How can the MEGA act as a universal lens for a range of nearsighted divers?
A The MEGA behaves like a – 4.5 diopter lens when submerged. However since you’re imaging in water and not air, the actual power works a little different… but calling it – 4.5 is close enough. When we were kids, we all had tremendous ability to focus close — technically called “accommodating excess negative diopter.” Your age is the biggest “driver” influencing your close-focus ability, as shown in this chart; we all lose close-focusing ability as we age. Eventually we all need reading glasses. This means that a diver in their early 30’s can still see OK, even if the prescription eyewear is too strong (i.e. -4.5 lenses for + 3.0 eyes) but IN AIR, several “cues” tell you this is the wrong prescription: 1. Object distance appears greater than reality 2. Object size appears smaller than reality 3. Barrel distortion (image curvature) at edges of your view 4. Closest focus-point is now further from your eye Because each of your eye’s rotation points is concentric with each MEGA dome lens
