Hypopyon and Lipid Flare in Dogs
An inflammatory breakdown of the blood-aqueous barrier that allows for entry of blood cells into the front (anterior) chamber of the eye, further allowing for an accumulation of white blood cells in this this chamber, is characteristic of a condition known as hypopyon. Chemoattractants, the chemical substances that influence the migration of cells, can act as a conveyor for this cellular movement. The cells often settle in place because of gravity, forming a fluid line in the lower front chamber of the eye.
Lipid flare, on the other hand, resembles hypopyon, but the clouded appearance of the anterior chamber is caused by a high concentration of lipids (the fatty substance in the cells) in the aqueous humor (the thick watery substance between the eye's lens and cornea). It requires a breakdown of the blood-aqueous barrier and concurrent hyperlipidemia (an elevation of lipids in the blood stream) to occur. There is no age, gender or breed predilection.
- White to yellow opacity within the anterior chamber
- May be an accumulation of cells in the lower area, or it may completely fill the anterior chamber
- Concurrent ophthalmic signs can include:
- Blepharospasm (twitching of the eye)
- Epiphora (excessive tear production)
- Diffuse corneal swelling
- Aqueous flare
- Miosis (constriction of the pupil of the eye)
- Swelling of the iris
- Vision loss/blindness
- Diffuse milky appearance of the anterior chamber
- Usually obscures visualization of structures within the eye
- Concurrent ophthalmic signs may include:
- Vision loss
- Mild blepharospasm (twitching)
- Mild to moderate diffuse corneal swelling
Any underlying condition which causes uveitis – inflammation of the middle layer of the eye – can result in hypopyon. Most commonly, hypopyon is associated with severe forms of uveitis, but hypopyon can also result from tumor cell accumulation in cases that involve ocular lymphoma (eye tumors).
Lipid flare often results from a condition of hyperlipidemia (raised or abnormal levels of lipids – the fatty substance of the bloodstream – in the blood stream), and concurrent breakdown of the blood-aqueous barrier (due to uveitis). Hyperlipidemia may also destabilize the blood-aqueous barrier directly. High levels of lipids in the circulating blood following a meal (postprandial lipemia) may occasionally result in the appearance of lipemic aqueous if uveitis is present.
Your veterinarian will perform a thorough physical and ocular examination on your dog, taking into account the background history of symptoms and possible incidents that might have led to this condition.
Hypopyon may be diagnosed by the presence of fibrin (the protein end product of coagulated blood) in the anterior chamber – generally forms an irregular clot, not a ventrally located horizontal line.
Lipid flare will need to be differentiated from severe aqueous flare, which does not appear as milky/white as lipid flare. Dogs that are affected with severe aqueous flare generally exhibit much more ocular pain than animals with lipid flare.
Diffuse corneal edema, a severe corneal edema, may be confused with anterior chamber opacity, but corneal stromal (connective tissue) thickening, keratoconus (degenerative non-inflammatory disorder of the eye), and corneal bullae (fluid-filled blister) are more typically noted with diffuse corneal edema than with hypopyon or lipid flare.