Readers who wish to explore specific topics in greater detail may consult the references cited within each chapter and listed in the Additional Materials and Resources section at the back of the book. These references are intended to be selective rather than exhaustive, chosen by the BCSC faculty as being important, current, and readily available to residents and practitioners.

^• Introduction to the BCSC

This edition of Section 8, External Disease and Cornea, includes videos related to topics cov­ ered in the book, and interactive content, an “activity,” developed by members of the BCSC faculty. The videos and activity are available to readers of the print and electronic versions of Section 8 (www.aao.org/bcscvideo_section08 and www.aao.org/bcscactivity_section08). Mobile-device users can scan the QR code below (a QR-code reader may need to be installed on the device) to access the videos and activity.

Videos

Activities

Each volume of the BCSC is designed as an independent study activity for ophthalmology residents and practitioners. The learning objectives for this volume are given on page 1. The text, illustrations, and references provide the information necessary to achieve the objectives; the study questions allow readers to test their understanding of the material and their mastery of the objectives. Physicians who wish to claim CME credit for this educational activity may do so by following the instructions given at the end of the book.*

The Basic and Clinical Science Course has expanded greatly over the years, with the ad­ dition of much new text, numerous illustrations, and video content. Recent editions have sought to place a greater emphasis on clinical applicability while maintaining a solid foun­ dation in basic science. As with any educational program, it reflects the experience of its authors. As its faculties change and medicine progresses, new viewpoints emerge on controversial subjects and techniques. Not all alternate approaches can be included in this series; as with any educational endeavor, the learner should seek additional sources, including Academy Preferred Practice Pattern Guidelines.

The BCSC faculty and staff continually strive to improve the educational usefulness of the course; you, the reader, can contribute to this ongoing process. If you have any sugges­ tions or questions about the series, please do not hesitate to contact the faculty or the editors.

The authors, editors, and reviewers hope that your study of the BCSC will be of last­ ing value and that each Section will serve as a practical resource for quality patient care.

* This activity meets the Self-Assessment CME requirements defined by the American Board of Oph­ thalmology (ABO). Please be advised that the ABO is not an accrediting body for purposes of any CME program. ABO does not sponsor this or any outside activity, and ABO does not endorse any particular CME activity. Complete information regarding the ABO Self-Assessment CME Maintenance of Certifi­ cation requirements is available at https://abop.org/maintain-certification/cme-self-assessment/.

For the 2021–2022 major revision of Section 8, External Disease and Cornea, the committee listened carefully to readers and made a number of important changes and added new features, the most significant of which are discussed below.

A new feature, the online case studies explore corneal ectasia and ocular surface lesions, supporting and enhancing the material presented in the text. These case studies are easily accessed via QR codes in the chapters.

CASE STUDY 9-1  Corneal ectasia.

Courtesy of Robert S. Feder, MD.

This new feature identifies information throughout the chapters that should not be missed. Their subtle presentation allows readers to add their own highlights to the pages as well.

a minimal risk of malignant transformation but should be followed more closely. PAM with moderate to severe atypia carries a 30% risk of progression to melanoma. Every effort

The “Clinical Pearl” boxes throughout the book present information that has direct impact on the diagnosis and management of corneal disease and can be quickly incorporated into clinical practice.