SDOCT Imaging to Identify Macular Pathology in Patients Diagnosed with Diabetic Maculopathy by a Digital Photographic Retinal Screening Programme

INTRODUCTION: Diabetic macular edema (DME) is an important cause of vision loss. England has a national systematic photographic retinal screening programme to identify patients with diabetic eye disease. Grading retinal photographs according to this national protocol identifies surrogate markers for DME. We audited a care pathway using a spectral-domain optical coherence tomography (SDOCT) clinic to identify macular pathology in this subset of patients. METHODS: A prospective audit was performed of patients referred from screening with mild to moderate non-proliferative diabetic retinopathy (R1) and surrogate markers for diabetic macular edema (M1) attending an SDOCT clinic. The SDOCT images were graded by an ophthalmologist as SDOCT positive, borderline or negative. SDOCT positive patients were referred to the medical retina clinic. SDOCT negative and borderline patients were further reviewed in the SDOCT clinic in 6 months. RESULTS: From a registered screening population of 17 551 patients with diabetes mellitus, 311 patients met the inclusion criteria between (March 2008 and September 2009). We analyzed images from 311 patients' SDOCT clinic episodes. There were 131 SDOCT negative and 12 borderline patients booked for revisit in the OCT clinic. Twenty-four were referred back to photographic screening for a variety of reasons. A total of 144 were referred to ophthalmology with OCT evidence of definite macular pathology requiring review by an ophthalmologist. DISCUSSION: This analysis shows that patients with diabetes, mild to moderate non-proliferative diabetic retinopathy (R1) and evidence of diabetic maculopathy on non-stereoscopic retinal photographs (M1) have a 42.1% chance of having no macular edema on SDOCT imaging as defined by standard OCT definitions of DME when graded by a retinal specialist. SDOCT imaging is a useful adjunct to colour fundus photography in screening for referable diabetic maculopathy in our screening population

Aspects of control of the retinal and choroidal circulations in normal and diabetic human subjects

This thesis examines aspects of the control of the retinal and choroidal circulations, with particular reference to autoregulation and to regulation mediated by the autonomic nervous system. Handgrip isometric exercise was used to induce an acute rise of mean arterial pressure (MAP) in the region of 20%. The response of the human retinal circulation to acute MAP elevation by isometric exercise was investigated in 9 normal subjects. Autoregulation was demonstrated by an 8.4% rise in flow in response to a 34% rise in retinal perfusion pressure (p=0.0007). The variable in velocity change derived from veins (SD 3.4%) was lower than that from arteries (SD 12.1%), which makes venous measurements more useful for obtaining statistically reliable results from these techniques. The response of the diabetic human retinal circulation to acute MAP elevation by isometric exercise was investigated in 19 diabetic subjects. Measurements were performed at normoglycaemia and hyperglycaemia. The conductance of the retinal circulation, defined as flow/perfusion pressure, was calculated. Conductance was significantly elevated at hyperglycaemia (p0.007). Conductance decreased significantly (p&lt;0.05) in response to elevation of blood pressure both at normoglycaemia and hyperglycaemia. The conductance change per unit perfusion pressure change was significantly smaller in diabetics than in normal subjects. Autonomic neuropathy had no effect on conductance nor on the change in conductance in response to isometric exercise.21 diabetic subjects and 13 control subjects had intraocular pressure (IOP) measured at rest and again during acute MAP elevation by isometric exercise. In normal subjects there were no detectable changes in IOP. There was a rise in IOP in a significant proportion of diabetic subjects, both at normoglycaemia (p=0.007) and hyperglycaemia (p=0.002).</p

Outcome of primary SDOCT visits (n = 311).

<p>RAP; retinal angiomatous proliferation, RPE; retinal pigment epithelium, DD; disc diameter.</p><p>Table footnote: SDOCT borderline scans had an intra-retinal cystic space on a single scan without a change in the ILM contour. This group has recently been published as having a variety of causes for this appearance, not limited to DME, and was identified as a group to be observed. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0014811#pone.0014811-Jittpoonkuson1" target="_blank">[20]</a></p

ENSC grading.

<p>DD; disc diameter, VA; visual acuity.</p

OCT clinic pathway.

<p>The number of patients identified in this study at each section of this pathway are highlighted. Note that any R2 and R3 identified at primary screening are referred directly to ophthalmology clinic and do not enter the SDOCT clinical pathway represented in Figure 1.</p