Age-related macular degeneration (AMD) is the most common form of sight loss in adults. The retinal densitometer is being developed to detect AMD at the earliest stages by measuring how the light sensitive pigments in the macula regenerate after exposure to light. The operating procedure of the device involves bleaching of the subject’s retina followed by the mapping of the reflectance of the macula at different wavelengths at different stages over a dark recovery period.






The imaging retinal densitometer is a device particularly suited for the detection of AMD via the bleaching of the retina and subsequent mapping of the reflectance of the macula as it adjusts over a dark recovery period. The apparatus comprises three units: a control unit, a head unit and an analysis unit.

The control unit is comprised of the control module, measurement module and bleaching module. The control module is responsible for the synchronisation of the light generation and the image acquisition undertaken by the measurement module. The measurement module generates illumination of predetermined wavelengths or wavelength bands, over the range of 410-850nm. The reflectance of the patient’s eye is the characteristic measured response to the illumination. The light output at each wavelength has a predetermined bandwidth, such as a bandwidth of 10 nm at FWHM. The bleaching module has a broadband light source that may be activated for a continuous period between 2 and 30 minutes or in pulses of duration between 5ms and 120 seconds.

The head unit is comprised of a headrest for the patient, optics carrying illumination from the measurement module, an eyepiece and an imaging device. The eyepiece is used to form a magnified image of the eye. Optics from the measurement module carry illumination to the eye at the head unit. This is fibre optic cable in most embodiments but may involve a liquid light guide in some cases. The imaging device may be a charge-coupled device (CCD) or a CMOS image censor and is capable of recording a spatial map of light reflected from measurement module by the macula. The headrest supports the patient’s head and allows the position of the imaging area to be adjusted in the x, y and z directions. 

The analysis unit holds the graphical user interface that allows the operator to perform such tasks as select the modes of operation and the plurality of wavelengths over which the eye’s reflectivity will be tested.



  • The retinal densitometer has the ability to test dark adaption at a number of wavelengths that can be determined by the operator.

  • Uniform illumination to a desired area of the retina.

  • Mapping of dark adaption to an image of the eye.



  • Early-stage diagnosis of age-related macular degeneration.

  • Switching between sources, while recording a series of images, allows measurement of changes in reflectance as a function of time and wavelength across the retina. This allows the device to map the change in optical density of the visual pigments over time.



  • Ophthalmology

  • Optometry


Patent Information:
Country Serial No.
United Kingdom GB1206174.3
Patent Cooperation Treaty PCT/GB2013/050887


Medical & Biomedical
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