Filling in the Blind Spot: Integrating Charles Bonnet Syndrome Screening in Ophthalmology

Introduction

Charles Bonnet Syndrome (CBS) is an ophthalmic condition characterized by complex visual hallucinations in patients with significant visual impairments, but otherwise preserved cognitive function and insight.^1,2 It was initially recognized by the Swiss naturalist Charles Bonnet, who was attempting to describe the condition in his grandfather Charles Lullin. Today, CBS remains a fascinating yet underrecognized phenomenon in clinical practice.^1,2 Patients often report vivid hallucinations of people, animals, or geometric patterns.^1,3 Interestingly, patients with CBS retain complete insight about the hallucinations, which makes this syndrome distinct from other neurologic or psychiatric conditions that may cause visual hallucinations.

With an increasingly aging population, the incidence of conditions that may lead to CBS is expected to increase. Some of these include age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma.⁴ Therefore, there is a growing patient population that may be at risk of developing CBS in the future.^2,3 Some studies have reported the prevalence of CBS to be from 11.8% to as high as 17.7% among patients with retinal diseases, low vision, and glaucoma, and it can be as high as 24.6% among visual rehabilitation patients.⁵ Additionally, the true prevalence of the disorder is likely underestimated due to underreporting. Many patients are reluctant to admit to having symptoms of the disorder due to fear of psychiatric labeling,^2,3,6 and clinicians may fail to recognize the etiology of these symptoms during routine care.⁶ As a result, CBS is frequently misdiagnosed or missed entirely, preventing patients from receiving education and resources that could substantially improve quality of life.^6,7

Despite being recognized for over two centuries, there is no universally accepted diagnostic definition of CBS. However, inclusion in the 11th revision of the International Classification of Diseases (ICD-11) could potentially help standardize the diagnosis among clinicians.^3,6–8 While hallucinations and vision loss are common requirements for diagnosis, there is considerable disagreement as to the content of the hallucinations and the degree of vision loss required for diagnosis.⁸ The lack of standardization affects both the quality of clinical care and efforts to research the impact and management of CBS.

Misdiagnosis of CBS as a psychiatric disorder can lead to inappropriate consultations or treatments, which can potentially expose patients to untoward adverse effects, especially in older patients who are more likely to have predisposing conditions.^2,3 Failure to recognize this disease can lead to patients with decreased quality of life, feelings of isolation, increased burden of visual impairment, and potentially psychiatric sequelae from distressing hallucinations.^2,7 It is essential for clinicians to identify and manage this syndrome early and adopt a systematic approach for the education and management of this condition.

The aims of this study are to examine the literature using a structured approach and create a systematic, practical approach that can be used in ophthalmology clinics to screen for CBS based on current practices and available evidence. We first examined the literature and determined groups most at risk for CBS. Then, we examined the literature for clinical approaches and validated tools that are commonly used in clinical research. Finally, we identified barriers to diagnosis and potentially solutions offered by previous authors. A standardized method of screening and identification is vital to improving patient outcomes, particularly given the wide heterogeneity in prevalence estimates and diagnostic thresholds across the literature.

Materials and Methods

We performed a structured review of multiple databases. Use of Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines was considered, however the multiplicity of the questions we aimed to answer would not fit well in a Patient/Population/Problem, Intervention, Comparison, and Outcome (PICO) framework, and we expected significant heterogeneity in the type of studies that would be useful for this review. We therefore decided to create a proprietary approach better suited to our study aims while still retaining a rigorous methodology. Studies were screened for their suitability of inclusion based on inclusion and exclusion criteria devised by our research team. Inclusion criteria focused on studies of CBS and populations at risk due to vision-impairing ocular conditions, particularly AMD, glaucoma, DR, and other major causes of low vision. Articles deemed relevant included studies that utilized or examined screening tools or diagnostic methods, epidemiology, and potential risk factors, as well as those focusing on clinical management and diagnosis. Article types that were included were systematic reviews, meta-analyses, relevant narrative reviews, observational studies where patients were either screened for CBS or involved patients with previously diagnosed CBS, clinical trials, and case series with five or more patients. Included articles were either peer-reviewed manuscripts or validated abstracts that were published in English.

Exclusion criteria included studies focusing on hallucinations primarily related to psychiatric or neurological etiologies, studies where CBS was only mentioned incidentally, studies that focused on non-visual hallucinations, studies that focused mainly on treatment, studies that did not have a full text or abstract, studies that were not peer-reviewed articles, or case reports and case series that included less than 5 patients. The decision to remove non-English language studies was made on the basis of feasibility, given that accurate translation of full-text articles in multiple languages was beyond the scope of our resources.

Databases that were searched included PubMed, Embase, Web of Science, and Scopus using the following search terms that can be found in Box 1:

BOX 1 Search Terms

A total of 1,582 records were found on initial search (PubMed N = 276, Scopus N = 368, Web of Science N = 218, and Embase N = 720) and added to a Zotero database. These databases were selected given their exhaustiveness and the ability to download search results in a format compatible with Zotero. Duplicate studies were then removed manually (N = 749), and subsequently English language studies were also removed (N = 115). A total of 718 papers remained for title and abstract screening.

Title and abstract review were conducted in two rounds. Two reviewers examined the titles and abstract for each study and made a determination of whether the study fit inclusion or exclusion criteria. Reviewers were blinded to the decision of the other reviewer, and any discordance was resolved by a third reviewer during the second, tie-breaker round. Studies that passed text and abstract review were included in the full-text review (N = 114).

Full-text review was conducted by extraction of the following details from each study: study title, DOI, authors, publication year, study type, sample size, patient population, CBS screening tools used (if any), risk factors identified, study design, methods, main findings, and limitations. Data was extracted and compiled on a single excel sheet, along with the vote from the research member who reviewed the study. Decision regarding inclusion was made based upon discussion between research team members. A total of 25 studies were removed, 4 of which did not contain useful information about CBS based on the discretion of our reviewers, 12 of which were editorial articles or case reports, 1 of which was a foreign language article, and 8 of which were duplicates that were discovered on review of the full text.

A total of 89 studies were included in the final review. All studies were compiled and reported in Table 1. This table has been expanded in supplemental Table 1 to contain more information about studies included in this review. Figure 1 provides a graphical illustration of our review.

Table 1 List of Included Studies

Figure 1 Study selection flowchart for the structured review of Charles Bonnet Syndrome (CBS). A total of 1,582 records were identified through database searches (PubMed, Embase, Web of Science, Scopus). After removing duplicates and non-English articles, 718 records remained for title and abstract screening. Of these, 605 were excluded based on predefined criteria, including irrelevance to CBS, non-visual hallucinations, and lack of peer review. A full-text review was conducted on 114 articles, with an additional 24 excluded due to inadequate data, non-peer-reviewed status, or duplication. A final total of 89 studies were included in the structured review.

Results

Prevalence Patterns and Demographic Risk Factors

CBS prevalence varies widely depending on the population, underlying pathology, and diagnostic criteria used. A meta-analysis suggested an average prevalence between 10% and 15% among patients with visual impairment.³⁶ Generally, the likelihood increases with the severity of visual deficits, increasing age, and social isolation.^12,17 CBS is more frequently reported among women and in older adults (7th–8th decade), likely reflecting the higher prevalence of AMD and glaucoma in this age group.^2,33,51,82 Prevalence for all ophthalmic pathology is 0.4%.⁸⁶ Approximately 14–20% of all individuals with a vision impairment will develop CBS, with AMD reported as the most frequently associated ocular pathology. However, prevalence estimates vary considerably depending on the diagnostic criteria applied, underscoring the challenge of establishing a consistent case definition.^28,34

High-Risk Groups and Condition-Specific Prevalence

CBS most commonly occurs in populations with significant bilateral vision loss but can occur in unilateral visual field loss. Late-stage AMD patients are consistently identified as a high-risk group, with prevalence rates of up to 27% when better-eye visual acuity falls below 20/120 (6/36), while neovascular AMD cohorts demonstrate a prevalence of around 9%.^29,33 Low-vision patients, particularly those over age 40, show an overall prevalence of ~19.7%, with increased risk in patients with a visual acuity below 20/60.^51,92 Patients receiving intravitreal anti-Vascular Endothelial Growth Factor (VEGF) therapy have a reported prevalence of 6.6%, and poor visual acuity and contrast sensitivity identified as key risk factors like all other patient populations.⁷⁸ In glaucoma populations, CBS in open-angle glaucoma patients with visual field deficits show prevalence rates ranging from 7.1% to 20.1% depending on the population screened.^77,83 Inherited retinal diseases such as retinitis pigmentosa have been shown to be at risk but specific prevalence at this point have not been reported. Non-ocular pathologies such as visual cortex damage due to strokes have been shown to be a significant risk factor for the development of CBS though prevalence has not been reported or quantified.^20,23,73 Overall, populations at risk include patients with bilateral visual field/acuity loss such as AMD (Dry and neovascular), advanced glaucoma, DR, strokes, and congenital retinal conditions.

Condition-Specific Associations and Risk Profiles

Age-Related Macular Degeneration: The Primary Risk Group

Among the ocular pathologies linked to CBS, AMD has been most extensively studied, with reported prevalence ranging from 10% to 30%.^2,29 Several studies report a prevalence of CBS in AMD patients ranging from 10% to 30%.^33,49,82 With patients showing end stage AMD, geographic atrophy, or neovascular AMD showing increased susceptibility to CBS.⁹¹

Studies investigating the relationship between visual acuity and the risk of developing CBS in patients with AMD have resulted in mixed findings. With some studies reporting that diminished visual acuity or visual field loss either independently or combined does not reliably predict the likelihood of developing CBS.¹² Other studies show that specific visual acuity thresholds may be associated with increased risk. Khan et al’s case–control study showed that visual acuity worse than 20/120 in the better seeing eye was significantly associated with an increased risk of CBS (OR 3.5).³³ Other studies have shown that bilateral visual acuity of 20/60 is also associated with an increased risk of CBS.⁸²

Glaucoma: Underrecognized but Clinically Relevant Risk

CBS has been less frequently reported in glaucoma compared to AMD. Reported prevalence of CBS in glaucoma patients was reported to be between 2% and 5%.⁴⁶

Diabetic Retinopathy: CBS Risk in Bilateral Central Vision Loss

Patients with diabetic retinopathy (DR) can develop CBS, especially if patients have bilateral vision deficits. Overall prevalence was lower than in AMD, prevalence was between 2% and 10%, with an increased risk of CBS with macular edema and neovascularization leading to central vision loss.^16,78

Other Etiologies: Retinal, Optic, and Cortical Pathways to CBS

CBS has also been reported in association with optic neuropathies, retinal detachments, and inherited retinal diseases such as retinitis pigmentosa.⁹³ Strokes leading to cortical visual impairment have also been documented as a cause of CBS, and data on prevalence in this population are limited.^20,67,92 The main feature across all these other conditions is significant loss of visual input to the visual cortex, while most bilateral optic neuropathies have been shown to have monocular CBS. Table 2 presents a summary of these CBS prevalence results.

Table 2 Summary of CBS Prevalence, Risk Factors, and Demographic Trends Across Vision-Impaired Populations

Screening Tools and Diagnostic Practices in CBS Research

We have identified two screening tools that are formally validated and used in multiple studies, namely the North-East Visual Hallucination Interview (NEVHI),³² and the Questionnaire de Repérage du Syndrome de Charles Bonnet (QR-SCB).⁶⁵ Additional screening tools found include one created by Vukicevic and Fitzmaurice,³⁵ which has not been formally validated, and one created by Shirashi et al,²⁶ which was validated by the study authors, however, is not routinely used in ophthalmologic research and only contains one question specific to CBS. The NEVHI was created by Mosimann et al in 2008 and is a semi-structured interview designed to assess the phenomenology of hallucinations, emotional response of patients, temporal characteristics, and cognitive insight in older patients with visual or cognitive impairment. It has good face, content, and criteria validity with strong inter-rater reliability (Kappa 0.72–0.83), but requires a trained interviewer.³² The QR-SCB, which was developed by Cantin et al in 2009, is a self-administered, 55-item questionnaire that can be used by low vision patients and offers a structured algorithm for screening. The sensitivity was found to be 1.00 with a sensitivity of 0.77 in the validation study, however it was only validated for use in french-speaking populations and relies on patient self-report which can be affected by the cognitive status of the patient.⁶⁵ A major advantage of this approach is that it can be completed without a trained interviewer, enhancing its clinical utility. The original validation of the NEVHI did not provide an estimated elapsed time of the interview; however, the length of administration is likely to cause more disruption to clinic flow than the QR-SCB. The NEVHI consists of 3 sections, the first of which includes 4 binaries, ie yes/no, questions that require patient elaboration. The subsequent two sections include 4 multiple choice questions delineating the temporal aspects of the hallucination, and 9 questions where patients must respond using a 1–5 Likert scale. Providers can be adequately trained to administer this standardized interview, however it would require the patient to be in an appropriate setting, ie a clinic room, for administration. Conversely, the QR-SCB often took between 15 and 45 minutes for administration; however, does not require a trained interviewer, and can be filled out while the patient is waiting to be roomed, provided they have a positive affirmation to the initial screening question. This is less likely to disrupt the clinic flow substantially and is able to be administered even in busy clinics. The characteristics of each of these tools have been characterized graphically in Table 3.

Table 3 Diagnostic Features, Strengths, and Limitations of Validated Charles Bonnet Syndrome Screening Instruments

Overall, of these tools, the NEVHI offers the most depth regarding evaluated domains and is great for use in specialist settings or for research, however the brevity of the QR-SCB allows for more rapid assessment and is a more attractive option for clinical settings. It has been previously adapted for use in English-speaking patients.^78,84

For our investigation into screening and diagnostic methods, we examined observational studies that either prospectively or retrospectively screened patients for CBS. Observational studies that recruited based on patient reported or documented CBS were not used for this portion. Several trends were discovered while reviewing the identified observational studies. The final results were tabulated and added to Table 4. Chief among these includes the considerable heterogeneity in overall screening approach and an underutilization of validated CBS screening tools.

Table 4 Summary of Studies Assessing Charles Bonnet Syndrome: Diagnostic Criteria, Screening Tools, and Hallucinatory Domains

Figure 2 Clinical workflow for screening, assessment, and management of Charles Bonnet Syndrome (CBS). This clinical algorithm presents a structured approach to identifying and managing CBS in ophthalmology clinics. Clinicians screen patients with risk factors such as AMD, glaucoma, or stroke using a direct question (eg, “Have you seen things others cannot see?”). If positive, they apply a validated tool like the QR-SCB. They then assess cognition and psychiatric history to rule out alternative causes. If needed, they use the NEVHI for further characterization. Management includes education, reassurance, and referral for visual or psychosocial rehabilitation when appropriate.

Screening approaches varied among studies with the most popular being structured, non-validated interviews alone (49% of studies 30/61). Customized questionnaires alone were used in 28% of studies (17/61). A combination of customized questionnaires and interviews were used in 5% of studies (3/61). While the majority of studies relied on self-reporting of visual hallucinations or medical history (52%, 32/61), 34% (21/61) used additional tools such as the Mini-Mental State Examination (MMSE), Mini-Mental State Examination, Blind Version (MMSE-Blind), or other tools to rule out cognitive or psychiatric comorbidities that could explain the hallucinations. Approximately 10% (6/61) of studies employed formal specialist evaluations to aid in the diagnosis and rule out potential confounding diagnoses, through structured examination. Two of the studies (3%, 2/61) used unclear methods that were not touched upon in appreciable detail.

Validated screening tools were underutilized, which was a prominent trend identified. In total, validated CBS-specific screening tools were used in approximately 11% of studies (7/61). Excluding all studies prior to the introduction of validated CBS-specific screening tools mentioned, ie studies published after 2009, only 20% (7/35) of studies used validated instruments. Most studies relied on structured or semi-structured interviews that were created by study authors.

These findings suggest adoption of a systematic approach to CBS screening and diagnostics would be beneficial. The lack of universally accepted screening and diagnostic methods likely increases the risk of underdiagnosis of CBS patients. Additionally, the use of non-standardized methods in research has the risk of significantly impacting validity.

Barriers to Diagnosis: Systemic, Clinical, and Psychosocial Obstacles to Recognizing Charles Bonnet Syndrome

During our review, it was noted that CBS is underdiagnosed and underreported among many patients experiencing symptoms. This can be explained by a lack of awareness of CBS among healthcare providers and patients, patient reluctance to report symptoms, misdiagnosis or underreporting, contextual factors, insufficient screening tools, and misperceptions about the clinical significance of CBS. Multiple patient, provider, and system-level barriers contribute to this diagnostic gap.

Familiarity of CBS among healthcare professionals remains low, a contributing factor being lack of thorough education about the condition in medical training.⁶⁰ In a random sampling of Family Practice physicians across Canada, over 50% (N = 4856) were completely unaware of the condition.⁶⁰ This demonstrates a significant lack of awareness among physicians, thus leading to underdiagnosis of CBS.

There is a reluctance of patients to disclose symptoms of visual hallucinations due to fear of stigma or misinterpretation. A qualitative study of experiences of children living with CBS showed that there was significant disruption to their daily lives, with some hallucinations being described as “creepy creatures” which led to fear of being seen as mentally ill.⁷² It was also noted in a study of CBS in patients with retinitis pigmentosa that many individuals reported symptoms only after being asked specifically about hallucinations; they did not self-report even though emotional distress was associated.⁴⁸ In a cross-sectional survey of 1077 patients from a tertiary ophthalmology clinic in Singapore, 4 met criteria for CBS, but only 1 of the 4 patients discussed symptoms with their doctor.²⁵ It has also been noted in a survey of one Portuguese population that many patients with CBS lived alone and did not disclose their hallucinations to anyone, leading to further emotional distress,⁸² and indicates that the number of cases of CBS is likely underreported. There is concern over psychiatric labeling and stigma that occasionally prevents patients from seeking the necessary care and revealing their symptoms to physicians.

CBS symptoms are often misclassified, as there are a multitude of psychiatric and neurological conditions that present similarly. One prospective study also notes a possible higher risk of dementia in patients with CBS,⁵⁶ emphasizing that there may be clinical overlap with cognitive or psychiatric conditions that make it difficult to identify if CBS is occuring. A study among Asian patients at a tertiary ophthalmic center showed a CBS prevalence rate of 0.4%, with only one of the four CBS patients discussing their symptoms with the doctor and subsequently being incorrectly diagnosed with another condition.²⁵ Misdiagnosis is another contributing factor to a reduced quality of life in these individuals, as the condition being unrecognized continues to go unmanaged.

Another diagnostic barrier is the lack of adequate, regular screening for CBS in ophthalmic offices. As discussed in a study that found that one-third of patients with retinitis pigmentosa experienced hallucinations characteristic of CBS, many did not report their symptoms.⁴⁸ Not only are screenings not incorporated into the typical workup of low vision patients but many of the standard assessments historically performed failed to elicit hallucination history, highlighting the need for structured tools to survey for CBS existence.³² The high prevalence of CBS in individuals with low-vision indicates the need for routine screening with effective tools incorporated into the clinical workflow.

CBS is often viewed as a benign condition, which leads to diagnostic complacency. A diagnosis of CBS can have a significant social and emotional impact on a patient, and dismissing it as benign can prevent proper support and early management.⁴⁶ One survey of 4000 ophthalmic patients identified 492 individuals with CBS, and of those it was reported that CBS persists for 5 years or more in 75% of the sample, causing distress and reducing quality of life reported by 32% of the patients (N = 492).⁴⁶

Individuals with or at risk for CBS undergo multiple barriers to a proper diagnosis, including variance in physician understanding, patient reluctance and fear of reporting due to stigma of symptoms, overlap of symptoms with other conditions, and lack of regularly used screening tools – all of which can lead to a decreased quality of life for patients. It is important to recognize these obstacles in order to understand the importance of identifying a standardized pathway for patients to be properly screened for CBS and promptly provide appropriate management and support.

Implementing a Stepwise Screening and Management Pathway for Charles Bonnet Syndrome

Based on the information gathered, we have devised a clinical pathway that can easily be adapted to ophthalmology clinics to screen for CBS in a practical and effective manner. The first portion of the screening pathway requires the identification of at risk groups. This pathway could potentially be universally applied to low vision clinics where the prevalence rate of CBS is expected to be as high as 18.8%,⁵² and selectively applied in general ophthalmology clinics where the positive predictive value is likely to be lower given the lower number of cases.

Identifying High-Risk Patients in Ophthalmology Clinics

CBS predominantly affects individuals that have bilateral visual impairment but can also occur in those with unilateral field loss. Therefore, patients in clinics with unilateral field loss should be screened for CBS as there have been cases reported. In multiple studies, the male-to-female ratio has been very close to 1:1.⁸⁷ Given the roughly equal distribution between genders, gender alone should be a significant criteria for determining which patients to screen for CBS. Pathologies that increase the risk include patients with bilateral visual impairment due to AMD, glaucoma, DR, stroke, and congenital retinal disorders. AMD is the most frequent ocular pathology associated with CBS, with several studies reporting a prevalence of CBS in AMD patients ranging from 10% to 30%.^{2,12,13,18,26} In low vision patients aged over 40, prevalence stands at around 19.7%, with increased risk in patients with visual acuity below 20/60.⁶⁸ Glaucoma patients, particularly those with open-angle glaucoma and visual field deficits have shown a prevalence ranging from 7.1% to 20.1%.^21,77 In general, CBS is more commonly associated with older adults, but there have been cohorts having an average age of 39.4 years.⁹⁵ Overall, populations most at risk include patients with bilateral visual field loss from AMD (wet and dry), glaucoma, DR, cortical lesions, and congenital retinal diseases. Therefore, patients with complete unilateral visual loss or underlying visual field loss with an ongoing pathology such as AMD have an increased risk of developing CBS and therefore should be considered for screening.

Once populations are identified, patients with these characteristics can be further assessed for CBS symptoms. Based on current evidence, the initial screening question for CBS can be effectively incorporated into clinical intake forms. One consideration to keep in mind is the reluctance of patients to report CBS diagnosis given the possibility of being labelled as mentally ill, therefore it is imperative to structure the question in such a way to encourage disclosure of visual hallucinations by ensuring the patient it is a normal phenomenon in patients with low vision. One specific screening question used commonly is the question posed by Holroyd et al.¹² This question is both sensitive and provides a patient-centered approach in screening for CBS: When people have trouble with their eyes, it frequently affects their vision. It may make it difficult to see things that are there, but sometimes people see things that are really not there or see things that other people do not see. Has this ever happened to you?

Including this question on intake paperwork can allow for an unobtrusive identification of patients who may be experiencing CBS symptoms without the associated label of a psychiatric or neurological diagnosis. Additionally, it is important for ophthalmologists and other medical professionals to educate patients as a potential outcome of low vision given the potential lack of awareness among certain patient populations, ie glaucoma patients, regarding CBS.⁶⁹

Patients that respond positively to this question can then undergo a more rigorous, structured assessment using one of the available CBS-specific screening tools. The two major validated tools that currently exist include the NEVHI and the QR-SCB which have been discussed previously. Given the ease of administration, we believe that the QR-SCB may be a more clinically useful option for routine ophthalmologic assessments, though the NEVHI may provide a more comprehensive assessment in cases where the symptoms or diagnosis are unclear due to the inclusion of open-ended questions that take into account patient descriptions of hallucinatory activity. This tool may provide more detailed information into the patient’s visual hallucinations, which is time intensive, however may yield more valuable diagnostic information in certain cases. These should both be used in specific cases based on clinical judgement.

In addition to the QR-SCB, the use of a validated measure of cognition can also be employed. The most commonly used screening tool includes the MMSE or the MMSE-Blind. In patients with significant visual impairment, the MMSE-Blind may be a better assessment as low vision could potentially be a confounder with the standard MMSE.⁹⁶ If there is further uncertainty about the patient’s cognition of psychiatric history, it may be appropriate to seek a referral from a psychiatrist or neuro-ophthalmologist to rule out any potentially confounding diagnoses through a full neuropsychiatric assessment. Additionally, special consideration should be paid to patients on certain medications, namely dopaminergic, anticholinergic, certain antibiotics, benzodiazepines or sedative-hypnotics, opioids, steroids, or recreational drugs, which can potentially lead to visual hallucinations and can complicate the diagnosis of CBS. Clinicians should use clinical judgement to ascertain whether the patient’s stated symptoms are secondary to another cause or secondary to their visual loss, and expert opinion is warranted if there is further uncertainty.

Following the confirmation of CBS, education about the condition is essential for patients. Education should be centered around the benign nature of the syndrome and clinicians should emphasize that this is a well-recognized and common sequelae of visual impairment and not indicative of psychiatric disease. Additionally, it is important for clinicians to assess the degree of functional impairment in patients with CBS symptoms. If there is significant disturbance of daily activities, significant distress, or emotional consequences, patients should be referred for appropriate visual rehabilitation or psychological support.

We believe this structured, stepwise approach to CBS screening, beginning with a simple intake question, followed by the use of a validated screening tool, patient education, assessment of functional impairment, and the use of available visual support services, will significantly improve outcomes for patients, greatly reduce misdiagnosis, and help integrate CBS care seamlessly into routine ophthalmological clinical practice. A visual representation of this clinical pathway is depicted in Figure 2.

Discussion

Limitations

The aims of this study were to delineate the currently validated screening tools for CBS and to propose a standardized clinical guideline that can be integrated into practice with minimal disruption to efficiency. Our review identified several available screening tools; however, to our knowledge, no specific screening pathway incorporating validated tools has previously been suggested for CBS. This highlights an important gap in the literature. By outlining a pathway that leverages validated tools, our work directly addresses the diagnostic challenges of CBS. The heterogeneity in prevalence estimates and lack of standardized criteria have historically led to underrecognition and misdiagnosis, often as psychiatric disease. Our proposed framework eases diagnosis by providing a structured sequence: first identifying high-risk populations, then incorporating sensitive intake questions, and finally applying validated screening instruments when appropriate. This stepwise method allows ophthalmologists to differentiate CBS from psychiatric or neurologic conditions, facilitates earlier recognition, and enables timely patient education and referral for supportive care. In this way, our review contributes not only to greater consistency in research but also to practical improvements in day-to-day clinical diagnosis.

While our proposed framework offers a pragmatic approach to CBS recognition, several important limitations must be acknowledged.

The most significant limitation of our research, as previously mentioned, is considerable heterogeneity in diagnostic criteria used throughout the literature. As highlighted by Hamedani and Pelak,⁸ there is no universally agreed-upon criteria that exists regarding key diagnostic features of CBS. Specifically touched upon by Hamedani and Palek, there is no consensus regarding the degree of vision loss, the nature of hallucinations (simple vs complex), the necessity of preserved cognitive function nor are there standardized methods for excluding neuropsychiatric disorders. Some studies have accepted minimal visual loss as sufficient for a diagnosis, while other studies have required severe vision loss. In a similar vein, the degree of insight required for patients varies greatly across the literature. This level of heterogeneity is a complicating factor for systematic case identification and the appropriate selection of screening thresholds in clinical practice. Studies using more strict criteria are likely to underreport the prevalence of CBS, while studies that use less strict criteria are likely to overreport the prevalence of CBS. Without the creation of standardized criteria, there is a large risk of overdiagnosis and underdiagnosis in clinical practice depending on the criteria used.

Additional limitations that exist in the present study include the underdevelopment of the validated CBS-specific screening tools. Unfortunately, the NEVHI and the QR-SCB were not systematically validated across large, diverse patient populations, and thus their diagnostic utility, sensitivity, and specificity in routine ophthalmologic settings is not completely delineated.

It should also be noted that previous studies have also shown that cultural differences play a role in the underreporting of hallucinations, likely due to social stigma, which is an important consideration when dealing with CBS patients of diverse cultural or ethnic backgrounds.^97,98

Addressing these limitations will require continued study of CBS to generate a broader consensus regarding the threshold for diagnosis and careful validation and refinement of screening tools. Through addressing these limitations, we can improve our certainty of CBS diagnosis and help patients get much-needed education and support in a systematic and timely manner.

Future Directions

Future endeavors to improve recognition and management of CBS will need to focus on critical weaknesses in the existing clinical approach. There is a definite need for the development of large-scale, rigorously validated CBS screening instruments that can be practically applied in ophthalmology clinics. While current tools exist, such as the NEVHI and the QR-SCB, these tools lack large-scale validation and have aspects that make them less clinically useful in the setting of an ophthalmology clinic. They offer a good foundation for future researchers to devise more abbreviated screening tools that can be systematically validated in a large population to ensure the sensitivity, specificity, and the feasibility.

Another important weakness to address is the lack of universally applicable diagnostic criteria for CBS. As mentioned previously, there is a great deal of heterogeneity throughout the literature regarding the diagnostic criteria used to confirm CBS. Specifically, there is variability regarding the degree of vision loss required, the phenomenology of the hallucinations, necessity of insight into the hallucinations, and our ability to diagnose this condition in patients who have comorbid and confounding neurologic or psychiatric disease. Future efforts should be made by researchers to establish a singular diagnostic definition of CBS for use in research and clinical practice.

There is also a need for longitudinal studies, which can characterize the natural history of CBS and give clinicians a better understanding of the factors underlying persistent symptoms, resolution, or psychiatric comorbidities that are exacerbated by CBS. This would be a great benefit for risk stratification and implementation of management strategies.

Finally, the development of structured clinical pathways that include a standardized approach to psychological support and visual rehabilitation would be an appropriate extension of our current research and may help to improve the lives of those living with distressing visual hallucinations due to vision loss.

We believe that further research into these areas can potentially transform CBS from something underdiagnosed and misunderstood aspect of visual care into a routinely recognized and expertly managed aspect of visual care.

Conclusion

CBS remains a frequently overlooked diagnosis among patients with significant visual impairment. Despite being benign, it can profoundly affect quality of life. Underreporting by patients, limited clinician familiarity, and the lack of standardized diagnostic criteria have all contributed to persistent underdiagnosis. As the burden of vision loss increases with an aging population, systematic and practical screening approaches that can be integrated into routine care are increasingly necessary.

This review highlights the importance of structured screening for CBS and proposes a pragmatic diagnostic framework that can be incorporated into routine ophthalmologic practice. By streamlining the identification of at-risk patients, encouraging disclosure through sensitive screening questions, and recommending validated tools for confirmation, this framework directly eases the diagnostic process. Such an approach facilitates earlier and more accurate recognition, reduces misdiagnosis as psychiatric illness, minimizes unnecessary referrals, and ensures patients receive appropriate education and rehabilitative resources. Future efforts should focus on validating this framework across diverse clinical settings, refining tools for diagnostic accuracy, and developing consensus diagnostic criteria to establish CBS as a routinely considered component of comprehensive vision care.