Pathognomonic macular ripples in fovea plana are revealed by polarized infrared reflectance imaging

Abstract

Purpose : A pathognomonic macular ripple sign has been observed in infrared (IR) scanning laser ophthalmoscopy (SLO) images in individuals with fovea plana, but is only evident in images captured by the Heidelberg Retina Angiograph 2 (HRA2, Heidelberg Engineering). The basis of this sign is presently unclear and is the purpose of this study. We tested the hypothesis that the macular ripple sign is an artefactual interference pattern that can be elicited via the application of a polarization filter to scanning laser fundus imaging.

Methods : Patients with fovea plana and healthy control subjects underwent ocular motility assessment, IR SLO imaging, IR SLO imaging with a polarization filter, and spectral-domain optical coherence tomography (SD-OCT).
All IR fundus images were acquired using the Spectralis HRA+OCT (Heidelberg Engineering Inc, Heidelberg, Germany). A 55° objective lens was used for IR imaging. SD-OCT was also acquired using the Spectralis with a 30° lens. The Spectralis model used in this study features a linear polarization filter that can be added to the incoming path of light by changing the instrument’s filter lever position (Figure 1). The outcome measure of this study is the qualitative observation (or absence) of the macular ripple sign in IR fundus images.

Results : IR images of each eye in the absence of the polarization filter were unremarkable for visible abnormalities (Figure 2, A and B). Fundus IR images taken with the polarization filter reveals artefacts in unaffected and affected patients. The macular bowtie reflex is visible in the healthy control eyes (Figure 2, C), while macular ripples are observed in patients with fovea plana (Figure 2, D).

Conclusions : The observation of macular ripples in patients with fovea plana is dependent on the use of a polarization filter in IR imaging. Imaging instruments with these features are commercially available and can be utilized to readily identify the pathognomonic ripple sign without the use of SD-OCT, especially for cases in which SD-OCT acquisition is not possible due to patient age, cooperation, or nystagmus.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Heidelberg Spectralis HRA+OCT filter lever includes a polarization filter when in the “P” position.

 

Figure 2. (A) IR image without polarization filter of the healthy eye. (B) IR without polarization filter in fovea plana. (C) IR with polarization filter in the healthy eye. (D) IR with polarization filter in fovea plana.