6-Sclera

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SCLERAL AFFECTIONS

I-CONGENITAL ANOMALIES: -

1-Melanosis of the sclera in dogs: -

Melanin deposits sometimes be seen in animals less than one year of age at the sclera and cornea. It appears in a form of diffuse superficial plaques or in a form of firm nodules.

2-Coloboma of the sclera: -

Congenital absence of a segment of the sclera. It is seen in Collies and related breeds. The typical coloborna are seen affecting the optic nerve but it may occur in the sclera near the optic nerve or extend forward to the equator.

3-Scleral ectasia(thin sclera): -

This condition known as Collie ectasia syndrome or Collie eye anomaly. Scleral ectasia or lack of scleral development is observed in Albino or subalbinotic animals, Collie eye syndrome, Shelty eye syndrome, Australian Shepherds, Siamese cats and appaloosas horses. The control of the condition is accomplished by removal of all affected dogs from the breeding programs.

Symptoms:

1-Chorioretinal dysplasia                                  2-Colobomas at the posterior pole of the globe

3-Tortousity of the retinal blood vessels          4-Retinal detachments

5-Intraocular hemorrhage                                 6-Central corneal opacity

II-ACQUIRED DISEASES OF THE SCLERA: -

Acquired disorders of the sclera are not common in domestic animals. Because of the inert collagenous nature of the sclera and its relatively poor blood supply, involvement of the sclera in disease processes is rare.

1-Episcleritis: -

Definition:

It is a localized nodular or diffuse inflammatory disorder affecting the episcleral tissues near the limbus. The nodules are immovable and the conjunctiva is freely movable over them in nodular form. The episcleral vessels are engorged with blood and overlying conjunctiva is congested and red in diffuse form.

Treatment:

Topical and subconjunctival corticosteroid administration.

2-Ocular nodular fasciitis (ONF): -

Definition:

It is a benign nodular lesions of connective tissue in the sclera, cornea and/or third eyelid. The lesions are localized and must be differentiated from nodular episcleritis, proliferative keratoconjunctivitis and focal neoplasms.

Treatment:

Surgical excision, as there is no respond to topical medication of corticosteroids.

3-Scleral tumors: -

Primary tumors of the sclera are uncommon. Melanomas or malignant melanomas are seen. Extension to the sclera from other tissues are more common. Squamous cell carcinomas are the common tumors extended from the conjunctiva and cornea in horse and cattle. Haemangiosarcomas and malignant melanomas are most likely to occur in dogs.

4-Episcleral hemorrhages: -

It has been previously described as subconjunctival hemorrhage.

5-Scleral trauma: -

Scleral trauma may leads to lacerations or perforation of the sclera. In equines the cause is severe blows to the eye while in small animals is due to fights with other animals or auto accidents. The ciliary body, iris and/or lens may prolapse through scleral wound. The extent of internal hemorrhage and retinal detachment determines if the eye will be visual following repair. The prolapsed tissues are replaced and the scleral wound is sutured with 6-0 non absorbable suture material.

6-Episcleral prolapse of periorbital fat in cattle: -

The postorbital fat can displace anteriorly between the sclera and Tenon's capsule to prolapse into the episcleral space. The condition may be congenital, or due to abnormal ocular muscle function. Exaggerated eye movement during examination may result in transient prolapse of fat.

Treatment:

The condition is not routinely treated because it does not affect vision.