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Biomedical subjects

M C Flom

Publications and source records attributed to M C Flom.

14 recordsLinked to original sources
PubMed1978

Marijuana, alcohol, and combined drug effects on the time course of glare recovery.

The time course of light adaptation after intense light exposure is significantly delayed by alcohol, marijuana, and a combined dose of alcohol and marijuana. These effects were found in a double blind experiment, using 10 subjects. The experimental treatments were placebo, 0.75 ml/kg of 95% ethanol, 8 and 15 mg of delta9 tetrahydrocannabinol (THC). and 0.75 ml/kg of 95% ethanol together with 15 mg of THC. The marijuana-induced delay in recovery is doserelated. Both drugs produce delayed recovery for at least 2 h after drug ingestion. The combined alcohol and marijuana treatment produces little more than the effect produced by either drug alone, suggesting some antagonism between the drugs--a suggestion supported by a significantly lower blood alcohol level for the alcohol dose when combined with marijuana than when taken alone.

Adaptation, Ocular↗
PubMed1978

Visual acuity at different retinal loci of eccentrically fixating functional amblyopes.

Visual acuity was measured in eccentrically fixating amblyopic subjects to determine the contribution of sensory (inhibitory) and motor (retinal-locus) components of the acuity loss. A unique aspect of this research involved the subjects' use of auditory feedback to control their unsteady and eccentric fixation while responding to flashed (800 msec) or continuously presented targets at various eccentricities in the visual field. All 4 amblyopic eyes had maximum visual acuity at the fovea; from there, the acuity declined approximately symmetrically into the nasal and temporal periphery. Foveal acuity for these amblyopic eyes was depressed from the acuity at the fovea of the normal eye. We conclude that Worth's explanation of eccentric fixation (eccentric fixation develops in an attempt by the amblyopic eye to fixate with a peripheral retinal locus having higher acuity than the fovea) cannot apply to our amblyopes. The acuity losses exhibited by the amblyopic eyes studied have a sensory (inhibition) component and a motor (retinal-locus) component, the sensory component being greater for small degrees of eccentric fixation and the motor component being greater for large amounts of eccentric fixation.

Acoustic Stimulation↗
PubMed1978

Changes in retinal correspondence following surgery for intermittent exotropia.

An intermittent exotrope of 54delta had harmonious anomalous correspondence when squinting and normal correspondence when bifoveally fixating. Measures of the angle of deviation (H) and angle of anomaly (A) were made at the first postoperative dressing 6 hr after surgery (H = 8--14delta esotropia, A = 0--54delta exo) and at several times over a 2.5-mo period during which a second operation was performed. The final result was 3delta of exophoria with normal correspondence when fusing and harmonious anomalous correspondence (A = 3delta exo) when fusion was disrupted. The change in angle of anomaly created by the surgery cannot be explained by changes in fusional vergence. Halldén's "sensory-fusion" mechanism, which is based on diplopia resulting from stimulation of disparate retinal points, is more useful in explaining the obtained results.

Adult↗
PubMed1978

Eccentric fixation in amblyopia: is reduced foveal acuity the cause?

The Worth-Chavasse theory of amblyopia is briefly reviewed with particular attention to Worth's explanation that eccentric fixation develops in an attempt by the amblyopic eye to fixate with an eccentric retinal locus having higher acuity than the fovea. Three experiments are reviewed; these show that of 8 eccentrically fixating amblyopic eyes tested, 7 had foveal acuity that was higher than or equal to the acuity at the eccentric fixation locus. A fourth study is reviewed, however, which reports that 24 of 25 eccentrically fixating amblyopic eyes had highest acuity at the eccentric retinal locus. With only slight reservations, the conclusion from the first 3 experiments that eccentric fixation does not occur to improve acuity appears justified, but the contrary results of the fourth study, in which fixation was not controlled, cannot easily be dismissed. The importance of performing an experiment that accurately measures acuity across the retinas of amblyopic eyes with careful control of fixation and target location is stressed.

Amblyopia↗
PubMed1977

Pupil size after use of marijuana and alcohol.

In an experiment using ten subjects, marijuana produced a dose-related constriction of the pupil at low photopic light levels; alcohol produced no effect on pupil size. The two drugs in combination produced no change in pupil size.

Adult↗
PubMed1977

Monocular central-field occlusion for intractable diplopia.

This report describes several methods of degrading imagery through the central portion of a spectacle lens to provide a cosmetically acceptable means of obtaining single vision in the central field of patients with intractable diplopia. For 2 strabismic patients with annoying diplopia, we applied to 1 spectacle lens a centrally placed disc (about 1 inch diameter) consisting of (1) translucent tap,a (2) a +7 D Fresnel lens,b or (3) stippled, clear lacquer. For 1 patient, the lacquer was the most acceptable; for the other, the tape was best. We present here the case reports for these 2 patients, showing why they preferred different image-degrading methods and how these and other methods of central-field image degrading can be advantageous even when diplopia is present across most of the visual field.

Adolescent↗
PubMed1977

The Humphrey Vision Analyzer tm: reliability and validity of refractive-error measures.

Four subjective measures of the refractive error of 42 eyes (21 patients) were obtained by 2 examiners, one using a Humphrey Vision Analyzer TM and the other using a conventional refractor. Each examiner made 2 separate measures of each subject's refractive error, one without and one with an added cylindrical lens chosen at random from a predetermined set of powers and axes. The order of using the instruments and the added lenses was mixed. Measures of the refractive errors differed with the 2 instruments by approximately the same amount on average as did duplicate measures with either instrument. Refractive-error measures obtained with the 2 instruments are about as valid as they are repeatable.

Adult↗
PubMed1976

Alcohol and marijuana effects on ocular tracking.

Experienced alcohol and marijuana users were instructed to track with their eyes a small spot that moved horizontally back and forth in pendular (sinusoidal) motion across a 7.5-degree field. The frequency of spot oscillation was gradually increased from 0.5 to 3.0 Hz in 40 sec. Eye movement recordings showed the frequency at which smooth tracking and, soon thereafter, saccadic tracking broke down. These smooth and saccadic cutoff frequencies were reduced after administration of alcohol, but not after marijuana or placebo. For low alcohol doses, smooth tracking was impaired and saccadic tracking was unaffected, much like an effect previously reported for barbiturates. Alcohol seems to affect smooth tracking by increasing the central processing time required to generate the appropriate eye movement. It affects saccadic tracking by slightly decreasing saccadic velocity and to a greater extent by increasing latency time, part of which may be devoted to central processing. The site of action of alcohol appears to be central to both the paramedian pontine reticular formation and the flocculus of the cerebellum.

Adult↗
PubMed1975

Alcohol and marijuana effects on static visual acuity.

Static visual acuity was measured at two contrast levels (12 and 49%) in ten subjects in a double blind experiment involving five drug conditions of alcohol and marijuana (0.5 ml and 1.0 ml/kg body weight of 95% ethanol, 8 and 15 mg delta-9-tetrahydrocannabinol (THC), and a placebo). We found no statistically significant change in static visual acuity for any of the dose levels at any of the measurement time up to six hours following drug ingestion; this is sharply contrasted with the marked decrements in acuity which were found in the same subjects under the same drug conditions when the targets were in motion and required corrdinated eye movements for their resolution.

Adolescent↗
PubMed1975

Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon?

Normal pressure within the human eye was reduced after smoking a socially relevant dose of marijuana (12 mg. delta9-9-tetrahydrocannabinol), but only for light to moderate users who experienced a substantial "high" and a state of peaceful relaxation from the experimental dose. Analysis suggests an indirect effect of the drug associated with relaxation-a psychophysiologic state that can be produced by drug and nondrug means.

Adolescent↗