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Keep tear film in mind when treating glaucoma patients with dry eye
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A: Chronic exposure to BAK can harm epithelium
 Katherine Mastrota | ||
Katherine Mastrota, OD, MS: Pre-existing dry eye in glaucoma patients complicates both medical and surgical management of glaucoma.
In dry eye, the ocular surface suffers from deprivation of the normal protective, nutritive and healing properties of the tear film. The changes in tear quality, quantity and osmolarity cause increased levels of inflammatory mediators and ultimately may lead to conjunctival and corneal epithelial cell dysfunction and perhaps early cell apoptosis.
The Palisades of Vogt, situated at the corneal limbus, house corneal epithelial stem cells that are responsible for corneal epithelial maintenance, turnover and healing; similarly, conjunctival stem cell reservoirs, dispersed throughout the conjunctival surface, primarily in the fornix, resurface conjunctival epithelial cells.
Benzalkonium chloride, in most ophthalmic preparations, is an effective preservative that can potentiate the effect of antimicrobials. However, as a detergent, chronic administration of BAK-containing medications, such as glaucoma medications, can be deleterious to surface epithelial cells and, perhaps, have far-reaching effects altering the stem cell environment and function. This added insult to a dry eye patient can lead to inflamed, uncomfortable eyes in patients who suffer both disease entities and intolerability of the hypotensive agents.
In patients whose uncontrolled glaucomatous disease warrants further intervention, dry eye disease can be problematic. If laser therapy is unsuccessful in reducing IOP to satisfactory levels, most surgeons will opt to perform a trabeculectomy. Usually the IOP post surgery is low enough to allow the treating physician to discontinue topical hypotensive medications, which is particularly welcomed in the dry eye patient. However the use of intraoperative antimetabolites (to reduce bleb scarring and failure) challenges the healing process of the already dry eye-challenged conjunctival epithelium. Chronic dry eye-induced conjunctival inflammation may predispose the patient to bleb failure.
Added to this is the fact that the dry eye, with decreased tear film lubricity, has increased friction and “stickiness” as the lid crosses the filtering bleb. Later on, this can create a small tear in the bleb allowing for bleb leakage and the attendant complications of increased infection risk and hypotony.
With a reduced tear volume, dellen formation adjacent to the bleb is also not uncommon. With the natural antimicrobial and protective properties of the tear film less effective in dry eye, the post-trabeculectomy eye, already at added risk for infection, is doubly challenged. Reducing the bacterial load on the eyelid and lash surfaces is prudent and effectively managed with a commercially prepared hygiene product such as OcuSoft lid foam (Cynacon/OcuSoft, Richmond, Texas). Diligent monitoring of these patients for postoperative blebitis and endophthalmitis is critical.
For more information:
- Katherine Mastrota, OD, MS, is center director at Omni Eye Surgery, 36 East 36th Street, New York, NY 10016; (212) 353-0030; fax: (212) 353-0083; e-mail: KatherineMastrota@msn.com. She is a member of the medical scientific advisory board for Cynacon OcuSoft.
A: Use the fewest number of medications as possible
Kathy Yang-Williams, OD, FAAO: The goal of treatment is to reduce IOP using the fewest number of medications and fewest applications of medication possible. We need to tailor the treatment regimen to decrease the range of side effects experienced by the patient and structure the treatment plan in such a way that it does not compromise compliance or persistency.
 Kathy Yang-Williams |
Benzalkonium chloride is a common ocular preservative that can exacerbate ocular surface disease. Timolol and pilocarpine 2% are available in a nonpreserved unit dose format; however, these medications tend to be more expensive and are less widely available than commercial preparations. Newer medications have replaced BAK with other preservatives that are gentler to the ocular surface. For example, Alphagan P (brimonidine tartrate 0.15%, Allergan) is preserved with Purite, Timoptic XE (0.25% timolol maleate, Merck) is preserved with benzododecinum bromide and Travatan Z (travoprost, Alcon) is preserved with SofZia.
Combination agents such as Cosopt (dorzolamide HCL, timolol maleate, Merck) and Combigan (0.2% brimonidine tartrate, 0.5% timolol maleate, Allergan) provide other options for decreasing ocular surface toxicity because fewer drug applications are required compared to the use of individual component drugs.
Prostaglandin analogs (bimatoprost, latanoprost and travoprost) have been shown to be efficacious and typically well tolerated by patients relative to other glaucoma medications. Conjunctival hyperemia occurs less frequently with latanoprost, and I have found that patients demonstrate better compliance with their therapy when ocular side effects are minimized. We must balance the efficacy of the treatment with the adverse effect profile because the medication can be effective only if the patient complies with therapy.
Surgical options should be considered for patients who require additional IOP lowering. The use of laser trabeculoplasty is a useful adjunct to a medical treatment plan, especially when there is significant epithelial compromise. Trabeculectomy and drainage implant procedures can also be considered for IOP lowering effect; however, these surgical techniques can affect the tear flow across the ocular surface. Bleb dysesthesias, or a symptomatic bleb, can create additional tear film irregularities that exacerbate symptoms for patients with dysfunctional tear syndrome.
Newer glaucoma surgeries such as viscocanalostomy, ab interno trabeculectomy (Trabectome, NeoMedix), canaloplasty with or without tensioning suture and trabecular micro-bypass (iStent, Glaukos) reduce IOP without the creation of a subconjunctival bleb. These procedures might be more suited to patients who already have a compromised tear flow pattern.
For more information:
- Kathy Yang-Williams, OD, FAAO, can be reached at Roosevelt Vision Source, 7001 Roosevelt Way NE, Seattle WA 98115; (206) 527-2987; fax: (206) 526-8076; e-mail: kyangwilliams@q.com. Dr. Williams has no direct financial interest in any products she mentions. She is a paid consultant to Pfizer.