Definition
The scraping away or denuding of the corneal surface epithelium (clear outer layer) of the eye.
Clinical Signs
- Eye pain (noticed as squinting).
- Excessive porphyrin (rust colored) tearing involving one eye.
- Bleopharospasm (excessive blinking of one eye) if the abrasion is large or presenting signs are delayed.
*Note: for information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.
Etiology
Like humans, the rat’s cornea has five layers. An abrasion to the cornea affects only the superficial epithelium and does not involve the stroma or basement membrane.
Abrasions to the cornea’s surface can be caused by exposure to a loss of moisture, scrapes from foreign bodies (e.g., ingrown eyelash, wood shaving type litter), or fighting.
A rat’s eyes being normally exophthalmic (prominent, protruding) can increase their risk of injury to the eye.
Corneal abrasion may also occur in rats during prolonged surgical procedures, or with neurological impairments in which the eyelid cannot be closed voluntarily. It is therefore important to keep the rat’s eyes lubricated under these types of conditions.
When treated appropriately the healing of minor abrasions generally start to occur within 24-48 hours. Where large, deep or more extensive abrasions involving the stromal layer of the cornea are involved the risk of complications is significant. Healing can occur; however, scar tissue may form resulting in the loss of further visual acuity for the rat. Without appropriate treatment, or where treatment is delayed, complications such as ulceration and infection can potentially involve the entire eye. In extreme cases prolapse of the iris, herniation of Descemet’s membrane (descemetocele), perforation, deep scarring, glaucoma, blindness, and/or loss of the eye can result.
Figure
Case History of Corneal Abrasion
- Fig. 1: Corneal abrasion right eye in 26-month-old male rat (Zero)
Diagnostics
Use of ophthalmoscope to view eye surface, anterior chamber, vitreous, and retina.
Use of fluorescein stain, with examination by portable slit lamp or Wood light, to help identify corneal surface disruption.
Treatment
The treatment of a corneal abrasion is primarily directed at promoting healing and relieving pain.
Use of anti-infective agents will depend upon extent of injury.
Topical ophthalmic agents (e.g., Bacitracin/Polymyxin B, or a fluoroquinolone, or Gentocin, or tobramycin) may be prescribed by the veterinarian.
The application of topical anesthetics, for corneal abrasions, are not recommended as they can retard epithelial healing and inhibit natural blinking reflex.
*Note: ophthalmic corticosteroids are also not recommended as they have a tendency to promote fungal growth.
For information on ophthalmic agents refer to the Rat Medication Guide.
Nursing Care
- Apply a warm moist compress to the eye for comfort if the rat will allow.
- Apply any antimicrobial ointments or drops your veterinarian may prescribe.
- Provide clean bedding daily while the eye is healing.
- Keep nails clipped to prevent the rat from accidentally scratching eye with long pointed nails.
- In the event there is dried or excess drainage from the eye, clean with a moistened cloth using warm water or normal saline.
- Contact veterinarian if any of the following are observed: increased swelling, redness, or signs of pain.
Outcome
- Cornea heals without complication
- Cornea appears clear
- Pain relieved
Prevention
- While corneal abrasions cannot always be prevented, ensuring your pet rat has a safe environment to live in and play in will reduce the risk of sustaining injury.
