Enucleation of an eye in a goldfish

26 Enucleation of an eye in a goldfish

INITIAL PRESENTATION

Unilateral ocular swelling in a goldfish.

Introduction

Goldfish are attractive fish, relatively hardy and long-lived (>20 years in optimum conditions). They are commonly kept as family pets and also as display fish in public ponds. External lesions are easily identified by owners, including ocular pathologies.

CASE PRESENTING SIGNS

An adult goldfish (Carassius auratus) presented with unilateral ocular swelling of gradual onset.

Husbandry

The goldfish was housed in an indoor display pond, approximately 25 cm deep and 4.5 × 6.0 m in size. Water was changed continuously (from mains water), constituting a third of the water being changed every 6 weeks. Filtration was achieved using rapid sand and ultraviolet filters. The water was not routinely monitored for the presence of toxins such as nitrates and nitrites. Commercial goldfish food was offered once daily on 5 days each week. A relatively low stocking density was present, with several other goldfish in the pond. The other fish in the pond did not show any clinical signs of disease.

Case History

The goldfish’s right eye had been noted to gradually increase in size over a period of 2 months. Otherwise the fish appeared unaffected by the ocular problem, but as it was in a display pond the facility’s management were concerned about public perception and presented the animal to the veterinary clinic for assessment. The history presented was:

• No loss of appetite

• Activity normal

• Gradual development of right ocular swelling.

Clinical Examination

The patient was initially assessed in the presenting container:

• Swimming movements were normal (albeit in a small enclosure)

• There were no obvious lesions on the integument

• Respiration rate and depth were evidenced by opercular movement, and noted to be normal

• The right eye was distended, extending 2 cm out from the skull (Fig. 26.1).

Figure 26.1 Dorsal view of goldfish’s head, showing distended right eye.

It was decided to perform further investigations, and a ‘hands on’ examination was reserved for when the fish was anaesthetized.

CLINICAL TIPS

Clinical examination of fish

• Observation of the fish in water provides useful information, including assessment of the animal’s mobility and respiratory movements.

• In some cases it is necessary to perform a brief conscious examination with the fish out of the water:

• The fish can be gently grasped in the hands, or a net used to capture it.

• Some of the examination may be performed with the fish in water, or it may be raised into the air for a brief period.

• It is advisable to hold the fish above the water container in case a sudden movement by the animal releases it.

• A net should be used for larger fish before handling, or they should be anaesthetized.

• Handling is stressful for fish, and may result in physical damage. Although this may appear minor, for example with the loss of a few scales, this may provide an entry portal for infection that may progress to septicaemia and death. Great care should therefore be taken when handling specimens. Nets should be free of holes that may catch a fin, and of abrasive surfaces.

DIFFERENTIAL DIAGNOSES

If possible, the practitioner should differentiate between buphthalmos (abnormal enlargement of the eye) and exophthalmos (‘pop eye’, abnormal protrusion of the eye, e.g. as a mass pushes it). Systemic disease usually results in bilateral exophthalmos, and other clinical signs or behaviour changes are often present concurrently.

The differentials for ocular swelling are:

• Infection: localized infection is often the cause of unilateral pathology

• Trauma: may cause ocular rupture

• Corneal damage: resulting in corneal oedema, may rapidly (within 24 hours) progress to cataract formation

• Retrobulbar oedema, e.g. due to gas in or behind the eye

• Retrobulbar mass, e.g. abscess, neoplasia

• Ocular neoplasia

• Gas supersaturation (‘gas bubble disease’)

• Ammonia toxicity

• Septicaemia

• Malnutrition, e.g. hypovitaminosis A (pitting of the cornea may lead to exophthalmos, uveitis and retinal degeneration).

Case Work-Up

The goldfish was anaesthetized using tricaine methane-sulfonate (MS-222). Once induced, the fish was positioned in lateral recumbency on a wet incontinence pad. Water was dripped over the fish’s body to keep the integument moist. Anaesthesia was maintained by slowly syringing a 100 mg/ml solution of buffered MS-222 into the oral cavity using a catheter-tip syringe (Fig. 26.2).

Figure 26.2 Anaesthetized goldfish. MS-222 is being administered into the oral cavity using a syringe to maintain anaesthesia.

A full clinical examination was performed:

• Body weight was 250 g

• Right eye was enlarged. The cornea was opaque so intra-ophthalmic examination was not possible. No discharge was present

• The left eye did not have any apparent problems

• No other lesions were observed or palpated on the goldfish.

Tags: Saunders Solutions in Veterinary Practice Small Animal Exotic

Sep 3, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

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