Reversible blindness associated with severe Diabetic Ketoacidosis

Abstract

Diabetes mellitus is commonly associated with gradual onset of visual loss. Reversible acute blindness associated with diabetic ketoacidosis has been reported only once previously [1]. Case report We report a case of sudden onset reversible blindness associated with diabetic ketoacidosis. A 23-year-old woman with a history of insulin dependent diabetes mellitus, hypercholesterolemia and benign intracranial hypertension presented with complete blindness on waking up from sleep. She denied any methanol or alcohol ingestion. Her medication included insulin, metformin, simvastatin and the oral contraceptive pill. On examination she was alert and her pupils were dilated and did not react to light. She had no perception of light in either eye. An ophthalmology review revealed clear corneas, normal fundoscopy and no local cause for loss of vision. Arterial blood gas analysis revealed a pH of < 6.8, PaO2 17.3 kPa, PaCO2 1.5 kPa and base excess of )28.2 mmol.l)1. Her blood glucose was 24 mmol.l)1. Computed tomography of her head was normal. She was treated initially with intravenous fluids, insulin and antibiotics. She subsequently needed a sodium bicarbonate infusion to treat her resistant acidosis. Her vision returned to normal when her arterial pH improved to 7.0. Discussion Common non-metabolic causes of sudden onset of blindness include trauma and vascular injury where the reversibility of blindness is not related to the arterial pH of blood. The course of sudden onset of complete blindness with normal fundoscopic examination and head computed tomography, negative history of any methanol ingestion, trauma or vascular event and rapid return of full vision once the arterial pH was > 7.0 after correction of acidosis, strongly suggests that diabetic ketoacidosis was the causative factor for the blindness in this case. A similar case of transient reversible blindness due to diabetic ketoacidosis has been reported by Deutsch [1]. Also, other cases of similar presentation have been reported where alcoholic ketoacidosis was found to be the reason for severe metabolic acidoses [2, 3]. The common aspects in all of these cases are a severe metabolic acidosis with an arterial pH < 7.0 and a rapid reversal of blindness with correction of the acidosis. The exact mechanism whereby a severe metabolic acidosis causes reversible blindness is uncertain. However, studies on fish and salamander by Feeney et al. [2] describe a possible explanation: extracellular acidification to a pH < 7.0 uncouples the horizontal cells, preventing the transmission of photoreceptor information into the visual neuronal network.