From the Guidelines
The best imaging modalities for visualizing the trabecular meshwork are gonioscopy, anterior segment optical coherence tomography (AS-OCT), and ultrasound biomicroscopy (UBM). Gonioscopy remains the gold standard clinical technique, using a special contact lens and slit lamp to directly visualize the angle structures including the trabecular meshwork, as noted in the primary angle-closure disease preferred practice pattern 1. AS-OCT provides high-resolution cross-sectional images of the anterior chamber angle non-invasively, allowing detailed visualization of the trabecular meshwork with the advantage of being quick and comfortable for patients. UBM uses high-frequency ultrasound to penetrate deeper structures and is particularly useful when media opacities prevent adequate visualization with optical methods. For optimal trabecular meshwork assessment, these techniques can be complementary - gonioscopy for direct clinical examination, AS-OCT for detailed structural analysis, and UBM when deeper penetration is needed or when opacities are present. The choice depends on specific clinical questions, with newer technologies like swept-source OCT and OCT angiography offering additional insights into trabecular meshwork structure and function, particularly valuable in glaucoma diagnosis and management.
Some key points to consider when choosing an imaging modality include:
- The ability of the modality to provide detailed visualization of the trabecular meshwork
- The presence of media opacities that may prevent adequate visualization with optical methods
- The need for deeper penetration to assess structures posterior to the iris
- The availability and comfort of the patient with the imaging modality
It's also important to note that the primary angle-closure disease preferred practice pattern 1 and primary open-angle glaucoma preferred practice pattern 1 provide guidance on the use of these imaging modalities in the diagnosis and management of glaucoma.
In terms of specific clinical scenarios, the choice of imaging modality may vary. For example, in cases where there is suspicion of plateau iris configuration or ciliary body abnormalities, UBM may be preferred due to its ability to provide better characterization of these structures compared to AS-OCT 1. However, AS-OCT may be preferred in cases where detailed structural analysis of the anterior chamber angle is needed.
Overall, the choice of imaging modality for visualizing the trabecular meshwork depends on the specific clinical question and the availability of the modality. Gonioscopy, AS-OCT, and UBM are all valuable tools in the assessment of the trabecular meshwork, and their use should be guided by the specific clinical scenario and the needs of the patient.
From the Research
Imaging Modalities for Trabecular Meshwork
The trabecular meshwork can be visualized using various imaging modalities, including:
- High-definition optical coherence tomography (HD-OCT) 2
- Scattering- and polarization-sensitive anterior segment optical coherence tomography (OCT) 3
- Swept source optical coherence tomography (SS-OCT) 4
- Fourier-domain optical coherence tomography 5
- Polarization-sensitive optical coherence tomography (PS-OCT) 6
Comparison of Imaging Modalities
The detection rate of the trabecular meshwork varies among different imaging modalities:
- PS-OCT has the highest detection rate (95.1%) 3
- HD-OCT has a detection rate of 62.2% 2
- SS-OCT allows for measurement of trabecular meshwork width, with a mean width of 710-890 μm in different quadrants of the eye 4
- Fourier-domain optical coherence tomography enables detailed noncontact imaging of the angle and its structures 5
- PS-OCT provides improved visibility of the trabecular meshwork compared to standard-scattering OCT (S-OCT) 6
Advantages and Limitations
Each imaging modality has its advantages and limitations:
- PS-OCT provides tissue-specific contrast and improved visibility of the trabecular meshwork 3, 6
- HD-OCT allows for in vivo visualization of the scleral spur and Schwalbe's line 2
- SS-OCT enables measurement of trabecular meshwork width and assessment of angle parameters 4
- Fourier-domain optical coherence tomography provides detailed imaging of the anterior segment 5
- S-OCT has limited visibility of the trabecular meshwork compared to PS-OCT 6