A coating or a faint tint filters some blue wavelength light, and it works in any frame shape you pick.
also: blue light blockers, computer glasses
The basics
What to know about eyeglass frames
What a frame has to do
An eyeglass frame is the mount that holds two corrective lenses a set distance from your eyes and at a set angle to them. Six parts do the whole job: a front carrying the rims, a bridge spanning your nose, an endpiece at each outer corner, a hinge, a temple running back to the ear, and a tip curving over it. None of that corrects vision. Lenses do, and the prescription behind them comes from an eye examination, which also catches pressure and retina problems no frame purchase ever will. Ask your examiner for your pupillary distance, the gap in millimeters between the centers of your pupils, since a lab needs it to place the optical center of each lens directly in front of each eye. A frame can sit perfectly on your face and still cause eyestrain when that number was guessed.
Full rim, half rim, rimless
Rim construction decides how much of the lens edge the frame supports, and support decides what the lens can be made from. Full rim frames hold the lens the whole way around in a bevel, a groove shaped like a letter V that is ground around the lens edge and seats into a matching channel in the rim. Semi rimless frames carry material across the top only and hold the bottom with a nylon cord about 0.5mm thick, strung under tension into a groove on the underside of the lens. Rimless mounts drill holes through each lens and bolt the bridge and endpieces straight to it, so the lens itself becomes the structure. A drilled lens has to be polycarbonate or Trivex, two plastics that resist cracking around a hole, because ordinary CR-39 plastic chips out at a drill point.
Acetate, metal and your skin
Material sets weight, adjustability and what your skin does about it. Cellulose acetate, a plastic pressed from cotton and wood pulp into sheets and then cut and polished, carries color through its full thickness and softens near 175 F. This is how an optician reshapes a temple in a hot air blower. Monel, a nickel and copper alloy, forms and solders easily and costs little, though it releases enough nickel to redden skin on people who react to it. Stainless of grade 316 and titanium release almost none. A titanium frame runs roughly 10 to 15 grams against 25 to 35 grams for a comparable acetate one. You feel that gap after six hours rather than in the first minute.
The three numbers inside the arm
Three numbers stamped inside one temple arm tell you whether a frame can fit before you ever try it, printed as something like 52-18-140. Lens width comes first, measured horizontally across the widest part of one lens, often 40mm to 62mm. Bridge width follows, the gap between the two lenses at their closest point, often 14mm to 24mm. Temple length is third, most often 135, 140, 145 or 150. Double the lens width, add the bridge width, then add roughly 6mm for the rims. You have the frame front to compare against your own face measured temple to temple, which for most adults lands between 125mm and 150mm. Progressive wearers need a fourth figure, lens height, since a lab wants about 28mm to 30mm of vertical depth to stack distance, middle and reading zones without cramming them.
What lightness costs
Every gain here gets billed somewhere else. A rimless mount weighs least and shows least, and it routes every knock into a drilled hole. This makes it the construction most likely to come back for repair. Titanium shrugs off sweat and skin reaction, then refuses ordinary solder, so a snapped temple often ends the frame instead of starting a repair. Acetate reshapes under heat, yet its bridge is molded to one curve. A nose that curve does not match will never be argued into agreement. Large lenses flatter plenty of faces and punish anyone nearsighted, because a minus lens thickens toward its edge and each few millimeters of extra lens width shows as more thickness at the rim. Spring hinges forgive being pulled off one handed, at the cost of a small coil that eventually gives up.
A minute at the counter
Judging a frame takes about a minute at the counter. Fold the temples and stand it on a flat surface. A sound front rests without rocking, and both temples meet it with equal resistance. Count the interlocking barrels at each hinge, since five or seven stay tight where three work loose inside a year. Flex one temple outward past parallel and let go, watching whether it returns to its old line or stays splayed. Sighting along the front from above shows whether both rims sit on the same plane. A rim that is even slightly out will hold your lenses at different heights.
Heat, grit and one handed removal
Heat, grit and one handed removal end more frames than dropping them does. A parked car in summer sun reaches the temperature an optician uses to bend acetate. A frame left on the dash comes back warped with its lens coating lifted. Take glasses off with both hands, because pulling on a single temple twists the front and drops one lens below the other. Wet a lens before any cloth touches it. Book the free adjustment most optical counters offer every six months and have hardened nose pads swapped at the same visit, since those two habits fix most of what people blame on a badly made frame.
Buyer checklist
Before you buy eyeglass frames
Small accessories are easy to buy by appearance, but measurements, materials and hardware decide comfort and durability.
01
Check the actual measurements
Belt length, hat circumference, glove size and lens width are more reliable than one-size labels.
02
Confirm material and lining
Fiber content affects warmth, breathability, stretch, skin feel and cleaning.
03
Inspect moving parts
Buckles, hinges, clasps, elastic and stitched joins usually show wear before the main material does.
04
Plan for storage
Structured hats, leather goods and sunglasses last longer when their shape and surfaces are protected.
Measure your face temple to temple with a ruler, then work out the frame front from the numbers on the arm: double the lens width, add the bridge width, add about 6mm for the rims. Most adults land between 125mm and 150mm, and a front more than 4mm wider than your face braces on nothing and slides all day.
Your pupils should sit in the horizontal center of each lens and a shade above the vertical center. Pupils sitting toward the nose side of the lens mean the bridge is too wide for you, which drags the frame down and puts you looking through the wrong part of the lens.
Smile hard while wearing them and watch the lower rim. Roughly 3mm of clearance above the cheek is enough; less than that and every smile shoves the frame up your nose and leaves skin oil across the bottom of the lens.
Temples should run straight back from the hinge and only start to curve once they pass the top of your ear. A curve beginning early presses into the skull and gives you a headache within an hour or two. A temple 5mm too short lets the front lift off your nose every time you chew.
For progressive or bifocal lenses, measure the vertical height of the lens opening before you commit. Under about 28mm the reading zone gets squeezed into a slot, and you end up tilting your head back to find it.
Low or flat bridges do better with adjustable metal pads, or with a frame sold as a low bridge fit, which raises the bridge and lengthens the pad area so the lens clears your cheek instead of resting on it.
Care
Caring for eyeglass frames
Keep them out of a parked car. Opticians bend acetate with hot air near 175 F. A dashboard in summer sun climbs close enough to pull a frame out of true and lift the coating off a lens.
Remove them with both hands, one on each temple. Taking them off one handed twists the front a fraction each time, and that accumulated twist is the usual reason one lens ends up sitting lower than the other.
Rinse under lukewarm water before any cloth arrives, then dry with clean microfiber. Dust is an abrasive, and a dry wipe drags one grain into a scratch that runs the full width of the lens. Paper towel is wood fiber, which is harder than the coating it is scrubbing.
Tighten hinge and rim screws every few months with a jeweler's screwdriver, or ask an optical counter to do it. Screws back themselves out through ordinary opening and closing, and on a rimless mount a loose screw lets the lens rotate on its bolt until the hole wears oval.
Replace nose pads about once a year. Silicone yellows, hardens and stops flexing, and hard pads are what leave deep red dents and let a frame creep down your nose.
Store them folded in a hard case rather than face down on a surface. Coatings scratch from the front, and a rimless or semi rimless front flexes whenever something presses on it inside a bag.
Questions
Common questions
What do the numbers printed inside my glasses mean?
They give frame size in millimeters, usually as three figures such as 52-18-140. The first is lens width, the second bridge width, the third temple length. Some frames add lens height or total front width alongside. Compare those numbers against a pair that already fits you rather than against your face alone, since the same lens width sits differently on a round lens than a rectangular one.
Can I buy frames online using my prescription?
Yes, provided you have one figure a prescription often omits: pupillary distance, the gap between your pupil centers, usually 54mm to 74mm in adults. Have your examiner write it down. Check the date too, because most prescriptions expire after one or two years and a lab will refuse to glaze an old one.
How do I know if a frame is too wide for my face?
Face a mirror and check the outer edge of each rim: it should line up with the side of your face rather than stand past it. Then turn sideways and confirm the temple runs straight back without bowing outward. A front wider than your head grips nothing at the sides, so it slides down whatever you do to the nose pads.
Are titanium frames worth the extra money?
For all day wear, and for anyone whose skin reacts to nickel, usually yes. Titanium sits around 10 to 15 grams against 25 to 35 for acetate, resists sweat corrosion without plating, and holds its adjustment. Repair is the catch: titanium will not take ordinary solder, so a snapped temple normally means buying a new frame.
Do rimless glasses break more often?
More often, though not dramatically so. Every load travels through the drilled holes, so a knock or a twist tends to crack the lens at its mount instead of bending a rim. Specify polycarbonate or Trivex, which resist cracking around a hole, keep the screws snug, and always remove them with two hands.
Can any frame take a progressive lens?
Most can, but the lens opening needs vertical depth. Labs usually want 28mm to 30mm to stack the distance, middle and reading zones in order. Very shallow rectangles and strongly upswept shapes squeeze the reading area to a sliver. Semi rimless and rimless designs work fine, though the unrimmed lower edge makes the lens edge more visible.
Why do my glasses leave red marks on my nose?
The load is landing on skin instead of being spread across it. Three usual causes: pads set too close together, pads that have hardened and no longer flex, or a frame heavy enough to dig in on its own. Widening the pads, replacing them with soft silicone, or moving to a lighter material each cures a different one.
Are drugstore reading glasses as good as prescription ones?
For occasional close work with roughly equal vision in both eyes, they do the job for a fraction of the price. Both lenses carry identical power, usually +1.00 to +3.50 in 0.25 steps, with the optical centers fixed near 62mm apart. Unequal eyes or any astigmatism turn that fixed setup into a headache after twenty minutes.
