Tunnel Vision,What Causes It and When Is It Serious?

Tunnel vision describes the loss of peripheral (side) vision while central vision remains intact,creating the visual experience of looking through a tunnel or narrow tube. It is one of the most significant and potentially serious symptoms in optometry, because the conditions that cause it range from chronic and progressive (requiring monitoring and management) to acute and emergency (requiring same-day or emergency treatment).

Glaucoma,the Most Common Cause

Primary open-angle glaucoma,the most common form of glaucoma,causes progressive peripheral visual field loss over years. Because the loss is gradual and peripheral, patients often do not notice it until a significant portion of peripheral vision has been destroyed. By the time tunnel vision is apparent to the patient, glaucoma is at an advanced stage. This is why annual screening is essential for high-risk individuals,to detect field loss before it is noticeable.

Glaucoma causes peripheral field loss by damaging the retinal nerve fibre layer,the axons of the retinal ganglion cells that carry visual information from the peripheral retina to the optic nerve. Once these nerve fibres are lost, the visual field defect is permanent. Early detection preserves remaining nerve tissue; late detection leaves little to preserve.

Retinitis Pigmentosa

A group of hereditary retinal dystrophies characterised by progressive degeneration of the peripheral photoreceptors. Symptoms typically begin in the teens or twenties with night vision difficulty, progressing to tunnel vision over decades. There is currently no cure but ongoing research into gene therapy is promising.

Retinal Detachment

A retinal detachment produces a shadow or curtain across part of the visual field,often initially peripheral. This is an acute emergency. Sudden new floaters, flashes of light, and then a progressive shadow or curtain (typically from the periphery moving toward centre) are the classic warning signs. Call triple zero or go immediately to Westmead Emergency.

Neurological Causes

• Pituitary adenoma: A tumour pressing on the optic chiasm produces a characteristic bitemporal visual field defect,loss of the outer visual fields in both eyes simultaneously.
• Occipital lobe stroke: A stroke affecting the visual cortex produces a hemianopia,loss of one half of the visual field in both eyes.
• Severe migraine: Visual aura including temporary field loss,always resolves completely within an hour.