[1] VA Med Ctr, Sect Ophthalmol, Providence, RI 02908 USA
[2] Brown Univ, Div Ophthalmol, Providence, RI 02912 USA
[3] Brown Univ, Program Liberal Med Educ, Providence, RI 02912 USA
[4] VA Med Ctr, Sect Ophthalmol, Iowa City, IA USA
[5] Univ Iowa, Sch Med, Dept Ophthalmol, Iowa City, IA 52242 USA
[6] VA Med Ctr, Sect Ophthalmol, Sacramento, CA USA
[7] Univ Calif Davis, Sch Med, Dept Ophthalmol & Vis Sci, Davis, CA 95616 USA