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The white-dot syndromes are a distinctive group of disorders producing yellow-white inflammatory lesions affecting the retina, RPE and choroid. A wide range of inflammatory and infectious conditions may also cause white spots. Areas of retinitis are characterised by a cloudy yellow-white appearance with indistinct edges (Figure 1). Choroiditis is deeper, with yellow or greyish patches that are more clearly demarcated (Figure 2). Retinal blood vessels lie over the lesions and inactive lesions form areas of well-defined chorioretinal atrophy.
Posterior uveitis
A complete discussion of the inflammatory and infectious conditions that produce white dots is beyond the scope of this article. Key features indicating one of these serious conditions are the presence of vitritis or anterior uveitis associated with areas of retinitis or choroiditis. Posterior uveitis may be caused by conditions including toxoplasmosis, sarcoidosis, Behçet's, intraocular lymphoma, sympathetic ophthalmia, TB, and syphilis. They may have multiple and atypical presentations, such as the multifocal toxoplasmosis seen in AIDS patients. A medical history may give clues, such as already having one of the systemic conditions. Posterior uveitis needs to be considered in the differential diagnosis of the white-dot syndromes and requires emergency referral.
The 'White-dot syndromes'
These syndromes have many shared features, the majority affecting people under 50 years of age, with the exception of birdshot chorioretinopathy and serpiginous choroiditis, which affect older adults.6 Symptoms include blurred vision, visual field loss (enlargement of blindspot), photopsias, nyctalopia, and floaters. These conditions present significant diagnostic and therapeutic challenges to clinicians. All patients with evidence of inflammatory chorioretinal lesions should be referred urgently or as an emergency, especially if there is uveitis.
- Multiple evanescent white-dot syndrome (MEWDS)
MEWDS is typically unilateral with sudden onset of visual disturbance and the development of multiple small white dots at the level of the outer retina or RPE. There is a good prognosis with most patients achieving normal vision within weeks without the need for treatment.
- Acute posterior multifocal placoid pigment epitheliopathy (APMPPE)
APMPPE is characterised by the rapid onset of blurred vision with mild vitreous cells and bilateral multifocal yellowish-white placoid lesions at the level of the RPE in the posterior pole (Figure 3). These lesions gradually fade to be replaced by RPE atrophy and hyperpigmentation. Most have a good prognosis with spontaneous recovery of vision to 20/40 or better within 3-6 weeks.
- Birdshot choroidopathy
This is characterised by deep yellow-orange choroidal lesions that radiate from the optic nerve, particularly on the nasal side (Figure 2). There is a moderate vitritis and often vasculitis, although patients often present with poor vision and only mild inflammation and few retinal changes. These patients should be referred for diagnosis (HLA A29 typing is almost pathognomonic for this condition) and immunosuppressive treatment.
- Punctate inner choroidopathy (PIC) and multifocal choroiditis with panuveitis syndrome (MFC)
PIC and MFC are similar syndromes in which there are acute yellow-white choroidal lesions beneath the macula (Figure 4). In PIC these are confined to the posterior pole and there is no associated vitritis. MFC has both anterior chamber and vitreous inflammation. The visual prognosis is poor due to scarring and choroidal neovascular membranes and patients require systemic immunosuppressive agents to control the disease.
- Serpiginous choroiditis
Serpiginous choroiditis is a bilateral chronic, progressive inflammatory condition. Grey-white, jigsaw-puzzle shaped lesions occur in the peripapillary and macular region. They clear to leave extensive atrophy of the choriocapillaris, RPE and retina. Subretinal fibrosis and choroidal neovascularisation may also complicate the picture.
Miscellaneous pale lesions
There are a number of conditions that cause areas of pale thickening or thinning of the retina that do not easily fit into any of the main categories discussed in this article. These are not really dots and flecks but still need to be considered in the differential diagnosis. Some will be obvious from pattern recognition, such as cotton-wool spots, but others, such as atrophic changes may represent the end stage of a number of different conditions.
- Cotton-wool spots
These are caused by localised ischaemia following capillary occlusion in the retinal nerve fibre layer. Axoplasmic flow (flow of substances within individual neurons) is interrupted, resulting in cloudy swelling of the nerve fibres (Figure 5). These are commonly seen in ischaemic diabetic retinopathy, hypertension, AIDS, and collagen vascular disorders. These patients need urgent referral for a full cardiovascular work-up and other investigations as necessary.
- Central serous retinopathy
A localised sensory detachment of the macula that is usually clear but can occasionally have small precipitates the fluid may sometimes be turbid, giving a paler appearance (Figure 6). Unfortunate patients who develop chronic problems may develop RPE changes with small atrophic patches at the macula.
- Atrophic patches at the macula
Areas of thinning at the macula may occur in the earlier stages of geographical atrophy (Figure 7) or myopic degeneration, later coalescing to a large area of atrophy. Small discrete areas are also seen after diabetic laser. Atrophy is also a very non-specific end stage change in a number of hereditary and inflammatory conditions discussed here. A careful history will help establish if the changes are part of a recognised condition or if this is a new presentation that needs referral.
Conclusion
White dots and flecks at the macula represent a wide range of conditions. The size, shape, colour, depth and pattern of these lesions will help with the differential diagnosis. Most white dots within the retina are benign and need no treatment. However, when associated with retinovascular disease (diabetes/vein occlusion) they only need routine assessment. When associated with an acute visual loss, posterior uveitis (vitreous cells) or acute neuro-retinitis (with disc swelling) they need urgent referral. Dilation and examination with a Volk lens is the current standard of care for these type of fundal lesions.
Acknowledgements
We would like to thank Professor Lotery and Ann Clover from Southampton Eye unit for their help in obtaining images for this article.
This is a sister paper to the red eye differential diagnosis paper published in Optician, February 29 2008. Christina A Rennie is a specialist registrar, Sam Khandhadia is research registrar and Richard Newsom consultant ophthalmologist, all at the Southampton Eye Unit