Equine Ophthalmology Flashcards
What are the three primary external layers of the horse’s eye and their characteristics?
Cornea: Clear, protects the eye, aids in refraction
Sclera: White, provides structure
Conjunctiva: Thin, Vascular muscular mucous membrane layer overlaying the sclera
What is the role of the retina in vision?
The retina acts like film in a camera converting light into signals that are sent to the brain for interpretation
What is the role of the tapetum and where is it located?
Tapetum is a reflective layer behind the retina, enhancing light detection photons a second chance to stimulate retinal cells
What is the significance of the corpora nigra in horses?
These are pigmented extensions of the iris that help regulate light entry and reduce glare.
Describe the visual field of a horse, including blind spots.
Horses have a total visual field of 350 degrees, with a 65 degree frontal binocular vision field and a small blind spot behind them.
What are the color vision capabilities of horses?
Horses are dichromatic, meaning they perceive fewer colors than humans , primarily blue and yellow spectrums.
Why is motion section better in horses than detail recognition?
Horses excel at motion detection due to a large number of rods, which are highly sensitive to light and movement.
They have fewer cones, which are responsible for color vision and sharpness, leading to poor visual acuity.
What is conjunctivitis, and what are its signs?
Inflammation of the conjunctiva with signs including redness, recharge, and minimal pain
What factors can cause conjunctivitis in horses?
Bacterial infection
Irritants like wind and dust
Parasites (Habronema)
Tumors and Trauma
What is Squamous Cell Carcinoma and why is it significant?
SCC is the most common ocular tumor in horses, often appearing in areas with such as the conjunctiva, third eyelid or cornea
What are the common treatment fro SCC in horses?
Surgery, cryosurgery, radiation therapy, chemotherapy injections, and immunotherapy with Interferon
How do corneal ulcers develop and what are their symptoms?
Develop due to trauma or infection
Symptoms include pain (tearing and squinting), cloudy appearance.
Will appear when tisanes with fluorescein and blue light
What complication can arise from treating corneal ulcers with steroids?
Steroids can worsen ulcers by inhibiting healing and encouraging deep infection.
How are deep or infected corneal ulcers managed?
Surgical repair if necessary
Frequent medication vis subpalpebral lavage system
Giving antibiotics and antifungals
What is Equine Recurrent Uveitis
Moon Blindness
Inflammation of the uvea
Signs: Painful, red, and cloudy eyes, often with a constricted pupil
Seen in appaloosas
Many causes
