Optical coherence tomography-angiography (OCT-A) is a relatively new non-invasive imaging technique which provides three-dimensional visualization of the retinal and choroidal microvasculature. Recently, OCT-A is widely used in the diagnosis of age-related macular degeneration (AMD). Purpose: To compare 3 quantitative indexes of foveal avascular zone (FAZ)—area (A), perimeter (Pm), and circularity (C) in patients with early and intermediate nonexudative AMD and healthy subjects using OCT-A. Methods: Eighty-nine patients with nonexudative AMD (n = 89 eyes) were enrolled in the study. They were compared with sex- and age-matched control group of 66 healthy subjects (n = 66 eyes). The patients with nonexudative AMD were divided into 2 subgroups—early AMD (n = 42 eyes) and intermediate AMD (n = 47 eyes). All participants underwent OCT-A (3 × 3 mm scans, Cirrus HD-OCT, Angioplex, Carl Zeiss Meditec, Dublin, CA). Results: There was no statistically significant difference in all 3 assessed indexes between the early AMD subgroup and the control group (A ? P = 0.139; Pm ? P = 0.230; and C ? P = 0.191). There was also no statistically significant difference in all 3 assessed indexes between the intermediate AMD subgroup and the control group (A ? P = 0.106, Pm ? P = 0.124, and C ? P = 0.102, respectively). Conclusions: According to our results from the assessment of FAZ in patients with early and intermediate AMD, we hypothesize that macular perfusion remains fairly unchanged in the nonexudative stages of the disease. OCT-A is a reliable technique for visualizing and quantifying FAZ in patients with nonexudative AMD.
Age-related macular degeneration (AMD) is the leading cause of visual impairment in individuals over the age of 55 years worldwide [
The traditional multimodal imaging modalities in AMD include fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT) [
Recently, OCT-A has been used in many vascular and degenerative diseases (AMD, diabetic retinopathy, central/branch retinal vein occlusion, etc.) to visualize and examine microvasculature, as well as foveal avascular zone (FAZ), in different vascular plexuses separately [
The purpose of the recent study was to compare 3 quantitative indexes of the superficial FAZ―area (A), perimeter (Pm), and circularity (C) in a Caucasian cohort with early and intermediate nonexudative AMD, and healthy subjects using OCT-A.
This prospective study was approved by Ethics Committee of Medical University of Plovdiv, Bulgaria, and conducted in accordance with the requirements of Declaration of Helsinki. A total of 89 consecutive patients (48 female, 41 male) with nonexudative AMD (n = 89 eyes) were enrolled in the study (
Early AMD (n = 42 eyes) | Intermediate AMD (n = 47 eyes) | Control group (n = 66 eyes) | Overall patients (n = 155 eyes) | |
---|---|---|---|---|
Age | ||||
(mean ± SD) Range | 66.5 ± 6.1 56 - 76 | 69 ± 6.3 57 - 81 | 64 ± 4.8 55 - 74 | 66 ± 6 55 - 81 |
Gender | ||||
Male Female | 20 22 | 21 26 | 30 36 | 71 84 |
AMD = age-related macular degeneration, SD = standard deviation.
AMD with drusen ≥ 125 µm and/or pigmentary abnormalities (n = 47 eyes). Criteria for inclusion in AMD patients group were age ≥ 55 years old, drusen and/or retinal pigment epithelium (RPE) abnormalities (hyper-/hypopigmentation) secondary to AMD, a spherical equivalent of ≥ −3D to ≤ +3D. Exclusion criteria were presence of CNV, GA, and other ocular degenerative, vascular or traumatic diseases. They were compared with sex- and age-matched control group of 66 healthy subjects (n = 66 eyes, 36 female and 30 male).The age was 64 ± 4.8 years, range 55 - 74. The inclusion criteria for the healthy volunteers were age ≥ 55 years old, BCVA of ≥ 1.0, and no history or evidence of ocular or systemic disease.
All participants underwent a complete ophthalmologic examination, including BCVA (Snellen charts), slit-lamp biomicroscopy with fundus examination, tonometry, and OCT-A (Cirrus HD-OCT, Angioplex, Carl Zeiss Meditec, Dublin, CA). OCT-A has automatic algorithms that provide estimates of the ‘‘nonflow’’ area in the center of the macula, defining the FAZ (
All statistical analyses were performed using statistical software (IBM SPSS software Version 19; SPSS, Inc., Chicago, IL, USA). The correlation between healthy subjects and each AMD subgroup was generated by independent-samples T-test. P values less than P < 0.05 were considered statistically significant.
Our study analyzed 89 eyes of AMD patients and 66 eyes of healthy volunteers (n = 155 eyes, 66 ± 6 years, range: 55 - 81). In the early AMD subgroup the following FAZ values (mean ± SD) were established: A―0.27 ± 0.09 mm2, Pm―2.28 ± 0.55 mm, and C―0.66 ± 0.08. In the intermediate AMD subgroup the registered values were: A―0.28 ± 0.08 mm2, Pm―2.28 ± 0.34 mm, and C―0.65 ± 0.04, and in the control group: A―0.24 ± 0.08 mm2, Pm―2.16 ± 0.44 mm, and C―0.68 ± 0.05, respectively. The values are summarized in
AMD subgroup and the control group: A - P = 0.139, Pm - P = 0.230, and C - P = 0.191. No statistically significant correlation was found in all 3 assessed indexes between the intermediate AMD subgroup and the control group as well: A - P = 0.106, Pm - P = 0.124, and C - P = 0.102, respectively.
OCT-A enables precise evaluation and quantification of the retinal microvasculature at different levels, without the need of a dye. OCT-A has automatic algorithms defining the FAZ. A relation of FAZ with the age and gender in normal
Superficial FAZ indexes | Early AMD (n = 42 eyes) | Intermediate AMD (n = 47 eyes) | Control group (n = 66 eyes) |
---|---|---|---|
Area (mm2) | 0.27 ± 0.09 | 0.28 ± 0.08 | 0.24 ± 0.08 |
Perimeter (mm) | 2.28 ± 0.55 | 2.28 ± 0.34 | 2.16 ± 0.44 |
Circularity | 0.66 ± 0.08 | 0.65 ± 0.04 | 0.68 ± 0.05 |
eyes has been previously described by various studies. Samara et al. [
In the analysis of superficial FAZ and examined parameters (A, Pm, and C) on 3 × 3-mm scans, our results did not show any statistically significant difference between patients with different stages of nonexudative AMD and control group of healthy volunteers. According to that, we hypothesize that FAZ area and shape, as well as macular perfusion remain fairly unchanged in the nonvascular form of the disease. As far as we know this is the first study which compares FAZ variables such A, Pm, and C in patients with nonexudative AMD using OCT-A.
There are some limitations in this study. We did not evaluate deep FAZ because of the software version limitations. In all conducted studies deep FAZ was measured with a wider range compared to superficial FAZ [
In conclusion, OCT-A is an appropriate non-invasive and reliable method for evaluating superficial FAZ that provides automatic quantitative measurement of this “nonflow’’ area in the center of the macula. According to our results, we hypothesize that macular perfusion remains fairly unchanged in the nonexudative stages of the disease. Additional studies are needed to confirm its application and importance in nonexudative stages of AMD.
The authors declare no conflict of interest.
This publication is funded by Medical University of Plovdiv, Bulgaria (Project № 001/2017).
Stavrev, V., Sivkova, N. and Koleva-Georgieva, D. (2018) Quantitative Assessment of Foveal Avascular Zone in Patients with Early and Intermediate Nonexudative Age-Related Macular Degeneration Using Optical Coherence Tomography-Angiography. Open Journal of Ophthalmology, 8, 133-139. https://doi.org/10.4236/ojoph.2018.83017