Oliver Backhouse, Consultant Eye Surgeon www.cataract.org.uk
There are many differing causes of ‘white dot’ inflammation in the eye. Often they have no readily identifiable cause but a name is still given to the problem as it can help better explain the prognosis. The eye can only respond to a problem in a certain manner so various differing causes of the inflammation may all look the same when the eyes are examined. All are relatively rare but some of the more frequently diagnosed ‘white dot syndromes’ are explained below.
They all can have feature of each other but the main differential diagnosis of these conditions are: AMPPE, Sarcoidosis, Birdshot retinochoroidopathy, Multiple evanescent white dot syndrome (MEWDS), Serpiginous choroiditis, Punctate Inner Choroidopathy (PIC), Multifocal choroiditis and Panuveitis (MCP), Tuberculosis and Presumed ocular histoplasmosis syndrome (POHS).
AMPPE mainly occurs in males or females aged 20–40 years. There appears to be no particular race involved. Patients complain of a rapid loss of vision in one eye with the second eye becoming affected within a week of the first eye. Some 20-50% of patients report a preceding viral like illnesses. Examination of the eyes shows multiple yellow-white spots under the retina. After a few weeks they begin to fade leaving behind some pigment scarring. As the spots fade vision begins to return to a level of 6/9 which is driving vision.
We now understand that the cause of the problem lies in the deep blood vessel layer of the eye called the choroid. For this reason AMPPE is now referred to as an Acute Multifocal Ischaemic Choroidopathy. As it can be associated with a skin rash on the legs (erythema nodosum) and rarely with inflammation of the blood vessels of the brain, the underlying process is felt to be a vasculitis of the Choroid (blood vessel inflammation). There is a slight genetic link with HLA B7 and DR2 that may help explain why some people and not others get AMPPE.
Fluorescein angiography can help obtain the diagnosis as well as Indocyanine green angiography (ICG) that shows the choroidal blood vessels in even more detail. The main differential diagnosis in AMPPE is of a) Sarcoidosis: May have raised serum ACE and an abnormal chest X-ray; b) Birdshot: Both eyes affected but of gradual onset, mostly female, greater amount of inflammation in the eye and associated with genetic type HLA A29; c) MEWDS: Usually visual loss in one eye.
Most uveitis specialists would not treat AMPPE unless it is affecting the fovea which is the central part of the macular that sees fine detail. Steroid medication is the treatment of choice if needed.
Serpiginous choroiditis is rare and typically affects patients in their 40s (age 20-70). It presents with unilateral or bilateral painless visual loss with occasional blind spots and distortion of vision. The inflammation is chronic and progressive with periods of activity and then quiescence. Gray-white lesions are seen at the level of the retinal pigment layer. They may coalesce and radiate out from the optic nerve area. Involvement of the macular is common. Patients may not be aware they have this condition until the macular is involved. Signs of previous inflammation are frequent as areas of scarring are left behind. Fluorescein angiography can help identify subtle activity and so make the decision for treatment easier.
The cause of Serpiginous choroiditis is unknown but conditions such as Tuberculosis can look remarkably similar and need to be excluded. Immune calming medications such as Steroids, Azathioprine and Cyclosporin have been shown to be of some benefit in reducing the activity of Serpiginous Choroiditis that affects the macular region. Unfortunately these medications can have long term side effects such as Kidney damage and there needs to be a careful discussion as to whether the benefits of the medication continues to outweigh the risks. Regular photography of the lesions in the eyes is recommended as progression can be slow and without any symptoms.
MEWDS is a self-limiting inflammatory white dot syndrome which predominately affects females under 30 years of age. It usually only affects one eye and resolves over a few weeks (can take up to 10 weeks). Patients have a painless loss of vision with ‘sparkling lights’ and a blind spot in the outer part of the visual field. A preceding viral like illness is found in 50% of patients with MEWDS.
The spots in the eye are subtle and easily overlooked. Fluorescein angiography can help get the diagnosis of MEWDS by revealing characteristic multiple ‘wreaths’ of these inflammatory spots that show up early on. The fovea has a granular appearance and in addition the optic disc may be swollen. Electrical testing of the retinal function reveals photoreceptor dysfunction in 80%. These abnormalities get better with resolution of the disease. No treatment is given as the almost all regain good vision. Uncommonly it can recur or be followed by an Acute Zonal Occult Outer Retinopathy (AZOOR).
MCP is the most common of the white dot syndromes. It mostly affects myopic females aged 20-60. Symptoms are of an acute onset of blurred vision (both eyes in 75%), sparkling lights and the appearances of blind spots in the visual field. Multiple yellow-grey spots are seen in the eye and they can be in their hundreds and of variable sizes. They are mainly located in the midperiphery of the eye. Old lesions become ‘punched-out’ scars with surrounding pigmentation. The optic disc is occasionally swollen but more often is surrounded with scarring. Inflammation of the vitreous (the jelly of the eye) is more prominent and the macular can be affected with inflammatory fluid or abnormal blood vessel formation that can further reduce central vision.
The diagnosis is based on clinical examination. The main differential diagnoses are a) POHS which has similar findings but the number of spots are less and smaller and does not have such vitreous activity; b) Sarcoidosis; c) Birdshot retinochoroidopathy.
MCP is a chronic condition so immune calming medication is recommended should some inflammatory activity persist. Approximately 70% of patients retain driving vision. Punctate Inner Choroidopathy (PIC) is a related disorder (possibly a mild form of MCP) that affects young myopic females. It presents with an acute bilateral loss of vision, and similar sparkling lights and blind spots. However, PIC lesions are smaller and there is no vitreous activity. PIC recurrences are uncommon but like MCP abnormal blood vessels can occur at the macular which spoil central vision. Like MCP most keep good driving vision.
Birdshot retinochoroidopathy typically affects females in their 40-60s. Patients present with a painless gradual blurring of vision in both eyes, sparkling lights, floaters, and later difficulty seeing at night with a loss of colour vision. More than 90% of patients with birdshot chorioretinopathy have a genetic make up of HLA-A29 positive (only 10% of the population are A29 positive).
Examination of the eyes shows multiple yellow-white patches scattered throughout (like the gun scatter of birdshot). They characteristically radiate from the optic nerve and follow the larger choroidal blood vessels. Vitreous inflammation, optic disc swelling, and macular oedema may also be present. The cause is unknown. Diagnosis is made by clinical examination, Fluorescein angiography, and genetic HLA-A29 testing. Steroids and steroid sparing agents such as Azathioprine are the treatments advised to reduce the inflammatory reaction that runs a chronic course. Electrical testing of retinal function is helpful in monitoring the response to treatment.
POHS can affect males and females equally. Often the condition gives no symptoms until it affects the macular where visual acuity loss and a central blind spot develops in the visual field. The cause is really unknown but because it looks so similar to ocular histoplasmosis from the endemic areas of Ohio and Mississippi River Valley region it is called presumed ocular histoplasmosis syndrome.
There is little inflammation to see in the eye but around the optic nerve is characteristic atrophy, a few chorioretinal scarred lesions, and as a late complication, abnormal blood vessels can occur at the macular. This macular problem is the main cause of visual loss. Should the patient experience further disturbed central vision it is always wise to be seen by an Ophthalmologist as soon as is possible incase the abnormal blood vessels are able to be treated.