China
Africa
Explore chapters and articles related to this topic
An Approach to Visual Loss in a Child
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Muhammad Hassaan Ali, Stacy L. Pineles
Congenital anomalies in which the eyeball is either absent or abnormally small in size are called anophthalmos and microphthalmos, respectively (29). Congenital uveal coloboma is the commonest congenital anomaly which occurs when the embryonic fissure fails to fuse completely by sixth week of development (30,31). Coloboma involving the macula or the optic nerve causes severe visual loss. Many studies have shown that these anomalies are leading causes of blindness in children with congenital visual disorders in many parts of Asia (32,33). No cause of these anomalies can be detected prenatally even though detailed investigations and genetic testing have been proposed in the subsequent siblings of an affected patient. Whether there is a role of folic acid in preventing such congenital malformations remains yet to be explored. These patients are generally managed with best refractive correction and low vision aids. Some people also advocate applying laser to the margins of the coloboma to avoid any impending retinal detachment (34).
Cranial Neuropathies II, III, IV, and VI
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Tanyatuth Padungkiatsagul, Heather E. Moss
Colobomas occur when there is incomplete closure of the embryonic fetal fissure that forms the optic cup and stalk. This results in incomplete formation of certain part of the eye. When the optic nerve is involved, the disc appears excavated usually inferiorly, with normal vessels and a normal superior rim.
Prenatal Cocaine Exposure and the Eye
Published in Richard J. Konkol, George D. Olsen, Prenatal Cocaine Exposure, 2020
William V. Good, Beatrice Latal Hajnal, Donna M. Ferriero
Ocular colobomas occur in a wide variety of recessive syndromes, as an isolated dominant gene disorder, or in trisomy 13. The relationship of coloboma to in utero drug exposure is hypothetical, and the one report to date could represent a real effect of cocaine, or may simply be a coincidence. Further research and follow-up of greater numbers of babies will be helpful in clarifying this issue.
Continuous Curvilinear Capsulorhexis – A Practical Review
Published in Seminars in Ophthalmology, 2022
Coloboma is a congenital condition in which part of the normal ocular tissue is missing, due to incomplete closure of the embryonal fissure.44 The clinical significance and implications for cataract surgery varies according to the involved eye structures.55 Lens coloboma is caused by incomplete zonular differentiation during the embryonal period, and is often an isolated finding.55 The zonular defect results in diminished or asymmetrical tension on the capsule, alterations in capsular volume and form, and the crystalline lens is therefore often harder, more prone to subluxation or dislocation, and advanced nuclear cataract can develop at young age.44 Hence, lens coloboma, as well as uveal coloboma which affects the iris, can complicate capsulorhexis with a higher risk of rhexis extensions, posterior capsular tears and vitreous loss during rhexis formation and phacoemulsification.44,45 Iris hooks or implementation of a capsular tension ring could facilitate cataract extraction, but their use requires a well sized and shaped CCC.22,44,54,55 Repair of iris coloboma along with cataract extraction is possible, but it probably does not improve the functional result and can be done for cosmetic reasons.44
De novo frameshift mutation in YAP1 associated with bilateral uveal coloboma and microphthalmia
Published in Ophthalmic Genetics, 2022
Charles DeYoung, Bin Guan, Ehsan Ullah, Delphine Blain, Robert B. Hufnagel, Brian P. Brooks
YAP1 (OMIM 606608) encodes Yes-associated protein 1, a known effector of the Hippo-signaling pathway, and is implicated in the development of several organs, including the eye (1). YAP1 activation is also known to play a role in the initiation, progression, and metastasis of multiple cancers and is being investigated as a potential target for cancer treatment (2). In situ hybridization of human embryonic tissue has detected YAP1 expression in the developing human eye, neural tube, brain, and kidney (3). YAP1 mutations have previously been linked to coloboma, which is characterized by the congenital loss of normal tissue in or around the eye (4). The resulting defects can cause a range of visual dysfunctions, depending on the size and location of the coloboma. Here, we present a one-year-old male infant with bilateral uveal colobomata and microphthalmia in the right eye, with a de novo YAP1 frameshift mutation.
Novel heterozygous variants in PXDN cause different anterior segment dysgenesis phenotypes in monozygotic twins
Published in Ophthalmic Genetics, 2021
Angela Y. Zhu, Gregory Costain, Cheryl Cytrynbaum, Rosanna Weksberg, Ronald D. Cohn, Asim Ali
The patients were monochorionic, diamniotic twin girls who were born at 30 + 1 weeks gestation by emergency C-section due to concerns regarding severe intrauterine growth restriction (IUGR) of Twin B; a growth discrepancy was diagnosed at 17 weeks gestation by ultrasound, but there was no evidence for twin-to-twin transfusion. Both parents were of mixed European descent. The parents were generally in good health, but the mother had a history of recurrent early pregnancy losses (estimated 6) prior to the birth of the patients; the father had a history of epilepsy as a child. Neither parent had any diagnosed ocular malformations. There was a reported history of an eye “coloboma” with congenital monocular vision loss in the mother’s maternal grandmother, but no other history of eye defects in the family and no known consanguinity (Figure 1).