is not easily observed in the early stage. New optical methods employing optical coherence tomography (OCT), a type of microscopic laser radar imaging that can probe beneath the surface of the retina, provide a method for precise subsurface imaging. OCT provides a high-resolution, three-dimensional image of the interior of the eye, allowing subsurface structures to be resolved down to a depth of about 1 millimeter below the surface of the retina. This capability allows early diagnosis and early intervention, which can stop or slow down the disease progression, providing the potential for many additional years of visual acuity to affected individuals.
The number of cases of AMD and DR has increased greatly due to the aging of the population and the obesity epidemic.22 Early detection and intervention with new anti-angiogenesis drugs have proven to be remarkably effective in treating AMD. Moreover, the efficacy of new drugs currently under development can be quantitatively assessed and compared using the three-dimensional OCT images, which accurately define the volume of the lesions in the retina caused by AMD. Changes in the lesion volumes provide a direct measure of the drug efficacy and can help determine effective and safe dosage levels.
OCT also provides the capability for the accurate mapping of the lens and surrounding tissue capsule, which can be measured with great precision in all three dimensions. This information, when combined with laser surgery using ultrafast lasers, has the potential to revolutionize the protocol for treating cataracts. Using OCT guidance, femtosecond lasers can be precisely focused on the capsule and automatically cut close to perfectly round incisions in the capsule. These precise incisions greatly assist in locating and centering the replacement lens. The same ultrafast pulsed laser can also be used to segment the original occluded lens, which can then be much more easily extracted from the patient’s eye. This combination of OCT for precise measurement of eye morphology, along with precision femtosecond ultrafast laser machining, is setting a new standard for quality in these ophthalmic procedures, as seen in Figure 6.6.23
For most solid tumor cancers, surgical excision is often the optimal intervention strategy when it is feasible. Most often it is very important to balance the
22 AMD Alliance International. 2011. Increasing Understanding of Wet Age-Related Macular Degeneration (AMD) as a Chronic Disease to ensure that all patients have access to early intervention, regular proactive treatment, and integrated care, and that research is ongoing for improved treatment options. Available at http://www.amdalliance.org/user_files/documents/AMD_ChronicDiseasePolicy_M03_NoCrops_Low_Res.pdf. Accessed August 1, 2012.
23 Friedman, N.J., D.V. Palanker, G. Schuele, D. Andersen, G. Marcellino, B.S. Seibel, J. Batlle, R. Feliz, J.H. Talamo, M.S. Blumenkranz, and W.W. Culbertson. 2011. Femtosecond laser capsulotomy. Journal of Cataract and Refractive Surgery 37(7):1189-1198.