A rare case of unilateral Axenfeld-Rieger anomaly associated with optic disc coloboma: A multimodal imaging canvas.

Abstract

A 22-year-old male presented to the outpatient department (OPD) with the complaint of photophobia. His best-corrected visual acuity (BCVA) was 20/20 in the right eye (oculus dextrus) and 20/40 in the left eye (oculus sinister). On ocular examination, OD was normal and OS revealed posterior embryotoxon with mild corectopia [Fig. 1a]. Ultrasound biomicroscopy [Fig. 2a], gonioscopy [Fig. 2b], and anterior segment optical coherence tomography (AS-OCT) [Fig. 1b] revealed thick bands of iris tissue adherent to the posterior embryotoxon. His intraocular pressures (IOPs) were 18 mmHg OD and 25 mmHg OS. Fundus examination [Fig. 3], B-scan [Fig. 4a and b], and optical coherence tomography (OCT) [Fig. 4c and d] of optic nerve head revealed optic disc coloboma, with visual fields showing the corresponding enlargement of blind spot [Fig. 5a]. Specular microscopy revealed polymegathism and decreased cell density in OS [Fig. 5b]. Craniofacial dysmorphism, dental anomalies, excess umbilical skin, and cardiac abnormalities were ruled out.Figure 1: (a) Slit-lamp image showing posterior embryotoxon, (i.e.)thickened prominent anteriorly displaced Schwalbe’s line (red arrow) extending from 3 o’clock to 7 o’clock position and corectopia in the left eye (OS). (b) Anterior segment optical coherence tomography (AS-OCT) revealing the iris strands adherent (red arrow) to posterior embryotoxon in OSFigure 2: (a and b) Ultrasound biomicroscopy image and gonioscopic image revealing iris strands adherent (red arrows) with the posterior embryotoxon in OSFigure 3: Fundus photograph showing (a) normal study in OD and (b) optic nerve head coloboma with peripapillary atrophy in OS. Same fundus in zoomed view showing (c) the normal optic disc in OD and (d) colobomatous optic disc with peripapillary atrophy in OSFigure 4: (a) B-scan examination of OS showing a mild posterior excavation of the optic nerve head (red arrow) suggestive of an optic disc coloboma. (b) Zoomed image of the same. (c and d) Optical coherence tomography (OCT) optic nerve head of OS showing poorly differentiated retinal tissue with multiple schitic cavities (red asterisks) suggesting an optic nerve head coloboma and herniated retina adjacent to the colobomatous areaFigure 5: (a) Perimetry report showing functional enlargement of blind spot corresponding to the structural optic nerve head coloboma in OS. (b) Specular microscopy showing normal endothelial cell morphology and cell density (2933 cells/mm2) in OD and decreased cell density (2571 cells/mm2) (red circle) and increased polymegathism in OSDiscussion Neural crest-derived mesenchymal cells, neuroectoderm of the optic cup, and surface ectoderm, all contribute to development of the tissues of anterior segment. Axenfeld–Rieger anomaly (ARA) is an iridocorneal anomaly which is congenital, bilateral, and may include ocular features such as limbal dermoid, megalocornea, microcornea, cataracts, chorioretinal colobomas, macular degeneration, and optic nerve hypoplasia.[123] But in this case, ARA was unilateral and associated with optic disc coloboma. Increased IOP is a common association of ARA, and was seen in this case, which was managed with anti-glaucoma medications. Though the angles were predominantly open, glaucoma occurs in approximately 50% of patients during childhood or adulthood due to incomplete development of the trabecular meshwork during gestation.[456] Testing for PITX2 and FOXC1 genes was carried out and mutation in FOXC1 was documented. Though rare, this manuscript reports a unilateral presentation of ARA associated with glaucoma, optic disc coloboma, and mutation in FOXC1 gene, which, according to our knowledge has never been reported in the literature before. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.