Nonorganic Vision Loss

Etiology

The etiology of NOVL is multifactorial and includes physiological, psychological, and social factors. Unlike organic visual impairments where an identifiable pathologic condition of the eye or visual pathway is present, NOVL arises absent observable pathologies.[1]

Psychogenic factors are important causes of NOVL. In some patients, vision loss may be a form of conversion disorder, where psychological distress is converted into physical symptoms. Patients with a history of anxiety, depression, posttraumatic stress disorder, or other psychiatric conditions may be more prone to NOVL. NOVL can also occur as a form of symptom amplification when an individual unconsciously exaggerates minor or nonspecific visual disturbances due to heightened health concerns.[10] Symptom amplification is most frequently observed in individuals with health anxiety or who have recently been diagnosed with an ocular condition; concerns about potential vision loss lead to an overemphasis on subjective visual symptoms.[11] NOVL may also present as part of factitious disorder or malingering, where the patient consciously feigns visual symptoms for secondary gain, such as seeking attention, evading responsibilities, or obtaining disability benefits.[12] However, these etiologies should be considered only after other potential causes have been thoroughly excluded.[4]

Some cases of NOVL are linked to a history of trauma or abuse; the visual symptoms represent a physical manifestation of the psychological impact of these experiences.[13] In children and adolescents, NOVL may be associated with school or family stressors.[14] Social and cultural factors may also influence the occurrence of NOVL.; individuals facing significant life stressors, with limited social support networks, or socioeconomically disadvantaged situations may be more susceptible to developing NOVL.[13]

In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), functional vision loss falls under the category of "Somatic Symptom and Related Disorders," specifically under the diagnosis of "Conversion Disorder (Functional Neurological Symptom Disorder)." The DSM-5 defines Conversion Disorder as one or more symptoms of altered voluntary motor or sensory function that are found, after appropriate medical assessment, to be incompatible with recognized neurological or medical conditions.[3]

Epidemiology

The frequency of NOVL varies among settings and studied populations. A randomized trial of 127 adult patients with convergence disorder demonstrated that 16% possessed functional visual symptoms.[6] 

A pediatric ophthalmology department in Belgium reported that from 2007 to 2014, 50% of children presenting with 'vision loss' were diagnosed with NOVL; the average age at diagnosis was 11 years, with a female predominance. Approximately 88% of affected children recovered within 2 weeks; the recurrence rate was 12.9%. Additionally, 25% of the children with NOVL required child psychiatric treatment.[14] Symptoms included blurred vision, diplopia, nystagmus, visual field deficits, and complete blindness.

While NOVL occurs in all age groups and sexes, some studies have suggested a slightly higher prevalence in women and adolescents.[13][14] The worldwide incidence and prevalence rates are poorly established due to varying reporting and diagnostic criteria. However, NOVL remains a notable contributor to visual impairment, given its significant psychosocial implications and impact on healthcare resources.

Pathophysiology

NOVL is a disorder of perception, as opposed to a structural or functional abnormality within the visual system. The pathogenic mechanisms of NOVL are poorly understood but likely involve psychological and neurophysiological processes.[15] Despite the lack of knowledge about the pathophysiologic processes of NOVL, the disease process is very real for the patient.[3]

NOVL is often associated with psychological conditions like anxiety, depression, or stress; the visual symptoms may serve as an unconscious coping mechanism for underlying psychological distress or trauma.[16] In this sense, NOVL could be viewed as a form of conversion disorder, where psychological stress manifests as a physical symptom.[17] At a neurophysiological level, the pathophysiology of NOVL may involve altered processing of visual information, leading to decoupled visual stimuli and conscious perception.[18] Early adverse experiences can potentially negatively affect the processing and interpretation of visual stimuli and manifest as vision loss.[14]

Some patients with NOVL have normal visual acuity but report symptoms such as tunnel vision or photophobia.[19] Other patients report dramatic vision loss but have normal responses to objective tests of visual function, like electroretinography or visual evoked potentials.[20][21]  

Malingering comprises a portion of cases of NOVL. Here, the pathophysiology is rooted in a conscious decision to feign visual impairment. The motivations behind malingering vary widely and can include gaining financial benefits, evading responsibilities, or seeking attention.[22]

Children are suggestible and often have a limited understanding of health and wellness. Some children misinterpret or exaggerate their visual symptoms due to confusion or fear, leading to discordance of self-reported vision loss and objective measures of visual function. The process of learning to read or dealing with school-related stress can sometimes trigger psychogenic visual symptoms.[23]

History and Physical

History

The presentation of NOVL varies widely. The history of the present illness of patients with NOVL may be notable for inconsistencies and fluctuations in reported symptoms.

Obtaining a comprehensive history is crucial when NOVL is suspected. It is essential to document the onset, duration, and progression of the reported visual symptoms, including visual complaints, such as blindness, or ocular findings, such as ptosis or blepharospasm.[17] Any sudden or inexplicable changes in vision or visual fields should be noted. Exacerbating or alleviating factors and associated symptoms such as headache, eye pain, or systemic symptoms should be queried. 

Patients with NOVL frequently report vision loss or disturbances that do not conform to an anatomical or physiological pattern. Patients may report complete vision loss in one eye but have no difficulty navigating or sudden severe vision loss with a normal ophthalmoscopic examination. Patients with NOVL may describe visual disturbances with unusual characteristics, such as "grey-out" or "white-out" episodes, which are not typically associated with organic visual disorders.[17]

The personal past ocular and medical history should be thoroughly reviewed, with particular attention to previous eye conditions, surgeries, or trauma, and systemic conditions that might affect vision, such as diabetes or neurological disorders. The psychosocial history can provide valuable clues in patients with NOVL. Occupation, hobbies, home life, and recent stressors can be particularly revealing.[13] Personal gains associated with vision loss, such as litigation or disability benefits, should be considered. The presence of psychiatric disorders such as anxiety or depression should be documented. 

It is essential to perform a thorough medication review; many medications can cause vision changes. This review should include prescribed medications, over-the-counter pharmaceuticals, herbs, supplements, and recreational substances.[24][25]

Physical Examination

A thorough physical examination should be performed. A complete eye examination is necessary, including assessment of visual acuity, refraction, color vision, visual fields, ocular motility, pupillary responses, and stereopsis. Examination of the anterior and posterior segments of the eye and intraocular pressure measurement is required.

The physical examination of patients with NOVL is typically normal. Vision testing often yields normal or near-normal results when not reliant on patient subjective responses; patients may claim they cannot see the chart for formal visual acuity testing but have no problem identifying objects or navigating around the room. The pupils will react normally, and ocular motility will be full. Ophthalmoscopic and slit-lamp examinations typically reveal no abnormalities.

Evaluation

The evaluation of NOVL primarily relies on the medical history and comprehensive eye examination. However, further objective evaluation may be needed to confirm the diagnosis and exclude coexisting organic pathologies.

Examination Techniques

Numerous examination techniques that exploit the automatic or unconscious nature of specific visual responses that are difficult for a person to control or suppress are beneficial when evaluating patients with suspected NOVL. These techniques include but are not limited to observing patients when they are unaware of being observed, the optokinetic drum or strip, confrontation of visual fields, variable visual acuity testing, stereopsis testing, color testing, and the mirror test. These tests should be performed in a supportive and nonaccusatory manner, remembering that many patients with NOVL are not intentionally producing their symptoms and may be dealing with underlying psychological stressors that require appropriate care and treatment. The key to diagnosing NOVL is recognizing inconsistencies in the history and physical examination and discriminating NOVL from potential organic causes of vision loss.

Observing Unaware Patients

Observing behavior when patients believe they are alone or unobserved can sometimes yield helpful information. Patients claiming total vision loss who navigate around objects in the room, read, or perform other visually guided tasks without difficulty could have NOVL.

Optokinetic Drum or Strip

The optokinetic drum or strip is a tool that can induce optokinetic nystagmus, an involuntary eye movement that occurs as the eyes track moving objects or patterns.[26] The optokinetic response is difficult to suppress consciously and can demonstrate preserved vision in patients claiming significant or total vision loss. The patient is asked to observe a rotating drum or moving strip with alternating black and white stripes during this test. Optokinetic nystagmus indicates that the patient can see the movement, even if they deny being able to do so.[27]

Confrontational Visual Field Testing

During confrontation visual field testing, the examiner compares their visual fields with those of the patient. The examiner can perform this test by wiggling their fingers and asking the patient to report when they see fingers wiggling in different parts of their visual field. Patients with NOVL may demonstrate a tubular or "gun barrel" field, only identifying targets presented directly in front of them, or results may be inconsistent.[28] A tubular field is when the patient identifies the edge of the visual field at a fixed distance from the visual axis, regardless of the distance at which the target is presented. This also can be described as tunnel vision, in which the tunnel remains at a fixed diameter. A normal visual field, or a restricted field caused by an organic process, should expand in size as the target shown is moved away from the observer.[29]

Variable Visual Acuity Testing

Manipulating the vision chart can sometimes reveal NOVL. Variations of misdirection may yield valuable information. Alternatively, occluding one eye and presenting the chart upside down or sideways can often lead to better-than-expected results as the patient may not realize they should be unable to read the chart in these orientations.[8][30]

Stereopsis Testing

Stereopsis is the perception of depth and three-dimensional structure obtained based on visual information derived from two eyes by individuals with normally developed binocular vision.[31] Patients reporting monocular vision loss who pass a stereopsis test that requires input from both eyes may have NOVL.

Color Testing

Red light testing, or the red desaturation test, is useful in assessing NOVL. During this test, the patient is asked to compare the brightness of a red light between both eyes. In organic pathologies, such as optic neuritis or severe glaucoma, the affected eye will perceive red light as less bright or saturated than the unaffected eye.[32][33] However, in NOVL, where the visual loss or impairment has no organic or physical cause, the perception of red light is usually equal in both eyes. Color testing relies on the principle that color vision, particularly red vision, is preserved until late in the course of organic eye diseases; discrepancies in reporting can suggest a nonorganic etiology.[33] This simple test should be used with other clinical findings and tests to establish a diagnosis. Ishihara color plates may be used for a more formal evaluation of color vision, but the red desaturation test is a quick test that does not require specialized equipment.[34]

Mirror Test

In the mirror test, a mirror reflects the image of an eye chart or other visual target into the eye that the patient claims is blind. The mirror is held on the side of the "good" eye, and if the patient can identify the chart or target, it indicates that the "bad" eye has functional vision.

Laboratory Tests

While there are no specific laboratory tests for NOVL, it may be necessary to order tests if an underlying physical or psychiatric condition is suspected. The choice of these tests depends on the specific presentation and may include a complete blood count, thyroid function tests, or tests for autoimmune conditions. 

Imaging

Radiographic imaging, such as magnetic resonance imaging or computed tomography, may be required to exclude organic pathologies, particularly in cases suggestive of neurological disease or inconsistent findings. These studies will typically reveal no abnormalities in patients with NOVL.

Optical Coherence Tomography

Optical coherence tomography can help corroborate the diagnosis of NOVL by demonstrating normal retinal and optic nerve anatomy in the face of reported visual loss.[35]

Electrodiagnostic Testing

Electrophysiological tests such as electroretinography and visually evoked potential may be employed to exclude retinal and optic nerve diseases, respectively. These tests typically reveal no abnormalities in patients with NOVL.[20][21]

Psychological Evaluation

A psychological evaluation is often beneficial because of the strong link between NOVL and psychological factors. Mental health professionals can identify stressors or psychiatric conditions, such as depression or anxiety, that may be contributing to symptoms.[36]

Treatment / Management

Effectively managing NOVL requires balancing reassurance, therapy, and referral when necessary. An essential component of managing NOVL is the physician-patient relationship, where trust and understanding are vital, and empathy and patience are paramount. Treating NOVL may be a prolonged process. Patients with NOVL may seek multiple opinions from clinicians. Surgical intervention is not required unless a coincident organic pathology is present.

Reassurance and Education

One of the mainstays of treatment in NOVL is patient reassurance. This is often the most challenging yet crucial part of the treatment, requiring delicacy and tact to communicate the diagnosis. The clinician should explain to the patient that their eyes and visual pathways function normally; no organic disease is present, but their symptoms are real. Educating patients about potential causes, such as stress or psychological factors, is beneficial.[37]

Referral to Mental and Behavioral Health Professionals

Referral to a psychologist or psychiatrist for further evaluation and management can be crucial to improving the quality of life in patients with NOVL. Cognitive-behavioral therapy may be beneficial. A mental health professional can help patients cope with contributing stressors or underlying psychiatric conditions.[38]

Continuity of Care

Patients with NOVL require frequent monitoring; the treatment plan should be adjusted as needed. The specific situation and clinical judgment of the healthcare provider dictate the timing of clinic visits.[38]

Differential Diagnosis

By definition, NOVL lacks causative identifiable organic pathology. However, organic causes of visual disturbances must be excluded before diagnosing NOVL. 

Commonly Encountered Organic Ocular Diseases

Cataracts, glaucoma, macular degeneration, retinal detachment, and optic neuritis are common ocular diseases that may present with visual changes or vision loss. While the physical examination, imaging studies, or laboratory testing typically demonstrate identifiable abnormalities, early or mild cases may not.

Some conditions may require more specialized diagnostic testing. For example, Stargardt disease, an inherited juvenile macular degeneration, often presents with vision loss during childhood or adolescence. Although certain signs may be present on ophthalmoscopic examination, such as yellow-white flecks at the level of the retinal pigment epithelium, these are not always apparent, especially in the early stages of the disease.[39] The diagnosis often relies on fluorescein angiography, which can demonstrate characteristic dark choroid or "silent choroid" alongside other specific findings like perifoveal hyperfluorescence.[40] 

Advanced imaging may be required to diagnose an organic cause of vision loss and avoid a misdiagnosis of NOVL. Neuro-ophthalmic conditions like optic neuritis or ischemic optic neuropathy may initially present with normal-appearing optic nerves or possess only retrobulbar findings.[41][42] Retinitis pigmentosa may be subtle in the early stages of the disease.[43] Glaucoma can masquerade as NOVL when it presents with normal intraocular pressure; this is normal-tension glaucoma.[44] These cases underscore the importance of a detailed assessment and often specialized testing when considering a diagnosis of NOVL. 

Commonly Misdiagnosed Organic Ocular Diseases

• Big Blind Spot Syndrome: Also known as enlarged blind spot syndrome, this condition is marked by an idiopathic enlargement of the physiologic blind spot, commonly associated with photopsia, scotomas, and visual field defects. The optic nerve typically appears normal, which may lead to a misdiagnosis of functional visual loss.[45] The pathophysiology of this syndrome is unclear, and treatment focuses on monitoring for the development of associated conditions, such as multiple evanescent white dot syndrome (MEWDS) or acute idiopathic blind spot enlargement (AIBSE).[46][47] Big blind spot syndrome may also be a paraneoplastic phenomenon.[48]

• Acute Zonal Occult Outer Retinopathy: This process typically affects young, myopic women, presenting as acute photopsia and an enlarging scotoma. The retinal exam may reveal no abnormalities, but electrophysiologic testing often shows significant changes. Atrophic changes of the retinal pigment epithelium may develop, and visual field defects often stabilize but do not improve.[49]

• Bilateral Retrochiasmal Disease: Diseases affecting the occipital lobe, such as strokes or tumors, can cause homonymous visual field defects that may be mistaken for functional visual loss if misinterpreted by the patient or clinician. The key to this diagnosis is the congruity of visual field defects, which is higher in more posterior lesions.[50][51] Neuroimaging is recommended and frequently required.[52]

• Chiasmal Disease without Optic Atrophy: Masses such as craniopharyngiomas or pituitary adenomas impinging on the optic chiasm can cause subtle bitemporal hemianopsia that is easily overlooked. Detailed perimetry and neuroimaging are mandatory when a lesion is suspected.[53]

• Cone-Rod Dystrophy: These rare, hereditary disorders cause progressive vision loss due to the death of the retinal photoreceptive cone and rod cells. Photophobia, reduced central vision, color vision disturbances, and peripheral visual field loss are common.[54]

• Early Keratoconus or Irregular Astigmatism: These conditions cause irregular corneal curvature, distortion of vision, and ghosting. Visual acuity can often be corrected to 20/20 with glasses in the early stages. However, rigid contact lenses may improve vision complaints.[55]

• Early Posterior Subcapsular Cataracts: These cataracts are located in the back of the lens and often cause significant glare and decreased visual acuity in bright light. The cataract may be subtle and not visualized during routine slit-lamp examination. The brightness acuity test can help detect glare and is an important test for these cataracts.[56]

• Leber Hereditary Optic Neuropathy: This process causes subacute loss of central vision in young adults, predominantly men. The optic nerve may initially appear normal despite significant vision loss. Genetic testing is required for diagnosis.[57]

• Macular Changes: Subtle central serous retinopathy, macular edema, and epiretinal membrane cause subtle macular changes and distort central vision. Optical coherence tomography may be required to confirm the diagnosis.[58]

• Paraneoplastic Retinopathy: These conditions, including cancer-associated retinopathy and melanoma-associated retinopathy, cause rapid, painless vision loss. Measurable autoantibodies associated with systemic malignancy attack the retina, causing significant damage.[59]

• Retinitis Pigmentosa Sine Pigmento: This variant of retinitis pigmentosa presents with night blindness and peripheral visual field loss but lacks the classic bone spicule pigmentation early in the disease. Electroretinogram testing is required for diagnosis.[60]

• Retrobulbar Optic Neuropathy: Often caused by demyelinating diseases such as multiple sclerosis, this condition affects the optic nerve behind the globe. Rapid vision loss, pain with eye movement, and an afferent pupillary defect can occur even while the optic nerve head appears normal.[61]

Migraine Headaches

Visual disturbances occur frequently during a migrainous episode and may be mistaken for NOVL. Patients with migraine headaches often describe their visual symptoms as transient, short-lived, and associated with headache, nausea, or sensitivity to light or sound; the duration of symptoms varies.[62]

Functional Neurological Disorder

Conversion disorder, also known as functional neurological symptom disorder, is a condition where patients present with physical neurological symptoms without an identifiable organic cause. Symptoms may include vision loss. Conversion disorder is believed to be a psychological response to stressful situations, trauma, or underlying mental health issues. The symptoms are not intentionally produced and may cause significant distress and impairment in social and occupational functioning.[63]

Somatic Symptom Disorder

Somatic symptom disorder is a psychiatric condition characterized by an excessive focus on physical symptoms that cause significant distress and interfere with daily functioning. Patients may present with a variety of physical complaints, including vision loss. The primary concern is not the presence or absence of a medical condition but the excessive reaction and health concerns in response to symptoms, which persist despite appropriate medical evaluation and reassurance.[64]

Malingering

Malingering is a condition characterized by the intentional production of false or grossly exaggerated physical or psychological symptoms. Individuals who are malingering are typically motivated by external incentives such as obtaining medication, avoiding work, evading criminal prosecution, or gaining other personal benefits. Malingering is not considered a psychiatric disorder but a deliberate attempt to deceive and manipulate others for personal gain.[12] 

Malingering with visual symptoms is still termed NOVL. In these cases, individuals consciously feign vision loss or exaggerate existing minor visual disturbances to achieve a particular external benefit. Unlike other forms of NOVL, patients with malingering are fully aware of their deception. Recognizing malingering is crucial in evaluating NOVL as it helps avoid unnecessary medical procedures and interventions.

Prognosis

The prognosis for NOVL varies with the underlying cause. With proper identification and management of the cause, most patients with NOVL experience significant improvement or complete resolution of their symptoms.[37] The prognosis also depends on timely and accurate diagnosis, close monitoring, and personalized treatment planning.[65] 

In patients with functional vision loss related to conversion disorder or somatic symptom disorder, the prognosis is generally favorable with psychological intervention.[17] These individuals often improve considerably when the treatment approach incorporates cognitive-behavioral therapy techniques. Developing a strong therapeutic alliance between the healthcare provider and the patient significantly improves the outcome.[6]

In cases of malingering, the prognosis for the visual disturbance itself is inherently good since the deficit is not due to underlying ocular pathology. However, addressing the driving factors behind malingering can be challenging and may require a multifaceted approach involving mental health professionals, social workers, or law enforcement.[22]

NOVL in children secondary to stressors or attention-seeking behaviors often improves when the underlying issue is identified and addressed. In many cases, reassurance and time are significant factors in the resolution of symptoms.[14]

Complications

NOVL does not cause direct physical harm; it can have significant effects on mental health, daily functioning, and quality of life. Patients with NOVL often experience a high degree of anxiety, frustration, and distress that exacerbates preexisting mental health conditions and may lead to the development of depressive symptoms or anxiety disorders.[66] Individuals with NOVL may face challenges in carrying out their daily activities, such as reading, driving, or walking. This can result in a reduced quality of life and increased dependence on others for assistance.[3] Stigmatization and misunderstanding by others can further add to their distress and isolation.

If the nonorganic nature of the vision loss is not recognized early, multiple consultations, invasive investigations, and unnecessary treatments may ensue, leading to undue physical, psychological, and financial burdens to the patient.[67] Contrarily, focusing on nonorganic symptoms might overshadow a concurrent organic pathology, delaying appropriate diagnosis and treatment and leading to potentially avoidable vision loss or progression of the underlying organic condition.