Clinical findings characteristic of non-exudative AMD include hard, soft, distinct and indistinct (confluent) drusen and pigmentary abnormalities such as pigment accumulation, migration or RPE depigmentation. Representative features including: basal laminar drusen, predominantly hard drusen, predominantly soft drusen, soft confluent drusen and pigmentary anomalies were compared. Four representative cases of these findings are presented here. Other examples, including predominantly soft drusen, are not presented due to space constraints.
Case 1: basal laminar drusen
A 57-year-old white male had basal laminar drusen in his right eye with a visual acuity of 20/25 OD. Small, yellowish spots scattered in the macula are visible on fundus photography (). FA () shows numerous, well-demarcated, sharp, focal spots of hyperfluorescence. These findings are not visible on OCT fundus images (), where the entire axial signal is summed. However, a cross-sectional OCT image from the 3D-OCT data set reveals distinct drusen () as darkened areas under the slightly elevated RPE. The photoreceptor IS/OS junction and ELM have a rippled appearance. The photoreceptor IS/OS junction is mostly continuous but occasionally disrupted by sharply demarcated deposits (, arrow 1). There is no evidence of PR OS layer thinning. Focal areas of increased light penetration into the choroid (, arrows 2, 3) occur below some drusen, thus suggesting increased RPE transparency and pigmentary changes.
Figure 2 Basal laminar drusen. (A) Colour fundus photograph. (B) Fluorescein angiograph (1:19.6). (C) Optical coherence tomography (OCT) fundus image. (D) Cross-sectional OCT image extracted from the 3-D data set. Arrows: 1, disruption of the photoreceptor inner/outer (more ...)
The ripples in the photoreceptor IS/OS junction can be visualised in the ONL level image () as small, bright areas where the IS/OS junction is displaced from its normal position. The PR OS level image () shows minimal changes with basal laminar drusen. The drusen are hyper-reflective and extend into the OS level, but they also elevate the PR OS layer, which displaces the hyper-reflective IS/OS junction outside the OS level image. Therefore, the net reflectivity change within the PR OS level from this type of drusen is very small. The RPE level image () shows drusen as a characteristic pattern of dark spots, thus indicating RPE elevation from its normal position. The choroid level projection OCT image () shows focal areas of light penetration through the RPE.
Case 2: predominantly hard drusen
A 71-year-old white male had predominantly hard drusen in both eyes with a visual acuity of 20/25 OD and 20/30 OS. Hard drusen are visible as small, well-demarcated spots in the fundus photograph OS () but are not visualised in OCT fundus images (). The OCT cross-sectional images show clustered deposits (), forming larger areas of RPE detachment. The clusters are irregularly shaped but not highly elevated. The Bruch membrane is visible underneath the RPE elevations. A region of photoreceptor atrophy is visible (, white bracket).
Figure 3 Predominantly hard drusen. (A) Colour fundus photograph. (B) OCT fundus image. (C, D) Example cross-sectional OCT images extracted from the 3-D data set. (E—H) Projection OCT fundus images. Brackets in (D) and (F) indicate an area of photoreceptor (more ...)
The ONL level image () shows elevations of the outer retinal complex (RPE and the photoreceptor layer) as bright areas. In contrast to the previous case, these elevations are higher and visible over a significant fraction of the macula. The PR OS level image () displays the highest RPE elevations as small, hyporeflective, regular spots. The larger dark area indicated by a bracket in corresponds to the region free from drusen, which is consistent with the cross-sectional image (). This dark area results from decreased light scattering at the photoreceptor IS/OS junction, thus suggesting photoreceptor impairment. The RPE level image () shows clusters of drusen as large dark areas with irregular shapes.
Case 3: soft confluent drusen
A 69-year-old female had large, soft confluent drusen OS () with a visual acuity of 20/40. The cross-sectional OCT image () reveals weakly scattering deposits forming “dome-like” RPE elevations. The RPE between the drusen is detached from the Bruch membrane, thus indicating confluence of deposits. The photoreceptor IS/OS junction and ELM are absent above the large RPE elevations, thus indicating photoreceptor impairment. A hyper-reflective feature visible in the ONL produces shadowing in deeper layers (arrow 1) that is consistent with the pigmentary changes in the fundus photograph. OCT cross-sectional images show drusen morphology complementary to the findings on the colour fundus image () and the OCT fundus image ().
Figure 4 Soft, confluent drusen. (A) Colour fundus photograph. Arrows 1 and 2 indicate pigmentary changes. (B) OCT fundus image. (C) Example cross-sectional OCT image extracted from the 3-D data set. Arrow 1 shows pigment migration, and arrow 2 shows pigment accumulation. (more ...)
In the ONL level image, highly elevated drusen are visible in () as bright areas with white borders, which correspond to the intersection of the RPE elevations with the ONL level. In the PR OS level image () regular, darkened areas of deposits are surrounded by hyper-reflective bands representing intersection of the elevated RPE with the PR OS level. In the RPE level image (), the dark areas corresponding to RPE elevation are merged due to drusen confluence. The choroidal level image () shows vasculature. The increased choroidal visibility could be related to pigmentary characteristics of the fundus as well as to AMD. Focal dark spots visible in all projection OCT fundus images (eg, arrow 1 in ) correlate with pigmentary changes in the fundus photograph and pigment migration or accumulation in cross-sectional OCT images.
Case 4: pigmentary abnormalities
An 83-year-old white female had dry AMD in both eyes with a visual acuity of 20/30 OU. The red-free photograph () and late-phase FA () show RPE atrophy, pigment clumping and drusen. In the OCT fundus image () hyper-reflective areas are visible, but it is unclear which layers produce this hyper-reflectivity.
Figure 5 Pigmentary abnormalities. (A) Red-free photograph. (B) Fluorescein angiograph. (C) OCT fundus image. (D—G) Cross-sectional OCT fundus images extracted from the 3-D data set. Arrow 1 shows a hyper-reflective feature in the outer nuclear layer, (more ...)
A series of cross-sectional OCT images indicates pigmentary abnormalities. reveals an area of RPE and photoreceptor layer disruption. A hyperscattering feature visible in the ONL in (arrow 1) may indicate inner retinal changes and atrophy of the ONL. Increased choroidal light penetration in suggests RPE depigmentation and atrophy (arrow 2). Focal hyperscattering features seen in correspond to pigment accumulation (arrow 3) or are present in the ONL, thus suggesting pigment migration (arrow 4).
The ONL level image () visualises elevations of the outer retinal complex as bright regions. Focal hyperscattering features indicate pigment migration. Dark areas in the PR OS level image (), corresponding to regions free from drusen in the ONL level, indicate disruptions in the photoreceptor layer (bracket). Hyperscattering regions in the choroidal level projection OCT image () indicate RPE atrophy.