Editing Optic neuritis (section)

== Diagnostics ==
The [[World Health Organization]]'s [[ICD-11]] classification includes optic neuritis.<ref name="auto122"/> However a 2022 review found that there is no consensus regarding the classification of optic neuritis, and precise diagnostic criteria are not available.<ref>{{Cite journal |title=Diagnosis and classification of optic neuritis - The Lancet Neurology |date=2022 |pmid=36179757 |url=https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(22)00200-9/abstract#%20 |journal=The Lancet. Neurology |volume=21 |issue=12 |pages=1120–1134 |doi=10.1016/S1474-4422(22)00200-9 |display-authors=1 | vauthors = Petzold A, Fraser CL, Abegg M, Alroughani R, Alshowaeir D, Alvarenga R, Andris C, Asgari N, Barnett Y, Battistella R, Behbehani R, Berger T, Bikbov MM, Biotti D, Biousse V, Boschi A, Brazdil M, Brezhnev A, Calabresi PA, Cordonnier M, Costello F, Cruz FM, Cunha LP, Daoudi S, Deschamps R, De Seze J, Diem R, Etemadifar M, Flores-Rivera J, Fonseca P }}</ref> In practice, optic neuritis is diagnosed by a combination of features pertaining to symptom manifestation, clinical evaluation, and imaging findings.

=== Clinical Evaluation ===
A trained healthcare provider may evaluate a patient for optic neuritis by identifying the presence and degree of visual acuity loss, visual field loss, color vision deficits, and an [[Relative afferent pupillary defect|afferent pupillary defect]] in the affected eye.<ref name=":35"/> The presence, absence, or degree of these manifestations may have associations with specific underlying etiologies of optic neuritis, but are often insufficient to definitively establish a diagnosis of optic neuritis and its associated cause.

Fundoscopy is another modality of clinical evaluation that is performed with an [[Ophthalmoscopy|ophthalmoscope]]. Findings that support a diagnosis of optic neuritis include optic disc edema, disc inflammation, disc hemorrhages, or ocular inflammation.<ref name=":35"/> However, these findings are not always present in every patient, such as in patients with idiopathic optic neuritis which often have normal fundoscopic findings.

=== MRI ===
[[Magnetic resonance imaging]] (MRI) is a robust and sensitive diagnostic modality for the detection of optic neuritis. Imaging of the optic nerve with MRI shows increased signal on the affected side. There is contrast enhancement of the symptomatic optic nerve and sheaths acutely or intrinsic signal increase (looking brighter) within ≥ 3 months. One study found that MRI of the orbits with fat suppression and gadolinium enhancement detected acute optic neuritis lesions in 95% of affected individuals within 20 days of vision loss.<ref>{{Cite journal |last1=Kupersmith |first1=Mark J. |last2=Alban |first2=Therese |last3=Zeiffer |first3=Barbara |last4=Lefton |first4=Daniel |date=April 2002 |title=Contrast-enhanced MRI in acute optic neuritis: relationship to visual performance |url=https://pubmed.ncbi.nlm.nih.gov/11912114 |journal=Brain: A Journal of Neurology |volume=125 |issue=Pt 4 |pages=812–822 |doi=10.1093/brain/awf087 |issn=0006-8950 |pmid=11912114}}</ref> Another study found that T2-weighted images with fat suppression and short tau inversion recovery (STIR) detected lesions in up to 89% of acute optic neuritis cases with abnormalities persisting for as long as 6 weeks in 92% of cases.<ref>{{Cite journal |last1=Miller |first1=D. H. |last2=Newton |first2=M. R. |last3=van der Poel |first3=J. C. |last4=du Boulay |first4=E. P. |last5=Halliday |first5=A. M. |last6=Kendall |first6=B. E. |last7=Johnson |first7=G. |last8=MacManus |first8=D. G. |last9=Moseley |first9=I. F. |last10=McDonald |first10=W. I. |date=February 1988 |title=Magnetic resonance imaging of the optic nerve in optic neuritis |url=https://pubmed.ncbi.nlm.nih.gov/3340276 |journal=Neurology |volume=38 |issue=2 |pages=175–179 |doi=10.1212/wnl.38.2.175 |issn=0028-3878 |pmid=3340276}}</ref>
 
[[File:Case-3-mri.png|thumb|Magnetic Resonnance Imaging (MRI) during an episode of optic neuritis.]]

Identification of optic nerve, orbital, brain, and meningeal involvement with MRI can also help to better characterize the underlying cause of optic neuritis upon initial evaluation. Unilateral optic nerve involvement is more common MS while bilateral optic nerve involvement is more common in NMOSD and MOGAD.<ref name=":35"/>  T2-hyperintense and gadolinium-enhancing lesions in multiple regions of the brain and/or spinal cord may be highly suggestive or diagnostic of MS. Such lesions found in the periependymal, fornix, and hypothalamic lesions may be more suggestive of NMOSD.<ref name=":35"/> Involvement of the optic chiasm or optic tract are more suggestive of NMOSD-optic neuritis; involvement of the retrobulbar optic nerve can be seen in both NMOSD and MOGAD, but more commonly in MOGAD; perineural optic nerve involvement is often suggestive of MOGAD-optic neuritis, but should not preclude the investigation of other autoimmune or infectious etiologies.<ref name=":35"/>

=== OCT ===
[[Optical coherence tomography]] (OCT) is a sensitive imaging modality that can reveal subtle pathologic changes in the optic nerve and retina.<ref name=":35"/> OCT may reveal changes in thickness of the retinal nerve fiber layers (RNFL) at the peripapillary retina and macula.<ref name=":35" /> The OCT shows corresponding optic disc swelling acutely or an inter-eye difference in the thickness of the neurons and their nerves connecting the eye with the brain in above 4-5% within ≥ 3 months after onset.<ref name="Petzold_20222"/>

New advancements in OCT technology have allowed for the development of OCT [[angiography]] which can provide information on the thickness of retinal blood vessels. Whereas OCT has yet to demonstrate identifiable correlations between acute RNFL changes and visual outcomes or treatment responses, OCT angiography may offer novel diagnostic and prognostic insight.

=== VEP ===
[[Evoked potential|Visual evoked potential]] (VEP) is a sensitive test that measures the P100 latency of axonal transmission along the optic nerve. The P100 latency typically peaks at 100 milliseconds after visual stimulus presentation, and a prolonged P100 latency suggests abnormal conduction along this pathway which confirms the presence of optic neuropathy.<ref name=":35" />