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J. P. Wood, M. Plunkett, V. Previn, G. Chidlow, R. J. Casson; Rapid and Delayed Cell Death of Cultured Trabecular Meshwork Cells After Selective Laser Trabeculoplasty. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3151.
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© ARVO (1962-2015); The Authors (2016-present)
Selective Laser Trabeculoplasty (SLT) is becoming increasingly employed as a means to reduce elevated intraocular pressure (IOP). Although it is known that the trabecular meshwork (TM) represents the major target of such a laser-based treatment, the actual mechanisms involved in this response have not been clearly delineated. Studies were therefore conducted to investigate the modes of damage and death of cultured bovine TM cells subjected to SLT in vitro.
Bovine TM cells 3-4 which had been grown on borosilicate glass coverslips and which had been pigmented by incubation for 16 hours with 100µg/ml melanin. Cells were irradiated with an SLT laser at a variety of energy settings (0.4 mJ-2.0 mJ), using the observation of bubble formation to correlate energy levels used in vitro to those employed in the clinic. Influences on cells were determined by trypan blue exclusion assays, TUNEL labeling, caspase-3 immunocytochemistry and morphological changes; changes were assessed over a period of up to 12 days subsequent to laser treatment.
At higher energy levels (2.0, 1.5 mJ), obvious immediate vaporization of cells was detected on coverslips at the site of laser treatment. This was not so evident at lower settings. At all energy settings, however, trypan blue exclusion analyses clearly showed that cells died rapidly by necrosis over a period of 30 minutes to 12 hours immediately adjacent to the site of laser treatment. This was followed by the delayed death of more outlying cells at 2-10 days following treatment that was characteristic of apoptosis. The degree of both immediate and delayed cell death was directly related to the magnitude of the laser energy setting and the distance from the central irradiated zone in each case.
SLT causes TM epithelial cell death in culture by the processes of vaporization, necrosis or delayed apoptosis, depending on the radiant exposure received by individual cells. The three dimensional nature of the TM along with the irregular energy distribution profile of the SLT laser are likely to result in all three types of cell death within the irradiated zone, in vivo.
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