Article

CLINICAL: GLAUCOMA

DROPPING THE DROPS

DRUG-DELIVERY CONTACT LENSES COULD SOLVE NON-COMPLIANCE

PATIENT ADHERENCE to glaucoma eye drops remains poor, with 50% of patients who filled their prescriptions discontinuing use within six months, reveals a classic study in the American Journal of Ophthalmology.

The 11 barriers to medication compliance: (1) skepticism of vision loss, (2) skepticism drops will mitigate vision loss, (3) poor self-efficacy, (4) poor knowledge regarding the disease, (5) mistrust of doctor, (6) drop-instillation difficulty, (7) drug cost, (8) drug side effects, (9) patient forgetfulness, (10) issues with medication schedule and (11) life stress, reports the July 2015 issue of Ophthalmology.

A solution to most of these barriers could be the prescription of a slow drug-releasing delivery system, such as a contact lens — the theme of this issue and something in the optometrist’s wheel house. (See “Other Drug Delivery Systems in the Works.”)

Here, I discuss the clinical advantage of this technology and where it stands regarding availability.

CLINICAL ADVANTAGE

The limited mixing between the drug-releasing contact lens and the cornea in the post lens tear film leads to more than 30 minutes of drug residence time on the cornea vs. 5 minutes of residence time from eye drops, reports a 2012 study in the Journal of Controlled Release.

Given that scores of studies show treating glaucoma with ocular hypotensive drugs delays the development of primary open-angle glaucoma and, therefore, the progression of VF loss, a drug-releasing contact lens represents an enormous patient benefit.

One caveat: Many glaucoma patients experience concomitant dry eye disease that, therefore, might limit contact lens wear.

Other Drug-Delivery Systems in the Works

  • Bimatoprost
    (Lumigan, Allergan)
    intraocular implant
  • Bimatoprost
    (Lumigan, Allergan)
    ocular insert
  • Latanoprost
    (Xalatan, Pfizer)
    punctal plugs
  • Travoprost
    (Travatan Z, Alcon)
    intraocular implant
  • Travoprost
    (Travatan Z, Alcon)
    punctal plugs

AVAILABILITY

We’re getting close. For example, a latanoprost (Xalatan, Pfizer)-eluting contact lens used in monkeys was shown to be at least as effective as the delivery of daily drop instillation, reports a 2016 study in the American Academy of Ophthalmology.

The study’s authors say more research is needed to determine the optimal continuous-release dose required and the tolerability of the lenses through an extended period.

The lens is designed with a thin polymer film that holds the drug in its periphery. The lens center and rim are clear to allow no decrease in VA, normal oxygen transmission and normal hydration. The next step is clinical trials to determine the safety and efficacy of the contact lens in humans. OM