Ocular colobomata

[Ocular coloboma and results of brain MRI: preliminary results]

INTRODUCTION

Congenital ocular colobomas are the result of a failure in closure of the embryonal fissure. We present a prospective study (2007-2011) in which we report brain MRI findings in children with ocular coloboma.

PATIENTS AND METHODS

Thirty-five children (54 eyes) were included; 15 boys, 20 girls with a median age of 24.0 months (1.0-96.0) at first presentation. Within 2 to 3 months following complete ophthalmologic examination, brain MRI was performed.

RESULTS

Colobomas were bilateral in 19 cases and unilateral in 16 cases. Eleven different types of coloboma were identified. Of 54 eyes, 74% demonstrated optic nerve coloboma, of which 28 were severe. Of 35 MRI's performed, abnormalities were present in 86%: gyration abnormalities (n=21), lateral ventricular dilatation (n=17), dilatation of the Virchow-Robin and subarachnoid spaces (n=14), signal abnormalities and brain stem malformations (n=14), white matter signal abnormalities (n=11), corpus callosum abnormalities (n=10). Most of these abnormalities were related. Gyration abnormalities were the most frequent. There was no significant association between the severity of the coloboma and the abnormalities found (P=1.0). Likewise, there was no significant association of gyration abnormalities with the severity of coloboma in children (P=1.0).

DISCUSSION AND CONCLUSION

This study shows, for the first time, the existence of frequent cerebral abnormalities on MRI in children with ocular coloboma. The most common abnormality being gyration abnormalities, in 60% of cases.

Surgical management and scheimpflug analysis of an atypical lens coloboma

A lens coloboma is not a true coloboma; it is just a zonular absence that causes a defect in the lens equator and hence a more spherical lens. It can be isolated or in association with iris, choroid or retinal colobomas. Typically the defect is present at the site of the embryonic fissure, but it can be present elsewhere. This congenital defect can cause amblyopia, especially when it is associated with cataract. We describe a case of a 39-year-old male with an atypical coloboma that was managed successfully with phacoemulsification, capsular tension ring and intraocular lens implantation. Scheimpflug image analysis and full ophthalmological assessment were performed. Scheimpflug images demonstrated a notching of the lens equator and an absence of zonulae. During the surgical procedure an ophthalmic viscosurgical device was used to tamponade the vitreous, and after continuous curvilinear capsulorhexis the capsular tension ring was inserted to allow the surgeon to perform a safe phacoemulsification.

A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position

Previously we developed a mathematical model for describing the retinal nerve fiber bundle trajectories in the superior-temporal and inferior-temporal regions of the human retina, based on traced trajectories extracted from fundus photographs. Aims of the current study were to (i) validate the existing model, (ii) expand the model to the entire retina and (iii) determine the influence of refraction, optic disc size and optic disc position on the trajectories. A new set of fundus photographs was collected comprising 28 eyes of 28 subjects. From these 28 photographs, 625 trajectories were extracted. Trajectories in the temporal region of the retina were compared to the existing model. In this region, 347 of 399 trajectories (87%) were within the 95% central range of the existing model. The model was extended to the nasal region. With this extension, the model can now be applied to the entire retina that corresponds to the visual field as tested with standard automated perimetry (up to approximately 30° eccentricity). There was an asymmetry between the superior and inferior hemifields and a considerable location-specific inter-subject variability. In the nasal region, we found two "singularities", located roughly at the one and five o'clock positions for the right optic disc. Here, trajectories from relatively widespread areas of the retina converge. Associations between individual deviations from the model and refraction, optic disc size and optic disc position were studied with multiple linear regression. Refraction (P = 0.021) and possibly optic disc inclination (P = 0.09) influenced the trajectories in the superior-temporal region.

Organogenesis of mild ocular coloboma in FLS mice: failure of basement membrane disintegration at optic fissure margins

Fatty Liver Shionogi (FLS) mice have been shown to develop a hereditary disorder characterized by localized retinochoroidal defects of the ventral fundus very similar to human typical ocular coloboma without microphthalmia. The objective of this study was to determine when and how the failure of the optic fissure closure occurs, and to clarify the disturbed mechanism of basement membrane disintegration during embryonal stage in FLS mice. Fetuses at day 11.5-15.5 of gestation were obtained from dams of FLS and BALB/c strain of mice. Coronal serial sections through the eye were examined by light and electron microscopy. The sections were followed by observation of the basement membrane using reaction with periodic acid-Schiff (PAS) reagent and immunohistochemical staining with anti-Laminin and anti-Type IV collagen antibodies. Both optic fissure margins closely approached each other up to GD 11.5 in all FLS and BALB/c embryos. The inner and outer layers of the optic cup did not normally fuse at midlenticular levels of the optic fissure in almost 70% of FLS fetuses by GD 15.5, whereas both margins were completely fused in all BALB/c fetuses of the same gestational day. In the FLS fetuses at GD 12.5, rolling on one side of fissure margins and consequent asymmetry were observed at the ventral optic fissure. The basement membrane persisted after the close contact of both sides of the fissure margins during GD 11.5 and 15.5. Ultrastructurally, the basal lamina was not disintegrated and mesenchymal cells intervened between the two neuroepithelial layers, resulting in complete separation of both fissure margins at GD 13.0. It is highly probable that the disturbed basement membrane disintegration right before optic fissure closure causes mild ocular coloboma without microphthalmia in FLS mice.

Isolated microcornea: case report and relation to other "small eye" phenotypes

Isolated microcornea is a very rarely-described condition of reduced cornea size (less than 11 mm horizontal diameter) in an individual without other significant ocular (or systemic) findings. This case report describes the biometric features of a boy with isolated microcornea (the youngest and most completely described patient to the best of our knowledge) and suggests that the condition is the same entity as relative anterior microphthalmos.

Incidence, ocular findings, and systemic associations of ocular coloboma: a population-based study

OBJECTIVE

To describe the incidence, ocular findings, and systemic associations of coloboma in a population-based cohort of children.

METHODS

We retrospectively reviewed the medical records of pediatric (aged <19 years) patients diagnosed as having ocular coloboma from January 1, 1968, through December 31, 2007, as residents of Olmsted County, Minnesota.

RESULTS

Thirty-three children were newly diagnosed as having ocular coloboma (annual incidence, 2.4 per 100,000 residents <19 years old; prevalence, 1 in 2077 live births). Median patient age at diagnosis was 3.9 months (range, 2 days to 18.4 years), and 22 patients (67%) had unilateral involvement. Twelve patients (36%) had involvement of the anterior segment only, 13 (39%) of the posterior segment only, and 8 (24%) of both. During median ophthalmologic follow-up of 9.2 years (range, 13 days to 35.9 years), 19 patients (58%) had other ocular disorders, including amblyopia in 11 (33%) and strabismus in 10 (30%). During median medical follow-up of 16.8 years, 22 patients (67%) were diagnosed as having a nonocular disorder, including abnormal development in 12 (36%) and CHARGE (coloboma, heart defects, choanal atresia, retarded growth and development, genital abnormalities, and ear anomalies) syndrome in 4 (12%).

CONCLUSIONS

Ocular coloboma occurred in 1 in 2077 live births. More than half of the patients were diagnosed as having an ocular disorder other than coloboma, including strabismus and amblyopia in approximately one-third. Two-thirds of patients were diagnosed as having a nonocular disorder, including CHARGE syndrome in 1 in 8 patients.

Intact retinal tissue and retinal pigment epithelium identified within a coloboma by high-speed, ultrahigh-resolution optical coherence tomography

PURPOSE

The purpose of this study was to report on a posterior segment coloboma manifesting unusual morphology as determined by high-speed, ultrahigh-resolution optical coherence tomography imaging.

METHODS

A 47-year-old woman with bilateral colobomas was evaluated by fundus examination and high-speed, ultrahigh-resolution optical coherence tomography imaging.

RESULTS

Imaging with high-speed, ultrahigh-resolution optical coherence tomography showed intact retinal pigment epithelium within the posterior segment coloboma. Most of the retinal layers seemed to continue into the coloboma, although they exhibited slight attenuation. The external limiting membrane was clearly visible continuing within the coloboma, suggesting that Müller cells and the inner segments of the photoreceptors were still present in this area. The junction between the inner and outer segments of the photoreceptors ended at the margin of the coloboma, which may be because of either photoreceptor disruption or a change in the orientation of the outer segments.

CONCLUSION

High-speed, ultrahigh-resolution optical coherence tomography imaging showed the presence of Müller cells and photoreceptor inner segments within a posterior segment coloboma. The retinal pigment epithelium was intact within the coloboma, representing an unusual morphology.

Disorders of pupillary structure and function

Neurologists are frequently consulted because of a pupillary abnormality. An unequal size of the pupils, an unusual shape, white colored pupils, or a poorly reactive pupil are common reasons for referral. A directed history and careful observation of the iris and pupil movements can bear out ocular pathology such as congenital or structural anomalies as the cause of abnormal pupils. Thereafter, it is important to evaluate the neurologic causes of anisocoria and poor pupil function. The first part of this article emphasizes pupillary abnormalities frequently encountered in infants and children and discusses some of the more common acquired iris structural defects. The second part focuses on evaluation of lesions in the neural pathways that result in pupillary dysfunction, with particular attention to those conditions having neurologic, systemic, or visual implications.

Spontaneous closure of a posttraumatic scleral fistula in an atypical choroidal coloboma

BACKGROUND

Scleral fistulas have been reported to occur in choroidal colobomas, and their repair has been described in the literature. Spontaneous closure of a posttraumatic fistula has not been reported.

PURPOSE

To describe the occurrence of posttraumatic scleral fistula formation and its spontaneous closure in an eye with an atypical choroidal coloboma.

METHODS

Interventional case report.

RESULTS

Spontaneous closure of the posttraumatic scleral fistula was noted at 1-month follow-up. This was documented clinically and confirmed by B-scan ultrasound.

CONCLUSION

Scleral fistula formation can occur at the base of a choroidal coloboma after blunt injury, and this can close spontaneously over a period of time.

Progenitor cells of the rod-free area centralis originate in the anterior dorsal optic vesicle

Background

Nervous system development is dependent on early regional specification to create functionally distinct tissues within an initially undifferentiated zone. Within the retina, photoreceptors are topographically organized with rod free area centrales faithfully generated at the centre of gaze. How does the developing eye regulate this placement? Conventional wisdom indicates that the distal tip of the growing optic vesicle (OV) gives rise to the area centralis/fovea. Ectopic expression and ablation studies do not fully support this view, creating a controversy as to the origin of this region. In this study, the lineage of cells in the chicken OV was traced using DiI. The location of labelled cells was mapped onto the retina in relation to the rod-free zone at embryonic (E) 7 and E17.5. The ability to regenerate a rod free area after OV ablation was determined in conjunction with lineage tracing.

Results

Anterior OV gave rise to cells in nasal retina and posterior OV became temporal retina. The OV distal tip gave rise to cells above the optic nerve head. A dorsal and anterior region of the OV correlated with cells in the developing rod free area centralis. Only ablations including the dorsal anterior region gave rise to a retina lacking a rod free zone. DiI application after ablation indicated that cells movements were greater along the anterior/posterior axis compared with the dorsal/ventral axis.

Conclusion

Our data support the idea that the chicken rod free area centralis originates from cells located near, but not at the distal tip of the developing OV. Therefore, the hypothesis that the area centralis is derived from cells at the distal tip of the OV is not supported; rather, a region anterior and dorsal to the distal tip gives rise to the rod free region. When compared with other studies of retinal development, our results are supported on molecular, morphological and functional levels. Our data will lead to a better understanding of the mechanisms underlying the topographic organization of the retina, the origin of the rod free zone, and the general issue of compartmentalization of neural tissue before any indication of morphological differentiation.

Bilateral typical complete colobomas in a donkey: retinographic and fluorangiographic description

An 18-year-old male donkey was referred with a history of blindness. On ocular examination a complete bilateral typical colobomatous defect involving iris, ciliary body, lens, choroid, retina and optic nerve was observed. An optic pit was presented at the temporal side of the right optic head. Ophthalmoscopic and fluorangiographic characteristics are described.

Case report and literature review of inferior rectus muscle aplasia in 16 Japanese patients

PURPOSE

To describe clinical features of inferior rectus muscle aplasia in Japanese patients and to gain insight into its pathogenesis.

METHODS

Case presentation and literature review of 16 Japanese patients with inferior rectus muscle aplasia.

RESULTS

The age at presentation of 16 patients (9 females, 4 males, and 3 with unknown gender) varied from 7 months to 73 years (mean, 21.8 years). The inferior rectus muscle was absent on the right side in 10 patients, on the left side in 4 patients, and on both sides in 2 patients. Structural anomalies of the eye globe, such as microphthalmos, microcornea, and coloboma of varying degrees, were present on the ipsilateral side of the inferior rectus muscle aplasia in 4 patients and on the contralateral side in 1 patient. As surgical findings, anomalous inferiorly located insertion of the medial rectus muscle was discovered in 5 patients: 1 patient in association with microcornea and iris coloboma. Frequent surgical procedures were recession or tenotomy of the superior rectus muscle, combined with downward transposition of the entire or partial tendons of the medial rectus and lateral rectus muscle to the medial and lateral end, respectively, of the putative inferior rectus muscle insertion.

CONCLUSIONS

The association of coloboma with inferior rectus muscle aplasia suggests that abnormal optic fissure closure during embryogenesis might underlie the muscle aplasia.

Optic nerve dysplasia and renal insufficiency in a family with a novel PAX2 mutation, Arg115X: further ophthalmologic delineation of the renal-coloboma syndrome

Renal-coloboma syndrome, an autosomal dominant disorder associated with mutations in PAX2, is characterized by colobomatous eye defects, renal hypoplasia, vesicoureteral reflux, high-frequency hearing loss, and rarely central nervous system abnormalities. We identified a three-generation family with optic nerve colobomatous dysplasia and renal disease. We report the identification of a novel mutation in PAX2 in this family with renal-coloboma syndrome, Arg115X. We also report on the ocular and extraocular manifestations of PAX2 mutations for all cases of renal-coloboma syndrome reported to date.

Congenital fibrosis of the extraocular muscles type 1, distinctive conjunctival changes and intrapapillary disc colobomata

A 6-month-old boy presented with a congenital eye movement disorder consistent with congenital fibrosis of the extraocular muscles type 1 (CFEOM1). Mutational analysis confirmed the most common mutation in the CFEOM1 gene KIF21A. In addition to the typical findings in CFEOM1, distinctive conjunctival changes and small bilateral optic disc colobomata were also noted. It is suggested that optic disc colobomata represent a new association of CFEOM1.

The temporal requirement for vitamin A in the developing eye: mechanism of action in optic fissure closure and new roles for the vitamin in regulating cell proliferation and adhesion in the embryonic retina

Mammalian eye development requires vitamin A (retinol, ROL). The role of vitamin A at specific times during eye development was studied in rat fetuses made vitamin A deficient (VAD) after embryonic day (E) 10.5 (late VAD). The optic fissure does not close in late VAD embryos, and severe folding and collapse of the retina is observed at E18.5. Pitx2, a gene required for normal optic fissure closure, is dramatically downregulated in the periocular mesenchyme in late VAD embryos, and dissolution of the basal lamina does not occur at the optic fissure margin. The addition of ROL to late VAD embryos by E12.5 restores Pitx2 expression, supports dissolution of the basal lamina, and prevents coloboma, whereas supplementation at E13.5 does not. Surprisingly, ROL given as late as E13.5 completely prevents folding of the retina despite the presence of an open fetal fissure, showing that coloboma and retinal folding represent distinct VAD-dependent defects. Retinal folding due to VAD is preceded by an overall reduction in the percentage of cyclin D1 positive cells in the developing retina, (initially resulting in retinal thinning), as well as a dramatic reduction in the cell adhesion-related molecules, N-cadherin and beta-catenin. Reduction of retinal cell number combined with a loss of the normal cell-cell adhesion proteins may contribute to the collapse and folding of the retina that occurs in late VAD fetuses.

Bilateral macular detachment caused by bilateral optic nerve malformation in a papillorenal syndrome due to a new PAX2 mutation

PURPOSE

Papillorenal syndrome is an autosomal dominant entity due to PAX2 gene mutation, involving optic nerve and renal malformations.

METHODS

The authors report a 19-year-old man with bilateral macular detachment associated with optic nerve pit in one eye and morning glory syndrome in the other eye. The patient underwent three-port pars plana vitrectomy, endolaser photocoagulation, and C3F8 gas tamponade in his best eye. A medical history of vesicoureteric reflux and kidney hypoplasia led to genetic analysis.

RESULTS

Molecular genetic PAX2 analysis revealed a novel nondescribed mutation in exon 3. One year postoperatively, ophthalmologic outcomes were satisfactory with complete flattening of the retina and improvement of the best-corrected visual acuity to 11/10.

CONCLUSIONS

PAX2 is involved in the optic vesicles, genital tracts, kidney, and central nervous system embryogenic development. The association of optic nerve and renal malformations should lead to the suspicion of papillorenal syndrome with PAX2 mutation.

A clinical and optical coherence tomography study of choroidal colobomas

PURPOSE OF REVIEW

This paper reviews current understanding of coloboma of the choroid, as evaluated clinically and using optical coherence tomography.

RECENT FINDINGS

Studies of the margin of coloboma of the choroid with optical coherence tomography revealed several interesting features, including variability in transition from normal retina to intercalary membrane (gradual or abrupt), presence of subclinical retinal detachments, focal communications between the subretinal space and subintercalary membrane space in eyes with extra-colobomatous retinal detachments, and inward humping of the eye wall in some cases. Pathological studies have stressed the importance of the intercalary membrane and the margin of coloboma as barriers for occurrence of retinal detachments. Vitrectomy and silicone oil tamponade could correct these retinal detachments in a majority of cases.

SUMMARY

Optical coherence tomography can provide insight into pathology at the margin of the coloboma. Coupled with knowledge from histopathological studies, this information can guide the management of retinal detachments secondary to coloboma of the choroid with a high degree of success.

Ocular colobomata, polydactyly, cleft palate and panhypopituitarism: a new syndrome

We describe a male patient with ocular colobomata, cleft palate, polydactyly, panhypopituitarism and possible craniosynostosis, whom we have followed for 30 years. Although there are some similarities to other documented syndromes, this previously unreported combination of features appears to constitute a new syndrome.

Ocular anomalies and holoprosencephaly in a lamb

The brain and eyes from a 1-day-old, male mixed-breed lamb with bilateral microphthalmia were examined. Bilateral ventral colobomata of choroid, sclera, retina and optic nerve were accompanied by agenesis of the optic nerve, and dilated lateral and third ventricular cavities that communicated with the subarachnoid space. Abundant neuroretinal tissue extending through the colobomatous defect to retro-orbital connective tissue, the meningeal surface and ventricular system were identified by histologic examination. Positive immunolabeling of these structures for recoverin (a photoreceptor marker) established the retinal origin of ectopic structures. The optic nerve was replaced by a short fibrous stalk containing glial nests. Sections of brainstem revealed extensive architectural disorganization. A developmental abnormality resulting from defective optic nerve and retina compartmentalization, accompanied by abnormalities of midline development consistent with the holoprosencephaly syndrome, was diagnosed. These lesions are consistent with signaling defects in the sonic hedgehog signaling pathway. Genetic and toxic causes of sonic hedgehog signaling defects are discussed.

Congenital isolate and total optic disc coloboma: case report and review of the literature

Isolated and total optic disc coloboma is a markedly rare congenital anomaly of the eye. Congenital eye colobomas frequently present with eye anomalies and systemic signal findings. We present a case of isolated total optic disc coloboma without systemic involvement, which has been rarely reported in the literature.

Molecular mechanisms of optic vesicle development: complexities, ambiguities and controversies

Optic vesicle formation, transformation into an optic cup and integration with neighboring tissues are essential for normal eye formation, and involve the coordinated occurrence of complex cellular and molecular events. Perhaps not surprisingly, these complex phenomena have provided fertile ground for controversial and even contradictory results and conclusions. After presenting an overview of current knowledge of optic vesicle development, we will address conceptual and methodological issues that complicate research in this field. This will be done through a review of the pertinent literature, as well as by drawing on our own experience, gathered through recent studies of both intra- and extra-cellular regulation of optic vesicle development and patterning. Finally, and without attempting to be exhaustive, we will point out some important aspects of optic vesicle development that have not yet received enough attention.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

Modified flexible iris retractor to retract superior iris and support inferior capsule in eyes with iris coloboma and inferior zonular deficiency

Flexible nylon iris retractors are a useful adjunct to cataract surgery in cases of small pupil and subluxated lenses. A modification is presented of the standard application of iris hooks to retract the superior iris and support the inferior capsule during phacoemulsification in cases of iris coloboma with inferior zonular deficiency. Three iris hooks are applied to retract the iris, and 2 iris hooks are applied to the inferior capsule margin to support the crystalline lens in that quadrant. Clear corneal temporal phacoemulsification is then performed with adequate pupillary diameter and capsular support.

Anterior coloboma with macrophthalmos and cyst

Coloboma is one of the congenital ocular malformations presenting important diagnostic and therapeutic problems, especially in infants. Coloboma can be associated with microphthalmia frequently and macrophtalmia rarely. However, the association of coloboma, macrophthalmia, and orbital cyst was not reported previously in the literature. A case of coloboma associated with macrophtalmia and cyst was presented, and MR findings of this anomaly was defined with emphasis to the importance of radiologic examinations in the diagnosis of some congenital ocular malformations.

Ocular coloboma: a reassessment in the age of molecular neuroscience

Congenital colobomata of the eye are important causes of childhood visual impairment and blindness. Ocular coloboma can be seen in isolation and in an impressive number of multisystem syndromes, where the eye phenotype is often seen in association with severe neurological or craniofacial anomalies or other systemic developmental defects. Several studies have shown that, in addition to inheritance, environmental influences may be causative factors. Through work to identify genes underlying inherited coloboma, significant inroads are being made into understanding the molecular events controlling closure of the optic fissure. In general, severity of disease can be linked to the temporal expression of the gene, but this is modified by factors such as tissue specificity of gene expression and genetic redundancy.

Ocular coloboma and high myopia with Hirschsprung disease associated with a novel ZFHX1B missense mutation and trisomy 21

Syndromic Hirschsprung disease has been associated with mutations in ZFHX1B, a Smad-interacting transcriptional repressor protein. Tissue in situ hybridization has demonstrated strong expression of ZFHX1B in the developing eye, suggesting that some mutations in this gene may cause visual loss. However, none of the reported mutations have been associated with an ocular phenotype. We describe a patient with Down syndrome and Hirschsprung disease with high myopia and ocular coloboma affecting the iris and retina. In addition to trisomy 21, a novel, de novo heterozygous A to G transition in exon 8 of the ZFHX1B gene was identified, which results in a R953G amino acid substitution. This abnormality was not seen in a screen of 200 chromosomes from ethnically matched, normal controls. The arginine residue at position 953 is an extremely conserved amino acid throughout evolution. This is the first report associating Hirschsprung disease and severe eye defects with a specific genetic mutation and is the first report of a mutation in ZFHX1B causing a developmental ocular anomaly.

Spontaneous resolution of optic nerve coloboma-associated retinal detachment

We report a congenital neurosensory retinal detachment associated with an optic nerve coloboma with subsequent spontaneous reattachment. This represents the earliest reported case of such a clinical situation. An observation period is recommended for infants with this clinical course to allow for the opportunity of spontaneous reattachment.

Ribosomal protein L24 defect in belly spot and tail (Bst), a mouse Minute

Ribosomal protein mutations, termed Minutes, have been instrumental in studying the coordination of cell and tissue growth in Drosophila. Although abundant in flies, equivalent defects in mammals are relatively unknown. Belly spot and tail (Bst) is a semidominant mouse mutation that disrupts pigmentation, somitogenesis and retinal cell fate determination. Here, we identify Bst as a deletion within the Rpl24 riboprotein gene. Bst significantly impairs Rpl24 splicing and ribosome biogenesis. Bst/+ cells have decreased rates of protein synthesis and proliferation, and are outcompeted by wild-type cells in C57BLKS<-->ROSA26 chimeras. Bacterial artificial chromosome (BAC) and cDNA transgenes correct the mutant phenotypes. Our findings establish Bst as a mouse Minute and provide the first detailed characterization of a mammalian ribosomal protein mutation.

Ocular and systemic findings associated with optic disc colobomas

PURPOSE

To determine the ocular and systemic anomalies associated with optic disc colobomas.

PATIENTS AND METHODS

The records of patients with a diagnosis of isolated optic disc coloboma and chorioretinal coloboma with optic disc involvement were retrospectively reviewed.

RESULTS

Fifteen patients were included in the study. Of the 30 eyes, the optic disc and choroid were involved in 18, an isolated disc coloboma was present in 5, a normal optic disc was present in 4, and the optic disc could not be identified because of extreme microphthalmia in 1. Of the optic discs outside the fundus colobomas, 1 had an abnormal shape and 1 had optic atrophy and hypoplasia. Eight patients had bilateral but asymmetric involvement of the optic nerve with the coloboma. Fourteen eyes of 9 patients were microphthalmic. Nine eyes of 6 patients had microcornea. One patient had a nonrhegmatogenous retinal detachment at the time of diagnosis. One eye had a retrobulbar cyst with microphthalmia. Eight (53%) of the patients had sensory strabismus. Two patients had unilateral cortical lens opacities. Associated systemic findings were present in 6 (40%) of the 15 patients.

CONCLUSIONS

Optic disc colobomas have a wide variety of presentations. Poor visual acuity was observed mostly in eyes with macular involvement and microphthalmia.

Visually impaired children with posterior ocular malformations: pre- and neonatal data and visual functions

AIM

To analyse pre- and neonatal data and ocular findings in children with visual impairment caused by posterior ocular malformations.

METHODS

Medical records were scrutinized, dried blood spot cards were analysed for virus DNA and ophthalmological assessments were performed in 28 children with optic nerve hypoplasia (ONH) and 10 with optic/chorio-retinal coloboma.

RESULTS

Prenatal exposure to possible teratogens was documented in 5/28, herpes simplex virus type 1 DNA was identified in the dried blood spot cards of 1/26 children and neonatal hypoglycaemia in 12/28 children with ONH. The time delay from ocular to endocrinological diagnosis and treatment was 3 years. Children with ONH and severe visual impairment had endocrinopathy more often (11/13) than ONH children with better visual functions (5/15). Prenatal exposure to teratogens or neonatal hypoglycaemia was not identified in any of the children with coloboma.

CONCLUSION

Neonatal hypoglycaemia was common in children with ONH. Severe visual impairment predicted endocrinopathy. Analysis of dried blood spot cards could serve as an additional diagnostic tool in children with ocular malformations.

Paramacular coloboma

BACKGROUND

Paramacular coloboma (plural: colobomata) is a solitary oval football or torpedo-shaped chorioretinal lesion located temporal to the fovea in one or both eyes. Previous case reports have speculated varying etiology, but few have justified its pathognomonic shape and location. We believe it to be congenital in nature and caused by incomplete differentiation of the arcuate bundles along the horizontal raphe in development of the macular architecture. Associated ocular findings may include blepharophimosis, situs inversus, or other anomalous retinal vascular patterns.

CASE REPORTS

Three cases of asymptomatic unilateral paramacular colobomata are presented. In each case, a single oval chorioretinal lesion temporal to the macula was found during routine examination. Visual acuity and Humphrey threshold visual field testing were normal with no other associated congenital, systemic, or ocular abnormalities. Because the lesion is nonprogressive, these patients can be followed on an annual basis.

CONCLUSION

Due to their anatomical origin, paramacular colobomata are always located temporal to the macula and have an oval football-shaped appearance. Visual acuity and visual field testing are usually normal, although highly observant patients may be aware of a mild scotoma. Differential diagnosis is important because the clinical appearance can be similar to acquired conditions, most notably age-related macular degeneration and presumed ocular histoplasmosis syndrome.

Choroidal neovascular membrane associated with optic nerve coloboma in a patient with CHARGE association

PURPOSE

To report a patient with CHARGE association (coloboma, heart disease, choanal atresia, growth retardation, genital hypoplasia, and ear abnormalities) who developed a choroidal neovascular membrane in association with an optic nerve coloboma.

DESIGN

Interventional/observational case report.

METHOD

A 21-month-old boy with CHARGE association developed a grayish choroidal neovascular membrane associated with lipid exudation, subretinal fluid, and retinal hemorrhage at the temporal edge of his right optic nerve coloboma.

RESULTS

The patient underwent transpupillary diode laser of the choroidal neovascular membrane. Five months later, it and the serous retinal detachment had resolved.

CONCLUSIONS

Patients with CHARGE association may develop choroidal neovascular membrane with serous retinal detachments in association with optic nerve colobomas. These neovascular membranes may be treated successfully with transpupillary diode laser.

Ultrasound biomicroscopy in lens "coloboma"

PURPOSE

To study the morphology of the Lens "Coloboma" using the technique of ultrasound biomicroscopy.

METHODS

We used the Paradigm 40 Ultrasound biomicroscope to study the morphology of the lens "Coloboma".

RESULTS

Ultrasound biomicroscopy of the lens "Coloboma" revealed a greatly increased sphericity of the lens and the deficiency of zonules in the "colobomatous" area.

CONCLUSIONS

Ultrasound biomicroscopy has helped in elucidating the pathology of the lens "Coloboma".

Congenital eye anomalies

Any part of the eye and its surrounding tissues may be affected by congenital malformation. Anomalies may occur in isolation, in combination, or as part of a systemic malformation syndrome. Early identification is essential to remove potential obstructions to visual development and to identify potential underlying multisystem disease. Recognition of congenital eye anomalies can also improve parental understanding and genetic counseling.

Novel mutation in sonic hedgehog in non-syndromic colobomatous microphthalmia

Ocular (uveoretinal) colobomas occur in one in 10,000 individuals and present a substantive cause of congenital poor vision. The genetic bases of most forms of uveoretinal coloboma are elusive; mutations in PAX2 are found in only a few cases of coloboma of the retina and optic nerve that occur with renal anomalies as part of the renal-coloboma syndrome (MIM#120330; #167409). From experimental data that upstream expression of sonic hedgehog (SHH) controls Pax2 expression in mice and zebrafish, and from clinical experience that colobomas are observed frequently in patients with holoprosencephaly, we hypothesized that SHH could be a candidate for non-syndromic ocular colobomas (NSOC). We identified a three-generation family in which both a proband and his mother presented with iris and uveoretinal colobomas without optic nerve involvement. A novel 24 bp deletion in the gene SHH was identified in these affected family members, and cosegregated with the phenotype. This is the first report of the association of SHH mutations and uveoretinal coloboma.

Early detection of severe cholestatic hepatopathy in COACH syndrome

COACH syndrome is a disorder with cerebellar vermis hypoplasia, oligophrenia, ataxia, coloboma, and hepatic fibrosis. Sixteen cases with certain COACH diagnosis have been reported so far. Neurologic abnormalities are the first symptoms in most cases. The majority of cases were diagnosed late in childhood or adolescence. Complications of the hepatopathy contribute extensively to the morbidity and lethality in the course of the disease. Major complications are portal hypertension, esophageal varices, and gastrointestinal bleeding. We report of a child with only mild neurologic symptoms, but severe hepatic fibrosis with cholangiopathy, and review the literature. This is the first description of profound cholestatic hepatopathy in a very young child with COACH syndrome. The patient was found to have cerebellar vermis hypoplasia, unilateral optical nerve coloboma, mild dysmorphic signs, and a ventricular septum defect. Routine laboratory investigations eventually revealed elevated liver enzymes. Prothrombin time was abnormal. Ultrasound scan of the liver was normal. Hepatotropic viral infections were excluded. We performed a liver biopsy at the age of 16 months, confirming an early stage of cirrhosis with septal fibrosis and pseudolobules, inflammatory infiltrates, signs of cholestasis, and reduced numbers of intrahepatic bile ducts. Early detection and differentiation of liver pathology are important in COACH syndrome. Progressive destructive cholangiopathy may contribute to hepatic fibrosis in COACH syndrome. Liver disease can be severe even in cases with mild neurologic deficits.

Vax2inactivation in mouse determines alteration of the eye dorsal-ventral axis, misrouting of the optic fibres and eye coloboma

Vax2 is a homeobox gene whose expression is confined to the ventral region of the prospective neural retina. Overexpression of this gene at early stages of development in Xenopus and in chicken embryos determines a ventralisation of the retina, thus suggesting its role in the molecular pathway that underlies eye development. We describe the generation and characterisation of a mouse with a targeted null mutation of the Vax2 gene. Vax2 homozygous mutant mice display incomplete closure of the optic fissure that leads to eye coloboma. This phenotype is not fully penetrant, suggesting that additional factors contribute to its generation. Vax2 inactivation determines dorsalisation of the expression of mid-late (Ephb2 and Efnb2) but not early (Pax2 and Tbx5) markers of dorsal-ventral polarity in the developing retina. Finally, Vax2 mutant mice exhibit abnormal projections of ventral retinal ganglion cells. In particular, we observed the almost complete absence of ipsilaterally projecting retinal ganglion cells axons in the optic chiasm and alteration of the retinocollicular projections. All these findings indicate that Vax2 is required for the proper closure of the optic fissure, for the establishment of a physiological asymmetry on the dorsal-ventral axis of the eye and for the formation of appropriate retinocollicular connections.

Molecular characterization and mapping of ATOH7, a human atonal homolog with a predicted role in retinal ganglion cell development

The human ATOH7 gene encodes a basic helix-loop-helix (bHLH) transcription factor that is highly similar to Drosophila Atonal within the conserved bHLH domain. The ATOH7 coding region is contained within a single exon. We mapped ATOH7 to Chromosome (Chr) 10q21.3-22.1, a region syntenic to the segment of mouse Chr 10 where Atoh7 (formerly Math5) is located. The evolutionary relationship between ATOH7 and other atonal homologs was investigated using parsimony analysis. A direct comparison of ATH5/7 and ATH1 protein subgroups to Atonal also revealed a nonrandom distribution of amino acid changes across the bHLH domain, which may be related to their separate visual and proprioceptive sensory functions. Among bHLH genes, ATOH7 is most closely related to Atoh7. This sequence conservation extends significantly beyond the coding region. We define blocks of strong homology in flanking human and mouse genomic DNA, which are likely to include cis regulatory elements. Because targeted deletion of Atoh7 causes optic nerve agenesis in mice, we propose ATOH7 as a candidate for human optic nerve aplasia and related clinical syndromes.