I. Eye Development
Sara Thomasy DVM, PhD, DACVO Mouse Day 8 Dog Day 11 Eye Fields
Mouse Day 7 Dog Day 10 Prosencephalon
https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 8 Dog Day 12
Cyclopia Cyclopia - Formation of a single median globe Synophthalmia – Two incompletely separated or fused globes Concurrent severe craniofacial defects Veratrum californicum . Day 14 of gestation in sheep Steroidal alkaloids . Cyclopamine and jervine . Inhibit sonic hedgehog signal transduction during gastrulation Affects midline neural plate
Corn Lily or False Hellebore Day 15
Optic vesicle
Mouse Day 9.5 Optic stalk
https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 9.5 Dog Day 15
Optic vesicle
Microphthalmia
Optic stalk
https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Optic vesicle deficiency Corresponding small palpebral fissure Failure of normal optic cup growth . Failure of fusion of the choroid fissure → colobomas . Failure to establish normal IOP
Associated with a myriad of ocular defects ASD PHPV Neural plate deficiency Cataract Retinal dysplasia Colobomatous malformations Merle ocular dysgenesis
Intraretinal space
Mouse Day 11 Dog Day 18
https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Mouse Day 11 Iris coloboma Dog Day 18 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm “Defect” Failure of fusion of the choroid fissure “Typical colobomas” at the 6 o’clock position Abnormal differentiation of the outer optic cup “Atypical colobomas” at other locations
Charlois Collie Collie Day 25
Mouse Day 11 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm
Persistent keratolenticular attachment Classic example: Peter’s anomaly Corneal opacity with stromal & DM defects (B) Persistent pupillary membrane (A) . Iris hypoplasia (C) . Anterior polar cataract (D)
B A D C Pupillary Provides nourishment membrane to the developing lens Failure of the pupillary membrane to regress Strands arise from iris collarette DDx: Synechiae arise from pupillary margin
Classified by location: Iris-to-cornea . Iris-to-iris . Iris-to-lens
Predisposed breeds: Basenji Mastiff Pembroke Welsh Corgi Chow Chow Week 8 Postnatal ↑ IOP in animals <6 months of age . Marked buphthalmos → scleral elasticity Arrest in normal development of AC . Concurrent ocular anomalies (eg. ASD)
↑ IOP in animals <6 months of age . Marked buphthalmos → scleral elasticity Arrest in normal development of AC . Concurrent ocular anomalies (eg. ASD)
Failure of the PL to rarify during development “Primary” glaucoma . Many predisposed breeds
http://www.eyedvm.com/eyeinfo.html Day 25
Hyaloid artery Lens Mouse Day 11.5 vesicle
Failure of the hyaloid artery to regress
Rat Concurrent cataract Challenging surgery! Ultrasound all surgical candidates
Failure of vascular regression Normal vitreous - antiangiogenic Concurrent anomalies Microphthalmia Microphakia Cataract Retinal dysplasia Inherited trait Doberman Staffordshire Bull Terrier
Rat
Day 29
Mouse Day 13 https://syllabus.med.unc.edu/courseware/embryo_images/unit-eye/eye_htms/eyetoc.htm Abnormal formation of 1º 0r 2º lens fibers Nuclear Nonprogressive Abnormal lens vesicle invagination, separation or defects in lens epithelium/capsule Peripheral
Rat Miniature Schnauzer Autosomal recessive Bilateral Posterior cortex → rapid progression Microphthalmia
Shastry BS & Reddy VN. Biochem & Biophys Res Commun. 1994 ;203: 1663-7. Zhang et al. IOVS. 1991;32: 2662-5. Gelatt et al. JAVMA. 1983;183:99-102. Gelatt et al. AJVR. 1983;44:1130-2. Rat Microphakia Immature Cataract Microphakia Hypermature Cataract Elongated CB processes Small optic vesicle → small lens vesicle Concurrent microphthalmia Abnormal optic vesicle orientation → small lens vesicle ± Cataract ↑ risk of lens luxation
Multifocal retinal dysplasia
Dog “Difficult formation” Incomplete contact between inner & outer optic cup Classified by severity: Focal/multifocal → retinal folds → inequity in growth of inner and outer optic cup
Dog Dog “Difficult formation” Incomplete contact between inner & outer optic cup Classified by severity: Focal/multifocal → retinal folds → inequity in growth of inner and outer optic cup Geographic Diffuse with retinal detachment
Dog Dog Optic nerve hypoplasia
Dog RGC axon guidance defect Abnormal retinal/ON development ↓/Absent vision (2/8 cases visual) Histologic features: Vestigial ectopic ON elements (no axons) – 6/8 cases Vitreous extension of retinal vessels – 5/8 cases Predisposed breeds: . Poodle . Shih Tzu
da Silva EG, et al. Vet Ophthalmol. 2008 ;11:23-29. Primary failure of RGC development Failure of RGC axon initiation &/or guidance Failure of RGC axons to reach optic disc Concurrent ASD (3/5 cases) Lack of: Retinal vessels NFL RGCs
da Silva EG, et al. Vet Ophthalmol. 2008 ;11:23-29. Day 32
Mouse Day 17
Abnormal differentiation of an isolated group of cells (early) Abnormal invagination of ectodermal tissue (late) Common locations (surface ectoderm derived): Cornea (at the lateral limbus) Eyelid Conjunctiva Choristoma – Normal tissue in an abnormal location Corneal dermoid Hamartoma – Tissue normal to that location but in an abnormal configuration Eyelid dermoid
Predisposed breeds: Dachshund Dalmation Doberman German Shepherd St. Bernard
Eyelid Agenesis Abnormal orientation of the optic vesicle as it contacts surface ectoderm Temporal aspect of superior eyelid Common sequelae: Exposure keratitis Common concurrent abnormalities: Anterior segment dysgenesis Coloboma Choroid Optic nerve Photo courtesy of Dr. Daniel Dorbandt, University of Illinois
Roberts & Bistner procedure . Dziezyc & Millichamp modification Z-plasty Cutler-Beard technique Mustarde cross lid technique Sliding skin grafts Cryotherapy Collagen injection Lip to lid transposition