Spectral Domain Optical Coherence Tomography Findings of Retinal Macroaneurysm

Introduction

Spectral domain optical coherence tomography (SD OCT) has been recently introduced for clinical use. This system allows a faster acquisition time than the conventional time domain OCT, thus allowing for a larger number of images to be acquired (over 20,000 axial scans per second). This increased speed and density of A-scans within B-scans result in higher-resolution OCT scans (5 to 6 μ).¹ Both spectral domain and time domain OCT systems use superluminescent diode light sources, but those in the spectral domain systems have a slightly broader bandwidth, also improving axial resolution over the time domain. We present SD OCT findings in a patient with retinal macroaneurysm.

Case Report

A 47-year-old healthy male presented with complaint of dry eyes. He denied any past medical history and was taking no medications. On examination his best-corrected visual acuity was 20/20 in both eyes OU. The ocular motility was full, and pupils were normal. Confrontation visual fields and intraocular pressures were normal bilaterally. An anterior segment examination was normal in both eyes. A dilated fundus examination of the left eye was normal. The fundus examination of the right eye was normal except for a possible macroaneurysm involving the supero-temporal arcade approximately 1DD away from the optic disc (Fig. 1). There was an area of possible internal hemorrhage inferiorly but no signs of rupture. Fundus fluorescein angiography (FA) OD revealed a small area of pooling at the macroanuerysm with blocking of fluorescence from the hemorrhage inferiorly. There were no signs consistent with rupture of the macroaneurysm (Fig. 1). The Left eye FA was normal. SD OCT (OCT/SLO, OTI Ophthalmic Technologies, Ontario, Canada), through the area of macroaneurysm, demonstrated a large 215-μ lumen length and 308-μ area with inferior hyper-reflectivity at the area of the hemorrhage (Figs. 1–3, selected line scans from the acquired Horizontal B Scan images). There was focal thickening of the retina surrounding the macroaneurysm but no retinal edema.

Figure 1. (A) Fundus Photograph Showing the Maroaneurysm (arrow) with Minimal Blood Inferiorly. (B) Fundus Fluorescein Angiography FA (laminar Flow Phase) Revealing Early Filling of the Macroaneurysm with Area of Block Fluorescein by the Blood. (C) FA Later Phase Complete Filling of the Macroaneurysm with Dye (hyperfluorescence) Without Leakage. There Is a Persistent Area of Blocked Fluorescence from the Blood. (D) Spectral Domain OCT—Horizontal Line Scan (single Image Selected from the Horizontal B Scan, Scan Angle 29.2°—Axial Resolution, 6 μ) Through the Area of Macroaneurysm Revealing the Lumen Measuring 215 μ in Antero-Posterior Diameter Using the “length Tools” of the Software. There Is an Area of Hyperreflectivity in the Inferior Wall/Lumen, Which Corresponds to the Area of Blood Visible on Fundus Examination and FA. This Area Could Be Either Hemorrhage in the Wall or Thrombus in the Lumen. (E) Spectral Domain OCT—Horizontal Line Scan (image Selected from the Horizontal B Scan, Scan Angle 29.2°—Axial Resolution, 6 μ) Through the Area of the Macroaneurysm, the Wall Does not Demonstrate Hyperreflectivity (lack of thrombus/hemorrhage).

Figure 3. Spectral Domain OCT Horizontal Line Scan (single Image Selected from the Horizontal B Scan, Scan Angle 29.2°—Axial Resolution, 6 μ) Through the Area of Macroaneurysm Revealing the Lumen Area of 308 μ Using the “area Tools” of the Software as Demonstrated in the Figure.

Discussion

Retinal macroaneurysms are acquired dilations of the large arterioles of the retina frequently associated with hypertension. They usually arise within the first three orders of the arterial bifurcation. Arbitrarily, the diameter of a macroaneurysm exceeds 100 μ and are usually less than 250 μ.² Frequently, macroaneuryms spontaneously resolve without treatment. Rupture of a macroaneurysm causes retinal hemorrhages in multiple layers, which may result in visual loss.³ Early diagnosis and management of an impending rupture would be beneficial. Various signs of impending rupture have been proposed in the literature, but none have been proven.⁴ In vivo measurement of the macroaneurysm and allowing various internal characteristics would be beneficial.

Presently, the modality to visualize a macroaneurysm is fundus examination and FA. OCT is increasingly used in various retinal disorders due to its ease of use, non-invasive rapid image acquisition and high-resolution imaging capabilities. Stratus OCT findings of a case of macroaneurysm have been suggested as an area of hyper-reflectivity in the retina.⁵ However, the actual aneurysm was not visible in the report, either due to the lower-resolution scans or surrounding hemorrhage. To the best of our knowledge, we report the first case of SD OCT findings of a macroaneurysm. The higher-resolution SD OCT more accurately measures the size (length and area) of the macroaneurysm and provides more detailed imaging of important prognostic characteristics including hemorrhage or thrombus. SD OCT may provide early identification of macroaneurysms and afford an opportunity for earlier intervention in high-risk cases. The high-risk SD OCT characteristics may be of a larger size and hemorrhage in the wall (represented by hyperreflectivity).

SD OCT allows high resolution imaging and measurement of retinal macroaneurysms. Larger studies are required to determine the value of SD OCT in their diagnosis and management.