Research Digest

Glycemic Control Linked to Progression of DR

An evaluation of factors associated with the progression of diabetic retinopathy (DR) over a 25-year period in Type 1 diabetes patients identified glycemic control as "strongly related" to whether the disease worsened to proliferative diabetic retinopathy (PDR), or improved.

In a study recently reported in Ophthalmology, researchers examined 955 patients diagnosed with Type 1 diabetes mellitus before the age of 30. The patients were a cohort of the Wisconsin Epidemiologic Study of Diabetic Retinopathy. They received baseline exams between 1980 and 1982. Surviving patients were then evaluated at at least one of the following four time periods: after 4, 10, 14 or 25 years. Five hundred and twenty patients completed the 25-year follow up. Stereoscopic color fundus photographs were graded using the modified Airlie House classification and the Early Treatment Diabetic Retinopathy Study retinopathy severity scheme.

The 25-year cumulative rate of progression of DR was 83%; progression to PDR was 42% and improvement of DR was 18%.

Results showed that glycemic control (assessed via blood levels of glycosylated hemoglobin A1) at baseline and throughout the study was a strong indicator of whether a subject's DR worsened or improved. Improved glycemic control was associated with significant reduction in DR progression and increased improvement in DR regardless of how long the patient had had Type 1 diabetes or the level of DR at baseline.

The study authors also determined the following additional risk factors for progression to PDR: male gender (associated with a 33% higher risk of progression and a 45% lower risk of regression), higher blood pressure (though less strongly associated with the progression and improvement of DR), presence of protein in urine and a greater body mass index as measured at baseline.

"The study has many strengths," the authors write, "including a large cohort with a broad distribution of severity of retinopathy at baseline, a low refusal rate and the use of standardized protocols of measurement."

Based on their findings, the researchers predict that 185,000 to 466,000 Americans with Type 1 diabetes will develop to PDR over a 25-year period. However, they caution that the numbers may be overestimated, as the incidence of PDR has declined in people diagnosed with Type 1 diabetes in recent years. It is speculated that improvement in diabetes care over the period of the study is the reason. OM

Reference

1. Klein R, Knudtson MD, Lee KE, Gangnon R, Klein BEK. The Wisconsin Epidemiologic Study of Diabetic Retinopathy XXII. Ophthalmology. 2008;115:1859-1868.

Soft Contact Lenses And Myopic Creep in Children

Results of a 3-year study show that soft contact lens wear in children does not cause "relevant increases in axial length or corneal curvature," according to an article published in the November issue of Investigative Ophthalmology & Visual Science.¹

Addressing concerns that soft contact lens wear in children increased the progression of myopia, the multisite study involved 484 children between the ages of 8 to 11 with –1.00 to –6.00 D of myopia and > 1.00 D of astigmatism. Subjects were randomized to spectacle- or contact lens-vision correction.

Researchers measured refractive error and corneal curvatures annually by cycloplegic autorefraction; they measured axial length annually by A-scan ultrasound. Measurements were conducted prior to randomization and annually, with 96.5% of the subjects examined at the final visit.

The average rate of myopic progression was 0.06 D per year greater for contact-lens wears than spectacle wearers — a finding that was statistically significant. However, after 3 years, the adjusted difference between contact lens wearers and spectacle wearers was not statistically significant (95% confidence interval = –0.46 to 0.02). Researchers found no difference between the two treatment groups in change in axial length (ANCOVA, P = 0.37) or change in the steepest corneal curvature (ANCOVA, P = 0.72).

The study was the largest randomized trial of its kind. It was conducted from September 2003 to October 2007 at five U.S. sites and was supported by funding from Vistakon. OM

Reference

1. Walline JJ, Jones LA, Sinnott L, Manny RE, Gaume A, Rah MJ, Chitkara M, Lyons S., on behalf of the ACHIEVE Study Group. A Randomized Trial of the Effect of Soft Contact Lenses on Myopia Progression in Children. Inves Ophthal & Vis Sci. 2008;49:4702-4706.