The effects of strabismus surgery on anterior segment circulation

Anterior segment circulation was assessed in 35 adults one day after squint surgery by clinical observation and low-dose fluorescein iris angiography. Seventeen patients had primary vertical rectus muscle surgery and all showed angiographic evidence of ischaemia. No ischaemia was found in the 15 patients who had secondary vertical rectus muscle surgery, or any horizontal rectus muscle surgery. The staged group had intermediate findings between the above two. Age, dysthyroid eye disease and type of conjunctival incision did not correlate with fluorescein iris angiographic sector-filling delay on the first post-operative day. The time taken for the sector with delay to fill becomes less during the first two post-operative weeks. Redistribution of iris filling persists, however. This data suggest that the safe interval before further muscle surgery can be done is shorter than has previously been assumed. Since the anterior ciliary arteries do not reform into canals the probable mechanism of redistribution of blood flow is from the long posterior ciliary arteries and increased capacity of the collateral circulation.