Sudden, painless vision loss as a sign of an ophthalmic emergency

Sudden and painless loss of vision is an alarming situation that may be the first sign of a serious eye condition requiring urgent medical attention.

Unlike other eye problems that cause discomfort, redness or pain, a sudden decrease in vision without other associated symptoms may be due to potentially serious retinal, vascular or optic nerve disorders.

At the Barraquer Ophthalmology Centre, we recommend an immediate ophthalmological assessment in the event of any sudden visual change, even if there is no eye pain.

What is considered sudden, painless vision loss?

Sudden, painless vision loss is considered to be a decrease in vision that appears within minutes or hours, affects one or both eyes and is not accompanied by significant eye pain.

It may present as:

• Partial darkening of the visual field.
• A “curtain” sensation.
• Severe blurred vision.
• A central black spot.
• Complete loss of vision.

Retinal detachment

A retinal detachment occurs when the retina separates from the underlying layer that nourishes it (the retinal pigment epithelium).

Warning signs

• Sudden onset or a significant increase in floaters.
• Flashes of light.
• A shadow or progressive loss of part of the visual field.

When the detachment progresses and affects the macula, vision loss may be severe and rapid.

Retinal detachment is a surgical emergency. The visual prognosis depends, to a large extent, on how quickly treatment is provided.

Retinal artery occlusion

Occlusion of the central retinal artery or one of its branches is one of the most serious causes.

It occurs due to a sudden interruption of arterial blood flow to the retina and is considered the ocular equivalent of a stroke.

Characteristics

• Sudden and usually unilateral vision loss.
• Absence of eye pain.

In addition to urgent ophthalmological assessment, a cardiovascular and neurological evaluation is usually required to identify possible associated risk factors.

Retinal vein occlusion

Occlusion of the central retinal vein or one of its branches causes impaired venous drainage, resulting in vascular congestion and retinal haemorrhages.

Risk factors

• High blood pressure.
• Diabetes mellitus.
• Dyslipidaemia.
• Glaucoma.

The degree of visual impairment varies and may range from a mild decrease in vision to significant vision loss.

Vitreous haemorrhage

This occurs when bleeding develops within the vitreous humour.

Patients usually describe:

• Sudden onset of dark spots.
• A reddish cloud in the visual field.
• Sudden decrease in vision.

The most common causes include:

• Diabetic retinopathy.
• Retinal tears.
• Eye trauma.
• Retinal vascular occlusions.

Ischaemic optic neuropathy

This occurs due to impaired blood supply to the optic nerve.

Common manifestations include:

• Sudden, painless vision loss.
• Visual field defects.
• It is more common in older people with cardiovascular risk factors.

In some cases, it may be associated with giant cell arteritis, an inflammatory disease that requires urgent treatment to prevent irreversible visual damage.

Why do these conditions not cause pain?

Many of the conditions that cause sudden vision loss mainly affect the retina, optic nerve or blood vessels. These structures do not have pain receptors to the same extent as other parts of the eye, such as the cornea or conjunctiva. As a result, they may cause significant vision loss without producing substantial discomfort.

The absence of pain should not be interpreted as a sign that the condition is less serious.

What should you do in the event of sudden vision loss?

In the event of any sudden decrease in vision, it is advisable to:

1. Seek urgent ophthalmological care.
2. Not wait for the condition to improve spontaneously.
3. Not self-medicate.

In some retinal and vascular diseases, the speed of intervention can have a direct impact on the visual prognosis.

At the Barraquer Ophthalmology Centre, we have an ophthalmic emergency service that is open at all times and equipped to assess any episode of acute vision loss immediately.

Common diagnostic tests

• Complete examination of the fundus.
• OCT (optical coherence tomography).
• Ocular ultrasound.
• Retinal angiography.
• Visual field testing.

Early diagnosis makes it possible to begin the most appropriate treatment as quickly as possible.

Sudden, painless vision loss is a symptom that should never be ignored. It may be the initial manifestation of a potentially serious retinal or vascular condition.

In the event of any sudden change in vision, an urgent ophthalmological assessment is essential to identify the cause and, whenever possible, preserve visual function.

Dr Maria José Capella, ophthalmologist at the Barraquer Ophthalmology Centre