PubMed Health⌕ Search

Biomedical subjects

A J Mash

Publications and source records attributed to A J Mash.

8 recordsLinked to original sources
PubMed1979

Estimates of genetic correlations among clinical measures of the eye.

In a quantitative genetic investigation of seven clinical tests, five pairs were significantly correlated: (1) cover test measures and corneal power, (2) corneal power and divergence recovery points, (3) convergence and divergence recovery points, (4) divergence break and recovery points, and (5) convergence break and recovery points. Common genes may account entirely for the gene influence on cover test measure; thus, parents who are above the population mean for corneal power will have offspring with a tendency toward an exodeviation (phoria). The two convergence amplitudes may depend on the same gene differences, whereas the two divergence amplitudes only partly reflect a common function, suggesting that they may be indexing somewhat different underlying physiologic mechanisms.

Accommodation, Ocular↗
PubMed1978

Intentional surgical overcorrection of acquired esotropia.

Fifty-eight patients with surgically treated acquired nonaccommodative esotropia were studied retrospectively, to ascertain what immediate surgical result gives the best chance for a postoperative bifoveal fusional result. Of the cases that were initially overcorrected (exodeviations), approximately two thirds were fusing six months or more after surgery. Of the cases that were initially aligned (orthophoric) or undercorrected (esodeviations), only one third were fusing after the same period. These results suggest that intentional surgical overcorrection of cases of acquired nonaccommodative esotropia that have a good fusional potential (ie, equal vision) does appear to be a desirable goal for the immediate postoperative period.

Adolescent↗
PubMed1975

Genetic analysis of vergence measures in populations with varying incidences of strabismus.

Genetic parameters were contrasted for vergence amplitudes within three populations--esotropic, exotropic, and randomly selected populations-who differed in their incidence of subtypes of strabismus. In general, heritabilities for convergence exceeded those for divergence, and heritabilities for recovery points exceeded those for break points. Heritability estimates for diveregence amplitudes were significantly different for the random and esotropia populations, while convergence heritability estimates for these groups were similar. Thus, gene differences influencing divergence ability contributed to genetic variance for strabismus.

Accommodation, Ocular↗
PubMed1975

Genetic analysis of cover test measures and AC/A ratio in human populations with varying incidences of strabismus.

The genetic analyses of indices relating to distance alignment and accommodative convergence are presented. This approach is important in understanding the contribution of genetic factors to observed individual differences for these measures. Abnormalities of either of these two components results in a tendency towards either a convergent or divergent position of the eyes (relative to the position of fusional demand) and thus places an additional load or strain on the other components of the binocular mechanism which must compensate for this potential disruption. If compensation is inadequate to maintain alignment of the eyes, a manifest deviation will result. Consequently, an understanding of the aetiology of such factors underlies an understanding of the aetiology of nonparalytic strabismus. The three populations displayed different tendencies in the cover test measure. The average tendency for each of the populations was consistent with the type of deviation common to all propositi of families within each of the respective populations. The heritability of this character was similar in the three populations and was dependent on the contribution of the female parent only, but to a substantial degree (h2 = 0-42 +/- 0-12). The nature of the sex difference is at present open to speculation. The population means within generations were similar for the gradient measure of AC/A ratio. The heritability of this character (0-38 +/- 0-09) suggests that the genetic component is of substantial importance underlying individual differences for AC/A ratio.

Accommodation, Ocular↗
PubMed1975

Quantitative guidelines for exotropia surgery.

The effect of numerous preoperative variables on the amount of surgical correction attained was assessed in a population of intermittent exotropic patients; 54 had bilateral recession surgery, 48 had recess resect surgery. By appropriate multivariate statistical analyses, about 95 per cent of the variance in results of surgery (expressed as change in deviation from preoperative to the postoperative time in prism diopters per millimeter of surgical correction) could be accounted for. A workable scheme for utilizing this data base to guide future surgery is presented in the form of quantitative formulae. In addition to this empirical derivation, insights are provided into the mechanics of ocular muscle operations and the maturation of the eye as it affects strabismus sergery. Expansion of this approach to a wider ranger of cases and to additional types of cases should result in a greater descriptive and surgical accuracy from strabismus surgery.

Adolescent↗
PubMed1975

Genetic analysis of indices of corneal power and corneal astigmatism in human populations with varying incidences of strabismus.

Heritability estimates for corneal power were found to be high and similar for two populations which differed in their incidence of esotropia. This similarity suggest (1) that genetic differences for corneal power do not contribute to the difference in heritability for spherical refractive error reported for these populations and (2) that this character is not a critical variable contributing to the pathophysiology of esotropia. Heritability estimates for corneal astigmatism were, in most cases, rather low. The pattern of population and sex differences among heritability estimates was consistent with those previously reported for cylindrical refractive error. These population differences in heritability suggest that they contribute to population differences found for cylindrical refractive error.

Adult↗