Corneal surface area and perimeter were assessed as novel indices to monito
r anterior segment growth, using chicks reared under different photoperiods
. We obtained central and mid-peripheral corneal curvatures using photokera
tometry. Anatomical tracings of the anterior corneal surface also were made
from freeze-dried non-fixed preparations of the anterior segments of the s
ame eyes. Using either photokeratometry or anatomical data, the profile of
the anterior corneal surface was fit to a general equation for conical sect
ions; corneal surface area was estimated from surfaces of revolution. Optic
al techniques modeled the chick cornea as a circle or as an ellipse closely
resembling a circle. The anatomical technique, in contrast, modeled the ch
ick corneal profile as a hyperbola. Potential explanations of this discrepa
ncy are discussed. Regardless of which model is evaluated, the corneal surf
ace area and perimeter of two-week-old chicks are affected by the photoperi
od of rearing. Corneal surface area in particular proved more sensitive tha
n conventional measurements in identifying anterior segment effects of rear
ing under different photoperiods. Analysis of corneal area may prove useful
in evaluating the mechanisms governing anterior segment growth. (C) 2001 T
he College of Optometrists. Published by Elsevier Science Ltd. All rights r
eserved.