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Teruhiko Hamanaka, Tetsuro Sakurai, Akira Matsuda, Akira Murakami; Aging of Schlemm’s canal in primary open angle glaucoma in hereditary and non-hereditary cases. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3526. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
In ARVO 2011, we reported that the length of Schlemm’s canal (SC) was significantly shorter in the eyes of hereditary POAG (group A) than that of non-hereditary POAG (group B) patients (p=0.000). This time, we investigated whether the size of SC and SC endothelium (SCE) change according to aging by dividing patients’ specimens into two groups (A and B).
Trabeculectomy (TLE) specimens from 58 eyes in group A (58±14 y) and 64 eyes in group B (63±16 y) were processed for light microscopy of thrombomodulin (TM) immunohistochemical staining and transmission electron microscopy (TEM). TM staining patterns were investigated by measuring the length of negative TM areas of the inner wall of SC. SCE of 10 TLE specimens from patients before the age of 40 and 15 TLE specimens from those aged over 70 from both groups were observed by TEM. This study was approved by the IRB in Japanese Red Cross Medical Center.
There was no correlation between the size of SC and aging in both groups (p=0.0543, 0.3965 in groups A and B, respectively). TM staining was strongly positive in Sondermann’s canal, while it tended to be weak and sometimes discontinuous in the normal sized SC. Local negative TM staining areas of the inner wall of SC were observed in the eyes of both groups. The ratio of negative TM staining areas of the inner wall of SC/the total length of SC (RNTM) was significantly higher in group B (19.3%) compared to group A (4.9%) (p=0.0001303). RNTM in group B became significantly higher than that in group A after the fifth decade of life (over 50: p=0.001, over 60: p=0.0003, over 70: p=0.0099). TEM observation revealed that degeneration and dropout of SCE in the inner wall were frequently observed in the eyes of those aged over 70 but not in the eyes of those before 40 years old in both groups.
Different TM staining patterns in SC may reflect functional differences in SCE for aqueous outflow. The function of SCE in group B may be more affected according to aging. Degeneration and dropout of SCE observed in older eyes of both groups may be one of the reasons for the increasing risk factor of POAG occurrence or worsening of IOP control according to aging.
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