Abstract
Abstract: :
Purpose:To determine the location and natural history of epiretinal membranes in a random sample of the population aged 40 years and older in urban Melbourne, Victoria, Australia. Methods:Cluster sample of population aged 40 years and older was drawn from nine randomly selected pairs of adjacent census collector districts in urban Melbourne. Detailed eye examination was conducted. Colour fundus stereo photographs were taken. 3271 persons (83% of the eligible) were examined at the baseline examination during 1992-94 and of them 2594 persons (85% of the eligible) participated in the followup examination. The average duration between baseline and followup examination was 4.5 years (range 4 to 7years). ERM were diagnosed clinically and from fundus photographs. They were classified into an early form without retinal folds (termed cellophane macular reflex (CMR)), which was further divided into CMR typeI and CMR typeII depending upon their size, or a late form with retinal folds (termed preretinal macular fibrosis(PMF)). The progression or regression of ERM found at the baseline examination was studied in a masked manner from the stereo photographs taken at baseline and followup examination. The site of the ERM was determined by using a macular grid. Results:Prevalence of the ERM was 5.9% (95% CI=5.2-6.6%) at the baseline examination. Prevalence of CMR typeI was 3% (86 individuals), for CMR typeII it was 1% (29 individuals) and it was 1.9% (54 individuals) for PMF at baseline.ERM was overlying the fovea in 28% of cases while it was nasal to fovea in 66%, temporal 52%, superior 67% and inferior 46% of cases. At followup 30% of all ERM progressed in size. 21.6% of ERM progressed from one type to another. 11.8% of CMR typeI progressed to CMR typeII, 3.9% of CMR typeI changed to PMF and 5.9% of CMR typeII became PMF at followup.Mean visual acuity at baseline for all ERM types was 53.04 (SD9.26) letters which at followup decreased to 49.95 (SD10.53) letters (p<0.001). Mean visual acuity for all CMR (CMR typeI & typeII) at baseline was 54.17 (SD4.15) letters which detrioated to 51.98 (SD6.14) letters (p<0.001), while it was 49.28 (SD14.78) letters for PMF at baseline which went down to 45.43 (SD15.79) letters at followup examination (p<0.001). Conclusion:To our knowledge this is the first population based study of the natural history of epiretinal membranes. We found that 30% of all ERM increased in size, while 9.8% of CMR (either typeI or typeII) progress to PMF and both CMR and PMF caused significant worsening of vision at a mean followup of 4.5 years.
Keywords: 460 macula/fovea • 352 clinical (human) or epidemiologic studies: natural history • 554 retina