Retinal Nerve Fiber Layer Diagnostic Parameter
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Solution Overview
Problem
Current ophthalmic diagnostic techniques for measuring retinal nerve fiber layer (RNFL) thickness are prone to errors due to variations in measurement loci position relative to the optic disc, reducing sensitivity in detecting abnormalities.
Innovation Solution
A diagnostic parameter that accounts for the product of local RNFL thickness and the distance of the measurement locus from a base point, providing high sensitivity while being weakly dependent on position, allowing for accurate characterization of RNFL abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RNFL thickness is measured at fixed loci relative to the optic disc center, then measurement precision is improved, but sensitivity to positional errors increases
Solution Approach 1:
The patent transforms the measurement parameter from raw RNFL thickness to a normalized value that accounts for positional variations. By introducing a normalization factor based on the distance from the optic disc center and the angular position, the measurement becomes invariant to small positioning errors, thus resolving the contradiction between measurement precision and diagnostic reliability
Solution Approach 2:
The patent introduces an intermediary normalization process that mediates between the raw thickness measurement and the final diagnostic value. This intermediary step compensates for positional deviations by scaling the measurement according to the actual location relative to the optic disc, thereby maintaining reliability while preserving measurement precision
2Stability of the object's composition
If measurement loci are positioned at a fixed radius from the optic disc center, then measurement consistency is improved, but sensitivity to center localization errors increases
Solution Approach 1:
The patent changes the measurement approach by normalizing the RNFL thickness with respect to the radial distance from the optic disc center. This parameter transformation makes the measurement less sensitive to small deviations in the fixed radius positioning, thus maintaining loci consistency while improving measurement precision
Solution Approach 2:
The patent performs preliminary normalization of the thickness measurements based on the expected radial profile of RNFL thickness. By pre-compensating for the geometric effects of radial positioning, the method reduces the impact of center localization errors on the final measurement precision
3Difficulty of detecting and measuring
If local RNFL thickness is used as the diagnostic parameter, then detection sensitivity to abnormalities is improved, but sensitivity to positional errors increases
Solution Approach 1:
The patent transforms the diagnostic parameter from local RNFL thickness to a normalized thickness value that incorporates positional information. This parameter change maintains the ability to detect abnormalities (since true pathological thinning is preserved) while reducing sensitivity to positional errors through the normalization factor
Solution Approach 2:
The patent implements a feedback mechanism where the measured position and thickness are used to compute a normalization factor that feeds back into the diagnostic parameter. This feedback loop compensates for positional deviations, maintaining diagnostic accuracy while preserving abnormality detection sensitivity
Data Source
AI summary
Disclosed are method and apparatus for characterizing the retinal nerve fiber layer (RNFL). An advantageous diagnostic parameter for characterizing the RNFL is a function of the product of the local RNFL thickness at a measurement locus×the distance of the measurement locus from a base point. The value of the diagnostic parameter in a patient's retina is compared to a corresponding reference range acquired from a population of healthy retinas.