Optical Coherence Tomography Useful for Macular Edema

May 16, 2012 (Chicago, Illinois) — In patients with diabetic macular edema, visual acuity (VA) correlates with the magnitude of change in central macular thickness (CMT). The strongest correlation with VA is the absolute (correlation coefficient, 0.416; P =.016) and relative (correlation coefficient, 0.398; P =.022) change in CMT from baseline to the first laser photocoagulation. CMT taken at a single time point is not as strongly correlated with CMT (correlation coefficient, 0.322; P = .004).

Here at the American Society of Cataract and Refractive Surgery 2012 Symposium on Cataract, IOL and Refractive Surgery, M.C. Chew, MBBS, from the Eye Institute of Singapore, described the use of optical coherence tomography (OCT) measurements of macular thickness and VA in patients with diabetic macular edema.

Dr. Chew explained to Medscape Medical News that "OCT is an imaging modality that is...almost like histology, but noninvasive."

Diabetes mellitus is a major cause of blindness worldwide. Diabetic macular edema is the leading cause of vision loss among patients with diabetes.

Prevalence estimates of macular edema in patients with diabetes range from 2% to 10%. The Wisconsin Epidemiological Study of Diabetic Retinopathy calculated the prevalence of macular edema in patients with diabetes to be as high as 11.1%. The response of macular edema to treatment varies; some patients require prolonged and/or repeated treatment.

Dr. Chew described both quantitative (retinal thickness) and qualitative (patterns of diabetic macular edema as seen by OCT) assessments.

Patients were treated with laser photocoagulation, and VA and change in VA were measured (treatment outcomes).

OCT and VA measurements were performed on the same visit. The correlation between OCT and VA was made at a single time point and at 2 different time points. Sections were reviewed for adequate quality. OCT measurements included central retinal thickness and mean inner subfield thickness.

The researchers reviewed 42 patients with diabetes and newly diagnosed macular edema over a 3-month period. Average patient age was 61.5 years (range, 47 to 88). Patients were excluded from the study if they had received previous laser photocoagulation treatment for macular edema, panretinal laser photocoagulation in the previous 3 months, or cataract extraction/intraocular surgery in the previous 6 months.

The patient population was 57.1% Chinese, 21.4% Malay, 19% Indian, and 2.4% other. The patient population was 54.8% female.

VA Correlated With CMT

Although VA correlated with CMT, its correlation with mean inner subfield thickness was only of borderline significance (correlation coefficient, 0.221; P = .05).

Dr. Chew reported that 73.9% of patients with diabetic macular edema had an OCT type 1 pattern of diffuse retinal swelling. The type 1 pattern correlated better with VA (correlation coefficient for absolute change, 0.852; P < .001) than the type 2 pattern (data not shown).

David Irvine, MD, from the Eye Care Group of Memphis, Tennessee, discussed the research with Medscape Medical News, and explained that "OCT is a device that we rely on heavily these days for imaging the retina.... This talk confirmed what we hoped."

Dr. Chew and Dr. Irvine have disclosed no relevant financial relationships.

American Society of Cataract and Refractive Surgery (ASCRS) 2012 Symposium on Cataract, IOL and Refractive Surgery. Presented April 21, 2012.