Overview 

Losing your vision, to whatever degree, can be frightening. Disorders such as papillitis, which can cause sudden changes in your vision, can cause uncertainty, confusion, and be frightening, especially if you don't fully understand what is going on. There are many different conditions that affect vision, and many of which are very similar to papilledema and involve changes to the optic nerve.

In this article, we will explore what papillitis is and how it is similar to other optic nerve disorders. Understanding the similarities between these disorders and also knowing how they are distinct and what sets them apart helps doctors to give accurate diagnoses. I hope this article will explain well to you the different optic nerve disorders and what they mean, providing clarity on the different optic nerve disorders and helping individuals feel more in control of what’s going on and receive and take the necessary steps to manage the condition with the right support.

Introduction 

Papillitis is a type of optic neuritis and is most commonly linked to an autoimmune disease or infectious disease. It can often be confused with other disorders affecting the optic disc, most notably retrobulbar optic neuritis, papilledema and ischemic optic neuropathy (ION). 

Distinguishing papillitis from other optic nerve conditions is essential for providing individuals with the correct treatment and management for papillitis itself and any underlying condition that may be present.¹

What is the optic nerve?

The optic nerve is actually a set of nerves; you have one for each eye, and they connect the eyes to the brain. It’s like a cable that carries information from your eyes to your brain so that your brain can form images from the light signals we capture with our eyes. The optic nerve sends these signals to certain areas of the brain, most notably the visual cortex, responsible for forming images by making sense of shapes, colours and movements. It also sends signals to areas such as the midbrain, which controls reflexes, and the SCN (suprachiasmatic nucleus), which controls the regulation of the body’s internal clock, your sleep-wake cycle. So the optic nerve is essential in many ways for carrying important information to different areas of the brain.²

Problems can occur at different points along the path of the optic nerve, and depending on where the problem occurs, we can see differences in symptoms and test results, which may help us to distinguish between different optic nerve disorders. 

Papillitis and other optic nerve disorders generally affect the head of the optic nerve, which is why they can present similarly, and this is why it's important to carefully examine what is going on to make an accurate diagnosis. Understanding these differences helps make the correct diagnosis and guide correct treatment.²

What is papillitis? 

Papilledema is a condition where we see inflammation and deterioration of the optic disc, the portion of the optic nerve that sits inside the eye. Because of the positioning of the optic disc, we can often see that the disc appears inflamed and swollen. The optic disc is also known as the blind spot, is the section at the back of the eye where the optic nerve joins the retina.

Papilledema is not the same for everybody; some individuals may experience slight visual perception loss, while others may experience more severe vision loss. This is dependent on the extent of the swelling of the optic disc. A key characteristic of papillitis is loss of colour perception, most notably a reduction in red colour perception. 

As papillitis can progress quickly, often within a couple of hours, it is important to achieve an accurate diagnosis and determine the underlying cause.^3,4

Causes of papillitis

Papillitis is usually caused by several underlying conditions.⁴

• Demyelinating conditions such as multiple sclerosis and encephalomyelitis
• Infections such as polio, measles, pneumonia and meningitis
• Metabolic disorders such as diabetes and hyperthyroidism 

Papillitis can also be idiopathic, so it occurs without a clear cause.

Signs and symptoms of papillitis

Common signs and symptoms include:⁴

• Loss of vision: severe and sudden, and also often unilateral, so one eye is affected
• Changes in colour vision: reduced colour perception, we typically see red desaturation, which is a loss of contrast and brightness of the colour red
• Eye pain: discomfort and tenderness with movement of the eye, due to the inflamed optic nerve being pulled by muscles that control eye movement 

Signs doctors may look for through specialised tests:⁴

• Changes in the pupil: the affected eye may not respond normally to light, and the pupillary reflexes may be diminished. This is due to the conduction of impulses through the optic nerve being delayed due to demyelination. This is referred to as the afferent pupillary defect, and it is tested by shining a light into the eye
• Appearance of media of the eye: The vitreous is the clear jelly-like substance in your eye; inflammation from the optic disc can spread and cause this clear substance to become cloudy⁵
• Visual field loss: Individuals may develop a centrocecal scotoma, which is a loss of vision between the blind spot and the fixation point. Under examination, this can have a distinct shape
• Imaging scans: CT and MRI scans show demyelination, a classic hallmark of multiple sclerosis
• Electrophysiology tests: A Visual Evoked Potential (VEP) test measures how well the optic nerve transmits signals to the brain. In papilledema, often due to demyelination and damage to the optic nerve, we see a decrease in the transmission of signals along the optic nerve⁴

Other optic nerve disorders

Retrobulbar neuritis

Retrobulbar neuritis, like papillitis, is a type of optic neuritis also often caused by autoimmune and inflammatory conditions. Retrobulbar neuritis is characterised by the swelling of the optic nerve behind the eye, and causes similar symptoms such as eye pain, decreased visual acuity, visual field defects (gaps in your vision) and colour vision loss.⁴

Upon examination of the eye, the optic disc will appear normal as the swelling of the optic nerve is not visible; other tests, such as MRI scans, VEP studies and visual field tests, can help a doctor to confirm a diagnosis of retrobulbar neuritis.⁶

Papilledema

Papilledema is the swelling of both optic discs caused by an increase in intracranial pressure. This just means there is an increase in pressure in the skull. The space in between the skull and the brain is filled with cerebrospinal fluid (CSF). This fluid also surrounds the optic nerve, so when pressure increases around the brain, it also increases around the optic nerve. This pressure disrupts the normal flow of blood and leads to swelling of the optic discs.⁷

Signs and symptoms of papilledema

Common symptoms of papilledema are well-documented in the literature:⁷

• Usually associated with severe headache and vomiting due to increased pressure within the skull
• Bilateral, both eyes are usually affected 
• In the early stage of papilledema, vision is not affected
• The first signs which affect vision are normally an enlarged blind spot and blurred vision
• In more severe cases, individuals can experience vision loss

Signs a healthcare professional will look for through specialised tests:⁷

• Swollen optic disc: A doctor can observe the back of the eye with a special lens and light (direct ophthalmoscopy), and observe a larger disc swelling
• Haemorrhages around the optic nerve, as the increased pressure causes blood vessels to burst⁸
• Enlarged blind spot: A visual field test will reveal an abnormally enlarged blind spot
• Brain imaging scans: CT and MRI can help doctors look for signs of increased pressure in the brain, and they can also rule out other possible causes of increased pressure in the brain such as tumours or blood clots

Ischemic optic neuropathy

Ischemic Optic Neuropathy (ION) is a sudden loss of vision caused by a decreased blood flow to the optic nerve rather than inflammation. This loss of blood flow to the optic nerve, often due to a blockage in the blood vessels, leads to damage of the optic nerve through cell death. ION is classified as either Anterior ischemic optic neuropathy (AION), where we can observe swelling of the optic disc, and Posterior ischemic optic neuropathy (PION), where there is no swelling of the optic disc as the damage is happening further back along the nerve.⁹

ION can either be arteritic (AION), caused by the inflammation of arteries and blood vessels, often due to autoimmune conditions, or non-arteritic (NAION) and caused by a blockage in blood flow.⁹

Arteritic ION is usually caused by other inflammatory conditions and therefore is often associated with other symptoms such as headaches, muscle pain that increases with chewing, weight loss, fatigue and malaise (general feeling of being unwell). 

If left untreated, ION can result in permanent vision loss. Arteritic ION is treated with anti-inflammatory corticosteroid medications, which prevent further ischemia and can protect the other eye from ION. NAION cannot be treated with anti-inflammatory drugs, and treatment is focused on managing underlying conditions such as high blood pressure, type 2 diabetes, atherosclerosis and smoking. As NAION usually affects one eye first, managing these underlying conditions can help you to lower your risk of developing NAION in both eyes.¹⁰

An eye examination in an individual with ION can show a pale, swollen optic disc, which is distinct from the swollen and inflamed optic disc we typically see in papilltis.¹⁰

Summary

Problems affecting your vision can be alarming, especially when they can be as a result of another underlying health problem or when the cause isn’t immediately clear. Papillitis is one of several conditions affecting the optic nerve, and it can be confusing and overwhelming trying to distinguish between them. Increasing awareness and understanding how these conditions differ can help you feel more informed and reassured, and give doctors the information they need to make the right diagnosis and guide treatment to protect your vision and health.