This paper seeks to address the question of how much do orbital cavernous haemangiomas actually change over time, and if there are any identifiable factors which can predict which lesions will grow and which will remain stable. In particular, if a haemangioma was found incidentally, are there any factors which can predict the likelihood of it requiring surgery in the future? The clinical records and images were reviewed of 104 patients with cavernous haemangiomas, 31 of these had been incidental findings. In all, 79 patients required surgical intervention. This included 11 from the incidentally diagnosed group, who unsurprisingly had less proptosis and were smaller at diagnosis than the symptomatic group. For all haemangiomas, factors predictive of needing surgery were greater size, choroidal folds, being male and extraconal location, but no factors were found which could predict which of the incidental lesions were more likely to grow. Overall, the incidentally found lesions were less likely to require surgery, and most were either stable or grew at less than 1mm a year. Despite this, 35% of these did require surgery within five to six years of diagnosis. Symptoms which led to surgery included reduced acuity, diplopia and increasing proptosis. The authors advise regular observation and imaging initially, but if incidental lesions are stable for five years they are very likely to remain stable in the long-term. This is an extensive multi-centre review with useful data regarding the management of asymptomatic, incidentally found cavernous haemangiomas, and will help when advising patients on the likelihood of needing surgery in the future.