standard frame alignment for basic frame adgustment
- 1. Standard frame alignment Mikael G. MSc in clinical optometry
- 2. STANDARD ALIGNMENT OR “TRUING” OF FRAMES - adjusted to certain impersonal standards that are independent of the type of face to which it is to be fitted. - The best time to pre adjust is when the prescription is being verified.
- 3. “Truing” spectacles is a good starting point for adjusting them, especially spectacles that have been worn for a long time without recent adjustment. A general rule for standard alignment is to begin with the bridge, then work with the end pieces, and handle the temples last.
- 4. • Obviously, changes made in one part of a frame may influence the alignment in another part. • Bending the bridge, for example, may change the relationship of the temples. • Handling the bridge first, and the other parts in order, helps to eliminate having to go back and realign parts.
- 5. Adjustable plastic frames must almost always be heated to be aligned. Metal frames and parts do not require heating, except for metal parts that are covered with plastic.
- 6. Standard Alignment of Plastic Frames HEATING THE FRAME Standard plastic frames must be heated for any alignment. Standard procedure for adjusting the frame should be followed, beginning with the bridge. Only that area of the frame requiring adjustment should be heated to avoid the possibility of disturbing an aligned area by mistake.
- 8. THE BRIDGE Readjusting the lenses to their proper planes is accomplished by first heating the bridge area, then grasping the frame by the lens areas and adjusting according to the correction desired. When using a salt pan to heat the bridge, stir the salt in the pan and form it into a centrally located peak running across the pan.
- 9. • Place the frame in the pan, temples up, and draw the bridge through the peak of the salt mound. • Repeat until the bridge is pliable enough to be bent.
- 10. Move the bridge through the hot air stream until it becomes pliable. If one lens is higher than the other, they are said to be out of horizontal alignment. If one lens appears to be farther forward or backward than the other, they are said to be out of vertical alignment.
- 11. Horizontal Alignment It is not easy to check for horizontal alignment of a plastic frame because there are not always clear reference points. To check for horizontal alignment, place a ruler or straight edge across the back of the frame at the top of the pads. Both endpieces should be equidistant. Causes: Rotated Lens Skewed Bridge
- 12. Vertical Alignment (Four-Point Touch) To check place a ruler or straight edge so that its edge goes across the inside of the entire front of the spectacles below the nose pad area. Theoretically the frame eyewire should touch at four points on the ruler
- 13. Face Form Face form or wraparound is when the frame front is just slightly rounded to the form of the face. Frames with face form will not conform to the four point touch test, but must be symmetrical nonetheless. The temporal sides of the eyewires should touch, and the nasal sides should be equidistant from the ruler.
- 14. Too much face form would be evident if the two nasal eye wires are a great distance from the ruler. The remedy for either too much or too little face form is to alter the bridge. First warm then grasp the frame by the lenses and eye wires with thumbs on the inside and fingers on the outside. Bend the bridge by turning the lenses inward or outward.
- 15. X-ing The frame front may be twisted so that the planes of the two lenses are out of coincidence with each other. This is called Xing because the eye wires of the frame front form an X when viewed from the side. X-ing causes the temples to be out of line with each other.
- 16. • When ever the temples do not appear parallel, the frame should first be examined for X-ing before other methods of realigning the temples are tried. • X-ing is corrected by grasping the eye wires and rotating the hands in opposing directions until the planes of the lenses are parallel.
- 17. Variant Planes Another form of vertical misalignment is when the lens planes are variant, or out of coplanar alignment. the lens planes are parallel, but one lens is farther forward than the other. push the entire eyewire away from you on one side, and pull it toward you on the other side, all the while keeping both lens planes parallel to each other.
- 18. THE TEMPLES The open temple spread is checked first because the adjustments may affect the end pieces. After this, temple parallelism is considered, followed by alignment of the temple ends. Finally the temple fold angle is corrected. .
- 19. Open Temple Spread The open temple spread, or let-back, is that angle that each open temple forms in relationship to the front of the frame. To afford a true picture of the temple spread initially, the temple shafts must be straight. Any curve to the temple shaft should be eliminated by heating the temple and straightening it with the hands. It is the normal condition of the temple to be opened out slightly farther than a 90-degree angle; usually 94-95 degrees.
- 20. Temple Parallelism For frames to be in standard alignment, the temples need to be parallel to one another and should not be angled down more than the other. When looking at the glasses from the side, the angles the temples make with the frame front determine temple parallelism. Pantoscopic angle is the angle the frame front deviates from the vertical when the glasses are held with the temples horizontal. Viewing the frames from the side, when the lower rims of the frame front are closer to the face than are the upper rims.
- 21. • A proper pantoscopic angle may vary from as little as 4 degrees up to 18 degrees. • If the glasses were to be adjusted so that the lower rims are tilted outward from the face, the glasses are said to have “retroscopic” instead of pantoscopic tilt. • In any case, to test whether or not the temples are parallel, position the glasses upside-down on a flat surface with the temples open.
- 22. if both temples sit flat or if one temple is not touching the flat surface. If it is difficult to tell, first touch one temple and then the other to see if the frame wobbles back and forth or if it sits solidly. This procedure is known as the flat surface touch test. If the frame wobbles, it needs correction or it will sit on the face at an angle.
- 23. Temple-Fold Angle The final alignment step is to fold the temples to the closed position and observe the angle formed as the temples cross. The temples should fold so that they are parallel to one another or form slight angles from parallel. These angles should be symmetrical and should cross each other exactly in the center of the frame, in line with the center of the bridge. Proper adjustment to this confi guration permits the spectacle to easily fit into a standard case for glasses.
- 24. Standard Alignment of Metal Frames The primary difference lies in the methods of manipulation used to bring the frame into alignment and the presence of adjustable nose pads. Metal frames require heating only in those places where plastic coats the metal. All other bends are done “cold.” Pliers are used for the majority of adjustments.
- 25. THE BRIDGE Horizontal Alignment To check for horizontal alignment of a metal frame, place a ruler or straight edge across the front of the frame at the point of attachment of the pad arms. In most frames, the endpieces will be considerably higher than the level of the pad arms, making the horizontal alignment judgment difficult. The end pieces should be equidistant from the ruler. Causes : Rotated Lens Skewed Bridge
- 26. Vertical Alignment (Four-Point Touch) As when performing the four-point touch test with plastic frames, a ruler or straight edge is necessary to determine whether or not the frame is in alignment. Metal frame construction is so varied, however, that establishing a four-point touch when straddling the inner parts of the frame eye wires is more often impossible than possible. The test is used to analyze the symmetry of the frame front.
- 27. Face Form Metal frames are usually designed with face form, especially in the larger eye sizes. When checking vertical alignment, there are two questions to keep in mind: 1. Does the frame have a four-point touch or a face form curve? 2. If the frame has face form, are the two nasal eye wires equidistant from the ruler or is one farther from it than the other?
- 28. Standard Alignment of Nose pads final adjustment of the pads will vary extensively with the individual shape and flare of the nose of the intended wearer. There are three basic angles that are used for reference when aligning nose pads. These are the frontal, splay, and vertical angles.
- 29. FRONTAL ANGLE (VIEWED FROM THE FRONT) The frontal angle of the nose pads refers to the vertical position of the pads in relation to each other when viewed from the front. The tops of the pads should be closer together than the bottoms, angling in toward each other approximately 20 degrees from a true vertical. Most pads can be “rocked” about a swivel joint. The pads should be slanted for the frontal angle by the same amount.
- 30. Pad Spacing While viewing the frontal angle, observe the amount of space between the eye wires and pads. Both pads should be equidistant from their respective eye wires. An estimated ideal position is for the face of the pads to appear approximately 1 mm closer to the nose than the eye wire itself.
- 31. Pad Height A third point of observation is whether or not both pads occupy the same horizontal plane. If one pad appears higher than the other, the pad arm may be bent upward. It is essential that both pads be in identical rocking positions because if one is erect and one is slanted, their heights may appear dissimilar.
- 32. SPLAY ANGLE This difference then between the back and front edges of each pad, viewed from the top or the bottom, is the splay angle. For initial alignment, a splay angle of 25 to 30 degrees is satisfactory and may be achieved through the use of the pad- adjusting pliers.
- 33. VERTICAL ANGLE (VIEWED FROM THE SIDE) The angle most often neglected in the standard alignment of nose pads is the vertical angle. This angle is especially important in ensuring proper weight distribution under the pad. Ideally the longitudinal (top to bottom) axis of the pad face is in contact with the nose surface in the direction of gravity.
- 34. Standard Alignment of Rimless Eyewear RIMLESS CONSTRUCTION AND LENS MATERIALS Rimless are still more difficult to adjust than plastic and metal frames. Newer mountings use a variety of methods to give extra stability to the mounting. In the past, the lens was held in place with one hole nasally and one hole temporally. Now there may be more than one hole, or a hole and an edge notch used in combination.
- 35. Appropriate Lens Materials If appropriate lens materials are used for rimless mountings, lens chipping is vastly reduced. the best lens materials for rimless mountings are Trivex and polycarbonate.
- 36. ALIGNING THE BRIDGE Whereas the bridge or pad arm origins and the end pieces serve as the line of reference for frames, the mounting line serves as a line of reference for rimless mountings. The mounting line is defined as “the line which passes through the points on the eye wires or straps at which the pad arms are attached. The end pieces may be attached on this line, or as may be the case, above or below this line.
- 37. RIMLESS ADJUSTMENTS Rimless Nose pad Alignment The chief distinction in technique is that the bending of the pad arms should not be attempted unless the base of the pad arm is sufficiently supported to prevent stress on the mounting point and lens. This support can be given by holding the mounting point with rimless bracing pliers while adjusting the pads with pad adjusting pliers.
- 38. Thank you !!!
- 39. Workshop practice guideline 1. Identify lens material. a. glass b. plastic 2. Identify frame material. a. plastic( different type) b. metal (different type) 3. Measure spherical SVL? (at least 5 lenses) 4. Measure sphero cyl SVL? ( at least 5 lenses) 5. Measure bifocals? ( at least 3 lenses ) 6. Measure progressives? ( at least 2 lenses ) 7. Frame selectin, alignment and adjustment?