Preface

Dry eye syndrome, also known as keratoconjunctivitis sicca (KCS), is a disorder of the tear film caused by either tear deficiency or excessive tear evaporation.

In the latest decades, we gained a better and better understanding of dry eye syndrome. Early theories assumed that the syndrome was a mere consequence of aqueous tear insufficiency; today, it is classified as a multifactorial disorder caused by inflammation of the ocular surface and lacrimal glands, neurotrophic deficiency, and meibomian gland dysfunction.

The investigation on the composition and regulatory mechanisms of the preocular tear film was a milestone in scientific research about dry eye syndrome: the tear film, in fact, plays a key role in maintaining the corneal and conjunctival integrity, in protecting the eyes against infections, and, ultimately, in preserving visual acuity. Potential modification in the composition or structure of a tear film can have devastating effects, such as desiccation of the ocular surface and ulceration and perforation of the cornea; it is therefore not surprising that patients with dry eye syndrome are prone to potentially blinding infections, such as bacterial keratitis. Previous research works report an increased risk of complications in even common procedures (e.g., laser refractive surgery) in patients with dry eye syndrome.

Advances in dry eye syndrome research gave us a lot of hope in treating such a disease: today, in fact, we can get benefit from recent scientific discoveries to design more accurate diagnostic procedures as well as more advanced devices and effective medical treatments.

This book aims at illustrating the most recent research advances in the diagnosis as well as in the therapeutic strategies of dry eye. The book consists of seven chapters that cover a large spectrum of topics that can be of interest to professional ophthalmologists as well as students. Book chapters are from research groups located worldwide, thus highlighting the huge impact of dry eye syndrome on the field of ophthalmology and, perhaps, on many other medical disciplines to date. Each chapter has been carefully revised not only for scientific correctness but also for clarity: in this way, the proposed material is, in our opinion, accessible to a large, nonspecialist, audience, and thus, it can be regarded as a good entry point to the fascinating topic of dry eye syndrome.

The book is divided into two main sections

In the first section, the chapters describe the most recent diagnostic technique we can rely on today.

Chapter 1 entitled *Examination for Dry Eyes* extensively reviews dry eye diagnostic procedures. Ideally, all of the available tests could be performed at a single visit,

but it is highly recommended the ophthalmologists follow a specific order in carrying out tests. Subjective symptoms often do not correlate with objective signs, and thus, laboratory tests, such as impression cytology, tear osmolarity, and ferning tests, greatly help in formulating a diagnosis. The most effective laboratory test, even if it might be too invasive for many patients, is the conjunctival biopsy, which analyzes specimens of epithelial layers and conjunctival stroma and is effective in identifying and counting the number of inflammatory cells.

Chapter 2 entitled *The Physiology of Tear Film* carefully points out the composition and functioning of the three-layer structure of the tear film, namely lipid, aqueous, and mucous layers. The chapter well clarifies that any disorder occurring in each of the three layers can affect the appearance of dry eye syndrome.

Chapter 3 is entitled *Lymphocytes in Dry Eye Disease* and highlights the role of the immune system in eye diseases, specifically in dry eye syndrome. In fact, modifications in immune cells, due to mechanical or chemical stimuli as well as infections, create, and magnify, immune responses that, in the long run, determine an injury of the ocular tissues.

Chapter 4 entitled *Diagnosis of Dry Eye* focuses on questionnaires, one of the most frequent techniques to diagnose dry eye syndrome. Questionnaires are relevant to measure parameters, such as the amount of tear secretion, tear clearance, tear volume, tear film stability, and tear evaporation, and quantify the degree of inflammation of the ocular surface and impact of inflammation on the daily lives of patients. Popular questionnaires are the Ocular Surface Disease Index (OSDI), Dry Eye Questionnaire (DEQ-5), Impact of Dry Eye on Everyday Living (IDEEL), and National Eye Institute's Visual Function Questionnaire (NEI VFQ-25).

The second section of the book is centered on the most recent, and promising, strategies to treat dry eye syndrome as well as on the potential, but often not fully elucidated, relationships among dry eye syndrome and other ocular diseases, such as glaucoma.

Chapter 5 entitled *Glaucoma and Dry Eye* discusses the side effects we might encounter in patients with glaucoma. Topical glaucoma treatments, in fact, cause chronic inflammations that severely affect the quantity and quality of tears: as a consequence, glaucoma medications may lead to the appearance of the syndrome or to its worsening. The chapter also surveys some recent treatments for patients with glaucoma proven to be effective in preserving the quality of the ocular surface.

Chapter 6 entitled *How Ocular Surface Disorder Affected Corneal Graft Survival* is about the role of dry eye syndrome in corneal graft failure. It is well-known, in fact, that inflammations, vascularization, and previous graft failure are high-risk factors in the rejection of cornea after a transplant. Corneas from patients with dry eye syndrome can activate an inflammatory process by increasing the number of T cells in the host, and this may predispose high rejection rates. Recently, HLA matching techniques have been applied in predicting graft survival rates in corneal transplants.

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Finally, Chapter 7 entitled *Intense Pulse Laser Therapy and Dry Eye Disease* describes a recently approved therapy called IPL. IPL is a second-stage therapy that follows treatments based on ocular lubricants and relies on brief flashes of noncoherent

> **Felicia M. Ferreri** BIOMORF Department, University of Messina,

> > Messina, Italy

light with a wavelength between 400 and 1200 nm.

Finally, Chapter 7 entitled *Intense Pulse Laser Therapy and Dry Eye Disease* describes a recently approved therapy called IPL. IPL is a second-stage therapy that follows treatments based on ocular lubricants and relies on brief flashes of noncoherent light with a wavelength between 400 and 1200 nm.

> **Felicia M. Ferreri** BIOMORF Department, University of Messina, Messina, Italy
