The assessment and monitoring of the field of binocular single vision remains a crucial aspect of ophthalmological care, yet current clinical practice relies on normative standards established by Feibel \& Roper-Hall in 1974 that present significant limitations for contemporary application. The original study, conducted with a demographically homogeneous Caucasian population in St Louis using only "several" normal individuals, raises concerns regarding its applicability to Asian populations, particularly in Singapore, where ethnic and genetic factors may influence ocular characteristics. The limited sample size significantly increases the likelihood of Type II errors, whilst the temporal gap of over five decades introduces additional concerns regarding population changes, environmental factors, and advances in measurement techniques that have not been incorporated into current normative data. Given these substantial limitations in demographic representation, statistical power, and temporal relevance, there exists a pressing need to establish population-specific normative data for the field of binocular single vision in Singapore's adult population, which would provide more clinically relevant reference values and potentially improve diagnostic accuracy for ocular conditions in the local context.
Age: 21 to 59 years old
Gender: Males or females
Ethnicity: Asian descent.
Mandarin Chinese
Any facial trauma
Any ocular trauma
Any head trauma
Any history of ocular disease
Healthy Individuals
Cohort
Cross-sectional
Field of Binocular Single Vision
Diagnostic testThe intervention involves a single field of binocular single vision assessment using the Takagi MT-325UD Projection Perimeter. Participants undergo binocular testing where they fixate and follow a single round light stimulus as it moves throughout the perimeter bowl. When participants perceive two distinct light stimuli (indicating loss of binocular single vision), they press a buzzer. The orthoptist records these responses and plots the boundaries on a standardised recording sheet to map the participant's field of binocular single vision. This intervention addresses significant limitations of the current gold standard established by Feibel \& Roper-Hall (1974). The original study was conducted with "several" normal individuals (likely fewer than 10 participants) of Caucasian descent in St Louis, Missouri, creating potential issues with statistical power and population applicability. Our study uses a larger, more robust sample size of 32 participants specifically from Singapore's Asian
Field of Binocular Single Vision in Asian population
Establish comprehensive normative range of field of binocular single vision (BSV) specifically for healthy adults in Singapore's population aged 21-59, creating locally relevant reference standards that reflect ethnic, genetic, and contemporary population. BSV is the ability to use both eyes simultaneously and coordinate the slightly different images from each eye into a single, unified, three-dimensional mental percept. The "field of binocular single vision" is the specific area within the overall visual field where this fusion and single vision can be maintained. To measure the field of BSV using Goldmann perimetry, a moving light stimulus is presented while the patient uses both eyes. The test maps the area where the patient can maintain fusion (single vision). The boundary where fusion breaks (and diplopia starts) is plotted across different directions to define the BSV field.
Comparison of current field of binocular single vision gold standard between Caucasian population vs Asian population
Conduct rigorous statistical comparison between newly established Singapore normative values and existing Feibel \& Roper-Hall (1974) standards to quantify differences and determine clinical significance. Current benchmarks are based on a 1974 U.S. study by Feibel \& Roper-Hall that involved fewer than ten Caucasian subjects and no Asian representation. Consequently, clinicians may over- or under-diagnose ocular deviation and fusion deficits in Asian patients. The study validates a modern methodology using the Takagi MT-325UD Projection Perimeter to map BSV fields under standardized conditions.
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