Ocular Surface and External Filtration Surgery: Mutual Relationships

Abstract

There is a large body of evidence from clinical and experimental studies that the long-term use of topical drugs may induce ocular surface changes, causing ocular discomfort, dry eye, conjunctival inflammation, subconjunctival fibrosis, corneal surface impairment, and, as a consequence of chronic ocular surface changes, the potential risk of failure for further glaucoma surgery. Subclinical inflammation has also been widely described in patients receiving antiglaucoma treatments for long periods of time, with inflammatory cell infiltration and fibroblast activation in the conjunctiva and subconjunctival space. The preservative, especially benzalkonium chloride, which has consistently demonstrated its toxic effects in laboratory, experimental, and clinical studies, could induce or enhance such inflammatory changes. As a quaternary ammonium, this compound causes tear film instability, loss of goblet cells, conjunctival squamous metaplasia and apoptosis, disruption of the corneal epithelium barrier, corneal nerve impairment, chronic inflammation and potential damage to deeper ocular tissues. Drug-induced adverse effects are therefore far from being restricted to only allergic reactions, but they are often very difficult to identify because they mostly occur in a delayed or poorly specific manner, and result from complex and multifactorial interactions between the drugs and the ocular surface. Postoperatively, the ocular surface also plays an important role, as the conjunctiva interacts with aqueous humor and subconjunctival fibrosis may block aqueous outflow and cause surgical failure. As preoperative inflammation underlies postoperative fibrosis and therefore surgical outcome, a better knowledge of ocular surface changes with appropriate evaluation and management should thus become a new paradigm in glaucoma care over the long term.

Assessment of Corneal Changes Associated with Topical Antiglaucoma Therapy Using in vivo Confocal Microscopy

“…In order to achieve a higher level of compliance with topical A/G treatment, adverse events may be reduced by changing the class of the topical medication, reducing exposure to preservatives or addition of topical lubrication [13]. Cautious surveillance of chronic inflammation of the ocular surface is recommended as its impact could increase the risk of failure of subsequent glaucoma filtration surgery [14,15].…”

Improvement in Glaucoma Patient Quality of Life by Therapy Switch to Preservative-Free Timolol/Dorzolamide Fixed Combination

“…Not only has it been consistently reported to have a noninferiority IOP-lowering profile when compared to these agents [9,25], but it provides a preservative-free alternative in a fixed combination treatment. This may be particularly important if surgery is to be eventually considered, as long-term preservative medication could interfere with conjunctival scarring and therefore affect surgical outcomes [26]. …”

Selective laser trabeculoplasty as an initial treatment option for open-angle glaucoma

“…Ocular and systemic side effects of topical medications, forgetfulness, difficulties in handling the bottle and instill eye drops properly, and consequently poor compliance with the proposed medical regimen are important issues for clinicians when starting a therapy that will last a lifetime (6,8) . Moreover, growing concern exists with drug-related chronic ocular surface inflammation, which may have a negative impact on success of a future filtration surgery (69) . With this in mind, we believe it is reasonable to consider alternative treatments, such as laser therapy, as first-line treatment options (17,28,29) .…”