By Chong Wee Hou, International Eye Cataract Retina Centre, Singapore

Retinal angiography is the systematic study of blood vessels in the retina and the underlying deeper layer called choroid at the inner back portion of the eye.

Many common eye diseases such as diabetic retinopathy, retinal vascular occlusion, retinal vasculitis and wet age-related macular degeneration which predominantly affect blood vessels in the back of the eye often require retinal angiography for optimal evaluation, treatment and monitoring of the disease.

Retinal angiography is performed as an outpatient procedure in the clinic after application of eye drops to dilate the pupil in the eye. Special fluorescent dyes are then injected into the blood stream through a vein on the back of the hand. This is followed by serial photography of the back of the eye using a special fundus camera to study the retinal and choroidal blood vessels as the dye flows through the eye circulatory system.  The procedure takes up to 30-45 minutes.

Fluorescein sodium is an orange-yellow coloured dye used for studying retinal blood vessels while indocyanine green is a green coloured dye used for studying the deeper choroidal layer. Although retinal angiography is generally very safe, very rarely severe life-threatening allergic reactions to the dye can occur. Hence, the procedure must be performed by a doctor in a set up that has access to emergency life-saving drugs.

Recent advances now allow an option of non-invasive “no injection” retinal angiography using optical coherence tomography (OCT) technology. Although OCT angiography obviates the rare risks associated with injection of dye, it cannot provide information on activity of disease which often manifests as leakage of the dye from abnormal leaky blood vessels.

Dr Ajeet Madhav Wagle, Medical Director and Senior Consultant Ophthalmologist from International Eye Cataract Retina Centre at Farrer Park Medical Centre and Singapore International Eye Cataract Retina Centre at Mount Elizabeth Medical Centre, delivered a guest lecture on retinal angiography to optometry students in Ngee Ann Polytechnic on 27 November 2017. He shared the basic principles and indications of retinal angiography and recent advances in imaging techniques with the students.