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By Laird Harrison
The rate of visual impairment is low in an urban French population over 75, a finding that augurs well for the country’s aging population, researchers say.
Presenting visual acuity was less than 20/60 in only 2.3% of 1153 subjects, report Catherine Creuzot-Garcher, MD, PhD, from the department of Ophthalmology, University Hospital in Dijon, France and six colleagues from four centres in Dijon and Bordeaux, France.
The researchers published these findings from the Montrachet Study (Maculopathy Optic Nerve nuTRition neurovascular and HEarT diseases) in Acta Ophthalmologica online 15 October 2015.
People in developed countries are living longer and longer, they point out, citing one estimate that most people born after the year 2000 will live at least 100 years. But the prevalence of eye diseases, visual impairment and blindness increases with age.
“The burden of these conditions is a great challenge today and in the future for healthcare services and health professionals, but also for caregivers and payers,” Dr. Creuzot-Garchet and her colleagues write.
They cite the Eye Diseases Prevalence Research Group estimate that in the United States, the prevalence of cataract, open-angle glaucoma and late age-related macular degeneration (AMD) will increase by 50%, while low vision will rise by 63% and blindness by 78% percent.
Most population-based studies have looked at a broad range of ages. Only two have described the ocular status of an old French population, Pola (Pathologies Oculaires Lieés a l’Age), conducted in the South and Alienor (Antioxydants, Lipides Essentiels, Nutrition et maladies OculaiRes), conducted in the Southwest.
To better understand the health of French eyes, Dr. Creuzot-Garchet and her colleagues analyzed data from the ongoing Three-City Study, designed to investigate vascular risk factors for dementia.
In the Three-City Study, 9294 community-dwelling people aged 65 and over were selected from the voter roles in Bordeaux, Dijon and Montpellier in 1999. Researchers evaluated the participants every 2 years.
In 1999, researchers offered eye examinations to 4,931 participants in the Three-City Study from Dijon.
From these, the researchers first selected 1,663 participants who had undergone magnetic resonance imaging (MRI). Then they added a random sample of 500 participants without MRI.
All the participants were Caucasians. Their mean age was 82.2 years.
Thee researchers defined myopia as a spherical equivalent of less than -0.5 D, hyperopia as a spherical equivalent over +0.5 D and emmetropia as anything in between. They defined high myopia as less than -5 D and high hyperopia as greater than + 5D.
The researchers found high myopia in 2.2% of the population and high hyperopia in 1.6%. Most of those with hyperopia were 85 years or older.
The researchers found that refractive errors were in accordance with the recent literature in Caucasians. And they noted that refractive errors did not follow a linear trend with age whatever the lens status.
The crude prevalence of best corrected visual acuity less than 20/60 was 1.8% and did not differ significantly from presenting visual acuity (P = 0.39).
The prevalence of visual acuity less than 20/40 was 8.7% presenting and 3.9% best-corrected, a statistically significant difference (P < 0.0001).
Overall, there were no statistically significant differences according to gender. Seven participants (0.6%) were blind according to criteria of the World Health Organization, and this prevalence did not increase in older participants.
The researchers noted a high prevalence of astigmatism. Spherical equivalence decreased significantly with age regardless of the lens status from a median of 0.38 D below 80 years of age to -0.44 D over 84 years, (P < 0.0001).
The researchers hypothesised that in phakic participants, this could be related to the decrease in the prevalence of hyperopia after 75 years, while in pseudophakic participants it could be due to an effort by cataract surgeons to favour near vision in older persons.
About half the population, 49.4%, were pseudophakic, which the researchers noted was much higher than in population-based studies from the 1990s, such as the Beaver Dam Study, where the rate of cataract extraction was 10.6%.
The number of cataract extractions in France rose from 247 300 in 1993 to 667 365 in 2010, the researchers reported, citing French government statistics.
The researchers noted that their findings may not be representative of older French people for several reasons.
First, only 50% of the original population participated. Those who declined may have done so because of more severe visual impairment, making it difficult for them to attend medical appointments.
Second, residents of nursing homes were not included.
Third, all the participants were white and urban.
Fourth, the population was not large enough to capture significant results on eye diseases with a low prevalence. And finally, the investigators limited their definition of visual impairment to visual acuity and did not test contrast sensitivity, glare or stereoacuity.
Dr. Creuzot-Garchet and her colleagues hope to combine their data with those from the Alienor Study, which had the same design, increasing its statistical power. And they hope their data can be sued to elucidate relationships between ocular health and systemic diseases.