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Understanding Cortical Blindness: Essential Guide for Optometrists

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Gain a comprehensive understanding of cortical blindness with this guide for optometrists, featuring tips for identifying and managing patients.

Understanding Cortical Blindness: Essential Guide for Optometrists
Patients with cortical blindness present with devastating vision loss without any remarkable anterior or posterior segment abnormalities. The presence of fully intact pupillary reflexes further compounds the problem, making the diagnostic process of cortical blindness (CB) complex and challenging.
This article will provide essential information so optometrists can understand cortical blindness, leading to timely treatment, management, and improved visual outcomes.

Cortical blindness terminology

The terms cortical blindness, cerebral blindness, and cortical visual impairment are sometimes used interchangeably, but they each have their own distinct meanings.
  1. Cortical blindness: Defined as vision loss due to damage to the primary visual striate cortex, V1, in the occipital lobe of the brain.1
  2. Cerebral blindness: Structurally, cerebral blindness refers to damage at V1 and the surrounding subcortical visual pathway. As CB refers to dysfunction at V1, CB can be thought of as a subtype of cerebral blindness.1
  3. Cerebral/cortical visual impairment (CVI): The preferred terminology used by pediatric specialties because it describes a more variable condition associated with neuroplasticity.2

Prevalence of cortical blindness

The prevalence of CB in the general population has not been adequately investigated, but CB is thought to be fairly uncommon.1,3 In 2003, Flanagan et al. reported a prevalence rate of 161 per 100,000 for the incidence of newly certified visually impaired children under 16 years of age.4

Review of ocular and brain anatomy

A brief overview of the ocular and brain anatomy can assist with the appreciation of the terminology and pathophysiology of CB.

Visual pathway

Visual information from the retina travels from the optic nerve to the optic chiasm, where the inner retinal fibers cross over and rejoin in the optic tract before reaching the lateral geniculate nucleus (LGN) in the thalamus.
From the LGN, optic radiations carry the data to the primary visual striate cortex in the occipital lobe, known as V1. The surrounding subcortical areas V2 to V5 link to other parts of the brain.1
Figure 1 illustrates the primary visual striate cortex and subcortical areas of the occipital lobe. The diagram shows the (a) frontal lobe at the anterior region of the brain with the (b) occipital lobe at the posterior end. The (c) subcortical areas surround the (d) primary visual striate cortex, V1.
Primary visual striate cortex
Figure 1: Courtesy of Tyler Mathenia, MD.

Blood supply

The optic tract is supplied by the posterior cerebral artery (PCA), while the optic radiation receives its blood supply from the middle cerebral artery (MCA). The occipital lobe is primarily nourished by the PCA, with a smaller contribution from the MCA.1

Causes and pathophysiology of CVI

Hypoxia, or oxygen deprivation, causes damage to the visual cortex, resulting in CVI. The most common cause of CVI in the pediatric population (22%) is perinatal hypoxia (i.e., impaired blood flow to the placenta, a birth complication).3
Additional causes of CVI include central nervous system (CNS) structure abnormalities, infection, metabolic disorders, chromosomal aberrations, epileptic encephalopathy, traumatic events, and other mixed etiologies.4
  1. Epilepsy: Notably, epilepsy and epileptic drugs seem to produce specific vision loss; specifically infantile spasms that appear between 3 and 8 months of age, can result in central visual impairment. The exact pathogenesis of visual impairment in patients with infantile spasms is uncertain.2
    1. Vigabatrin, an antiepileptic drug used in infantile spasms, may cause permanent, concentric peripheral visual field loss due to drug-induced injury to both the retinal photoreceptors and the retinal ganglion cells and their axons.5
  2. Hydrocephalus: Hydrocephalus leads to chronic distention of the posterior cortex, contributing to cerebral visual impairment. Additionally, secondary elevation of intracranial pressure can exacerbate CVI.
  3. Hypoxic-ischemic encephalopathy (HIE): CVI resulting from HIE involves damage to the visual processing areas of the brain due to inadequate oxygen supply. Perinatal and postnatal HIE represent the most prevalent cause of CVI.
  4. Infections: Infections from bacteria, viruses, or parasites are implicated in CVI. Various mechanisms by which infection might harm the brain include thrombophlebitis, arterial occlusion, hypoxic-ischemic damage, venous sinus thrombosis, and hydrocephalus. Examples include TORCH (toxoplasmosis; other [syphilis, rubella, cytomegalovirus, and herpesvirus]) infections.
  5. Trauma: Direct damage to the visual cortex is another cause of CVI. Trauma can be non-accidental, such as in shaken baby syndrome.
  6. Other causes of CVI: Brain tumors, cerebrovascular accidents, congenital brain malformations, hemodialysis, hypoglycemia, and metabolic and neurodegenerative disease are other causes of CVI.

Etiology and pathophysiology of CB

Spontaneous ischemic stroke (32%) and cardiac arrest or surgery (20%) are the primary causes of cortical blindness in adults. They represent vascular and perfusion-related issues that impede blood flow, compromising oxygen and nutrients to the visual cortex, and manifesting as cortical blindness.8
The other numerous and diverse causes of CB in adults are summarized below.

Vascular conditions linked with CB

Inadequate vascular supply of blood and nutrients to the occipital lobe is the most common cause of cortical blindness (CB).
Vascular conditions include:
  • Bilateral occipital infarction
  • Dural venous sinus thrombosis
  • Hypoperfusion or hypoxia related to cardiac arrest
  • Carbon monoxide poisoning
  • Spinal surgery
  • Posterior reversible encephalopathy syndrome
  • Preeclampsia, eclampsia
  • Angiographic contrast agents

Infectious diseases associated with CB

CB resulting from infection is typically due to direct microbial invasion, inflammation, or secondary vascular compromise.
Infectious disorders are:
  • Meningitis
  • Subacute sclerosing panencephalitis (SSPE)
  • Creutzfeldt-Jakob disease (Heidenhain variant)
  • COVID-19
  • Progressive multifocaI leukoencephalopathy

Metabolic disturbances and cortical blindness

Metabolic imbalances in glucose, electrolytes, or oxygen compromise neuronal function, culminating in CB.
Several metabolic conditions include:
  • Hypoglycemia
  • Nonketotic hyperglycemia
  • Hepatic encephalopathy
  • Ornithine transcarbamylase (OTC) deficiency-related hyperammonemic encephalopathy

Mitochondrial conditions linked with CB

In mitochondrial disease, the mitochondria impairs energy production necessary for normal neuronal activity, particularly in the occipital cortex.
Mitochondrial conditions in adults are:
  • Mitochondrial encephalopathy (i.e., mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes [MELAS] syndrome)
  • Leigh disease

Neurodegenerative diseases associated with CB

In neurodegenerative diseases, the progressive degeneration of brain structures, including the occipital cortex, contributes to cortical blindness through the cumulative impact on visual processing pathways.
Neurodegenerative diseases associated with CB:
  • Leukodystrophy
  • Alzheimer’s disease (posterior cortical atrophy)

Other factors connected with CB

The other conditions, causes, and pathophysiologies of CB are diverse and numerous and include:
  • Seizures and postictal state
  • Radiation necrosis or stroke-like migraine attack after radiation therapy (SMART)
  • Demyelinating disease (Schilder variant)
  • Periventricular leukomalacia
  • Electrocution
  • Electroconvulsive therapy
  • Ozone-induced encephalopathy

Presentation of cortical blindness

The classic presentation of CB is characterized by (1) severe bilateral and symmetric vision loss, (2) little to no anterior and posterior segment findings, (3) fully intact pupillary light reflexes with no relative afferent pupil defect (RAPD), and (4) presence of homonymous hemianopsia visual field defect, which may be partial or complete.1,4,7
The severity of vision loss can range from no light perception to near-normal visual acuity in children and adults.9 Near-normal visual acuity can occur as a result of macular sparing.1

Signs and symptoms of CVI

In pediatric patients with CVI, ocular signs and symptoms may deviate from the classic presentation with the addition of associated neurological conditions.
Ocular findings in CVI include:9
  • Exotropia (41%)
  • Mild optic atrophy (25%)
  • Nystagmus (21%)
  • High refractive error (20%, [e.g., hyperopia >+3D and myopia >-2D])
  • Esotropia (19%)
CVI is often associated with other neurologic deficits, including epilepsy, cerebral palsy, hemiparesis, microcephaly, and hearing loss.9

Diagnostic testing for cortical blindness


Clinical electrophysiological testing incorporates noninvasive procedures that provide an objective indication of function at various locations within the visual system.10 In situations involving unexplained or suspected functional visual loss, normal electrophysiology can effectively exclude organic causes.10
Valuable visual electrophysiology tests employed in diagnosing CB and CVI include electroretinography (ERG) and visually evoked potential (VEP). ERG assesses the functional integrity of the retina to brief flashes of light,10 while VEP measures optic nerve and post-retinal pathway function.
Flash VEPs, which use diffuse flash stimulation, are less sensitive but suit young children, patients with poor fixation, and non-compliant patients.10


Neuroimaging is crucial for assessing the location and amount of damage, differentiating optic nerve and cortical involvement, and aiding in the prognosis of visual recovery.7
Computed tomography (CT) offers initial accessibility but may overlook early or small strokes.7 Magnetic resonance imaging (MRI) is superior for diagnosing cerebral infarction, meningitis, encephalitis, and neurodegenerative disorders, with diffusion-weighted MRI pinpointing acute infarction areas.7

Optokinetic nystagmus testing

Optokinetic nystagmus (OKN) is an involuntary eye movement in response to moving visual stimuli, like stripes on an optokinetic drum. The OKN response estimates visual and neurological functions and can be abnormal or missing in patients with CB/CVI.11,12
It has been shown that OKN can be generated in patients with CB and CVI due to subcortical mechanisms or extrastriate pathways.11,12 The unreliability of OKN testing makes it best suited as a quick and adjunctive tool when neuroimaging equipment is not available.

Visual acuity testing

As mentioned earlier, patients often present with bilateral symmetric vision loss that can range from almost normal visual acuity in cases of macular sparing, and extend to finger counting, hand motion, or no light perception.1,9

Visual field testing

Visual field testing should be performed whenever possible. Visual field defects can be correlated with findings regarding location, damage, and amount of vision loss. Lesions in different areas of V1 correspond to different types of visual field defects.12
For example, anterior cortex lesions, typically from PCA stroke, cause contralateral congruous homonymous hemianopia with macular sparing. This occurs because blood to the occipital cortex tip is supplied by the unaffected MCA in PCA stroke.1
Figure 2 presents a cross-sectional diagram of the V1 area, whereas Figure 3 represents the corresponding visual field defects.12,13
Visual pathways
Figure 2: Courtesy of Cindy Hui, OD.
CB lesion location and visual field defect
Figure 3: Courtesy of Cindy Hui, OD.

Differential diagnoses for cortical blindness

Ocular conditions that produce symmetrically reduced vision in both eyes, normal pupillary reflexes, and unremarkable anterior and posterior segment findings should be considered in the differential diagnosis of cortical blindness.3

Ocular disorders

Bilateral retrobulbar optic neuritis

Bilateral retrobulbar optic neuritis, can present with central and peripheral vision loss with a normal fundus appearance.3 Distinguishing features include sluggish pupils, color vision impairment, and eye pain with movement.15

Genetically-determined retinal photoreceptor degeneration

Genetically-determined retinal photoreceptor degeneration, like foveal cone dystrophy, is characterized by central vision loss with color vision abnormalities. Abnormal ERG findings occur due to impairment of the foveal cone cells.16

Glaucoma and retinitis pigmentosa

Glaucoma and retinitis pigmentosa (RP) exhibit peripheral visual field loss, with possible macular sparing. Unlike cortical blindness from bilateral PCA infarctions, they lack bilateral homonymous hemianopias.3

Leber congenital amaurosis

Infants with retinal degenerations, such as Leber congenital amaurosis (LCA), present with nystagmus, sluggish or absent pupillary responses, severely decreased visual acuity, photophobia, and high hyperopia. Diagnosis of LCA relies on severely subnormal or non-detectable ERGs, optical coherence tomography (OCT), and genetic testing.17

Leber hereditary optic neuropathy (LHON)

Leber hereditary optic neuropathy (LHON) presents with vision and color loss, featuring a cecocentral scotoma. A pupillary defect may only appear in the acute stage.18

Ocular migraines

Migraines, including ocular migraines, may simulate cortical blindness by causing restricted visual fields or tunnel vision during an episode.19 With ocular migraines, visual field changes are temporary and variable, lasting for up to 30 minutes.

Oculomotor apraxia

Young children with oculomotor apraxia (OMA) often get misdiagnosed as blind due to an inability to orient their eyes to visual targets. Symptoms include difficulty fixating, head thrusting, and abnormal OKN.20

Paraneoplastic retinopathies

Paraneoplastic retinopathies, such as cancer-associated retinopathy (CAR), may cause mild pupillary light reflex reduction, severe vision loss, ring scotoma, and other visual field defects with minimal fundus abnormalities. Retinal and optic nerve autoantibody testing and ERG are starting points in the diagnosis of CAR.21

Non-organic disorders with similar presentations to CB

Non-organic disorders that produce symmetrically reduced vision in both eyes, normal pupillary reflexes, and unremarkable anterior and posterior segment findings should be considered in the differential diagnosis of cortical blindness.
Non-organic disorders that can mimic cortical blindness include hemineglect, malingering, prosopagnosia, and simultagnosia.1
  1. Hemineglect: Hemineglect and CB share similarities in impaired awareness, both resulting from brain damage, affecting perception or attention. Hemineglect is associated with damage to the parietal lobe, not at V1.
  2. Malingering: Malingering is a conscious and intentional exaggeration or feigning of physical or psychological symptoms. Objective testing for OKN and VEP can be helpful. Visual field testing can generate unusual outcomes.
  3. Prosopagnosia: Prosopagnosia is a neurological condition characterized by the inability to recognize faces. It often results from damage to the fusiform gyrus, a region in the temporal lobe of the brain associated with face recognition.
  4. Simultagnosia: Simultagnosia is a neurological condition characterized by the inability to perceive a visual scene as a whole, only able to process one object at a time. Patients will often have homonymous or juxtaposed homonymous visual field deficits due to bilateral parieto-occipital damage.

Treatment and management of CB

Pediatric treatment of CVI

A significant proportion of children with CVI experience improvement in visual function with therapy. A review by Matsuba et al. evaluated the long-term outcome of children with congenital CVI and found that 46% of the children had at least one level of visual improvement, compared to 8% of children who experienced visual decline.26

Treatment of concomitant ocular/visual disorders

Any concomitant visual disorders should be corrected, including underlying refractive error, strabismus, and amblyopia. Likewise, ocular disorders such as congenital cataract or retinal disease should be treated.5

Vision therapy for pediatric patients with CVI

Vision therapy for children with CVI consists of exercises and training to improve (1) visual awareness and attention, (2) visual perception, (3) scanning and tracking, and (4) hand-eye coordination.27

Adult treatment of cortical blindness

Substitution therapy

Substitutive interventions feature adapted lighting, environmental modification, and prism therapy to support activities of daily living (ADLs). Adapted lighting entails optimizing the position and brightness to maximize residual vision. Environmental modification improves contrast by minimizing patterns, such as removing heavily patterned rugs.
Visual substitution therapy with prisms shifts images from damaged portions of the retina projecting to the intact visual cortex, enabling patients to capture visual information that would otherwise be missed.28

Compensation therapy

Compensation therapy, similar to visual substitution therapy without prisms, trains patients in deliberate head and eye movements to (1) increase saccades toward the impaired visual field, (2) vary saccade amplitude for increased sampling efficiency, and (3) develop organized scanning patterns in areas of their visual field defect.28


The purpose of visual restitutive interventions is to restore vision and reduce visual field defect size by training impaired functions or repeatedly stimulating areas of the visual field.
Visual restoration approaches usually employ computer-based vision training that provides repeated exposure to target stimuli to activate the brain and restore vision.28

Brain stimulation

Visual training could potentially be enhanced with noninvasive electric brain stimulation, with various strategies currently under investigation as potential adjuvants to training. These include transcranial random noise stimulation (tRNS), transcranial direct current stimulation (tDCS), and repeated transorbital alternating current stimulation (rtACS).28


The use of pharmacology in vision recovery post-stroke is under research, with several studies suggesting that serotonin reuptake inhibitors could enhance plasticity in the adult visual system. The mechanism works by reopening a critical period to facilitate recovery and prolonging the transient phase of increased plasticity post-stroke.28

Co-management of CB and CVI

Educating patients

Educating patients and their families about their condition, government programs, low vision services, and special education services available to them is imperative for ongoing care. Coordinating with social services empowers patients and families to take full advantage of available opportunities and support.27
Many low vision clinics offer a full spectrum of rehabilitation services as well. These include training on orientation and mobility, independent living skills, assistive technology, and reading/writing with braille.
Preventing perinatal hypoxic-ischemic encephalopathy and preterm delivery is the optimum technique for limiting vision loss from CVI.2 Patient education and promoting compliance with specialists in the patient’s medical team can circumvent adverse effects.

Collaborative care to treat CB and CVI

Children with CVI commonly have co-morbidities like cerebral palsy, developmental delay, and autism spectrum disorder (ASD). Partnering with pediatricians and/or child psychologists to treat these conditions is significant as systemic improvements may also influence and benefit a patient’s visual outcome.5
Part of managing patients requires integrating care with the patient’s neurovascular medical team to treat the underlying condition of CB and prevent future ischemic events, such as in cases of cerebral infarction.3
Additionally, sleep disturbances are common in patients with severe CB, likely resulting from a loss of the circadian rhythm controlled by light. These sleep disturbances can manifest as restlessness, wandering, mood swings, agitation, and akathisia (the inability to sit still).
Co-management with neurologists or psychiatrists can help restore sleep cycles and manage other psychological concerns in patients with CB.29


While this article simplifies the topic of CB, the true challenge lies in managing CB patients with severe vision loss.
This emphasizes the importance of eyecare providers engaging in collaborative care with neurologists, psychologists, and rehabilitation specialists for optimal outcomes in dealing with cortical blindness and cortical visual impairment.
  1. Sarkar S, Tripathy K. Cortical Blindness. [Updated 2023 Aug 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
  2. Bjornsson HD, Al-Zubidi N, Saluja G, et al. Cerebral Visual Impairment. EyeWiki. Updated August 1, 2023. Accessed December 13, 2023.
  3. Khanna S. Cortical blindness. MedLink Neurology. Published July 14, 1997. Updated November 6, 2023. Accessed December 13, 2023.
  4. Flanagan NM, Jackson AJ, Hill AE. Visual impairment in childhood: insights from a community-based survey. Child Care Health Dev. 2003;29(6):493-499. doi:10.1046/j.1365-2214.2003.00369.x
  5. Huo R, Burden SK, Hoyt CS, Good WV. Chronic cortical visual impairment in children: aetiology, prognosis, and associated neurological deficits. Br J Ophthalmol. 1999;83(6):670-675. doi:10.1136/bjo.83.6.670
  6. Chang MY, Borchert MS. Advances in the evaluation and management of cortical/cerebral visual impairment in children. Surv Ophthalmol. 2020;65(6):708-724. doi:10.1016/j.survophthal.2020.03.001
  7. American Association for Pediatric Ophthalmology and Strabismus. Vigabatrin: The Problem of Monitoring for Peripheral Vision Loss in Children. American Association for Pediatric Ophthalmology and Strabismus. Published July 2017. Accessed December 13, 2023.
  8. Aldrich MS, Alessi AG, Beck RW, Gilman S. Cortical blindness: etiology, diagnosis, and prognosis. Ann Neurol. 1987;21(2):149-158. doi:10.1002/ana.410210207
  9. Khetpal V, Donahue SP. Cortical visual impairment: etiology, associated findings, and prognosis in a tertiary care setting. J AAPOS. 2007;11(3):235-239. doi:10.1016/j.jaapos.2007.01.122
  10. Robson AG, Nilsson J, Li S, et al. ISCEV guide to visual electrodiagnostic procedures. Doc Ophthalmol. 2018;136(1):1-26. doi:10.1007/s10633-017-9621-y
  11. Van Hof-van Duin J, Mohn G. Optokinetic and spontaneous nystagmus in children with neurological disorders. Behav Brain Res. 1983;10(1):163-175. doi:10.1016/0166-4328(83)90162-6
  12. Okiyama R, Shimizu N. Optokinetic response and adaptation of the vestibulo-ocular reflex (VOR) in a patient with chronic cortical blindness. Acta Otolaryngol Suppl. 1991;481:556-558. doi:10.3109/00016489109131469
  13. Ogawa K, Ishikawa H, Suzuki Y, et al. Clinical study of the visual field defects caused by occipital lobe lesions. Cerebrovasc Dis. 2014;37(2):102-108. doi:10.1159/000356848
  14. Wong AM, Sharpe JA. Representation of the visual field in the human occipital cortex: a magnetic resonance imaging and perimetric correlation. Arch Ophthalmol. 1999;117(2):208-217. doi:10.1001/archopht.117.2.208
  15. Jirawuthiworavong GV, Miller AM, Al-Zubidi N, et al. Demyelinating Optic Neuritis. EyeWiki. Updated September 27, 2023. Accessed December 15, 2023.
  16. Schroeder M, Kjellström U. Full-field ERG as a predictor of the natural course of ABCA4-associated retinal degenerations. Mol Vis. 2018;24:1-16. Published 2018 Jan 4.
  17. Dumitrescu AV, Epley KD, Tang PH, et al. Leber Congenital Amaurosis. EyeWiki. Updated October 12, 2023. Accessed December 15, 2023.
  18. Winters J, Shah SB, Epley KD, et al. Leber Hereditary Optic Neuropathy. EyeWiki. Updated November 13, 2023. Accessed December 15, 2023.
  19. Othman BA, Ponce CP, Igbinoba R, et al. Ophthalmologic Manifestations of Migraines. EyeWiki. Updated April 19, 2023. Accessed December 15, 2023.
  20. Ditta L, Al-Zubidi N, Dryden SC, et al. Oculomotor Apraxia. Updated October 10, 2023. Accessed December 15, 2023.
  21. Vickers A, Ponce CP. Ophthalmologic Manifestations of Paraneoplastic Syndromes. EyeWiki. Updated November 3, 2023. Accessed December 15, 2023.
  22. Cojan Y, Saj A, Vuilleumier P. Brain Substrates for Distinct Spatial Processing Components Contributing to Hemineglect in Humans. Brain Sci. 2021;11(12):1584. Published 2021 Nov 29. doi:10.3390/brainsci11121584
  23. Incesu AI. Tests for malingering in ophthalmology. Int J Ophthalmol. 2013;6(5):708-717. Published 2013 Oct 18. doi:10.3980/j.issn.2222-3959.2013.05.30
  24. Al-Zubidi N, Bhat N, Belushi FA. Prosopagnosia. EyeWiki. Updated October 11, 2023. Accessed December 15, 2023.
  25. Lee AG, Al-Zubidi N, Kini A, Othman BA. Simultanagnosia. EyeWiki. Updated November 13, 2023. Accessed December 15, 2023.
  26. Matsuba CA, Jan JE. Long-term outcome of children with cortical visual impairment. Dev Med Child Neurol. 2006;48(6):508-512. doi:10.1017/S0012162206001071
  27. Phuljhele S, Saluja G, Dhiman R, Saxena R. Current perspective: Cerebral visual impairment-The impending doom. Indian J Ophthalmol. 2023;71(10):3277-3279. doi:10.4103/IJO.IJO_2446_23
  28. Saionz EL, Feldon SE, Huxlin KR. Rehabilitation of cortically induced visual field loss. Curr Opin Neurol. 2021;34(1):67-74. doi:10.1097/WCO.0000000000000884
  29. Gaber TA. Rehabilitation of cortical blindness secondary to stroke. NeuroRehabilitation. 2010;27(4):321-325. doi:10.3233/NRE-2010-0615
Cindy Hui, OD
About Cindy Hui, OD

Dr. Cindy Hui was born a myope and grew up in the San Francisco Bay Area. In her youth, she spent countless hours at her optometrist’s office as a patient, and then later on as a very eager protege. She graduated from the University of California at Berkeley and then attended the Southern California College of Optometry and has been a practicing optometrist ever since.

She dedicates her time seeing patients and has an affinity for treating nursing home and psychiatric patients.

Dr. Hui stands up for integrity, authenticity, and kindness to animals. In her spare time, she likes watching true crime shows, crocheting and cave diving.

Cindy Hui, OD
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