Congenital ocular disease in the foal

Campylorrhinus lateralis, Bilateral microphthalmia and odontoma temporalis in an Oldenburg Foal

An Oldenburg colt with wry nose was autopsied after having lived for only 30 min. It presented cyanotic oral mucosae, underdeveloped eyes and a right-sided temporal osseous mass. The applicable nomenclature for the defects is discussed, and the potential etiopathogenesis is explored by describing the normal embryonic development of the affected body parts.

Canaliculosinostomy as a Long-Term Treatment of Seven Horses for Permanent Obstruction of the Nasolacrimal Duct

OBJECTIVE

To describe canaliculosinostomy performed to resolve epiphora caused by nasolacrimal duct obstruction and to report the outcome of horses undergoing this procedure.

STUDY DESIGN

Case series.

ANIMALS

Seven horses with uni- or bilateral nasolacrimal duct obstruction.

METHODS

The ventral lacrimal punctum and canaliculus were expanded with catheters of increasing diameter until a 14 gauge, Jamshedi needle could be passed into and through the lacrimal sac into the caudal maxillary sinus. One end of a plastic tube was inserted through the needle into the sinus, and the needle was withdrawn over the tubing. Using a hubless needle, the other end of the tube was passed through the lower eyelid leaving a segment of tubing exposed ventral to the eyelid. The end of the tubing within the sinus was exteriorized through a trephine hole in the frontal sinus and then tunneled beneath the skin adjacent to the osteotomy using a hubless needle, leaving a segment of tubing exposed on the forehead. Exposed tubing was sutured to the skin. The tubing was removed at 5-6 weeks.

RESULTS

Canaliculosinostomy was easily performed with the horses sedated. Five horses had resolution of epiphora, and 2 had improvement.

CONCLUSION

Canaliculosinostomy to divert lacrimal secretions into the sinuses resolves or improves epiphora caused by nasolacrimal duct obstruction and provides a good functional and cosmetic outcome. Canaliculosinostomy can be performed in the sedated horse.

Ophthalmic lesions in neonatal foals evaluated for nonophthalmic disease at referral hospitals

OBJECTIVE

To determine types and frequency of ophthalmic lesions detected in neonatal foals evaluated for nonophthalmic disease at 3 veterinary referral hospitals and to investigate associations between systemic and ophthalmic diseases in these foals.

DESIGN

Prospective cross-sectional study.

ANIMALS

70 foals < 30 days old.

PROCEDURES

Complete ophthalmic examinations were performed. Signalment, clinical signs, mentation during ophthalmic examination, results of clinicopathologic tests, and diagnosis of systemic disease were recorded. Descriptive data analysis including a χ(2) test for associations was performed.

RESULTS

Most foals (39/70 [55.7%]) with systemic disease had ≥ 1 ophthalmic lesion detected. Of the 39 foals with ophthalmic disease, 24 (61.5%) had potentially vision-threatening lesions. Clinically important abnormalities included conjunctival hyperemia or episcleral injection (30/70 [42.9%]), uveitis (18/70 [25.7%]), ulcerative keratitis (13/70 [18.6%]), nonulcerative keratitis (10/70 [14.3%]), entropion (8/70 [11.4%]), retinal hemorrhage (8/70 [11.4%]), and cataract (6/70 [8.6%]). Foals with sepsis were significantly more likely to have uveitis than were those without sepsis. Foals with sepsis and uveitis were also significantly less likely to survive to discharge than were foals that had sepsis without uveitis. Acquired ophthalmic disease (detected in 37/70 [52.9%] foals) was significantly more common than congenital ophthalmic disease (detected in 9/70 [12.9%]).

CONCLUSIONS AND CLINICAL RELEVANCE

Ophthalmic lesions were detected in 55.7% of neonatal foals with systemic disease. Acquired ophthalmic disease was more commonly detected than congenital ophthalmic disease. Foals with sepsis were more likely to have uveitis than were foals without sepsis. A complete ophthalmic examination is indicated in neonatal foals evaluated for systemic disease.

Ocular conditions of neonatal foals

A discussion of ocular conditions of foals with an emphasis on congenital and inherited disorders is presented. An understanding of the normal postnatal development of the eye and adnexae is important. Recognition of inherited abnormalities is essential when giving advice on breeding suitability, and prompt attention or referral of deteriorating ocular conditions in foals ensures the best outcome for future use. Congenital conditions may be recognized for the first time in older animals during their first thorough eye examination.

The lens and cataracts

It is conservatively estimated that some form of lens opacity is present in 5% to 7% of horses with otherwise clinically normal eyes.These opacities can range from small epicapsular remnants of the fetal vasculature to dense and extensive cataract. A cataract is defined technically as any opacity or alteration in the optical homogeneity of the lens involving one or more of the following: anterior epithelium, capsule, cortex, or nucleus. In the horse, cataracts rarely involve the entire lens structure (ie, complete cataracts) and are more usually localized to one anatomic landmark or sector of the lens. Complete cataracts are invariably associated with overt and significant visual disability. Focal or incomplete cataracts alone seldom cause any apparent visual dysfunction in affected horses,however.

Congenital ocular abnormalities of Rocky Mountain Horses

OBJECTIVE: To determine the incidence and describe ocular abnormalities in a cross-section of the population of Rocky Mountain Horses. Design: Prospective study. Animals: Five-hundred and fourteen Rocky Mountain Horses. Procedure: Ophthalmic examinations were performed using a slit-lamp biomicroscope and an indirect ophthalmoscope. Intraocular pressures were measured by applanation tonometry. Eyes from six horses were obtained for histologic examination. RESULTS: Cysts of the posterior iris, ciliary body, and peripheral retina were detected most frequently (249 horses), and were always located temporally. Curvilinear streaks of retinal pigmented epithelium extending from the peripheral temporal retina marked the boundary of previous retinal detachment in 189 horses. Retinal dysplasia was detected in 125 horses. Multiple ocular anomalies were evident in 71 horses and were always bilateral and symmetrical. Affected eyes had a large, clear cornea that protruded excessively and had an apparent short radius of curvature, a deep anterior chamber, miotic and dyscoric pupil, and iris hypoplasia. Pupillary light responses were decreased or absent and pupils failed to dilate after repeated instillation of mydriatic drugs in horses with multiple ocular anomalies. Less frequently encountered abnormalities included peripheral iridocorneal adhesions and goniosynechiae. Congenital cataract was always present in eyes with multiple abnormalities. Intraocular pressures did not differ among horses with normal eyes and horses with multiple ocular abnormalities. Histologic examination of eyes corroborated the clinical appearance.

Study of the hyaloid apparatus in the neonatal thoroughbred foal

Over 80 per cent of 169 neonatal thoroughbred foals had some part of the hyaloid artery present bilaterally and its degree of completeness, colour and character was statistically symmetrical. The complete artery was present in over 60 per cent of the foals. The incidence of the hyaloid artery and its completeness, colour and character were related to the age of the foal. The hyaloid system atrophies in the early stages of the neonatal period and generally its presence did not cause any significant ocular problems. The presence and morphology of the posterior pupillary membrane was highly correlated with the presence, completeness, colour and character of the hyaloid artery.

Survey of retinal haemorrhages in neonatal thoroughbred foals

Twenty-seven of 167 neonatal thoroughbred foals (16 per cent) were found to have retinal haemorrhages after a careful examination of the entire fundus. Experience in differentiating haemorrhages from other lesions, and the selection of foals from normal populations, were considered to have an important effect on their apparent incidence. Bilateral haemorrhages were more common and there was a significantly higher incidence in female foals. The numbers of haemorrhages ranged between one and 20; 36 per cent of eyes with retinal haemorrhages had the small punctate type and 56 per cent had the splash-like form. There was no change from one type of haemorrhage to another, and the patterns of resolution were similar. The haemorrhages were in the tapetal fundus, except two that were recorded in the optic disc, and they resolved within 10 days. No short- or long-term ocular or neurological effects of the retinal haemorrhages were detected, and they were not related to the incidence of abnormal foal behaviour.

Subconjunctival haemorrhages in neonatal thoroughbred foals

A survey of 169 neonatal thoroughbred foals revealed that 8.3 per cent had subconjunctival haemorrhages, but there was no indication of a relationship between retinal and subconjunctival haemorrhages. The haemorrhages were not related to any abnormality of the foals and there was no sex or eye predisposition. In most cases the haemorrhages were fresh and red, occurred mainly dorsally or dorsonasally and extended up to the limbus; they resolved completely within four to 10 days, depending on their initial severity and extent. They had no effect on the foals' vision in the short or long term. The incidence of subconjunctival haemorrhages was associated with foaling category, multiparity and country of birth.

Miscellaneous conditions of the equine head

Nutritional secondary hyperparathyroidism is associated with horses that are fed diets with an imbalance of calcium and phosphorus or diets containing oxalates. Clinical signs include a shifting lameness, with tenderness of the joints, reluctance to move, or a stiff, stilted gait. Some horses may have broadening of the nasal bones, enlargement of the maxilla and/or the mandible, or a ridge over the nasal bones. Diagnosis may include physical examination findings; analysis of feed; and clinical pathologic data, which may include normocalcemia, normal to increased serum phosphorus, and increased fractional excretion of phosphorus (normal FxP < 0.5%). The primary objective of therapy is to correct the nutritional calcium to phosphorus imbalance. Sialoliths are calcific concretions that develop in the salivary gland or duct. Therapy generally involves surgical removal, and associated complications are uncommon. Obstruction of the nasolacrimal duct occurs most commonly secondary to intraluminal foreign material, although congenital atresia may occur. Clinical signs include epiphora, conjunctivitis, and mucopurulent discharge. Foreign material is often removed by retrograde saline flush and atresia is resolved by surgery.

Eyelid and nasolacrimal disease

An understanding of normal structure and function of the equine eyelid is essential to make an accurate diagnosis and appropriately treat equine eyelid diseases. Entropion, eyelid trauma, neoplasia, and nasolacrimal disorders are reviewed. Methods of diagnosis and treatment are presented.

Diagnosis and treatment of lens diseases

The lens represents a unique tissue in light of its embryologic development, retention of old cells and nuclear make-up, transparent nature, immune privileged status, and metabolic restrictions. Disorders of malformation and malposition occur, but cataract development is the most common and significant problem for owners and animals. Technologic and pharmacologic advances have allowed surgical removal of equine cataracts to become an acceptable alternative, capable of returning a visually impaired horse to a functional status. Uveal inflammation represents the greatest threat to successful surgical cataract removal. Veterinarians should consult with those versed in ophthalmology for assistance in diagnosis, prognosis, peroperative treatment, surgical intervention, and follow-up on lens disorders.

Congenital ocular anomalies

This discussion provides an idea of the diversity and relative prevalence of certain congenital ocular conditions of horses. Many are not difficult to diagnose, yet curative treatment may be impossible. When dealing with owners of horses affected with unusual anomalies, responsible client service requires veterinarians to provide accurate information and to know where answers to unusual questions can be found. Again, most veterinarians never encounter all of the diverse congenital defects. As a result, the horse owner frequently receives misinformation. Hopefully, this brief coverage of congenital ocular anomalies will provide useful information and assist in appropriate communication to concerned parties.