Ambio 22: 417-426. soil organic matter and acid soils predominate. case in many of the soils inthe warm-humid tropics. of agricultural and charcoal production. cut and burned to allow planting of crops. cycles before the land has to revert back to fallow. and added to soil.
It's important for adults 40 and older to have eye exams every 2 to 4 years to check for problems. Those who have a history of eye problems or who are at risk for developing them should see an eye doctor every year. This is particularly important if you have risk factors or a family history of eye problems.
According to the American Optometric Association (AOA), infants should have their first comprehensive eye exam at 6 months of age. Children then should have additional eye exams at age 3, and just before they enter the first grade  at about age 5 or 6. For school-aged children, the AOA recommends an eye exam every two years if no vision correction is required.