Table 1.
Studies on early optical coherence tomography biomarkers linked with age-related macular degeneration (continuation of the table on pages 5–7).
| Author | Year | Number of Patients/Eyes Included | Biomarker | Characteristics of Biomarker | Description | Correlation with AMD | Method | The Role of Biomarker in Clinical Practice |
|---|---|---|---|---|---|---|---|---|
| Hilely et al. [24] | 2021 | 45 eyes | Drusen height | Quantitative biomarker | The height of the drusen causing reduced choroidal perfusion might lead to RPE 1 pump failure | An early sign of atrophy on OCT 2 imaging | OCT 2 | Predictor |
| Au et al. [25] | 2022 | 155 eyes | Drusen height | Quantitative biomarker | Drusen height, more so than drusen GHD 3, is correlated with the presence of OCT 1 predictors of atrophy | Early biomarker for targeting early intervention to prevent atrophy and vision loss | OCT 2 | Predictor |
| Abdelfattah et al. [26] | 2016 | 89 patients |
Drusen volume | Quantitative biomarker | Quantifying drusen volume through OCT 2 could be a promising biomarker for identifying patients at higher risk of developing MNV 4 | Important predictor for the development of advanced AMD 5 at 12 and 24 months of follow-up in the fellow eye | OCT 2 | Predictor |
| Lamin et al. [27] | 2019 | 248 patients | Drusen volume | Quantitative biomarker |
Increase in the overall amount of drusen measured through optical coherence tomography before neovascular AMD 5 development | A useful method for detecting early signs of neovascular AMD 5 in those at risk for the disease | OCT 2 | Predictor |
| Amissah-Arthur et al. [19] | 2012 | 749 patients | RPE 1 changes | Qualitative biomarker |
Abnormalities in the RPE 1 without any visible alterations in the outer neural retina | Possible to diagnose conversion to a wet form of AMD 5 in the fellow eye by looking for small changes in RPE 1 contours/elevation | OCT 2 | Predictor |
| Nagai et al. [13] | 2020 | 30 eyes | PROS 6 | Quantitative biomarker | The length of the PROS 6 where the visual pigment is concentrated | Potential sensitive biomarker for the degeneration of photoreceptors | OCT 2 | Risk factor |
| Jaffe et al. (CAM Report 5) [28] |
2021 | Not available | Intraretinal hyperreflective foci, focal RPE 1 thickening, and choroidal hypertransmission | Qualitative biomarker |
Early signs of RPE 1 damage and disturbance that may lead to geographic atrophy | Predictors of atrophy | OCT 2 | Predictor |
| Harada et al. [10] | 2022 | 24 eyes | CCFA 7 ratio | Quantitative biomarker | Percentage of choriocapillaris slab area to analyzed area from OCTA 8 images | Smaller CCFA 7 ratio in AMD high-risk fellow eyes than in control eyes, indicating decline in choriocapillaris flow | OCTA 8 | Risk factor |
| Trinh et al. [29] | 2019 | 63 eyes | GCL 9 thickness | Quantitative biomarker | Reduction in GCL 9 thickness in AMD eyes | Structural loss in the early stages of AMD may be linked to retinal vascular alterations | OCT 2/OCTA 8 | Predictor |
| Trinh et al. [29] | 2019 | 63 eyes | Vascular density in the superficial capillary plexus (SCP) 10 | Quantitative biomarker | As different OCTA 8 modalities utilize different scanning techniques and definitions to automatically separate the retinal vasculature from the scan, differences between OCTA 8 studies may be device-related | Substantial reduction in the SCP’s 10 vascular density in AMD patients; however, vascular density in DCP 11 was not significantly decreased | OCTA 8 | Risk factor |
| Lamin et al. [14] | 2020 | 51 eyes | Drusen load | Quantitative biomarker | Comparison of drusen load between the two types of CNV 12 | Significant rise in the area and volume of drusen during the 12 months preceding the onset of occult CNV 12 | OCT 2 | Risk factor |
| Lamin et al. [14] | 2020 | 51 eyes | Retinal layer volumes | Quantitative biomarker | Comparison of retinal layer volumes between CNV 12 types | Decrease in ONL 13 volume and increase in outer plexiform layer volume in eyes with occult CNV 12 | OCT 2 | Risk factor |
| Menteş et al. [30] | 2019 | 27 eyes | Drusen load | Quantitative biomarker | Comparison of drusen load between the two types of CNV 12 | Significant rise in the area and volume of drusen during the 12 months preceding the onset of occult CNV 12 | OCT 2 | Risk factor |
| Shi et al. [31] | 2019 | 100 eyes | DLS 14 | Qualitative biomarker |
Identification of type 1 MNV in eyes with nonexudative AMD | DLS 14 has good predictive values for identifying type 1 MNV 2 | OCT 2 | Predictor |
| Oliveira Dias et al. [32] | 2018 | 160 patients | Subclinical neovascularization | Qualitative biomarker |
Neovascularization was not visible on clinical exam, but detected on OCT 2 imaging | Increased risk of exudation in eyes with subclinical MNV 4 compared to eyes without detectable MNV 4 | OCTA 8 | Risk factor |
| Nassisi et al. [33] | 2019 | 501 eyes | IHRF 15, hRF 16, DLs 14, SDD 17, and Drusen volume | Qualitative biomarkers (except drusen volume—quantitative biomarker) |
Various features visible on OCT imaging | IHRF 15, hRF 16 within a drusen-like lesion, and SDD 17 were significantly associated with an increased risk of progression to late AMD 5. SDD 17 is strongly associated with the development of GA 18 and type 3 MNV 4. Drusen volume was not significantly associated with the development of MNV 4 | OCT 2 | Risk factors |
| Kang et al. [34] | 2022 | 70 eyes | Chorioretinal thickness, RPE 1 degenerative features, and SDDs 17 | Chorioretinal thickness—quantitative biomarker; RPE 1 degenerative features and SDDs 17—qualitative biomarkers | The thickness of the retina and choroid in eyes with RPE 1 degeneration is comparatively reduced to those without this degeneration | Early AMD 5 eyes with SDDs 17 are prone to overall chorioretinal degeneration. Fellow eyes with neovascular AMD 5 showed greater proportions of RPE 1 degeneration and a thicker retina and choroid | OCT 2 | Risk factor |
| Kwak et al. [35] | 2021 | 93 eyes | CVI 19 | Quantitative biomarker | Lower CVI 19 values in unaffected fellow eyes may be associated with possible subclinical disease | Significant correlation between the incidence of fellow eye type 3 neovascularization and the presence of large soft drusen, reticular pseudodrusen, and lower choroidal vascularity index CVI 19 values | OCT 2 | Risk factor |
| Toprak et al. [36] | 2017 | 47 eyes | RPE 1 and EZ 20 reflectivity | Qualitative biomarker |
Lower reflectivities suggest early photoreceptor damage | Non-neovascular AMD patients have significantly lower reflectivities compared to healthy controls. | OCT 2 | Predictor |
| Schick et al. [21] | 2015 | 104 patients | Macular drusen | Quantitative biomarker | More than 20 drusen in non-affected eyes indicate potential biomarkers for more severe progression of the disease | Prevalence of more than 20 macular drusen is more prevalent in non-affected eyes of individuals with early onset of unilateral neovascular AMD 5 | OCT 2 | Risk factor |
| RPD 21 | Qualitative biomarker |
Prevalence increases with age and is more common in the late-onset CNV 12 group; link with neovascular AMD 5 | RPDs 21 were more commonly observed in the late-onset CNV 12 group than in the no-CNV 12 group. | Predictor |
1 RPE—retinal pigment epithelium; 2 OCT—optical coherence tomography; 3 GHD—greatest horizontal diameter; 4 MNV—macular neovascularization; 5 AMD—age-related macular degeneration; 6 PROS—photoreceptor outer segment; 7 CCFA—choriocapillaris flow area; 8 OCTA—optical coherence tomography angiography; 9 GCL—ganglion cell layer; 10 SCP—superficial capillary plexus; 11 DCP deep capillary plexus; 12 CNV—choroidal neovascularization; 13 ONL—outer nuclear layer; 14 DLs—drusenoid lesions; 15 IHRF—intraretinal hyperreflective foci; 16 hRF—hyporeflective foci; 17 SDDs—subretinal drusenoid deposits; 18 GA—geographic atrophy; 19 CVI—choroidal vascularity index; 20 EZ—ellipsoid zone; and 21 RPD—reticular pseudodrusen.