This is why you see physicians checking an athlete's pupils with a penlight following head trauma sustained during sporting events, or when a patient arrives at a hospital emergency department with other possible stroke symptoms. Brain injury or diseaseĪ head injury, stroke or brain tumor can affect how your pupils react to light and cause dilated pupils. Sometimes, this sort of injury can occur during an eye surgery, such as a complicated cataract surgery or a corneal transplant. READ NEXT: Floppy Iris Syndrome Eye injuryĪ serious, penetrating eye injury can damage your iris and cause the pupil to become dilated and irregular in shape. The following prescription and non-prescription medicines can cause your pupils to dilate and affect their ability to react to light:īotox and other medications containing botulinum toxinĪtropine (used for myopia control and other medical purposes) The most common dilated pupil causes include: Medications If one pupil is noticeably larger than the other, you may have something called anisocoria. Your pupils should also dilate symmetrically. However, if your eyes are fully dilated even in a bright environment or if your eyes don't seem to be dilating as they should, it's time to get your eyes checked. It's normal for your pupils to dilate more the darker your surroundings. This is a key spec if you wear glasses.If you've noticed your eyes are unusually dilated (larger) or one eye is dilated more than the other, call an eye doctor! For bright daylight viewing, exit pupil size is less important because almost all binoculars offer exit pupils that exceed 2mm.Įye relief is the distance between an eyepiece and your eye while the whole field of view is visible.
#Picture of pupil size chart full#
A higher number indicates better viewing in low-light situations, and it will be easier to maintain a full image of an object if your hands move or shake.Įxit pupil size is calculated by dividing the diameter of the objective lenses by the magnification number. Simply put, a higher number means brighter images.
(Binoculars with higher quality optics will also have brighter images.) For two pairs of binoculars that otherwise have exactly the same specifications, the pair with larger objective lenses will capture more light, providing a brighter image. The diameter of the objective lenses plays a key role in how much light your binoculars can gather. So, always check that spec whenever you’re doing final comparisons. Magnification and size are the starting point, but optics and features should also factor into your decision.īe aware that binoculars with otherwise identical specs can have dramatically different fields of view (as much as 90 feet wider at 1,000 yards). How do I choose binoculars for specific uses? If you want binoculars for a specific primary purpose such as bird watching, whale watching or astronomy, the basic guidelines below can help narrow down your choices. What additional features are important to consider when buying binoculars? Protective touches like rubber coating, as well as waterproof and fog-proof construction, factor into price, and depending on your intended usage may be well worth the upgrade. Why are binoculars with similar specs pricier than others? It’s what’s inside that counts, and advanced optics are a big reason why the price of similar binoculars can differ by hundreds of dollars. (Below, we’ll go into more detail about binocular specs.) When you understand what these numbers mean and how they affect your viewing, you’ll know if you’re choosing binoculars that will be good for birding, stargazing or using on a moving boat, for example. Objective lens size gives you an understanding of how physically big the binoculars are and how much light they can gather. In 8x42 binoculars, for example, “8” is the magnification power and “42” is the diameter (in millimeters) of the objective lenses (the lenses closest to the object you’re viewing). What do the numbers (specs) on binoculars mean? Model numbers on binoculars essentially tell you their strength ( magnification power) and size ( objective lens diameter).
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