Drusen Deposits, Dry Macular Degeneration and OCT Test

With drusen deposits being one of the key signals for the onset of dry macular degeneration, understanding this key signal would provide a better understanding of the eye disease. With dry macular degeneration progressing over a matter of years, patients tend to see a gradual loss of vision as drusen deposits built up. Drusen are small yellow-white deposits that accumulate under the retina of the eye and the presence of drusen can result in a further breakdown of macular tissue that can cause dry macular degeneration to progress into wet macular degeneration.

Scientists have now reported that they have used spectral domain optical coherence tomography (SD-OCT) to automatically calculate the number of drusen and their size in a patients with dry macular degeneration. Traditional OCT machines utilize time domain technology but SD-OCT provides unprecedented simultaneous ultra-high speed scanning with ultra-high resolution of the ophthalmic images produced.

SD-OCT provides for scanning of the entire posterior pole of the retina which is considerably different than traditional OCT which cans the macula with six radial scans and interpolates to account for any data missed between the radial scans. The more comprehnsive visualization of retinal structure provides an opportunity to potentially improve the overall evaluation and treatment of macular degeneration, including wet macular degeneration and dry macular degeneration.

Using new automated algorithms, the total volume or area of all scanned drusen, as well as the proportion of the retinal area affected with drusen in patients with dry macular degeneration could potentially provide a deeper understanding of the macular degeneration disease, and its progression. Understanding more about the drusen area as well as the drusen size is an important indicator of the progression of dry macular degeneration.

This is significant because until now drusen size was used instead of drusen area to determine the severity of dry AMD because a full assessment of the drusen area was not available. SD-OCT may provide a solution to this problem.

The Massachusetts General Hospital, Wellman Center for Photomedicine has developed an experimental SD-OCT machine. Using this new SD-OCT machine, images obtained from three patients with dry macular degeneration were obtained and the new SD-OCT algorithm was employed to determine drusen area, drusen volume and overal proportion of drusen.

The goal in using this new algorithm was to provide understanding as to how SD-OCT could improve the clinical care of dry AMD patients by determining drusen area and volume automatically. SD-OCT technology could potentially provide a more objective and easier classification of the dry macular degeneration, which in turn could help to determine the disease prognosis for some patients.

In the study, the authors concluded that with the new algorithms available because of the SD-OCT technology, the ability to evaluate structural abnormalities in dry AMD would be greatly improved because of a more precise determination of drusen area.