Primary Open-angle Glaucoma Alters Retinal Recovery from a Thiobarbiturate: Spatial Frequency Dependence

Ofri, Ron; Dawson, William W.; Foli, K; Gelatt, Kirk N.

doi:10.1006/exer.1993.1061

Cited by 13 publications

(12 citation statements)

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“…However, the spatial frequency dependence of the phenomenon is a complex topic which cannot be fully discussed in one paper, and is therefore presented elsewhere. 34 Our findings raise three major questions. Firstly, why is the retinal reaction of glaucomatous dogs to thiamylal, or to its consequences or products, different from that of normal dogs?…”

Section: Re-injection Experimentsmentioning

confidence: 91%

Chronic ocular hypertension alters local retinal responsiveness.

Ofri

Dawson

Foli

et al. 1993

British Journal of Ophthalmology

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Electrophysiological responses of the retina and visual cortex to a series of grating stimuli (6-768 minutes of arc) were recorded in seven sessions using normal beagles, 21 sessions using beagles afflicted with inherited ocular hypertension, and 12 sessions using rhesus monkeys. A 150 field centred around the animal's area centralis or fovea was used to stimulate the central retina. A 30°field, centred on the same spot, was then used to stimulate the larger area. Two recording series were completed on each animal, with both field sizes presented in each recording session. The first recording took place 30 minutes after and the second 2 hours after the injection of thiamylal sodium. Only the signals from the toroidal 150 of the retina of the hypertensive dogs were remarkably larger during the second recording (p=0001). No significant differences were found between the two recordings from the retinas of normal dogs or monkeys, nor were there any significant differences between the two recordings from above the cortex in any group. Several hypotheses are proposed to explain the basis for the interaction of thiamylal with the more peripheral retinal function in clinically glaucomatous dogs. (BrJ Ophthalmol 1993; 77: 502-508) Thiamylal sodium is the thiobarbiturate analogue of secobarbitone. It is an ultra short acting drug, commonly used for induction of general anaesthesia for several short term veterinary surgical procedures. In the dog the drug is metabolised rapidly by the liver,' and has no apparent cumulative effect.23 The duration of anaesthesia in the dog is 10-45 minutes,2 with complete recovery after 113 minutes.3 In mixed breed dogs, disposition of thiamylal is characterised by a rapid distribution phase (half life 38-9 minutes) and an elimination phase with a half life of 666 minutes.4 The total plasma clearance of the drug in dogs is 3-21 ml/min/kg. 18 Despite this wealth of information on the multifactorial effect of anaesthetic drugs and increased IOP on visual electrophysiology, we find no information on the interactions between anaesthesia and OHT in the glaucomatous retina. This is surprising, considering the fact that ERG recordings are used in many institutions to diagnose and monitor the progress of glaucoma in non-verbal patients such as children, mentally handicapped people, and animals.'9-22 They may be used to diagnose glaucoma at early stages, before the appearance of funduscopic changes and visual field losses.'ll22 Frequently at this stage the visual deficits are not entirely diffuse, with the greatest losses in the more peripheral, paracentral regions of the visual field. 19 21 23 We report on interactions between thiamylal and different retinal regions of normal and ocular hypertensive dogs. Materials and methods EXPERIMENTAL ANIMALSSeventeen beagle dogs and seven rhesus monkeys (Macaca mulatta) were used in the study. Of the 17 dogs, 13 were hypertensive and four were normal. Some ofthe animals were used for more than one recording session. In such cases, the minimum inter...

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Section: Re-injection Experimentsmentioning

confidence: 91%

Chronic ocular hypertension alters local retinal responsiveness.

Ofri

Dawson

Foli

et al. 1993

British Journal of Ophthalmology

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“…Statistical analysis was performed using the SAS computer program for performing multiple comparison tests as well as Student t ‐tests 31 . Student t ‐tests and anova linear models were used to evaluate repeated measurements.…”

Section: Methodsmentioning

confidence: 99%

Progressive changes in ophthalmic blood velocities in Beagles with primary open angle glaucoma

Gelatt

Miyabayashi

Gelatt-Nicholson

et al. 2003

Veterinary Ophthalmology

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“…104 This theory provides a pathogenetic mechanism for NTG in people and could explain retinal changes discovered with pERG before the onset of clinical signs in beagles. 9,10 Color Doppler imaging in glaucomatous beagles has shown decreased blood velocities and increased pulsatility and resistive indexes in orbital and ocular arteries compared with normal beagles. Retinal artery blood flow velocities were not different in the two groups.…”

Section: Vascular Theorymentioning

confidence: 98%

“…[3][4][5] IOP values in humans are not considered sensitive or specific to make a diagnosis or suggest prognosis, 6 because IOP can be normal in patients affected with normotensive glaucoma (NTG). 7 Unlike in people, increased IOP has historically been a requirement for the diagnosis of clinical glaucoma in dogs, 8 despite pattern-electroretinography (pERG) changes and posterior-segment blood flow abnormalities having been reported before the onset of clinical signs of primary open-angle glaucoma (POAG) in dogs, [9][10][11] suggesting that pathologic changes in the retina can occur before any increase in IOP. Furthermore, glaucoma is a progressive disease in humans and in dogs even with a controlled normalized IOP, suggesting that additional pathophysiologic mechanisms must be involved.…”

mentioning

confidence: 98%

Definition, Classification, and Pathophysiology of Canine Glaucoma

Pizzirani

2015

Veterinary Clinics of North America: Small Animal Practice

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Primary Open-angle Glaucoma Alters Retinal Recovery from a Thiobarbiturate: Spatial Frequency Dependence

Cited by 13 publications

References 0 publications

Chronic ocular hypertension alters local retinal responsiveness.

Chronic ocular hypertension alters local retinal responsiveness.

Progressive changes in ophthalmic blood velocities in Beagles with primary open angle glaucoma

Definition, Classification, and Pathophysiology of Canine Glaucoma

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