What does a blind eye look like in a rat? - briefly
In a rat, a non‑functional eye presents a cloudy, opaque cornea and a contracted, atrophic retina. The pupil is often absent or filled with fibrous tissue, giving the eye a whitish‑yellow appearance.
What does a blind eye look like in a rat? - in detail
A blind eye in a laboratory rat presents with distinct external and internal characteristics that differentiate it from a functional eye.
Externally, the orbit may appear smaller because the globe lacks the normal turgor provided by intra‑ocular pressure. The cornea often becomes cloudy, ranging from a faint haze to a dense opacity that obscures the pupil. The anterior chamber may be shallow, and the iris can appear atrophic, sometimes reduced to a thin, fibrous ring. In many cases, the eyelids close more tightly, and the animal may show reduced blinking or an abnormal squint.
Internally, histological examination reveals several consistent changes:
- Retinal degeneration: Photoreceptor layers are thinned or absent, with loss of outer nuclear layer cells. Remaining retinal tissue may be replaced by glial scar tissue.
- Absence of optic nerve fibers: The optic nerve may be severely reduced in diameter, showing demyelination and axonal loss.
- Vitreous liquefaction: The vitreous body often becomes more gelatinous, sometimes replaced by fibrotic tissue.
- Choroidal atrophy: The vascular layer thins, reducing blood supply to the outer retina.
- Corneal ulceration or stromal scarring: Chronic exposure leads to epithelial breakdown and stromal opacity.
Functional assessment confirms the lack of visual response. Pupillary reflexes are absent; the pupil does not constrict to light. Behavioral tests, such as the visual placing reflex, show no response when the animal’s head is lowered toward a surface.
Typical etiologies for such an eye include congenital anophthalmia, traumatic enucleation, severe intra‑ocular infection, or experimental induction of blindness through optic nerve transection. Regardless of cause, the described morphological features reliably indicate a non‑functional ocular organ in the rat.