Hypopyon and Lipid Flare in Cats
Hypopyon is the accumulation of white blood cells in the front (anterior) chamber of the eye. An inflammatory breakdown of the blood-aqueous barrier allows for entry of blood cells into this chamber; chemoattractants, 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 cat, 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. Animals 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.
Hypopyon requires aggressive treatment for the uveitis and its underlying cause. Outpatient treatment is generally adequate, but you will need to be aware that there is still a significant chance that your cat will lose its sight. Lipid flare requires treatment for the uveitis, which is usually mild, and any underlying metabolic disorders. If your cat is diagnosed with hyperlipidemia, you will need to change the cat's diet to one that is lower in fat and calories, in order to decrease the amount of fat in the bloodstream. Outpatient treatment, with anti-inflammatory drugs prescribed for home administration, is generally adequate.
Living and Management
Your veterinarian will schedule a check-up for two to three days after the initial treatment. Intraocular (within the eyes) pressure should be monitored to detect secondary glaucoma. The frequency of subsequent rechecks will be dictated by the severity of the disease and your cat's individual response to treatment.
The expected prognosis may depend heavily on what the underlying condition is behind the eye condition. For example, with hypopyon, the prognosis is guarded depending on the underlying disease and response to treatment. With lipid flare, the prognosis is usually good. It generally responds quickly (within 24–72 hours) to moderate anti-inflammatory therapy. However, keep in mind that recurrence and the need for further treatment is possible with lipid flare.