The ultrastructural pathological features of congenital microcoria. A case report
W. A. Simpson and M. A. Parsons
Department of Ophthalmology, Royal Hallamshire Hospital, Sheffield, England.
We describe the light microscopic, immunohistochemical, and electron
microscopic findings in a sporadic case of congenital microcoria in a
72-year-old man with senile cataract. We demonstrated a lack of
myofilaments and desmin in the stromal cytoplasmic processes of the
anterior pigmented cells of the iris, although other features of muscle
differentiation were present in these few surviving cell processes that
normally form the pupil dilator muscle. Degenerative changes in anterior
pigment cells and iris stromal atrophy were thought to be late secondary
features of microcoria. The findings suggest that congenital microcoria
results from a defect of intermediate filaments in the terminal fetal
stages of differentiation of the anterior pigmented epithelial cell of the
iris, with absence of myofilaments and consequent failure of development of
a functional dilator pupil muscle.
