Purpose
Previous studies showed clearing of the brain using a water-based optical clearing method denominated See Deep Brain (SeeDB). However, although the eye belongs to the central nervous system, this histological technique was not used until now. Applying this new clearing technique could open new possibilities for the histological visualization of the normal anatomy or pathological changes of the eye maintaining original architecture. We applied this optical clearing method for visualization of intraocular structures.
Methods
Four eyes of cornea-donors (2 male, 2 female: 73 to 84 years) obtained from the Cornea Bank of the Department of Ophthalmology, were used. After enucleation and extraction of the corneoscleral button, bulbi were fixed with 4% paraformaldehyde in PBS and treated with increasing concentrations of aqueous fructose solution with 0.5% α-thioglycerol. After the optical clearing procedure, transscleral microphotographs of the choroid were taken using confocal microscopy.
Results
Complete transparency of the sclera was obtained in the SeeDB treated enucleated human eyes. Transscleral visualization of the choroid is possible. The transparency of the choroid is only partial, because the SeeDB method does not act on melanocytes of the uvea. Microscopical observation and photographic documentation of vessels and other choroidal tissues is also allowed without additional processing of the specimens.
Conclusions
The SeeDB method allows visualization of intraocular structures in fixed enucleated human eyes through a completely translucent sclera. This innovative imaging technique could facilitate comprehensive qualitative and quantitative studies of the whole human eye, preserving its 3D relations. Of special interest, supra- and intrachoroidal ganglionic plexus could be visualized transsclerally. Also choroidal vessels and melanocytes are now accessible for direct visualization without opening the fixed, enucleated eyes. Finally, clinical-pathological correlations of some intraocular diseases - e.g. choroidal or retinal tumors will be possible in intact eyes.