Ophthalmology

Compiled by Dr. Khyne U Mar, DVM and Willem Schaftenaar, DVM

Eye problems are not uncommon in elephants. They are often the result of trauma and presented as superficial or deep cornea lesions and ulcers. Cataracts are also regularly seen in elephants. If the vision in one eye is reduced, the animal should be approached with care from that side.

Clinical examination

 

The clinical examination of the eye starts with the anamnesis and observation of the animal.

The eyelashes should be long in order to protect dirt and objects from touching the eye ball. They are located mostly superior to the eye and can be as long as 11 cm. The inferior eyelid has less and smaller (2 cm) lashes.

A unique feature of the elephant eye is the lack of a lacrimal apparatus (lacrimal glands as well as nasolacrimal duct) and eye brows. Tear films simply flow towards the medial canthus and exit along a groove in the skin onto the face in Asian elephants (Wong et al. 2012).The area around the eyes is often wet.

A Schirmer tear test can be performed in elephants. In a research cohort of 80 healthy Asian elephants the mean value was 34.3+/- 1.7 mm/min with older elephants (>40 years) having higher values than younger ones (<20 years).

The cornea should be clear, without any irregularities

The iris of an elephant varies in color from tan, yellow, brown or the combinations.

Blepharospasm is a strong indication for ocular disease.

Conjunctiva cultures can be taken, though the strong palpebrae can make sampling for culture a challenge.

Ophthalmic anesthetics can be used safely in elephants and may facilitate clinical examination and allow ophthalmoscopic examination of the deeper ocular structures.

The pupillary light response can be performed if the elephant trusts the clinician enough to approach the animal with a proper light source at the required short distance. This test should be performed in subdued light.

The menace response can be performed if the animal allows the clinician at short distance by moving fingers towards the elephant's eye without causing air movement. 

The numerous hairs on the skin of the palpebrae are not true cilia or true eyelashes are as they are not associated with the margins of the palpebrae (Wong et al 2012, J. Zoo and Wildlife Med., 43(4), pp 793-801). The lower eyelid is more developed and ascends to a greater degree than the upper lid descends (Suedmeyer, 2006). (Photo KUMar)

The iris of an elephant can have several colors: tan, yellow, brown or a combination. (Photo: WSchaftenaar)

A white, circumferential ring, similar to the arcus senilis in man is noticed in 40+ yr Asian elephant (fat deposit or aging?). (Photo: KUMar)

Fluorescein staining of the cornea may be difficult as the elephant will close its eye immediately when approached. A fluorescein strip can be diluted in sterile water and sprayed over the eye ball in a constant flow using a blunt small gauge needle on a 10 ml syringe. This should be sprayed on the eye from the medial or lateral side. It helps when at the same time a steady water stream is directed at the periocular skin, which may result in relaxation of the animal.

After fluorescein has been sprayed on the cornea, the eye should be flushed with sterile saline to remove excessive fluorescine. If present, cornea defects will stain under blacklight.

Cataract (white central spot) and keratitis (diffuse, superficial cloudiness of cornea) is frequently seen in elephants. Vision can be checked by passing the light bundle of a flashlight (telephone) from the ear over the eye (blinking reflex). 

Ophthalmoscopy in the untrained elephant can be quite a challenge, as the animal will usually not allow this kind of close examination that moreover uses a light source. However, the animal can be trained to allow ophthalmoscopy.

The third eyelid or nictitating membrane is located at the ventro-medial aspect
of the orbit. Inside the nictitating membrane, an oblong, flanged-shaped piece of hyaline cartilage supports the anterior palpebral aspect of the nictitating
membrane. A harderian gland that is located here, plays a role in the lubrication of the cornea. Zeis's glands (modified sebaceous glands) are located in the margins of the lid. They produce an oily substance that helps lubricate the cornea.

 

The nictating membrane in an Asian elephant (arrow).(Photo: KUMar)

Blinking reflex using a smartphone's flash light in an Asian elephant with chronic keratitis. (Video: WSchaftenaar)

Ultrasonographic examination

The clinical examination of the elephant's eye can benefit from transcutaneous ultrosonographic examination. The anterior eye chamber, the lens end the posterior eye chamber can be visualized using a 4-7 MHz convex probe (Bapodra et al. 2010).

Eyelids

Blepharitis is an inflammation of the eyelids than can be caused by trauma (rubbing), parasite infection or as part of a localized dermatitis. The accompanying symptoms are blepharospasm, epiphora (wet skin area below the eye) and often photophobia. Sometimes lice (Haematomyzus elephantis) or ticks (Amblyomma tholloni) can be found on the eyelids causing local skin lesions.

Blepharitis in an Asian elephant. (Photo: KUMar)

Small skin lesion caused by ticks (Amblyomma tholloni) 

(Photo: KUMar)

Conjunctiva

The conjunctiva is a tissue that lines the inside of the eyelids and covers the sclera (the white part of the eye). It is composed of unkeratinized, stratified squamous epithelium with goblet cells, and stratified columnar epithelium. The conjunctiva is highly vascularised, with many microvessels.

 

Conjunctivitis is an inflammation of the conjunctiva and is a common finding in elephants. In several cases small nodules and vesicles were observed (lymphoid tissue on histology), possibly associated with chronic irritation. A conjunctivitis is often the result of trauma (hard object, dust, irritating liquid or smoke). Conjunctivitis is also seen in poxvirus infections.  

Conjunctivitis in a Asian elephant (From: Elephant care manual for mahouts and camp managers, FAO 2005

Conjuctivitis and keratitis in an Asian elephant. Note the swollen mucosa. (Photo: KUMar)

The conjunctival sac is connection between the palpebral and bulbar conjunctiva. Under certain conditions (hypoproteinemia, trauma, insect bites or allergic reactions), a prolapse of this part of the cornea can develop, which protrudes like a mucosal sac between the eye and the lower eyelid.  

Prolapse of the corneal sac in an Asian elephant. 

(Photo: KUMar)

Cornea

The cornea is transparent because it lacks cells and blood vessels and has no pigment. The cornea should always be wet thanks to a pre-corneal film tear. Oxygen and nutrients are available from the aqueous cornea tear film, the limbal capillary plexus and the palpebral conjunctival capillaries.

 

Several disorders of the elephant cornea have been reported. Most of the cornea lesions seem to have a traumatic cause: trauma by rubbing, allergy by environmental irritants such as exposure to direct sunlight or continued exposure to dryness or small particles, e.g. dust, smoke, grass seed etc. that damage the corneal epithelium.
Hypovitaminosis-A has also been suggested as a cause of cornea disorder as well as hypoproteinemia.

Corneal edema

Corneal edema, also called corneal swelling, is a buildup of fluid in the cornea. It is caused by dysfunction of the endothelium membrane on the inner side of the cornea, that normally pumps fluid out of the cornea in order to keep it transparent and clear. This can happen after a blow on the eye or a puncture of the cornea (e.g. by small branches), or by contact with toxic substances. 

Cornea edema in an Asian elephant. (Photo: KUMar)

Cornea edema in an Asian elephant. (Photo: KUMar)

Cornea opacities - keratitis

Opacities in the cornea are called keratitis and are very common in elephants. They present as whitish, "cloudy" areas usually in the central part of the cornea. It has been suggested that they are caused by trauma (thorn, heat, dust, and chemicals), direct sunlight or chronic dehydration. The cornea must be checked for foreign bodies. In case of a severe keratitis, the entire cornea turns white. This reduces the vision of the animal just the distinction between light and dark. This can be tested with the blinking reflex. In some cases, the keratitis can be painful: the elephant shows blepharospasm and the third eyelid may be protruded (partly) over the eyeball. In that case involvement of the iris should be considered.

It is recommended to perform cytology, aerobic bacterial culture, and sometimes fungal culture. 

 

When opacities are only found in the superficial epithelium, and dispersed over the entire cornea surface, it might be the result of hypovitaminosis-A (vitamin A is essential for the normal functioning of the corneal epithelium, including the production of the tear film). This condition is called "xerophthalmia".

As fluid makes its way into the cornea it can accumulate and cause the
formation of small bullae or "blisters." This is called bullous keratopathy. If the
blisters break or rupture, a corneal ulcer will result.

Mild, superficial opacity in the central area of the cornea an Asian elephant (keratitis). (Photo: KUMar)

Diffuse, superficial opacities spread over the entire cornea of an Asian elephant, possibly caused by hypovitaminosis-A (xerophthalmia). (Photo: KUMar)

Mild keratitis in an Asian elephant. (Photo: KUMar)

Severe keratitis involving the entire cornea of an Asian elephant. (Photo: KUMar)

Severe keratitis with protrusion of the third eyelid in an Asian elephant. This could be an expression of pain, in which case iris involvement should be considered. (Photo: KUMar)

Cornea ulcus

A cornea ulcer is an open sore on the cornea. The epithelial outer layer and the middle layer of the cornea are disrupted. This condition is very painful and blepharospasm is often seen. Sometimes the elephant is rubbing the area around the affected eye against an object. There may be protrusion of the third eyelid. 

An ulcer is usually the result of trauma. Treatment of a keratitis with NSAID's or glucocorticosteroids increases the risk of ulceration.

As a reaction on the ulcus and to repair the lesion, blood vessels will grow into the stroma of the cornea, visible as small red lines, sometimes forming a network of small vessels. This process takes several weeks. When the cornea surface has been repaired, the remnants of these blood vessels will be visible as white connective tissue strands. The major risk in an ulcus cornea is perforation of the entire cornea, which will result in loss of the ocular fluids and complete loss of the eye,

When blood vessels fail to grow towards the ulcer, the ulcer remains in an unchanged form as an indolent corneal ulcer, needing a special treatment.

Two manifestations of a severe keratitis and cornea ulcer with a prolapse of the iris in an Asian elephant. (Photo: KUMar)

Hypopyon

Hypopyon keratitis is an accumulation of pus (heterophyls and fibrin) in the anterior eye chamber (between cornea and lens). It is accompanied by profuse discharge and signs of ocular pain. Ultrasonographic examination may be helpful for diagnosing the pus in the anterior eye chamber. One case reports describes the treatment of hypopyon in an Asian bull elephant. Hypopyon and uveitis have been described in a case of leptospirosis (Fowler. 2006. Infectious diseases. In: Fowler and Mikota, 2006, 403).

 

Iris and uvea

The iris is a diaphragm that regulates the influx of light. It is a very vulnerable structure that consists of two layers: the front pigmented fibrovascular layer (known as a stroma) and, beneath the stroma, pigmented epithelial cells.The back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the dilator muscles. The high pigment content blocks light from passing through the iris to the retina, restricting it to the pupil. The outer edge of the iris, known as the root, is attached to the sclera and the anterior ciliary body. The iris and ciliary body together are known as the anterior uvea.

 

Any lesions in the anterior part of the eye can result in damage to the iris. Parts of the affected iris may come into contact with the inner layer of the cornea (anterior synechya) or the lens (posterior synechia). If there is also a corneal ulcer, the iris may prolapse through the ulcer (iris prolapse). Iris lesions are considered to be very painful in all animal species. These conditions need immediate veterinary attention. 

Lesions of the iris and uvea are called uveitis. If only the anterior part is involved, we call it iritis. In reality it will be hard to distinguish these conditions in elephant ophthalmology, unless proper ophthalmoscopy can be performed under sedation or general anesthesia.

Lens

The lens is a transparent biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. Any lesions of the lens will result in white discoloration and loss of transparency (cataract). This is seen as in the central pupillary space. Young cataracts will show as cloudy structures. A mature cataract appears as a completely white pupil. 

A complete, mature cataract will reduce the vision of the elephant which may finally result in complete blindness of the affected eye. When an elephant is approached on the side of the blind eye, the clinician should be aware of the compensating behavior of the elephant, when it tries to keep its functional eye on the investigator.

Several causes of cataracts are known in other animal species: overexposure to sun light, deficiency of vitamin A, C, E or riboflavin, diabetes and dehydration. Often the cause of a cataract in elephants cannot be retrieved. 

Early stage of a cataract in an Asian elephant. (Photo: KUMar)

Advanced stage of a cataract in an Asian elephant. (Photo: KUMar)

Advanced stage of a cataract in an Asian elephant. (Photo: KUMar)

Panopthalmitis and phthisis bulbi

Panophthalmitis is the inflammation of all coats of the animal eye including intraocular structures. It has been documented in nine eyes postmortem during a field study of eye lesions in African elephants (McCullagh, 1969)

Phthisis bulbi is a shrunken, non-functional eye. It may result from severe eye disease, inflammation or injury. 

Phthisis bulbi after chronically infected cornea ulcer. (Photo: KUMar)

Subdermal injection of Plancentrex (0.1 mg/ml) in an Asian elephant. (Photo: KUMar)

The elephant's eye can be flushed using a long, small diameter tube place on a syringe. (Photo: KUMar)

Treatment options in elephant ophthalmology

Blepharitis: Treatments of blepharitis in elephants have not been described in the literature. A similar approach as in other mammals is recommended: elimination of the cause (parasites, dermatitis) and flushing the eye with saline solution, 3-5 dd.

Conjunctivitis, prolapse of the corneal sac: elimination of the cause and flushing the eye with saline solution, 3-5 dd and antibiotic ointment, 3-5 dd.

Cornea edema: flushing with a hypertonic saline solution, 3-5 dd.

Keratitis in early stage: flushing with saline solution, 3-5 dd, antibiotic ointment, 3-5 dd

Chronic keratitis: treatment will have no effect.

Xerophthalmia: oral vitamine A supplementation.

Cornea ulcer: flushing with saline solution, 3-5 dd, analogues serum, antibiotic ointment, debridement, pain relief (systemic). A contact lens for horses has been used in a 44 yrs-old Asian elephant with a cornea lesion. Unfortunately the lens was lost within a few days.

Hypopyon: pain relief (NSAID), systemic antibiotics (DDX: leptospirosis!).

Uveitis and Synechia: Atropine sulfate eye ointment (1%), 4-6 dd, is a commonly used mydriatic drug in horses. It may stabilize the blood-aqueous barrier, reducing vascular protein leakage, minimizing pain from ciliary muscle spasm, and reducing the chance of synechia formation by causing pupillary dilatation. Pupil dilation is an indicator for the drug to be effective on the ciliary muscles. In horses even topical atropine has been shown to prolong intestinal transit time, reduce and abolish intestinal sounds, and diminish the normal myoelectric patterns in the small intestine and large colon of horses. Whether this also applies to elephants is unknown. Subdermal injection of placental extract (Placentrex®) is a common treatment for uveitis, hypopyon and corneal opacities in elephants in Asia (Suedmeyer, 2006).

Iris prolaps: systemic NSAID, flushing with saline solution, 3-5 dd. As the cornea is perforated by the prolapsed iris, the elephant should be treated systemically with antibiotics.

Cataract: only 2 cases of (mature) by phaecoemulsification have been reported (cataract surgery-UK and cataract surgery-USA) by phaecoemulsification have been reported. However, artificial lenses to replace the removed lens contents are not available.  

Panophthalmitis: Enucleation is the only treatment indicated for this condition. However, there are no published data on the treatment of panophthalmitis.

 
 

References and further reading:

  • Suedmeyer Wm. K. 2006. Special senses. In: Biology, Medicine and Surgery of Elephants, Ed. Fowler and Mikota, 399-403.

  • Fowler M. 2006. Infectious diseases. In: Biology, Medicine and Surgery of Elephants, Ed. Fowler and Mikota, 148.

  • Priya Bapodra, Tim Bouts, Paul Mahoney, Sally Turner, M.A., Ayona Silva-Fletcher, and Michael Waters. 2010. Ultrasonographic examination of the Asian elephant (Elephas maximus) eye. Journal of Zoo and Wildlife Medicine , Vol. 41, No. 3, 409–417.

  • Michael A. Wong, Ramiro Isaza, J. Kelly Cuthbert, Dennis E. Brooks and Don A. Samuelson. 

  • 2012. Periocular anterior adnexal anatomy and clinical adnexal examinaton of the adult Asian elephant (Elephas maximus). Journal of Zoo and Wildlife Medicine , Vol. 43, No. 4, pp. 793-80.

  • McCullagh, K.G. and Gresham, G.A. 1969. Eye lesions in the African elephant (Loxodonta africana). Res Vet Sci 10(6): 587–589.