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Pigmented vs. Non-Pigmented Rodents
Learn the key differences between pigmented and albino rodents in ocular preclinical studies. Compare anatomy, physiology, and model suitability to select the right rodent strain for your research.
What’s the Difference?
Choose pigmented rodents (e.g., C57BL/6 mice or Brown Norway rats), when drug-melanin binding is critical to your compound’s mode of action, or you’re performing a laser-based model, such as laser-induced CNV.
Choose non-pigmented (albino) rodents (BALB/c mice, or Sprague-Dawley rats), when you need to avoid melanin sequestration, or are running phototoxicity models. The lack of melanin in these models also leads to higher retinal drug exposure and faster clearance, which can be important in PK studies, however, they don’t mix well with laser-based models.
Why Does Pigmentation Matter?
Drug Distribution & Half-Life: Many ophthalmic drugs bind ocular melanin. In pigmented eyes, this can prolong retention in uveal and retinal tissues and alter apparent exposure, whereas in albino eyes there’s little to no sequestration. Regulatory agencies recommend selecting pigmented vs. albino rodents based on a compound’s melanin binding.
Laser & Light Studies: Pigment absorbs visible/near-infrared laser energy, so pigmented eyes require less energy to achieve the same photocoagulation effect which is useful in laser-based models. On the contrary, albino eyes can be more vulnerable to certain light damage paradigms.
Choosing the Right Model for Your Study:
| Feature | Pigmented | Non-Pigmented |
|---|---|---|
| Melanin content | High | Low |
| Drug-melanin binding | Yes | Minimal |
| Fundus imaging | More challenging | Easier |
| Light Sensitivity | Lower | Higher |
| Translational Relevance | Closer to human eye | Limited for pigment interactions |
Comparative Anatomy/Physiology
| Feature | Rat | Mouse | Human |
|---|---|---|---|
| Vitreous Volume | 20 – 25 µL | 5 – 10 µL | 3 – 5 mL |
| Cornea | 5 – 6 mm | 3 mm | ~11.5 – 12 mm diameter |
| Baseline Awake IOP | ~10 – 20 mmHg | 10 – 22 mmHg | ~15 – 16 mmHg |
| Retina | Holangiotic (vessels radiate from optic disc) | Holangiotic | Holangiotic |