Purpose. To measure the tissue mechanical response to elevated
intraocular pressure (IOP) using intact globe expansion
of rabbit eyes. This method examined rabbit kit (2–3 weeks
old) eyes as a model for weakened tissue and evaluated riboflavin/
UVA and glyceraldehyde cross-linking treatments.
Methods. The ocular shape of enucleated eyes was photographed
during a 24-hour period while a controlled IOP was
imposed (either low IOP 22 mm Hg or high IOP 85 mm
Hg). Untreated controls consisted of kit eyes tested at both
low- and high IOP and adult eyes tested at high IOP. Treated kit
eyes (dextran controls, riboflavin/UVA treatment of the cornea,
and glyceraldehyde treatment of the entire globe) were tested
at high IOP.
Results. Low IOP elicited negligible creep of the sclera and
very gradual creep of the cornea. In contrast, high IOP induced
up to an 8% strain in the sclera and a 15% strain in the cornea
of rabbit kit eyes. The expansion of adult eyes was less than
one third that of kit eyes at the same, high IOP. Riboflavin/UVA
treatment of corneas reduced expansion compared with that in
both dextran-treated and untreated control corneas. Glyceraldehyde
treatment prevented expansion of the cornea and
sclera.
Conclusions. The intact globe expansion method (GEM) imposes
a loading geometry comparable to in vivo conditions and
can quantify changes in mechanical stability as a function of
testing conditions (e.g., IOP, tissue maturation, and therapeutic
cross-linking) with small sample sizes and small variability.
Rabbit kit eyes provide a model of weak tissue suitable for
screening treatments that strengthen the cornea and sclera
