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The relationship between nerve fiber layer and perimetry measurements
Ronald S Harwerth1, Abhiram S Vilupuru, Nalini V Rangaswamy
1College of Optometry, University of Houston, Houston, Texas 77204-2020, USA. rharwerth@uh.edu
Investigative Ophthalmology & Visual Science
|January 26, 2007
Summary
Standard automated perimetry (SAP) and optical coherence tomography (OCT) effectively correlate to measure glaucomatous neuropathy. RNFL thickness is more sensitive for early glaucoma, while perimetry is better for advanced stages.
Area of Science:
- Ophthalmology
- Neuroscience
- Medical Imaging
Background:
- Glaucoma causes retinal ganglion cell (RGC) loss, leading to visual field defects and retinal nerve fiber layer (RNFL) thinning.
- Current methods lack correlation between RGC loss and RNFL thinning in glaucoma.
Purpose of the Study:
- To investigate the relationship between standard automated perimetry (SAP) and optical coherence tomography (OCT) measures of RGCs.
- To correlate SAP visual field defects with OCT measures of RNFL thickness.
Main Methods:
- Developed methods using normal monkey data to estimate neuron counts and map visual field locations to the optic nerve head (ONH).
- Applied these methods to monkeys with experimental glaucoma.
Main Results:
- SAP and OCT data showed close agreement in neuron counts for normal eyes (approx. 1.5 million RGCs and axons).
- Neural loss measurements from subjective (SAP) and objective (OCT) methods correlated highly in early experimental glaucoma.
Conclusions:
- SAP and OCT measures are correlated indicators of glaucomatous neuropathy.
- RNFL thickness is a more sensitive measure for early glaucoma, while perimetry is better for moderate to advanced stages.
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