A long-sighted person can only see clearly looking into the far distance if the muscular focusing system inside the eye is used. With hyperopia, the long-sighted eye has to work harder than a normal eye at all distances. Long-sightedness can cause eyestrain, headaches, poor concentration, double vision, or blurred vision when looking up from close work.
Hyperopia is due to the eye being smaller than normal. Clear vision is impossible unless the power of the optical system is increased either by the eye increasing its focusing effort or by using spectacles or contact lenses.