Feline ocular emergencies

Feline ocular emergencies include any ophthalmic condition that has rapidly developed or is the result of trauma to the eye or periocular structures. Common feline emergencies include proptosis, lid lacerations, corneal ulcers, and foreign bodies. Complete ophthalmic examination including procurement of the minimal ophthalmic database (Schirmer tear test, fluorescein stain, and intraocular pressure measurement) should be obtained whenever possible to ensure that the complete and correct diagnosis is made. Concern for the patient's vision and ocular comfort should guide the practioner's diagnostic and therapeutic plan. This article reviews some of the more common feline ocular emergencies, including conditions affecting the orbit and globe, adnexa, conjunctiva, and cornea. Feline uveitis, glaucoma, and lenticular diseases are covered more thoroughly elsewhere in this issue.     

Ocular oncology

Neoplasia can affect all ocular tissues. The clinical appearance of ocular neoplasia can vary considerably depending on the specific tissue involved. Intraocular neoplasia may mimic or incite ocular inflammatory disease in addition to causing hyphema or secondary glaucoma. Intraocular neoplasms can be primary tumors or may be secondary to metastatic disease or systemic neoplasia. Primary neoplasms, metastatic tumors, tumors extending from adjacent structures, and systemic neoplasms can also affect the adnexal tissues. Many ophthalmic tumors are histologically benign but are locally invasive and, within the confined space of the eye or orbit, can produce significant tissue distortion. Certain ocular neoplasms, such as many canine eyelid tumors, are amenable to simple excision and can be adequately managed in general practice. The evaluation and treatment of other ophthalmic neoplasms, however, may require the additional equipment available only in larger specialty practices, such as computed tomography and radiation therapy. Early diagnosis of ocular neoplasia is an important aspect of successful management.     

Geriatric ophthalmology

The threat of vision loss increases with age owing to a combination of the accumulation of untreated or partially managed eye disease (for example, immune-mediated keratoconjunctivitis) as well as the late-in-life onset of certain ocular disorders such as lens subluxation/luxation syndrome and senile/age-related cataracts. In addition, the ophthalmic effects of age-related systemic diseases such as systemic hypertension can be vision threatening as well. The veterinarian must always weigh the potential ophthalmic benefits of contemporary therapy against the potential patient risk, not only when ophthalmic surgery is considered but also with the use of various drugs.     

Corneal diseases of rabbits.

Corneal diseases are common in domestic rabbits. It is important to carefully evaluate the cornea and the entire eye when rabbit present with clinical signs such as squinting, tearing, or conjunctival hyperemia. Complete ophthalmic examination and general physical examination should be performed on all rabbits with corneal disease. Important diagnostic testing include culture and sensitivity, cytology, and fluorescein staining. Breed predispositions do not occur for most corneal problems, although some diseases are selected genetically in research rabbits. Corneal disease can be a primary condition or can occur secondary to other ocular or systemic disease.     

Ophthalmic emergencies

Ocular emergencies can be very intimidating for veterinarians. Most ocular emergencies can be stabilized by the veterinarian until an ophthalmologist can be consulted if necessary. Proptosis, or forward displacement of the globe, can occur secondary to any blunt trauma to the head. The two options for a proptosed eye are enucleation or replacement with tarsorrhaphy depending on the viability of the extraocular tissues and eye. Glaucoma, or increased intraocular pressure (above 35 mm Hg), is diagnosed by measuring the intraocular pressure using a Shiotz or electronic tonometer. Emergency treatment includes intravenous mannitol and topical pilocarpine. Uveitis, or inflammation of the iris, ciliary body and/or choroid, can have many underlying causes such as neoplasia, infection, lens induced, and trauma. The treatment consists of treating the underlying cause, and administering topical atropine to alleviate pain and topical corticosteroids to decrease inflammation. Corneal ulcers, or defects in the corneal epithelium, are classified according to the depth of the defect. The treatment consists of topical antibiotics and topical atropine. If the ulcer is deep, is melting, or is a descemetocele, then a third eyelid or conjunctival flap is usually necessary. The cornea should be sutured if it is perforated or lacerated. Hyphema, or blood in the anterior chamber, can occur secondary to trauma, neoplasia, infection, or a coagulapathy. The treatment consists of treating the underlying cause and topical corticosteroids with or without antibiotics.     

Functional anatomy of the ocular circulatory system: vascular corrosion casts of the cetacean eye

OBJECTIVE: To examine the functional anatomy of the ocular circulation in four bottlenose dolphins (Tursiops truncatus) and five melon-headed whales (Peponocephala electra). PROCEDURE: Eyes were obtained postmortem from whales that died while in captivity and/or were found beached. Specimens from whales were investigated using scanning electron microscopy (SEM) of vascular corrosion casts and histology. The thermal characteristics of live dolphin eyes were measured using an infrared imaging system. RESULTS: The whale eye receives its primary blood supply from the ophthalmic rete, which extends just behind the eyeball. The ophthalmic rete diverges from the basilar rete and the cervical rete via the posterior thoracic artery. The iris and ciliary processes are supplied by iridic arteries via the major arterial circle that is located around the iris edge. The retinal vessels show the holangiotic type. Choroidal arteries run in parallel arrays so as to interdigitate the densely packed choroidal veins. The venules in the conjunctival fold and palpebral conjunctiva form a well-developed venous plexus. Thermographic examination revealed that the eye shows a substantially higher degree of thermal emission than adjacent skin areas. CONCLUSIONS: The cetacean eye is characterized by a unique vascular pattern and multivessel plexuses, which are quite different from those of terrestrial mammals. This suggests that the ocular vasculature might function as a thermoregulatory system so that the appropriate operating temperature for the photoreceptors can be maintained in a deep and cold aquatic environment. The distinctive plexuses in the orbit might also be for pooling blood in the eye to conserve oxygen during dives. The ophthalmic rete might play a role in a pressure-damping effect on cetacean ocular circulation as well.     

兽医眼表移植学及植片材料的研究进展

角膜疾病是动物最常见的眼科疾病之一,治疗不当将引起视力减退、致盲甚至眼球摘除,给动物带来巨大的痛苦与生活障碍。兽医眼表移植手术经历了多年的研究探索与改良,成为治疗动物角膜损伤、挽救眼球甚至恢复视力的有效方法。不同的手术方式与移植材料对于角膜愈合、免疫排斥、光学性以及眼球形态产生深远的意义和影响。现就各种眼表移植技术以及植片材料在动物角膜疾病中的适应症、应用特点以及预后等方面的研究进展进行综述,旨在为兽医眼科相关疾病的临床治疗层面提供有意义的指导。     

Equine ocular anatomy and ophthalmic examination.

This article is intended to provide the practitioner with a succinct but complete source regarding equine orbital and ocular anatomy,instrumentation available for ophthalmic examination, a methodical examination technique, sedation and regional nerve blocks, and diagnostic procedures involving the eye. Such knowledge of orbital and ocular anatomy is essential to allow recognition of normal,normal variations, or an abnormality of the equine eye and orbit.     

Development of the New Zealand White Rabbit Eye: I. Pre‐ and Postnatal Development of Eye Tunics

The New Zealand white (NZW) rabbit has been and is right now regularly utilized in ophthalmic surgery evaluation. Inside NZW rabbit eye, the visibility of ocular structures throughout surgical procedure is fantastic. Younger rabbits are used in different ages for the evaluation of ophthalmic surgery. Complete studies of ocular development in the NZW rabbits have not been reported previously. The aim of the present investigation was to describe the major landmarks and the time course of the pre‐ and post‐natal development of the complete eye tunics of the NZW rabbit to give a superb model as well as a fruitful area for further ophthalmological investigations. Serial histological sections of NZW rabbit prenatal (E13–E28) and post‐natal (P1–P14) stages were examined, respectively. The eye of the NZW rabbit developed in a similar manner to that of the human and domestic animals eyes; the principal differences were at the time of occurrence of certain developmental events, absence of pigmentation which represent an exploited benefit for ophthalmic surgery, remarkable Bowman's membrane at E25, poor developed ciliary stroma and juvenile retinal layer until P9. In human, the basic morphogenetic processes of the development of eye tunics are completed towards the end of the first half of gestation period. However, the latter represents the beginning stage of the development of eye tunics in the rabbit. Thus, allowing various extensive ophthalmic researches to be performed.     

Control of ocular inflammation

Although both topical and systemic anti-inflammatory agents have a place in veterinary ophthalmology, they play only a small role in overall patient management. They must be used appropriately to prevent ocular damage and loss of vision from inflammation and are not a replacement for a complete ophthalmic examination and specific treatment directed at the etiology of the problem. If used indiscriminately, they can result in local or systemic side effects or toxicities, many of which are worse than the initial problem for which they were selected. Just as topical corticosteroids are contraindicated with infectious keratitis, so are systemic corticosteroids contraindicated in patients with ocular inflammation resulting from a systemic infectious process. Anti-inflammatories must be used at the appropriate dosage and frequency. Use of corticosteroids that have low intraocular penetration for intraocular disease or corticosteroids with low potency is a waste of time and money. The most expensive medication is one that does not work. Avoid combination therapies when only a single medication is required. These do not save time or money and have the potential to result in the development of drug-related diseases. Diseases for which anti-inflammatory therapy has little or no indication include corneal scars, corneal edema, corneal pigmentation, corneal dystrophy, cataracts without inflammation, glaucoma, and retinal atrophy and degeneration. Last, remember that all commercially available ophthalmic medications are specifically formulated for use in the eye. Their pH, concentration, osmolality, and melting temperature all are designed to facilitate penetration. The use of dermal and otic preparations to treat ophthalmic problems is contraindicated.     

Ophthalmic Disorders Observed in Pet Chinchillas (Chinchilla lanigera)

This article presents a retrospective analysis of ocular disorders observed in outpatient pet chinchillas examined in a veterinary clinic between 2000 and 2010. The most common ophthalmic conditions diagnosed during this time period was alteration of the lens (15 eyes, 10 chinchillas), followed by abnormalities of the cornea (14 eyes, 13 chinchillas), and conjunctival disease (10 eyes, 9 chinchillas). The predominant lens disorder was cataracts, whereas the main alteration of the cornea was fluorescein-positive corneal substance loss. Subtle ocular changes appear to be common in the chinchilla. The data gathered within this study indicate that a thorough ophthalmic evaluation is warranted during routine physical examinations for this species.     

Effect of topical ophthalmic latanoprost on intraocular pressure in normal horses

The ocular effects of latanoprost ophthalmic solution were evaluated in two studies, with eight horses in each study. One eye of each horse was treated with latanoprost ophthalmic solution once daily for 5 days, and the opposite eye received a control solution of sterile eyewash. Intraocular pressure and pupillary diameter were measured daily for 5 days after treatment. Latanoprost had no significant effect on intraocular pressure or pupillary diameter in normal horse eyes compared with control eyes in these studies. Placement of an eyelid nerve block resulted in significantly lower intraocular pressure.     

Equine infectious keratitis.

Corneal ulcers are one of the most common ocular disease presentations in the horse. With the use of correct diagnostic techniques and selection of an appropriate treatment regimen, most cases result in a satisfactory outcome. The eye does not respond well to inflammation, and in complicated ulcers, this should be managed aggressively using systemic NSAIDs with a high priority assigned to removing the infectious agent. Care needs to be taken to avoid topical or systemic corticosteroid use for the treatment of equine ocular disease, however, unless the clinician is completely sure that the corneal disease is not caused by an infectious process. The use of combination corticosteroid-antibiotic ophthalmic preparations without an appropriate treatment rationale can result in doing more harm than good. It is important to have a treatment plan and to monitor the elected treatment regimen. The clinician should decide on some objective criteria at initiation of treatment so that any changes are made rationally. This approach should also include consideration of early referral of the eye's care to a veterinary ophthalmologist.     

Tissue distribution of dexamethasone in feline ocular structures following single topical application of dexamethasone as an ointment or suspension

Objective To compare the dexamethasone concentration in various structures of the feline eye following a single topical application of dexamethasone as an ophthalmic ointment or suspension. Animals studied Nineteen cats, euthanized due to reasons not related to this study, were selected and their ocular health status evaluated. Selected animals were treated with dexamethasone ointment or suspension. Procedure The concentration of dexamethasone was determined in the following structures of the eye: third eyelid, cornea, aqueous humor, iris, lens, vitreous body, and choroid/retina. The dexamethasone concentration in the eye was measured by radioimmunoassay. The applied amount of dexamethasone was 0.05 mg in 0.05 mL Isopto Dex^® ophthalmic suspension and 0.05 mL Isopto Dex^® ophthalmic ointment, respectively. Cats were treated once with ointment or suspension and were euthanized 3 h or 6 h after treatment. Results At 3 h after topical administration the highest concentrations of dexamethasone were measured in the anterior structures of the eye. The concentrations after application of ointment and suspension were comparable. However, 6 h after administration, the concentrations decreased after administration of suspension and increased further after administration of the ointment, leading to significantly higher concentrations of dexamethasone in the third eyelid, cornea and choroid/retina after treatment with ointment. Conclusion Therapeutically relevant concentrations of dexamethasone after a single topical administration were only achieved in the anterior structures of the eye. Six hours after application there was a substantially higher amount of dexamethasone in the anterior structures of cat eyes treated with ophthalmic ointment compared to ophthalmic suspension.     

Feline leukemia virus and feline immunodeficiency virus.

Ophthalmic manifestations of FeLV or FIV infection can occur in all ocular tissues and may be manifestations of direct viral effects or secondary to viral-related malignant transformation. Additionally, the manifestations of common feline ophthalmic pathogens may be more severe and poorly responsive to therapy because of the immunosuppressive effects of FeLV or FIV infection. Prompt diagnosis of underlying viral infection in cats with ophthalmic disease is paramount for accurate diagnosis and prognosis and is required for appropriate therapeutic decision making.     

Equine ophthalmic examination: Routine diagnostic techniques

A complete, thorough ophthalmic examination is essential in the clinical approach to equine ocular diseases. In the majority of cases and more than in most systems, an ophthalmic diagnosis can be achieved at the time of examination because most ocular structures can be visualised either directly or indirectly. This article describes examination protocol and the techniques, instruments and diagnostic procedures currently available to equine general practitioners.     

Corneal stromal sequestration and keratoconjunctivitis sicca in a horse

A 19-year-old Shetland pony presented with unilateral ocular discomfort and abnormal ocular appearance. Keratoconjunctivitis sicca, ulcerative keratitis and brown discoloration of the corneal stroma were identified on ophthalmic examination. The etiology of keratoconjunctivitis sicca was not determined in this case. For practical and financial reasons, the owners requested enucleation of the affected eye. Histopathologic examination revealed extensive loss of corneal epithelium overlying a zone of hypereosinophilic, degenerate, and necrotic corneal stroma. This well-circumscribed region of corneal stromal sequestration was surrounded by stromal vascularization, and an intense inflammatory, predominantly polymorphonuclear, cellular infiltrate. The clinical and histopathologic features of this case were considered remarkably similar to those observed in feline corneal stromal sequestration.     

Survey of ophthalmic disorders among captive pinnipeds in Japan

Pinnipeds have evolved enlarged ocular bulbs to catch fish in the dark. However, their large protruding eyes are easily damaged, which increases the risk of blindness and death in these animals. In captivity, ophthalmic disorders, manifested as keratitis and cataracts, are common among pinnipeds. In this study, we investigated symptoms of ophthalmic disorders in pinniped species using a questionnaire distributed to 32 zoos and aquariums throughout Japan. We conducted this study in cooperation with the Japanese Association of Zoos and Aquariums. The survey included 295 pinnipeds from four otariid species, five phocid species, and one odobenid species. Of these, 43.1% of the pinnipeds had diseases affecting the lens, cornea, and/or other eye parts. Age was positively associated with lens disorders in California sea lions, South American sea lions, and spotted seals. Conflicts and public appearances were also associated with corneal and/or lens disorders in California sea lions. Treatments were evaluated as effective for corneal disorders and conjunctivitis. The results of this study indicate that ophthalmic disorders in pinnipeds are related to the conditions of their captive environment. Aquariums and zoos should be encouraged to share information regarding optimal maintenance practices to improve the living conditions of pinnipeds.     

Vasculature of the ophthalmic rete in night herons (Nycticorax nycticorax): scanning electron microscopy of corrosion casts

Vasculature of the ophthalmic rete (rete ophthalmicum) in the night heron (Nycticorax nycticorax) was studied using scanning electron microscopy of vascular corrosion casts and light microscopy on tissue sections. Most blood to the eyeball and a lesser volume of blood to the brain passed through the ophthalmic rete via the external ophthalmic artery. The collateral retial arterioles originated from the external ophthalmic artery forming a flat and fusiform-shaped arterial network at the ventrotemporal region of the eyeball. The arterial network was intermixed with a similar complex of the veins from the eye. The ophthalmotemporal artery, which supplied the eyeball posteriorly, and supraorbital and infraorbital arteries, which supplied the eyeball anteriorly, originated from the rete. Blood from the eye, which is a site of potential heat loss, drained into the ophthalmic rete via the ophthalmotemporal vein. On the casts of retial arterioles, slit-like cleavages at branching sites representing flap valves, which might play a role as sluice valves, were seen. In addition, marks of circularly running grooves, which might represent tufts of smooth muscle cells and might contribute to a sphincter activity, were observed. These anatomical specializations of the avian ophthalmic rete, involving parallel arrangement of arteries and veins, may function to facilitate counter-current heat exchange and to regulate blood pressure and volume to the eye and the brain.     

Reference values for selected ophthalmic diagnostic tests of the ferret (Mustela putorius furo)

PURPOSE: To perform selected ophthalmic diagnostic tests in healthy ferrets with the aim of establishing normal physiological reference values for this species. METHOD: A total of 15 healthy, unrelated ferrets were used to test most of the parameters in this investigation. Eight of the 15 ferrets were used for central corneal thickness evaluation. Ages varied from 1.5 to 6 years of age. Selected diagnostic ocular tests were performed including Schirmer tear test, tonometry using an applanation tonometer (Tonopen), central corneal thickness using an ultrasonic pachymeter (Sonomed, Micropach, Model 200P +) and culture of the normal conjunctival bacterial flora. RESULTS AND DISCUSSION: Staphylococcus sp. and Corynebacterium sp. were isolated from healthy conjunctival and eyelid margins, suggesting they are normal constituents of the conjunctival flora of the ferret. Results for selected ocular diagnostic tests investigated here for the ferret eye were as follows: intraocular pressure: 14.50 +/- 3.27 mmHg; Schirmer tear test: 5.31 +/- 1.32 mm/min; central corneal thickness: 0.337 +/- 0.020 mm. No statistically significant differences between ages or genders were found for any of the results. The reference data for the ocular tests obtained in this investigation will help veterinary ophthalmologists to more accurately diagnose ocular diseases in the ferret. Knowledge of these reference values will be particularly useful to diagnose discrete or unusual pathological changes of the ferret eye.