Infectious CNS diseases can involve the visual pathway at multiple levels, leading to optical neuritis, uveitis, retinitis, or encephalitis. Bacterial infections, such as tuberculosis, may directly affect the optical nerve, optical chiasm, or occipital lobe. Cat scratch disease caused by Bartonella henselae can result in optical neuropathy and neuroretinitis. Viral infections also pose significant risk; cytomegalovirus (CMV) can cause retinitis, particularly in immunocompromised patients such as those with HIV/AIDS, transplant recipients, or chemotherapy patients, at times leading to blindness. Herpes viruses, including Herpes Simplex Virus (HSV) ( Fig. 1 ) and varicella-zoster virus, can cause acute retinal necrosis and/or cerebritis. Congenital infections, as part of the TORCH complex (Toxoplasmosis, CMV, Rubella, Syphilis, HSV), can produce visual impairment by damaging the developing brain and visual cortex, as well as the retina and choroid. Congenital Zika syndrome (CZS) is associated with microcephaly, cortical malformations, and profound visual deficits. Computed tomography (CT) and MR imaging studies have demonstrated occipital cortical volume loss in 95% of affected infants, even in cases where the ocular examination is normal, highlighting the importance of neuroimaging in identifying cortical visual impairment.

Sequela of HSV encephalitis involving the optical radiations within the right temporal lobe. Axial T2-weighted ( A ), axial FLAIR ( B ), axial postcontrast T1 ( C – D ), and coronal postcontrast T1 showing encephalomalacia ( white arrows ) involving the right temporal lobe, including portions of the optical radiations (Meyer’s Loop) in a patient with sequela of HSV encephalitis. HSV, Herpes Simplex Virus.

Inflammatory disorders frequently target the optical nerve and optical pathway. Multiple sclerosis (MS) ( Fig. 2 ) and neuromyelitis optica spectrum disorder (NMOSD) are prototypical demyelinating diseases that produce optical nerve inflammation and white matter lesions. Myelin oligodendrocyte glycoprotein antibody-associated disease frequently affects vision through acute optical neuritis with prominent inflammatory signs. Visual recovery after high-dose corticosteroids is often favorable, however, relapses are common and can lead to cumulative optical nerve damage and permanent visual impairment. Neurosarcoidosis is characterized by granulomatous lesions that may affect the optical nerves, meninges, or brain parenchyma, at times leading to irreversible visual impairment. Imaging modalities, including contrast-enhanced MR imaging and PET-CT, are critical for detecting inflammatory lesions and monitoring response to therapy.

Multiple sclerosis lesions involving the optical radiations. Axial FLAIR imaging in a patient with long-standing history of multiple sclerosis, including old demyelination lesions involving the optical radiations, with an example on the right noted by a white arrow.

Neoplasms affecting the visual pathway can be primary or secondary and involve structures from the optical nerve to the occipital cortex. Optical nerve gliomas, commonly associated with neurofibromatosis type 1, are slowly growing tumors that can compromise visual function. Pituitary macroadenomas ( Fig. 3 ) and craniopharyngiomas frequently exert mass effect on the optical chiasm, producing bitemporal hemianopia. Meningiomas arising from the dura mater near the optical nerve or chiasm may similarly cause progressive visual loss. Occipital lobe tumors interfere with visual processing and may result in homonymous visual field defects. Lymphomas and brain metastases may infiltrate visual pathway structures, depending on their location, resulting in variable visual symptoms. Additionally, tumors can increase ICP, leading to papilledema and secondary optical nerve damage. Early recognition using MR imaging and CT is vital, as timely intervention may preserve visual function.

Pituitary macroadenoma extending into the suprasellar cistern and exerting mass effect on the inferior aspect of the optical chiasm. Coronal ( A ) and sagittal ( B ) post-contrast T1-weighted imaging showing a heterogeneously enhancing mass lesion contacting and elevating the left aspect of the optical chiasm ( white arrow ).

Vascular disorders are a major cause of vision loss, affecting both the eye and the brain. Local vascular compromise in the retina can result in retinal artery or vein occlusion, ischemic optical neuropathy, or retinopathy secondary to systemic diseases such as diabetes or hypertension. Large vessel occlusions involving the posterior cerebral artery (PCA), which supplies the occipital lobe and visual cortex, can cause homonymous hemianopia or quadrantanopia. The clinical spectrum of vascular injury extends beyond field defects to include visual hallucinations, visual agnosia, neglect, prosopagnosia, and cortical blindness. ^,, Imaging modalities such as diffusion-weighted MR imaging and CT angiography are crucial for identifying ischemic injury and guiding intervention.

Metabolic disorders can disrupt vision through direct effects on the optical nerve, retina, or visual cortex. X-linked adrenoleukodystrophy causes demyelination, predominantly involving the parietal and occipital white matter that frequently compromises visual pathways ( Fig. 4 ). Mitochondrial disorders, such as MELAS and Leigh syndrome, impair energy metabolism, leading to optical neuropathy and cortical visual impairment. Thiamine deficiency, hepatic encephalopathy, and storage diseases, such as Batten disease, may similarly produce vision loss by damaging neuronal tissue, particularly through involvement of the retina, optical nerve, optical radiations, and visual cortex. Systemic metabolic diseases, including diabetes and hypertension, can compromise the vasa nervorum of cranial nerves, resulting in diplopia or other ocular motor deficits. ^, Neuroimaging, including MR spectroscopy, may help identify metabolic abnormalities affecting visual pathways.

Adrenoleukodystrophy involving the optical radiations. Axial ( A ), sagittal ( B ), and coronal ( C ) FLAIR imaging in a case of adrenoleukodystrophy showing extensive involvement of the white matter tracts of the optical radiations.

Neurodegenerative disorders can affect vision through ocular involvement or cortical degeneration. Disorders such as age-related macular degeneration, glaucoma, and retinitis pigmentosa primarily involve the retina or optical nerve, while diseases like Alzheimer’s and Parkinson’s disease affect visual perception and processing through cortical and subcortical degeneration. Posterior cortical atrophy, a variant of Alzheimer’s disease, presents with cortical visual syndrome, including visuospatial and perceptual deficits. The Heidenhain variant of Creutzfeldt–Jakob disease produces rapid cortical blindness. Lewy body dementia is characterized by visual hallucinations and perceptual errors, while Parkinsonian syndromes may cause subtle visuospatial and ocular motor deficits. Neuroimaging, particularly volumetric MR imaging and functional imaging, aids in assessing structural and functional changes underlying visual dysfunction.

Congenital cerebral visual impairment arises from maldevelopment or early damage to visual pathways. Structural brain malformations, such as holoprosencephaly, septo-optical dysplasia ( Fig. 5 ), lissencephaly, pachygyria, polymicrogyria, schizencephaly, and corpus callosum agenesis, can all affect optical nerves, optical radiations, or the visual cortex. Posterior fossa malformations, including Chiari and Dandy–Walker malformations, may distort visual pathways. White matter abnormalities (such as periventricular leukomalacia), congenital hydrocephalus, or arachnoid cysts, can compromise the optical radiations. Perinatal hypoxic-ischemic injury is the most common cause of congenital visual impairment worldwide, while congenital stroke or intracranial hemorrhage affecting visual structures further contributes to early-life vision loss. Genetic, metabolic, infectious, and inflammatory disorders may also manifest as congenital visual pathway deficits, highlighting the importance of neuroimaging for early detection and intervention, particularly when reversible causes can be identified.

Septo-optical dysplasia. ( A ) Coronal STIR showing diminutive bilateral optical nerves ( white arrows ). ( B ) Small optical canal bilaterally with diminutive canalicular segment of the bilateral optical nerves. ( C ) Axial T2 weighted imaging showing the lateral ventricles with an absent septum pellucidum.

Traumatic brain injury (TBI), brainstem injury, or cranial nerve trauma can disrupt vision. Focal cortical injury may cause immediate cortical blindness or hemianopia, while diffuse axonal injury can produce delayed visual field deficits and impaired visual attention. Traumatic ischemia involving the PCA territory may result in occipital lobe stroke with homonymous hemianopia. Injury to the optical chiasm or optical tracts may produce specific visual field defects, and higher-order cortical injury may result in visual neglect, agnosia, or impaired motion perception. MR imaging, particularly with susceptibility-weighted imaging and diffusion tensor imaging, plays a central role in assessing post-traumatic visual pathway injury.

Idiopathic visual loss encompasses conditions in which no structural, infectious, inflammatory, traumatic, or metabolic cause can be identified. Idiopathic intracranial hypertension (IIH) is characterized by elevated ICP of unknown etiology, producing papilledema and visual field loss. Functional or psychogenic visual disorders may present with apparent blindness in the setting of normal imaging and inconsistent examination findings. Idiopathic occipital atrophy is a rare condition associated with slowly progressive cortical visual loss. Neuroimaging may reveal subtle cortical atrophy or be entirely normal, necessitating careful correlation with clinical findings.

In summary, CNS diseases affecting vision encompass a broad range of etiologies, each with unique mechanisms of injury, clinical manifestations, and imaging characteristics. Infectious, inflammatory, neoplastic, vascular, metabolic, neurodegenerative, congenital, traumatic, and idiopathic disorders may impact any level of the visual pathway, from the retina to the occipital cortex. Advanced imaging modalities, particularly MR imaging and CT, are critical in identifying the location, extent, and nature of these lesions. Clinicians must integrate clinical examination, neuroimaging, and functional assessments to accurately localize pathology, guide treatment, and predict visual outcomes. Understanding the diverse causes of CNS-related visual impairment is essential for timely diagnosis, intervention, and preservation of visual function.