Optic nerve drusen: what they are, how they are found and whether they affect sight

The optic nerve carries visual information from the retina at the back of the eye to the brain. Where it enters the eye it forms the optic disc, also called the optic nerve head. A leaflet from Hull University Teaching Hospitals describes optic nerve head drusen as abnormal deposits of protein and calcium in the optic nerve head, which can lie on the surface or be buried beneath it. A Sheffield Children's NHS Foundation Trust leaflet describes them as tiny, non-harmful lumps that can make the optic disc look elevated or distorted, with blurry and irregular edges.

The word drusen is also used for deposits under the retina in age-related macular degeneration, but optic nerve drusen are a different condition affecting a different structure.

The Cambridge University Hospitals leaflet estimates that optic nerve drusen occur in about 1 to 2 people per 100 of the population, and notes that many cases are never diagnosed because most people have no vision problems. The Hull leaflet gives about 1 percent. They usually occur in both eyes but can be present in only one.

The tendency to form drusen is present from birth, but the deposits become visible only after several years. The Hull leaflet notes they usually do not show in children younger than 4, and the Cambridge leaflet that they usually become visible after the age of 10 though sometimes earlier. The exact cause is unknown; they can be inherited as a family trait, and the Hull leaflet advises that people diagnosed may wish to discuss it with close relatives so that they can have screening.

Most people have no symptoms. The Cambridge leaflet says drusen do not usually affect central vision or colour vision but can affect peripheral vision in some people, usually very gradually, and that some patients lose peripheral vision over time without noticing it, so it is picked up on formal testing. The prognosis for central vision is good.

The Hull leaflet adds that in some cases drusen can cause vision problems such as peripheral or central vision loss, and that people with drusen have a slightly increased risk of other eye conditions including retinal vascular occlusion and non-arteritic anterior ischaemic optic neuropathy (NAION). These are uncommon, but they are the reason sudden change should never be ignored.

Drusen are usually diagnosed during a routine eye exam, when the eye doctor looks at the back of the eye. Sheffield Children's leaflet says that the condition is often diagnosed at the first ophthalmology visit, and that confirmation may need ocular ultrasound (a B-scan through the closed eyelid), optical coherence tomography (OCT) and sometimes fluorescein angiography, which uses a dye to image the blood vessels. Buried drusen may be hard to see and ultrasound can show the calcium within them.

The Cambridge leaflet describes the usual assessment in children: measuring vision, a Humphrey visual field test to check peripheral vision, an examination with dilated pupils and photographs of the optic nerve including auto-fluorescence images and OCT.

The Sheffield leaflet stresses that drusen may be confused with papilloedema, which may be a sign of pressure inside the head and requires more thorough investigation, and that drusen can be hard to diagnose at a high street optician, so it is important to tell your optician about the diagnosis. Hull advises seeing your eye doctor to confirm the diagnosis and rule out other conditions with a similar appearance.

The Hull leaflet says that once drusen are confirmed there is no proven way to treat them or prevent them increasing in size, and the Cambridge leaflet says optic nerve drusen is not a treatable condition, though eye drops are prescribed if the pressure inside the eye is raised. The Sheffield leaflet says vision is very rarely affected and so does not need treatment, although photographs are often taken to document findings.

Follow-up is usually with a community optometrist or optician, who can repeat visual field tests periodically. The Cambridge leaflet notes that children are typically discharged to the care of the optician. Adults who are newly diagnosed should ask how often field tests are advised and make sure the diagnosis is on their record so that future swelling or pressure checks are interpreted correctly.

Sudden loss or blurring of vision, a dark curtain or shadow across your vision, new flashes or floaters, pain with eye movement or a sudden severe headache should be treated as urgent regardless of any known drusen. Contact an eye casualty, NHS 111 or an urgent optician appointment the same day, and call 999 or go to A&E if there are other neurological symptoms such as weakness or confusion. The NHS says new floaters or flashes, a dark curtain or sudden change in vision are reasons to seek urgent advice from an optician or NHS 111.

Most people live with drusen without any change in their lives. Regular eye tests are sensible. Tell any eye professional about your diagnosis, because, as the Sheffield leaflet explains, drusen can be difficult to diagnose at an optician and may be mistaken for swelling of the nerve. Driving, work and sport are not usually restricted unless the visual field is affected; if you are told your field is reduced, discuss driving standards with your clinician.

Drusen are often first spotted by a community optometrist, who refers to hospital eye services if the appearance is uncertain or swelling is suspected. Private ophthalmology can provide OCT and ultrasound quickly. In either setting, make sure a written summary of the diagnosis is kept, because it prevents repeat investigations for suspected raised intracranial pressure.