1993, 1998, 2004, all rights reserved, Lenstech LLC
Copyright
1993, 1998, 2004, all rights reserved, Lenstech LLC
4.0 Requirements
4.1 Impact Resistance: All lenses shall be in compliance with the Federal Regulation on Impact Resistant Lenses (21 CFR 801.410).
4.2 Flammability: No part of the spectacle shall ignite when tested for flammability in accordance with the procedure specified in 5.2. Deformation or any other deterioration, other than ignition, of the spectacles is permitted. Compliance is required of individual frames, lenses or the assembled product.
4.3 Cosmetic Quality: Lenses shall be reasonably free from pits, scratches, grayness, water marks, bubbles, cracks, striae, inclusions and local irregularities which produce aberrations that would impair or prevent the use of the lenses for their intended purpose as determined by product experience and normal actual use conditions. The test procedure is described in 5.3.
4.4 Optical Quality: Lenses shall be free from severe lensometer target element distortion or blur when tested in accordance with the procedure specified in 5.4. Areas outside a 20 millimeter radius from the datum center or within 6 millimeters of the edge, need not be tested for optical quality.
4.5 Refractive Properties
Refractive properties are to be measured in accordance with the procedure specified in 5.5.
4.5.1 Refractive Power: The refractive power of an individual lens shall be spherical, aspherical (by design) and positive. The range of powers used for reading at the normal distance is between +1.0 and +4.0 diopters. Higher powers are intended for reading at closer distances or for hobbies.
4.5.1.1 Designated Refractive Power: The manufacturer or distributor shall designate the refractive power of each pair of spectacles.
4.5.1.2 Refractive Power Variation Between Designated and Actual: The actual refractive power shall be within (+ /-) 0.13 diopters of the designated refractive power.
4.5.1.3 Refractive Power Imbalance: The difference in refractive power between a mounted pair of lenses or between lenses of similar design intended for mounting in a frame shall not exceed 0.19 diopters.
4.5.2 Astigmatic Power: The maximum difference in refractive power between any two meridians within an individual lens shall not exceed 0.13 diopters.
4.5.3 Prismatic Power
4.5.3.1 Individual Lenses: The prismatic power in any meridian, measured at the reference points of each lens mounted in a frame or of lenses of similar design intended for mounting in a particular frame, shall not exceed 0.25 prism diopters. Bifocals must meet the segment location requirements of 4.6.
4.5.3.2 Imbalance Between Lenses: The prismatic power imbalance of lenses mounted in a frame or of lenses of similar design intended to be mounted in a particular frame, shall not exceed the following tolerances:
4.5.3.2.1 Vertical Tolerance: 0.33 prism diopters maximum
4.5.3.2.2 Horizontal Tolerance: 0.75 prism diopters maximum
4.5.4 Localized Power Errors: Localized power errors or aberrations caused by waves, warpage, or internal defects which are detected by visual inspection, are permissible if no severe lensometer target element distortion or blur is found when the localized area is examined in accordance with the procedure specified in 5.4. Areas outside a 20 millimeter radius from the datum center or within 6 millimeters of the edge, need not be tested for localized power errors.
4.5.5 Optical Centers: The optical centers of lenses mounted in a frame shall be approximately in front of the pupils when reading and shall be located so that the resultant prismatic powers do not exceed the tolerances stated in 4.5.3. In order to meet the specified individual lens and imbalance between lenses tolerances, the optical centers must not vary from the reference points more than the following tolerances:
|
DESIGNATED REFRACTIVE POWER |
MAXIMUM ALLOWABLE VARIATION OF OPTICAL CENTERS | ||
|---|---|---|---|
| INDIVIDUAL LENSES | LENS PAIRS | ||
| IN ANY MERIDIAN | VERTICAL | HORIZONTAL | |
| (RP) | (H) | (H) | (H) |
| (Diopters) | (Millimeters) | (Millimeters) | (Millimeters) |
|
+1.00 |
2.5
|
3.3
|
7.5 |
Notes:
1.) This table is intended as a guide and may be extended to include refractive powers not listed.
2.) The maximum variation of optical centers data was calculated by using Prentices Rule and solving for the distance in millimeters: H=10 (PP/RP), where H= distance from optical axis or distance between optical centers in millimeters, PP= prismatic power at a point in prism diopters (0.25 for individual lenses, 0.33 for imbalance vertical, 0.75 for imbalance horizontal), RP= refractive power in diopters.
3.) Maximum variation measurements of individual lenses are to be taken from the reference points to the optical centers of the lenses.
4.) Imbalance measurements are to be taken from the optical centers of the lenses.
4.5.6 Distance Between Optical Centers: The horizontal distance between optical centers of lenses mounted in a frame or of lenses of similar design intended to be mounted in a frame should be equivalent to the near interpupillary distance.
4.5.6.1 Direction of Measurement: Distance between optical centers should be measured between axes passing through the optical centers and perpendicular to the datum line.
4.6 Segment Location
Segment location should be measured in accordance with the procedure specified in 5.6.
4.6.1 Vertical (Segment Drop)
4.6.1.1 Individual Lenses: Drop should be within (+/-) 1 .0 millimeter of specification. In the absence of specifications, drop should be 5 to 6 millimeters from a horizontal line through the reference point.
4.6.1.2 Imbalance Between Lenses: Difference in drop levels in mounted lenses should not exceed 1.0 millimeter. The drop in mounted lenses should appear symmetrical and balanced.
4.6.2 Horizontal (Segment Inset)
4.6.2.1 Individual Lenses: Inset should be within (+/-) 1.0 millimeter of specification. In the absence of specifications, inset should be 5 to 6 millimeters from a vertical line through the reference point.
4.6.2.2 Imbalance Between Lenses: Difference in inset horizontal positions in mounted lenses should not exceed 2.0 millimeters. The inset in mounted lenses should appear symmetrical and balanced.
4.6.3 Segment Tilt: The edges of straight-edged-top segments should not tilt more than 0.5 millimeter in the horizontal direction.
4.7 Ultraviolet Attenuating Lens
Manufacturers of lenses who claim specific ultraviolet attenuating properties, shall state the average percent ultraviolet radiation attenuated or blocked, in the wavelength regions of 290 to 315 nanometers (ultraviolet UVB) and 315 to 380 nanometers (ultraviolet UVA). See 5.7 for the method of calculation.
4.8 Lens Design
The lens shall be designed to control marginal astigmatism for the reading distance. Lenses that meet this requirement are known as Corrected Curve Lenses and have concave ocular curves between -2 and -7 diopters.
4.9 Frame Design
Frames shall be designed for near vision. The angle between the optical axis of the lens and the line of sight shall be no greater than 10 degrees in the as worn condition.
4.10 Frame Finish
The surface finish of metal and plastic frames shall be free of significant imperfections or roughness. All hardware or other components shall be free of burrs or hazardous projections. Excessive polishing compounds or other processing residue shall not be present.
4.11 Compliance and Sampling Procedures
Compliance with the impact resistance requirements specified herein, shall be determined by 100 percent testing or by testing of a statistically significant sample (for example, conforming to the requirements of ANSI/ASQC Zl.4-1981) of each production batch at an appropriate stage of manufacture.
Compliance with the requirements for flammability, cosmetic quality, optical quality, refractive properties, segment location and ultraviolet attenuating properties specified herein, shall be determined by the manufacturer using an accepted statistically significant sampling procedure (for example, ANSI/ASQC Zl.4-1981) at an appropriate stage of manufacture.
4.12 Country of Origin
The frame must be stamped or marked indicating the country of origin.
4.13 Labeling
4.13.1 Intended Refractive Power: Each pair of spectacles shall be marked or labeled to indicate its intended refractive power in diopters.
4.13.2 Intended Interpupillary Distance: The intended interpupillary distance should be indicated on the frame. An alternative to marking the interpupillary distance on the frame is to identify the product for use by specific gender: female (56 to 58 millimeters), unisex (58 to 60 millimeters), and male (60 to 64 millimeters).
4.13.3 Instructions: The following statement shall be displayed at point of purchase: "This product is intended to be an aid for vision at near distances such as use as reading glasses and is not intended to replace prescribed corrective eyewear and professional eye examinations and care". Modifications of this statement or any other statements displayed at the point of purchase, are subject to review and approval.
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