Diabetes and double vision
Diabetes causes a wide array of problems throughout the body, and the eye is no exception. Double vision (also known as diplopia), is one of those problems. It can occur suddenly or more gradually and be quite uncomfortable and alarming.
Diplopia occurs due to a complication called acute focal neuropathy, which is typically a result of uncontrolled blood sugar (glucose) or vascular damage. The aforementioned damage to circulation causes a palsy, or paralysis, of the various nerves that move the eyes. If one muscle or a group of muscles in one eye does/do not work properly, the eyes are no longer aligned and two images are presented to the brain instead of one. Consequently, daily tasks such as driving, reading and other visual tasks become quite difficult to perform.
The cranial nerves that can cause such palsies are the third, fourth and sixth cranial nerves. Their individual presenting features are summarised below:
Third nerve palsy: presents with a characteristic down and out position of the affected eye. Frequently the patient also presents with a droopy eyelid (ptosis), and a dilated pupil (mydriasis). Double vision will not be present if the eyelid is covering the affected eye.
Fourth nerve: presents with vertical double vision, this worsens on looking down (for example to read) or walking down stairs.
Sixth nerve palsy: presents with the inability of the affected eye to turn outward. The double vision is horizontal, worse in the distance and increases on looking to the affected side.
The majority of these palsies start to improve over weeks to months, commonly with full resolution. Temporary management consists of patching one eye, using prisms to relieve any discomfort caused by the diplopia or by injecting Botox into the muscle. If the diplopia does not resolve, permanent prisms are incorporated into the patient’s spectacles or repeat Botox injections are required. If the residual diplopia is severe, eye muscle surgery may be necessary to straighten the eyes.
Anyone who experiences double vision should be seen by an ophthalmologist immediately or attend eye emergency at the hospital, to exclude any other causes of diplopia.
Ms Celine Anne Pace