Measuring Choroidal Thickness Using Optical Coherence Tomography

Diabetic retinopathy (DR) is the most common and specific complication of DM. It is one of the leading causes of preventable blindness in the adult working population. (1) DR was the fifth leading cause of blindness and of moderate and severe vision impairment.

Global prevalence of diabetic retinopathy was 22.27% and prevalence was highest in Africa (35.90%). (1)

Fortunately, much of the visual loss from DR is preventable, and the rates of vision loss from diabetes and DR have declined over the past few decades due to advances in ocular disease assessment, screening, imaging and treatment in recent years. (2)

The outer third of the retina gets oxygen and nutrients from choroid. The three vascular layers of choroid are chorio capillaries layer, Sattler layer and Haller layer. (3)

A healthy choroid is essential for retinal function by continuous perfusion into the outer retina, which plays critical roles in thermoregulation of the retina, maintenance of the anatomic position of the retina, removal of residues, and secretion of growth factors. (4-5)

The vascular choroid changes of the diabetic patients are quite similar to those seen in DR, such as increased vascular tortuosity, vascular outpouchings, microaneurysms, nonperfusion areas, vascular dilations and narrowing, and choroidal neovascularization. (6)

Until recently, the choroid could only be evaluated by indocyanine green angiography, laser Doppler flowmetry, and ultrasonography. (6) Optical coherence tomography (OCT) is a non-invasive imaging modality, which is used in acquiring high-resolution sections of retina. (5)

Inclusion criteria

• All known Type 2 DM patients aged 30 to 95 years either gender who presented to ophthalmology clinics in Assuit ophthalmology hospital with no history of ocular treatment (ocular treatment naïve) and visual acuity of 0.1 (6/60) or more that are able to complete an eye examination, and non-diabetic healthy individuals (HbA1c <7) will be included in the study.

Exclusion criteria

• Known diagnosis of any other retinal disease, glaucoma, neurodegenerative disease, and any significant media opacities that precluded fundus imaging and not giving consent will be excluded.