Congenital Abnormalities of Eyes in Dogs
Richa Chourasia, Kritika Dhial and Shivangi Diwedi
PhD Scholar, College of Veterinary and Animal Sceinces, RAJUVAS, Bikaner
Email: chourasiaricha.27@gmail.com
Branch of embryology dealing with abnormal development and congenital anomalies is known as Teratology. There are many congenital abnormalities reported in dogs. Not all abnormalities are inheritable some are also due to toxicity and diseases during development/ organogenesis. Some anomaly can be seen immediately after birth while some can be seen.
Anopthalmos and Micropthalmos:
Anopthalmos is the total absence of eye ball. It can be due to suppression of the optic primordia during the development of fore brain or abnormal development of fore brain or because of teratogenic insult to the optic vesicles leading to its degeneration. It can be easily confused with extreme micropthalmos. It is a very rare genetic disease whose confirmative diagnosis can be done via histology which showed no evidence of eye/ orbital content.
Micropthalmos is the presence of eye smaller than the normal eye. In dogs it is frequently observed as a part of collie eye anomaly. It can also occur in eyes with multiple ocular anomalies like cataract, retinal dysplasia and anterior segment dysgenesis. A micropthamic eye can be functionally normal if all the internal eye structures remain proportional in size.
In micropthamic condition, anterior segment dygenesis can be seen easily in Saint Bernard and Doberman breed dogs, cataract in Old English sheepdog, Miniature Schnauzer and Cavalier King Charles Spaniel, persistent hyperplastic primary vitreous in Irish Woflhound; and retinal dysplasia in Saint Bernard and Doberman.
Cyclopia and Synopthalmus:
Cyclopia is the condition in which there is presence of single eye. In this case prosencephalon does not show any cleavage, there is on mid brain, one dorsal cyst and a single optic nerve and optic canal. The frontonasal process presents a proboscis (displaced nose) above the single orbit. The lids of the two eyes are fused around the single orbit.
Synopthalmus is the condition in which there is fusion of eyes in the midline. Both the conditions are life threatening.
Coloboma:
Coloboma is a condition in which a portion of the eye commonly a portion of uvea is lacking. In typical coloboma there is incomplete closure of the embryonic optic fissure, which can converted into orbital cyst if becomes severe. If it is moderate it can be diagnosed as a simple notch in the lower nasal quadrant of the pupil. These are usually located in inferonasal portion of the eye. Atypical coloboma occurs due to lack of induction of one tissue for another. In collie eye anomaly, colboma of optic nerve can be seen.
Persistent pupillary membrane:
In persistent pupillary membrane a strands of fetal tissue remain on the eye after birth. It is commonly seen in Basenjis, Pembroke and Cardigan Welsh Corgis, chow chows, and mastiffs.
Dermoid:
Tumour like cyst can be senn attached to the conjunctiva or cornes with hairs on them.
Persistent hyperplastic primary vitreous (PHPV) or persistent hyperplastic tunica vasculosa lentis (PHTVL):
It is a disease condition in which the regression of ophthalmic embryonic vasculature does not occur normally. Because the normal embryologic vitreal vasculature is intimately associated with the posterior lens surface/capsule and exits the eye at the posterior pole, abnormalities of these areas, especially the posterior lens, are also frequently seen in patients affected by PHPV. The degree of severity is variable ranging from an incidental finding of a retrolental fibrous strand to complete hyphema, severe ocular lens malformations, secondary glaucoma and patent, aberrant vasculature within the lens and vitreous. It is commonly seen in Briards, Cocker Spaniel, Beagles and Rottweilers. In this patient is usually presented for the treatment of cataract.
https://www.pashudhanpraharee.com/horners-syndrome-in-dog/
https://www.petmd.com/dog/conditions/eyes/c_dg_congenital_eye_defects
