Heritability of corneal curvature and astigmatism: a videokeratographic child-parent comparison study.
OBJECTIVE
To study child-parent similarities and the heritability of corneal shape by applying a variance component model to videokeratographic data.


METHODS
Sixteen astigmatic (keratometric cylinder >/= 1.0 D) and 18 nonastigmatic (keratometric cylinder < 1.0 D) children, 7-14 years of age (mean age, 9.5 years), were enrolled with their parents. Corneal curvature, corneal astigmatism (axis and magnitude), asphericity, corneal uniformity index, and Rabinowitz McDonnell inferior-superior dioptric asymmetry value (I-S value), as well as spherical and astigmatic topographic patterns, were determined by a corneal topographer. Child-parent comparisons were assessed through a 1-way analysis of variance and the chi test. For corneal curvature, corneal astigmatism, and asphericity, heritability was estimated by a variance component model after adjustments were made for age and sex.


RESULTS
Both astigmatic and nonastigmatic children showed steeper keratometric values than their parents (P < 0.05). The axis values of corneal astigmatism showed no statistically significant difference (P = 0.684) between astigmatic offspring and their parents, whereas the magnitude values were significantly higher (P < 0.001) in astigmatic children. Altogether, 68% (95% confidence interval [CI], 66%-72%) of child-parent comparisons showed the same topographic pattern between parents and their offspring. Heritability values (48%; 95% CI, 36%-57%) were statistically significant for corneal curvature (P < 0.00001) and <30% for corneal astigmatism and asphericity.


CONCLUSIONS
The application of a variance component model to videokeratographic child-parent comparisons suggests that the genetic contribution to corneal shape affects corneal curvature rather than corneal astigmatism.
Cagigrigoriu
Andrea
A
Department of Ophthalmology, San Luigi Gonzaga Hospital, Turin University, Turin, Italy. andrea.cagi@alice.it
Gregori
Dario
D
Cortassa
Fabrizia
F
Catena
Francesca
F
Marra
Antonella
A
D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000235:genetics*; D049628:Body Size / Q000235:genetics*; D002648:Child; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D005828:Genetics, Population; D006801:Humans; D008297:Male; D008875:Middle Aged; D010290:Parents; D019655:Quantitative Trait, Heritable