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fatima fikri, Deepak Edward, Sami Al Shahwan, Khitam Al Hati, Ibrahim Al Jadaan; Immunohistochemical Features of Encapsulated Blebs Following Ahmed Glaucoma Valve Implantation. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3055.
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We hypothesized that the extracellular matrix (EM) of encapsulated bleb played an important role in the hydraulic resistance of encapsulated blebs. To test this hypothesis we used immunohistochemistry to label the EM and proliferating fibroblasts in excised encapsulated blebs following Ahmed Glaucoma valve (AGV) implantation and compared them with control Tenons tissue.
Excised encapsulated blebs (n=14) and normal Tenons tissue (n=4) were studied. Using indirect immunohistochemistry, the tissue was labeled with antibodies against collagen III, heparan sulfate, TGF β and PCNA. The staining intensity was assessed in a semiquantitative fashion by two masked observers and graded from 0-+4 staining. The clinical features of the patients were reviewed retrospectively.
The mean age of patients was 15 ±16.3 years. The diagnosis included congenital glaucoma (50%), secondary glaucoma (35.7%), primary angle closure glaucoma and primary open angle glaucoma (7.1% each). AGV, model S2 was inserted in 85.7%, while 14.3% received the S1 model. The mean IOP prior to AGV revision was 38.6 ±11.6 mmHg. The mean interval between AGV insertion and valve revision was 37.3 ±51.8 month. There were no significant difference in the staining intensity of collagen III and TGF β between the cases and controls (p=0.72 and p=0.87 respectively). Heparan staining was more intense in the blebs compared to controls, however it was not statistically significant (p=0.19). EM labeling was patchy with variable intensity in the excised tissue. The PCNA cell count did not differ significantly from control (p=0.32). There was a weak positive correlation between IOP at time of revision and the degree of collagen III and PCNA staining. A weak negative correlation was noted between IOP and revision time, and between Collagen III, heparan and PCNA label and age.
The EM markers used in this study did not show differences in immunolabeling between excised capsules and control tissue. It is possible that a) EM markers other than those studied played an important role in increased hydraulic resistance or b) EM density as reflected by the patchy distribution of EM marker label rather than averaging immunohistochemical label maybe important in predicting the hydraulic resistance of the capsule.
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