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Postrefractive surgery dry eye Guilherme G. Quinto, Walter Camacho and Ashley Behrens The Wilmer Ophthalmological Institute, The Johns Purpose of review Hopkins University School of Medicine, Baltimore, Maryland, USA To report the recently published literature on ocular surface changes after refractive surgery, as well as the outcomes of treatment modalities on postrefractive surgery dry Correspondence to Ashley Behrens, MD, The Wilmer Eye Institute, 600 North Wolfe St., 255 Woods eye. Building, Baltimore, MD 21287-0005, USA Recent findings Tel: +1 410 502 0461; e-mail: [email protected] Cyclosporine, the first US Food and Drug Administration approved agent to treat the underlying pathological mechanism of chronic dry eye, has demonstrated promising results in dry eye patients. Further, there may be an additive effect of topical Current Opinion in Ophthalmology 2008, 19:335–341 cyclosporine and punctal occlusion. Femtosecond lasers for corneal flaps in laser in-situ keratomileusis seem to induce fewer signs and symptoms of dry eye and may be attributed to the creation of thinner flaps. Summary Dry eye is one of the most common complications after photorefractive keratectomy and laser in-situ keratomileusis. Keratorefractive surgery is known to cause damage to the corneal sensory nerves. Several studies have demonstrated a decrease in corneal sensation, tear secretion, and tear film stability several months after keratorefractive surgery. For patients with preoperative dry eye, the ocular surface must be treated accordingly prior to surgery. Keywords dry eye syndrome, laser in-situ keratomileusis, management, ocular surface, photorefractive keratectomy Curr Opin Ophthalmol 19:335–341 ß 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins 1040-8738 gathered to elaborate diagnostic and treatment guidelines Introduction for dry eye syndrome using a Delphi consensus technique One of the most common complications of photorefractive [3]. One of the recommendations of the panel was that the keratectomy (PRK) and laser in-situ keratomileusis term ‘dry eye syndrome’ be replaced with ‘dysfunctional (LASIK) is dry eye syndrome [1,2]. Although dry eye tear syndrome’ to reflect current understanding of the after refractive surgery is usually transient, some patients pathophysiology of the disease [3]. complain of severe symptoms, which may negatively influence their satisfaction with the outcome of the pro- cedure [3,4]. Both keratorefractive procedures have been DEWS Definition and Classification Subcommittee [7] reported to perturb the ocular surface homeostasis by provided a contemporary definition of dry eye disease causing a decrease in corneal sensitivity, tear film instabil- supported within a comprehensive classification frame- ity, decreased aqueous tear production, and corneal and work. A new definition of dry eye was developed to conjunctival epitheliopathy [5]. This review summarizes reflect current understanding of the disease, and the the recently published literature on the ocular surface committee recommended a three-part classification of changes after keratorefractive surgery and its treatment dry eye, based on etiology, mechanism, and disease modalities. stage. These guidelines are not intended to override the clinical assessment and adjustment of an expert clinician in individual cases. Dry eye syndrome Dry eye syndrome encompasses diverse etiologies and Dry eye syndrome is defined as a disorder of the tear film varies greatly in severity. In addition, correlations between caused by tear deficiency or excessive tear evaporation, symptoms, clinical signs, and diagnostic test results are which causes damage to the interpalpebral ocular surface variable, making the diagnosis and treatment of this con- and is associated with symptoms of ocular discomfort dition challenging [6]. Due to this need, an International [8–10]. Diagnosis is made after analyzing patients’ com- Task Force consisting of 17 dry eye expert clinicians was plaints, objective signs, and abnormal results of dry eye 1040-8738 ß 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 336 Refractive surgery tests [11]. The symptoms are usually described by escein staining, and severity of conjunctival squamous patients as burning, dryness, or foreign-body sensation, metaplasia in patients with Sjo¨gren’s syndrome kerato- often associated with ocular pain, blurred vision, photo- conjunctivitis [15]. phobia, and visual fatigue. The clinical signs of dry eye include positive vital staining of ocular surface, decreased tear film breakup time and Schirmer tests, reduced Tear secretion and tear film instability corneal sensitivity, and decreased functional visual acuity Keratorefractive surgery seems to cause tear-deficient dry [11]. eye by a neural-based mechanism. Since the usual stan- dard method to evaluate reduced tear volume and tear flow The quality of life can be significantly affected by dry eye is the Schirmer test, studies have consistently included symptoms, as documented by several validated survey these data when reporting dry eye incidence [8]. Several instruments [12]. The psychological impact of this recent studies have demonstrated the decrease on corneal chronic condition is suggested by a utility assessment barrier, tear secretion, and tear film stability. Polunin et al. of patients’ willingness to trade years at the end of life for [16] showed that the corneal barrier function decreased an opportunity to be free of dry eye, which found that the after PRK and LASIK treatments, and the recovery was utility of moderate dry eye was similar to that of moderate more delayed after LASIK than after PRK. Yu et al. [17] angina [13]. investigated the effect of LASIK on tear function in 96 eyes of 58 patients for the correction of myopia. LASIK significantly altered the tear break-up time, Schirmer test Etiology values, and basal tear secretion. They also concluded that The pathophysiologic definition of dry eye was changed patients with preexisting tear flow abnormality measured to a dysfunction of the integrated ocular surface-secretory with Schirmer test values less than 10 mm was a significant glandular functional unit [14]. Communication between risk factor for experiencing dry eye symptoms at 1 month the ocular surface and lacrimal glands occurs through a after surgery. sensory autonomic neural reflex loop. The sensory nerves innervating the ocular surface connect with efferent Lee et al. [18] compared tear secretion and tear film autonomic nerves in the brain stem that stimulate instability following PRK (36 eyes of 21 patients, ranging secretion of tear fluid and proteins by the lacrimal glands. from 2.50 to 6.00 D) and LASIK (39 eyes of 25 patients, Ocular surface sensitivity has been found to decrease as rangingÀ from À3.25 to 9.75 D). At 3 months following aqueous tear production and clearance of tears from the surgery there wasÀ significantlyÀ decreased tear secretion and ocular surface decrease. This decrease in surface sen- tear film stability in LASIK patients compared with PRK sation exacerbates dry eye because sensory stimulated patients. Although not statistically significant at 6 months, reflex tearing is decreased, resulting in decreased ability tear secretion and tear film stability were still decreased in of the lacrimal glands to respond to ocular surface insults. LASIK and these values never reached preoperative Thus, a self-perpetuating cycle between the lacrimal levels. Nejima et al. [19] evaluated corneal barrier function, gland and the ocular surface is created [14]. Adequate tear secretion, and tear stability after PRK (28 eyes of aqueous tear production and clearance with normal 15 patients) and LASIK (115 eyes of 59 patients). Both mucous gland function are finely controlled by balancing procedures decreased epithelial barrier function, reduced the innervation of the ocular surface and the tear- tear secretion, and deteriorated tear film stability secreting glands to prevent surface dryness. The dry (P < 0.05). Increases in corneal epithelial permeability eye from keratorefractive surgery results mostly from were, again, more prolonged after LASIK than after damage to the corneal sensory nerves. Inflammation plays PRK. A significant intergroup difference in permeability an important role as well in the pathogenesis of dry eye, was observed 1 month after surgery (P < 0.05). In their and it has been elucidated over the past decade [15]. study, tear break-up time was significantly shorter in the Decreased tear production and tear clearance lead to LASIK group than in the PRK group up to 3 months after chronic inflammation of the ocular surface. This inflam- surgery (P < 0.045). matory response consists of cellular infiltration of the ocular surface by activated T lymphocytes, with Konomi et al. [20] have shown recently that preoperative increased expression of adhesion molecules and inflam- tear volume may affect the recovery of the ocular surface matory cytokines, increased concentrations of inflamma- after LASIK, increasing the risk of chronic dry eye. In this tory cytokines in the tear fluid, and increased activity of study, patients were classified into two main outcome matrix degrading enzymes such as matrix metalloprotei- groups: the nondry eye group and the chronic dry eye nase MMP-9 in the tear fluid. Significant positive corre- group, on the basis of dry eye status 9 months after lation has been observed between the levels of inflam- surgery. All parameters,
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