VETENSKAP # 9–2016 www.optikbranschen.se
Ny epok i svensk optometri
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å är vi inne i september 2016, den första månaden då optiker med godkänd utbildning har behörighet att använda diagnostiska droppar. Hoppas att alla som kan har skickat ansökan till Socialstyrelsen. I detta nummer är det gemensamma ämnet tårvätskan. Den första artikeln är en rapport om tårvätskan och kontaktlinsbärande, här presenteras nya resultat. Det andra är ett examensarbete från LNU som ligger som länk på nätsidan, här har det undersökts torrhetsparametrar innan och efter implantat av en ICL lins. Att problem med tårvätskan ökar på hösten är tydligt, hade idag själv fyra nya patienter som behövde Blephex-behandling samt två som kom på uppföljningsbesök efter en sådan och de har märkt en klar förbättring. Ett ämne som diskuteras på sociala medier bland optiker nu är: Vid vilken ålder ska man börja mäta trycket? Är det vid 40 år, 50 år eller det ögonläkarna i området rekommenderar? Frågan har ställts vad Optikerförbundets SOTAdokument säger. Där finns ingen specifik ålder angiven. Mitt svar är enkelt, börja mät innan det behövs, på det sättet fångas även tidiga variationer upp. Ett patientexempel på detta är kortfattat följande: 35-åring kommer för undersökning uppger irritation, besvär och trötthet i ögonen. Allt är normalt ingen ref-ändring, mäter IOP som är H22/ V21 alltså inom normala gränser, om det inte varit
för ett tre år tidigare IOP värde på 12/12 och 12/12 sju år tidigare. Papillen ser dock bra ut. Mäter en vecka senare då 24/20 en vecka senare 22/20. Så håller det på, ett år senare är IOP ca 26/21 ganska stadig, Kontroll är gjord hos ögonläkare utan åtgärd men med planerade återbesök. Vid 38 års ålder är IOP 32/22 då sätts droppar in. Idag är patienten 51 och behandlar båda ögonen och har inte någon synfältspåverkan, liten storleksskillnad på C/D-kvot. Tack vare de tidigare IOP-värdena fanns vetskapen om att en ökning av IOP skett, som ska hållas under uppsikt. Det fanns inte någon glaucom eller OHT i släkten. Detta är inte vanligt men dessa patienter finns och de vill behålla synen och vi kan upptäcka dem. Hade jag arbetat enligt de riktlinjer som ögonkliniken här ger ut idag skulle inte IOP ha mätts innan 50 års ålder, frågan är då hur det hade varit för denna patient idag. Det är vårt ansvar att upptäcka och vi är inte skyddade för att ögonklinikerna ger ut andra önskemål. Vi är ett eget yrke med egen legitimation det skedde 1964 och sedan dess har vi eget ansvar för det vi gör. Så rådet är gör alla undersökningar, om ett eller tio år vill du veta hur det var idag, det kan du inte kontrollera då. Frågor till artiklarna finns som vanligt på Optikerförbundets hemsida och artiklarna i sin helhet på Optikbranschens hemsida. Trevlig läsning. CATARINA ERICSON
n Artikel 1: Inspired by the science of tears n Artikel 2: Utvärdering av ögontorrhetsparametrar och synskärpa hos patienter som fått Visian ICL implanterat
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Catarina Ericson är OPTIK:s vetenskapsredaktör. Hon är MSc i Klinisk Optometri och Leg Optiker. e-post: catarina@c-optik.se
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Redaktörens kommentar:
Introduktionen ger en bra förståelse för tårfilmens komplexa sammansättning. Sista delen är intressant med hänsyn till kombinationen, tårfilmen med olika linsegenskaper.
Inspired by the science of tears A better understanding of how contact lenses interact with the eye and the tear film is helping to develop new material technologies, as Bart Johnson, Dr Brian Pall and Dr Charles Scales report Tears are vital to maintain a healthy ocular surface and an optically clear entrance to the eye. Without them, we would not have the sharp retinal image that allows us to see the world and each other clearly. Tears are rich and complex, and that richness is necessary for their efficacy. Water alone could not nourish and protect the delicate corneal and conjunctival epithelia, nor give us the clear, stable vision we experience daily. The human tear film is optimised to address a unique additional challenge: create a smooth, optically transparent, refractive interface between the hydrophilic environment of the eye and the hydrophobic external environment of the air. This interface is stabilised through synergistic interactions of hydrophilic, amphiphilic and lipophilic tear-film components, including ocular mucins, proteins and lipids. These components work together to continuously lubricate, moisturise, smooth, oxygenate, eliminate waste and protect the ocular surface during and between blink cycles. A COMPLEX STRUCTURE The traditional picture of the tear film consisted of a simple three-layer – mucin, aqueous and lipid – structure. Recent research has revealed it to be much more complex, with more than 18 known mucins, 491 proteins
(identified so far) and at least 153 lipid types – all of which interact to provide structural integrity to the tear film while also performing their individual functions.1-3 And each of the three major components of the tear film is itself multifunctional and complex in makeup. MULTIFUNCTIONAL MUCIN The base layer of the tear film is comprised of tear film mucins, which extend from inside the corneal epithelial cells, through the hydrophobic cell membrane, to the outside of the cell. Called the glycocalyx, these high molecular weight mucins are bound to the cornea on one end but have hydrophilic tails that extend into and hold the aqueous part of the tear film to the cell surface (Figure 1).1 Because cell membranes are largely hydrophobic, without the mucin glycocalyx, tears could run off the corneal surface like water off a Teflon coated frying pan. At the same time, the mucins act as a ‘disadhesive’ so the corneal epithelium does not stick to the tarsal conjunctiva. The functions of the tear film mucins are summarised in Table 1. Free-floating mucins in aqueous Hydrophilic tails Tear mucins bound to the cornea Figure 1. High molecular-weight mucins are bound to the cornea on one end but have hydrophilic tails that extend into and hold the aqueous to the cell surface. Because cell membranes are largely hydrophobic, without these membrane-bound mucins, tears would run off the corneal surface (For illustrative purposes only)
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TABLE 1. FUNCTIONS OF THE TEAR FILM MUCINS • Anchor and stabilise the tear film • Protect ocular surface from abrasion through formation of the glycocalyx • Lubricate cell surfaces so corneal epithelium does not stick to tarsal conjunctiva • Reduce shear stress during blink MORE THAN WATER Other mucins float freely in the tear film’s aqueous component, which functions to clean, protect and transport nutrients and oxygen to the cornea.4 Much more than water, the aqueous contains large and small chemical entities – including the 491 identified proteins – as well as environmental debris that will be disposed of through tear drainage.3 LEARNING ABOUT LIPIDS Above the aqueous is the complex, less well-understood lipid layer. Once considered a simple barrier to prevent evaporation, it is at least a two-layer structure, with polar lipids at the aqueous/lipid interface and a thicker layer of nonpolar lipids (such as waxes, triglycerides, and cholesterol esters) situated above the polar lipids (such as phosphorus-containing lipids) and facing the air.5 The lipid layer aids in lubrication, prevents loss of aqueous, and helps maintain a smooth optical surface. Without the amphiphilic (ie hydrophilic and lipophilic) polar phospholipid interface, nonpolar lipids would spread poorly over the aqueous, creating a less stable lipid layer and leading to more rapid tear film break-up.5 IMPACT OF A CONTACT LENS In healthy eyes, tear film components work in harmony. When the tear film is compromised, such as in dry eye disease or with some systemic medications, this system can break down, leading to dryness and discomfort, corneal staining, conjunctival redness and visual disturbances. What’s more, the changing environments that people experience daily, as well as the intense demands we make on our eyes, all may affect optical performance and comfort. Examples include air conditioned or smoky environments, or working long hours with digital devices. A contact lens changes the ocular surface environment dramatically. The presence of a lens can alter mucin production, aqueous flow rate, and the concentration of certain tear proteins.6 On the eye, a contact lens ‘splits’ the tear film, trapping the vital mucin layer behind the lens, dramatically reducing the volume of aqueous, and disrupting the lipid layer.7 A thinner pre-lens tear film layer increases evaporation and shortens tear film break-up time, which can impact vision.8
SIMULATING THE TEAR ENVIRONMENT An ideal contact lens would create a condition on the lens surface similar to that of the surfaces of the eye, which could help mitigate the negative effects of lens wear on the tear film and surrounding ocular tissues. To do that effectively, a soft lens requires tear-like properties that can interact with and support not just its water component but the full range of tear film constituents: mucins, aqueous and lipids. For example, if the contact lens is to function in a manner that mimics the corneal surface, it must effectively re-create the mucin layer at the lens surface in order to maintain lubrication and, importantly, reduce friction. What happens if friction between the lids and the ocular surface increases as the day wears on – for example, with a contact lens whose surface becomes less lubricous over the course of a day? In this situation, the repeated movement of the eyelid over an increasingly resistive surface thousands of times throughout the day can create a significant amount of additional physical work for the eye.9 This correlates with the common observation that many patients are comfortable in their contact lenses under certain conditions, yet experience symptoms of discomfort or eye fatigue (‘tired eyes’) with different environments, activities or wear times.7,10 In addition to maintaining the physical integrity of the tear film and its components, a contact lens should also maintain the functional elements of the tear film in their natural state. Examples include protecting proteins (such as lysozyme) from denaturation, which can be caused by heat, drying, and exposure to air or chemicals; and shielding lipids from oxidation and degradation resulting from exposure to ultraviolet radiation.11 Not only is this necessary for these components to perform their intended functions, but allowing naturally occurring proteins and lipids to degrade has also been shown in vitro to result in the release of pro-inflammatory substances that can be irritating to the eye.5 The characteristics of tear-friendly contact lenses are summarised in Table 2. TABLE 2. CHARACTERISTICS OF TEAR-FRIENDLY SOFT CONTACT LENSES • Maintain the physical integrity of the tear film and its components • Maintain the functional elements of the tear film in their natural state • Protect proteins (such as lysozyme) from denaturation, which can be caused by heat, drying, and exposure to chemicals • Shield lipids from oxidation resulting from exposure to ultraviolet radiation
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TOWARDS NEW TECHNOLOGIES Comfort remains a key attribute of contact lenses, and dryness and discomfort are the most frequently reported symptoms among those who discontinue contact lens wear.12 Discomfort is often characterised as a feeling of dryness and several tear film factors are associated with contact lens-related dry eye.8 Clinically, the causes of discomfort are very complex, and no single factor has been identified as the culprit: many factors are potential contributors to the issue. The frequency and negative consequences of contact lens discomfort make it crucial for researchers to design lenses that stay comfortable and lubricious throughout the day. Manufacturers have used a variety of methods to try to create a stable pre-lens tear film, such as coating the lens or creating ionic surfaces. One such approach is a new technology that involves working in harmony with the complexity of the natural tear film.
Figure 2. An illustration to demonstrate how a lens material is comprised of an enhanced network of tear-like molecules plus highly breathable hydrated silicone that integrates with the patient’s own tear film
Researchers are developing contact lens materials which have an enhanced network of tear-like molecules plus highly breathable hydrated silicone that integrates with the patient’s own tear film each day (Figure 2). The network of tear-like molecules is uniform throughout the lens, and works consistently all day. The lenses are designed to work with the key tear components to lubricate and moisturise the lens, and support the tear film throughout the day, a concept known as Tear-infused Design. These contact lenses will be commercially available in the coming months. By having a basic understanding of how various contact lens materials interact with the eye and the tear film, we can develop these new technologies that allow us to make better selections and help meet the specific needs of our patients. Bringing together the art of understanding our patient and the science of understanding lenseye interactions also creates a tremendous opportunity for a richer dialogue with our patients. Bart Johnson is senior manager R&D, Dr Brian Pall is senior principal research optometrist and Dr Charles
Scales is principal scientist at Johnson & Johnson Vision Care Inc USA. This article has been adapted from an article appearing in a special edition of the US publication Optometric Management (Johnson B, Pall B and Scales CW. Inspired by the science tears. Optom Man 2015;July:13-16).
REFERENCES 1. Mantelli F and Argüeso P. Functions of ocular surface mucins in health and disease. Curr Opin Allergy Clin Immunol 2008;8:5 477-83. 2. de Souza GA, Godoy LM and Mann M. Identification of 491 proteins in the tear fluid proteome reveals a large number of proteases and protease inhibitors. Genome Biology 2006;7:8 R72. 3. Rantamäki AH, Seppänen-Laakso T, Oresic M et al. Human tear fluid lipidome: from composition to function. PLoS One 2011;6:5 e19553. 4. Abelson M, Dartt D and McLaughlin J. Mucins: foundation of a good tear film. Review of Ophthalmology. November 7, 2011. www.reviewofophthalmology.com/ content/d/therapeutic_topics/c/30968. Accessed September 2, 2015. 5. Green-Church KB, Butovich I, Willcox M et al. The International Workshop on Meibomian Gland Dysfunction: Report of the Subcommittee on Tear Film Lipids and Lipid–Protein Interactions in Health and Disease. Invest Ophthalmol Vis Sci 2011;52:4 1979-93. 6. Rohit A, Willcox M and Stapleton F. Tear lipid layer and contact lens comfort: a review. Eye Contact Lens 2013;39:3 247-53. 7. Nichols JJ, Willcox MDP, Bron AJ et al. The TFOS International Workshop on Contact Lens Discomfort: Executive Summary. Invest Ophthalmol Vis Sci 2013;54:TFOS7-TFOS13. 8. Nichols JJ and Sinnott LT. Tear film, contact lens, and patient-related factors associated with contact lensrelated dry eye. Invest Ophthalmol Vis Sci 2006;47:131928. 9. Tosatti S, Sterner O, Aeschlimann R et al. Tribological classification of contact lenses – from coefficient of friction to sliding work: can contact lens wear help you burn calories? Paper presentation at Nederlands Contactlens Congres, March 2016. 10. Mathews K, Daigle B, Alford J et al. Exploring variability in soft contact lens performance throughout the day. Optician 2016;251:6546 32-34. 11. Buch J, Canavan K, Fadli Z et al. The tear film and contact lens wear. Contact Lens Spectrum 2015;31:2 34-37. 12. Richdale K, Sinnott LT, Skadahl E et al. Frequency of and factors associated with contact lens dissatisfaction and discontinuation. Cornea 2007;26:168-174.
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Redaktörens kommentar: Inledningen presenterar bra vad en ICL lins
är och hur dessa operationer utförs. Med både fördelar och nackdelar. Resultatet är spännande med hur detta upplevts.
Utvärdering av ögontorrhetsparametrar och synskärpa hos patienter som fått Visian ICL implanterat Författare: Petra Hansson, Linnéuniversitetet sammanfattning Catarina Ericson Syftet med studien var att utvärdera ögontorrhetsparametrar och synskärpa hos patienter som fått Visian ICL implanterat och jämföra dem med en tidigare studie gjord om LASIK, för att se vilken metod som gav minst påverkan på patienternas tårfilm och minst biverkningar som torra ögon En grupp på sex stycken som implanterades med en ICL-lins undersöktes på operationsdagen och cirka tre veckor efter operation. Undersökningarna som gjordes var en OSDI-enkät innehållande 12 frågor gällande torrhetsproblem, lipidskikt, NITBUT och tårmenisken utvärderades med hjälp av ett Tearscope, och sist kontrollerades visus. Sex ögon visar på ett tunnare lipidskikt postoperativt, två ögon visar på ett tjockare lipidskikt postoperativt. Medelvärdet på NITBUT ökade från 16,8±6,7 till 20,3±8,9 sekunder postoperativt. två ögon visar på ett försämrat visus postoperativt, 4 ögon visar på ett förbättrat visus postoperativt och sex ögon visar på ett oförändrat resultat. Den här studien visar på att Visian ICL är en bra och säker metod för synkorrigering.
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Utvärdering av ögontorrhet sparametra r och synskärpa h os patienter so Visian ICL implanterat m fått
Författare: Pet ra Ämne: Optome Hansson tri Nivå: Grundn ivå Nr: 2016:O14
http://lnu.diva-portal.org/smash/get/diva2:940777/FULLTEXT01.pdf