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Biomedical subjects

A Y Firth

Publications and source records attributed to A Y Firth.

9 recordsLinked to original sources
PubMed2004

Orthoptic status before and immediately after heroin detoxification.

AIM: To determine whether changes in orthoptic status take place during withdrawal from heroin and/or methadone. METHOD: A prospective study of patients, using a repeated measures design, attending a 5 day naltrexone compressed opiate detoxification programme. RESULTS: 83 patients were seen before detoxification (mean age 27.1 (SD 4.6) years) and 69 after detoxification. The horizontal angle of deviation became less exo/more eso at distance (p<0.001) but no significant change was found at near (p = 0.069). Stereoacuity, visual acuity, and convergence were found to be reduced in the immediate post-detoxification period. Prism fusion range, refractive error, subjective accommodation, and objective accommodation at 33 cm did not reduce but a small decrease was found in objective accommodation at 20 cm. CONCLUSIONS: The eso trend found in these patients may be responsible for the development of acute concomitant esotropia in some patients undergoing heroin detoxification. However, the mechanism for this trend does not appear to be caused by divergence insufficiency or sixth nerve palsy.

Accommodation, Ocular↗
PubMed2001

Heroin withdrawal as a possible cause of acute concomitant esotropia in adults.

PURPOSE: To report the possible effects of heroin withdrawal on binocular vision. METHODS: A case series of patients is presented in whom esotropia developed on cessation of heroin use. RESULTS: In each case the esotropia was concomitant and prismatic correction restored binocular single vision. Intermittent spontaneous control occurred in one patient, the deviation resolved in one and one patient was lost to follow-up. CONCLUSIONS: Heroin withdrawal should be considered as a cause of acute concomitant esotropia. However, an accurate history of other medication is needed to ensure that this is not the cause of decompensation.

Acute Disease↗
PubMed1999

Adie syndrome: evidence for refractive error and accomodative asymmetry as the cause of amblyopia.

PURPOSE: To report objective changes in accommodation in a child with Adie syndrome. METHODS: A child aged 2 years 10 months when initially examined was found to have good visual acuity in both eyes, a low degree of hypermetropia (isometropic), and Adie pupil presumed to be caused by chicken pox that had occurred 2 months earlier. Amblyopia developed but responded well to treatment, which involved correction of the refractive error and occlusion therapy. Objective changes in the refraction of the eye were measured on the Canon R1 autorefractor at 3.8 m and 33 cm. RESULT: The degree of accommodation in the affected eye when both eyes were open was markedly reduced. CONCLUSION: The presence of isometropic hypermetropia, which remains uncorrected when Adie syndrome is present, can lead to the development of amblyopia in a child.

Accommodation, Ocular↗
PubMed1999

The role of vergence adaptation in recovery of binocular single vision (BSV) following sensory strabismus.

Vergence adaptation is an important element of comfortable binocular single vision and probably contributes to the high incidence of orthophoria or small angles of heterophoria in the normal population. Where binocular single vision has been absent for a period of time, restoration of good visual acuity appears to enable the vergence adaptation mechanism to become active again. A case is presented in which a moderate to large angle of deviation rapidly 'disappeared' once good visual acuity was restored and the disparate images could be fused. Known factors concerning vergence adaptation are discussed in relation to such clinical cases.

Adaptation, Ocular↗
PubMed1995

Handedness in strabismics. Etiological implications.

The incidence of non right handedness was found to be significantly higher in a group of 228 strabismics when compared with a control group of neurologically normal non strabismic subjects. The difference was still present after elimination of strabismics with known neurological or general health problems, or who were born prematurely. The strabismics showed no inter group differences in handedness in relation to the type of retinal correspondence present or the ability to achieve normal or abnormal binocular single vision. Evidence is reviewed for the presence of a developmental defect leading to strabismus, and results of this survey support a previously proposed idea that a developmental defect leads to strabismus, the type of which reflects the severity of the defect (although external factors may also be an influence).

Adolescent↗
PubMed1990

Pupillary responses in amblyopia.

Relative afferent pupillary defects (RAPD) were detected in 32.3% of patients with amblyopia by a modification of the swinging flashlight test and the synoptophore. After consideration of various clinical investigations the significant factors identified in patients showing a RAPD were: anisometropia, early age of onset where strabismus was present, level of visual acuity following treatment, longer period of occlusion therapy. These points bear similarities to the results of pattern electroretinograms (PERG) in amblyopes, and the possibility of the causative defect being at ganglion cell level is discussed. The effect of occlusion treatment cannot be predicted from the presence or absence of a RAPD.

Adolescent↗