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Diagnosis of PIC can be difficult because the appearance may be similar to other conditions and types of posterior uveitis, especially other forms of the so called white dot syndromes. The diagnosis is made by eliminating all the other possibilities by careful examination by an experienced ophthalmologist, aided with visual field testing and Fluorescein angiography (an intra-venous dye used to show the blood vessels at the back of the eye).
It is important that the correct diagnosis is made because treatment may be quite different for apparently similar conditions.
What happens with PIC depends a lot on the presence or absence of an important complication, Choroidal neovascularization (known as CNV).
Often, the inflammation in PIC is self limiting, not always requiring treatment.
However treatment is advised if there are many active or central lesions, or if there are signs of CNV.
One cause of the White Dot Syndromes as suggested by Gass involves viral or infectious agents. Specifically pertaining to the ‘AZOOR complex,’ Gass has postulated that a virus may enter the retina at the optic head and the infection may spread from one photoreceptor to another. Some unexplained features include the development of more than one disease in the same patient and the majority of cases occurring in females.
According to Becker’s common genetic hypothesis, “unlike mendelian genetic disorders, common autoimmune and inflammatory diseases arise from combinatorial interactions of common non-disease specific loci, disease specific loci, and specific environmental triggers.” An important aspect of this hypothesis pertains to the existence of common non-disease genes that predispose patients to autoimmune diseases. Jampol and Becker insinuate that ‘common susceptibility genes’ are present in patients affected by white dot syndromes. The presence of environmental triggers, such as viral infections, immunizations, and stress, and interactions with other genes contribute to the development of the white dot syndromes. Additionally, Jampol and Becker hypothesize that the predisposing genetic loci can be identified.
Gass points to a lack of evidence in support of the Becker theory. Instead, Gass highlights that although evidence indicates that patients with AZOOR have a greater chance of developing autoimmune diseases, this does not mean that the AZOOR complex of disorders are themselves autoimmune diseases. This is supported by the difficulty in detecting “retinal autoantibodies” in AZOOR patients.
Two other diseases which also present with white dots on the fundus are retinitis punctata albescens and fundus albipunctatus. These diseases are not white dot syndromes, but have much more defined etiology. Retinitis punctata albescens is caused by mutations in RLBP1, the gene for retinaldehyde binding protein 1. In comparison, fundus albipunctatus is caused by mutations in RDH5 gene for an 11-cis-RDH in RPE cells.
Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) primarily occurs in adults (with a mean age of 27). Symptoms include blurred vision in both eyes, but the onset may occur at a different time in each eye. There are yellow-white placoid lesions in the posterior pole at the level of the RPE. Some suggest a genetic predisposition to the disease, while others postulate an abnormal immune response to a virus.
Photopsia is the presence of perceived flashes of light. It is most commonly associated with posterior vitreous detachment, migraine with aura, migraine aura without headache, retinal break or detachment, occipital lobe infarction, and sensory deprivation (ophthalmo"pathic" hallucinations). Vitreous shrinkage or liquefaction, which are the most common causes of photopsia, cause a pull in vitreoretinal attachments, irritating the retina and causing it to discharge electrical impulses. These impulses are interpreted by the brain as 'flashes'.
This condition has also been identified as a common initial symptom of Punctate inner choroiditis (PIC), a rare retinal autoimmune disease believed to be caused by the immune system mistakenly attacking and destroying the retina. During pregnancy, new-onset photopsia is concerning for severe preeclampsia.
Photopsia can present as retinal detachment when examined by an optometrist or ophthalmologist. However, it can also be a sign of Uveal melanoma. This condition is extremely rare (5–7 per 1 million people will be affected, typically fair-skinned, blue-eyed northern Europeans). Photopsia should be investigated immediately.