21 Frames, Measuring & Fitting Practice Questions & Answers

1. 1. Which temple style runs straight for its entire length, with no downward bend behind the ear, so the eyewear is easy to put on and take off but is the least secure on the head?

   • A.A library (paddle) temple✓ Answer
   • B.A skull temple
   • C.A comfort cable temple
   • D.A riding bow temple

   A library or paddle temple has no bend at all; it is held only by light friction against the sides of the head, which makes the eyewear quick to remove but easy to dislodge when the wearer bends forward. A skull temple bends down and follows the contour of the skull behind the ear, a comfort cable wraps completely around the ear, and a riding bow curves down to about earlobe level, so all three grip far better.

   Source: American Board of Opticianry exam content outline, ophthalmic products (frames); System for Ophthalmic DispensingReport a problem with this question

2. 2. A patient selects a three-piece rimless mounting in which each lens is drilled and held to the bridge and endpieces by screws. Which consideration follows directly from that mounting choice?

   • A.The lens must be edged with a V-bevel so that it seats in the mounting's eyewire groove
   • B.Any lens material is acceptable, because the screws rather than the lens carry all of the mounting stress
   • C.An impact-resistant material such as polycarbonate, with adequate centre thickness, is required because the drill holes concentrate stress in the lens✓ Answer
   • D.A brittle material such as glass is preferred, because it resists chipping around the drill holes

   In a drill mount the lens itself is the structural member: the holes create stress risers, and any impact or over-tightened screw can start a crack that runs from the hole. Impact-resistant materials tolerate that stress far better than brittle ones, and a rimless lens also needs enough centre thickness for the hole to be drilled safely; a V-bevel belongs to a full-rim frame, which has a grooved eyewire.

   Source: 21 CFR 801.410 (impact-resistant lenses in eyeglasses); System for Ophthalmic Dispensing, rimless mountingsReport a problem with this question

3. 3. The temples of a cellulose acetate (zyl) frame must be spread slightly wider. How should the frame be prepared before the adjustment?

   • A.Hold it briefly in the open flame of a torch until the surface softens
   • B.Warm it evenly in a warm-air frame heater until it is pliable, then bend it slowly✓ Answer
   • C.Soak it in ice water, which makes the plastic temporarily flexible
   • D.Adjust it cold at the endpieces, exactly as a metal frame is adjusted

   Cellulose acetate is a thermoplastic that becomes workable only when heated, and a warm-air heater raises the temperature gradually and evenly so the material bends without stress marks. An open flame heats one spot far above the working range and will scorch, bubble or craze the plastic and can damage lens coatings, while cold bending of acetate simply snaps it.

   Source: American Board of Opticianry exam content outline, dispensing procedures (frame materials and handling); System for Ophthalmic DispensingReport a problem with this question

4. 4. An epoxy resin frame is heated, adjusted and cooled successfully, but the next time it is warmed for a small change it springs back toward the shape it had when new. Which material property explains this behaviour?

   • A.Nickel fatigue in the core wire, which unwinds when warm
   • B.Water absorption, which swells the material and reverses the adjustment
   • C.Work hardening of the hinge barrels, which pulls the front back into shape
   • D.Thermal (shape) memory: it must be heated to adjust, holds the new shape on cooling, and returns to its moulded shape when reheated✓ Answer

   Epoxy resin frames are moulded under heat and retain a memory of that original shape, so heat is what makes them adjustable and heat is also what erases the adjustment. The practical consequence at the bench is that these frames cannot be cold-bent at all and must be reheated for every change, with the technician expecting some return toward the moulded form.

   Source: American Board of Opticianry exam content outline, ophthalmic products (frame materials); System for Ophthalmic DispensingReport a problem with this question

5. 5. A nylon (polyamide) sports frame arrives with a fractured endpiece. Why is soldering not an option for this repair?

   • A.Soldering is possible only after the nylon is chemically primed and then annealed
   • B.Solder melts at a lower temperature than nylon, so the joint would never set
   • C.Nylon is a thermoplastic, not a metal, so there is no metallic surface for solder to wet and bond to; the front must be replaced✓ Answer
   • D.Solder would corrode on contact with nylon within a few weeks

   Soldering works by melting a filler metal that alloys with the metal surfaces being joined, so it is meaningless on a polymer; the heat required would simply melt and deform the nylon. Nylon frames are also notoriously difficult to adjust because they hold their moulded shape, which is exactly why they suit high-impact sports and wrap styles but limit repair options to component replacement.

   Source: American Board of Opticianry exam content outline, ophthalmic products (frame materials); System for Ophthalmic Dispensing, frame repairReport a problem with this question

6. 6. A patient returns with a red, itchy rash on the bridge of the nose and at the temple tips, exactly where a common alloy metal frame touches the skin. What is the most likely cause and the most appropriate substitution?

   • A.Nickel in the alloy causing allergic contact dermatitis; substitute a titanium, beta-titanium or plastic frame✓ Answer
   • B.Ultraviolet exposure through the lenses; substitute a frame with larger lenses
   • C.Perspiration salts etching the plating; substitute a frame with silicone nose pads only
   • D.Excess pantoscopic tilt pressing the frame into the skin; substitute a lighter lens material

   Nickel is present in most inexpensive frame alloys and is the leading cause of contact dermatitis in eyewear, producing a rash confined to the skin the metal touches. Because the reaction is immunological rather than mechanical, plating wears through and the rash returns, so the durable fix is a nickel-free material such as titanium, beta-titanium or plastic.

   Source: American Board of Opticianry exam content outline, ophthalmic products (frame materials and liabilities); System for Ophthalmic DispensingReport a problem with this question

7. 7. A patient with a narrow, sensitive nasal crest is being fitted with fairly heavy eyewear in a plastic frame that has no adjustable pad arms. Which non-adjustable bridge design best relieves pressure on the crest by transferring weight to the sides of the nose?

   • A.A saddle bridge
   • B.A bridge with adjustable pad arms
   • C.A modified saddle bridge
   • D.A keyhole bridge✓ Answer

   A keyhole bridge is shaped so that it arches over the crest and bears only on the lateral walls of the nose, which is why it is chosen for a narrow or tender crest and for heavier eyewear. A saddle bridge deliberately spreads weight across the crest as well as the sides, a modified saddle still contacts the crest, and pad arms are excluded by the stem because this frame has none.

   Source: American Board of Opticianry exam content outline, ophthalmic products (frames, bridge types); System for Ophthalmic DispensingReport a problem with this question

8. 8. A frame is marked 52-18-140. Using the boxing system, what is its geometric centre distance, also called the frame PD or distance between centres?

   • A.70 mm✓ Answer
   • B.52 mm
   • C.86 mm
   • D.34 mm

   In the boxing system the geometric centre distance equals the A measurement plus the DBL, because each geometric centre sits at the middle of its own box and the two boxes are separated by the DBL: 52 + 18 = 70 mm. The 140 is the temple length and plays no part in the calculation, and comparing this 70 mm with the wearer's distance PD is what tells the dispenser how much the lenses must be decentred.

   Source: ANSI Z80.5, Requirements for Ophthalmic Frames (boxing system definitions)Report a problem with this question

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

   • A.Twice the longest radius from the geometric centre, that is, the diameter of the smallest circle that will completely cover the shape✓ Answer
   • B.The vertical height of the box, measured between the horizontal tangents
   • C.The horizontal width of the box, measured between the vertical tangents
   • D.The distance from the geometric centre of one lens to the geometric centre of the other

   The effective diameter is twice the longest radius drawn from the geometric centre to the edge of the shape, so it is exactly the diameter of the smallest round blank that could still cover the whole pattern if no decentration were needed. That is why ED, not the A measurement, is the starting figure for minimum blank size; the horizontal box width is A, the vertical box height is B, and the centre-to-centre distance is the geometric centre distance.

   Source: ANSI Z80.5, Requirements for Ophthalmic Frames (boxing system definitions)Report a problem with this question

10. 10. A patient's new prescription is -8.00 D in each eye and the distance PD is 62 mm. Which frame characteristic will do the most to limit edge thickness and overall weight?

    • A.A wide DBL, since the bridge width has no effect on the lens itself
    • B.Adjustable pad arms, because pads carry the weight and therefore reduce edge thickness
    • C.A small eyesize whose frame PD is close to the patient's distance PD, so that decentration is minimal✓ Answer
    • D.A large eyesize, because a bigger lens spreads the power over more surface

    In a minus lens the thickness grows toward the edge, so both a larger eyesize and any decentration push more thick material into the finished lens; keeping the frame PD (A plus DBL) close to the wearer's PD means the optical centres sit near the geometric centres and almost no extra material is carried out to the edge. A wide DBL is not neutral either, because DBL is part of the frame PD and therefore drives decentration, and pad arms only affect how the finished weight is supported.

    Source: American Board of Opticianry exam content outline, dispensing procedures (lens parameters and frame selection); System for Ophthalmic DispensingReport a problem with this question

11. 11. A frame has an A measurement of 52 mm and a DBL of 16 mm. The patient's monocular distance PDs are 32 mm right and 34 mm left. What decentration is required?

    • A.2 mm in for each lens
    • B.1 mm in for each lens
    • C.2 mm out for the right lens and 2 mm in for the left lens
    • D.2 mm in for the right lens and none for the left lens✓ Answer

    Decentration is worked out one eye at a time whenever the monocular PDs differ: the frame PD is 52 + 16 = 68 mm, so each geometric centre sits 34 mm from the frame's midline. The right eye needs its optical centre 32 mm from the midline, a 2 mm inward move, while the left eye's 34 mm already coincides with the geometric centre, so no decentration is needed there.

    Source: American Board of Opticianry exam content outline, dispensing procedures (centration and distance between centres); System for Ophthalmic DispensingReport a problem with this question

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

    • A.62 mm
    • B.66 mm✓ Answer
    • C.64 mm
    • D.70 mm

    Minimum blank size is the effective diameter plus twice the decentration plus the working allowance, because moving the optical centre away from the blank's centre by 4 mm means the far side of the shape now needs an extra 4 mm of glass on that side as well: 56 + (2 x 4) + 2 = 66 mm. Ordering a blank smaller than this is the standard reason a lens will not cut out.

    Source: American Board of Opticianry exam content outline, dispensing procedures (blank size and centration); System for Ophthalmic DispensingReport a problem with this question

13. 13. A patient's distance PD is 64 mm and the near PD is 60 mm. What segment inset is required for each lens of a pair of bifocals?

    • A.4 mm
    • B.1 mm
    • C.2 mm✓ Answer
    • D.8 mm

    The eyes converge for near vision, so the near PD is smaller than the distance PD and the difference is shared between the two eyes: (64 - 60) / 2 = 2 mm of inset per lens. Inset is applied in addition to any distance decentration, and its purpose is to place the segment where the visual axes actually cross the lens at reading distance.

    Source: American Board of Opticianry exam content outline, dispensing procedures (multifocal positioning); System for Ophthalmic DispensingReport a problem with this question

14. 14. A frame has a B measurement of 40 mm and the ordered segment height is 16 mm. Where does the top of the segment sit relative to the datum line?

    • A.16 mm below the datum line
    • B.4 mm below the datum line✓ Answer
    • C.24 mm below the datum line
    • D.4 mm above the datum line

    The datum line runs horizontally through the vertical midpoint of the box, so it sits at B divided by 2, here 20 mm above the lowest point of the lens opening. A segment height of 16 mm is measured from that same lowest point, so the segment top is 20 - 16 = 4 mm below the datum line, which the laboratory records as a 4 mm segment drop.

    Source: ANSI Z80.5, Requirements for Ophthalmic Frames (boxing system, datum line); System for Ophthalmic DispensingReport a problem with this question

15. 15. Why is a monocular PD preferred over a single binocular PD when ordering spectacle lenses?

    • A.Because monocular values remove the need to measure segment heights
    • B.Because most faces are not perfectly symmetrical about the midline, so each optical centre must be placed relative to the centre of the bridge individually✓ Answer
    • C.Because the monocular PD automatically compensates for pantoscopic tilt
    • D.Because a binocular PD cannot be measured accurately at any working distance

    Facial asymmetry is the rule rather than the exception, so splitting a binocular PD in half can place one optical centre several millimetres off the visual axis and induce unwanted prism by Prentice's rule. Measuring each eye from the centre of the bridge places both optical centres correctly, and the two monocular values still add up to the binocular PD as a useful check.

    Source: American Board of Opticianry exam content outline, dispensing procedures (measuring the wearer); System for Ophthalmic DispensingReport a problem with this question

16. 16. A patient has chosen a frame. At what point in the process should the PD, optical centre heights and segment heights be taken?

    • A.Only after the lenses have been edged and mounted in the frame
    • B.While the patient holds the frame in one hand at reading distance
    • C.Before the patient tries the frame on, using the dimensions marked on the frame
    • D.After the frame has been pre-adjusted to the patient's face✓ Answer

    Heights and centres are referenced to where the lens actually sits in front of the eye, so any later change in vertex, pantoscopic tilt or how high the frame rides invalidates a measurement taken beforehand. The standard sequence is to align the front first, so it is level and sits just under the brow with the pads flush, then set the temples, and only then measure with the patient in natural head posture and the dispenser at eye level.

    Source: American Board of Opticianry exam content outline, dispensing procedures (fitting, adjusting and measuring); System for Ophthalmic DispensingReport a problem with this question

17. 17. Where is the top line of a flat-top trifocal segment normally positioned when fitting height is taken on a pre-adjusted frame?

    • A.At the lower lid margin
    • B.At the lower pupil margin✓ Answer
    • C.At the datum line of the frame
    • D.At the centre of the pupil

    A trifocal is set higher than a bifocal because the intermediate zone must be available with only a small downward gaze, so its top line is placed at the bottom edge of the pupil. A bifocal top is conventionally placed at the lower lid margin, and the fitting cross of a progressive is placed at the pupil centre; the datum line is a frame reference, not an anatomical one.

    Source: American Board of Opticianry exam content outline, dispensing procedures (proper positioning of multifocals); System for Ophthalmic DispensingReport a problem with this question

18. 18. A single vision frame is fitted with 12 degrees of pantoscopic tilt. Applying the customary rule that the optical centre is lowered 1 mm for every 2 degrees of tilt, how far below the pupil centre should the optical centre be placed?

    • A.6 mm✓ Answer
    • B.12 mm
    • C.2 mm
    • D.3 mm

    Twelve degrees divided by two degrees per millimetre gives a 6 mm drop. The rule exists because tilting the front rotates the optical axis away from the eye's centre of rotation; lowering the centre re-aims that axis so the patient still looks through the lens along its axis, which prevents the unwanted sphere, cylinder and vertical prism that uncompensated tilt induces, and the error grows with lens power.

    Source: American Board of Opticianry exam content outline, dispensing procedures (optical effects of pantoscopic tilt); System for Ophthalmic DispensingReport a problem with this question

19. 19. A patient wearing +6.00 D lenses reports that distance vision is clear first thing in the morning but blurs as the day goes on, and the frame is found to have slipped well down the nose. What is the optical explanation?

    • A.Increasing the vertex distance reduces the effective plus power to zero, so no correction reaches the eye
    • B.Increasing the vertex distance increases the effective plus power at the eye, so the correction becomes too strong for distance✓ Answer
    • C.Vertex distance affects only cylinder axis, so the axis has rotated
    • D.Vertex distance has no optical effect below 8.00 D, so the cause must be a wrong prescription

    Effective power changes with vertex distance according to the relationship in which the new power equals the original power divided by one minus the distance in metres times the power, and for a plus lens moving away from the eye the effective plus increases. The patient is therefore over-plussed for distance as the frame slides, and the correct response is to re-adjust the frame back to the fitted vertex, not to change the prescription.

    Source: American Board of Opticianry exam content outline, dispensing procedures (vertex distance and effective power); System for Ophthalmic DispensingReport a problem with this question

20. 20. During standard alignment the frame front is laid face down on a flat surface and one eyewire rocks instead of resting flat while the other stays down. What does this finding indicate, and what does the patient typically report if it is not corrected?

    • A.The nose pads are set too far apart; the patient reports the frame riding too high
    • B.There is excessive pantoscopic tilt; the patient reports that the lenses touch the eyebrows
    • C.The temples are of unequal length; the patient reports pressure over one mastoid
    • D.The front is X-ed, or propellered, with one eyewire rotated relative to the other; the patient reports that one lens sits closer to the face or cheek than the other✓ Answer

    Standard alignment is checked before the frame ever touches a face, and the four-point touch test asks that both eyewire tops and both temple ends contact a flat surface at the same time. A rocking eyewire means one side of the front is twisted about the horizontal axis, so once worn that lens sits at a different distance from the face, changing vertex and tilt on that eye and producing an obvious cosmetic and optical asymmetry.

    Source: American Board of Opticianry exam content outline, dispensing procedures (frame alignment); System for Ophthalmic Dispensing, standard alignmentReport a problem with this question

21. 21. A metal frame with adjustable pad arms sits noticeably too low on the wearer, so the pupils fall above the midline of the lenses. Which adjustment raises the frame?

    • A.Move the nose pads farther apart
    • B.Increase the depth of the bend behind each ear
    • C.Shorten the temples at the endpieces
    • D.Move the nose pads closer together✓ Answer

    Because the nose is narrower toward the top, bringing the pads closer together makes them contact higher on the nasal walls and the whole frame rides up; spreading them apart lets the frame settle lower. On a pad frame, height is controlled at the pads rather than at the temples, whereas a plastic frame with a fixed bridge can only be raised or lowered by altering the temples.

    Source: American Board of Opticianry exam content outline, dispensing procedures (adjustment procedures); System for Ophthalmic DispensingReport 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 →