Arch Ophthalmol Chic
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The mechanism by which optic nerve sheath fenestration relieves papilledema associated with increased intracranial pressure has not been clearly defined. A model was constructed to determine if the induction of fluid flow along the nerve sheath and through the fenestration could account for a reduction in pressure around the optic nerve, as might be expected according to Bernoulli's equation of fluid dynamics. The model states that as the velocity of a fluid increases, the pressure it exerts decreases. ⋯ The reduced intrasheath pressures persisted even when the intracranial pressure was again elevated to pathologic levels as long as active fluid flow continued along the nerve sheaths. Thus, induction of cerebrospinal fluid flow along the optic nerve sheath by fenestration appears to locally reduce the pressure around the optic nerve, in spite of persistently elevated intracranial pressure. This is in accordance with what would be predicted by Bernoulli's equation.
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Arch Ophthalmol Chic · Aug 1990
Topical ultraviolet light-absorbing chromophore protects against experimental photokeratitis.
Ultraviolet radiation may play a causative role in a number of human ocular and dermatologic conditions; reduction of environmental UV light exposure may decrease their incidence. We investigated the effects of two different UV light-absorbing chromophores, octyl methoxycinnamate (Parsol-MCX) and butyl methoxydibenzoylmethane (Parsol-1798) on corneal UV light transmittance, and evaluated topically applied Parsol-MCX for its protective effect against experimental UV light-induced keratitis in New Zealand white rabbits. Both Parsol-1789 (UV-A light absorber) and Parsol-MCX (UV-B light absorber) are well tolerated by New Zealand white rabbit eyes. Pretreatment with a single drop of Parsol-MCX reproducibly protected against UV light-induced keratitis, apparently by absorbing greater than 75% of UV-B (peak wavelength, 308 nm) irradiation.
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Arch Ophthalmol Chic · Aug 1989
New and previously unidentified retinal breaks in eyes with recurrent retinal detachment with proliferative vitreoretinopathy.
The location of retinal breaks found on preoperative examination was studied in 68 eyes of 68 patients with recurrent retinal detachment and proliferative vitreoretinopathy. Twelve eyes had 23 open breaks that were known to exist previously, no open break was detected in 18 eyes, and 72 new or previously unidentified breaks were found in 41 eyes. ⋯ Our results indicate that the retina that borders chorioretinal scars is vulnerable and prone to develop retinal tears secondary to traction from preretinal membranes. The vicinity of cryopexy-induced scars should be closely observed for retinal breaks in cases of recurrent retinal detachment with proliferative vitreoretinopathy.