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GHS on 7p

onasally along the location of the optic fissure whereas atypical iris colobomas are not associated with abnormal fissure closure and can occur elsewhere. Atypical iris colobomas usually have an intact iris root (Fig. 1-24).

Differentiation of choroidal and iris stroma is determined by the adjacent structures of the optic cup: the iris epithelium, anteriorly, and the future retinal pigment epithelium, posteriorly. In animals exhibiting primary abnormalities in differentiation of the outer layer of the optic cup, anterior and posterior segment colobomas are seen in a very specific distribution associated with the iris epithelium or RPE defects,25,26 and this is the most likely explanation for atypical uveal colobomas. The term lens coloboma is actually a misnomer, as this defect results from a lack of the zonular pull in the region of the coloboma rather than regional hypoplasia of the lens. Ciliary body colobomas are often associated with abnormal lens shape or subluxation or both.

FIGURE 1-21A-C. (A) Photograph of patient with left colobomatous microphthalmia and normal right eye. (B) Slit lamp view of the iris coloboma left eye. Note the pigment on anterior capsule of the lens. (C) Optic nerve coloboma of left eye with inferior choroidal coloboma that extended anteriorly to meet the iris coloboma seen in (B).

FIGURE 1-21A-C. (A) Photograph of patient with left colobomatous microphthalmia and normal right eye. (B) Slit lamp view of the iris coloboma left eye. Note the pigment on anterior capsule of the lens. (C) Optic nerve coloboma of left eye with inferior choroidal coloboma that extended anteriorly to meet the iris coloboma seen in (B).

Colobomatous microphthalmia with eyelid cyst syndrome may be unilateral or bilateral (see Fig. 1-28). Colobomatous cysts form from the inner layer (neuroectoderm) of the optic cup as it grows out of the persistent opening of the optic fissure. The lower lid cyst contains primitive vitreous contents that were not enclosed within the eye because the optic fissure did not close. The cyst has a stalk that connects to the microphthalmic eye. For those who are unaware of the syndrome, the lid cyst is often mistaken as an abnormal eye located in the lid.

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