 10 mm or less in size. Of 35 enucleations performed during Desert Storm, 94% were the result of munitions fragments. CONCLUSIONS: During Operation Desert Storm, fragmentation wounds from munitions were the most common cause of ocular and ocular adnexal morbidity. The authors' findings indicate that polycarbonate ballistic protective eyewear could have prevented many of the ocular injuries that they report.

Adolescent↗
PubMed1993

Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty.

BACKGROUND/PURPOSE: Selective removal of interrupted sutures and adjustment of a running suture can minimize astigmatism after penetrating keratoplasty, but the long-term effects of early suture manipulations remain largely unknown. The authors tested the hypothesis that the cornea becomes "fixed" more than 1 year after keratoplasty so that desirable refractive results will remain when all sutures are eventually removed. METHODS: The authors reviewed retrospectively the changes in astigmatism that occurred when all remaining sutures were removed from 162 eyes 1 to 6 years after penetrating keratoplasty. Single-running sutures were used in 130 eyes, double-running sutures in 20 eyes, and a combination of interrupted and running sutures in 12 eyes. RESULTS: Removal of single-running sutures caused an average decrease in astigmatism of 0.52 diopters (D) from 6.10 +/- 4.41 D to 5.57 +/- 3.14 D. However, the astigmatism in 62% of eyes changed 2 or more D (range, 11.94 to -17.87 D), and the range changed more than 20 degrees in 55% of eyes. The average vectorial change was 6.5 +/- 4.3 D (range, 0.59 to 19.8 D). There was no decrease in the amount of astigmatic change with increasing time between surgery and suture removal. Graft size and diagnosis had no effect on the amount of astigmatic change. Astigmatic errors became stable, with less than 1 D of change between successive examinations within 6 months after suture removal. Similar results were obtained for eyes with double-running and interrupted-running sutures. CONCLUSIONS: Corneal astigmatism may change unpredictably and by large amounts when all remaining sutures are removed 1 to 6 years after penetrating keratoplasty.

Astigmatism↗
PubMed1993

Cerebral blood velocity and other cardiovascular responses to 2 days of head-down tilt.

Spaceflight induces a cephalad redistribution of fluid volume and blood flow within the human body, and space motion sickness, which is a problem during the first few days of spaceflight, could be related to these changes in fluid status and in blood flow of the cerebrum and vestibular system. To evaluate possible changes in cerebral blood flow during simulated weightlessness, we measured blood velocity in the middle cerebral artery (MCA) along with retinal vascular diameters, intraocular pressure, impedance cardiography, and sphygmomanometry on nine men (26.2 +/- 6.6 yr) morning and evening for 2 days during continuous 10 degrees head-down tilt (HDT). When subjects went from seated to head-down bed rest, their heart rate and retinal diameters decreased, and intraocular pressures increased. After 48 h of HDT, blood flow velocity in the MCA was decreased and thoracic impedance was increased, indicating less fluid in the thorax. Percent changes in blood flow velocities in the MCA after 48 h of HDT were inversely correlated with percent changes in retinal vascular diameters. Blood flow velocities in the MCA were inversely correlated (intersubject) with arterial pressures and retinal vascular diameters. Heart rate, stroke volume, cardiac output, systolic arterial pressure, and at times pulse pressure and blood flow velocities in the MCA were greater in the evening. Total peripheral resistance was higher in the morning. Although cerebral blood velocity is reduced after subjects are head down for 2 days, the inverse relationship with retinal vessel diameters, which have control analogous to that of cerebral vessels, indicates cerebral blood flow is not reduced.

Adult↗
PubMed1992

Viral keratitis.

Viruses that affect the cornea produce changes that range from benign, self-limited conjunctivitis to sight-threatening scarring and vascularization of the cornea. In this article, the forms of viral keratitis most commonly encountered by the clinician are reviewed. The epidemiology, clinical presentation, and treatment of infection by Herpes simplex virus, varicella zoster virus, and the adenoviruses are discussed. Also included are other viral infections of the cornea.

Adenoviridae Infections↗
PubMed1992

Corneal transplantation in a patient with congenital sensory neuropathy.

We describe penetrating keratoplasty for corneal scarring in a patient with congenital sensory neuropathy and repeated self-mutilation. This patient underwent a successful penetrating keratoplasty but suffered a series of postoperative complications necessitating three repeat grafts. Some of these complications were attributable to decreased corneal sensation while others were caused by self-mutilation. Since his last penetrating keratoplasty 4 years ago, this patient has had functional visual acuity.

Child↗
PubMed1991

Gentamicin resistance in staphylococcal corneal ulcers.

Gentamicin sulfate is frequently included in the initial treatment of suspected bacterial keratitis. We present the gentamicin susceptibility test results for coagulase-negative staphylococci and Staphylococcus aureus isolated from corneal ulcers in nine patients. All were resistant to gentamicin by standard disk diffusion techniques. The minimum inhibitory concentrations were very high, some exceeding the concentration normally achieved by frequent topical application of antibiotics. Clinicians should be aware that strains of staphylococci extremely resistant to gentamicin may cause keratitis. An antibiotic with broad activity against Gram-positive organisms, such as a cephalosporin or vancomycin, should be included as part of the initial therapy for corneal ulcers that might be caused by staphylococci.

Contact Lenses↗
PubMed1990

An automated method of quantifying retinal vascular responses during exposure to novel environmental conditions.

The width of retinal arteries and veins was measured by digital image analysis using an automated vessel-tracking software program. Mean coefficients of variations in vessel width of less than 3% were easily achieved from digitized 35-mm retinal photographs taken with a table-top or hand-held fundus camera. Retinal images were analyzed from seven subjects exposed to sea level or altitudes equivalent to 10,000 (3048 m), 17,500 (5334 m), and 25,000 (7620 m) ft and nine subjects exposed to sea level and 14,110 ft (4300 m). At each altitude, retinal veins dilated more than did arteries (5 +/- 1 versus 0 +/- 1% at 10,000 ft and 28 +/- 9% versus 9 +/- 2% at 25,000 ft; veins versus arteries, respectively). However, widths of retinal arteries and veins were reduced in nine subjects tested after 15 minutes, 24 hours, and 48 hours of 10 degrees head-down tilt; and values varied inversely with intraocular pressures (IOP). Hand-held retinal fundus photography and digital image analysis were found to provide a sensitive and objective method for detecting and quantifying retinal vascular responses in humans exposed to novel environments.

Adolescent↗
PubMed1990

Spontaneous bleeding from a normal-appearing iris: an unusual cause of atypical amaurosis fugax.

Amaurosis fugax, or fleeting loss of vision, is often attributed to embolic retinovascular disease. In this setting, there is appropriate concern for associated cerebrovascular complications. Extensive and expensive vascular evaluation may be indicated. Less often, local ocular abnormalities may mimic embolic visual loss. We describe a case of sudden, transient, monocular visual loss in a 67-year-old woman caused by Valsalva-induced intraocular bleeding from a seemingly normal iris.

Aged↗
PubMed1990

Intraocular pressure, retinal vascular, and visual acuity changes during 48 hours of 10 degrees head-down tilt.

Intraocular pressures, retinal vascular diameters, and visual acuities of nine men (ages 19-29), were repeatedly measured while the subjects were tilted 10 degrees head-down for 48 h and while they were seated before (baseline), and after the tilt. An immediate increase in intraocular pressure, measured by pneumatonometer (4.7 +/- 0.6 mm Hg, p less than 0.001) was recorded when subjects assumed the head-down position, and diurnal variations in intraocular pressures were observed for the 48 h. The initial and final head-down intraocular pressures were not significantly different (18.9 +/- 1.2 mm Hg vs. 17.9 +/- 1.4 mm Hg, respectively). However, when subjects resumed the sitting position, intraocular pressures fell below the initial sitting values (14.2 +/- 0.9 pre vs. 11.2 +/- 0.5 post, p less than 0.04). Computer image analysis of the retinal vasculature detected a 6% and 2% reduction in the caliber of arteries and veins, respectively, as compared with sitting baseline values. No changes in visual acuity were documented during the 48 h of head-down tilt. Our data suggest that the choroidal blood reservoir increases in volume over 48 h at continuous head-down position with a compensatory decrease in aqueous volume. These findings may explain intraocular pressure changes noted in astronauts during previous space missions and in studies associated with change in body position.

Adult↗
PubMed1988

Effect of eye color on heart rate response to intramuscular administration of atropine.

Melanin has been previously shown to modify the mydriatic response to atropine instillation. Skin and iris pigmentation has also been shown to modify aspects of the heart rate response to injected atropine, although these observations have been generally overlooked. In this study, 20 healthy non-smoker male subjects, ages 20-30 years, were injected by two different automatic injector devices and the mydriatic and heart rate responses in the first 90 min were reported. The group included 8 brown-eyed, 4 hazel-eyed, and 8 blue-eyed subjects. Although there were differences in the rate of atropine delivery between the two injection devices, the heart rate responses were independently modified by eye color to a magnitude of difference as great as the differences between injectors. Subjects with more pigmented irides (brown-eyed) showed a more rapid rise in heart rate compared to less pigmented irides (hazel-eyed and blue-eyed subjects). Following injection by the device with a slower atropine absorption rate, these differences were particularly enhanced and an abbreviated bradycardic phase of the heart rate response was observed for the brown-eyed subjects. This observation confirms earlier reports and suggests the possibility of an interference by melanin (in the iris or elsewhere) in atropine accessibility to selected muscarinic target sites.

Adult↗
PubMed1987

Intraocular lenses in aviators: a review of the U.S. Army experience.

Intraocular lenses are known to be efficacious in the correction of aphakia, but their suitability and durability in Army aviators has not been previously evaluated. Eight experienced pilots (preoperative flight time average: 7,660 hours), who had intraocular lens implants following removal of cataractus lenses, were studied. All had returned to flight duty, seven as pilots, with a total of 2,700 hours postoperative flight time accumulated. All were very pleased with the surgery and with the effectiveness of their lenses. Minor problems included: halos around lights in low illumination (5/8 pilots), erythropsia (2/8), and difficulties with a fixed focal length (2/8). Two aviators reported significant visual problems: complications associated with a platinum loop iris supported intraocular lens, and discomfort and glare stemming from traumatic corneal scarring. A detailed ophthalmological examination revealed abnormalities (5/8 pilots), but none which would be directly attributed to flying. Modern intraocular lenses appear to be an acceptable means of correcting aphakia in Army aviators.

Adult↗
PubMed1987

Conjunctival oxygen tension at high altitude.

Transconjunctival oxygen tension (PcjO2) was studied using a hypobaric chamber and during mountaineering excursions. Measurements obtained during acute chamber exposures (15-20 min) at sea level, 1829 m (6,000 ft), 3048 m (10,000 ft), 4267 m (14,000 ft) and return to sea level were (means +/- SEM): 60.1 +/- 2.7, 49.1 +/- 1.8, 38.3 +/- 2.4, 27.4 +/- 1.5, and 61.1 +/- 2.8 mm Hg, respectively (n = 13). The ratio of PcjO2 to arterial blood oxygen tension (PaO2) did not change in a consistent manner between sea level and 4267 m; PcjO2 was 74 +/- 6.9% of PaO2. The 16 subjects participating in the mountaineering phase of the study revealed similar means at sea level and 1829 m (57.4 +/- 2.4 and 46.3 +/- 1.9 mm Hg respectively), but a smaller decrement was observed at 3048 m (43.0 +/- 1.6 mm Hg). The difference between mountain and chamber values may be accounted for by a partial acclimatization to altitude brought about by longer exposure on the mountain excursions. A comparison between PcjO2 and transcutaneous oxygen tension during the chamber study suggests that a greater precision and sensitivity is obtained with measurement of oxygen tension at the conjunctival site. PcjO2 measurement is a non-invasive reflection of PaO2 which is suitable for continuous monitoring during hypoxia studies.

Adult↗