[1] Univ Sassari, Inst Ophthalmol, I-07100 Sassari, Italy
[2] Univ Sassari, Inst Clin Biochem, I-07100 Sassari, Italy
[3] Univ Parma, Inst Ophthalmol, I-43100 Parma, Italy
[4] Univ Sassari, Inst Hyg & Prevent Med, Epidemiol & Biostat Lab, I-07100 Sassari, Italy