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Biomedical subjects

Alison Y Firth

Publications and source records attributed to Alison Y Firth.

6 recordsLinked to original sources
PubMed2006

Visual side-effects from transdermal scopolamine (hyoscine).

Transdermal scopolamine may be used to reduce drooling in children with disabilities. Side-effects include dilated pupils and a reduction in the near point of accommodation (the closest point at which clear vision is possible). Two male children with epilepsy, one with spinal dysraphism (aged 7y 6mo) and one with cerebral palsy (aged 5y 8mo), who have undergone treatment for drooling with transdermal scopolamine are described. Near visual acuity was reduced, and both children showed dilated pupils with reduced or no response to light. These responses became normal on cessation of the scopolamine patch. As the effect of this drug may be cumulative, and many patients are unable to communicate difficulties, clinicians need to be aware of these possible side-effects.

Administration, Cutaneous↗
PubMed2006

Is the Cardiff Acuity Test effective in detecting refractive errors in children?

PURPOSE: Refractive error is a common cause of reduced visual acuity in young children. This reduced vision should be detected as soon as possible to avoid development of squinting and educational disadvantage. The Bailey-Lovie Chart (BLC) is based on the logarithm of the minimal angle of resolution (logarithm of the minimum angle of resolution logMAR) and is widely accepted as the clinical standard for visual acuity testing. However, most young children are unable to perform this test because of its symbolic level. The Cardiff Acuity Test (CAT) overcomes these symbolic demands and is the test of choice for young children in most U.K. orthoptic departments. The purpose of this study is to determine how effective the CAT is in detecting reduced visual acuity caused by refractive error in young children. METHODS: Visual acuity of the right eye was tested without spectacles in 68 children (mean age, 74 +/- 14.6 months) with known bilateral symmetric refractive error (40 male) using the CAT and the BLC. Subjects were randomized to receive CAT or BLC first in a single assessment using a crossover design. Subjects scoring 0.2 logMAR or better were classified as having passed the test. RESULTS: The CAT correctly identified reduced vision caused by uncorrected refractive error in 25% (17) of the children compared with a detection rate of 97% (66) for the BLC using the specified pass criteria. Further analysis with an adjusted cut point for the CAT (0.0 logMAR), as used to identify abnormal vision in clinical practice, identified a detection rate of 56% (38 of the children). CONCLUSIONS: This study casts doubt on the current clinical practice used in orthoptic clinics by suggesting that assessment of visual acuity with the CAT alone will underdiagnose reduced acuity caused by refractive errors.

Child, Preschool↗
PubMed2005

Heroin and diplopia.

AIMS: To describe the eye misalignments that occur during heroin use and heroin detoxification and to give an overview of the management of persisting diplopia (double vision) which results from eye misalignment. METHODS: A literature review using Medline and the search terms strabismus, heroin and substance withdrawal syndrome is presented. General management of cases presenting to the ophthalmologist and orthoptist with acute acquired concomitant esotropia is described. FINDINGS: A tendency towards a divergence of the visual axes appears to be present in heroin users, although when present it may not always lead to diplopia. Following detoxification intermittent esotropia or constant esotropia (convergence of the visual axes) can occur; if intermittent the angle tends to be small and diplopia present when viewing distance objects. Occlusion of one eye to eliminate the second image could encourage the development of a constant deviation. The deviation is not caused by a cranial nerve palsy. Constant deviations of this type are classified as 'acute acquired concomitant esotropia'. Relief from the diplopia may be gained by prismatic correction, and the deviation may then resolve spontaneously. Botulinum toxin or surgical intervention may be necessary in cases that do not resolve. CONCLUSIONS: Heroin use may lead to intermittent or constant exotropia and withdrawal may result in intermittent or constant esotropia. Awareness of the mechanism causing this may avoid referral to other specialties (e.g. neurology) and awareness of treatment modalities could encourage patients to seek appropriate help for relief of symptoms.

Acute Disease↗
PubMed2004

Binocular sighting ocular dominance changes with different angles of horizontal gaze.

BACKGROUND AND PURPOSE: Ocular dominance testing is generally carried out in the primary position. A change of eye dominance when viewing in the contralateral field of horizontal gaze has recently been reported. The purpose of this study was to determine whether this occurs with other tests of eye dominance. METHODS: Ten right handed females (mean age 21.6 +/-0.8 years) with normal binocular single vision and right eye ocular dominance in primary position were tested for ocular dominance on three tests (pointing, hole-in-card, Miles ABC) performed fixing at positions at 10 degree intervals from 40 degrees left gaze to 40 degrees right gaze, with the head stationary. Four trials were undertaken in each position for each test. RESULTS: Not all participants showed a change in dominance in left gaze on all of the tests. However, a change did occur at a median of 30 degrees for the hole- in-card and Miles ABC tests and 20 degrees for the pointing test. Examining the position of change across the 3 tests, a borderline "statistically significant" difference occurred (p=0.055, Friedman test). A "statistically significant" difference was shown between the hole-in-card and pointing tests (p=0.041, Wilcoxon signed ranks test). For pointing versus Miles ABC, p=0.084; and hole-in-card versus Miles ABC, p=0.705. CONCLUSIONS: A change in eye dominance occurs when viewing in the contralateral field. Differences may exist in the angle at which this occurs due to the different conditions of the various tests for ocular dominance.

Adult↗
PubMed2003

Vertical vergence adaptation does improve with practice.

PURPOSE: To investigate the effect of repeated testing on adaptation to a 2 Delta vertical prism in subjects with normal binocular single vision. METHODS: Subjects were required to have good visual acuity and normal binocular single vision. The residual deviation was measured after a 1-min period of adaptation to a 2 Delta vertical prism using a modified Maddox Rod technique. This measurement was repeated 10 times, with a 5-min rest period between each trial. RESULTS: For eight young adult subjects, the mean residual deviation at 1 min reduced with consecutive trials, and this effect was statistically significant (p < 0.0001). No significant correlation was present between the amplitude of vertical vergence and the increase in adaptation with repeated demand. CONCLUSIONS: A practice effect for vertical vergence adaptation appears to be present in young adult subjects with normal binocular single vision.

Adaptation, Ocular↗