What is meaning of +- 4D in eye for job application requirement

power 4dPower of the lens (P) = 4 D. Refractive Index (r) = 1.5. To Find: The radius of curvature. Calculations: The following equation determines a lens's power: where P is the power ofPower Workout 4D brings Fitness Information and Tips for people looking Easy Exercises and Workouts to Get in Shape and Lose Weht at Home without going to gym.