Abstract
Purpose:
We have developed a pigmented mouse model for light induced retinal degeneration (LIRD). Transgenic mice are commonly available on the 129sv background and these mice can be used for optokinetic tracking (OKT). Here we test our hypothesis that it is possible to light damage retinas in a pigmented strain of mice using high intensity white-light LED boxes and that the retinal damage would be similar to LIRD in BALB/c albino mice.
Methods:
Light damage: 129sv and BALB/c mice were obtained from Charles River. 129sv mice were pretreated with 1% atropine eye drops to dilate pupils prior to light exposure. BALB/c mice were treated with 5-10k lux white light for 4 hours starting at ZT2. 129sv mice were treated with 50-70k lux for 4 hours starting at ZT2. OKT: visual acuity in 129sv mice was measured using an OptoMotry OKT system 6 days after light damage. ERG: retinal function was measured 7-10 days following light exposure using scotopic ERGs. Histology: eyes were embedded in epon and toluidine blue sections were imaged using brightfield microscopy.
Results:
Exposure to toxic light induces LIRD in 129sv mice. OKT results showed a dose dependent reduction in visual acuity with 50k lux for 4 hours (0.292+/-0.021) significantly (P=0.029) reducing OKT response compared to dim controls (0.446+/-0.081) and no detectable response with 70k lux (0+/-0) for 4 hours (P<0.001) (unpaired t-test). ERG results for 50-70k lux for 4 h doses reduced scotopic ERG a-wave and b-wave amplitudes by 75% and were all significant compared to dim control (P<0.001, one-way ANOVA and SNK post-hoc analysis at brightest flash intensity). The morphology of light treated 129sv retinas at the posterior pole showed thinning of outer nuclear layer, pycnotic/disrupted nuclei, no outer segments remaining consistent with light damage in BALB/c mice. The distribution of damage in 129sv mice showed more loss of photoreceptors at posterior pole consistent with light damage in BALB/c mice.
Conclusions:
Although pigmented, 129sv mice undergo LIRD. The toxic light dose needed is significantly higher than traditional LIRD in BALB/c. The decreased ERG and retinal degeneration are similar to that of BALB/c. OKTs and ERGs are useful measures of LIRD in 129sv mice.
Keywords: 688 retina •
426 apoptosis/cell death