Applications of liposomes in ophthalmology

This review outlines the applications of liposomal formulations in ophthalmology. In ophthalmology, liposomes have been used to treat disorders of both the anterior and posterior segments. These include dry eyes, keratitis, corneal transplant rejection, uveitis, endophthalmitis, and proliferative vitreoretinopathy. Liposomes also have shown promise as vectors for genetic transfection and monoclonal antibody-directed vehicles. Furthermore, heat-activated liposomes have spurred research in focal laser and heat-induced release of liposomal drugs and dyes for selective drug delivery. These techniques have been useful in selective tumor and neovascular vessel occlusion, angiography, and retinal and choroidal blood-flow studies. Although verteporfin is the only liposomal drug currently approved for use in the eye, the benefits of liposomes will likely be applied widely in all treatment, diagnostic, and research aspects of ophthalmology in the future.

Ocular fundus images with confocal scanning laser ophthalmoscopy in the dog, monkey and minipig

Confocal scanning laser ophthalmoscopy (CSLO) is a new technique that enables ocular fundus image recording and retinal dynamic angiography to be performed. The ocular fundus image is acquired sequentially, point by point, and is reconstructed on a video monitor at the rate of 25 images per second. The feasibility of performing both ocular fundus image recordings and retinal angiography image recordings were tested on two dogs, two monkeys and two minipigs using a 40 degrees field I + Tech CSLO. Fundus area of each dog, monkey and minipig were examined without any additional optical devices. The ocular fundus and angiography images were recorded, stabilized and analyzed under the same conditions. For each species, all images were easily recorded without any additional optical device in a lighted room and the morphology of the retinal images generated was similar to those obtained with a camera or angiography of higher resolution. Capillary phase or venous times are presented. Image recording at 25 frames/second enabled more retinal dynamics to be demonstrated than with use of regular angiography. This technique is noninvasive and easy to perform if the eye is fixed and eyelids maintained open. It also allows exploration of retinal microvascularization and could be utilized for clinical, pharmacologic and toxicologic investigations as well.

The scanning laser ophthalmoscope

The imaging of the fundus of the eye poses two major technical challenges. First, it is necessary for both the illuminating and reflected beams to pass through the same aperture, the iris. In some commonly used instruments this leads to the use of levels of illumination close to the maximum tolerable by a patient. Second, in order to visualize the different structures present in the various layers of the fundus it is necessary to perform tomographic imaging. The scanning laser ophthalmoscope provides an answer to these particular problems. By scanning the fundus with a narrow laser beam most of the area of the iris is then available for the reflected light and so the intensity of the illuminating beam can be kept low, making it more acceptable for patients. The use of confocal imaging allows 3D images to be produced. In this short review the performance of the instrument will be discussed and its application to a number of clinical problems in ophthalmology considered. Finally there will be a brief description of other instrumentation currently under development.