Duration 5min, Q&A 3min
Comparison of Ocular Retinal Imaging Quality Evaluation by Ray Tracing Wavefront Technology and Double-Pass System
To compare the agreement of the ocular modulation transfer function (MTF) measured by double- pass system and ray tracing wavefront technology, analyze the correlations between two MTF results and the subjective visual quality
One hudred and sixty-three subjects (251 eyes) from 30 to 60 years old without any ocular diseases were consecutively enrolled in an epidemiologic field (Handan eye study).
To compare the mean value of subtracted lower order aberration MTF at 5,10,15,20.25,30 (c/d) spatial frequency,, and the area under the MTF curve obtained by double-pass system(OQAS) and iTrace Visual Function Analyzer in 4.0 mm and 6.0 mm pupil size after mydriasis. Bland-Altman analysis were used to compare the agreement of MTF between two instruments. The relevant factors influence the MTF differences were analyzed, the correlations analysis were preformed between two MTF measurement results and subjective visual quality.
Results and Conclusion
The mean value of MTF at 5,10,15,20.25,30 c/d obtained by iTrace/OQAS in 4mm pupil were 0.730±0.138/0.347±0.123,0.431±0.159/0.162±0.086,0.262±0.120/0.072±0.049,0.169±0.078/0.042±0.033,0.118±0.053/0.026±0.022,0.094±0.043/0.017±0.022, and 0.379±0.166/0.313±0.132,0.159±0.087/0.132±0.084,0.089±0.045/0.050±0.041,0.062±0.028/0.026±0.025,0.046±0.021/0.015±0.015,0.039±0.018/0.008±0.009,0.379±0.166/0.313±0.1322 in 6mm pupil. The result of iTrace were all significant higher than OQAS ( P<0.01) in both 4mm and 6mm pupil diameter. There was no correlation between the MTF difference and age, but a negative correlation were found with cylindrical diopter in the 6mm pupil (r=-0.215,p<0.01).The MTF difference decrease while the pupil size increase at all spatial frequency, the area under MTF curve difference in 6mm pupil size were obviously smaller than result in 4mm pupil. Bland-Altman analysis indicated that the agreement of two instruments were poor while the limits of agreement improves in the 6mm pupil diameter; MTF value at all spatial frequency obtained by iTrace and OQAS were negatively related with subjects' LogMAR best corrected visual acuity (P < 0.05, P < 0.01), only the OQAS MTF value were positively correlated with contrast sensitivity at 3, 6, 12, 18 c/d Log values (P < 0.01).
Compared to double-pass system, ray tracing wavefront technology may overestimate ocular optical quality, and the bias become larger when pupil diameter decrease. Double-pass system produces a more reliable retinal image quality description which is better correlated with the subjective visual quality.
[ Keyword ]
modulation transfer function / double-pass system / wavefront aberration / contrast sensitivity / retinal image quality
[ Conflict of Interest ]