Contrast Sensitivity Chart Segmentation for Disease Differentiation
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Solution Overview
Problem
Current methods for measuring contrast sensitivity in clinical settings are not widely adopted due to the lack of simple and reliable tools, despite its potential in diagnosing and managing ocular diseases like diabetic retinopathy, age-related macular degeneration, and multiple sclerosis, as visual acuity measurements have been the standard.
Innovation Solution
A chart with a grid of elongated rectangles or lattices featuring shaded marks of varying Weber contrast, allowing patients to mark the center of visible marks, with a key for comparison to determine threshold contrast sensitivity, which can be scored electronically or using a tablet computer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visual acuity measurement is used as the standard method, then the measurement process is simple and familiar to clinicians, but it cannot effectively differentiate ocular diseases with similar acuity levels
Solution Approach 1:
The measurement system is segmented into two distinct components: visual acuity assessment and contrast sensitivity assessment. The contrast sensitivity component is further segmented into multiple spatial frequencies (0.5, 1, 2, 4, 8, 16, 32, 64 cycles/degree), allowing clinicians to evaluate different aspects of visual function independently. This segmentation enables disease differentiation without requiring a completely new complex system.
Solution Approach 2:
The contrast sensitivity test chart serves multiple functions: it measures contrast sensitivity across different spatial frequencies, differentiates ocular diseases with similar acuity levels, monitors disease progression, and evaluates treatment effectiveness. By integrating these functions into a single test instrument, the system achieves multi-functionality without proportionally increasing complexity.
2Reliability
If contrast sensitivity measurement is implemented, then disease progression can be monitored more effectively, but the measurement method becomes more complex and less familiar to clinicians
Solution Approach 1:
The invention uses printed test charts that replicate the contrast sensitivity test patterns on paper or card stock, copying the essential features of electronic display-based tests. This allows the complex measurement methodology to be implemented through simple, familiar printed materials that clinicians can use without specialized electronic equipment or training.
Solution Approach 2:
The test charts incorporate multiple spatial frequency parameters (0.5 to 64 cycles/degree) and contrast levels in a systematic arrangement. By encoding these parameter variations into the physical chart design, the system enables comprehensive measurement without requiring complex adjustable equipment, maintaining ease of operation while achieving reliable disease monitoring.
3Measurement precision
If a comprehensive contrast sensitivity chart with multiple spatial frequencies is used, then measurement precision is improved, but the chart complexity and difficulty of interpretation increase
Solution Approach 1:
The comprehensive test is segmented into multiple distinct spatial frequency charts, each containing a limited set of contrast levels appropriate for that specific frequency. This segmentation prevents any single chart from becoming overly complex while ensuring that each individual chart maintains sufficient precision for its specific measurement purpose. The segmented approach allows systematic evaluation across all frequencies without overwhelming the patient or clinician.
Solution Approach 2:
The invention adds the dimension of spatial frequency as a separate organizational axis, rather than combining all contrast levels and frequencies into a single two-dimensional chart. By distributing measurements across multiple frequency-specific charts, the system maintains measurement precision while reducing the complexity and interpretative difficulty of any individual test chart.
Data Source
AI summary
An apparatus and method for evaluating a patient's contrast sensitivity. The apparatus including a table or chart with a plurality of shaded marks printed in cells in the table or chart. The shaded marks printed with a various contrasts with a log of Weber contrast ranging from −0.20 to −2.15. Where a subject marks an observed position of the shaded marks and a key is used to check the observed position against an actual position of the shaded mark to determine a threshold contrast of the subject.