| Popis: |
One of the most common complications of filtering surgery is postoperative anterior chamber bleeding, or hyphema. Rates of postoperative hyphema in the literature vary, but have been reported to be up to 53%. However, recent data from the Tube Versus Trabeculectomy Study found that postoperative hyphema occurred in only 8% of eyes (8 of 105 eyes), possibly a sign of improving surgical technique. The severity of hyphema after trabeculectomy varies greatly. Bleeding in the anterior chamber may be so mild that visual acuity and surgical outcome are unaffected. On the other hand, a total hyphema may obstruct the visual axis and potentially result in fibrosis and failure of the filtering procedure. Furthermore, some patients with glaucoma who require surgical intervention also have visual impairment or blindness in the fellow eye. Loss of vision from hyphema in the operated eye, even if only temporary, can be functionally, and possibly psychologically, debilitating to the patient. The first step in reducing the risk for hyphema is obtaining a good medical history. Does the patient have any bleeding disorders, such as hemophilia or thrombocytopenia? Is the patient taking any medications that interfere with clotting or platelet aggregation, such as aspirin, clopidogrel, and/or warfarin? The use of antiplatelet and anticoagulation therapy is associated with a higher incidence of hyphemas. Platelets stop bleeding by plugging the hole in the broken vessel wall. Alternatively, antiplatelet medications inhibit platelet aggregation and therefore prolong bleeding time. Aspirin permanently alters developing platelets, and therefore its antiplatelet effect lasts until the complete cohort of affected platelets is turned over, approximately 2 weeks. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit platelet aggregation in a manner similar to aspirin, but the effect is to existing circulating platelets only and wears off in 2–3 days. Ticlopidine (i.e., Ticlid; Roche Laboratories, Inc., Nutley, New Jersey) and clopidogrel (i.e., Plavix; Bristol-Myers Squibb/Sanofi Pharmaceuticals Partnership, Bridgewater, New Jersey) also affect platelet aggregation by binding to the P2Y , resulting in irreversible platelet inhibition. |
