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Sher A. Aslam, Mandeep Singh, Peter Charbel Issa, Wayne I.L. Davies, Michelle McClements, Robert A.H. Scott, Robert E. MacLaren; Development Of A Simulated Model For Battlefield Retinal Laser Injury. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5821.
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© ARVO (1962-2015); The Authors (2016-present)
Battlefield lasers are used as defensive countermeasures and for target acquisition though the future may see development of offensive weaponry. Due to increased use of such technology the risk of associated ocular injury is growing which can manifest as anterior or posterior segment damage. Visual loss resulting from direct retinal exposure primarily occurs from the degeneration of cones following foveal laser injury. We designed an in vivo model to assess the effects of laser application on cone survival.
Frequency-doubled 532nm Nd:YAG laser was applied to the retinae of transgenic B6.Cg-Tg(OPN1LW-EGFP) mice (N=12) in which green fluorescent protein (GFP) expression is restricted to long/medium (LM) wavelength sensitive cones. The effects were observed using the fluorescence mode of a confocal scanning laser ophthalmoscope (cSLO) enabling quantification of lesion size and GFP-positive photoreceptor density over time. A cross-sectional study was also conducted for histological evaluation of retinal lesions following laser exposure. Terminal Deoxynucleotidyl Transferase Mediated dUTP Nick End Labeling (TUNEL) was used to detect apoptosis on retinal sections taken between 8h and 7 days post laser application (N=3 per time point).
cSLO imaging showed a reduction of fluorescent LM cones within the area of laser application from 1 week post exposure with a significant increase in lesion size and loss of fluorescence by 6 weeks (two-sided t-test, p<0.0001). Positive TUNEL stain in areas of laser application was confined to the outer nuclear layer confirming that photoreceptor death occurred via apoptosis. TUNEL positive cells decreased from 24h to 5 days post laser exposure (one-way ANOVA, p<0.0001). The number of photoreceptor cells counted at the centre of the lesions decreased to 62 ± 4.8 % and 55 ± 3.8 % of non-lesioned internal control areas at 1 (two-sided t-test, p<0.0001) and 3 weeks (two-sided t-test, p<0.0001) respectively.
These results support a model for longitudinal study of the effects of retinal laser injury by visualising apoptosis of single LM cones in vivo. This technique provides opportunity for evaluation of interventions which may prove beneficial in reducing battlefield retinal laser injury.
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