Ordering and verification of spectacle frame lens and glass
- 1. ORDERING AND VERIFICATION OF SPECTACLE FRAME NAOBA MUTUM F.Y. M.OPTOM
- 2. INTRODUCTION Spectacle frames are an integral part of vision correction, serving both functional and aesthetic roles. Beyond simply holding lenses in place, frames ensure that corrective lenses align properly with the patient's line of sight, enhancing visual acuity and providing comfort throughout daily wear. They also represent a personal style choice, which makes their selection a blend of science and art.
- 3. IMPORTANCE OF ACCURATE FRAME ORDERING AND VERIFICATION • When it comes to vision correction, precision is crucial. An ill-fitting frame or incorrect alignment of lenses can lead to issues such as: • Eye strain • Distorted vision • Physical discomfort (e.g., irritation around the nose, temples, or ears) • The process of ordering spectacle frames includes careful selection, accurate measurement, and rigorous verification. Optometrists and optical professionals must consider various aspects, such as the patient's prescription, face shape, lifestyle needs, and personal preferences, to make the best frame recommendation.
- 4. REQUIREMENTS IN ORDERING A SPECTACLE FRAME The requirements for ordering a spectacle frame involve several key steps that ensure the frame is not only visually appealing but also functionally effective for vision correction and comfortable for long-term wear.
- 5. REQUIREMENTS 1. Patient Consultation and Lifestyle Assessment • Objective: Understand the patient’s needs, preferences, and lifestyle, which will influence frame selection. • Key Questions to Consider: • Visual Needs: Is the patient near-sighted, far-sighted, or using progressive lenses? • Daily Activities: Does the patient need frames suitable for sports, digital work, or fashion? • Style Preferences: What are the patient’s preferences for frame style, color, and material? • Comfort Requirements: Does the patient have any sensitivity to certain materials (e.g., metal allergies)?
- 6. 2. Frame Type and Material Selection Types of Frames: • Full-Rim: Encircles the entire lens, offering protection and stability. • Half-Rim or Semi-Rimless: Lightweight, partially encases the lens for a more subtle look. • Rimless: Minimalistic with no frame around the lenses, appealing to those seeking a lightweight, barely-there look. Material Options: • Plastic (e.g., Acetate): Lightweight, colorful, and comfortable. Good for patients with sensitive skin. • Metal (e.g., Titanium, Stainless Steel): Durable and flexible, ideal for a sleek appearance. Titanium is hypoallergenic, suitable for sensitive patients.
- 7. • Combination Frames: Blend plastic and metal for versatility in appearance and durability. • Memory Metal (e.g., Flexon): Shape-retentive, ideal for active patients or children, as the frames can twist and return to original shape.
- 8. 3. Precise Frame Measurements Pupillary Distance (PD): • The distance between the centers of the pupils, crucial for aligning lenses correctly to avoid strain. • Measurement Tools: PD ruler, digital measuring devices, or specialized apps. Lens Width (Eye Size): • Refers to the horizontal width of each lens. • Ensures the lens size fits the patient’s face without appearing too large or small.
- 9. Bridge Width: • The distance between the two lenses that sits over the nose. • Important for comfort and stability, as a too-narrow or too-wide bridge will affect fit and alignment. Temple Length: • Refers to the length of the “arms” of the frame that sit over the ears. • Proper temple length ensures the frame rests comfortably behind the ears and maintains stability.
- 10. 4. Frame Alignment and Fit Nose Pads and Bridge Fit: • For frames with adjustable nose pads, the bridge should rest comfortably on the nose, distributing the weight evenly. • Check the fit on the nose, ensuring it does not pinch or slip. Temple Arms: • The arms should wrap around the ears without excessive pressure. • Adjust temple tips as needed to secure the frame without discomfort.
- 11. Tilt and Wrap Angle: • Proper angle and tilt prevent glare and ensure optimal alignment of lenses with the eyes. • Adjustments can help the frame sit flush on the face without affecting the prescription.
- 12. 5. Lens Prescription Requirements Prescription Type: • Based on the patient's needs: single vision, bifocal, progressive, or specialized lenses (e.g., for computer use). Lens Material: • Choose between materials such as polycarbonate (impact-resistant), high- index (thinner), or Trivex (lightweight and impact-resistant).
- 13. Additional Coatings and Treatments: • Anti-Reflective Coating: Reduces glare, beneficial for screen use and night driving. • UV Protection: Shields eyes from harmful UV rays, essential for outdoor wear. • Blue Light Filter: Filters harmful blue light, reducing strain from prolonged screen exposure.
- 14. 6. Supplier Selection and Order Placement Choosing a Reliable Supplier: • Verify that the supplier offers high-quality frames with a warranty or return policy. • Look for suppliers with positive reviews and reliable support for handling adjustments, returns, or repairs. Submitting the Order: • Include all relevant details such as frame measurements, prescription requirements, and any specific preferences. • Double-check the order for accuracy in measurements and specifications to reduce errors and ensure satisfaction.
- 15. 7. Verification of Frame and Lens Specifications Quality Check: • Inspect the frame for any manufacturing defects, scratches, or alignment issues. • Verify lens quality, ensuring no blemishes, scratches, or coating issues. Measurement Verification: • Confirm all measurements align with the order, including PD, bridge width, and temple length. • Lens prescription should match the patient’s needs precisely, verified with tools like a lensometer.
- 16. Fit and Comfort Testing: • Perform a final fitting with the patient to ensure the frame feels comfortable, does not pinch or slip, and aligns with the line of sight. • Make any minor adjustments to nose pads or temple length to enhance comfort.
- 17. 8. Final Patient Fitting and Adjustments Patient Feedback: Ask the patient to assess comfort, fit, and visual clarity. Minor Adjustments: Fine-tune the frame alignment, nose pad placement, and temple adjustments based on patient feedback. Instructions for Care: Provide guidance on how to clean and maintain the frame and lenses, including avoiding harsh chemicals and proper storage. This step completes the order, ensuring the patient leaves with a frame that meets all requirements for fit, comfort, and vision correction.
- 20. OBTAINING PRESCRIPTION INFORMATION FOR MULTIFOCAL LENSES • Distance powers for multifocal lenses are measured in the same way that powers for single vision lenses are measured. • A multifocal differs from a single vision lens because it has additional plus power for viewing at near. • This near addition is plus power that is added to the power of the distance prescription. • To measure the distance power of multifocal lenses, place the glasses in the lensometer in exactly the same way as would be done for single vision lenses. • The distance power is measured in the manner described for single vision lenses. To measure the power of single vision lenses or the distance power of segmented multifocals, the glasses are placed in the lensometer as shown. This measures the prescription in the correct manner. The power being measured is known as the back vertex power.
- 21. • To measure the add (near addition) power, turn the glasses around backward in the lensometer so that the front of the lenses are against the lensometer aperture. • Now remeasure the distance power. • When measured this way, the power is called front vertex power. When measured in the normal way, from the back, the power measured is called back vertex power. • It will be noted that the lensometer- measured cylinder axis for the front vertex power is the mirror image of the axis for the back vertex power. To measure multifocal lens power, the glasses must be turned around backward in the lensometer and distance power measured again, this time as front vertex power. Note that the power is measured as far above the optical center of the lens as the near verification point in the multifocal segment is below the distance optical center of the lens.
- 22. • In other words, a lens having a 30-degree back-vertex-power axis will manifest an axis of 150 degrees when turned around. • When remeasuring the distance power as front vertex power, do not measure the lens at the OC. • Instead measure the distance front vertex power at a location above the OC. That point should be as far above the OC and inward as the point where the add power will be measured is below the OC and inward. • This technique ensures that any power variations caused by lens aberrations or lens thicknesses will be the same in distance and near power measurements.
- 23. • Next measure the power of the lens through the near segment. The difference between distance and near power readings is the power of the near addition.
- 24. Identifying Multifocal Segment Style and Size • When ordering a replacement pair or second pair of glasses from an existing pair, it is important to identify the multifocal type. • Multifocals are identified by segment style. • The most commonly used visible segment styles are flat-top (sometimes called “D” segs), curve-top, and round segs.
- 25. Measuring Segment Size • Once segment style is identified, segment size must be found. • Segment size is measured across the widest portion of the segment—not the top of the segment. • Trifocal sizes are identified by two numbers. • The first number is the vertical size of the trifocal section in millimeters. The second number is the widest horizontal measure of the multifocal segment The width of a bifocal or trifocal segment is measured at the widest part of the segment.
- 26. • The width of a round segment is determined by its diameter. • This remains true, even if most of the segment has been edged away, making a physical measurement impossible. In such cases, the size of the segment is determined by estimating the location of segment borders
- 27. Measuring Segment Height • To measure and duplicate the segment height of an existing prescription, first the old segment height for the existing prescription is measured. • If the frame will remain the same, so will the old segment height.
- 28. Identifying Base Curve • Changing the base curve may affect the way objects appear to the wearer. Straight lines may seem curved, objects may seem larger or smaller than they actually. • To measure a preexisting lens curve for accurate duplication or verification, a lens measure (some times referred to as a lens clock), is used. A lens measure may use direct plus and minus scales as shown here, or an outer minus scale for concave sur faces and an inner plus scale for convex surfaces
- 29. Identifying Lens Material • It is important that an attempt to identify the lens mate rial in the existing prescription be made. • It is simple enough to tell the difference between glass and plastic. • Lightly tapping the lens with a metallic object, such as a ring, will result in a characteristically different sound and feel. • Plastic materials are not as easy to differentiate one from another.
- 30. • Plastic materials are not as easy to differentiate one from another. • When a polycarbonate lens is dropped on a surface with its backside down, some compare the sound to that of a poker chip. But a lens already in a frame will not be removed just to perform this procedure! • Polycarbonate and higher index plastics are often made thinner than regular plastic lenses of equal powers. Lens center thickness is measured with lens calipers. In preparation for measuring lens thickness, the optical center of the lens is spotted using the lensometer. Then the center thickness of the lens may be measured with a pair of calipers as shown in this photo
- 31. • Center thickness can be used to help determine the type of material from which the lens is made. • Minus lenses have their thinnest point at the optical center. *Warning: It is not possible to identify lens material on the basis of lens thickness! Glass lenses purchased outside the United States do not have the same impact resistance requirements and may be exceptionally thin. It is important to note that a thick lens is not a safety lens unless it has been marked on the surface as a safety lens with the manufacturer’s identifying mark.
- 32. What to Keep in Mind When Ordering One Lens Instead of Two? • Occasionally, it becomes necessary to order one lens instead of two. • This occurs when only one lens power changes from the previous examination or when one lens is damaged or broken. • When a single vision lens is being replaced, the major reference point (MRP) height of the remaining lens in the prescription should be measured. • The MRP height of the new lens should match that of the remaining partner lens.
- 33. • When only one lens is replaced in multifocal lenses, the lens should be ordered so that the two segment heights match. • It is also important that the MRP height of the lens that is not being replaced be measured. • This is because many optical laboratories do not place the MRP on the 180- degree midline for multifocals with a segment that is set high in the frame. • This means that in order for the new lens to match the old lens, both MRP and seg heights should be specified.
- 34. • When a laboratory receives no specific instructions for MRP height, the MRP is normally placed at midlevel (on the horizontal midline). • However, when the seg height is specified at a level that approaches or goes above this horizontal midline, many laboratories place the MRP 3 mm above the seg line. • Therefore, when replacing only one lens of a multifocal prescription, the dispenser should either send the old glasses to the laboratory, or tell the laboratory the segment height and the MRP height for the new lens. • Failure to specify MRP height when ordering one lens only may result in unwanted vertical prism in the finished pair of glasses.
- 35. • Therefore, when replacing only one lens of a multifocal prescription, the dispenser should either send the old glasses to the laboratory, or tell the laboratory the segment height and the MRP height for the new lens. • Failure to specify MRP height when ordering one lens only may result in unwanted vertical prism in the finished pair of glasses
- 36. ORDERING LENSES ONLY Sometimes a wearer wants new lenses for an old frame, but does not have a spare pair of glasses. When the order cannot immediately be done in-house and the wearer must keep the frame, the order to the laboratory is for “lenses only.” The danger in ordering “lenses only” and just specifying frame name and size is that the lens can easily be too large or too small. The error is only evident when the wearer returns, and the dispenser attempts to insert the off-sized lens pair into the old frame.
- 37. In this situation the method of choice is to remove the lenses from the frame and use a remote frame shape tracer that is connected to the computer in the optical laboratory. With a frame tracer, a stylus can trace the inside bevel of the eyewire. Both shape and size are electronically sent directly to the laboratory. A frame tracer uses a stylus to trace the inside bevel of the frame, recording the shape. This shape is then sent to the optical laboratory and downloaded into their lens edger so that the lenses may be edged to exactly fit the measured frame.
- 38. Ordering “Lenses Only” for a Frame of an Unknown Shape If the frame name or lens shape is unknown, or if the pattern is not readily available at the laboratory, then it will be necessary to trace the lens and measure for C size. The procedures for shape tracing and C-size measurements are: 1. Using the lensometer, spot the distance OCs and the 180-degree line. 2. Remove the right lens from the frame without disturbing the three lensometer dots. 3. Use a form, and keeping the 180-degree line horizontal, center the lens as if making a pattern.
- 39. 4. In practice one of these forms may not be available. If not, draw an “x” and “y” axis on graph paper and record the necessary information. Graph paper will work just as well. Here is an example of one type of form that may be used to trace a lens of unknown shape for a “lenses only” order Center the lens so that it is exactly in the middle of the grid both horizontally and vertically. The three lensometer dots must be exactly horizontal but do not have to be exactly on the line; nor does the center lensometer dot need to be at the origin of the x and y axes
- 40. 5. Trace the lens onto the graph paper, using a sharp pencil. Keep the pencil perpendicular to the paper the whole time the lens is being traced. 6. Measure the actual lens A and B dimensions (not the dimensions of the lens tracing) and record these dimensions. 7. An easy, more accurate alternative to a simple ruler is to use a Box-O Graph to measure the lens . The tracing is only used for shape, not dimensions.
- 41. 8. Measure the DBL of the frame. Do not rely on the bridge size marked on the frame. 9. Using a circumference gauge, measure the circumference of the lens and record. 10.Record whether the lens is for a plastic, metal, nylon cord, or other type of frame. 11. Indicate whether the lens is a right or a left lens. Mark “N” for nasal on the nasal side of the tracing. 12. Replace the lens in the frame and clean up the lenses.
- 42. Ordering “Lenses Only” by C-Size Sometimes there is not a frame tracer available. Without a tracer, it is still possible for the wearer to keep the frames and still order the lenses. When the shape of the frame is well known, the laboratory may have a factory pattern or an electronically stored shape on hand. However, there may be a variation in size. Simply ordering the size stamped on the frame may not be good enough.
- 43. In this case, the lens may be removed and a circumference gauge used to find the C size* or circumference of the lens. When lens circumference is known, lens size can be reproduced with more accuracy. A circumference gauge is used to find the circumference of an edged lens. To measure the circumference of a lens, place the lens in the gauge front-side up. Close the tape around the lens and read the circumference directly from the tape
- 44. Verifying Lens Powers and Determining Error Tolerances • Lens power is verified using the lensometer, and in the United States tolerances for ophthalmic lens prescriptions are set by the American National Standards Institute. • The American National Standards Institute, abbreviated ANSI, is a nongovernmental agency made up of representative segments of industry. • The specific standard for prescription lenses is identified by the number Z80.1 and is titled “American National Standard for Ophthalmics- Prescription Ophthalmic Lenses—Recommendations.”
- 45. • Each aspect of a spectacle lens prescription has a small range of tolerance within which that particular variable of the eyeglass prescription can fall and still be considered acceptable. • It must be recognized that it is a difficult task to fabricate a prescription that meets ANSI standards in all variables.
- 46. Tolerance for Error in “Sphere” Power and Cylinder Axis • After focusing the eyepiece, the lens with the strongest power in the 90 degree meridian is placed in the lensometer. • If the lenses have similar powers and there is also prescribed prism in the prescription, then choose the lens with the most vertical prism and start with that lens. • The power wheel of the lensometer is preset for the expected sphere power, and the axis wheel is preset for the expected axis. • If either of these two values is incorrect, the lensometer’s illuminated target will blur.
- 47. • With the sphere power and axis preset, center the lensometer target on the reticle. If the mires are unclear, focus the power wheel or axis wheel. @The question is, how far away from the expected value can the sphere power of the prescription be and still be considered acceptable? According to older ANSI standards, for most lenses, the allowable error tolerance was ±0.12 D and for higher powers, the allowable error tolerance increased. Now the power standard is not based on the sphere power, but on the meridian of highest absolute power. To know if this power is off, we may need to finish reading the full spherocylinder prescription.
- 48. So before deciding on power acceptability, we will write our sphere finding down and go on to the cylinder. Cylinder axis error tolerances vary, depending on the strength of the cylinder power. For small 0.25 D cylinders, the axis can deviate up to 14 degrees either way. If the cylinder power is equal to 1.75 D or greater, however, the tolerance drops to ±2 degrees. An easy way to visualize axis tolerances is to think of a cross with the 0.25 D cylinder on the bottom and 1.75 D on the top. Drawing an “Axis Tolerance Cross” is a simple way to remember the cylinder axis tolerances for each cylinder power.
- 49. Cylinder Power Verification and Error Tolerance The ANSI standard cylinder power tolerances vary depending on the strength of the cylinder. For cylinder with a power of 2.00 D or less, this tolerance is ±0.13 D. For cylinders from 2.25 D through 4.50 D, tolerance is ±0.15 D. Above these powers the tolerance is 4% of the cylinder power. When using a standard lensometer, this means the cylinder power tolerance is close to 1/8th diopter.
- 50. Checking for Unwanted Vertical Prism
- 51. Verifying Lens Segments and Surfaces • Verification of the Multifocal Segment To verify the size and location of the multifocal segment, check the following: 1. Check segment height. 2. Check flat-top bifocals for tilt by placing a ruler across the seg tops. 3. Measure seg width with a ruler at the widest part of the seg. 4. To verify the near PD ordered, measure the distance from the left side of one seg to the left side of the other. 5. A lens pair should be within 2.5 mm of the ordered amount to be within standards. When both multifocal segments are identical, it is easier to measure near PD from the left side of one segment to the left side of the other than from center to center.
- 52. Checking for Small Surface and Media Defects • Check for internal media defects, such as bubbles and striae in the lens material. • Also inspect the surface for scratches, pits, or areas of grayness. • Check for waves To inspect for a wave in the surface of a lens, view a grid or straightedge through the lens, moving the lens slowly so that the image of the line traverses the surface slowly. An irregularity in the otherwise smooth image shows the presence of a wave.
- 53. Verification of Frames and Quality of Mounting • First check the quality of the mounting (the lens insertion). • The security of the lenses will be revealed by the presence or absence of an air space between lens and frame. • Check to be sure that the frame concurs exactly with all ordered specifications: (1) style and color, (2) eye size and DBL, and (3) length of temple. (4) Be sure to inspect for possible frame damage, such as scratched or marred surfaces, or rolled eyewires.
- 55. What is wrong with each of the following (Questions 1-4): 1. OS: −4.25 −0.75 × 010 OD: −4.50 sphere 2. +4.5 −1.0 × 017 3. +0.50 −1.75 × 12° 4. +2.00 −.75 × 033 QUIZZIE The Rx was written in reverse and should appear as: O.D. −4.50 Sphere O.S. −4.25 − 0.75 × 010 Carry components to 2 decimal places: +4.50 − 1.00 × 017 Leave degree sign off axis reading Use a prefactory zero before the cylinder value: +2.00 − 0.75 × 033
- 56. 2. An individual with badly scratched lenses wants a new pair of glasses. You read the existing prescription from the old glasses to make the new pair. You also measure the wearer’s PD. The distance between the OCs in the existing spectacles is found to be significantly different from the wearer’s PD. Which of the following reasons for this are possible? a. There may be cylinder present in the prescription. b. There was an error in making the original glasses. c. There is prescribed prism in the original prescription. d. Both lenses in the prescription are simply spheres. Ans : b,c
- 57. 3. True or False? Always use the actual order form to verify a prescription received from the laboratory. Ans: false, original examination form or prescription should be used 4.To check for strain in a lens, what instrument is used? a. Ophthalmoscope b. Retinoscope c. Colmascope d. Lensometer e. c or d may be used Ans c
- 58. 5. A “distometer” is used in an optical dispensary to measure: (A) Patients’ PDs (B) Frame PDs (C) Vertex distances (D) Seg heights Ans c 6. Some frame types do not have an eyewire going completely around the lens. Frames of this nature are called: (A) Supras (B) Shields (C) Mountings (D) Chassis Ans c