Figure 3: Pupil block glaucoma in a silicone oil filled aphakic eye. In the absence of a peripheral iridectomy or in the presence of an occluded one, silicone oil can fill the pupillary aperture. Aqueous humour accumulates behind the iris, inferiorly, in the posterior segment. 1. The peripheral iris bows forward and may occlude the drainage angle. 2. The continued accumulation of aqueous may force silicone oil into the AC where it can cause further mechanical obstruction to the drainage of aqueous humour.