The diagnostic accuracy of spectral-domain optical coherence tomography for neovascular age-related macular degeneration: a comparison with fundus fluorescein angiography

Abstract

Purpose: To evaluate the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) for neovascular age-related macular degeneration (nAMD): a comparison against fundus fluorescein angiography (FFA).

Methods: A retrospective review of SD-OCT, colour fundus photographs (FP), and FFA of 411 consecutive patients referred to a rapid access Macular Clinic over a 4-year period was performed. FFA images were reviewed non-stereoscopically. SD-OCT images were acquired using the Topcon 3D OCT-1000 instrument. All FFA and OCT images were graded by at least two ophthalmologists independently. Side-by-side grading took place with immediate open discussion and adjudication. If there was disagreement between the two grading ophthalmologists or they were not 90% confident of their assigned grade, then adjudication by a third ophthalmologist was performed.

Results: A total of 278 eyes were graded as having choroidal neovascularisation (CNV) with SD-OCT and 231 diagnosed with FFA. The main diagnostic CNV classifications on FFA were: classic no occult in 27 eyes, predominantly classic in 16, minimally classic in 50, occult in 129, and 9 peripapillary membranes. There were a total of 47 false positives with SD-OCT: a rate of 16.9%. The sensitivity and specificity of SD-OCT alone for detecting CNV was 100 and 80.8%, respectively.

Conclusion: Our study confirms SD-OCT in comparison to the reference standard of non-stereoscopic FFA is highly sensitive at detecting newly presenting nAMD in the setting of a specialist AMD clinic where the investigations are interpreted by trained specialists. However, it does not seem accurate enough to replace FFA in the diagnosis on nAMD in current practice.

Figure 1

A fusiform or dome shaped area of high reflectivity located within the subretinal space directly adjacent to the presumed retinal pigment epithelium (RPE). This may or may not be associated with sub-retinal fluid (SRF), intra-retinal fluid (IRF), or haemorrhage. Subretinal haemorrhage was ruled out as the cause of this lesion by using point to point correlation between the SD-OCT B scan and the OCT photograph. This utilised PinPoint Registration software.

Figure 2

The presence of a nondrusenoid RPE elevation: a pigment epithelial detachment (PED). If confluent drusen and a PED exist, a drusenoid PED was ruled out by the use of point to point correlation with the B scan and the OCT colour photograph. The PED can range in appearance from a large dome-shaped elevation of RPE with low reflectivity within and a visible Bruch's membrane, to an irregular and corrugated detachment that may be shallow with moderate reflectivity throughout or on the underside of the RPE. A PED was graded with or without SRF, IRF, or haemorrhage.

Figure 3

If a drusenoid PED exists and is associated with SRF/IRF/or diffuse retinal thickening over 250 μm in the absence of other pathology to explain its origin.

Figure 4

Features in keeping with a possible peripapillary CNV or idiopathic polypoidal choroidal vasculopathy were also graded if there were: peripapillary exudate, haemorrhage, PED, retinal thickening, or SRF/IRF that were due to no other identifiable ocular pathology and could be seen to approach the OCT macular grid from the optic disc/nasal direction.

Figure 5

The presence of intraretinal cystic spaces, subretinal fluid, or retinal thickening with no other identifiable aetiology to account for these changes were graded as questionable CNV. It has previously been demonstrated quantitatively that a late leak of undetermined source can occur without a PED.