PubMed · 14838064
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A POSNER. 1951. Recent developments in tonometry.. https://doi.org/10.1016/0002-9394(51)91036-7
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AIM: To compare the effect on intraocular pressure (IOP) of large vs small scleral flap size during trabeculectomy using adjustable sutures. METHODS: Trabeculectomy operations were performed on nine donor human eyes connected to a constant flow infusion with real-time IOP monitoring. Large scleral flaps (4 x 4 mm, 16 mm(2), n=12) or small scleral flaps (3 x 2 mm, 6 mm(2), n=9) were constructed over 0.76 mm(2) sclerostomies. For each procedure, equilibrium IOP was measured following tight closure with two four-throw adjustable 10-0 nylon sutures. RESULTS: Five scleral flaps were thin or poorly constructed; four of these were in the initial seven procedures, implying learning effect. These had a mean absolute IOP of 7.6 mmHg (range 2.7-12.4 mmHg) and mean relative IOP of 28.3% of baseline (range 10-45.8%) after closure. In the remaining 16 good quality procedures, mean IOP was 1.3 mmHg (range 0-3.4 mmHg) after sclerostomy, confirming minimal outflow resistance before closure. Following flap closure mean IOP was 20 mmHg (SD 4.4, range 15.5-29.3 mmHg) for large (n=8), and 18.7 mmHg (SD 3.6, 15.9-25.8 mmHg) for small (n=8) flaps (unpaired t-test, P=0.26). Mean IOP (% baseline) was 71.6% (SD 8.4, range 60.6-86.6%) and 66% (SD=12.7, 46.8-86.6%) for large and small flap groups, respectively (unpaired t-test, P=0.2). CONCLUSIONS: Well-constructed scleral flaps of both sizes were able to support an average IOP at least two-thirds of baseline, and both had similar absolute IOP levels. Errors in flap construction resulted in loss of IOP control. Smaller flap size does not appear to compromise control of early postoperative IOP using adjustable sutures.
DNA damage is related to a variety of degenerative diseases such as cancer, atherosclerosis and neurodegenerative diseases, depending on the tissue affected. Increasing evidence indicates that reactive oxygen species (ROS) play a key role in the pathogenesis of primary open angle glaucoma (POAG), the main cause of irreversible blindness worldwide. Oxidative DNA damage is significantly increased in the ocular epithelium regulating aqueous humor outflow, i.e., the trabecular meshwork (TM), of glaucomatous patients compared to controls. The pathogenic role of ROS in glaucoma is supported by various experimental findings, including (a) resistance to aqueous humor outflow is increased by hydrogen peroxide by inducing TM degeneration; (b) TM possesses remarkable antioxidant activities, mainly related to superoxide dismutase-catalase and glutathione pathways that are altered in glaucoma patients; and (c) intraocular-pressure increase and severity of visual-field defects in glaucoma patients parallel the amount of oxidative DNA damage affecting TM. Vascular alterations, which are often associated with glaucoma, could contribute to the generation of oxidative damage. Oxidative stress, occurring not only in TM but also in retinal cells, appears to be involved in the neuronal cell death affecting the optic nerve in POAG. The highlighting of the pathogenic role of ROS in POAG has implications for the prevention of this disease as indicated by the growing number of studies using genetic analyses to identify susceptible individuals and of clinical trials testing the efficacy of antioxidant drugs for POAG management.