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Iris Coloboma With Iris Heterochromia

Iris Coloboma With Iris Heterochromia HETEROCHROMIA of the iris associated with iris coloboma has been described only once in the literature as a rare finding.1 Herein we describe and illustrate a series of 13 cases to emphasize its frequent occurrence and propose a possible explanation for the cause of the iris coloboma–iris heterochromia association. As part of a detailed population study of congenital eye defects in Scotland, 75 children (aged 4-16 years) with iris colobomas were examined in detail. In 13 (17.3%) of these patients, there was a noticeable iris heterochromia (Figure 1), which is particularly striking in those cases where the unaffected eye is blue (Figure 2). In unilateral cases, the heterochromia is characterized by the darker iris being the one affected with the coloboma (Figure 3). In cases of bilateral iris coloboma with clinical microphthalmos and reduced corneal diameter (Table 1), the variation in iris color is inconsistent. A fundus coloboma (Figure 4) may be present, but not always. Figure 1. View LargeDownload Patient 6. Bilateral iris coloboma with iris heterochromia. A, Right blue eye with microphthalmos. B, Left brown eye. Figure 2. View LargeDownload Patient 258. Iris coloboma of the right brown eye with microphthalmos. Figure 3. View LargeDownload Patient 85. Iris coloboma of the right eye. View LargeDownload Iris Coloboma–Iris Heterochromia Association in 13 Patients* Figure 4. View LargeDownload Fundus coloboma of the right eye. The optic disc and macular region are involved. Comment Normal iris pigmentation is derived from cells in 2 layers.2 Anteriorly, there are melanocytes within the iris stroma and anterior border layer (there are fewer melanocytes in the blue iris, plus amelanotic cells containing nonpigmented granules). Posteriorly, pigmented granules lie within the cells of the posterior pigmented epithelium. Embryologically, the iris stroma is a mesenchymal or neural crest derivative, while the posterior pigmented epithelium is formed from the neuroectoderm of the optic cup. At the same time as closure of the embryonic fissure (5-7 weeks), a wave of neural crest cells migrates into the anterior chamber to be incorporated into the iris stroma.3 Normal iris formation is dependent on the closure of the embryonic fissure. A possible explanation for the iris coloboma–iris heterochromia association is that the abnormal closure of the embryonic fissure results in irregular (Figure 5) or excessive migration of neural crest cells into the iris stroma. Neural crest cell migratory dysfunction could be a causative factor in the formation of the iris coloboma. The high frequency of iris heterochromia–iris coloboma with reduced corneal size suggests that an increased density of pigmented cells within the iris stroma may be a contributing factor (Figure 2). In our series, iris coloboma–iris heterochromia occurred in as many as 17% (13 patients) of cases of iris coloboma. These 13 cases illustrate some possible mechanisms for the previously rarely recognized association of iris coloboma–iris heterochromia, and contribute to our understanding of normal and abnormal ocular embryogenesis. Figure 5. View LargeDownload Patient 238. Iris coloboma of the left eye. Note the irregular distribution of iris pigment. We are grateful to the Scottish Office, Edinburgh, for financial support of this work. Photographic assistance was provided by Angela Ellingford and Stephen C. McPherson, MCOptom. Reprints: Danny A. Morrison, BMedSc, FRCOphth, Department of Clinical Genetics, Molecular Medicine Centre, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland (e-mail: dannymorrison@ntlworld.com). References 1. Drews RCPico G Heterochromia associated with coloboma of the iris. Am J Ophthalmol. 1971;72827Google Scholar 2. Bron AJTripathi RCTripathi BJ The Iris: Wolff's Anatomy of the Eye and Orbit. 8th ed. New York, NY Chapman & Hall1997; 3. Tripathi BJTripathi RCWisdom J Embryology of the anterior segment of the human eye. Ritch RShields MBKrupin Teds. The Glaucomas Vol 12nd ed. St Louis, Mo Mosby Inc1995;Google Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Ophthalmology American Medical Association

Iris Coloboma With Iris Heterochromia

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Publisher
American Medical Association
Copyright
Copyright © 2000 American Medical Association. All Rights Reserved.
ISSN
0003-9950
eISSN
1538-3687
DOI
10.1001/archopht.118.11.1590
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Abstract

HETEROCHROMIA of the iris associated with iris coloboma has been described only once in the literature as a rare finding.1 Herein we describe and illustrate a series of 13 cases to emphasize its frequent occurrence and propose a possible explanation for the cause of the iris coloboma–iris heterochromia association. As part of a detailed population study of congenital eye defects in Scotland, 75 children (aged 4-16 years) with iris colobomas were examined in detail. In 13 (17.3%) of these patients, there was a noticeable iris heterochromia (Figure 1), which is particularly striking in those cases where the unaffected eye is blue (Figure 2). In unilateral cases, the heterochromia is characterized by the darker iris being the one affected with the coloboma (Figure 3). In cases of bilateral iris coloboma with clinical microphthalmos and reduced corneal diameter (Table 1), the variation in iris color is inconsistent. A fundus coloboma (Figure 4) may be present, but not always. Figure 1. View LargeDownload Patient 6. Bilateral iris coloboma with iris heterochromia. A, Right blue eye with microphthalmos. B, Left brown eye. Figure 2. View LargeDownload Patient 258. Iris coloboma of the right brown eye with microphthalmos. Figure 3. View LargeDownload Patient 85. Iris coloboma of the right eye. View LargeDownload Iris Coloboma–Iris Heterochromia Association in 13 Patients* Figure 4. View LargeDownload Fundus coloboma of the right eye. The optic disc and macular region are involved. Comment Normal iris pigmentation is derived from cells in 2 layers.2 Anteriorly, there are melanocytes within the iris stroma and anterior border layer (there are fewer melanocytes in the blue iris, plus amelanotic cells containing nonpigmented granules). Posteriorly, pigmented granules lie within the cells of the posterior pigmented epithelium. Embryologically, the iris stroma is a mesenchymal or neural crest derivative, while the posterior pigmented epithelium is formed from the neuroectoderm of the optic cup. At the same time as closure of the embryonic fissure (5-7 weeks), a wave of neural crest cells migrates into the anterior chamber to be incorporated into the iris stroma.3 Normal iris formation is dependent on the closure of the embryonic fissure. A possible explanation for the iris coloboma–iris heterochromia association is that the abnormal closure of the embryonic fissure results in irregular (Figure 5) or excessive migration of neural crest cells into the iris stroma. Neural crest cell migratory dysfunction could be a causative factor in the formation of the iris coloboma. The high frequency of iris heterochromia–iris coloboma with reduced corneal size suggests that an increased density of pigmented cells within the iris stroma may be a contributing factor (Figure 2). In our series, iris coloboma–iris heterochromia occurred in as many as 17% (13 patients) of cases of iris coloboma. These 13 cases illustrate some possible mechanisms for the previously rarely recognized association of iris coloboma–iris heterochromia, and contribute to our understanding of normal and abnormal ocular embryogenesis. Figure 5. View LargeDownload Patient 238. Iris coloboma of the left eye. Note the irregular distribution of iris pigment. We are grateful to the Scottish Office, Edinburgh, for financial support of this work. Photographic assistance was provided by Angela Ellingford and Stephen C. McPherson, MCOptom. Reprints: Danny A. Morrison, BMedSc, FRCOphth, Department of Clinical Genetics, Molecular Medicine Centre, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland (e-mail: dannymorrison@ntlworld.com). References 1. Drews RCPico G Heterochromia associated with coloboma of the iris. Am J Ophthalmol. 1971;72827Google Scholar 2. Bron AJTripathi RCTripathi BJ The Iris: Wolff's Anatomy of the Eye and Orbit. 8th ed. New York, NY Chapman & Hall1997; 3. Tripathi BJTripathi RCWisdom J Embryology of the anterior segment of the human eye. Ritch RShields MBKrupin Teds. The Glaucomas Vol 12nd ed. St Louis, Mo Mosby Inc1995;Google Scholar

Journal

Archives of Ophthalmology – American Medical Association

Published: Nov 1, 2000

Keywords: congenital coloboma of iris,heterochromic iris

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