14 Microphthalmia is a rare condition in kittens, but often these globes have multiple anomalies (Figure 14.1). Breeds affected include the Domestic Shorthair and Persian. Congenital cataracts are often present. Vision is usually present unless the cataract formation is advanced. Generally there is no treatment. Figure 14.1 (A) Microphthalmia affecting both eyes in a kitten. The microphthalmia causes the exposure of the dorsal sclera within the palpebral fissure. (B) Symblepharon, or adhesion of the conjunctiva to the eyelids, the cornea, and to itself, in this kitten is obscuring visualization of a normal‐sized globe. Proptosis or the traumatic displacement of the eye from the orbit is a serious disease in the cat (Figure 14.2). It is usually associated with considerable head trauma, and often mandibular symphysis fractures are present. Orbital hemorrhage can compound the globe luxation. The cornea undergoes rapid desiccation with malacia, and perforation is likely if not addressed promptly. Optic nerve damage (extending to involve the optic chiasm) can be a complication from the trauma with stretching and inflammation. Damage to the contralateral optic nerve can result in blindness of the fellow eye. Figure 14.2 (A) Marked proptosis in a cat of several hours duration. Note the marked drying and desiccation of the unprotected cornea. (B) Traumatic proptosis in another cat. The pupil is dilated and unresponsive to light. The prognosis for successful globe replacement and return of vision is very poor. Replacement of the globe and short‐term complete temporary tarsorrhaphy should be performed as soon as possible. The prognosis for the return of vision in cats is poor. The clinical signs and treatment of orbital inflammations in cats are similar to those in dogs. As the orbital space is more limited in cats, orbital inflammations rapidly cause protrusion of the nictitans, conjunctival hyperemia, localized orbital pain, and limited exophthalmos (Figure 14.3). Both bacteria and fungus (Penicillium sp.) have been isolated. Treatment is the same as for the dog. Figure 14.3 (A) Orbital cellulitis in a cat presented as exophthalmos, swollen eyelids, and secondary iridocyclitis (miosis). The signs for orbital cellulitis in cats are much more subtle than in the dog. (B) Another example of orbital cellulitis in a cat. Note the exophthalmos, conjunctival swelling and hyperemia, and the dull, dry central cornea (the result of exposure). Orbital neoplasia occurs in cats, but reports are less frequent than in dogs. About 90% are malignant, and about 60% of these tumors are squamous cell carcinomas (Figure 14.4). Many of the tumors arise from the conjunctiva, nictitating membrane, or eyelids and invade the orbit from there. Others arise in the nasal passages and invade outward into the orbit. Orbital lymphosarcoma is a common orbital tumor in cats. It is unilateral or bilateral. Figure 14.4 (A) Orbital neoplasms are often squamous cell carcinomas that arise from the eyelids and conjunctiva, as in this cat, and subsequently invade the orbit. (B) This cat had a neoplasm in the ventral floor of the orbit that extended from the oropharynx and resulted in dorsal deviation of the globe and elevation of the nictitans. (C) Orbital extension of squamous cell carcinoma from the nasal passages resulted in exophthalmos in this cat. (D) Orbital lymphoma in this cat resulted in exophthalmos, deviation of the globe off its axis, and exposure. Impairment of the optic nerve and the optic chiasm resulted in mydriasis and blindness. Diseases of the feline eyelids are similar to those that occur in the dog, but inherited defects are far less frequent. In contrast to the usual benign lid tumors in the dog, lid tumors in cats are usually highly malignant and histologic examination of the surgical margins is recommended. Eyelid agenesis or lid coloboma is an infrequent disorder in kittens, affecting one or both eyelids (Figure 14.5). The lid coloboma almost always involves the lateral aspects of the upper lid, less commonly the lateral canthus and lateral lower eyelid. The lid margin and the conjunctiva (palpebral and fornix) are often missing. The edge of the affected area can contact the bulbar conjunctiva and cornea and produce focal irritation and inflammation. Figure 14.5 (A) Eyelid agenesis is one of the most frequent congenital lid defects in the cat. In this young cat the eyelid agenesis affects both lateral upper eyelids. The lack of lid margin and trichiasis cause corneal and conjunctival irritation that necessitates surgical correction. (B) Same cat as in part A in a closer view of the right eye. Note the lack of lateral upper eyelid skin, margin and conjunctiva, and the trichiasis. Keratitis is present in the exposed and irritated dorsolateral cornea. (C) Same cat as in part A and B immediately postoperatively following surgical reconstruction (Dziezyc–Millichamp modification of the Roberts–Bistner technique). (D) Another cat with eyelid agenesis immediately following repair with a modified lip‐to‐lid procedure. Eyelid agenesis can be accompanied by other anomalies of the globe including iris defects (persistent pupillary membranes, iris colobomas), cataracts, and colobomas of the optic nerve head. Clinical vision is usually normal. Both heredity and in utero viral infections have been suggested causes. Eyelid restoration with a myocutaneous pedicle graft from the lower eyelid or the lateral commissure of the mouth is the most common surgical therapy. Structural abnormalities of the eyelids (i.e., entropion and ectropion) are infrequent in cats, but entropion occurs in the Persian and other brachycephalic breeds, in tom cats of any breed that were neutered later in life, or in an aged or infirm cat that has had significant weight loss or atrophy (Figure 14.6). Cicatricial entropion can follow eyelid surgery, eyelid lacerations, and prolonged blepharitis. Once the cutaneous portion of the eyelid margin contacts the cornea and/or conjunctiva, blepharospasm develops and can worsen the entropion (spastic entropion). Entropion in cats most commonly affects solely the lower eyelid. Figure 14.6 (A) Entropion or the inversion of the eyelid margin has resulted in blepharospasm and keratitis from the lid–corneal contact. (B) Same cat as in part A immediately following surgical correction using the Hotz–Celsus technique. Blepharitis or inflammation of the eyelids in cats primarily involves the dermis alone, with deep involvement (i.e., meibomianitis) occurring rarely (Figure 14.7). Figure 14.7 (A) Blepharitis associated with Demodex in a cat. Note the multiple sites of involvement (e.g., nose, forehead, and eyelids). (B) Blepharitis secondary to feline scabies caused by Notoedres in a kitten. These lesions are highly pruritic. (C) Severe bilateral autoimmune blepharitis in a cat. There is a conjunctival pedicle graft on the right cornea covering a keratectomy site where a corneal sequestrum was removed. Eyelid neoplasms are not infrequent in older cats and account for 2% of all feline neoplasia. In contrast to dogs, lid tumors in cats are highly malignant, locally infiltrative, and often require extensive surgery or a combination of therapies (surgical debulking, cryotherapy, radiation, and chemotherapy). The most common tumors are squamous cell carcinoma (36–65%), fibrosarcomas (8%), lymphoma (11%), and adenocarcinomas (7–8%) (Figure 14.8). Figure 14.8 (A) Early squamous cell carcinoma in a white cat. The lesion initially appears resembling an ulcerated wound that fails to heal. (B) Lid squamous cell carcinoma in an aged cat. The tumor has infiltrated the entire lower eyelid and the medial canthus. Biopsy is suggested to confirm the diagnosis before attempting extensive surgery, radiation, and/or cryotherapy. (C) Apocrine hidrocystomas present as single to multiple masses often cystic and containing brown proteinaceous fluids as in this Persian cat. (D) Cutaneous mast cell tumors have been reported in the eyelids of cats. These often appear as areas of focal alopecia. They may be raised, as seen in this cat, or flat. Squamous cell carcinomas (SCC) represent about two‐thirds of the eyelid tumors diagnosed in cats, and occur most commonly in older light‐colored or white cats. They appear as ulcerated to proliferative lesions, most often affecting the eyelid margins and anterior nictitans. Locally invasive, SCC metastasize late. Fibrosarcomas are frequent lid tumors, appearing as a focal nodular mass arising in the subcutaneous tissues and with an ulcerative surface. In young cats, multicentric fibrosarcomas result from the feline sarcoma virus (FeSV). Long‐term prognosis is poor. Lymphoma occurs unilaterally or bilaterally. These masses are subcutaneous or beneath the palpebral conjunctiva. Eyelid and periocular apocrine hidrocystomas have been reported in cats, especially in the Persian and Himalayan breeds. Thought to arise from the apocrine glands along the eyelid margins, they appear as gray, often coalescing, single or multiple cystic masses. Histologically, they are adenomatous, dilated epithelial cysts, and contain brown to tan proteinaceous debris. They are benign; however, recurrence is common. Tear and nasolacrimal disorders in cats are infrequent, but keratoconjunctivitis sicca (KCS) does occur. Nasolacrimal drainage disorders most often occur in the brachycephalic breeds. Epiphora is infrequent in cats and has several causes. In the brachycephalic breeds (Persian and Himalayan), it can be associated with medial lower entropion and lacrimal punctal disorders, and is treated surgically. It is seen in cats with acute or chronic ocular surface disease, especially if there is an infectious etiology (e.g., FHV‐1, Chlamydophila, Mycoplasma). KCS occurs infrequently in cats and most often seems related to chronic blepharoconjunctivitis associated with feline herpesvirus (FHV‐1) infections (Figure 14.9). Schirmer’s tear tests values are normally a little lower in cats than dogs, but dry eyed cats will have significant reductions in aqueous tear production. Clinical signs of feline KCS are more subtle than dogs, and include conjunctival and nictitans hyperemia, mild and diffuse superficial keratitis with vascularization but little corneal or conjunctival pigmentation. There is usually no ulceration (fluorescein retention), but rose Bengal stain may be retained diffusely (minute foci of degenerating corneal epithelium). Figure 14.9 (A) Early keratoconjunctivitis sicca (KCS) in a cat. Brown ocular discharge is present, the result of ocular surface inflammation. KCS is commonly associated with feline herpesvirus (FHV‐1) infection in cats. Feline KCS is less obvious than in the dog. (B) Chronic nasolacrimal obstruction treated by conjunctivorhinostomy in a cat. The silicone tube within the new bypass to the nose is secured to the medial canthus and nose for several weeks. The cat must wear an E‐collar during the time the tubing is in place. (C) Prolapse of the nictitans gland in a cat. This is an uncommon finding in cats and is seen most often in the Burmese breed. Surgical replacement is recommended to minimize the risk of the development of KCS. FHV‐1 is ubiquitous among domestic and wild cats worldwide. It is estimated that over 80% of domestic cats have been exposed to FHV‐1 by adulthood. Primary infection in cats results in both conjunctival and respiratory infections, often complicated by secondary bacterial infections (Figure 14.10). In kittens less than 12–14 days old, FHV‐1 infections can present as neonatal ophthalmia where infection has developed under the normally closed eyelids. Figure 14.10 (A) Primary feline herpesvirus‐1 (FHV‐1) conjunctivitis in a kitten. Note the copious conjunctival exudates of both eyes. (B) Extensive symblepharon in a kitten following its initial infection with FHV‐1. The palpebral conjunctiva has adhered to the cornea, the conjunctiva of the nictitans, and to itself. In older kittens (at the time of weaning), FHV‐1 can present as an acute serous to mucopurulent conjunctivitis with respiratory signs. The conjunctiva is hyperemic but not generally chemotic. Corneal microdendritic ulcers can be detected with topical fluorescein or rose Bengal stain. Treatment includes topical antibiotics (tetracycline, chloramphenicol, or erythromycin), and systemic supportive therapy. Symblepharon formation, or adhesion of the conjunctiva to itself or other ocular tissues, can be a complication. After recovery from the primary FHV‐1 infection, about 80% of the cats become latent carriers of FHV‐1 and in about 45% of these cats the virus will spontaneously activate and result in recrudescent eye disease. Hence, in most adult cats, ophthalmic FHV‐1 infections are recurrent (Figure 14.11; also Figure 18.29). Stress, the introduction of a new pet, moving, and other disease or immunocompromised states can trigger release of the virus. Some cats, instead of developing the cytolytic form of the herpetic ocular disease, which is the result of active viral replication and cell lysis, will develop an immunopathologic form that manifests with stromal keratitis. Figure 14.11 (A) Recurrent FHV‐1 conjunctivitis in an adult cat. Conjunctivitis with chemosis of the ventral conjunctiva is present. (B) More severe recurrent FHV‐1 conjunctivitis in an adult cat. Marked conjunctival hyperemia and chemosis affect both ventral and dorsal conjunctivae. Chlamydophila psittaci causes pneumonitis and conjunctivitis, most commonly in kittens (Figure 14.12). The respiratory infection is usually mild. The conjunctivitis is characterized by conjunctival hyperemia, chemosis, and serous to later mucopurulent conjunctival exudates. Often one eye and then both eyes are affected. Follicles form on the conjunctival surfaces in chronic infections. Cytology of acute infection can reveal intracytoplasmic inclusion bodies within the conjunctival epithelial cells. Figure 14.12 Chlamydia conjunctivitis in a kitten. The conjunctivitis is mild, and some dried conjunctival discharge is present at the medial canthus. Mycoplasma spp. (Mycoplasma felis and Mycoplasma gatae) also cause conjunctivitis in cats, which can affect one or both eyes (Figure 14.13). The conjunctivitis is characterized by epiphora, conjunctival follicles, chemosis, and formation of pseudomembranes (plaques of thick white exudates). Cytology reveals intracytoplasmic bodies. Figure 14.13 Mycoplasmal conjunctivitis in an adult cat. Note the marked conjunctival hyperemia and swelling, and the pseudomembrane (arrow) in the ventral conjunctiva. Symblepharon is the adherence of conjunctiva to itself or to the cornea. It occurs most often in young cats, and appears related to acute or recurrent FHV‐1 conjunctivitis (Figure 14.14; also Figure 18.29C). Symblepharon appears as conjunctiva adhered to the cornea for varying degrees. Eyelid movements and the depth of the conjunctival fornix can also be compromised. Surgical procedures are available to treat this condition, but recurrent FHV‐1 conjunctivitis can cause the condition to return. Figure 14.14 (A) Symblepharon in a cat associated with FHV‐1. The adherent conjunctiva impairs this kitten’s ability to blink. (B) Symblepharon in a cat involving adhesion of the upper palpebral conjunctival to the lower which obscures the entire globe. Lipogranulomatous conjunctivitis is an unusual inflammatory condition in cats believed to develop from damage to meibomian glands and an inflammatory reaction to liberated glandular secretions (Figure 14.15). The lesions occur in the palpebral conjunctiva adjacent to the eyelid margins and appear as nonulcerated white nodules. They can be quite irritating, but in most cases surgical resection is curative. Figure 14.15 Lipogranulomatous conjunctivitis in an aged cat. The feline cornea is nearly round (vertical diameter 16 mm; horizontal diameter 17 mm), and along with the nictitating membrane is the main tissue visible in the feline palpebral fissure. Very little of the bulbar conjunctiva can be seen in normal cats until the upper eyelid is manually retracted. Although FHV‐1 primarily affects the conjunctiva, the cornea can be involved as well (Figure 14.16). The virus can replicate in and cause lysis of the corneal epithelium. Dendritic or microdendritic corneal ulcers result, which stain poorly with topical fluorescein but fairly well with rose Bengal. Released viral particles from lysed epithelial cells infect adjacent cells and result in enlargement of the superficial ulcer. Figure 14.16 (A) Feline herpesvirus‐1 can also cause corneal ulceration in the cat. Note the very fine dendritic corneal ulcers and the irregular distribution of these micro‐ulcers. (B) Dendritic corneal ulcers associated with FHV‐1 and stained with topical fluorescein and highlighted with a cobalt blue light filter. (C) Dendritic ulcers stained with fluorescein which are expanding into geographic ulcers in this cat. FHV‐1 keratitis can also involve the stroma (Figure 14.17). Studies suggest viral suppression of the local immune response at the time of the initial infection permits access to the stroma. Residual viral antigen in the corneal stroma can elicit a delayed inflammatory response that is not typically ulcerative. Clinical signs include corneal edema and cellular infiltrate, superficial vascularization, and fibrosis. Significant corneal scarring can eventually impair vision. Corneal ulcers are present in some cases. Figure 14.17 (A) Feline herpesvirus‐1 stromal keratitis in a 3‐year‐old cat. Note the stromal edema and scarring with superficial vascularization. (B) Another example of chronic herpetic ocular disease in a cat. Note the corneal stromal vasculature, the conjunctival hyperemia and chemosis, and mild eyelid swelling. Corneal sequestration has several synonyms including corneal black spot, corneal nigrum, corneal mummification, and focal corneal degeneration (Figure 14.18; also Figure 18.29A). It consists of a central or paracentral focal degeneration of the corneal stroma (collagen and fibroblasts), the accumulation of a brown water‐soluble pigment, and a variable surrounding inflammatory response. Although it affects cats of all ages in one or both eyes, the Persian, Himalayan, and Burmese breeds seem predisposed. The cause has not established, but FHV‐1 has been detected in 55–73% of sequestrum keratectomy samples. Figure 14.18 (A) Corneal sequestration and corneal ulceration in a young cat. Note the black plaque in the base of the ulcer. (B) A larger corneal sequestration in a young cat. Note the central black sequestration and the surrounding superficial corneal ulcer. (C) Faint brown pigmentation of the cornea which is the earliest manifestation of sequestrum. (D) Postoperative appearance using a sliding corneoconjunctival graft dorsal of the surgical site. Corneal sequestration appears as a variable shaped, size, and depth, brown to black lesion that may be so dense that slit lamp biomicroscopy cannot accurately estimate the depth of stromal involvement. High frequency ultrasonography (20–35 MHz) can be helpful to assess depth and corneal thickness in those instances. Occasionally, corneal sequestration extends though the entire thickness of the stroma to Descemet’s membrane. Several treatment modalities have been recommended: (i) supportive medical therapy until spontaneous slough; (ii) superficial keratectomy; (iii) superficial keratectomy with palpebral conjunctival graft; and (iv) superficial keratectomy with a sliding corneoconjunctival graft. Recurrence can occur, especially if the sequestration was incompletely excised. Proliferative keratoconjunctivitis occurs most commonly in cats and is characterized by the development of single to multiple inflammatory masses and/or vasculature originating at the limbus (Figure 14.19). The conjunctiva, cornea, and the nictitating membrane are affected. Dermatologic signs of the eosinophilic complex are usually absent. Although the cause has not been resolved, polymerase chain reaction (PCR) results suggest at least 76% of the lesions are positive for FHV‐1 DNA.
Feline Ophthalmology
Diseases of the Orbit
Traumatic Proptosis
Orbital Cellulitis
Orbital Neoplasia
Diseases of the Eyelids
Lid Agenesis
Entropion
Blepharitis
Lid Neoplasia
Diseases of the Tear and Nasolacrimal System
Epiphora
Keratoconjunctivitis Sicca
Diseases of the Conjunctiva
Feline Herpesvirus
Chlamydophila psittaci
Mycoplasmal Infections
Symblepharon
Lipogranulomatous Conjunctivitis
Diseases of the Cornea
Feline Herpesvirus‐1 and the Cornea
Corneal Sequestration
Proliferative Keratoconjunctivitis (Esosinophilic Keratitis)
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