**6. Differential diagnosis**

Glaucoma with pupillary block – pupillary block angle closure occurs when the posterior surface of the iris, in the pupillary margin, comes in contact with the lens. The increased pu‐ pillary block obstructs the flow of the aqueous humour from the posterior chamber to the anterior chamber, resulting in increased pressure in the posterior chamber and forward bowing of the peripheral iris. This closes the anterior chamber angle, obstructing the trabec‐ ular meshwork and the outflow channels with subsequent elevation of the IOP. Laser pe‐ ripheral iridotomy is the treatment of choice [45] and should be performed in all cases of pupillary block glaucoma. In pupillary block, there should not exist axial shallowing of the anterior chamber (movement of the IOL toward the cornea). The anterior chamber usually remains deeper in the center than on its circumference, in contrast to malignant glaucoma, where axial chamber shallowing also occurs. If there is axial shallowing, then fluid has somehow moved posteriorly and the vitreous is acting to shallow the chamber [46].

Angle closure glaucoma – shallowing of the anterior chamber occurs symmetrically in both eyes. In the affected eye, the filtration angle is closed, there is a sudden increase in IOP, and microcystic edema of the cornea. Conjunctival injection and a medium size pupil may ac‐ company these symptoms [47]. It occurs regardless of surgery and is caused by anatomical predisposition.

Choroidal effusion - a static condition which is observed independently of operation and has inflammatory (trauma and intraocular surgery, scleritis, following cryocoagulation and photocoagulation, chronic uveitis, Vogt-Koyanagi-Harada disease) or hydrostatic causes (hypotony and wound leak, dural arteriovenous fistula, abnormally thick sclera in nanophthalmos, possibly in emmetropic or myopic eyes or associated with Hunter's syn‐ drome). Uveal effusion should not be considered to be a distinct clinical entity but rather a state characterized by abnormal amounts of fluid in the choroid resulting in thickening of the choroid, accumulation of fluid in the suprachoroidal space resulting in choroidal detachment, and in some cases, accumulation of fluid in the subretinal space, resulting in nonrhegmatogenous retinal detachment. IOP may be normal but is often reduced in uveal effusion secondary to inflammatory factors. An exception occurs in nanophthalmic uveal effusion wherein IOP is normal or frequently elevated and chronic angle closure glauco‐ ma may develop [48].

Suprachoroidal hemorrhage – shallowing of the anterior chamber coexists with increased IOP, sudden pain, and the presence of a haemorrhagic, non-serous detachment of the cho‐ roid in biomicroscopic and ultrasonographic examination. It occurs most often within 1 week after surgery, rarely later [6]. Suprachoroidal hemorrhage may be caused by bleeding diathesis, anti-coagulants, paranasal sinusitis, or may occur spontaneously. Small supra‐ choroidal hemorrhages occurring during surgery are usually absorbed extemporaneously. Suprachoroidal hemorrhage may be also related to postoperative hypotony, and in the late postoperative period, may be connected to increased venous pressure or increased tension of the abdominal press.
