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.
As a rule, you should not go more than two years without having your eyes examined. Diabetic patients, people with a family history of eye diseases, and anyone whose general health is poor or who is taking medications that may have potential side effects on the eye may need an eye exam at least once a year.