A study finds Iowa has the nation’s second-highest rate of vision impairment or blindness in people over 40 years old. North Dakota ranked first. Des Moines ophthalmologist Dr. David Ball explains Iowan is in such sorry shape because of its aging populace. As people live longer and healthier lives, they become at risk for developing other eye problems. Dr. Ball, who specializes in treating glaucoma, says Iowans should give serious consideration to their eye health.He says people should visit the eye doctor every other year after they turn 40 as prevention is the strongest medicine. Dr. Ball says there’s no science to back up the old wive’s tale about carrots being good for the eyes, but he says the orange veggies are part of the wellness package.The study was released by the National Eye Institute. One-point-three million Iowans, or about 45-percent of the state’s population, are at least 40 years old.