title: Optical Coherence Tomographic Angiography in Type 2 Diabetes and Diabetic Retinopathy.
abstract: OBJECTIVE
  Optical coherence tomographic angiography (OCT-A) is able to visualize retinal microvasculature without the need for injection of fluorescein contrast dye. Nevertheless, it is only able to capture a limited view of macula and does not show leakage.
  
  
  OBJECTIVE
  To evaluate the retinal microvasculature using OCT-A in patients with type 2 diabetes as well as the association of OCT-A characteristics with diabetic retinopathy (DR) and systemic risk factors.
  
  
  METHODS
  A prospective, observational study was conducted from January 1 to June 30, 2016, at medical retina clinics at the Singapore National Eye Center among 50 patients with type 2 diabetes with and without DR (n = 100 eyes). We examined the retinal microvasculature with swept-source OCT-A and a semiautomated software to measure the capillary density index (CDI) and fractal dimension (FD) at the superficial vascular plexus (SVP) and deep retinal vascular plexus (DVP). We collected data on histories of patients' glycated hemoglobin A1c, hypertension, hyperlipidemia, smoking, and renal impairment.
  
  
  METHODS
  The CDI and FD at the SVP and DVP for each severity level of DR and the association of systemic risk factors vs the CDI and FD.
  
  
  RESULTS
  The mean (SD) glycated hemoglobin A1c of the 50 patients (26 men and 24 women; 35 Chinese; mean [SD] age, 59.5 [8.9] years) was 7.9% (1.7%). The mean (SD) CDI at the SVP decreased from 0.358 (0.017) in patients with no DR to 0.338 (0.012) in patients with proliferative DR (P < .001) and at the DVP decreased in patients with no DR from 0.361 (0.019) to 0.345 (0.020) in patients with proliferative DR (P = .04). The mean (SD) FD at the SVP increased from 1.53 (0.05) in patients with no DR to 1.60 (0.05) in patients with proliferative DR (P < .01) and at the DVP increased from 1.55 (0.06) in patients with no DR to 1.61 (0.05) in patients with proliferative DR (P = .02). For systemic risk factors, hyperlipidemia (odds ratio [OR], 9.82; 95% CI, 6.92-11.23; P < .001), smoking (OR, 10.90; 95% CI, 8.23-12.34; P < .001), and renal impairment (OR, 3.72; 95% CI, 1.80-4.81; P = .05) were associated with reduced CDI, while increased glycated hemoglobin A1c (≥8%) (OR, 8.77; 95% CI, 5.23-10.81; P < .01) and renal impairment (OR, 10.30; 95% CI, 8.21-11.91; P < .001) were associated with increased FD.
  
  
  CONCLUSIONS
  Optical coherence tomographic angiography is a novel imaging modality to quantify the retinal capillary microvasculature in patients with diabetes. It can be potentially used in interventional trials to study the effect of systemic risk factors on the microvasculature that was previously not accessible in a noninvasive manner. The relevance of these findings relative to visual acuity, however, remains largely unknown at this time.
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Daniel Shu Wei
authors.initials: DSW
authors.lastname: Ting
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Gavin Siew Wei
authors.initials: GSW
authors.lastname: Tan
authors.affiliation: Singapore Eye Research Institute, Singapore, Singapore4National healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore.
authors.forename: Rupesh
authors.initials: R
authors.lastname: Agrawal
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yanagi
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore.
authors.forename: Nicole Ming
authors.initials: NM
authors.lastname: Sie
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore.
authors.forename: Chee Wai
authors.initials: CW
authors.lastname: Wong
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Ian Yew
authors.initials: IY
authors.lastname: San Yeo
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Shu Yen
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Chui Ming Gemmy
authors.initials: CMG
authors.lastname: Cheung
authors.affiliation: Vitreo-retinal Department, Singapore National Eye Center, Singapore, Singapore2Singapore Eye Research Institute, Singapore, Singapore3Duke-National University Singapore Medical School, Singapore, Singapore.
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
mesh_terms: D002196:Capillaries / Q000000981:diagnostic imaging / Q000473:pathology; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis*; D003930:Diabetic Retinopathy / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005451:Fluorescein Angiography; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006949:Hyperlipidemias / Q000473:pathology; D007674:Kidney Diseases / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012171:Retinal Vessels / Q000000981:diagnostic imaging* / Q000473:pathology*; D012307:Risk Factors; D012907:Smoking / Q000473:pathology; D041623:Tomography, Optical Coherence
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human