Coloboma: Congenital anomaly in which some of the structures of the eye are absent due to incomplete fusion of the fetal intraocular fissure during gestation.Microphthalmos: Congenital or developmental anomaly in which the eyeballs are abnormally small.Anophthalmos: Congenital absence of the eye or eyes.Choanal Atresia: A congenital abnormality that is characterized by a blocked CHOANAE, the opening between the nose and the NASOPHARYNX. Blockage can be unilateral or bilateral; bony or membranous.Hypertelorism: Abnormal increase in the interorbital distance due to overdevelopment of the lesser wings of the sphenoid.Eye Abnormalities: Congenital absence of or defects in structures of the eye; may also be hereditary.Pupil Disorders: Conditions which affect the structure or function of the pupil of the eye, including disorders of innervation to the pupillary constrictor or dilator muscles, and disorders of pupillary reflexes.Abnormalities, MultipleIris: The most anterior portion of the uveal layer, separating the anterior chamber from the posterior. It consists of two layers - the stroma and the pigmented epithelium. Color of the iris depends on the amount of melanin in the stroma on reflection from the pigmented epithelium.PAX2 Transcription Factor: A paired box transcription factor that is essential for ORGANOGENESIS of the CENTRAL NERVOUS SYSTEM and KIDNEY.Posterior Eye Segment: The back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the VITREOUS HUMOR; RETINA; CHOROID; and OPTIC NERVE.Choroid: The thin, highly vascular membrane covering most of the posterior of the eye between the RETINA and SCLERA.Fundus Oculi: The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)Syndrome: A characteristic symptom complex.