Preface

Blindness defines either the best-corrected distance visual acuity or presenting distance visual acuity in the better eye. Different visual acuity levels are commonly used to better define blindness ranging between < 20/400 and < 20/200 in the better eye. In contrast, visual impairment defines a visual acuity of 20/60 or less in the better eye.

The prevalence of blindness varies considerably among developed countries. Socio-economic factors are linked to available health and eye care services and thus influence prevalence. For example, a 0.25 prevalence of blindness among the general population living in a well-developed country may translate to a 1.25 prevalence in a country with poor socio-economic status and health care. Differences in prevalence are also due to blindness being secondary to several diseases and conditions, such as cataracts, refractive errors, and corneal scarring (trachoma, corneal infections, and vitamin A deficiency). Visual impairment and blindness is an important public health problem that requires affordable, high-quality clinical and diagnostic capacity, good therapeutic approaches, and rehabilitation.

In this book we provide an overview of the effects of blindness and visual impairment in the context of the most common causes of blindness in older adults and children. These causes may include retinal disorders, cataracts, glaucoma, and macular and corneal degeneration.

**Giuseppe Lo Giudice, MD**

San Paolo Ophthalmic Center, San Antonio Hospital, University of Padua, AOPD, Italy

**Angel Catala** National University of La Plata, Argentina

**1**

Section 1

Cornea and Refractive

Concepts

Section 1
