It’s an uncertain world but there’s one thing you can bet the bank on: Mittens will resist being medicated. Signs of a pet cat suffering can be taken as indicative that you will too.
Persians, Himalayans and other brachycephalic “pug” breeds may seem fluffy and docile, but they have fangs and claws, and sadly, they’re also particularly prone to a mysterious condition called feline corneal sequestra, or “black eye lesion” disease.
The condition also occurs in other predisposed breeds, including the Sphynx, even though its face isn’t brachycephalic – it isn’t pushed in.
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A Sphynx cat at a show. This breed can get the disease even though its faced isn’t pushed in. Credit: Vadim Ghirda/AP
A Sphynx cat at a show. This breed can get the disease even though its faced isn’t pushed in. Credit: Vadim Ghirda/AP
Now a discovery by Israeli researchers sheds new light on this strange disease, which appears as a dark, spreading stain in the cat’s eye. Iron and bromine were detected in the diseased part of corneas but not in the normal control corneas analyzed, Oren Pe’er, Lionel Sebbag and Ron Ofri reported last month in the journal Veterinary Ophthalmology.
Though their paper is called “The Role of Trace Elements in the Formation of Feline Corneal Sequestra,” the researchers do not purport to know exactly what that role is. The study does not establish whether iron and bromine cause the lesion, contribute to its development or accumulate because of tissue damage.
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A black eye lesion. Iron and bromine were detected in the diseased part of the cornea. Credit: Oren Pe’er
A black eye lesion. Iron and bromine were detected in the diseased part of the cornea. Credit: Oren Pe’er
So the cause of black eye remains unknown; the study merely identifies iron and bromine’s presence in sequestral tissue and raises questions about their possible involvement in the disease process.
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A Himalayan cat, which is predisposed to the disease. Credit: Cindy Ching/Shutterstock
A Himalayan cat, which is predisposed to the disease. Credit: Cindy Ching/Shutterstock
Cat owners need to know about this condition because it’s usually painful and, if untreated, the lesion may progressively deepen within the cornea. Some cats develop sequestra in both eyes, either simultaneously or at different times, and advanced lesions may leave your cat blind as a bat.
What should the kitty owner be on the lookout for? A discoloration of the eye ranging in color from reddish to light brown to ebon black. “We don’t know what gives the color,” Pe’er says. Previous studies have investigated several possible sources of this pigmentation, including iron, melanin and porphyrins, but the exact origin remains unresolved, he adds.
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Two Sphynxes rubbing their non-brachycephalic noses. Credit: PuppetMasteX/Wikimedia Commons
Two Sphynxes rubbing their non-brachycephalic noses. Credit: PuppetMasteX/Wikimedia Commons
Feline herpesvirus-1 has been proposed as one of several possible factors associated with corneal sequestra, alongside chronic corneal irritation, genetic predisposition and abnormalities to the tear film – the eye’s super-thin liquid outer layer. But the exact cause remains unclear.
“The new findings raise the possibility that iron- and bromine-associated biochemical processes may be involved in the tissue changes seen in sequestra, including oxidative damage and stromal degeneration,” Pe’er says. “Whether these elements contribute to the disease or accumulate as a consequence of tissue injury remains unknown.”
Absent knowledge on causation, the key treatment for black eye remains surgical removal of the dead tissue, Sebbag says.
He adds that possibly more than one cause or compound may underlie the disease, which is exactly the sort to give cat owners the nightmare of dilemma. Which is – take him or her to the vet, causing suffering and pain to everybody involved but hopefully help; or steer clear of the vet to spare the stress but possibly causing the little darling more suffering. Might the condition pass on its own?
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If you notice symptoms, you definitely want to take your little friend to a doctor within a week. Credit: Oren Pe’er
If you notice symptoms, you definitely want to take your little friend to a doctor within a week. Credit: Oren Pe’er
No, not normally. In isolated cases, the eye heals itself, sloughing off the necrotic tissue spontaneously. The process, if it happens at all, can take months. But in the meantime, Mittens is hurting. “The lesion can get deeper and harder,” Sebbag notes.
So at what point should we take our furry friend to the vet? Basically, when we see the lesion, but it isn’t a drop-everything-and-rush situation, Sebbag says. “The condition progresses slowly. It won’t progress to perforation of the eye or blindness within 24 hours,” he advises, but you definitely want to take your friend to the doctor within a week.
Note that not all cats clearly demonstrate suffering. Some may rock on for a while, but you don’t want the lesion to get worse.
Why are brachycephalic cats more prone? Pe’er and Sebbag note that one reason could be that pushed-in facial structure. Persian and Himalayan cats were bred for prominent eyes and relatively large eyelid openings, which unhappily increases the risk to their corneas. Abnormalities of the tear film and reduced corneal sensitivity may further compromise the eye’s surface.
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An Exotic Shorthair kitten with the flat-faced brachycephalic look. Credit: Sue Thatcher/Shutterstock
An Exotic Shorthair kitten with the flat-faced brachycephalic look. Credit: Sue Thatcher/Shutterstock
Why some cats heal and some don’t remains unknown. Future studies will be needed to determine where iron and bromine are located within the lesion and whether they contribute to tissue damage or are a consequence of it.
Ultimately, understanding these mechanisms could help identify new therapeutic approaches beyond surgery, Pe’er says.
Ahead of developing, one day, eyedrops or some less invasive treatment, how does the operation go? Gingerly. The feline cornea is about half a millimeter thick, and the vets operate under a microscope, removing the sequestrum while preserving as much healthy corneal tissue as possible. When a sequestrum extends deep, its removal may leave a substantial defect that requires additional structural support, using a graft or another reconstructive technique for the cornea.
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An Exotic Shorthair, alas, susceptible to lesions because of the huge eyes Credit: Pixel-Shot/Shutterstock
An Exotic Shorthair, alas, susceptible to lesions because of the huge eyes Credit: Pixel-Shot/Shutterstock
The study included nine cats with corneal sequestra, representing 11 affected eyes because two cats had it on both sides, as well as four control cats with clinically normal corneas collected postmortem, Pe’er says. In the samples analyzed, neither bromine nor iron was detected in the control corneas, whereas both elements were detected in sequestral tissue.
Is that a big enough sample size? Pe’er acknowledges that the sample was small, reflecting the difficulty of obtaining surgically excised corneal tissue suitable for analysis, but statistically significant differences were identified for both iron and bromine. So, yes.
The bottom line is that the findings don’t show cause but raise important questions about the biology of the disease. What can you do in the meantime? If you notice a new brown or black spot in Mittens’ eye, don’t wait for any caterwauling but human up and take the cute little beast to the vet.