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BACKGROUND AND OBJECTIVE To determine the prophylactic and therapeutic value of a single subthreshold 810-nanometer laser treatment in patients with high risk drusen as a manifestation of dry age-related macular degeneration in both eyes. PATIENTS AND METHODS The Prophylactic Treatment of Age-related Macular Degeneration study enrolled 1,278 eyes of 639 participants who were 50 years or older with at least 5 drusen 63 µm or more in diameter in each eye. Treatment consisted of the placement of an annular grid of 48 extrafoveal, subthreshold 810-nm diode laser applications centered at but sparing the foveola in one eye of each participant, with the fellow eye serving as a control. Development of choroidal neovascularization and change in best-corrected visual acuity were compared between treated and untreated eyes. RESULTS Subthreshold laser treatment did not decrease the incidence of choroidal neovascularization in treated versus untreated eyes. A modest visual acuity benefit in treated eyes was found at 24 months (1.5 letter difference; P = .04) and in the treated eyes of participants with a baseline visual acuity between 20/32 and 20/63 (4.0 letter difference; P = .0034). However, this treatment effect was not sustained at 3 years. CONCLUSION A single subthreshold 810-nanometer laser treatment to eyes of participants with bilateral high risk drusen is not an effective prophylactic strategy against choroidal neovascularization. [Ophthalmic Surg Lasers Imaging 2009;40:530-538.] AUTHORS From the UPMC Eye Center (TRF, PMB), University of Pittsburgh, Pittsburgh, Pennsylvania; the Shiley Eye Center (WRF), University of California–San Diego, La Jolla, California; and the W. K. Kellogg Eye Center (DCM), University of Michigan, Ann Arbor, Michigan. Accepted for publication December 19, 2008. Supported by Iridex Corporation, Mountain View, California, and the sources listed under the individual center descriptions found at the end of the article; the Eye and Ear Foundation of Pittsburgh, Pittsburgh, Pennsylvania; Research to Prevent Blindness, Inc., New York, New York; and unrestricted funds from several participating centers. Presented in part at the annual meeting of the American Academy of Ophthalmology, October 15-18, 2005, Chicago, Illinois, and the annual meeting of the Association for Research in Vision and Ophthalmology, April 30-May 4, 2006, Ft. Lauderdale, Florida. The authors thank photographic readers Cheryl Hiner, Columbia, MD, Rosemary J. Brothers, Madison, WI, and Linda Huang, MD, and Maria Palaiou, MS, Pittsburgh, PA; the Data and Safety Monitoring Committee voting members Donald J. D’Amico, MD, Mark W. Johnson, MD, J. Richard Landis, PhD, and nonvoting ex-officio member, Dr. Musch; and Giorgio Dorin for his contribution to the manuscript. The authors have no financial or proprietary interest in the materials presented herein. Address correspondence to Thomas R. Friberg, MS, MD, UPMC Eye Center, 203 Lothrop Street, Suite 824, Pittsburgh, PA 15213. doi: 10.3928/15428877-20091030-01

It has been suggested that mast cells may play a role in the growth and maintenance of new blood vessels. Since capillary proliferation is an important component of diabetic retinopathy, we have examined 38 retinas from patients with all stages of this disease, looking for the presence of mast cells. No mast cells were observed in any of the retinal specimens, regardless of the degree or severity of diabetic retinopathy and in spite of the fact that mast cells were seen in the sclera of all 38 specimens. These results suggest that the presence of mast cells is not an obligatory requirement for all types of neovascularization.

While only a small proportion of adult-onset diabetic patients develop vision threatening retinopathy, this group makes up a major portion of those diabetics seeking ophthalmologic care. Fifty-three percent of patients having fundus photographs at the W.P. Beetham Eye Unit of the Joslin Clinic developed diabetes at the age of 20 or over, and almost 30% at the age of 40 or over. Twenty-two percent of all patients seen with proliferative retinopathy were in this latter group. Ten of 54 patients with proliferative retinopathy in the greater than or equal to 40 onset group were not taking insulin. The older onset patients who developed proliferative retinopathy did so after shorter durations of diabetes and with more visual disability than younger onset patients. Macular edema was more common in adult-onset patients, and its presence in a patient less than 50 years old was usually associated with proliferative or preproliferative retinopathy.