22 Frames, Measuring & Fitting Practice Questions & Answers

1. 1. A four-year-old is being dispensed her first pair of glasses. She is active, and her parents report that the frame is constantly pushed up, pulled at and knocked off. Which temple style suits her best?

   • A.Library temples, whose straight shanks grip the sides of the head and slip off quickly when tugged
   • B.Skull temples on spring hinges, which flex outward so the fit will not need readjusting later
   • C.Skull temples cut 10 mm longer than measured, so the extra length gives the bend behind the ear more hold
   • D.Cable temples, whose flexible curl follows the whole ear and resists the frame being pulled forward✓ Answer

   A comfort cable temple wraps the full circumference of the ear, so the frame cannot be pulled straight off the face; that is why it is the standard choice for infants and toddlers, for safety eyewear and for very active wearers. A library temple has no downward bend at all and relies on skull pressure, and extra temple length only lets the bend sit past the mastoid where it holds nothing.

   Source: ABO-NCLE Basic (NOCE) exam content outline, Ophthalmic Products — Frames: temple typesReport a problem with this question

2. 2. A wearer of -4.50 D lenses has chosen a rimless mounting in which the lenses are drilled and held by screws. Which lens material should be dispensed with that mounting, and why?

   • A.Hard resin (CR-39), because it drills cleanly and is the least costly material suited to rimless work
   • B.Polycarbonate, because its toughness lets a drilled hole carry the mounting without chipping or cracking✓ Answer
   • C.Crown glass, because its hardness keeps a drilled hole from elongating as the mounting screw is tightened
   • D.A 1.74 high-index resin, because the thinner edge it gives lets the mounting hardware seat flush

   A drilled rimless mounting concentrates stress at the hole, so the material must resist crack propagation rather than merely being hard. Polycarbonate is the toughest common ophthalmic material and is the standard choice for drill mounts; glass and the brittle high-index resins star-crack at the hole, and hard resin chips as the screw is torqued.

   Source: ABO-NCLE Basic (NOCE) exam content outline, Ophthalmic Products — Frames: rimless and drill mountingsReport a problem with this question

3. 3. The bend behind the ear on a cellulose acetate (zyl) frame must be increased. What is the correct way to make that adjustment?

   • A.Bend it cold with wide-jaw pliers, since warming acetate draws the laminated color out of the surface
   • B.Heat the temple until the surface begins to glisten, shape it, and release it as soon as the bend is formed
   • C.Warm only the wire core with a hot-air blower so the acetate surrounding that core is never softened
   • D.Warm the temple evenly, form the new bend, and hold that position until the material has cooled✓ Answer

   Cellulose acetate is a thermoplastic: it softens when warmed and keeps whatever shape it holds while it hardens again, so the new position must be held until the temple is cool. Releasing it while still warm lets it creep back, and overheating to the point of glistening blisters the surface, while bending acetate cold simply snaps it.

   Source: System for Ophthalmic Dispensing (Brooks and Borish), frame materials and the adjusting of thermoplastic fronts and templesReport a problem with this question

4. 4. A frame made of epoxy resin, a thermosetting plastic, was adjusted a year ago. It is warmed again today so the pad area can be repositioned. What does the material do on that second heating?

   • A.It keeps the adjustment made a year ago and grows a little softer with every later heating
   • B.It goes on softening and finally stays in whatever position it is bent into while it is warm
   • C.It moves back toward the shape it was molded in, so the new position must be held until cool✓ Answer
   • D.It hardens a little further with each heating, so from now on the frame has to be bent cold

   A thermosetting epoxy frame has shape memory: heat returns it toward the form it was cured in, which is why yesterday's adjustment disappears when the frame is warmed. The adjustment therefore has to be made while the frame is warm and held, or cooled, in the new position, exactly the opposite of the assumption that heat simply softens it permanently.

   Source: System for Ophthalmic Dispensing (Brooks and Borish), thermosetting epoxy frames and their heat memoryReport a problem with this question

5. 5. The eyewire of a polyamide (nylon) sports frame has cracked through at the lower rim. The wearer asks whether the break can be soldered. What should be done?

   • A.Replace the front, because solder joins metals and the heat it needs would distort the polymer✓ Answer
   • B.Fuse the two edges in a frame warmer, since polyamide flows back together with heat the way acetate does
   • C.Solder the break with low-temperature silver solder, then file and polish the joint until it is smooth
   • D.Pin the break with a wire core and cement it, the standard repair for a cracked nylon eyewire

   Soldering is a metal-joining process: the filler alloy wets and bonds to metal, and no solder bonds to a polymer, while the torch temperature is far above the point at which polyamide deforms. A cracked polyamide front is replaced, not repaired, and this is also the material that is normally lens-inserted cold rather than warmed.

   Source: System for Ophthalmic Dispensing (Brooks and Borish), polyamide frames, cold lens insertion and frame repairReport a problem with this question

6. 6. Six weeks after dispensing a Monel frame, a patient returns with itching and a red rash exactly where the pads and end pieces touch the skin. What is the appropriate response?

   • A.Dispense a titanium frame, since the nickel in Monel is the usual cause of this contact reaction✓ Answer
   • B.Refit the same frame with silicone pads, as the reaction comes from pressure and not from the metal
   • C.Have the frame replated in a gold finish, because the rash appears where the plating is still intact
   • D.Loosen the pads and the temples, as the rash follows the skin compression of a tight adjustment

   A rash confined to the points of frame contact is allergic contact dermatitis, and the commonest ophthalmic allergen is the nickel in Monel, released as the plating wears through at the pads and end pieces. Changing the pads leaves the end pieces against the skin, and replating only delays the release, so the patient is moved to titanium or stainless steel.

   Source: ABO-NCLE Basic (NOCE) exam content outline, Ophthalmic Products — Frames: materials, limitations and liabilitiesReport a problem with this question

7. 7. A patient with a narrow, high nasal crest says her heavy plastic frame digs a deep groove into the top of her nose. Which bridge design addresses this?

   • A.A saddle bridge, which follows the crest so that the load is spread along the narrow ridge
   • B.A bridge 4 mm wider than measured, so the front settles lower and the pressure point moves down
   • C.A keyhole bridge, which is relieved over the crest and carries the weight on the sides of the nose✓ Answer
   • D.A metal frame with the pads set close together, which lifts the front clear of the nose altogether

   Weight must be carried on as much tissue as possible, and a narrow high crest offers almost none; the keyhole bridge flares away from the crest and transfers the load to the lateral walls of the nose, where the bearing area is larger. A saddle bridge does the opposite by concentrating the whole weight on the ridge that is already marked.

   Source: ABO-NCLE Basic (NOCE) exam content outline, Ophthalmic Products — Frames: bridge types and their fitting characteristicsReport a problem with this question

8. 8. A frame is marked 52 □ 18 140. In the boxing system, what is its geometric center distance, also called the frame PD?

   • A.35 mm, the eyesize and the bridge added together and then halved
   • B.70 mm, the eyesize added to the distance between the two lens shapes✓ Answer
   • C.52 mm, the eyesize on its own, which is where the lens centers fall
   • D.44 mm, half of the eyesize with the full bridge width added to it

   In the boxing system the first number is the A measurement (eyesize) and the second is the DBL, the shortest distance between the two lens shapes; the geometric center distance is simply A + DBL, here 52 + 18 = 70 mm. The third number, 140, is the temple length and has no part in this calculation.

   Source: ANSI Z80.1, boxing system definitions of the A measurement, the distance between lenses and the geometric center distanceReport a problem with this question

9. 9. In the boxing system, what does the effective diameter of a lens shape describe?

   • A.The longest horizontal measurement of the shape, taken across the rim groove
   • B.Twice the longest distance from the geometric center of the shape out to its edge✓ Answer
   • C.The diagonal of the box, measured from one corner of the shape's box to the other
   • D.The shortest distance between the two lens shapes, measured at their nasal edges

   The effective diameter is twice the longest radius of the shape measured from its geometric center, so it states the smallest round blank that would cover the shape if no decentration were needed. The longest horizontal measurement is the A, and the shortest gap between the shapes is the DBL.

   Source: ANSI Z80.1, boxing system definition of effective diameterReport a problem with this question

10. 10. A lens shape has an effective diameter of 56 mm and each lens must be decentered 4 mm. Allowing 2 mm for edging, what is the minimum blank size?

    • A.66 mm, twice the decentration and the 2 mm allowance added to the effective diameter✓ Answer
    • B.62 mm, the effective diameter plus one decentration and 2 mm for edging
    • C.64 mm, the effective diameter plus twice the decentration, with no allowance
    • D.58 mm, the effective diameter with 2 mm added for the edging allowance

    Minimum blank size is the effective diameter plus twice the decentration plus a small edging allowance, because moving the optical center 4 mm toward the nose leaves the blank 4 mm short on the temporal side and the shortage must be covered on both sides of the center. Here 56 + 8 + 2 gives 66 mm.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), minimum blank size calculationReport a problem with this question

11. 11. A frame has an A measurement of 50 mm and a distance between lenses of 20 mm. The wearer's monocular distance measurements are 32 mm right and 31 mm left. How much must each lens be decentered?

    • A.4 mm in for the right lens and 3 mm in for the left lens
    • B.3.5 mm in for each lens, taken from the 63 mm total measurement
    • C.1 mm in for the left lens only, as the right already matches the frame
    • D.3 mm in for the right lens and 4 mm in for the left lens✓ Answer

    The geometric center distance is 50 + 20 = 70 mm, so each geometric center sits 35 mm from the frame's midline. Decentration per lens is that 35 mm minus the monocular measurement for the same eye, giving 3 mm in on the right and 4 mm in on the left; averaging the two eyes would place both centers wrongly.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), decentration per lens from the geometric center distance and monocular measurementsReport a problem with this question

12. 12. A wearer's distance measurement is 64 mm and the near measurement is 58 mm. What inset is required for each segment?

    • A.1.5 mm per lens, a quarter of the difference, since both eyes converge equally
    • B.2 mm per lens, the customary inset used whenever a near measurement is taken
    • C.6 mm per lens, the whole difference between the distance and near measurements
    • D.3 mm per lens, half of the 6 mm difference between the two measurements✓ Answer

    The difference between the distance and near measurements is the total convergence of both eyes, so it is shared between the two lenses: 64 - 58 = 6 mm total, or 3 mm of inset for each segment. Applying the full difference to each lens would inset the segments twice as far as the eyes actually turn.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), calculation of segment inset from distance and near interpupillary measurementsReport a problem with this question

13. 13. A frame has a B measurement of 40 mm and the segment height ordered is 18 mm. Where does the segment top fall relative to the geometric center of the lens?

    • A.2 mm below the geometric center, which itself sits 20 mm above the lowest point✓ Answer
    • B.18 mm below the geometric center, the segment height measured down from that center
    • C.2 mm above the geometric center, since segment height is measured from the datum line
    • D.22 mm above the lowest point of the lens, the B measurement less the segment height

    Segment height is measured from the lowest point of the lens, and the geometric center lies at half the B measurement, that is 20 mm above that lowest point. An 18 mm segment height therefore puts the segment top 2 mm below the geometric center, a 2 mm drop the laboratory must produce.

    Source: ANSI Z80.1 boxing system geometry, with segment height measured from the lowest point of the finished lensReport a problem with this question

14. 14. Why are monocular distance measurements preferred over one binocular value when spectacle lenses are ordered?

    • A.Halving a binocular value is inaccurate above 4.00 D but is acceptable in weaker powers
    • B.Faces are seldom symmetric, so each optical center is set in front of its own pupil✓ Answer
    • C.Monocular values are needed only when the frame calls for the lenses to be decentered
    • D.A binocular value cannot be read accurately from a corneal reflex pupillometer

    The midline of the face rarely falls halfway between the two pupils, so splitting a binocular value puts one optical center nasal to its pupil and the other temporal, inducing opposite horizontal prism in the two eyes. Measuring each eye from the midline of the bridge places both centers correctly whatever the power.

    Source: ABO-NCLE Basic (NOCE) exam content outline, Dispensing Procedures — fitting, adjusting and measuringReport a problem with this question

15. 15. At what point in the dispensing process are fitting heights and monocular distances taken?

    • A.Before any adjustment, while the frame is still in the shape it left the factory in
    • B.After the frame has been adjusted to the patient and is sitting in the position of wear✓ Answer
    • C.After the lenses have been edged and mounted, so the finished pair is checked on the face
    • D.At any point, as long as the same frame model and eyesize are used for the final order

    Fitting heights and monocular distances describe where the pupil sits behind the lens, and that geometry changes with every millimetre the frame is moved by pantoscopic tilt, pad width or temple bend. The frame is therefore aligned and adjusted first, then measured in the position of wear with the optician's eyes level with the patient's.

    Source: ABO-NCLE Basic (NOCE) exam content outline, Dispensing Procedures — measurements taken in the position of wearReport a problem with this question

16. 16. Where is the top of the intermediate segment of a trifocal customarily placed?

    • A.At the lower edge of the iris, level with the bottom of the limbus
    • B.At the margin of the lower lid, the usual height for a flat-top bifocal
    • C.At the lower edge of the pupil, with the patient looking straight ahead✓ Answer
    • D.At the center of the pupil, so the intermediate covers the whole midrange

    The intermediate zone is used with a small downward gaze, so its top is set at the lower pupil margin in primary gaze, which is higher than a bifocal segment and is the reason a trifocal wearer must be warned about the line crossing the distance field. Placing it at the lid margin would leave the intermediate unusable.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), multifocal segment height selection for trifocalsReport a problem with this question

17. 17. The laboratory has placed the distance optical centers 4 mm below the wearer's pupil centers. Using the customary rule of 1 mm of drop for every 2 degrees of tilt, how much pantoscopic tilt should the frame carry?

    • A.8 degrees, keeping the line of sight square to the back surface of the lens✓ Answer
    • B.4 degrees, one degree of tilt matching each millimetre the center was dropped
    • C.2 degrees, half a degree of tilt for each millimetre the center was dropped
    • D.16 degrees, four degrees of tilt allowed for every millimetre of drop ordered

    The rule pairs each 2 degrees of pantoscopic tilt with 1 mm of optical center drop, so a 4 mm drop corresponds to 8 degrees of tilt. Matching the two keeps the wearer's distance line of sight passing through the optical center at right angles to the lens, which avoids the sphere change and induced cylinder that tilt would otherwise produce.

    Source: ABO-approved National Academy of Opticianry course on vertex distance, effective power and compensated power for tilt and wrap (Martin's tilt rule)Report a problem with this question

18. 18. A patient dispensed an acetate frame three weeks ago says it sits correctly every morning but slides down her nose by mid-afternoon, when the temples also feel loose. What is the most likely explanation?

    • A.Her distance measurement was taken too wide, which lets the front ride lower on her nose
    • B.The lenses were surfaced too thick, so the front grows heavier as the hours of wear go by
    • C.The acetate has relaxed with facial heat and daily wear, so the bends behind the ears have opened✓ Answer
    • D.The pantoscopic tilt is negative, which makes the front slide forward whenever she reads

    A complaint that appears only later in the day points to the frame material rather than to the prescription: cellulose acetate is a thermoplastic and softens slightly at skin temperature, so the earpiece bends open through the day and the front loses its hold. The remedy is to rewarm the temples and re-form the bends, and to check them again at follow-up.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), thermoplastic frame materials and troubleshooting slipping framesReport a problem with this question

19. 19. An optician checks an adjusted frame for temple parallelism on a flat bench. How is that check performed, and what does it show?

    • A.Stand the frame on its temple tips; a tip that lifts shows the two temples are not level
    • B.Lay the frame face down on the lenses; a rocking front shows the lens planes are not coplanar
    • C.Rest the frame on the edge of one temple; a front that tips forward shows negative face form
    • D.Set the frame down on its back with the temples open; a temple that lifts is out of parallel✓ Answer

    Temple parallelism is judged with the frame resting on its back and the temples fully opened, so that the front and both temples should contact the flat surface at the same time; a temple that lifts off is bent in or out relative to its partner. Standing the frame on its tips is the common error, because tip curl and tip angle then hide the fault.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), standard bench alignment sequence and the temple parallelism checkReport a problem with this question

20. 20. A metal frame with adjustable pads rides too low, and the wearer keeps looking over the top of the segment line. Which adjustment raises the front?

    • A.Narrow the pads toward each other, which seats the frame higher on the nasal crest✓ Answer
    • B.Spread the pads apart, giving the bridge more contact so that it seats higher up the nose
    • C.Move the bend behind the ear farther out, letting the front of the frame swing upward
    • D.Increase the pantoscopic tilt at the end pieces so the lower rims lift away from the face

    The nose widens downward, so pads set closer together meet the nose higher up and lift the front, while spreading them lets the frame settle lower. Moving the earpiece bend outward lengthens the effective temple and drops the front, and changing pantoscopic tilt alters the angle of the front rather than its height.

    Source: ABO-NCLE Basic (NOCE) exam content outline, Dispensing Procedures — adjusting adjustable pads and their effect on frame positionReport a problem with this question

21. 21. Looking down on a frame from directly above, an optician sees that one lens plane sits farther forward than the other. Which standard alignment fault is this?

    • A.X-ing, in which the two lenses are twisted in opposite directions about the bridge
    • B.Out-of-coplanar alignment, the fault that only a view from above will reveal✓ Answer
    • C.A skewed front, in which one eyewire has rotated within the plane of the front
    • D.Negative face form, in which the end pieces sit forward of the bridge on the face

    Coplanar alignment asks whether both lens planes lie in the same plane, and only the view from above separates a front that is forward on one side from the other faults. X-ing is a twist seen from the side, where one lens shows pantoscopic and the other retroscopic angle, and a skewed front is a rotation seen from in front.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), standard alignment: coplanar alignment, X-ing and skewed frontsReport a problem with this question

22. 22. A wearer of -9.00 D lenses wants the thinnest possible edges. Which frame characteristics best achieve that?

    • A.A wide distance between lenses, so the extra decentration thins the nasal edge of each lens
    • B.A large rectangular eye shape, so the same edge thickness is spread over a wider lens
    • C.A small, round eye shape in a frame whose geometric center distance is near the wearer's own✓ Answer
    • D.A rimless drill mounting, so that having no rim removes the need to edge the lens thinner

    Edge thickness in a minus lens grows with distance from the optical center, so the two levers are a small, round shape that keeps every edge close to the center and a frame whose geometric center distance is close to the wearer's measurement, which keeps decentration and therefore the thickest edge small. A wide bridge increases decentration and makes the edge thicker.

    Source: System for Ophthalmic Dispensing (Brooks and Borish), frame selection for high minus prescriptions and the effect of decentration on edge thicknessReport a problem with this question

Practice questions based on the American Board of Opticianry Basic Certification exam content outline, standard ophthalmic dispensing references, and the federal rules that govern eyewear (the FDA impact-resistance requirement and the FTC Eyeglass and Contact Lens Rules). ABO and NCLE are marks of the American Board of Opticianry and National Contact Lens Examiners; this site is not affiliated with or endorsed by them. Opticianry is licensed in only some states and the requirements differ — confirm your own state board's practice act and the current exam format before testing. About the ABO exam →