Dry eye disease (DED) has rapidly emerged as a common ophthalmic disorder, with the global prevalence ranging from 5-50%.[1] However, the generic diagnosis of DED without plugging in the specifics has the risk of being a wastebasket diagnosis like other loosely used non-specific quasi-medical terms such as headache. Failure to look for the possible etiology and attribute a cause can often result in misdiagnosis or missed diagnosis and inappropriate treatment. The triad of high prevalence, impact on vision-related quality of life, and the long-term economic costs associated with the treatment make it imperative to accurately diagnose and appropriately manage DED.
Are We Defining It Right?
DED formally became a definable entity only about three decades ago. The 1995 consensus definition by the National Eye Institute/Industry working group on Clinical Trials in Dry Eye was as follows: ‘‘Dry eye is a disorder of the tear film due to tear deficiency or excessive tear evaporation which causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort.”[2] The Definitions and Classification subcommittee of the International Dry Eye Workshop (DEWS) in 2007 brought in tear film osmolality and inflammation into the definition - ”Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.”[3] The 2017 DEWS II definition acknowledges the role of neurosensory abnormality - ”Dry eye is a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.”[4] There is a lingering argument that the definition does not address the etiology entirely and is still incomplete.
Are We Diagnosing It Right?
DED is not to be diagnosed based on symptoms or signs alone. It is to be systematically diagnosed using a stratified diagnostic ladder comprising of symptoms, risk factors, dry eye questionnaires, score on the Ocular Surface Disease Index, determination of homeostasis markers, tests for subtype classification, and determination of severity [Fig. 1].[5] Each step is important in categorizing DED and initiating appropriate management.
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Figure 1: DED diagnostic tree.
[ 5 ] Reprinted from: Wolffsohn JS, Arita R, Chalmers R, Djalilian A, Dogru M, Dumbleton K,
et al.
TFOS DEWS II Diagnostic Methodology report. Ocul Surf. 2017 Jul; 15(3):539-574Are We Treating It Right?
With the current understanding of tear film-based therapy, the management should ideally be aimed to first determine the target - lipid layer/meibomian glands, aqueous, secretory mucin, membrane-associated mucin, goblet cells, and/or ocular surface inflammation[6,7] The mere use of artificial tears will not do justice to the management of DED.
“Meibomian glands are essentially the glands proper to the cornea, which in the interests of vision have been moved out of the way.’’ - Wolff
The role of identification and management of meibomian gland dysfunction in DED cannot be overemphasized. As Korb and Blackie emphasize, the ‘‘rule out MGD first’’ approach has the potential to revolutionize the timing of diagnosis and the choice of frontline therapy in most patients with dry eye.[8]Fig. 2 provides the tear film-based management approach as recommended by the Japanese and Asian Dry Eye Societies.[6,7]
Figure 2: Tear Film Oriented Therapy (TFOT) shows the targets for therapy and possible therapy for each target.
[ 6 , 7 ] Reprinted from Tsubota K, Yokoi N, Shimazaki J, Watanabe H, Dogru M, Yamada M, et al.
; Asia Dry Eye Society. New Perspectives on Dry Eye Definition and Diagnosis: A Consensus Report by the Asia Dry Eye Society. Ocul Surf. 2017 Jan; 15(1):65-76 and http://www.dryeye.ne.jp/tfot/index.htmlWhy the DED Special Issue?
The purpose of this special issue on DED is to bring together comprehensive, contemporary, and curated knowledge with the help of review articles, provide diagnostic and management recommendations with Preferred Practice recommendations, highlight cutting-edge research, and challenge the thought process with articles addressing the cellular and molecular targets. We hope that the contents of this painstakingly put together special issue will help clear the vital basic concepts and enable appropriate diagnosis and treatment of DED.
References
1. Stapleton F, Alves M, Bunya VY, Jalbert I, Lekhanont K, Malet F, et al. TFOS DEWS II epidemiology report. Ocul Surf 2017;15:334–65.
2. Lemp MA. Report of the national eye institute/industry workshop on clinical trials in dry eyes. CLAO J 1995;21:221–32.
3. . The definition and classification of dry eye disease:Report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007). Ocul Surf 2007;5:75–92.
4. Craig JP, Nichols KK, Akpek EK, Caffery B, Dua HS, Joo CK, et al. TFOS DEWS II definition and classification report. Ocul Surf 2017;15:276–83.
5. Wolffsohn JS, Arita R, Chalmers R, Djalilian A, Dogru M, Dumbleton K, et al. TFOS DEWS II diagnostic methodology report. Ocul Surf 2017;15:539–74.
6. Tsubota K, Yokoi N, Shimazaki J, Watanabe H, Dogru M, Yamada M, et al. New perspectives on dry eye definition and diagnosis:A consensus report by the Asia Dry Eye Society. Ocul Surf 2017;15:65–76.
7. Yokoi N, Georgiev GA. Tear film-oriented diagnosis and tear film-oriented therapy for dry eye based on tear film dynamics. Invest Ophthalmol Vis Sci 2018;59:DES13–22.
8. Korb DR, Blackie CA. “Dry Eye”Is the wrong diagnosis for millions. Optom Vis Sci 2015;92:e350–4.
