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Fig. 2.18 (a) Detection of IRMA (arrows), larger FAZ (foveal avascular zone), and retinal nonperfused areas in early FA image. In late FA phase (b), a diffuse hyperfluorescence secondary to BRB (blood-retinal barrier) breakdown is detectable, not associated with macular edema in the OCT vertical scan (c) which, on the contrary, shows a thinner retina due to macular ischemia. The EDI-OCT scan allows also a detailed visualization of the choroidal vascularization
progression to high-risk PDR, the results of the randomized clinical trials confirmed that FA is not indicated in such cases of severe NPDR, while this stage of DR could be clearly followed only with color fundus photography [14, 45].
•Thus, the role of FA remained mandatory in cases of PDR, DME, and ischemic maculopathy.
2.2.4Ultrasonography
Ultrasonography is used in case of partial or complete non-visualization of the fundus, due to massive media opacity, such as dense cataract or vitreous hemorrhage, in order to identify the status of the retina. Color Doppler imaging is another method for the hemodynamic evaluation of the orbital vessels, by using ultrasound waves. The retrobulbar blood vessels are evaluated for the assessment of different parameters, such as vascular resistance, blood flow velocity, and systolic and diastolic velocities [46].
2.2.5Optical Coherence Tomography
Optical coherence tomography (OCT) is a noninvasive test widely used in diagnosis and follow-up of macular and optic nerve pathologies. Spectral domain (SD)-OCT
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Fig. 2.19 Color (a) and red-free (b) images show ectasic lesions in the parafoveal region. FA frames (c–e) confirm the localization of these lesion, and OCT horizontal scan (f) highlights the presence of intraretinal liquid temporally to the fovea (white arrow)
is an innovative imaging tool that enables a detailed examination of the inner and outer layers of the retina, including the photoreceptor’s integrity and choroid.
•New advances in the understanding of the retinal morphology in DR derived from the simultaneous correlation between FA and SD-OCT (Figs. 2.19 and 2.20). In a recent work, a correlation between OCT and FA has been performed and the structure and location of microaneurysms have been investigated [47].
•The greatest utility of OCT in the DR is the identification of DME and the monitoring of the therapy, evaluating central retinal thickness (CRT) measurement (Figs. 2.21, 2.22, and 2.23). In patients with NPDR, nonsignificant differences have been noticed between nondiabetics and diabetics without any sign of DR [47].
•The choroidal thickness measurement is a recent imaging option, which enables the evaluation and assessment of the choroid. Recent papers showed successful examination of the choroid of diabetic patients with different degree of DR, using different instruments. No significant differences in subfoveal choroidal thickness were noticed between patients with NPDR and nondiabetic controls [48, 49].
•The acquisition of the peripapillary nerve fiber layer and ganglion cells complex, originally created for the study of glaucoma, is actually another widely used devices also in DR.
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Fig. 2.20 FA frames (a, c, e) of retinal ischemia in diabetic patients which show hyperfluorescent dots secondary to early epiretinal new vessels (arrows), associated with different corresponding macular conditions at OCT (b, d, f)
Fig. 2.21 FA image (a) in mild NPDR. There are more microaneurysms in the temporal side of the macula, and they are responsible of the development of an intraretinal microcyst clearly visible in the OCT horizontal scan (b, arrow)
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Fig. 2.22 (a) Panretinal FA image shows impairment of retinal vessels in the peripheral area of the retina, moderate ischemia, and diffuse BRB (blood-retinal barrier) breakdown. (b) The OCT horizontal scan detects the presence of a large central intraretinal cyst and a reduction in the inner retinal layers thickness
2.2.6Adaptive Optics Scanning Laser Ophthalmoscope
Adaptive optics scanning laser ophthalmoscope (AOSLO) is a new, noninvasive, imaging system that enables a high-resolution imaging of the human retina. A recent analysis of the microscopic changes in NPDR has been performed with AOSLO [50]. The imaging system enables to identify the structural integrity of photoreceptors, the capillary changes, and the development and progression of microaneurysms.
2.2.7Multifocal Electroretinogram
Multifocal electroretinogram (ERG) is currently used to detect early functional changes in patients with DM, even in the absence of clinical findings of DR. Recent studies reported early functional abnormalities in both NPDR and absent DR [51].