Eyeworld

by Douglas J. Rhee, MD Advanced diagnostic measurement for better disease management D iagnosis and detec- tion of glaucomatous progression remains a challenge; detection relies on examination of the structural damage to the optic nerve, combined with measure- ment of visual function. 1 Unfor- tunately, changes in structure and function do not always agree in patients, 2 making the diagnosis more difficult. As clinicians, we often concentrate so much on preparametric glaucoma that we forget the first defect is a visual field defect in half our patients. Numerous studies have shown what we note in clinical prac- tice—10% of all patients will be- come legally blind or lose vision altogether over a 20-year period. 3 Early diagnosis is the only means to prevent this type of glaucoma damage. We currently have three methods to quantitatively analyze the nerve fiber layer (NFL) thick- ness, including optical coherence tomography (OCT), Heidelberg Retina Tomograph (HRT), and nerve fiber analyzer (GDx), which uses polarized light to look at the NFL. In the past 10 years, OCT has become a mainstay in our armamentarium. Spectral-domain OCT (SD-OCT) offers benefits over early generation time-domain OCT because of increased axial resolution, faster scanning speeds, and improved reproducibility but similar diagnostic accuracy, 4 and allows for gaze tracking so the optic nerve remains centered. For clinicians without SD-OCT, Douglas J. Rhee, MD continued on page 5 time-domain can still be a valu- able tool. There are three main reasons to use OCT: to rule out glaucoma and rule out healthy suspects; to understand the areas of abnormal- ity and how intensively to treat; and to determine if treatment needs to be advanced based on disease progression. Using OCT to rule out healthy patients In this case, a 64-year-old male of African descent had a family history of glaucoma. In Figure 1, imaging and central thickness are on the borderline stage, as is his IOP. But Figure 2, a time-domain OCT reading, clearly shows this Dr. Lewis: Is there a difference in the strength of the prostaglan- dins? Dr. Radcliffe: There are 20–30 studies that have compared the prostaglandins, and while some have shown similar efficacy be- tween latanoprost, travoprost, and bimatoprost, many have shown travoprost and bimatoprost to have better efficacy than lata- noprost. Once you add another medication, you run the risk of diminishing patient compliance, so it might make the most sense to use a more potent prostaglan- din analog before adding to latanoprost. Dr. Lewis: What are the pros/cons to adding a second medication? Dr. Radcliffe: Beta blockers are (perhaps) our most trusted mole- cule. We don't have many formu- lary concerns with beta blockers. Adding them has been shown in studies to reduce the hyperemia rate, lower allergy responses, and enhance tolerability. Brand name vs. generic Dr. Radcliffe: The Food and Drug Administration requires the con- centration of the active ingredi- ent, and any of the excipients, be the same in the generic as in the name brand. The main difference is human clinical trials on the generic product are not going to show efficacy. That's often where concerns arise. Dr. Rhee: Generics are often less expensive for the patient, and that can make a difference. But branded products have their role, and if efficacy or side effects are an issue, they may be preferred. Dr. Francis: Generics have a place because of cost. But there's no control over how the drug is compounded in terms of the order of the ingredients. The manufac- turing process and the steps are not necessarily the same as the original drug. Drug delivery Dr. Lewis: What are your thoughts about the new drug de- livery systems being investigated? Dr. Rhee: I'm impressed with how much easier patients accept the concept of an implantable drug delivery system. There seems to be a clinical impression that a laser is much more invasive than inject- ing something into the eye. " While OCT has vastly improved our ability to diagnose and manage glaucoma, we cannot overlook the importance of visual field testing. " –Douglas J. Rhee, MD Supported by unrestricted educational grants from Aerie, Alcon Laboratories, Allergan, Carl Zeiss Meditec, and Glaukos 3

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