Dr. Usha Shree

Several visual symptoms in a person with diabetes should prompt same-day or next-day retinal specialist review rather than a routine appointment. Sudden onset of floaters, which are new spots, threads, or a shower of dark dots appearing in the vision, may represent a vitreous haemorrhage from a bleeding new vessel and need prompt assessment. A dark shadow, curtain, or veil that covers part of the visual field may indicate a retinal haemorrhage or, more urgently, a retinal detachment. Sudden blurring of central vision that was not present the day before may indicate acute macular oedema. Distortion of straight lines, where lines appear wavy or bent, suggests macular involvement that requires prompt treatment. Any of these symptoms in a person with known diabetic retinopathy, or in a person with longstanding or poorly controlled diabetes who has not had a recent retinal examination, should be assessed as urgent. In contrast, a person with diabetes who has no visual symptoms but has not had a retinal examination in the past twelve months should be seen for a routine annual review, not an emergency. At Kasturi Nagar, Bengaluru, I prioritise urgent review for any sudden visual change in a diabetic patient because the window for effective intervention in vitreous haemorrhage and traction retinal detachment narrows quickly once the process has begun.

Fundus fluorescein angiography (FFA) and OCT angiography (OCT-A) are both imaging modalities that reveal the retinal vasculature, but they work differently and have different clinical strengths. FFA involves injecting a fluorescent dye into a vein in the arm and photographing the retina as the dye passes through the blood vessels. It reveals areas of active vascular leakage, identifies zones of capillary non-perfusion where the ischaemia driving neovascularisation originates, and precisely maps the distribution of new vessel formation. It is particularly valuable for treatment planning before panretinal laser and for establishing the extent of ischaemia. OCT-A is non-invasive and does not require dye injection. It maps the retinal capillary plexuses using motion contrast and provides exquisite detail of the foveal avascular zone and early capillary dropout with resolution that FFA cannot match. It is increasingly used for detecting early diabetic vascular changes before they are clinically apparent, and for monitoring subtle progression. In practice, both have a role: FFA for leakage mapping and treatment planning, and OCT-A for early detection and monitoring. The choice depends on the clinical question being answered at each visit.

Vitrectomy becomes necessary for diabetic retinopathy in three main situations. The first is a dense vitreous haemorrhage that has not cleared spontaneously after an adequate waiting period, typically four to six weeks, where the blood in the vitreous cavity prevents the retina from being examined or treated with laser. The second is a traction retinal detachment, where fibrovascular membranes attached to new vessels on the retinal surface have contracted and pulled the retina away from the eye wall, or are threatening to do so. The third is when dense fibrovascular membranes are present that cannot be treated with laser or injection alone. The procedure is performed in a theatre under local or general anaesthesia, using fine microsurgical instruments introduced through three small incisions in the sclera. The vitreous gel is removed, fibrovascular membranes are carefully peeled from the retinal surface, and the retina is reattached if it has detached. A gas bubble or silicone oil may be used at the end of surgery to help maintain the retina in position. Visual outcomes are best when surgery is performed before traction detachment has involved the central macula, which is why early specialist review of any sudden visual change in a patient with diabetes is essential.

Anti-VEGF injections are the first-line treatment for centre-involving diabetic macular oedema and work by neutralising vascular endothelial growth factor, the protein responsible for the vascular leakage that accumulates as fluid in the macula. The injection involves a small amount of the anti-VEGF medication being introduced into the vitreous cavity of the eye through the sclera using a fine needle, performed under topical anaesthetic eye drops in a minor outpatient procedure that takes a few minutes. The eye is cleaned carefully beforehand to minimise infection risk, and most patients experience minimal discomfort. The treatment protocol for diabetic macular oedema typically begins with a loading phase of three to four monthly injections, after which the OCT scan at each visit guides whether the interval can be extended or whether further monthly injections are needed. Visual improvement is often seen within the first few injections and continues over the treatment course, but results depend on the severity and duration of the oedema before treatment began. At Kasturi Nagar, Bengaluru, I use OCT monitoring after each injection to assess the response and adjust the schedule for each patient individually.