Expanded Understanding of Retinal Abnormalities Overlying Choroidal Neovascularization Noted in Minimum Intensity Projection Images (MinIP) from CirrusTM SD-OCT in Patients with Age-related Macular Degeneration

Abstract

 

Purpose:

 

To describe our expanded understanding of retinal abnormalities overlying choroidal neovascularization (CNV) noted in minimum intensity projection (MinIP) images from Cirrus^TM (Carl Zeiss Meditec, Dublin, CA) spectral domain optical coherence tomography (SD-OCT) of patients with age-related macular degeneration (AMD), including evaluation of the inter-observer agreement on the shape and extent of the bright signal noted in MinIP images, and its origin from B-scans.

 

Methods:

 

Following IRB approval, 25 eyes from 23 patients were imaged with Macular Cube 512x218 scans on two separate visits. Included were 4 eyes with new-onset CNV secondary to AMD, 16 eyes with CNV during anti-VEGF therapy, and 5 eyes with geographic atrophy of the retinal pigment epithelium due to AMD but no CNV. Lesions noted on the MinIP images at each visit were manually segmented independently by two graders. The shape and extent of the segmented area were qualitatively compared. Origin of the minimum intensity signal was determined for all scans, and reviewed qualitatively.

 

Results:

 

The inter-grader variability showed good agreement in 15 of 20 study eyes. Qualitative review of the origin of the MinIP signal showed that the gray background intensity corresponding with normal retinal areas typically consisted of reflectivity values from the outer nuclear layer (ONL). This finding was consistent in all study eyes as well as in all control eyes. In the presence of CNV, the ONL often became hyper-reflective, causing a bright lesion with indistinct borders to appear in the MinIP image. In other cases, the ONL became sufficiently hyper-reflective or thinned such that the MinIP signal was in the inner nuclear layer. In these cases, a brighter lesion with well delineated borders typically was seen in the MinIP image.

 

Conclusions:

 

MinIP images provide an en face view of abnormalities in the reflectivity and integrity of the ONL. Qualitative correlation of images of CNV as seen in fluorescein angiography with bright areas in MinIP images indicates that CNV is associated with observable alterations to retinal layers, particularly in the ONL.

 

Keywords: imaging/image analysis: clinical • age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)