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A. O Brien, C. Dainty; Simple Device to Measure the Optical Density of the Macular Pigment in vivo. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4956. doi: https://doi.org/.
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To design and construct a simple imaging device to measure in vivo the macular pigment optical density.
The device is designed to be optically simple, portable and easily controlled. By utilisation of a micro controller, specially designed software and custom built electronics, the complete behaviour of the device can be controlled from a single interface. Two objective methods, reflectance and auto-fluorescence, and one subjective method, heterochromatic flicker photometry are employed. Inherent frailities with each technique are confronted by novel software and system design. The techniques are based on the behaviour of a two colour LED system, the operation of which, must be coordinated appropriately to achieve the desired consistency and accuracy in each measurement. The strategy employed to achieve dynamic and independent control over the LEDs is pulse width modulation, while triggering of the system is controlled via the microcontroller, dictated by Labview. Alignment is achieved by use of a fixation target and mounting of the device on a fully adjustable stand. The subject is stablised by use of a head rest.
The results demonstrate the control of the system from a single user interface. The control refers to the development of an appropriate strategy to coordinate LED, filter wheel and camera activity. Dynamic and independent control over the LED operation, data acquisition and image analysis, is also available from a single intuitive terminal. We also show the results of the testing of the system both, for artificial eyes and the initial testing of the device on subjects. These results illustrate the system’s ability to measure the peak density as well as the distribution of the pigment across the macula.
We have developed a simple, portable, inexpensive device to measure the macular pigment optical density in vivo. Its versatility should allow both for a clinical screening application, as well as establishing the physiological role of the MP in a laboratory based environment. This paper concentrates on the assembly and design of this device, and attempts to present the ideas and reasons for its construction.
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