tailieunhanh - Ebook Chandler and grant's glaucoma (5/E): Part 2
Part 2 book “Chandler and grants glaucoma” has contents: Combined mechanisms, secondary open-angle glaucoma, laser methods in glaucoma, glaucoma surgery, diagnosis and treatment of glaucoma in children, special considerations. | Section Combined Mechanisms vi 38 Combined Open-Angle and Angle-Closure Glaucoma Joel S. Schuman, MD, FACS and David L. Epstein, MD, MMM The obstruction to aqueous outflow in primary openangle glaucoma (POAG) is due mainly to abnormalities within or just beyond the trabecular meshwork, whereas in angle-closure glaucoma, the cause of obstruction to aqueous outflow is contact between the periphery of the iris and the corneoscleral trabecular meshwork, preventing access of aqueous humor to the normal aqueous outflow system. There is no reason why both conditions could not occur in the same eye. Because each has an independent basis, a certain number of coincidences of this sort can be expected. On the other hand, there are more cases of residual open-angle glaucoma after laser iridectomy than would be expected by chance. There is also a hypothetical possibility that repeated episodes of angle closure could cause permanent damage to the corneoscleral trabecular meshwork even without formation of peripheral anterior synechiae (PAS) and that they could in this way induce a form of permanent open-angle glaucoma that would persist between episodes of angle closure and after angle-closure attacks were terminated by iridectomy. This has been mentioned previously (open-angle glaucoma due to chronic iris touch). As yet, however, we lack clear evidence for this mechanism. Occasionally, patients present evidence of having both open-angle and angle-closure glaucomas. In some of these patients, one may be certain that only 2, 3, or 4 clock-hours of the angle are closed, but one may find an IOP of 40 mm Hg, and tonography may indicate an impairment of facility of outflow consistent with the intraocular pressure (IOP), but disproportionately more than the extent of angle closure. When the findings are this clear and definitive, the diagnosis is easy. One has to conclude that there is not enough angle closure to account for this amount of glaucoma. In many other cases, it is .
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