City Research Online

Abstract

Previous studies relating to total astigmatism in the young were collected and reviewed. Information on the source(s) of this astigmatism was found to be scarce in infants and children. It was proposed to study the corneal astigmatism in subjects under 5 years of age which would involve making measurements of their corneal radii in the principal meridia.

Methods of measuring corneal radii were considered with particular emphasis placed on those suitable in young subjects. It was decided that photokeratoscopy would be the most practical method to be adopted for this study. A portable photokeratoscope was calibrated for use and its accuracy and reliability assessed. Strong linear relationships were found between the corneal radii and corneal astigmatism measurements obtained using the photokeratoscope and a conventional keratometer on 10 adult eyes.

The photokeratoscope was used to record the HVID, flattest and steepest corneal radii and corneal astigmatism from 1 eye each of 152 normal subjects aged 1 month to 5 years and from 1 eye each of 35 aphakic binocular congenital cataract subjects aged 1 month to 15 years.

In the normal eyes, the HVID was found to increase sharply up to 6 months of age after which there appeared to be little change. This increase with age was statistically significant. The HVID values recorded in males were also significantly higher than those recorded in females. The mean values of the flattest and steepest corneal radii were seen to increase up to 6 months of age but these increases were not statistically significant. No significant differences were also present between the sexes. The incidence of corneal astigmatism >1D was observed to decrease significantly with age. A reduction in the mean values of corneal astigmatism was also seen as age increased.

In the binocular congenital cataract eyes, the HVID values tended to be smaller than those observed in normal eyes up to the age of 5 years. The corneal radii values mainly fell in the range found in normal eyes. The majority of the corneal astigmatism measured in the aphakic eyes was between 1 to 3 D.

The results on normal eyes supported the view that a major cause of total astigmatism in subjects under the age of 3 years is corneal in origin.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > R Medicine (General) R Medicine > RE Ophthalmology
Departments:	School of Health & Medical Sciences > Department of Optometry & Visual Science School of Health & Medical Sciences > School of Health & Medical Sciences Doctoral Theses Doctoral Theses

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