Before drawing general conclusions about corneal behavior from the present results, a number of factors should be taken into account. First, it should be noted that the architectures of the mature avian and mammalian stroma differ at a fundamental level,
14 likely as a legacy of contrasting developmental processes.
43,44 This may partly reflect biomechanical requirements, such as those imposed by the need for the avian cornea to accommodate.
45 Second, the trephinate inflation method used in our study involves the cornea and limbus but, in clamping the tissue outside the limbus, neglects the influence of the sclera. In doing this we inevitably compromise to some extent the natural load-bearing environment of the cornea because, under in vivo conditions, the sclera may be expected deform in response to IOP, thereby affecting the cornea.
31 Indeed, modeling studies have indicated that the biomechanical stability of the anterior eye is likely maintained by a precise rheological balance between the cornea, limbus, and sclera.
46 –50 Moreover, the possible in vivo effects on the RGE cornea of both increased scleral size and the likely scleral restructuring implied by globe enlargement
22 –25 cannot be assessed using trephinates. Third, a limitation of the mathematical shell analysis used to calculate stress-strain behavior is that it approximates the chicken cornea as a homogeneous, spherical structure,
26 whereas in reality it is both aspheric and, as we have shown in the current paper and previously
24,25 demonstrates variation in collagen fibril aligment as a function of corneal position and depth. Last, possible alterations in noncollagenous corneal matrix components, such as specific proteoglycan types and collagen cross-links have not been investigated in RGE.