Ophthalmic Surgery, Lasers and Imaging Retina

Clinical Science 

Omega Sign: A Distinct Optical Coherence Tomography Finding in Macular Combined Hamartoma of Retina and Retinal Pigment Epithelium

Vinod Kumar, MS, DNB, MNAMS, FRCS; Rohan Chawla, MD; Koushik Tripathy, MD

Abstract

BACKGROUND AND OBJECTIVE:

To report a distinct optical coherence tomography (OCT) appearance of macular combined hamartoma of retina and retinal pigment epithelium (CHRRPE).

PATIENTS AND METHODS:

This is a retrospective case series of four eyes of four patients with macular CHRRPE who were assessed with the help of color fundus photographs, swept-source OCT (SS-OCT), and fundus fluorescein angiography wherever required.

RESULTS:

All four patients presented with decreased visual acuity. SS-OCT in all patients showed adherent epiretinal membrane (ERM) and localized thickening of underlying retina. An omega-shaped disorganization of inner retinal layers was seen bounded posteriorly by the outer plexiform layer. This was termed, “Omega sign.”

CONCLUSION:

Omega sign is a characteristic feature of macular CHRRPE and may help to distinguish macular CHRRPEs from ERMs.

[Ophthalmic Surg Lasers Imaging Retina. 2017;48:122–125.]

Abstract

BACKGROUND AND OBJECTIVE:

To report a distinct optical coherence tomography (OCT) appearance of macular combined hamartoma of retina and retinal pigment epithelium (CHRRPE).

PATIENTS AND METHODS:

This is a retrospective case series of four eyes of four patients with macular CHRRPE who were assessed with the help of color fundus photographs, swept-source OCT (SS-OCT), and fundus fluorescein angiography wherever required.

RESULTS:

All four patients presented with decreased visual acuity. SS-OCT in all patients showed adherent epiretinal membrane (ERM) and localized thickening of underlying retina. An omega-shaped disorganization of inner retinal layers was seen bounded posteriorly by the outer plexiform layer. This was termed, “Omega sign.”

CONCLUSION:

Omega sign is a characteristic feature of macular CHRRPE and may help to distinguish macular CHRRPEs from ERMs.

[Ophthalmic Surg Lasers Imaging Retina. 2017;48:122–125.]

Introduction

Combined hamartomas of retina and retinal pigment epithelium (CHRRPE) are solitary, unilateral, benign tumors that are located at the posterior pole and may be associated with vision loss. CHRRPE lesions have varying amounts of glial, vascular, and retinal pigment epithelial components.1 Gass divided them in to two subcategories, depending on the optic nerve involvement.2 The lesions, which do not involve the optic nerve, are frequently present in the macular area. The most common differential diagnosis for macular CHRRPE lesions is epiretinal membrane (ERM).3 Similar to CHRRPE, ERMs are associated with retinal surface gliosis with retinal vascular tortuosity. Thus, it becomes challenging to differentiate childhood ERMs from CHRRPE lesions, since fluorescein angiograms do not assess the intraretinal component of CHRRPE.3

High-resolution optical coherence tomography (OCT) has been found to be useful for differentiating these lesions.4 We have identified a distinctive OCT finding that may help to distinguish a CHRRPE lesion from an ERM. We describe four eyes with macular CHRRPE in which OCT revealed omega-shaped infiltration of the inner retina lined posteriorly by the outer plexiform layer.

Patients and Methods

This was a retrospective observational case series. Four eyes of four patients with macular CHRRPE were included in the study. All patients had undergone detailed ophthalmological examination, including best-corrected visual acuity (BCVA) (Snellen's chart), slit-lamp biomicroscopy, color fundus photography, and high-resolution OCT. Fundus fluorescein angiography (FFA) was conducted wherever required if either of the components of CHRRPE was not evident, or to rule out other pathology like choroidal neovascularization. The CHRRPE was diagnosed based on the clinical presence of epiretinal glial tissue, vascular tortuosity, and retinal pigment epithelium (RPE) hyperpigmentation. The patients with history/signs of trauma and intraocular inflammation were not included in the study. Informed consent was obtained from all the patients, and the study adhered to the tenets of the Declaration of Helsinki.

Results

Four eyes of four patients with macular CHRRPE were identified. One patient was male and three were female (mean age: 18 years; range: 11 years to 23 years). The right eye was affected in two patients and the left eye was affected in the other two. All the patients presented with decreased visual acuity in the affected eye. All three components of CHRRPE — namely, epiretinal glial tissue with intraretinal extension, vascular tortuosity, and hyperpigmentation of RPE — could be identified in all patients. The intraretinal extension of epiretinal glial tissue was seen as omega-shaped, hyperreflective tissue that caused disorganization of retinal layers and was limited posteriorly by the outer plexiform layer (OPL). We termed this OCT finding as “Omega sign.” Details of two cases and color fundus and OCT images of other patients are presented below.

Case 1

A 22-year-old female presented with decreased vision in her right eye noted recently. She had no systemic complaints; family history was unremarkable. Best-corrected visual acuity (BCVA) was 20/400 and 20/20 in the right and left eyes, respectively. Anterior segment examination of both eyes was unremarkable. Dilated fundus examination of both the eyes revealed reticular pseudodrusen scattered throughout the posterior pole but more prominently in the temporal macula (Figures 1A and 1B). In addition, the right eye showed thick, whitish ERM extending from the surface of disc to the fovea. This was associated with RPE hyperpigmentation appreciable more at the superior border of epiretinal glial tissue at the fovea. FFA confirmed the diagnosis of drusen (Figures 1C and 1D) and revealed vascular tortuosity. Swept-source OCT (SS-OCT) (Topcon, Tokyo, Japan) revealed findings consistent with reticular pseudodrusen (Figures 1E and 1F). A thick ERM, which was adherent throughout its length, was noted in the right eye. The retinal layers beneath the ERM were disorganized. The posterior border of this intraretinal disorganization was omega-shaped and lined by the OPL (Figures 1E and 1F; Omega sign is marked by blue line in 1E). Based on clinical findings, the patient was diagnosed to have reticular pseudodrusen in both eyes and macular CHRRPE in the right eye. The patient was given option of surgical removal of epiretinal glial tissue; however, the patient declined any intervention.


Color fundus photographs of right (A) and left eyes (B) show reticular pseudodrusen in the temporal macula. Additionally, the right eye shows epiretinal membrane (ERM) extending from the optic disc to the macula. White arrows marked “e” and “f” show the position of optical coherence tomography (OCT) scans in (E) and (F). Fluorescein angiograms show drusen in both eyes (C, D) and vascular tortuosity beneath the ERM in the right eye. Swept-source OCT (E) shows ERM, drusen, and omega-shaped localized thickening of the retina that is bounded posteriorly by the outer plexiform layer (Omega sign is marked by blue line). Omega sign is more prominent in the oblique scan (F).

Figure 1.

Color fundus photographs of right (A) and left eyes (B) show reticular pseudodrusen in the temporal macula. Additionally, the right eye shows epiretinal membrane (ERM) extending from the optic disc to the macula. White arrows marked “e” and “f” show the position of optical coherence tomography (OCT) scans in (E) and (F). Fluorescein angiograms show drusen in both eyes (C, D) and vascular tortuosity beneath the ERM in the right eye. Swept-source OCT (E) shows ERM, drusen, and omega-shaped localized thickening of the retina that is bounded posteriorly by the outer plexiform layer (Omega sign is marked by blue line). Omega sign is more prominent in the oblique scan (F).

Case 2

An 11-year-old female presented with complaints of low vision in her left eye. BCVA was 20/20 and 20/60 in the right and the left eyes, respectively. The right eye was normal, and the left eye showed a typical macular CHRRPE (Figure 2A). SS-OCT, in addition to ERM, showed omega-shaped disorganization of inner retinal layers lined posteriorly by OPL (Figure 2B). The patient was diagnosed with macular CHHRPE and was advised to undergo observation in view of relatively good visual acuity.


Fundus picture of Patient 2 with typical macular combined hamartoma of retina and retinal pigment epithelium. Swept-source optical coherence tomography shows omega-shaped disorganization of inner retina.

Figure 2.

Fundus picture of Patient 2 with typical macular combined hamartoma of retina and retinal pigment epithelium. Swept-source optical coherence tomography shows omega-shaped disorganization of inner retina.

Similar OCT findings were seen in another two patients with macular CHRRPE (Figure 3).


Color photographs of Patients 3 (A) and 4 (C) showing typical combined hamartoma of retina and retinal pigment epithelium lesion. Swept-source optical coherence tomography scans through the fovea of Patients 3 (B) and 4 (D) show Omega sign.

Figure 3.

Color photographs of Patients 3 (A) and 4 (C) showing typical combined hamartoma of retina and retinal pigment epithelium lesion. Swept-source optical coherence tomography scans through the fovea of Patients 3 (B) and 4 (D) show Omega sign.

Discussion

CHRRPEs are rare, benign tumors and are considered to be of congenital origin. Depending on the macular involvement, they may be associated with variable amount of visual loss. Visual loss has also been attributed to functional amblyopia in these patients resulting from structural abnormalities.5 The vision loss tends to be progressive, especially for those in whom the macula is involved.1,6 The macular CHRRPEs that show progressive vision loss often have predominance of epiretinal glial tissue and vitreous traction.7 These patients are often amenable to surgical removal of epiretinal glial tissue. OCT is an important tool in the assessment of such patients in deciding the plane of the dissection. Although initial results of vitrectomy and membrane removal were not encouraging,1,8 later studies showed improved outcomes following surgical management of CHRRPE.9,10 The results of surgery, however, remain guarded to that compared with conventional ERM surgery and is thus recommended only in selected patients.

During surgery for CHRRPE, in certain areas on the surface of the mass, the ERM component is adhered firmly to the retina. Forced peeling may cause complications such as bleeding and retinal holes and is not recommended in such areas. This is because epiretinal components and underlying ham-artoma are integral.9 The aim of surgery is not to remove the hamartoma, but to reduce vitreoretinal traction and surface irregularity as safely possible. Thus, it becomes prudent to differentiate macular CHRRPEs from ERM, which in young patients is often a result of trauma or uveitis. We found Omega sign helpful in the differentiation of macular CHRRPE from ERM.11 We could not find similar intraretinal findings on OCT in our database of approximately 200 ERM patients. It is our contention that Omega sign is a result of two things: outward push (perpendicular to the retina) of the OPL by the retinal hamartoma in the inner retinal layers, and inward contraction (along the retinal surface) by the epiretinal glial tissue. The small number of study eyes is the major limitation of this study. However, CHHRPE is a relatively rare condition.

To conclude, we describe an OCT finding that can be used to differentiate rarely occurring CHRRPE from commonly seen ERM, the latter being a close and common differential diagnosis of the former.

References

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Authors

From the Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.

The authors report no relevant financial disclosures.

Address correspondence to Vinod Kumar, MS, DNB, MNAMS, FRCS, 57 Sadar Apartments, Mayur Vihar phase 1 extension, New Delhi, India 110091; email: drvinod_agg@yahoo.com.

Received: August 06, 2016
Accepted: November 29, 2016

10.3928/23258160-20170130-05

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