Original article
Enhanced Depth Imaging Spectral-Domain Optical Coherence Tomography

https://doi.org/10.1016/j.ajo.2008.05.032Get rights and content

Purpose

To describe a method to obtain images of the choroid using conventional spectral-domain (SD) optical coherence tomography (OCT) and to evaluate choroidal thickness measurements using these images.

Design

Observational case series.

Methods

The images were obtained by positioning the SD OCT device close enough to the eye to obtain an inverted representation of the fundus in healthy volunteers who did not have pupillary dilation. Seven sections, each comprised of 100 averaged scans, were obtained within a 5- × 15-degree rectangle centered on the fovea. The choroidal thickness under the fovea in each image was measured by independent observers.

Results

The choroidal thickness could be evaluated in every subject's choroidal image. The mean choroidal thickness under the fovea was 318 μm in the right eye and 335 μm in the left eye. The choroidal thickness showed a high correlation in both eyes (r = 0.82; P < .001). The correlation between the measurements performed by the independent observers was highly significant (right eye, r = 0.93; left eye, r = 0.97; P < .001 for both).

Conclusions

This method provides detailed, measurable images from the choroid, a structure that heretofore has been difficult to image in clinical practice.

Section snippets

Derivation of Imaging Technique

In spectral-domain (SD) OCT, the eye is illuminated with light from a broad band source. Backscattered light is combined with that from a reference arm to generate an interference signal. The depth information of the reflective source is frequency encoded: the interferometric signals have a higher frequency with the greater depth of origin. The information from the interferometric fringes is obtained by using a dispersive detector in which a grating is used to spread out the various frequencies

Methods

Volunteers with no known eye disease were used to help evaluate the ability to image and measure the thickness of the choroid. The volunteers were imaged through undilated pupils. The Heidelberg Spectralis, which is capable of providing scanning laser ophthalmoscopic images simultaneously with the OCT, was set to image a 5- × 15-degree rectangle centered on the fovea. This rectangle was scanned with seven sections, and each section had 100 OCT frames averaged. In use, the device was pushed

Results

The mean age of the 17 measured subjects was 33.4 years, with a range of 19 to 54 years. The mean choroidal thickness under the fovea, taken as the mean of the two observers, was 318 μm in the right eye and 335 μm in the left eye. The choroidal thickness showed a high correlation in both eyes (r = 0.82; P < .001). The correlation between the measurements performed by the independent observers was highly significant (right eye, r = 0.93; left eye, r = 0.97; P < .001 for both; Figure 4).

Discussion

This method of imaging the choroid was easy to perform and obtained detailed images of the choroid without the need for pupillary dilation. Because the scanning laser ophthalmoscopic image is available simultaneously, the exact location of the scan is readily known. This potentially allows repeated measurements in groups of individuals to ascertain choroidal thickness parameters in health and disease. In a typical clinical examination, the pupils could be dilated. The mean choroidal thickness

References (10)

There are more references available in the full text version of this article.

Cited by (0)

View full text
Copyright © 2008 Elsevier Inc. All rights reserved.