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MacDx: Consistency of endpoints
White-light and red-light bleaching for 30seconds. Subject: male, 81 years old, 20/20 OD & OS, IOL OU, NL eye exam.
Dark adaptation: White-light: 20.4 seconds, SD 2.8 seconds, range 17 to 27 seconds
Red-light: 22.8 seconds, SD 3.3 seconds, range 17 to 27 seconds
Testing time: 1 minute
MacDx Foveal Dark Adaptation
MacDx a new adaptometer has a unique dark adaptation endpoint within the program that does not requires the patient to relocate to a second instrument following bleaching for dark adaptation endpoint determination. MacDx is a digital program designed for a graphic display device (GDD). The protocol calls for foveal bleaching by viewing a round light on the GDD screen (iPad, iPhone, Android, etc.) for a specified time, followed by viewing a Bull's Eye target where the white center is separated from a white peripheral ring by dark ring. The endpoint is relative, the moment the Bull's Eye center appears the same color and brightness as the peripheral ring. The screening method is 30 second bleaching duration.
The following experiment measures the relationship between red stimulus duration and dark adaptation recovery of an 81-year-old healthy subject with 20/20 acuity in each eye. In Figures 1 and 2 below are dark adaptation curves for subject AJH, right and left eyes. Five dark adaptation endpoints were taken at each bleaching interval: 5, 30, 90, 150 and 300 seconds. As the bleaching duration increases the foveal dark adaptation endpoints rise and the time to reach a final steady threshold value increase.
MacDx Dark Adaptation Curve
OD: Dark adaptation following bleaching of 15, 30, 90, 150 and 300 seconds
OS: Dark adaptation following bleaching of 15, 30, 90, 150 and 300 seconds
Linear R2 close to 1.0 when DA of OD and OS are normal.
Figure 4. Mote, Riopelle (ref 5), Comparison of seconds of light adaptation at difference bleaching intensities and minutes for dark adaptation threshold stimulus steady state.