|Year : 2013 | Volume
| Issue : 2 | Page : 23-27
Optical coherence tomography evaluation of retinal and optic nerve head neovascularization in proliferative diabetic retinopathy
Mahmoud Alaa Aboeuhussein
Department of Ophthalmology, Faculty of Medicine, Alexandria University, Egypt
|Date of Web Publication||24-Jun-2014|
Mahmoud Alaa Aboeuhussein
9 Emarat Hayat Eltadress, Smoha, Alexandria
Source of Support: None, Conflict of Interest: None
Purpose: The purpose of this study is to describe the in vivo spatial and morphological vitreoretinal relationships associated with diabetic retinal neovascularization (NV) using optical coherence tomography (OCT). Patient and Methods: This was a prospective observational study that involved 50 eyes of 46 patients with proliferative diabetic retinopathy (PDR) documented by fluorescein angiography either treatment naοve or laser treated were included. Qualitative assessment of macula, retina and optic disc head OCT imaging of patients with PDR. The morphology and plane of retinal neovascularization at the disc (NVD) and elsewhere in the retina (NVE) was examined, and the posterior vitreous relationships were evaluated. Results: The mean age of patients was 52.1 years. Ten patients had type 1 diabetes and 36 had type 2 diabetes. It was possible to evaluate changes of retina, vessels and vitreous in the 50 eyes. This study describes OCT characteristics of: NVD in 35 eyes (70%), NVEs in 20 eyes (40%), NV causing traction without retinal detachment in 15 eyes (30%), and NV causing traction with retinal detachment in 10 eyes (20%). Conclusion: It is possible to image NV of proliferative retinopathy using spectral domain OCT and to visualize the retinal, vascular and vitreous changes associated with NV.
Keywords: Neovascularization, optical coherence tomography, proliferative diabetic retinopathy
|How to cite this article:|
Aboeuhussein MA. Optical coherence tomography evaluation of retinal and optic nerve head neovascularization in proliferative diabetic retinopathy. Egypt Retina J 2013;1:23-7
|How to cite this URL:|
Aboeuhussein MA. Optical coherence tomography evaluation of retinal and optic nerve head neovascularization in proliferative diabetic retinopathy. Egypt Retina J [serial online] 2013 [cited 2020 Apr 7];1:23-7. Available from: http://www.egyptretinaj.com/text.asp?2013/1/2/23/135244
| Introduction|| |
In many developed countries, diabetic retinopathy is an increasing cause of blindness, especially in the working age population.  Individuals with diabetes are 25 times more likely to become blind than those in the general population.  Ischemia causes the release of cytokines such as vascular endothelial growth factor into the vitreous cavity is known to be one of the main drivers of new vessel formation in retinal proliferative disease.  Proliferative diabetic retinopathy (PDR) is a major cause of visual loss in patients with diabetes and is characterized by neovascularization (NV) that occurs at the vitreoretinal interface and in the vitreous. It can cause vitreous hemorrhage, neovascular glaucoma, and tractional retinal detachment (TRD), which can result in visual loss. 
Retinal and optic nerve head NV are the hallmark of PDR and responsible for the hemorrhagic complications that lead to significant visual loss in this disorder. In diabetics, the retinal neovascular outgrowths are characterized by a rete of new vessels arising from the venous side of the circulation, and penetrate the internal limiting membrane.  The early new vessels lie flat and orientate parallel with the retinal surface. In response to the ongoing hypoxic stimulus, retinal ischemia and elevated intraocular vascular endothelial growth factor levels, the new vessels expand around a central peduncle. Mature retinal neovascular complexes resemble "fronds" and continue to grow in the shape of a flat cartwheel or umbrella.  Shimizu et al. demonstrated that the mid-peripheral retina was far more prone to developing capillary nonperfusion than the posterior retina.  In current clinical practice, retinal NV in PDR is classified using the modified Airlie House Classification that defines four key factors on standard fundus photographs: The location of new vessels; the extent of fibrous proliferation; the plane of proliferation; and the presence of retinal elevation. 
The natural history of severe and advanced neovascularization at the disc (NVD) and elsewhere (NVE) results in the development of TRD, avulsion of new vessels into the vitreous, perhaps retinoschisis, and hemorrhagic complications at the vitreoretinal interface. 
Optical coherence tomography (OCT) is well-established as an accurate imaging study of retinal pathology with good correlation between histology of animals and humans in vivo. ,, OCT images provide an accurate visualization of the actual retinal architecture in vivo. The clinical and histologic findings in NV have been described. , However, there are only few studies regarding the spectral domain OCT correlate of NV. The purpose of this study was to describe the structure of these preretinal new vessels and to determine whether findings such as traction on the retina from the NV can be seen using spectral domain OCT.
| Patient and Methods|| |
This was a prospective observational study that involved 50 eyes of 46 patients with PDR documented by fluorescein angiography either treatment naοve or laser treated were included. The research protocol was approved by the Alexandria University Institutional Review Board and Ethics Committee.
The patients inclusion criteria: Diabetic patients older than 18 years of age; glycosylated hemoglobin (HBA1C) level of ≤10%; no previous intraocular drug therapy or surgery other than cataract surgery to the study eye; blood pressure <180/110; and absence of any systemic medication known to be toxic to the retina.
We only included patients with neovascular complexes that could be captured on the standard disc and macula OCT scans that are outlined in the OCT protocol below. Patients with peripheral NVE complexes were out of reach of the OCT imaging protocol.
Examination included Snellen best-corrected visual acuity, slit-lamp examination, fundus biomicroscopy, color fundus photography, fluorescein angiogram using Topcon camera, and OCT examination centered on the area of abnormal blood vessels was performed.
Optical coherence tomography imaging was performed using Cirrus-HD OCT software version 4.5 (Cirrus HD-OCT; Carl Zeiss Meditech, Inc., Dublin, CA, USA). This software version allows for the acquisition of high-definition 1-line raster scans that are constructed from 20 B-scans obtained at the same location and processed using a unique Selective Pixel Profiling system. The 1-line raster is a 6 mm line consisting of 4096 A-scans with an axial resolution of ~ 5-6 μm and a transverse resolution of ~15-20 μm.
The spectral domain OCT cross-sectional images and OCT fundus image were correlated with color fundus photographs and fluorescein angiography and evaluated for characteristic changes of the vessels, retina, and vitreous overlying the areas of abnormal vasculature.
| Results|| |
The studied group included 50 eyes of 46 patients with PDR were imaged using the Cirrus HD-OCT. The patients consisted of 25 men and 21 women, with a mean age of 52.1 (range: 27-65 years). Ten patients had type 1 diabetes and 36 had type 2 diabetes. The mean HbA1C in all enrolled patients was 8.5% (range: 7.3-10.4%). Ten eyes had previous laser treatment (pan retinal photocoagulation). Previous cataract surgery was performed in 15 eyes. It was possible to evaluate changes of retina, vessels and vitreous in all eyes.
The images were examined to describe the characteristic appearance of:
Neovascularization at the disc in 35 eyes (70%), NVEs in 20 eyes (40%), NV causing traction without retinal detachment in 15 eyes (30%), and NV causing TRD in 10 eyes (20%).
Neovascularization of the disc
Neovascularization at the disc was detected in 35 eyes (70%). It was possible to identify NVD using spectral domain OCT in all of the cases [Figure 1], [Figure 2], [Figure 3]. It appeared as hyperreflective tissue arising from the disc with optical shadowing. In all cases, we were able to observe a connection between the new vessels and the optic disc.
In 20 eyes (40%) that were examined, NVE of the retina was noted [Figure 4] and [Figure 5]. The NV is seen as the hyperreflective loops of relatively homogenous hyperreflectivity. There is increased reflectivity in the nerve fiber and ganglion cell layers intervening between the NVE loops. The boundary between the different retinal layers appears irregular.
Neovascularization with traction but without detachment
In 15 eyes (30%) that were examined, traction on the retina was observed without retinal detachment [Figure 6]. This patient has a thickened posterior hyaloid, NV is seen as a hyperreflective material within the inner retinal layer and projecting into the vitreous. Structural changes are noted in inner retinal layers as a result of traction, but retinal detachment is not present. In addition, focal dots of hyperreflective material corresponding to vessels are evident in the inner retina. Optical shadowing is again seen in the outer retina behind the more reflective new vessels.
Neovascularization with traction and retinal detachment
In 10 eyes that were examined (20%), traction from the NV was observed with accompanying retinal detachment [Figure 7]. The posterior hyaloid is attached and thickened. The detached retina has lost its architectural organization. All these cases were associated with tractional retinoschisis on either sides of retinal detachment. Retinal detachment appears as a full-thickness separation of the moderately reflective neurosensory retina from the underlying, more reflective retinal pigment epithelium band (asterix). Conversely, retinoschisis is a splitting of the neurosensory retina, leaving a thin band of moderately reflective tissue over the more reflective retinal pigment epithelium band (arrow).
|Figure 7: Neovascularization elsewhere with tractional retinal detachment and retinoschisis|
Click here to view
| Discussion|| |
This study shows that OCT evaluation of retinal and optic disc new vessels due to PDR is possible. The resolution on the macular cube scan was not always enough to identify the areas of NV in detail. The 1-line raster proved superior to the cube scan in delineating the fine detail of the NV because of image averaging that allows for greater resolution. Newer generation OCTs will allow for the acquisition of macular cube scans with resolution comparable with that of the 1-line scan. In addition, newer OCTs will be able to get more peripheral 1-line scans and will potentially allow for scanning of the entire retina.
The posterior hyaloid can be visualized and can be determined whether it is attached to the newly formed vessels in many cases of patients with retinal NV. If the posterior hyaloid is strongly attached to the NV in the area of the optic nerve, it can make the detachment of the hyaloid more difficult with higher risk of bleeding during surgery. Areas with traction with and without retinal detachment were able to be identified. This prior knowledge may be important in the clinic to assess progression and for surgical planning.
Spectral domain OCT is a noninvasive technology that can be used to image NV and has clinical utility in that OCT may be useful to monitor subtle changes such as progression of the NV and traction on the retina over time.
Diabetic patients often have significant cardiac and renal disease, and together with unstable glycemic control, not all patients are suitable to undergo fluorescein angiography. In such cases, fluorescein angiography is deferred and clinical biomicroscopy alone is used to confirm the diagnosis of PDR. We would suggest that OCT be used as a noninvasive tool to diagnose suspicious NVD complexes in suspected PDR disease. Although the OCT provides no index of the activity of PDR disease, detection of NVD would assist clinicians with the decision to perform urgent retinal laser therapy in suspected cases.
The development of worsening grades of PDR disease, from subclinical to large NVE and NVD complexes, was previously reported using fundus fluorescein angiography and pathological studies.  The use of OCT to show the vitreoretinal adhesions and tractional retinal morphological changes provides clinicians with a better understanding of the complex natural history of PDR disease.
A study limitation includes the inability to image far beyond the vascular arcades with current commercially available OCT devices.
Cho et al.  recently reported OCT features of retinal NV in a small group of patients. This was the first study to show spectral domain OCT evaluation of retinal and disc NV in association with PDR. They reported 16 eyes of 14 patients with PDR were imaged using the Cirrus HD-OCT. Nine patients presented with NVD (56.2%). In six of the images (37.5%) that were examined, NV of the retina was noted. In four of the images (25%) that were examined, traction on the retina was observed without retinal detachment. In three of the images (18.8%) that were examined, traction from the NV was observed with accompanying retinal detachment.
| Conclusion|| |
It is possible to image NV of proliferative retinopathy using spectral domain OCT and to visualize the retinal, vascular and vitreous changes associated with NV.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]