GLOSSARY of Ocular Birth Defects

Here is a Glossary of Ocular Birth Defects for parents and children to gain further understanding.

Anomoly: Designates the “ocular” findings alone.

Causes: Anophthalmia/microphthalmia may be isolated (i.e. with no other systemic involvement) or may be a part of a syndrome with other associated anomalies (Environmental, Heritage, Unknown).

Charge Syndrome: (C.H.A.R.G.E) Coloboma, Heart Defects, Atresia (choanal), Retarded Growth, Genital Abnormalities, Ear Abnormalities/Deafness.

Clinical Anophthalmos: Without a specific diagnosis use this inclusive term.

Clinical Congenital Anophthalmos – The difference between congenital anophthalmos and extreme microphthalmos can only be done by a histological examination. Because such an exam is impossible in every case, the term: Clinical Anophthalmos should be used to denote the majority of cases wherein the eye appears to be absent.

Common Eyelid Malformations: Anklyoblepharon (Fused or partially fused eyelids), Blepharophmos (Eyelids Abnormally Small), Telecanthus (Abnormal increase in distance between the medial canthi of eyelids), Epicanthus (Vertical fold of skin over the nasal canthus. Normal in Mongolian Peoples).

Complex Micropthalmia: Refers to an eye with anterior segment dysgenesis and/or posterior segment dysgenesis. Decrease in TAL can be mild, moderate, or severe.

Congenital: Present at Birth.

Congenital Anophthalmia: Catch all term – Clinical Anophthalmia.

Congenital Micropthalmos: A developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eyes are abnormally small and have anatomic malformations.

Degenerative Anophthalmos: Occurs when the eye(s) start to form and for some reason degenerates or is destroyed. The occurrence of anophthalmos on one side and microphthalmos on the other points to such a degenerative process.

De Novo Mutation: An alteration in a gene that is present for the FIRST TIME in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents or in the fertilized egg itself. (Synonyms: New gene mutation, new mutation).

Differential Diagnosis: Crytophthalmos (Hidden Eye) Abnormal fusion of the entire eyelid margin with the absence of eyelashes resulting in a continuous sheet of skin extending from the forehead to the check.

Environmental Causes: (Teratogens) Rubella, Alcohol and Drug Abuse (FAS), Thalidomide, Retinoic Acid, Exposure to Benomyl).

Genetics: The GENE is the basic unit of heredity, consisting of a segment of DNA arranged in a linear manner along a chromosome. A gene codes for a specific protein or segment of protein leading to a particular characteristic or function.

Heritable Causes: Genetic/Chromosome Abnormalities.

HotSpot Mutation: DNA Sequences of high susceptibility to mutation due to some inherent instability.  A region where the mutations are observed with greater frequency.

MAC: (microphthalmia-anophthalmia-coloboma) Common term used to group children who are present with congenital ocular disorders.

Measurement of the EYE:  *Done by 3D CT Imaging*

TAL – Total axial length of the globe (Neonate = 6.8mm / Adult = 7.3mm)

ASL – Anterior segment length of globe (Neonate = 6.8mm / Adult = 7.3mm)

PSL – Posterior segment length of globe (Neonate = 10.2mm / Adult = 16.5mm)

Nanophthalmos (Dwarf-eye): Is a subtype of simple microphthalmia characterized by micro-cornea, TAL less than 18mm, high hyperopia (8 diopters). Angle closure glaucoma is common. Eye can have vision.

Orbital Bone Malformations: Micro-Orbitism.

Primary Anophthalmos: Is a complete absence of the eye(s) tissue due to the failure of the part of the brain that forms the eye. This condition occurs sporadically, tends to be bilateral and in most cases the child is otherwise physically well formed.

Secondary Anophthalmos: Is a type that is seldom seen by the Ocularist. It involves a wide spread change affecting the anterior end of the neural tube. The result is usually a non-viable child with cerebral deformities and numerous other abnormalities.

Severe Micropthalmia: Refers to a globe that is severely reduced in size with a corneal diameter less than 4mm and a TAL less than 10mm at birth.

Simple Micropthalmia: Refers to an eye that is anatomically intact except for its short TAL.

Statistics Related to MAC Anomalies: Prevalence – True Anophthalmia: 1 in 100,000 births Microphthalmia: 1 in 10,000 births / Canadian Survey of 449 cases  *34% have mild microphthalmia, *In severe cases 51% are bilateral, *72% have other eye malformations, 25% of severe cases did not survive infancy.

Syndrome: Includes systematic findings such as dental anomalies, maxillary hypoplasia, ocular differences, hypotelorism, cutis navel, and heart defects.

Trisomy: The presence of a single extra chromosome, yielding a total of three chromosomes of that particular type instead of a pair. Partial trisomy refers to a presence of an extra copy of a segment of a chromosome.

Types of Complex Microphthalmia: Anterior Segment Dysgenesis (Peters Anomaly), Posterior Segment Dysgenesis (Cataract) Persistent fetal vasculature *(PHPV) *Persistent hyperplastic primary vitreous Choriorentinal coloboma.