الفهرس 
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Abstract
Hypotony may be defined both statistically and clinically. The statistical definition of hypotony is intraocular pressure (IOP) less than 6.5mmHg, which is more than 3 standard deviations below the mean IOP. The clinical definition of hypotony is IOP low enough to result in vision loss. While clinical signs and symptoms are usually reversible in acute and transient stages, chronically decreased IOP can have deleterious effects on intraocular tissue morphology and function. Hypotony can occur with either increased outflow of aqueous humor or, less often, reduced production of aqueous humor by the ciliary body. Increased outflow may occur via a surgical wound leak, over filtering bleb, cyclodialysis cleft, scleral rupture, etc. Decreased aqueous humor production by the ciliary body is usually seen in the setting of inflammatory conditions. Hypotony can be encountered in the ophthalmologist’s practice, with many cases being caused by glaucoma surgery. Hypotony is a significant complication that has been associated with delayed visual recovery following filtering surgery. Vision loss associated with low IOP may be attributed to many causes including corneal edema, astigmatism, and macular edema. Several procedures were taken intra- and postoperatively to decrease the incidence of hypotony, such as releasable suture, laser suture lysis techniques, and/or the adjunctive use of intraoperative viscoelastic material. Despite these approaches, however, hypotony can still occur. This research aimed to study the causes, risk factors, adverse effects and management plans of ocular hypotony after different glaucoma surgeries. 205 eyes underwent various types of glaucoma surgry were enrolled in this retrospective study. thirty eyes were diagnosed with postoperative hypotony. Our study showed that combined viscocanalostomy with trabeculectomy and MMC, combined phacoemulsification, viscocanalostomy, and trabeculectomy with MMC and combined viscocanalostomy with express shunt implantation with MMC had the highest incidence of post glaucoma surgery hypotony (P = 0.012, 0.043, <0.001 respectively). Whereas Ahmed glaucoma valve implantation followed by trabeculectomy with MMC had the lowest in incidence of post glaucoma surgery hypotony. Other glaucoma surgeries were not significantly associated with hypotony. The present study showed that Pseudo-exfoliative glaucoma was associated significantly with post glaucoma surgery hypotony occurring in (60.0%) of the patients. Other glaucoma types were not significantly associated with hypotony. As regard to apparent cause of hypotony, excessive filtration was in 17 (56.7%) eyes, leaking bleb in 9 (30.0%) eyes, choroidal effusion in (10.0%) of eyes, inflammation in one eye (3.3%) while no reported cases of endophthalmitis. The current study showed that there was one patient (3%) with hypotony maculopathy and 29 (97%) eyes with no hypotony maculopathy. In our study, conservative treatment was done in 21 (70%) eyes, bleb revision was done in 5 (16.67%) eyes, choroidal drainage 2 (6.67%), AC reformation 3 (10%), intra bleb blood injection was done in 1.0 (3.3%) eye and removal of express valve was done in 1.0 (3.3%) eye.IOP was significantly decreased at “first diagnosis of hypotony” compared to “before operation” (P value <0.001). IOP “At last follow up” was significantly increased compared to “first diagnosis of hypotony”.