Case of the Month

Edited by Robert N. Johnson, MD

Oct, 2016

A 51 year-old woman presents with mildly decreased vision in the left eye.

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Presented by Ananda Kalevar, MD

Figure 1: Slit lamp color photograph of the right eye.  Note the iris coloboma and advanced cataract.

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Figures 2A and B:  Color fundus montage photograph of the right eye (Figure 2A) and left eye (Figure 2B). Imaging of the right eye is suboptimal due to the significant cataract.Note the extensive choroidal coloboma involving the macula and optic nerve. In the left eye, note the large inferior choroidal coloboma with a smaller second coloboma proximally resembling a second optic disc.

Case History

A 51 year-old woman presents with mildly decreased vision in the left eye for the past several weeks.  She had poor vision in her right eye for as long as she could remember. Her past medical history was relevant for platybasia (flattening of the skull base), cervical spinal stenosis, scoliosis, and degenerative arthritis of multiple joints.  Her past ocular history, family history, social history and medications were non-contributory.

On examination, best-corrected visual acuity was counting fingers and 20/32 in her right and left eye, respectively.  Intraocular pressure was normal in both eyes.  Anterior segment of the right eye revealed an inferonasal iris coloboma with an advanced cataract (Figure 1).  Anterior segment of the left eye revealed only a mild cataract.  Posterior segment of the right eye revealed an extensive inferior chorioretinal coloboma involving the macula and the optic nerve (Figure 2A).  Posterior segment of the left eye revealed a large inferior chorioretinal coloboma. A smaller coloboma more proximal to the nerve simulated a second optic disc. There was no involvement of the macula and the optic nerve (figure 2B).  B-scan ultrasonography of the right (figure 3A) and left eye (figure 3B) revealed well circumscribed excavated areas corresponding to the colobomas.

 

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Figures 3A and B: B-scan of the right and left eyes.  Note the large excavation in each eye due to the choroidal coloboma.

What is your Diagnosis?

Differential Diagnosis

Retinoblastoma, Coats disease, morning glory syndrome, myelinated nerve fiber layer, amelanotic melanoma, retinitis, staphyloma, toxoplamosis chorioretinal scar, commotio retinae.

 

Discussion

 Uveal colobomas arise from abnormal development of the eye due to an incomplete closure of the optic fissure during the 5th-7th weeks of fetal life.1  Colobomas may impact several parts of the eye from the iris, ciliary body, choroid, retina and optic nerve.  The typical location is inferonasal.  The eyes are affected bilaterally in the majority of the cases.1 A spectrum of involvement exists for each eye and involvement can be discontinuous within the same eye.2  Vision ranges from normal to no light perception depending on involvement of optic nerve and macula.  Males and females are affected equally.  Ocular abnormalities are frequently associated with colobomas such as cataract, microphthalmia and anophthalmia.  The majority of cases have a myopic refraction.1-3

Most cases are sporadic, though autosomal dominant, autosomal recessive and X-linked recessive inheritance patterns have all been reported.  There is significant genetic complexity for colobomas thus it should be determined if the case is sporadic, familial or associated with a systemic disorder.  The presence of a coloboma should prompt a thorough evaluation to determine if there is an associated systemic disease.  The most common syndrome associated is CHARGE syndrome.1  No single environmental factor has been recognized to cause colobomas.

The chorioretinal coloboma defects are well circumscribed and typically forms a staphyloma.  The appearance of the coloboma has a white color due to the lack of choroid, retina and retinal pigment epithelium and almost bare sclera showing through with only a transparent intercalary membrane derived from undifferentiated neurosensory retina covering it.1-2  Due to the combination of these structural abnormalities, there is a high rate of retinal detachment, approaching 40%. Retinal detachment associated with colobomas are difficult to manage.4  Due to the high rates of developing a retinal detachment, prophylactic laser photocoagulation has been advocated and been shown to significantly reduce the chances of developing one.1

Take Home Points

  • Uveal colobomas arise from abnormal development of the eye due to an incomplete closure of the optic fissure.
  • No clear genetic or environmental mechanism has been understood.
  • High rates of retinal detachment are associated with uveal colobomas.

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References

  1. Uhumwangho OM, Jalali S. Chorioretinal coloboma in a paediatric population. Eye (London, England). 2014 Jun;28(6):728-33.
  2. Chang L, Blain D, Bertuzzi S, Brooks BP. Uveal coloboma: clinical and basic science update. Current opinion in ophthalmology. 2006 Oct 1;17(5):447-70.
  3. Warburg M. Classification of microphthalmos and coloboma. Journal of medical genetics. 1993 Aug 1;30(8):664-9.
  4. McDonald HR, Lewis H, Brown G, Sipperley JO. Vitreous surgery for retinal detachment associated with choroidal coloboma. Archives of Ophthalmology. 1991 Oct 1;109(10):1399-402.

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