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Per O. Lundmark, Tove Lise Morisbakk, Rigmor C. Baraas; Effect of Ocular Accommodation on Thickness Measurements of the Parapapillary Retina Obtained with Spectral Domain OCT. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5087.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of ocular accommodation on measurements of retinal- and nerve fiber layer thickness (NFLT) in the parapapillary area obtained with spectral domain OCT (SD-OCT).
Included were 20 healthy young volunteers with ametropia < ± 6 DS, < 1 DC, visual acuity >0.0 logMAR, and accommodation amplitude > 8 D. Repeated circular scans (1536 A-scans/B-scan, 2-16 frames) centered at the papilla were obtained from the left eye with SD-OCT (SpectralisTM, Heidelberg Engineering), while the subject used the right eye to fixate on a logMAR chart at 5 m, 50 cm, 25 cm and 16.7 cm. All scans were performed on the same day by one experienced operator. Concurrent measurements of the accommodative effort were obtained from the right eye with a power refractor (PowerRef II, Plusoptix). Average- and pointwise thickness measurements were obtained from 6 sectors using the built in analysis software (Heyex v.4.0), as well as by analysis of the longitudinal reflectivity profile (LRP) of exported images. Measurements of accommodation were averaged for 1 sec. starting at 0.4 sec. before the recorded OCT scan. The effect of accommodation was analyzed by Pearson correlation (r) and linear regression where accommodation- and thickness measurements relative to individual baselines at 5 m were entered as independent and dependent variables, respectively.
Relative accommodation (RA) was 0.0 ± 0.1, -1.0 ± 0.6, -2.4 ± 0.7, and -4.6 ± 1.1 D for fixation at 5 m, 50 cm, 25 cm, and 16.7 cm, respectively. Regression analyses (n = 11) based on average thickness showed a weak but significant negative correlations between RA and NFLT in superior- and nasal sectors, with strongest correlations in the supra-temporal and nasal sector (r = 0.18, p = 0.016 and r = 0.18, p = 0.017, respectively).
Preliminary results indicate that accommodative efforts during SD-OCT measurements may result in a slight thinning effect on averaged parapapillary NFLT measurements. Further analyses will investigate the effect on average retinal- and pointwise thickness measurements with LRP.
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