Ocular oncologists embrace EDI-OCT imaging

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Ocular oncologists are using enhanced depth imaging-optical coherence tomography to identify and learn about choroidal tumors.

By Cheryl Guttman Krader; Reviewed by Carol L. Shields, MD

Philadelphia-Thanks to its high resolution and increased depth of visualization into the choroid, enhanced depth imaging-optical coherence tomography (EDI-OCT) is proving itself to be a valuable tool for diagnosing and understanding a variety of intraocular tumors.

Carol L. Shields, MD, described the EDI-OCT characteristics of six intraocular lesions: choroidal nevus, choroidal melanoma, choroidal metastasis, choroidal lymphoma, congenital hypertrophy of the retinal epithelium (CHRPE), and retinoblastoma.

The information was based on analyses of images obtained using commercially available platforms (Heidelberg Spectralis HRA + OCT, Heidelberg Engineering; iVue, Optovue) in patients seen at the Wills Eye Hospital, Philadelphia. Dr. Shields is co-director of the Ocular Oncology Service, Wills Eye Hospital, and professor of ophthalmology, Thomas Jefferson University, Philadelphia.

Dr. Shields said that on EDI-OCT, a choroidal nevus appears as a “quiet mound” with a gentle contour and smooth surface, often with an overlying cleft between the retina and retinal pigment epithelium (RPE). (Figure 1)

“This cleft might represent chronic subretinal fluid with retracted photoreceptors,” Dr Shields said.

Obtaining suitable images

However, experience with EDI-OCT shows that the technique cannot be used in all patients [Ophthalmolmology. 2012;119:1066-1072]. In a study including 104 eyes, suitable images were obtained in only about half of the patients, Dr. Shields noted.

“Patient cooperation and clear ocular media is important, and so the best patients are younger than 60 years of age with minimal cataract,” she said. “In addition, tumors that are posterior to the equator and <5 mm in diameter seem to be ideal.”

EDI-OCT imaging of choroidal nevi also showed choroidal shadowing in most (94%) as well as choriocapillaris compression (94%), which could be attributed to the tumor’s origin in the outer choroid and inward growth toward the RPE. Detachment of the overlying RPE was seen in 8% of eyes with a choroidal nevus, while photoreceptor loss was observed in 43% of the eyes.

“The EDI-OCT images give us the answer as to why some patients with choroidal nevus have poor vision. This could be due to photoreceptor loss,” Dr. Shields said.

EDI-OCT identified overlying shallow subretinal fluid more often than ophthalmoscopic and ultrasonographic examination, but only in a minority of eyes.

Dr. Shields said that the age of the subretinal fluid can be estimated based on the appearance of the photoreceptors. When subretinal fluid is fresh, the photoreceptors appear shaggy from presumed swelling of the tissue or from macrophages on the posterior retinal surface. As the fluid becomes more longstanding, the photoreceptors take on a stalactite appearance, and when the fluid is very chronic, the photoreceptors completely disappear, leaving a cleft.

Distinguishing the differences

Small choroidal melanomas (≤3mm in thickness) share similarities with choroidal nevi in terms of having a mound shape, choroidal shadowing, and choriocapillaris compression.

However, a study comparing the EDI-OCT features of small choroidal melanomas and choroidal nevi showed three significant differences between the two types of lesions with the melanomas being slightly thicker, more often associated with subretinal fluid, and more often exhibiting subretinal fluid with shaggy photoreceptors [Arch Ophthalmol. 2012;130:850-856]. (Figure 2)

“We believe the shaggy appearance represents swollen photoreceptor tips or lipofuscin-laden macrophages clinging to the underside of the photoreceptors,” she said.

In contrast to the choroidal nevi and choroidal melanomas, choroidal metastases tend to have a subtle “lumpy, bumpy” surface rather than a smooth contour. (Figure 3)

In a series of 31 eyes with choroidal metastases, almost two-thirds had this slightly uneven topography, Dr. Shields noted.

Similar to the nevi and melanomas, the choroidal metastases almost always showed choriocapillaris compression. Photoreceptor loss was also common (64%), as was subretinal fluid (79%), and 7% of eyes with choroidal metastases had debris in the subretinal space.

“With EDI-OCT we can measure the exact thickness of the metastases, and so we can use this technology to follow patient response to therapy,” Dr. Shields said.

Hemangiomas, which can be difficult to see clinically and on ultrasound, could be readily identified in most cases with EDI-OCT, Dr. Shields said.

The hemangiomas also had a dome shape and uniformly smooth contour with overlying subretinal fluid. However, in contrast to the nevi and melanomas, the choriocapillaris and choroidal vessels within the hemangiomas were expanded rather than compressed. Optical shadowing with an indistinct margin and sometimes a small tumor wing into the surrounding tissue was also observed.

Dr. Shields said that choroidal lymphomas showed the most remarkable surface topography on EDI-OCT. The contour of lymphomas varies depending on lesion thickness and can be described using terms relevant to the ocean surface. The thinnest lesions tended to have a flat or “placid” contour, while those measuring about 2 to 3 mm thick were mostly “rippled,” and those that were thicker had a more wavy or “seasick” appearance. (Figure 4)

EDI-OCT characteristics of congenital hypertrophy of RPE were described based on imaging performed in a series of 18 eyes. The studies showed that all of the lesions were flat, associated with photoreceptor loss, and had a normal choroid. A subretinal cleft was seen in about one-third of eyes, and in no case was there subretinal fluid.

Comparing images obtained with time domain and EDI-OCT, Dr. Shields demonstrated how lacunae transmission can be seen much better with the latter technology, and she also showed the 1:1 correlation between the CHRPE margin and area of abnormal photoreceptors.

Images of retinoblastomas were obtained with a portable handheld EDI-OCT instrument. They showed an exophytic mass overlaid with normal retina.

Carol L. Shields, MD

E: carolshields@gmail.com

Dr. Shields has no financial interest in the material she presented.

Figure 1 Choroidal nevus with overlying drusen found on EDI-OCT to have smooth dome-shaped surface and overlying RPE detachment, subretinal cleft, and intraretinal edema.

Figure 2 Choroidal melanoma with subtle subretinal fluid found on EDI-OCT to have smooth dome-shaped surface with optical shadowing and overlying shaggy photoreceptors with subretinal fluid in the foveal region.

Figure 3 Subtle yellow-colored choroidal metastasis with shallow subretinal fluid found on EDI-OCT to have slightly “lumpy bumpy” surface and subretinal fluid in the foveal region.

Figure 4 Choroidal lymphoma appearing as a yellow choroidal mass found on EDI-OCT to have remarkably “wavy” surface topography, termed “seasick” appearance. (Images courtesy of Carol L. Shields, MD)

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