Purpose: Mice are one of the major biological organisms for studying the genetic bases of human retinal disease. Unfortunately, the small size and consequently high refractive power of the mouse eye poses major problems for high resolution imaging. Previous approaches to imaging the mouse retina have adapted pre-existing imaging systems for the mouse. The purpose of the current study was to perform initial studies to guide the design and construction of a modern confocal adaptive optics SLO system for imaging the mouse retina.
Methods: A 30Hz confocal scanning laser ophthalmoscope was constructed. The major features of the system were 1) Use of 633 nm laser, and filters for both direct light imaging and near IR fluorescent label imaging. 2) An integrated Hartmann Shack wavefront sensor for measuring the aberrations of the mouse eye. 3) Provisions for incorporation of aberration control, 4) An avalanche photodiode for detection. 5) galvanometers based deflection system, 6) A very large range of defocus compensation. 7) A corneal contact lens was used to maintain anterior eye clarity. The system visualizes the eye through a 1 mm pupil.
Results: Mice retina were successfully imaged, with good contrast of the major retinal vessels and visualization of nerve fibers. A major problem was that the mice used had a wide range of emmetropia, ranging from slightly myopic when fitted with the corneal contact lens to 20 diopters hyperopic. The HS sensor in its current configuration is very useful for determining best focus, and higher order aberrations on the mouse eyes measured to date are low.
Conclusions: The current system has some problems with reflections, but has proven useful for imaging and for testing out the initial stages of the imaging system design.