Research

The theme of research in the Campbell lab is optical properties of the eye. We investigate both the fundamental refractive properties of the eye's components and we seek to use our understanding to improve diagnosis snd therapy for a variety of ocular conditions. We do exciting work with important implications and we use leading edge technologies such as adaptive optics. The work is highly multidisciplinary, involving theoretical modeling, experimental measurement and requiring personnel with diverse expertise. The work fits within the disciplines of biophysics, biophotonics and Vision Science and Prof. Campbell is a member of the Ontario Centre for Photonics, the Ontario Photonics Consortium, the Canadian Centres for Photonics Innovation and the US Center for Adaptive Optics. Backgrounds of previous lab members have included Astronomy, Biology, Chemistry, Engineering, Mathematics, Physics, Optometry, Ophthalmology and Psychology. Former lab members now have careers in academe and in industrial R&D in the biomedical and photonics fields. Some current research projects are explained in more detail below:

Optical properties of the eye and their changes over the lifespan in normal eyes

We have measured the optical quality in normal developing eyes and have compared its changes to models of growth. We have shown that the image quality improves faster than model predictions, suggesting that in the growing eye, there is feedback from an increasingly sensitive retinal mechanism. Our theoretical and experimental studies in this area are continuing.

The crystalline lens has a gradient of refractive index which changes with growth throughout life while maintaining a sharp image on the retina (in normal eyes). Our work has shown that the loss of near vision with age is a result of age related changes in the crystalline lens of the eye which limits the change in shape of the lens which is possible in older eyes. Work is continuing on gradient refractive index optical models of the eye and on possible cures for presbyopia. (see below).

The amount of light scattered in the eye increases with increasing age. We have shown that the design of instruments for imaging the rear of the eye should account for this effect.

Changes in the eye's optical properties as a result of visual experience and in refractive error development

We have shown that the fine structure of the gradient of refractive index in the crystalline lens can be influenced by visual experience. Work is continuing to elucidate the feedback between optical image quality on the retina, and structural changes in the eye. This work was recognized by the Rank Prize in Optoelectronics.

If a lens is placed on an animal eye, the rate of eye growth will change to maintain a focused image on the retina. We have shown for the first time that the optical structure of the eye also changes in a way that worsens the quality of the image on the retina. Optical modeling and experiments are continuing.

Imaging of the rear of the eye for diagnosis and treatment of eye disease

We use our knowledge of the optical quality of the eye to improve images of the rear of the eye. We have developed and patented novel polarimetry techniques which improve the quality of confocal scanning laser images of structures at the rear of the eye which are important to the diagnosis and tracking of glaucoma, age related macular degeneration and diabetic retinopathy, the three leading causes of blindness in North America.

We are developing ultra-high resolution imaging in animal models of ocular disease and refractive error development. This will allow improved tracking of therapeutic interventions.

In a joint project with SickKids hospital, we will be developing a novel high resolution imaging device which will be used to study the earliest changes in the eye in Type I diabetes.

Development of novel adaptive optics

We have assisted in design modifications of a ferrofluid adaptive optics mirror for use in high resolution imaging of the eye. A control loop between a Shack-Hartmann device and the mirror will give real-time correction of the optical imperfections (aberrations) of the eye. This element will be less expensive and have a larger stroke than other available AO corrections for ocular imaging.

Two photon therapies in the eye

Two photon processes localize the effects of light based therapies to much smaller volumes than those therapies which work via single photon processes. We are currently investigating the localized delivery of light into the eye for two photon treatment of presbyopia (the loss of near vision) and age related macular degeneration.