69 R

New Aspects of PCO-Prevention
Spalton DJ

London

Square edged intraocular lenses have been recognised clini-
cally and experimentally to be associated with low rates of PCO
but the cellular mechanism for this observation has not been
explained. In a laboratory experiment we grew bovine lens epi-
thelial cells in square and round edged culture plates and found
that the cells migrated out of both culture well profiles. Although
bovine cells cannot be direct equated with human lens epithelial
cells this experiment casts doubt on whether square edged intra-
ocular lenses exert their effect by inducing contact inhibition of
cellular migration. An alternative explanation is that square edged
intraocular lenses exert a greater pressure profile on the posterior
capsule and that this acts as a barrier to lens epithelial cell migra-
tion. We have imaged the profile of round and square edged intra-
ocular lenses and show that a square edged intraocular lens
should exert a greater pressure on the posterior capsule at its
margin. Mathematical modelling suggests that this is in the order
of at least 70 %. In vivo this is likely to be considerably increased
by the effect of capsular fibrosis. We are now exploring this hypo-
thesis in a lens epithelial cell culture model. This model shows
that it takes longer for lens epithelial cells to breach the optic
edge with square intraocular lenses than round lenses and that
this time increases if pressure is applied to increase IOL posterior
capsular contact.




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