Ocular coloboma (OC) is a rare congenital anomaly began by defective embryogenesis. As the development of the eye starts in the twenty-two day embryo, as the appearance of a pair of shallow grooves on each side of the invaginating forebrain (1). Ocular coloboma is the product of an error in the fetal fissure closure that ends with persistent cleft, normally occurring between the fifth and sixth weeks of gestation (2). Colobomas are generally accompanying with visual loss that could need some treatment and intervention other than amblyopia management (3).
In this article, we present a case of bilateral iris, disc & retina coloboma.
A 20-year-old man referred from a far village to Ophthalmology clinic, King Khaled Hospital with painless and progressive decreased vision in the right eye for 2 months.
The decrease of vision in the right eye was gradual without pain and history of ocular trauma or surgeries, his left eye is amblyopic. He is medically free as well as the family history. Neonatal history revealed that his mother was exposed to x-ray in 1st trimester.
On ocular examination, his unaided distance visual acuity was 20/200 in the right eye & hand motion in the left eye. His intraocular pressure (IOP) was 18 mm Hg bilaterally OU. On inception there was exotropia of the left eye. Undilated anterior segment evaluation on slit lamp was within normal limits except of iris coloboma in the inferonesal quadrant OU (Fig.1).
Dilated fundus examination shown optic disc and retinochoroidal colobma OU (Fig.2) with juxtapapillary choroidal neovascularization in the right eye. Further more we did optical coherence tomography (OCT) which confirm presence of choroidal neovascular membrane (CNVM) (Fig.3)
OC is a rare congenital anomaly that has a prevalence of around 0.14% in the general population (4) it is initiated by imperfect embryogenesis, which leads to failed closure of the embryonic fissure during the second month of fetal life. (5).
The incidence of this syndrome is 0.7 per 10 000 live-births worldwide (1). In our case we have a patient with bilateral iris, optic disc, retinochoroidal coloboma. No records exist on the incidence in Saudi Arabia.
Sporadic, unilateral or bilateral coloboma causes are varies from genetic and non-genetic factors, also could be related to some syndromes as CHARGE syndrome (6). Using of thalidomide and alcohol abuse and other certain drugs during pregnancy are believed to be linked with OC as some studies suggest (7)(8).
Many reasons are believed to be the cause of colobomas, so here we described a case of OC associated with retinal, choroidal, iris coloboma. We believe that it’s unlikely to be of autosomal dominant inheritance. Because neither one of the parents or siblings of our patient had the same condition. And it is less frequently an autosomal dominant inheritance may occur (9). Chromosomal analysis it is needed to be done with patient of OC but it was not possible in our case due to non-availability of our facilities, although we think may be neonatal exposure of x-ray could be the cause as the history given.
Our patient presents with bilateral iris, disc and retinochoroidal coloboma and this is consistent with previous study that counts Fifty percent of patients with OC have bilateral disease (10). He also had right choroidal neovascularization inferiornasal that cause the decreased of vision in such cases the treatment plan will include either anti-vascular endothelial growth factor (anti-VEGF), focal laser photocoagulation, or photodynamic therapy according to literature usually it is prefer to start with focal laser photocoagulation (11) but regarding our patient who have the CVNM in juxtapapillary area we decide to treat him with anti- VEGF to avoid potentially risk of iatrogenic vision loss. Anti- VEGF resulted in regression of the CNVM and improvement of visual acuity. Furthermore we are planning to continue with the patient for more anti –VEGF until reaching complete regression of the CVNM and routine follow up in the future.
To our knowledge the reported cases of coloboma in Saudi Arabia mainly because of gentic factors, this is the first case of coloboma reported in northern region in Saudi Arabia also the first case to believe that the causative factor is due to environmental factor, which is neonatal exposure to x-ray. We recommend lifelong follow up for coloboma cases to catch any retinochoroidal changes of developing of cataract and glaucoma.