Why are a rat's eyes stuck together? - briefly
Rats are born with fused eyelids, a condition referred to as «congenital eyelid adhesion» that shields the immature eyes. The membranes separate during growth, permitting normal vision.
Why are a rat's eyes stuck together? - in detail
Rats possess a thin upper and lower eyelid that meet at the medial and lateral canthi. A translucent third lid, the nictitating membrane, slides horizontally across the eye surface. During normal development the eyelids remain closed for the first 10 – 14 days, forming a sealed environment that protects the cornea while the visual system matures. After this period the lids separate, allowing the animal to open its eyes.
Physiological adhesion occurs when tear film components—lipid secretions from the Meibomian glands, aqueous fluid from the lacrimal gland, and mucins from conjunctival goblet cells—accumulate along the lid margins. Minor drying or excess mucus can cause the margins to adhere temporarily. Grooming behavior often resolves such adhesion without intervention.
Pathological adhesion may result from:
- Bacterial, fungal, or viral conjunctivitis producing purulent discharge that hardens between lids.
- Trauma that damages the eyelid margin, leading to scar tissue and permanent adherence.
- Nutritional deficiencies, particularly vitamin A, causing keratinization of the conjunctiva and reduced tear production.
- Congenital malformations such as ankyloblepharon, where lids are fused by fibrous tissue at birth.
- Chronic inflammatory conditions (e.g., allergic dermatitis) that thicken the skin and promote sticking.
Treatment depends on the underlying cause. Gentle moistening with sterile saline can separate mildly adhered lids. Antimicrobial eye drops address infectious agents. Surgical correction is required for congenital fusion or scar-induced ankylosis. Nutritional supplementation restores normal tear film composition in deficiency cases.
Preventive measures include maintaining a clean habitat, providing balanced nutrition, and monitoring for signs of ocular discharge. Regular veterinary examinations detect early inflammatory changes before permanent adhesion develops.