Early Sign of Retinal Neovascularization Evolution in Diabetic Retinopathy: A Longitudinal OCT Angiography Study

En face OCT: Breakthroughs in understanding the pathoanatomy of retinal disease and clinical applications

En face optical coherence tomography (OCT) is a practical and informative imaging modality to noninvasively visualize distinct retinal and choroidal layers by providing coronal images using boundary-specific segmentation. Ongoing research with this method is generating breakthroughs in the illustration of new perspectives of retinal disease. The clinical value of en face OCT as an advanced retinal imaging tool is growing steadily and it has unveiled many new insights into the pathoanatomy of retinal disorders. Moreover, this modality can capture various en face OCT biomarkers that correspond to different cell or tissue subtypes, which were previously only identified through histological or electron microscopy methods, underscoring the significance of this technique in providing valuable pathoanatomical information. In this comprehensive review, we will systematically summarize the en face OCT findings across a broad spectrum of retinal diseases, including disorders of the vitreoretinal interface and retinal vascular system (e.g. paracentral acute middle maculopathy or PAMM and diabetic retinopathy), in addition to the en face OCT features of other conditions such as age-related macular degeneration, pachychoroid disease spectrum, myopic degeneration, uveitis and inflammatory disorders, inherited retinal dystrophies, and drug toxicity. We will discuss and highlight the unique clinical and pathoanatomical findings uncovered with en face OCT of each these diseases mentioned above.

Evaluation of macular retinal oximetry across different levels of diabetic retinopathy: a cross sectional study

BACKGROUND

This study evaluates retinal oxygen saturation and vessel density within the macula and correlates these measures in controls and subjects with type 2 diabetes (DM) with (DMR) and without (DMnR) retinopathy. Changes in retinal oxygen saturation have not been evaluated regionally in diabetic patients.

METHODS

Data from seventy subjects (28 controls, 26 DMnR, and 16 DMR were analyzed. For those with DMR,8 were mild/moderate diabetic retinopathy (NPDR) and 8 severe NPDR/proliferative (PDR). Subjects were categorized with glycosylated hemoglobin A1c and fundus photography. Retinal oximetry measurements were performed within a 300-400 μm region at four diagonal locations 3.1 degrees from the center of the fovea in the superior nasal, superior temporal, inferior nasal, and inferior temporal locations adjacent to the foveal avascular zone (FAZ). Optical coherence tomography angiography (OCTA) was performed and corrected for refractive error. Photoshop and ImageJ were utilized to calculate the superficial capillary plexus vascular density (SCP). Oximetry and OCTA vessel density were analyzed overall and by region.

RESULTS

Average retinal oxygen saturation was highest in DMR (p = 0.008). Average OCTA density was less in DMR compared to controls (p = 0.01), but not compared to DMnR subjects (p = 0.07). A significant inverse correlation was observed between averaged oxygen saturation and SCP vascular density for all subjects (p = 0.02). Duration of DM was positively associated with oxygen saturation (p = 0.01) and negatively with OCTA SCP vascular density (p = 0.009). There were no differential effects of retinal location.

CONCLUSION

To our knowledge, this study is the first to evaluate the relationship between macular oxygen saturation and SCP vascular density at different levels of retinopathy. This may be useful to track patients with DM as they move through stages of retinopathy.

Optical coherence tomography angiography in diabetic retinopathy: A major review

Diabetic retinopathy (DR) is characterized by retinal vasculopathy and is a leading cause of visual impairment. Optical coherence tomography angiography (OCTA) is an innovative imaging technology that can detect various pathologies and quantifiable changes in retinal microvasculature. We briefly describe its functional principles and advantages over fluorescein angiography and perform a comprehensive review on its clinical applications in the screening or management of people with prediabetes, diabetes without clinical retinopathy (NDR), nonproliferative DR (NPDR), proliferative DR (PDR), and diabetic macular edema (DME). OCTA reveals early microvascular alterations in prediabetic and NDR eyes, which may coexist with sub-clinical neuroretinal dysfunction. Its applications in NPDR include measuring ischemia, detecting retinal neovascularization, and timing of early treatment through predicting the risk of retinopathy worsening or development of DME. In PDR, OCTA helps characterize the flow within neovascular complexes and evaluate their progression or regression in response to treatment. In eyes with DME, OCTA perfusion parameters may be of predictive value regarding the visual and anatomical gains associated with treatment. We further discussed the limitations of OCTA and the benefits of its incorporation into an updated DR severity scale.