Optic neuritis (inflammation of the optic nerve) is often the first symptom of multiple sclerosis and thus the start of targeted diagnostics and often also the starting point of a specific immunotherapy. Therefore, it is surprising that there have been no general diagnostic or classification criteria for optic neuritis so far. This gap has now been closed by a recent study published in the science magazine THE LANCET. To establish the diagnostic criteria, a group of 101 international experts came together. Neurologists, neuroradiologists and (neuro)ophthalmologists (= ophthalmologists specializing in nerve diseases of the eye) developed new diagnostic criteria for optic neuritis between April 2020 and May 2021 in a so-called validated Delphi process. The Delphi process (named after the “Oracle of Delphi”) is a systematic, multi-stage survey method with feedback, in which a group of experts assesses theses on a consultation topic in several rounds of questions. The method is considered a proven means of finding a consensus independently of the influence of individual people. The results now published by the group of experts are of interest to MS patients, so I would like to briefly summarize them.
Clinical and paraclinical diagnostic criteria
The diagnosis of optic neuritis should be based on clinical findings and paraclinical findings. The clinical criteria include: (A) unilateral, subacute visual loss with pain in the orbit, which intensifies with eye movements (orbital motion pain) with color desaturation and reduced contrast perception (B) painless visual loss in which all the criteria mentioned under (A) occur except for orbital motion pain and (C) bilateral visual loss, in which all criteria listed under (A) or (B) apply.
Paraclinical criteria are understood to mean the results of technical additional examinations. These include 1) Optical coherence tomography (OCT) – a laser scan of the back of the eye, with which the thickness of the different retinal layers can be measured. However, this method is not yet widely available at ophthalmologists or neurologists/neurological clinics. 2) Magnetic resonance imaging (MRI) – here, either the acute contrast enhancement of the symptomatic optic nerve or a signal increase of the nerve visible in the course is of diagnostic importance. 3) Biomarkers such as the detection of autoantibodies (e.g. against aquaporin-4 or MOG) or the detection of oligoclonal bands in the cerebrospinal fluid.
The combination of the above clinical and paraclinical criteria then allows the diagnosis of either definite or possible optic neuritis. Definite optic neuritis can be assumed if the clinical criteria for (A) are met and one of the above paraclinical tests has produced a corresponding result; if there is painless visual loss (B), then two positive paraclinical tests are required; in the case of bilateral visual loss (C), two positive paraclinical tests must also be present, but one of them must be an MRI finding.
Possible optic neuritis can be assumed if the clinical criteria (A), (B) or (C) are present in the acute situation, but there are (yet) no paraclinical tests that support this assumption. In the case of positive paraclinical findings and anamnestic indications of a past optic nerve inflammation, a possible optic neuritis can also be assumed.
I understand if you found this to be cumbersome and perhaps even confusing when reading. On the other hand, precise diagnostic criteria are of great importance for the classification of a visual disorder. The authors rightly emphasize that it can be assumed that more than 60 diseases can be the cause of optic neuritis. Not all of these are diseases that are chronic and require long-term immunotherapy. Therefore, the authors also suggest a distinction into different subtypes, with a classification into autoimmune (usually relapsing or recurrent) and systemic (usually one-time) optic neuritides (ON) being agreed upon. The autoimmune optic neuritides (ON) naturally include optic neuritis in MS or optic neuritis in the context of neuromyelitis optica (NMO) with antibodies against aquaporin-4. But also rarer forms of chronic optic nerve inflammations that respond well to cortisone. With regard to the optic nerve inflammations that occur in the context of systemic diseases, the publication mentions post-infectious inflammations among others and gives a detailed overview of a large number of systemic diseases in which the optic nerve can be involved.
The work discussed here is of scientific importance because it creates more clarity and is important for future (drug) studies.
