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Biomedical subjects

L M Parver

Publications and source records attributed to L M Parver.

At least 19 recordsLinked to original sources
PubMed2000

Photochemical injury to the foveomacula of the monkey eye following argon blue-green panretinal photocoagulation.

PURPOSE: Visual loss following panretinal photocoagulation was found in the Diabetic Retinopathy and the Early Treatment Diabetic Retinopathy Studies. This study was designed to test the hypothesis that light scattered in the monkey eye during a procedure designed to mimic a clinical panretinal photocoagulation (PRP) can produce a photochemical injury to the foveomacula. METHODS: Ten eyes of 5 adult cynomologous monkeys underwent a PRP using an argon blue-green laser. Three eyes in 2 monkeys underwent a sham PRP, and an additional eye had a PRP with blue filtered slit-lamp illumination. The animals had baseline fundus photographs and fluorescein angiograms that were repeated 24 hours after the experimental procedure. Forty-eight hours after the experimental procedure, the eyes were removed and processed for light and electron microscopy. RESULTS: There were no observable changes in the macula on fundus photography or fluorescein angiography 24 hours following PRP. Light and electron microscopy demonstrated changes in the retinal pigment epithelium and the outer photoreceptors, which were confined to the foveola. The control eyes showed no apparent effect from the slit lamp illumination used during the PRP. CONCLUSIONS: The presence of histologic evidence of retinal injury in the foveomacula of the monkey eye after a procedure designed to mimic clinical PRP supports the hypothesis that photochemical retinal damage in the foveola may be associated with this procedure.

Animals↗
PubMed1993

Infectious endophthalmitis after penetrating injuries with retained intraocular foreign bodies. National Eye Trauma System.

PURPOSE: To determine the risk factors and prognostic indicators of infectious endophthalmitis in eyes with penetrating injury and retained intraocular foreign body. METHODS: From the National Eye Trauma System (NETS) Registry, 492 eyes with intraocular foreign bodies were reviewed for signs of infectious endophthalmitis. RESULTS: Thirty-four eyes (6.9%) with intraocular foreign bodies had evidence of infectious endophthalmitis, and 31 (91.2%) of those eyes had signs of infection at the time of removal of the intraocular foreign body. The majority of eyes with an intraocular foreign body with or without endophthalmitis were in patients between 10 and 39 years of age, but the risk of endophthalmitis developing increased with age, especially in patients 50 years of age or older with delayed primary repair (P = 0.005). Endophthalmitis was more likely to develop in eyes with home or occupational injuries (33/358, 9.2%) than in those with injuries from other settings (1/128, 0.8%; P = 0.001). Infectious endophthalmitis was much less likely to develop in eyes with primary repair within 24 hours of the injury (10/287 = 3.5%) than in eyes with primary repair more than 24 hours after the injury (22/164, 13.4%; P < 0.0001). Bacilli or staphylococci were isolated in 21 (95%) of 22 eyes with positive cultures. Visual prognosis was reasonably good with 15 (58%) of 26 eyes attaining a visual acuity of 20/200 or better. CONCLUSIONS: Removal of a retained intraocular foreign body within 24 hours of injury markedly reduces the risk of infectious endophthalmitis developing. Older persons are at high risk for endophthalmitis developing after retaining an intraocular foreign body when there is delayed surgical repair.

Adolescent↗
PubMed1992

Penetration eye injuries in the workplace. The National Eye Trauma System Registry.

Occupational eye injuries are common and preventable. Between 1985 and 1991, there were 635 work-related penetrating eye injuries among the 2939 cases (22%) reported to the National Eye Trauma System Registry by 48 collaborating centers in 28 states and Washington, DC. The median age of the injured workers was 30 years; 75% were younger than 40 years; and 97% were male. The commonest causes of injuries were projectiles (457 cases), sharp objects (166 cases), blunt objects (60 cases), and blasts (22 cases); these terms are not mutually exclusive. Specific objects causing injuries included nails, wire, screwdrivers, and other hand tools. There was evidence of alcohol use by at least 2% of the injured workers. When they were injured, 6% of the workers were wearing safety glasses; 3% were wearing nonsafety eyewear. Posterior segment trauma, which occurred in 63% of the cases, included vitreous hemorrhage (42%), intraocular foreign bodies (35%), and retinal detachment (10%). Hyphema occurred in 35% and traumatic cataract in 32% of the cases. Initial visual acuity after injury was hand motion or worse in 43% of the cases. National Eye Trauma System Registry data are useful to identify strategies to prevent occupational eye injuries such as wider use of safety glasses and improvement in engineering controls.

Accidents, Occupational↗
PubMed1992

Penetrating eye injuries related to assault. The National Eye Trauma System Registry.

From 1985 to 1991, 648 cases of assault-related penetrating ocular injury were reported to the National Eye Trauma System Registry. We examined the circumstances surrounding and initial clinical findings related to this case series of injuries. Eighty-three percent of the patients were male. The median age was 28 years; 77% were younger than age 40 years, and 17% were younger than age 20 years. The ocular injury was part of multiple trauma in 34% of cases. There was evidence of alcohol and illicit drug use by at least 48% and 6% of the injured persons, respectively. Seventeen percent of the injuries involved powder or nonpowder firearms. Fists, glass fragments, metal rods or pipes, knives, and scissors were among the other objects causing injury. Posterior segment trauma, which occurred in 70% of cases, included vitreous hemorrhage (40% of cases), retinal detachment (11%), presence of intraocular foreign bodies (6%), and optic nerve damage (4%). The initial visual acuity after injury was hand motion or worse in 74% of the cases. Strategies to prevent such injuries focus on the origins of violence in general and are more difficult to devise than strategies to prevent eye injuries in other settings. Public health efforts to reduce the use of alcohol, drugs, and firearms may reduce the incidence of these injuries.

Adolescent↗
PubMed1992

Correlation of full-thickness corneal wound length with endothelial cell loss.

We studied 12 patients who had sustained penetrating corneal lacerations with corneal wound lengths ranging from 1 to 9 mm to determine whether wound size was directly proportional to endothelial cell loss 3 or more months after injury. Endothelial cell counts in the uninjured eye averaged 2973 +/- 330 cells/mm2 (range, 2500 to 3700). In the injured eye, near the wound (less than 2 mm from the wound), the cell counts averaged 1260 +/- 590 cells/mm2 (range, 575 to 2500); away from the wound, where cells appeared healthiest, counts averaged 1619 +/- 544 cells/mm2 (range, 850 to 2750). The average total cell loss near the wound was 1713 +/- 622 cells/mm2 (range, 500 to 2575), vs 1354 +/- 582 cells/mm2 (range, 250 to 2150) away from the wound, compared with the uninjured eye. Cell loss near the wound was not significantly different from that away from the wound. There was a positive correlation between wound length and total cell loss measured both near the wound (r = 0.830) and away from the wound (r = 0.755). Pars plana lensectomy was not associated with detectable additional cell loss. Our results suggest that patients with corneal lacerations sustain significant endothelial cell loss, which correlates closely with wound length, and that patients with larger wounds may be at greater risk for developing corneal decompensation with additional procedures or trauma.

Cell Count↗
PubMed1991

Temperature modulating action of choroidal blood flow.

A major physiologic role for the high flow choroidal vasculature is to help maintain a stable temperature in the macula. The choroidal vasculature modulates tissue temperature in the macula via both active and passive mechanisms. The active mechanisms involve a reflexive increase in choroidal blood flow in response to light. The neuro-anatomical pathways mediating this reflective mechanism have been demonstrated to involve the supra-chiasmatic and the Edinger-Westphal nuclei. The importance of the thermal environment for the retina has been neglected in looking for causes of retinal disease. The observations on the ability of the choroidal circulation to modulate the thermal environment of the macula should excite further study of the role of temperature and the ability of the eye to dissipate light-generated heat on macula disease.

Animals↗
PubMed1990

Determinants of hospital charges and length of stay for ocular trauma.

Ocular trauma is an important cause of blindness and visual impairment in the United States. This study examined the economic effect of ocular trauma by evaluating hospital length of stay and charges for 4406 discharges from Maryland hospitals from 1979 to 1986. Length of stay declined on average 6.1% per year during this period. Length of stay was positively associated with age which could not be accounted for by the severity of the trauma or the presence of secondary trauma diagnoses. Other factors associated with length of stay included race, principal diagnosis, secondary trauma, and characteristics of the hospital. National projections estimate greater than 227,000 hospital days and $175 to $200 million in hospital charges alone are due to ocular injuries every year.

Adolescent↗
PubMed1989

Sensitivity to retinal light damage and surgical blood oxygen levels.

Increased oxygen levels decrease the threshold for photochemical retinal damage. We measured arterial oxygen levels in a group of ophthalmic surgical patients. As expected, levels exceeded unanesthetized measurements by one to two times. Based on experimental data, this could decrease the threshold for light-induced retinal damage during ophthalmic surgery by 40% to 50%. While the clinical implications of light-induced retinal damage in surgical eye patients are unclear, it is prudent to take steps to minimize light exposure during surgery.

Adult↗
PubMed1986

Sympathetic ophthalmia. Immunopathological findings.

Ocular tissue from six patients with a clinical diagnosis of sympathetic ophthalmia (SO) was examined using immunohistochemical techniques. All patients presented with a history of bilateral panuveitis after penetrating ocular injury or multiple intraocular surgeries and clinical features of SO. In four cases, classic histopathological features of SO were observed, including granulomatous uveal tract infiltration and subretinal pigment epithelium (RPE) collections of inflammatory cells (Dalen-Fuchs nodules). Bone marrow derived monocytes were the major cellular components in these granulomas. In two cases, histopathology failed to demonstrate typical Dalen-Fuchs nodules or granulomas in the choroid. However, the choroidal infiltrates were composed primarily of T-helper and B lymphocytes, without macrophages or epithelioid cells. The eyes examined in this report indicate that a varied spectrum of immunopathological and histopathological findings may occur in clinically diagnosed SO.

Adult↗
PubMed1984

Dexamethasone protection against photochemical retinal injury.

Photochemical retinal injury was produced in the foveomacula of the rhesus monkey using the light from an indirect ophthalmoscope. The eyes were examined by both light and electron microscopy. Damage consisted of vacuolization of the retinal pigment epithelium and neurosensory retinal layers. Pretreatment with subcutaneous injection of dexamethasone for 16 weeks prior to light exposure markedly decreased damage to the retinal pigment epithelium, but had no apparent effect on damage to the neurosensory retina in eyes examined 18 hours after exposure. The mechanism responsible for this protective effect is unknown.

Animals↗
PubMed1984

Progressive subretinal fibrosis and uveitis.

Three patients with intraocular inflammation and unusual progressive subretinal lesions are described. This entity is characterised by a chronic vitreous inflammation in association with whitish "fibrotic'-like subretinal lesions which progressively enlarge and coalesce. The patients all developed cystoid macular oedema. The differential diagnosis of this entity is discussed. These patients appear to have a unique and previously undescribed inflammatory disorder. The macular oedema responded to corticosteroid therapy in only one patient, and no therapy appeared to alter the course of the disease. Unlike many other patients with posterior uveitis these did not respond to the retinal S-antigen.

Adolescent↗
PubMed1983

Choroidal blood flow. III. Reflexive control in human eyes.

Choroidal blood flow helps maintain a stable temperature environment for the outer retinal layers, especially in the macular area. Recent studies in monkeys have demonstrated a centrally mediated reflexive mechanism that increases choroidal blood flow in response to light or light-generated heat. This increase in choroidal blood flow can be detected as an elevation in ocular surface temperature. With the use of ocular surface temperature as a semiquantitative index of alterations in choroidal blood flow, the existence of a similar reflex was demonstrated in normal human volunteers.

Blood Circulation↗
PubMed1983

Observations on monkey eyes exposed to light from an operating microscope.

Two cynomolgous monkeys were exposed to the light of an operating microscope. One eye was exposed to the light with the blue end of the spectrum filtered, while the other was exposed to unfiltered light. Neither group of eyes showed ophthalmoscopic evidence of a discrete retinal lesion. The eyes exposed to unfiltered light, however, showed histologic evidence of foveomacular change. The eyes exposed to filtered light showed lesser changes.

Animals↗
PubMed1982

Choroidal blood flow. I. Ocular tissue temperature as a measure of flow.

Temperature measurements were taken from the retina-choroid, scleral surface, or bulbar conjunctiva in cats and monkeys. Decreasing choroidal blood flow by elevating intraocular pressure produced a decrease in ocular tissue temperature. Confirmation of choroidal blood flow changes was obtained by the hydrogen washout technique, an independent measure of blood flow. We conclude that ocular tissue temperature can be used as a semiquantitative index of choroidal blood flow, and, being noninvasive, has potential clinical application.

Animals↗
PubMed1982

Choroidal blood flow II. Reflexive control in the monkey.

Temperature measurements were taken from (1) the retina-choroid in the macula, (2) the scleral surface, or (3) the bulbar conjunctiva of the cynomolgus monkey, while the fellow eye was exposed to a moderate-intensity light source. Light stimulation produced an increase in tissue temperature in the non-light-stimulated eye. The increase in tissue temperature presumably results from a reflexive increase in choroidal blood flow. Hydrogen washout measurements of blood flow in the retina-choroid confirmed this increase in flow. This active mechanism, along with the passive ability of the choroidal circulation to dissipate light-generated heat, may be an important physiologic safeguard in helping to maintain a stable temperature environment for the outer retinal layers in the macula.

Animals↗
PubMed1982

The stabilizing effect of the choroidal circulation on the temperature environment of the macula.

A major physiologic function for the high-flow choroidal circulation is the stabilization of the temperature environment of the retina. This is especially important in the macular region, which lies at the focal point of the eye's optical system. Observations of temperature changes in the macula under varying conditions of ambient illumination and choroidal blood flow have established that the choroidal circulation serves a dual purpose in stabilizing retinal tissue temperature, acting both as a heat source and a heat sink, depending on prevailing tissue temperatures.

Animals↗