Hi abman,
The definitive answer to your question is
maybe. There is a BIG advantage if the mask is technically too strong for you, as long as it is still comfortable for your eyes to maintain focus. Our diving eye doctors under 40-years old prefer to wear a contact lens Rx that causes the mask to be technically too strong. Why? Because it enhances contrast / resolution everything looks more vivid hyper acuity you never even experience when above water. But this is not the right answer for everybody.
Bear with me
THREE factors determine the right answer for you:
Optical mechanics
Your age
Avoiding use of contact lenses
MECHANICS:
NO other optical systems for human vision above or below water except our Double-Dome masks automatically change the diopter power depending upon where youre looking. Our dome shape makes water an
active part of the system the diopter strength actually changes, depending upon how much distance of water youre looking through
shown here. Unlike eyeglasses / contacts / flat Rx masks with fixed diopter powers, ours is a range. When youre in the zone you enjoy better vision than you could possibly have above water (superior close-to-far ability). If youre not naturally in the zone then disposable contact lenses put you into the zone.
AGE:
As puberty begins, everybody slowly begins to lose their ability to comfortably maintain their MINIMUM focus distance. Only when we get into our 40s does this become obvious (our arms get too short) and we need:
Reading glasses (if distance is still 20/20)
OR
Bifocals (if weve worn any Rx correction when younger)
Eye doctors call our minimum-distance focus ability ACCOMMODATION
In the 1960s Boeing conducted a big study for the military over 5,000 people were tested for accommodation. At any given age, there is an average minimum focus distance once everyone is corrected to 20/20 for distance. Also closer-than-average and further-than-average. We base our
conversion chart on further-than-average, to be conservative and avoid causing eye strain. There are always exceptions, and weird discoveries. Weve sold dozens of masks to Estonia for 20/20 divers who dont need to wear contact lenses. Even divers in their mid 30s. Their side of the gene pool seems to have the ability to maintain close focus for long periods of time with no eye strain.
AVOIDING EYE STRAIN
When an eye doctor refracts you to determine your vision Rx, you are first auto-refracted by a machine. But most people prefer something a little different literally what our brain has gotten used to and prefer. You look at a Snellen eye chart through a set of trial
diopter lenses, Whats better, A or B? B or C? If B lets you read the 20/20 line, and C lets you
almost read the 20/15 line, the doctor does NOT give you C. But looking through C everything looks more vivid contrast is better. But the Dr. doesnt want to make you overly dependent, which would require a stronger Rx within a few years. Also, a too-strong Rx improves your distance vision but reduces your minimum focus distance (accommodation).
If youre still with me
SIZE:
The 3.5 mask is higher volume vs. the 4.5. Why? To achieve true size / distance / shape, your eyes must stay at the center of a dome. But to reduce the diopter power, the radius of the dome must increase. If you have to wear a mild + power contact for the 4.5 (say +1.00), then the 3.5 would allow your eyes to go naked. But if youve got to wear contacts for the 3.5 anyway, then probably the 4.5 is preferred for its smaller size.
EYE STRAIN?
If you are using the 4.5 naked-eye but experiencing eye strain, then the 3.5 is the way to go.
Whew
for all those that made it through the end
thank you and congratulation. Theres a pop-quiz next week.
Now go get wet this weekend!!!!
