OTA Outlines SD-OCT Benefits

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Can spectral-domain optical coherence tomography (SD-OCT) help clinicians detect structural glaucoma­tous damage and the changes associ­ated with the diagnosis of glaucoma? Yes and yes, according to an Academy Ophthalmic Technology Assessment (OTA).¹

“Classic structural changes associ­ated with glaucoma can be detected in the retinal nerve fiber layer, the macula, and the optic nerve with SD-OCT technology,” said Teresa C. Chen, MD, at Harvard Medical School in Boston. She called SD-OCT “a useful tool in the management of glaucoma patients.”

Expansion in knowledge. The literature review began where the previous imaging OTA left off—Feb­ruary 2006—and concluded in April 2018. During that time, 708 articles on the use of SD-OCT to help clinicians detect changes in eyes diagnosed with glaucoma appeared in the literature. Of those, 74 met inclusion criteria, with 2 identified as level I, and 57 as level II. The remaining 15 articles were not used in the analysis.

CONFIRMATION. Radial scan (1A) and corresponding SD-OCT image (1B). In this imaging example, SD-OCT was used to rule out glaucoma in myopic eyes. MRW = minimum rim width; ILM = internal limiting membrane.

Expansion in technology. “Most clinical practices have transitioned from the older 2-D time-domain OCT machines to the newer 3-D SD-OCT machines,” Dr. Chen said. In the stud­ies evaluated in the OTA, the Cirrus High-Definition OCT (Carl Zeiss Med­itec) was the most commonly studied machine, followed by the RTVue-100 (Optovue), the Spectralis SD-OCT (Heidelberg Engineering), and the 3D OCT-1000 and 3D OCT-2000 (Topcon).

Results. “Though different ma­chines have different scan protocols and different software packages, all can detect the same classic pattern of struc­tural changes noted in glaucoma—su­perior and inferior thinning,” said Dr. Chen. Findings from the OTA include the following:

• All instruments were capable of detecting damage to the retinal nerve fiber layer (RNFL), macula, and optic nerve in patients with preperimetric and perimetric glaucoma.
• RNFL was the most commonly stud­ied single parameter, followed by the macula and optic nerve.
• All instruments can detect the same typical pattern of glaucomatous RNFL loss that affects primarily the inferior, inferior temporal, superior, and superi­or temporal regions of the optic nerve.
• The best disc parameters for detect­ing glaucomatous nerve damage are global rim area, inferior rim area, and vertical cup-to-disc ratio.
• Newer reference-plane independent optic nerve parameters may have the same or better detection capability when compared with older reference-plane dependent disc parameters.

Bottom line. The OTA does caution clinicians to be aware of factors that may influence test results, including “testing artifacts, false positives, false negatives, refractive error … and nor­mal aging changes.” But overall, “SD-OCT machines allow for better axial resolutions, faster acquisition speeds, better scan quality, and better repro­ducibility, all of which affords us better information to care for our patients,” Dr. Chen said.

—Miriam Karmel

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1 Chen TC et al. Ophthalmology. 2018;125(11):1817-1827.

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Relevant financial disclosures—Dr. Chen: None.

For full disclosures and the disclosure key, see below.

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