Biomedical subjects

A Jonathan Jackson

Publications and source records attributed to A Jonathan Jackson.

3 recordsLinked to original sources

PubMed2006

Accommodative dysfunction in children with cerebral palsy: a population-based study.

PURPOSE: To determine the prevalence, nature, and degree of accommodative dysfunction among children with different types and severities of cerebral palsy (CP) in Northern Ireland. METHODS: Ninety subjects with CP (aged 4-15 years) were recruited through the Northern Ireland CP Register (NICPR). Modified Nott dynamic retinoscopy was used to measure lag and lead of accommodation at three test distances: 25 cm (4 D), 16.7 cm (6 D), and 10 cm (10 D) with the distance correction in place. Accommodative function was also assessed in an age-matched control group (n = 125) for comparison. Each subject's neurologic status was derived from the NICPR. RESULTS: Children with CP demonstrate significantly reduced accommodative responses compared with their neurologically normal peers. Of the subjects with CP, 57.6% demonstrated an accommodative lag outside normal limits at one or more distances. Reduced accommodative responses were significantly associated with more severe motor and intellectual impairments (ANOVA P = 0.001, P < 0.01, respectively). CONCLUSIONS: Brain injury such as that present in CP has a significant impact on accommodative function. These findings have implications for the optometric care of children with CP and inform our understanding of the impact of early brain injury on visual development.

Accommodation, Ocular↗

PubMed2003

Peripheral resolution for achromatic and SWS gratings in early to moderate glaucoma and the implications for selective ganglion cell density loss.

PURPOSE: To investigate whether there is significant selective reduction in short-wavelength-sensitive (SWS) ganglion cell density in early to moderate glaucoma. METHODS: Peripheral achromatic resolution acuity (an indirect measure of the underlying midget ganglion cell density) and peripheral chromatic resolution acuity under conditions of blue cone isolation (an indirect measure of the underlying small bistratified ganglion cell density) were measured at 13 degrees eccentricity in four oblique meridians in 15 eyes (mean age, 64.6 +/- 9.6 years) with early to moderate glaucoma. The results from the subjects with glaucoma were compared with those in a group of 17 age-matched normal eyes (mean age, 62.5 +/- 6.6 years). RESULTS: Mean achromatic resolution acuity across the four locations was significantly lower in the subjects with glaucoma than in the normal subjects (2.92 vs. 4.01 cyc/deg). Mean chromatic resolution acuity across the four locations was also significantly lower in the subjects with glaucoma than the normal subjects (0.78 vs. 0.99 cyc/deg). There was no selective loss of mean SWS acuity in the subjects with glaucoma. Individual location analysis revealed that the chromatic-achromatic resolution ratio was not significantly different in the subjects with glaucoma who had early glaucomatous damage when compared with the normal subjects. The chromatic-achromatic resolution ratio was lower than normal at certain locations in certain individuals with early glaucoma. CONCLUSIONS: The results indicate that there is no evidence of significant selective reduction in global SWS ganglion cell density in early to moderate glaucoma. However, there may be selective loss of SWS ganglion cell density at individual locations in individual eyes.

Aged↗

PubMed2003

Familial keratoconus with cataract: linkage to the long arm of chromosome 15 and exclusion of candidate genes.

PURPOSE: Keratoconus and cataract are common causes of visual morbidity. Both conditions show genetic predisposition. The purpose of this study was to map the disease locus in a large three-generation family affected by combined early-onset autosomal dominant anterior polar cataract and clinically severe keratoconus. Uniquely, in this family both disorders were present and fully penetrant in those affected. METHODS: Thirty members of the family were examined clinically on two occasions, at an interval of 5 years, to establish their phenotypes and determine the progression of the disease. Genomic DNA was extracted from blood samples of 16 affected and 14 unaffected individuals, and typed with more than 350 highly polymorphic microsatellite loci in a genome-wide linkage screen. Markers were amplified by PCR with fluorescently labeled primers and sized with an automated DNA analyser before calculation of lod scores. After linkage was established, several positional candidate genes were assessed by PCR-based DNA sequencing. RESULTS: The locus for keratoconus with cataract was mapped to a 6.5-Mb region of the long arm of chromosome 15, at 22.33-24.2 between CYP11A and D15S211. The positional and functional candidate genes CTSH, CRABP1, IREB2, and RASGRF1 were excluded as the cause of keratoconus with cataract in this family. CONCLUSIONS: This is the first report of a family with autosomal dominant inheritance of keratoconus in association with cataract. The causative gene maps to the long arm of chromosome 15 but has not yet been identified.

Adolescent↗