ENGLISH SUMMARY: Glaucoma is a leading cause of the global prevalence of irreversible blindness. The pathogenesis of glaucoma is not entirely known, but the major risk factors include advancing age, genetic predisposition, and increased intraocular pressure (IOP). The only evidence-based treatment is a lowering of IOP through the use of eye drops, laser procedures, or surgical interventions. Although laser treatment is gaining recognition as a first-choice treatment option, the most common approach for managing glaucoma is IOP-lowering eye drops. A major challenge in the treatment is the occurrence of adverse events and poor adherence. In this context, the ocular surface is an area of great concern, as most glaucoma patients have dry eye disease (DED), which is largely caused by eye drops. Preservation with benzalkonium chloride (BAK) is a controversial topic due to its potential role as a significant cause of DED. A systematic review and meta-analyses investigate potential differences in efficacy and safety between BAK-preserved and BAK-free anti-glaucomatous eye drops (I). Many of the included studies report on ocular surface damage caused by the application of BAK-preserved eye drops. However, the meta-analyses addressing hyperemia, number of ocular adverse events, and tear break-up time did not identify any significant differences. The latter is likely due to varying measurement methods, different endpoints, and study durations. It is, therefore, possible that the large variations between the studies conceal differences in the safety profiles. The efficacy meta-analysis finds that there are no differences in the IOP-lowering effect between BAK-preserved and BAK-free eye drops, indicating that BAK is not necessary for the effectiveness of eye drops. To promote more homogeneous choices of endpoints and methods when evaluating BAK-preserved and BAK-free glaucoma treatments, a Delphi consensus statement was performed. In this study, glaucoma experts and ocular surface disease experts reached consensus on the key factors to consider when designing such studies (II). The hope is to have more studies with comparable endpoints that can systematically show the potentially adverse effects of BAK. The preclinical studies in the current Ph.D. research focus on conjunctival goblet cells (GCs). GCs are important for the ocular surface because they release the mucin MUC5AC, which is an essential component of the inner layer of the tear film. BAK preservation may damage the GCs and result in a low GC density, leading to an unstable tear film and DED. The most commonly used IOP-lowering drugs are prostaglandin analogs (PGAs). Thus, the conducted studies investigate the effect of PGAs preserved in different ways on GCs. BAK-preserved latanoprost is cytotoxic to primary cultured human conjunctival GCs and results in a scattered expression of MUC5AC, in contrast to negative controls, where MUC5AC is localized around the cell nucleus (III). Preservative-free (PF) latanoprost is not cytotoxic and does not affect the MUC5AC expression pattern. Furthermore, BAK-preserved travoprost is found to be cytotoxic in a time-dependent manner, while Polyquad (R)-preserved travoprost does not affect GC survival at any measured time point (IV). Both Polyquad and BAK induce scattered expression of MUC5AC. The cytotoxicity of BAK-preserved PGA eye drops is higher compared to the safer profile of PF and Polyquad-preserved PGA eye drops (V). Additionally, PF latanoprost does not increase the release of the inflammatory markers interleukin (IL)-6 and IL-8, unlike BAK-preserved latanoprost. A review highlights the active and inactive components of IOP-lowering eye drops (VI). Several preclinical and clinical studies have identified adverse effects of BAK. Although other components, such as the active drug and phosphates, can also cause adverse events, the review clearly states that BAK alone is a major source of decreased tolerability. The conclusion of this thesis is that BAK preservation is unnecessary and harmful to the ocular surface. The preclinical studies demonstrate that GCs die when exposed to BAK. Furthermore, they find that BAK induces a pro-inflammatory response. The review included in the thesis concludes that BAK should be phased out of eye drops for chronic use. Overall, the inclusion of BAK poses a risk of developing DED and poor adherence, which can ultimately lead to disease progression and blindness. Danish Summary: Glaukom (gron st AE r) er en af de hyppigste arsager til blindhed pa verdensplan. angstrom rsagen til glaukom kendes ikke, men de v AE sentligste risikofaktorer er alder, genetik og forhojet intraokul AE rt tryk. Den eneste evidensbaserede behandling er s AE nkning af ojentrykket med enten ojendraber, laser eller kirurgi. Omend laserbehandling er blevet tiltagende anerkendt som forstevalgsbehandling, er ojendraber den mest udbredte behandlingsform. Da ojendraber mod glaukom kan medfore v AE sentlige bivirkninger, er det en stor udfordring, at patienter med glaukom ikke bruger deres ojendraber korrekt. I denne sammenh AE ng er ojenoverfladen et omrade, der v AE kker bekymring, da langt de fleste glaukompatienter lider af ojenoverfladesygdom, som overvejende skyldes ojendrabebehandling. Konservering med benzalkoniumklorid (BAK) er kontroversiel, da BAK menes at v AE re en v AE sentlig arsag til ojenoverfladesygdom. Et systematisk review og metaanalyser undersoger forskelle i effekt og bivirkningsprofil mellem BAK-konserverede og BAK-frie ojendraber (I). Flere studier rapporterer om skade pa ojets overflade ved brug af BAK-konserverede ojendraber. Dog findes der ikke forskelle i metaanalyserne, der undersoger hyper AE mi, antal lokale bivirkninger og tareopbrydningstid. De inkluderede studier har meget varierende outcomes, varighed og malemetoder. Det er derfor muligt, at de store variationer studierne imellem maskerer BAK's egentlige toksiske effekt. I metaanalysen, der undersoger drabernes tryks AE nkende effekt, findes der ingen forskel mellem BAK-konserverede og BAK-frie ojendraber, hvilket indikerer, at BAK ikke er nodvendig for drabernes tryks AE nkende effekt. For at bane vejen for mere ensartede valg af end points og metoder i kliniske forsog, der undersoger BAK-konserverede og BAK-frie antiglaukomatose ojendraber, er der lavet et Delphi konsensus studie (II). I studiet er eksperter i glaukom og overfladesygdom blevet enige om de vigtigste elementer, der bor inkluderes, nar sadanne kliniske studier designes. Habet er at oge m AE ngden af studier med sammenlignelige end points og metoder som systematisk kan vise BAK's potentielt uhensigtsm AE ssige effekt pa ojendrabers bivirkningsprofil. De pr AE kliniske studier i den foreliggende afhandling fokuserer pa de konjunktivale b AE gerceller, da b AE gercellerne er vigtige for ojets overflade. B AE gerceller frigiver mucinet MUC5AC, som er en vigtig bestanddel i tarefilmens inderste lag. BAK-konservering kan beskadige b AE gercellerne og forarsage lav b AE gercelledensitet. Dette vil medfore en ustabil tarefilm og ojenoverfladesygdom. Da de hyppigst anvendte tryks AE nkende ojendraber er prostaglandinanaloger (PGA), undersoges hvorledes forskelligt konserverede PGA-ojendraber pavirker b AE gercellerne. BAK-konserveret latanoprost er toksisk overfor prim AE re humane konjunktivale b AE gercellekulturer og forarsager spredt ekspression af MUC5AC. Dette er sammenlignet med negative kontroller, hvor MUC5AC er lokaliseret rundt om cellekernen (III). Konserveringsfri latanoprost er ikke cytotoksisk og pavirker ikke MUC5AC ekspressionen. Ydermere er BAK-konserveret travoprost tidsafh AE ngigt toksisk, hvilket ikke er tilf AE ldet for Polyquad (R)-konserveret travoprost (VI). Bade BAK- og Polyquad-konserveret travoprost forarsager spredt MUC5AC ekspression. BAK-konserverede PGA-ojendraber er mere toksiske end PF og Polyquad-konserverede PGA-ojendraber (V). Derudover oger BAK-konserveret latanoprost frigivelsen af IL-6 og IL-8, hvilket PF latanoprost ikke gor. Et review fokuserer pa bade de aktive og inaktive komponenter i tryks AE nkende ojendraber (VI). Flere kliniske og pr AE kliniske studier viser, at BAK er skadeligt. Mens andre komponenter sasom det aktive stof og fosfater ogsa kan v AE re arsag til bivirkninger, fremgar det tydeligt af reviewet, at BAK alene er en betydelig kilde til ojenoverfladesygdom. Konklusionen pa denne afhandling er, at BAK konservering er unodvendig og skadelig for ojets overflade. I de pr AE kliniske studier findes det, at BAK dr AE ber b AE gercellerne og forarsager et inflammatorisk respons. Det inkluderede review konkluderer, at BAK bor udfases fra ojendraber, der bruges livslangt. Overordnet set oger BAK risikoen for at udvikle ojenoverfladesygdom, hvilket gor, at patienterne ikke bruger deres ojendraber korrekt. Dette kan ultimativt fore til sygdomsprogression og blindhed.
