Bilateral Macular Coloboma With Eccentric Fixation Confirmed by Microperimetry: A Case Report

The purpose of this report is to describe a case of bilateral macular coloboma with eccentric fixation confirmed by microperimetry. A 21-year-old Vietnamese woman presented with bilateral vision loss and was diagnosed with bilateral macular coloboma. Comprehensive ophthalmic examinations, including visual acuity testing, fundus examination, dynamic visual field testing, and microperimetry (MP-3, Nidek Co., Ltd., Gamagori, Japan), were performed to evaluate the macular lesions and fixation patterns. Blood tests were also conducted to investigate potential etiologies. Visual acuity was found to be 20/100 in the right eye and 20/80 in the left eye, with exotropia but no nystagmus. Fundus examination revealed bilateral, round, well-defined depressions approximately four and three disc diameters in size in the macular areas, with choroidal atrophy, pigmentation, and linearization of retinal vessels. Dynamic visual field testing demonstrated paracentric dark spots corresponding to the lesions. Microperimetry showed unstable fixation located on the nasal side of the macular lesions in both eyes, with decreased retinal sensitivity in the affected areas. Blood tests were positive for cytomegalovirus immunoglobulin G (IgG). This case presented a diagnostic challenge in distinguishing between developmental abnormality and inflammatory scarring due to a possible in utero infection. Microperimetry demonstrated eccentric fixation on the nasal side of the macular lesions, suggesting the patient likely established this fixation pattern from childhood, despite the unknown time of onset. This case highlights the value of microperimetry in evaluating fixation patterns in patients with bilateral macular coloboma.