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S.V. Girman, B. Lu, R.D. Lund; Light Adaptation Study in RCS Rats, Untreated and with Subretinal Graft of Human RPE Cells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):482.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose To differentiate the rod and cone functions in the retina of dystrophic RCS rats, untreated and after grafting human RPE cells into the subretinal space. Methods We studied light-adaptation curves in dark-adapted pigmented dystrophic RCS (grafted and untreated) and control normal rats by recording threshold multi-unit responses versus increasing background illumination (BI) in the superior colliculus to presentation a light spot (2º in dia, 0.1 s ON, 3 s period, brightness controlled in 0.1 log step). The ganzfield BI was 0.02 cd/m2 when illuminator turned on, or indefinite (< 0.001 cd/m2 ) when turned off . A chamber with changeable filters (used to control retinal BI) was installed in front of eye; the filter value was decreased by steps of 0.5 log. Thresholds were measured as intensity of stimulus (with eye + stimulus filters) needed to give a response above baseline. Results The results (see fig) shows that in normal rats the visual threshold has a minimal value at BI below -8 log cd/m2 from where it rises progressively with increasing BI to an inflexion point at around -4 log cd/m2, which presumably corresponds to rat's mesopic range of BI. In dystrophic rats the threshold maintained the constant minimal value up to BI of -4 log cd/m2 , at which again there is the inflection in the curve. The position of the inflection point remains similar in normal and in dystrophic rats aged 21 days upwards, as well as in the grafted rats at any post-grafting age. The thresholds are shifted up with age in both last groups, but in grafted animals this shift is much less evident than in untreated dystrophic rats, so that, e.g., the part of retina best-preserved by the graft shows at age of 2 months nearly the same visual thresholds as those of 21 days old untreated rats. Conclusions Our data suggest that: i) the function of rod photoreceptors is severely compromised in dystrophic RCS rats as young as 21 days old, whereas cone function deteriorates progressively with age; ii) subretinal grafting of healthy RPE cells does not restore rod function, but it significantly slows down the process of functional deterioration. View OriginalDownload SlideView OriginalDownload Slide
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