To compare treatment with preservative-free dexamethasone 0.1% (Monofree Dexamethason) and diclofenac 0.1% (Dicloabak) eye drops versus preserved dexamethasone 0.1% (Maxidex) and diclofenac 0.1% (Voltaren Ophtha) eye drops after cataract surgery in terms of postoperative inflammation, iatrogenic dry eye disease and cystoid macular edema.

Cataract surgery is a standardized procedure yielding excellent visual outcomes in most patients. According to Daien et al., the incidence of cataract surgery in 2012 in France was 11/1000 person-years. Although there are few complications related to the surgery, patients often experience ocular discomfort in the postoperative period.

Postoperative treatment usually includes topical non-steroidal anti-inflammatory drugs and topical steroids for four weeks to control anterior chamber inflammation, to relieve ocular pain after surgery and to reduce the incidence of cystoid macular edema.

Benzalkonium chloride (BAK) is the most common eye drop preservative and is associated with several ocular adverse effects, including dry eye and ocular surface inflammation. Moreover, in two clinical trials comparing the effects of BAK-containing and preservative-free eye drops, anterior chamber inflammation was reported in response to BAK after 1 month of exposure. Finally, besides the fact that intra-ocular inflammation increases the risk of macular edema, there is some evidence in the literature suggesting that BAK may also contribute to the development of macular edema.

Because of these well-established detrimental effects of preservatives, pharmaceutical industry has invested in the development of preservative-free eye drops in the past decade, which has led to preservative-free alternatives for almost all the eye medications.

The aim of this project is to investigate whether omitting preservatives from the postoperative topical treatment after cataract surgery can reduce symptoms and signs of ocular surface disease, intra-ocular inflammation and the incidence of cystoid macular edema.

Additionally ocular microbiome research is added to our study because of its known correlation with the ocular immunity. Although the ocular surface is continuously colonized by a commensal microbial community, the healthy ocular surface is not in an inflammatory state. This phenomenon suggests that there is an interplay between the ocular surface microbiome and innate immune mechanisms, which prevents inflammatory responses against commensal microbiota.

St Leger et al. used a murine model to reveal the presence of a commensal, Corynebacterium mastitidis, on the ocular surface. Corynebacterium mastitidis elicited an IL-17 response from ƔΔT-cells, facilitating recruitment of neutrophils to the ocular surface and secretion of antimicrobial peptides in the tears. These findings suggest the presence of a functional resident microbiome on the ocular surface which contribute to immune homeostasis and protects the ocular surface from pathogens.

Our expert in the area of ocular microbiome research is affiliated with the department of biochemistry and microbiology of the University of Ghent.

Inclusion Criteria:

• Patients diagnosed with age-related cataract
• Age 60 years or above

Exclusion Criteria:

• Unwilling to sign informed consent
• Pseudoexfoliation syndrome
• Functionally monocular patient
• Any use of eye drops during at least 3 months before surgery with the exception of artificial tears
• Pre-existing dry eye disease according to the criteria's of the TFOS DEXS II report
• Previous ocular surgery, laser treatment or uveitis, with the exception of retinal laser treatment (more than 6 months ago) and iridotomy (more than 6 months ago)
• Active conjunctivitis
• Wearing of contact lens
• Presence of any macular diseases possibly impacting visual acuity
• Presence of any ocular diseases leading to difficulty to have a correct eye examination
• Known or suspected allergy to any of the ingredients on the study medications
• Presence of uncontrolled systemic disease