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A Novel Light Damage Paradigm for Use in Retinal Regeneration Studies in Adult Zebrafish
Published on: October 24, 2013
Structural and functional consequences of bright light exposure on the retina of neonatal rats
Sandrine Joly1, Allison Lindsay Dorfman, Sylvain Chemtob
1Department of Biological Sciences, University of Montreal, Montreal, QC, Canada.
Insights
Postnatal exposure to bright light before eye opening can cause significant retinal damage. Although not immediately apparent, this light-induced retinopathy (LIR) manifests functionally later in life.
Area of Science:
- Ophthalmology
- Neuroscience
- Developmental Biology
Background:
- Previous studies established light-induced retinopathy (LIR) in rats exposed to bright light after eye opening (P14-P34).
- LIR severity correlates with exposure duration and onset age, progressing in acute and chronic phases.
- A two-step degenerative process for LIR was suggested, with severity increasing over time post-exposure.
Purpose of the Study:
- To investigate if bright light exposure before eyelid opening (P0-P14) causes measurable retinal damage.
- To test the hypothesis that pre-eye opening light exposure leads to chronic LIR despite a non-detectable acute phase.
Main Methods:
- Neonatal rats were exposed to a bright luminous environment from birth (P0) to P14.
- Retinal structure and function were evaluated at P30 and P60.
Main Results:
- No significant LIR damage was observed at P30 in rats exposed from P0-P14.
- Significant functional anomalies were detected at P60, with relative preservation of retinal ultrastructure.
- Results indicate a slow degenerative process initiated by postnatal light exposure even with closed eyelids.
Conclusions:
- Postnatal bright light exposure prior to eyelid opening can induce a delayed, chronic form of light-induced retinopathy (LIR).
- Functional deficits in the retina may occur later in development, even without apparent acute structural damage.
- This highlights the vulnerability of the developing retina to environmental light stimuli before full visual system maturation.
Abstract:
In a previous study we showed that juvenile rats exposed, for various durations of time, to a bright luminous environment between P14 (eye opening) and P34 developed a light-induced retinopathy (LIR), the severity of which depending on the duration of exposure as well as the age of the rat at the onset of exposure. Our study also revealed that the severity of the LIR increased as the time elapsed between the cessation of exposure and the structural/functional evaluation increased, suggesting that the LIR degenerative process proceeded in two distinct steps namely, an initial (rapid) acute phase that was followed by a (slower) chronic phase. In view of the above, the purpose of the present study was to reinvestigate previous claims suggesting that exposure to bright light prior to eyelid opening had no measurable consequences on the retinal structure and function; the claim being that despite a non-detectable acute phase, bright light exposure prior to eyelid opening could nonetheless yield a significant retinopathy during the chronic phase of development of LIR. In order to test our hypothesis, neonatal rats were raised in a bright luminous environment from birth to P14. At P30, analysis of the results obtained from rats exposed between P0-P14 did not reveal, as previously acknowledged by others, significant LIR damages. However, results obtained at P60 disclosed significant functional anomalies with relative sparing of the retinal ultrastructure. Our results confirm that, in spite of closed eyelids, postnatal exposure to bright environment did trigger a slow degenerative process.
