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Editors Selection IGR 8-3

Epidemiology: Glaucoma as cause of blindness

Comment by Chris Johnson on:

55997 Examining visual field loss in patients in glaucoma clinics during their predicted remaining lifetime, Saunders LJ; Russell RA; Kirwan JF et al., Investigative Ophthalmology and Visual Science, 2014; 55: 102-109

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Previous investigations of the likelihood of glaucoma patients developing visual impairment or statutory blindness have been based on relatively small sample sizes (300 patients or less) and manual perimetric testing, which has been reported to be highly variable and dependent on the skills and experience of the examiner. In the present study, the authors evaluated automated visual field findings on more than 3,700 patients, and used computer modeling and linear regression of Mean Deviation (MD) to estimate the prevalence of visual impairment and statutory blindness over the lifetime of these patients. The authors found that 3% of patients demonstrated a progression of greater than -1.5 dB per year, 10.4% reached visual impairment within their lifetime, and 5.2% achieved statutory blindness.

3% of patients demonstrated a progression of greater than -1.5 dB per year, 10.4% reached visual impairment within their lifetime, and 5.2% achieved statutory blindness

The results for statutory blindness compare favorably with the small sample longitudinal studies using manual perimetric results. There appear to be advantages and disadvantages associated with this procedure. The advantages are that it is possible to provide a prediction of whether glaucomatous visual field loss will produce changes in the patient's activities of daily living and quality of life. It also provides a means of detecting fast versus slow progressors, to direct potential changes in therapeutic intervention. Additionally, the findings are based on existing technology and analysis procedures. The disadvantages are that nearly one third of the potential cases were excluded because they did not meet the reliability criteria established for this study, eliminating a significant portion of the population. Another disadvantage is that this model assumes that the rate of progression will be linear and that this rate will be constant throughout the patient's lifetime, whereas it is likely that the rate may reflect a higher rate of progression as glaucomatous damage increases over time. Finally, it is clear that the testing and analysis procedures for perimetry in glaucoma will change considerably over a reasonable time period, so that current assumptions and methods may not be suitable for the future. A dynamic model may be preferable for future purposes.

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