Summary for the Clinician

■As in other imaging modalities, artifacts are fairly common with OCT.

■Artifacts can be divided into acquisition and interpretation artifacts.

■A good image is an important determinant in avoiding artifacts; however, good signal strength does not assure a reliable OCT analysis and the clinician should look for any disparity in the report, as the Stratus® software version 4.0 and above can identify the presence of artifacts.

■Retinal thickness measurements depend on automated segmentation algorithms that place a line along the inner retinal boundary and another line along the outer retinal boundary. In cases where the normal anatomy is altered, the expertise of the examiner plays a major role in the correct positioning of the line scan.

■Interpretation of OCT topographic maps should always include examination of the cross-sectional OCT scans.

■The retinal thickness measurement differences between the Spectralis®, Cirrus®, and Stratus® vary depending on the specific pathological process that is being imaged.

1.4  Conclusion

Although errors are common in the image analysis of the Stratus® OCT, the current software version 4.0 can detect and warn of their presence. The examiner must search for any incongruent information. In many pathologies, the information of the OCT images is very useful; however, images of entities with alterations of the RPE morphology are best evaluated without any analysis protocol. Spectral-domain OCT has overcome many of the weaknesses encountered with the Stratus® OCT such as fixation dependence, small scanned area, and thickness measurements, but Stratus® OCT can still be a valuable tool in the daily clinical practice if the examiner is aware of its normal functioning and pitfalls. Finally, one must not forget that despite all the advantages of the spectraldomain OCT, it can also give erroneous information. As with any other medical imaging modality, the OCT results have to be correlated with the clinical condition of the patient.

References 9

References

 1. Huang D, Swanson EA, Lin CP et al (1991) Optical coherence tomography. Science 254:1178–1181

 2. Hee MR, Izatt JA, Swanson EA et al (1995) Optical coherence tomography of the human retina. Arch Ophthalmol 113:325–332

 3. Puliafito CA, Hee MR, Lin CP et al (1995) Imaging of macular­ diseases with optical coherence tomography. Ophthalmology 102:217–229

 4. Costa RA, Calucci D, Skaf M et al (2004) Optical coherence tomography 3: automatic delineation of the outer neural retinal boundary and its influence on retinal thickness measurements. Invest Ophthalmol Vis Sci 45: 2399–2406

 5. Pons ME, Garcia-Valenzuela E (2005) Redefining the limit of the outer retina in optical coherence tomography scans. Ophthalmology 112:1079–1085

 6. Sadda SR, Joeres S, Wu Z et al (2007) Error correction and quantitative subanalysis of optical coherence tomography data using computer-assisted grading. Invest Ophthalmol Vis Sci 48:839–848

 7. Kaluzny JJ, Szkulmowska A, Bajraszewski T et al (2007) Retinal imaging by spectral optical coherence tomography. Eur J Ophthalmol 17:238–245

 8. Wojtkowski M, Bajraszewski T, Gorczynska I et al (2004) Ophthalmic imaging by spectral optical coherence tomography. Am J Ophthalmol 138:412–419

 9. Wojtkowski M, Srinivasan V, Fujimoto JG et al (2005) Threedimensional retinal imaging with high-speed ultrahigh-­

resolution optical coherence tomography. Ophthalmology 112:1734–1746

10.Browning DJ, McOwen MD, Bowen RM Jr, O’Marah TL (2004) Comparison of the clinical diagnosis of diabetic macular edema with diagnosis by optical coherence tomography. Ophthalmology 111:712–715

11.Azzolini C, Patelli F, Brancato R (2001) Correlation between optical coherence tomography data and biomicroscopic interpretation of idiopathic macular hole. Am J Ophthalmol 132:348–355

12.Chan A, Duker JS, Schuman JS, Fujimoto JG (2004) Stage 0 macular holes: observations by optical coherence tomography. Ophthalmology 111:2027–2032

13.Ray R, Stinnett SS, Jaffe GJ (2005) Evaluation of image artifact produced by optical coherence tomography of retinal pathology. Am J Ophthalmol 139:18–29

14.Sadda SR, Wu Z, Walsh AC et al (2006) Errors in retinal thickness measurements obtained by optical coherence tomography. Ophthalmology 113:285–293

15.Hee MR (2005) Artifacts in optical coherence tomography topographic maps. Am J Ophthalmol 139:154–155

16.Hee MR, Puliafito CA, Duker JS et al (1998) Topography of diabetic macular edema with optical coherence tomography. Ophthalmology 105:360–370

17.Srinivasan VJ, Wojtkowski M, Witkin AJ et al (2006)

1  ­High-definition and 3-dimensional imaging of macular ­pathologies with high-speed ultrahigh-resolution optical coherence tomography. Ophthalmology 113(2054): e2051–2014

18.Han IC, Jaffe GJ (2009) Comparison of spectraland timedomain optical coherence tomography for retinal thickness

measurements in healthy and diseased eyes. Am J Ophthal­ mol 147:847–858, 858 e841

19.Forooghian F, Cukras C, Meyerle CB et al (2008) Evaluation of time domain and spectral domain optical coherence tomography in the measurement of diabetic macular edema. Invest Ophthalmol Vis Sci 49:4290–4296

20.Leung CK, Cheung CY, Weinreb RN et al (2008) Comparison of macular thickness measurements between time domain and spectral domain optical coherence tomography. Invest Ophthalmol Vis Sci 49:4893–4897