Feline corneal sequestrum: laboratory analysis of ocular samples from 12 cats

Long-term treatment outcomes and risk factors for recurrence in feline corneal sequestrum: 72 cases (2009-2017)

BACKGROUND

This study aimed to evaluate long-term treatment outcomes in feline corneal sequestrum (FCS), compare the recurrence rates between different surgical techniques, identify possible recurrence risk factors and monitor the development of FCS in the contralateral eye.

METHODS

The medical records of 72 cats (79 eyes) with FCS treated between 2009 and 2017 were retrospectively analysed.

RESULTS

The most commonly affected breeds were Persian, domestic shorthaired and Burmesecats. The mean age was 6.9 years. Sixty-five cats (90%) were affected unilaterally. Sixty-six eyes (83%) underwent surgery: keratectomy in 34 eyes (52%) and keratectomy followed by a graft procedure in 32 eyes (48%). Recurrence occurred in 13 out of 66 eyes (19%) at a median of 245 days after surgery. Skull conformation, location of the FCS, type of surgical procedure and concurrent ocular surgery did not significantly affect the recurrence rate. Eighteen cats (27%) developed FCS in the contralateral eye at a median of 635 days after surgery.

LIMITATIONS

Limitations are related to the retrospective nature of the study, the use of telephone follow-up for assessment of recurrence in some cats and the small number of cases.

CONCLUSIONS

Surgical excision had a successful outcome in most cases. The type of surgical procedure and skull conformation did not affect the recurrence rate. One-quarter of the cats developed FCS in the contralateral eye.

Diagnosing Corneal Pigmentation in Small Animals

The transparency of the cornea is critical to its role in transmitting light. Loss of corneal transparency results in visual impairment. Corneal pigmentation results from melanin accumulation in the epithelial cells of the cornea. Differential diagnosis for corneal pigmentation include corneal sequestrum, corneal foreign body, limbal melanocytoma, iris prolapse, and dermoid. These conditions must be excluded to reach a diagnosis of corneal pigmentation. A myriad of ocular surface conditions are associated with corneal pigmentation, including qualitative and quantitative tear film deficiency, adnexal disease, corneal ulceration, and breed-related corneal pigmentation syndromes. Accurate etiologic diagnosis is critical to determining effective treatment.

Genetic Aspects of Corneal Sequestra in a Population of Persian, Himalayan and Exotic Cats

Simple Summary

Corneal sequestrum is a common eye disease in Persian, Himalayan and exotic cats. It is a brown stain on the cornea that can be painful and often requires surgery for full recovery. The cause of this disease is unknown. One hypothesis is that genetic factors influence the disease, but there are no data to support this in the scientific literature. In this study, the influence of genetics on this disease was investigated on the basis of clinical and pedigree data from a cattery. Kittens of some dams in this cattery turned out to have a higher risk of corneal sequestra than kittens of other dams, indicating that genetics indeed play a role. The disease also has a high heritability, which implies that by selecting the right breeding animals, breeders can reduce the risk of corneal sequestra in the offspring. DNA analysis of some of the cats from the cattery could not link the disease to a specific region in the DNA, so it is possible that many different genes in different DNA regions are involved in the development of corneal sequestra.

Abstract

Corneal sequestra are ophthalmic lesions that are remarkably common in Persian, Himalayan and exotic cats. In this study, the genetic aspects of this disease were investigated in a population of cats originating from a single cattery. Odds ratios were calculated for parents with affected offspring. The heritability of (owner-reported) corneal sequestra was estimated with a Markov chain Monte Carlo procedure. Well-phenotyped cases and controls were used for a genome-wide association study. Data from 692 cats originating from the cattery, of which 61 were affected, were used. Cats from two specific mothers had significantly higher odds of developing corneal sequestra, but no significant effect of the fathers was found (after correction for the mothers). The heritability of corneal sequestra was estimated to be 0.96. A genome-wide association study with 14 cases and 10 controls did not reveal an associated chromosomal region. The large effect that genetic factors had on the development of corneal sequestra in this study suggests that selective breeding could be an effective way to reduce the prevalence of this condition in these cat breeds.

Prevalence and characteristics of ocular diseases in Sphynx cats: A retrospective assessment (2012-2021) and comparison with non-Sphynx cats

PURPOSE

To describe the prevalence of ocular diseases in Sphynx cats, and compare disease characteristics with other feline breeds.

METHODS

Medical records of Sphynx cats presented to an ophthalmology referral center between 1/2012 and 4/2021 were examined. Cats of other breeds examined during the same period served as controls.

RESULTS

One hundred ten Sphynx cats were examined during the study period, diagnosed with corneal sequestrum (n = 42 cats), lower eyelid entropion (n = 25), presumed herpetic keratoconjunctivitis (n = 19), conjunctivitis (n = 7), corneal ulcers (n = 6), nasolacrimal duct atresia/obstruction (n = 6), corneal dystrophy (n = 3), eosinophilic keratitis (n = 2), uveitis (n = 2), non-ulcerative keratitis (n = 1), and cataract (n = 1). Corneal sequestrum was significantly more common in Sphynx versus non-Sphynx cats (odds ratio = 8.0, 95% CI = 5.3-12.2, p < .001), and age of diagnosis was significantly younger in Sphynx cats (2.0 ± 1.5 years vs. 5.9 ± 4.0 years, p < .001). Corneal sequestrum recurrence was noted in 19.4% Sphynx eyes and 6.4% non-Sphynx eyes undergoing surgery (p = .015). Lower eyelid entropion-most often bilateral (80%)-was significantly more common in Sphynx versus non-Sphynx cats (odds ratio = 4.1, 95% CI = 2.3-7.1, p < .001), and age of diagnosis was significantly younger in Sphynx cats (0.9 ± 1.4 years vs. 3.5 ± 3.3 years, p < .005).

CONCLUSIONS

Corneal sequestrum and entropion were overrepresented and diagnosed at an earlier age in Sphynx cats when compared with the general feline population. Given the high prevalence, early age of onset, and relatively high recurrence of corneal sequestrum in Sphynx cats, further studies are warranted to better understand etiopathogenesis and preferred therapies.

Autologous lamellar keratoplasty for the treatment of feline corneal sequestrum: A retrospective study of 35 eyes (2012-2020)

OBJECTIVE

To evaluate the use of autologous lamellar keratoplasty for the treatment of feline corneal sequestrum (FCS).

PROCEDURE

The medical records of cats diagnosed with FCS that underwent autologous lamellar keratoplasty between 2012 and 2020 with a minimum of 2 months of follow-up were reviewed. After keratectomy of FCS, a button adjacent to the corneal limbus was harvested on the same eye and sutured to the recipient bed. A nictitating membrane flap was left in place until the first recheck except for one patient. Postoperative treatment with topical and systemic antibiotics and systemic nonsteroidal anti-inflammatory medications was prescribed. Follow-up examinations were carried out 2 weeks, 1 month and 2 months post-operatively and consisted of a complete ophthalmic examination.

RESULTS

A total of 35 cats (35 eyes) were included. The median follow-up time was 3.2 months (range, 2-59 months). Brachycephalic cats were overrepresented (85.7%). The mean graft size was 6.5 mm (range, 6-9 mm). Minor complications consisting of melting and partial integration of the graft occurred in 2/35 eyes (5.7%). Recurrence was observed in 1/35 eyes (2.9%) and was managed by a superficial keratectomy. A good visual outcome was achieved in all eyes, and a faint or mild corneal opacification occurred in 15/35 (42.9%).

CONCLUSIONS

Autologous lamellar keratoplasty is an effective treatment for FCS, providing good tectonic support to the affected cornea and resulting in good visual and cosmetic outcomes. These results should be verified in future prospective studies that include a larger number of cases and longer-term follow-up.

Feline bacterial keratitis: Clinical features, bacterial isolates, and in vitro antimicrobial susceptibility patterns

OBJECTIVE

To describe clinical characteristics, bacterial isolates, and in vitro antimicrobial susceptibility patterns for cats with bacterial keratitis.

ANIMALS STUDIED

Eighty one cats with bacterial keratitis.

PROCEDURES

Medical records of cats with a clinical diagnosis of bacterial keratitis, confirmed by corneal culture, were reviewed from June 2004 to July 2017. Animal signalment, bacterial isolates, aerobic bacteria in vitro antimicrobial susceptibility test results, and pertinent clinical features were recorded. Percentages of susceptible aerobic bacterial isolates were statistically compared among selected antimicrobials.

RESULTS

There were 102 aerobic bacterial isolates recovered from corneal samples of the 81 cats presented with bacterial keratitis. The most frequent bacteria isolated were Staphylococcus species, which constituted 55% (56/102) of total isolates. All aerobic bacterial isolates grouped together had the highest percentage of susceptibility to ofloxacin (100%), ciprofloxacin (94%), chloramphenicol (93%), doxycycline (92%), ticarcillin (90%), gentamicin (89%), moxifloxacin (89%), tobramycin (86%), neomycin (85%), amikacin (84%), and cefazolin (84%). The same isolates had the lowest percentage of susceptibility to polymyxin B (2%), bacitracin (15%), and clindamycin (31%). When analyzed separately, the isolated Staphylococcus species had the highest percentage of susceptibility to ofloxacin (100%), tobramycin (93%), and neomycin (85%) and the lowest percentage of susceptibility to polymyxin B (3%) and bacitracin (13%).

CONCLUSIONS

Members of the Staphylococcus genus were the most frequent bacteria isolated from cases of feline bacterial keratitis. On the basis of in vitro susceptibility testing and mechanism of action, ofloxacin, ciprofloxacin, ticarcillin, gentamicin, or moxifloxacin are recommended for initial antimicrobial therapy of suspected bacterial keratitis in cats.

Porphyrins are not present in feline ocular tissues or corneal sequestra

OBJECTIVE

To determine if feline lacrimal glands, glands of the third eyelid, corneas, and corneal sequestra contain porphyrins, which could be responsible for the brown/amber discoloration of corneal sequestra and tears in affected cats.

PROCEDURES

Samples of grossly normal cornea, lacrimal gland, gland of the third eyelid, and sequestra obtained via keratectomy were collected. Porphyrin concentrations of the homogenate were determined by spectrofluorometry with protoporphyrin IX and coproporphyrin III dihydrochloride used as standards. A hamster harderian gland was used as a positive control.

RESULTS

Normal tissues were harvested from one eye each of 14 nonclient owned, adult, mixed-breed, short-hair cats euthanized for reasons not associated with this study. Eighteen sequestra were acquired from cats undergoing unilateral lamellar keratectomies. Breeds of the affected cats included eight Himalayan, five domestic shorthair, and one each of four other breeds. Only the positive control and standards contained levels of porphyrins above background. All feline samples examined were histologically normal with no evidence of porphyrins.

CONCLUSIONS

Porphyrins are absent in normal feline lacrimal glands, corneas, and corneal sequestra. Porphyrins do not appear to be the cause of the brown/amber color of feline corneal sequestra.

Aetiology of corneal ulcers assume FHV-1 unless proven otherwise

OVERVIEW

Feline ulcerative keratitis is a common presenting complaint and is frequently a sequela of feline herpesvirus 1 (FHV-1) infection; so much so, in fact, that it is fair to assume an FHV-1 aetiology until proven otherwise. Other potential causes of ulceration are trauma or underlying eyelid abnormalities (entropion, ectropion, agenesis, dermoids, neoplasia), lash abnormalities (ectopic cilia, trichiasis), tear film abnormalities or neurological deficiencies (trigeminal nerve paralysis, facial nerve paralysis).

CLINICAL CHALLENGES

The management of corneal ulceration in cats is frequently challenging, and treatment needs to be tailored carefully to the individual cat, its temperament, and the disease process present.

EVIDENCE BASE

The scientific literature on feline ulcerative keratitis is extensive, particularly that related to FHV-1 infection. The aim of this article is to review the aetiology and diagnosis of corneal ulceration in cats with particular reference to the evidence base available.

PATIENT GROUP

All age groups and breeds can suffer with ulcerative keratitis. Breed predispositions are present for some forms of corneal ulceration, and these are discussed.

Ultrastructural findings in feline corneal sequestra

OBJECTIVES

(1) To describe the ultrastructural features of corneal sequestra in cats; and (2) to enhance our understanding regarding the pathogenesis of feline corneal sequestration.

METHODS

Nine corneal sequestra were harvested via keratectomy from globes of nine cats. The sequestra were routinely fixed then postfixed for high resolution light and transmission electron microscopy (HR-LM and TEM, respectively). The tissues were embedded in Epon/Araldite. Sections of 0.5-microm thickness were cut and stained with 1% toluidine blue in 1% sodium tetraborate solution for HR-LM. Ultrathin sections were collected on copper grids and stained with uranyl acetate and Sato's lead stain for TEM. Ultrathin sections were examined and the images were captured on an Advantage HR CCD camera using a Hitachi 7500 electron microscope operated at 80 kV. Two healthy corneas from two cats were harvested immediately following euthanasia. These corneal tissues (control samples) were processed in the same manner as the corneal sequestra for HR-LM and TEM. A portion of each sequestrum was also submitted for polymerase chain reaction (PCR) testing for infectious agents including feline herpesvirus-1 (FHV-1), Toxoplasma gondii, Chlamydophila felis and Mycoplasma spp.

RESULTS

Ultrastructure of healthy corneal tissues revealed basal corneal epithelial cells aligned adjacent to a thin acellular layer similar to Bowman's layer with underlying tightly packed, regularly arranged, collagen fibrils oriented in different planes. Keratocytes were elongated and had long and irregularly shaped nuclei, and cytoplasm contained rough endoplasmic reticulum and abundant membrane-bound vesicles. In contrast, corneal sequestra contained varying amounts of an amorphous, electron-dense substance, continuous with intact basal epithelial basement membranes peripherally, and overlying corneal ulceration and loosely packed collagen fibrils. Remnants of necrotic keratocytes were seen in spaces between disarranged collagen layers. In all samples, occasional keratocytes exhibited morphology indicative of apoptosis including clumping and margination of chromatin, and shrunken cytoplasm. Varying degrees of inflammation were noted on HR-LM and TEM of affected corneas including peri- and intralesional neutrophils, lymphocytes, plasma cells, and macrophages. Corneal sequestra were FHV-1-positive (n = 3), FHV-1- and T. gondii-positive (n = 1), T. gondii-positive (n = 3), or negative for DNA of these infectious agents (n = 2) using PCR. All corneal sequestra were negative for DNA of Chlamydophila felis and Mycoplasma spp. using PCR.

CONCLUSIONS

Apoptosis may play a role in the pathogenesis of feline corneal sequestration independent of the presence of DNA of these infectious organisms. Prospective clinical studies are warranted to further understand the significance of T. gondii in relation to feline corneal sequestration.

Congenital and hereditary ocular abnormalities in cats

Congenital and inherited ocular diseases are reported less frequently in the cat than the dog. The 2 species also differ in their array of disorders, with familiar canine abnormalities like cataracts overshadowed by unique feline diseases such as eyelid agenesis and corneal sequestration. Organized according to the primary ocular structure affected and commingling congenital and inherited disorders in each section, the review begins with multiple ocular anomalies and their impact on globe-orbit relationship. Adnexal disorders include eyelid agenesis, entropion, dermoid, and nictitans gland protrusion. Corneal abnormalities range from the routine sequestrum and PPM-related opacity to those rare infiltrates accompanying inborn errors of metabolism. Brief descriptions of uveal anomalies, primary glaucoma, cataracts, and lens luxations follow. Retinal dysplasia and progressive retinal atrophy complete the summary. Suspicions of heritability are often based on small numbers of animals in sporadic reports of ocular disease, but the Persian, Burmese, and Siamese are among the breeds repeatedly linked with one or more of these disorders.

Feline Corneal Disease

The cornea is naturally transparent. Anything that interferes with the cornea's stromal architecture, contributes to blood vessel migration, increases corneal pigmentation, or predisposes to corneal edema, disrupts the corneas transparency and indicates corneal disease. The color, location, and shape and pattern of a corneal lesion can help in determining the underlying cause for the disease. Corneal disease is typically divided into congenital or acquired disorders. Congenital disorders, such as corneal dermoids are rare in cats, whereas acquired corneal disease associated with nonulcerative or ulcerative keratitis is common. Primary ocular disease, such as tear film instability, adenexal disease (medial canthal entropion, lagophthalmus, eyelid agenesis), and herpes keratitis are associated with the majority of acquired corneal disease in cats. Proliferative/eosinophilic keratitis, acute bullous keratopathy, and Florida keratopathy are common feline nonulcerative disorders. Nonprogressive ulcerative disease in cats, such as chronic corneal epithelial defects and corneal sequestration are more common than progressive corneal ulcerations.

Feline corneal sequestra: a review of 64 cases (80 eyes) from 1993 to 2000

Feline corneal sequestrum is a common condition of the feline cornea. The purpose of this study was to provide a detailed description of the clinical features of the condition including the response to different management options and to assess the rate of recurrence. The medical records of 64 cases (80 eyes) of feline corneal sequestra that presented to the Animal Health Trust from 1993 to 2000 were reviewed. Fifty-two cases were reviewed retrospectively; 12 cases were assessed prospectively between April and September 2000 as part of a separate study. The Persian was the most frequently encountered breed and the mean age of affected cats was 5.6 years. At initial presentation, sequestra were unilateral in 58 cats and bilateral in 6 cats, 5 of which were Persians. Ocular discomfort and ocular discharge were common presenting signs, occurring in 42 and 36 eyes, respectively. Seventy-four eyes were managed surgically with keratectomy only (n = 44) or keratectomy followed by a graft procedure (n = 30). Sequestra recurred in 16 eyes in the study. There was no significant difference in the rate of recurrence between eyes that received a graft procedure (n = 5) and eyes that did not (n = 11) (P = 0.56). Complications following transection of conjunctival pedicle grafts were observed. Brown to black discoloration of noncorneal tissue and therapeutic biomaterials was observed, including discoloration of both viable and apparently nonviable grafted conjunctival tissue, small intestinal submucosa graft material and bandage contact lenses.