Cherry eye
Cherry eye is a disorder of the nictitating membrane (NM), also called the third eyelid, present in the eyes of dogs and cats.<ref name="autogenerated2000">Gelatt, K. N. (2000). Essentials of Veterinary Ophthalmology. Baltimore: Lippincott Williams & Wilkins.</ref> Cherry eye is most often seen in young dogs under the age of two.<ref name="autogenerated2001">Gelatt, K. N. (2001). Color Atlas of Veterinary Ophthalmology. Baltimore: Lippincott Williams & Wilkins.</ref> Common misnomers include adenitis, hyperplasia, adenoma of the gland of the third eyelid; however, cherry eye is not caused by hyperplasia, neoplasia, or primary inflammation.<ref name="autogenerated1">Slatter, D. (2001). Fundamentals of Veterinary Ophthalmology: Third Edition. Philadelphia: W.B. Saunders Company.</ref> In many species, the third eyelid plays an essential role in vision by supplying oxygen and nutrients to the eye via tear production.<ref name="seniorpetproducts1">Robledo, E. P., Serrano, R. D., Sanches, N. Q., & Ramirez, A. M. (n.d.). "Effect of Pet Vision in a Canine with Keratoconjunctivitis Sicca (Dry Eye) Template:Webarchive". Retrieved 1 December 2012.</ref> Normally, the gland can turn inside-out without detachment.<ref name="autogenerated1"/> Cherry eye results from a defect in the retinaculum which is responsible for anchoring the gland to the periorbita. This defect causes the gland to prolapse and protrude from the eye as a red fleshy mass.<ref name="autogenerated1"/> Problems arise as sensitive tissue dries out and is subjected to external trauma<ref name="autogenerated1"/> Exposure of the tissue often results in secondary inflammation, swelling, or infection.<ref name="autogenerated1"/> If left untreated, this condition can lead to dry eye syndrome and other complications.<ref name="seniorpetproducts1"/>
DescriptionEdit
Cherry eye is most common in young dogs, especially breeds such as Beagle, Cavalier King Charles Spaniel, English Bulldog, Lhasa Apso, Shih Tzu, West Highland White Terrier, Pug, Bloodhound, American Cocker Spaniel, and Boston Terrier.<ref name="autogenerated2000"/> Cherry eye is rare in felines, but can occur. This defect is most common in the Burmese breed of felines.<ref name="autogenerated3">Griffin, C., & Glaze, M. B. (2008). "Eyes and Ears". St John U.S.V.I. November 3–6. International Veterinary Seminars.</ref> A similar condition exists in dwarf lop-eared rabbits, which occurs in the harderian gland. Similar surgical treatment is necessary.<ref name="autogenerated1"/>
There is likely a complicated and multigenic component involving genetic risk factors.<ref>Edelmann, M. L., Miyadera, K., Iwabe, S., & Komáromy, A. M. (2013). Investigating the inheritance of prolapsed nictitating membrane glands in a large canine pedigree. Veterinary ophthalmology, 16(6), 416–422. https://doi.org/10.1111/vop.12015</ref> Some breeds are considered to be more susceptible to its development than others, including the Bulldog, Boston Terrier, Bull Terrier, Lhasa Apso, Cocker Spaniel, St. Bernard, Shar-pei, Shih Tzu and Poodle <ref>"Common Ocular Problems of Shih Tzu Dogs". Canadian Veterinary Journal, Volume 33, 392.</ref> The NM contains many glands which merge and appear as a single gland.<ref name="autogenerated80">Sarma, B. (2010). "Cherry Eye in Dogs. Intas Polivet, 11, pp. 80–81.</ref> Typically, glands secrete tears for lubrication of the cornea.<ref name="autogenerated80"/> Lack of anchoring allows the gland to flip up, causing the gland to prolapse. Symptoms include a visible fleshy mass, abnormal tear production, and a discharge or drainage from the eye. Cherry eye is typically diagnosed by examination of the conjunctiva and nictitating membrane.<ref name="autogenerated2001"/> The most obvious symptom of cherry eye is a round fleshy mass in the medial canthus of the eye, similar in appearance to the fruit it is named for.<ref name="autogenerated80"/> This mass may be unilateral or ‘’bilateral’’. Both eyes may develop cherry eye at different times in the animal's life.<ref name="autogenerated2000"/> Other symptoms of cherry eye include drainage from the eye and abnormal tear production. Initially, cherry eye results in overproduction of tears, but eventually changes to unsubstantial tear production.<ref name="autogenerated2000"/>
TreatmentEdit
Non-surgicalEdit
Cherry eye, if caught early, can be resolved with a downward diagonal-toward-snout closed-eye massage of the affected eye or occasionally self-corrects alone or with antibiotics and steroids.<ref name="autogenerated1"/> Sometimes the prolapse will correct itself with no interference, or with slight physical manual massage manipulation as often as necessary coupled with medication.<ref name="autogenerated1"/>
SurgicalEdit
Surgery is the most common means of repairing a cherry eye. Surgery involves gland replacement, not excision, by anchoring the membrane to the orbital rim or using a pocket technique.<ref name="autogenerated1"/> In severely infected cases, preoperative antibiotics may be necessary by means of antibiotic eye ointment.<ref name="autogenerated1"/> Removal of the gland was once an acceptable treatment, and made the eye appear completely normal.<ref name="autogenerated3"/> Despite cosmetic appeal, removal of the gland reduces tear production by 30 percent. Tear production is essential in maintaining and protecting the eye from the external environment.<ref name="autogenerated3"/> Reduced tear production is especially problematic in breeds of animals predisposed to Keratoconjunctivitis sicca (KCS), also known as dry eye syndrome. With surgeries performed in this manner, KCS often results later in life.<ref name="autogenerated1"/>
KCS is not common in dogs, affecting one per cent of the dog population.<ref>Blount, W. (n.d.). "Dry Eye: More formally known as Keratoconjuntivis Sicca or KCS". Retrieved 1 December 2012.</ref> KCS is a chronic degenerative conjunctivitis that can lead to impaired vision and blindness.<ref name="autogenerated2001"/> KCS has a wide array of causes including drug toxicity, cherry eye, previous surgery, trauma, and irradiation.<ref name="autogenerated2001"/> KCS can be treated, but treatment often spans the entirety of the animal's life.<ref name="autogenerated2001"/>
In contrast to this, several replacement surgical procedures exist to remedy cherry eye.<ref name="autogenerated2001"/> Replacement of the gland results in lower instances of dry eye later in life.<ref name="intranictitans228">Plummer, C., Kallberg, M., Gelatt, K., Gelatt, J., & Barrie, K. P. (2008). "Intranictitans tacking for replacement of prolapsed gland of the third eyelid in dogs". Veterinary Ophthalmology, pp. 228–233.</ref> Surgery types are broken into two groups: anchoring procedures and pocket/envelope procedures.<ref name="autogenerated2000"/> At least 8 surgical techniques currently exist.<ref name="autogenerated2000"/> In anchoring procedures, the prolapsed gland must be sutured to the periorbital fascia, the sclera, or the base of the third eyelid.<ref name="autogenerated3"/> In contrast, pocket procedures involve suturing healthy tissue around the prolapsed to enclose and secure it.<ref name="autogenerated3"/> Each of these techniques may be performed with an anterior or superior approach, depending on which direction of suturing will cause the least complications to the eye.<ref name="autogenerated3"/>
Anchoring methodEdit
Originally, the anchoring method involved suturing the gland to the globe. This method was superseded over time due to the risky and difficult nature of the surgery, along with a high rate of recurrence.<ref name="autogenerated1"/> Anchoring approaches from posterior may disrupt normal fluid excretion.<ref name="intranictitans228"/> Subsequently, an anterior approach was introduced.<ref name="intranictitans228"/> Disadvantages of anchoring techniques include restricted mobility of third eyelid, which is essential in the functions of fluid distribution and self-cleaning.<ref name="intranictitans228"/> New procedures are currently being explored to allow tacking of the NM without restricting movement of the third eyelid.<ref name="intranictitans228"/> Few studies compare results of surgeries, therefore choosing a procedure is a matter of preference.<ref name="intranictitans228"/>
Envelope/pocket methodEdit
The envelope method, often called the pocket technique, requires suturing of tissue around the prolapse, encasing it in a layer of conjunctiva.<ref name="autogenerated3"/> Pocket techniques are easiest for doctors to learn.<ref name="autogenerated2000"/> Pocket methods also have anterior and posterior versions. Posterior suturing techniques are the most commonly used because they cause the least complications, with no alterations in tear production.<ref name="intranictitans228"/> Surgery should only be attempted by experienced surgeons.<ref name="autogenerated1"/> Inappropriate surgical techniques can result in many complications including cysts on the eye.<ref name="intranictitans228"/>
PrognosisEdit
Without treatmentEdit
Previously, treatment was thought optional until the role of NM was fully understood.<ref name="autogenerated2000"/> The NM gland is responsible for 40–50% of tear production.<ref name="ophthalmologists1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> If exposed for extended periods of time, the gland is at risk for trauma, secondary infection, and reduced tear production.<ref name="ophthalmologists1"/> Many complications can arise if left untreated: early closed-eye massage manipulation is recommended to prevent inflammation .<ref name="autogenerated1"/>
Post treatmentEdit
Postoperative treatment includes antibiotic eye ointment three times daily for two weeks.<ref name="autogenerated3"/> It is possible to have a relapse of the gland after surgery and require multiple surgeries.<ref name="autogenerated1"/> With treatment, it is possible for animals to live a normal life.
See alsoEdit
- Conjunctivitis, commonly referred to as pink eye