ACCOMMODATIVE RESPONSES TO SIMPLE SINUSOIDAL AND COMPOUND GRATINGS: ROLE OF SPATIAL PHASE

Title ACCOMMODATIVE RESPONSES TO SIMPLE SINUSOIDAL AND COMPOUND GRATINGS: ROLE OF SPATIAL PHASE
Author, Co-Author Pierre Denieul, Ing. opt., Dr. sci. physiq., Hans Brettel, Dr.rer.nat., Dr.med.habil., Francoise Martin-Corno, Ing.opt., Dr.es sci.physiq.
Topic
Year
1992
Day
Monday
Program Number
2:00 pm
Room
Ireland B
Affiliation
Abstract The monocular steady state accommodative response to simple sinusoidal and compound gratings was studied by highly sensitive infrared optometry. In addition to the mean level of accommodation, we analyzed the microfluctuations of accommodation in terms of 'high' (HF: 0.5 - 6 Hz) and 'low' (LF: 0 - 0.5 Hz) frequency components and used HF/LF ratios as measures of the functioning of the accommodative mechanism. The gratings were presented on a video monitor at 0.3 m. The compound gratings consisted of a fundamental and its third harmonic, with phase relations of 0 deg ('triangular'), 90 deg and 180 deg ('rectangular'). - For simple sinusoidal gratings, we investigated the influence of spatial frequency and luminance contrast. At spatial frequencies of about 7 cpd, especially at high contrast, a minimum of accommodation error and of microfluctuation amplitude were found. However, the maximum of HF/LF activity ratio of microfluctuations (which indicates the control activity of accommodation) was found around 3 cpd. This apparent contradiction might be explained by the larger effort required by the subject to focus on high spatial frequency gratings. - For compound gratings, the accommodative accuracy was generally almost the same for all 3 phase relations, except with patterns whose fundamentals were as low as 1 cpd. With these coarse gratings, the accommodative accuracy was better for 180 or 90 deg than for 0 deg. On the other hand, the HF/LF ratio was lower for 180 and 90 deg than for 0 deg, indicating a larger effort of accommodation for 180 and 90 deg. We suppose that the presence of local contrast variations in the 180 and 90 deg patterns increases the demand for precise focusing whereas the smoother spatial luminance profile of the 0 deg pattern does not.
Affiliation of Co-Authors
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