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Abrez Hussain Batcha, Christine T. Nguyen, Bang Bui, Erica Fletcher, Sarah Hosking; Retinal And Cortical Function Following Acute Intra Ocular Pressure Elevation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):166.
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To assess the effect of acute intraocular pressure(IOP) elevation on retinal and cortical function in pigmented (Long-Evans,LE) rats.
Acute IOP elevation (100mmHg for 60mins) was induced unilaterally in LE rats (n=24) and the contralateral eye served as sham-control. Full-field scotopic electroretinogram(ERG) and visually evoked potential(VEP) recordings were simultaneously obtained from treated and control eyes at 1day(n=24), 1week(n=18), 1month(n=12) and 3months(n=6) after IOP elevation. ERG responses were analyzed for photoreceptoral sensitivity(a-wave), rod and cone ON-bipolar(b-wave) function. VEP amplitude and latency was determined (N1-P1, P1-N2 and N1-N2). Blood pressure(BP) was monitored with tail-cuff sphygmomanometry.
Acute IOP elevation significantly reduced photoreceptoral amplitude (-21±4%) and sensitivity (-33±7%, p<0.01), an effect most pronounced at day1 (p<0.05). In eyes with IOP elevation, the degree of dysfunction was significantly related to BP (%function=0.42*systolic BP+41.12, R=0.55). A reduction in function was also noted in the sham-controls (amplitude, -25±3%; sensitivity, -43±6%, p<0.01). Rod mediated b-wave amplitude was significantly reduced (p<0.01), there was a trend for a greater effect in the IOP treated (-15±6%) compared with the control eyes (-8±6%), greater than for the cone b-wave (control eye, +3±4%; IOP eye, -5±5%, p<0.05). VEP analysis did not reveal any significant changes in cortical function following acute IOP elevation.
Retinal dysfunction was less severe than previous studies of ischemia-reperfusion due to (1) our IOP of 100mmHg is less than the previous studies, (2) our rats had higher BP at the time of IOP elevation and (3) we employed nutrient rich Hanks balanced salt solution. Nevertheless the study highlights the importance of BP in retinal injury. Moreover it shows that retinal function mediated by rod pathway is more sensitive to ischemic stress than the cone pathway.
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