To determine the frequency and type of optical coherence tomography (OCT) fast macular thickness map (FMTM) scan artifacts, and whether these artifacts depend on patient diagnosis, demographics, and ocular therapy.

Retrospective observational case series.

Records from patients who underwent an ophthalmologic evaluation by a member of the Duke University Eye Center vitreoretinal faculty and had an OCT scan produced by the FMTM protocol between July 7, 2003 and July 31, 2003 were reviewed. The relationships between OCT scan artifacts and ocular diagnosis, ocular treatment, and patient demographics were determined. Logistic regression was used to relate OCT scan artifacts simultaneously with ocular diagnosis and treatment.

Scans from 171 eyes were analyzed. Retinal scan artifacts, though not observed in normal eyes, were identified frequently in eyes with macular pathology (P = .049). Artifacts were observed in 43.2% of all scans, and of these, an erroneous retinal thickness measurement was obtained in 62.2%. Six types of OCT surface map artifacts were observed. Of these, inner and outer retinal misidentification, degraded image artifact, and “off center” artifact were significantly associated with central thickness calculation errors (P < .001). Neovascular age-related macular degeneration (AMD), full-thickness macular hole, and photodynamic therapy were all associated with increased artifact (P = .002, .022, and <.001, respectively).

Optical coherence tomography scan artifacts are seen surprisingly frequently, adversely affect retinal thickness measurements in a high proportion of cases, and are diagnosis-dependent. Recognition of these artifacts will improve retinal thickness measurement accuracy, and will prevent faulty treatment decisions that are based on inaccurate retinal thickness measurements.