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Sascha Klee, Patrick Bessler, Jens Haueisen; Verification of Cone Isolation Techniques using an Adaptation Box. Invest. Ophthalmol. Vis. Sci. 2011;52(14):699.
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Selective excitation of the human cones has got a wide variety of applications. To get evidences for their successful implementation the examination of protan- and deuteranopes may be accomplished. The strongest indication can be achieved by investigating tritanopes but they are too rare. Our aim was the design and application of an adaptation box which is suitable to test cone isolation techniques by conducting bleaching experiments in healthy volunteers.
Considering homogeneous lighting conditions, light efficiency, and field of view size, we designed a box with the dimension of 130 cm x 80 cm x 100 cm using synthetic Lambertian surface material. We integrated a four channel RGBW fluorescent tube system which was controlled by a digital addressable lighting interface. The dominant wavelength and maximum illuminance were adjusted to 436 nm - 1104 lux (B); 486 nm, 542 nm - 5483 lux (G); and 601 nm, 631 nm - 2857 lux (R). We verified two selective stimulation sequences (S-cone and LM-cone) based on the silent substitution technique. The box was set to bleach the S-cones selectively and to spare the LM-cones. This simulates a tritanope. After 10 min of S-cone bleaching a selective stimulation with simultaneous EEG recording was conducted. A period of 60°min was implemented between repetition. We used a moving average window for the time analysis of the VEP.
There were no significant VEPs in the first average window (0-19 s after end of bleaching) for the S-cone responses. Very small responses arose 37 s after the bleaching. Clear S-cone VEPs were visible after 54 s. The LM-cone responses were not affected by the bleaching and were already visible in the first averaging window. The absence of S-cone responses up to nearly 50 s after the bleaching in contrast to the unaffected LM-cone responses is an evidence for the successful selective cone isolation.
We designed and used an adaptation box to verify a cone isolation technique. Due to the S-cone bleaching procedure it was possible to simulate a tritanope and to get clear evidences for a successful selective stimulation.
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