Ординатура / Офтальмология / Английские материалы / Essentials of Ophthalmic Lens Finishing, 2nd edition_Brooks_2003

S E R I E S 5

Progressive Addition Lenses: Using Hidden ‘Circles’

Reference: Pages 102 through 105.

Laying out progressive lenses is possible using the hidden marks on a progressive lens instead of the fitting cross. Hidden circles are permanent marks on the lens and are not subject to error. Fitting crosses are removable marks placed on the lens using the hidden “circles” as reference.

For the exercises in this section, use the hidden circles to lay out the lens instead of the fitting cross and perform the following steps:

•Determine monocular distance decentration.

•Calculate hidden circle raise (or drop) based on the fitting cross height. (For these exercises, assume that the fitting cross is 4 mm above the level of the PRP and hidden “circles.”)

•Lay the lens out for edging.

•Mark the lens with a cross to indicate the location of the block.

1.A = 48 mm B = 38 mm

DBL = 20 mm

Monocular PDs: R = 32 mm; L = 32 mm Fitting cross heights: R = 24 mm; L = 24 mm

2.A = 44 mm B = 32 mm

DBL = 20 mm

Monocular PDs: R = 30.5 mm; L = 31.0 mm Fitting cross heights: R = 19 mm; L = 19 mm

3.A = 49 mm B = 34 mm

DBL = 21 mm

Monocular PDs: R = 31.5 mm; L = 30.5 mm Fitting cross heights: R = 20 mm; L = 21 mm

4.A = 47 mm B = 36 mm

DBL = 19 mm

Monocular PDs: R = 32.0 mm; L = 31.5 mm Fitting cross heights: R = 24 mm; L = 23 mm

5.A = 40 mm B = 30 mm

DBL = 24 mm

Monocular PDs: R = 30.0 mm; L = 31.0 mm Fitting cross heights: R = 19.5 mm; L = 20.0 mm

6.A = 50 mm B = 38 mm

DBL = 18 mm

Monocular PDs: R = 33.0 mm; L = 32.5 mm Fitting cross heights: R = 23.5 mm; L = 25.0 mm

7.A = 49 mm B = 39 mm

DBL = 20 mm

Monocular PDs: R = 34.0 mm; L = 32.5 mm Fitting cross heights: R = 26 mm; L = 27 mm

8.A = 47 mm B = 38 mm

DBL = 19 mm

Monocular PDs: R = 31.5 mm; L = 32.5 mm Fitting cross heights: R = 23.5 mm; L = 24.5 mm

9.A = 44 mm B = 37 mm

DBL = 20 mm

Monocular PDs: R = 32.5 mm; L = 31.0 mm Fitting cross heights: R = 21.5 mm; L = 22.0 mm

10.A = 46 mm B = 39 mm

DBL = 19 mm

Monocular PDs: R = 31.0 mm; L = 30.0 mm Fitting cross heights: R = 26.5 mm; L = 25.5 mm

S E R I E S 6

Flat-Top Bifocals

TOTAL INSET AND DROP CONSIDERED INDEPENDENTLY

Reference: Pages 112 through 114.

For the following problems, lay out a flat-top bifocal lens for the correct bifocal height. (For these exercises, do not be concerned about total inset.) Be concerned only with the vertical position of the segment line.

1.Frame B = 42 mm Segment height = 18 mm

2.Frame B = 42 mm Segment height = 21 mm

3.Frame A = 48 mm B = 38 mm

Segment height = 17 mm

4.Frame A = 50 mm B = 43

Segment drop = –4 mm

(What is the segment height?)

5.Frame A = 52 mm B = 42 mm

DBL = 18 mm Segment raise = +1 mm

(What is the segment height?)

6.Frame A = 54 mm B = 41 mm

DBL = 17 mm

Segment height = 17 mm

For the following prescriptions, assume that the segment top moves –3 mm vertically for the segment drop. Position the lens for marking such that both the drop and the total inset are correct. (The lens does not need to be “spotted” ahead of time for this exercise.) The lens should be positioned front side up. Mark the lens with your water-soluble marker for blocking.

7.Right lens

A = 48 mm DBL = 20 mm

Near PD = 60 mm

8.Right lens

A = 51 mm DBL = 17 mm

Near PD = 60 mm

9.Left lens

A = 50 mm DBL = 18 mm

Near PD = 58 mm

10.Right lens

A = 55 mm DBL = 18 mm

Wearer’s PD = 66/62

11.Left lens

Lens power is +1.00 –0.75 × 180

A = 53 mm DBL = 17 mm

Wearer’s PD = 64/60

12.Right lens

A = 52 mm DBL = 17 mm ED = 57 mm

Wearer’s PD = 62/59

S E R I E S 7

Flat-Top Bifocals

TOTAL INSET AND DROP CONSIDERED SIMULTANEOUSLY

Reference: Pages 117 and 118.

For each of the following exercises, position the flat-top bifocal lens on the centration device for the amount of total inset and segment drop given. Assume the lens to be front side up and mark the lens for edging using your water-soluble overhead transparency marking pen.

1.Total inset = 4 mm Segment drop = –4 mm

2.Total inset = 5.5 mm Segment drop = –3 mm

3.Total inset = 7 mm Segment drop = –2 mm

4.Total inset = 2.5 mm Segment drop = –5 mm

5.Total inset = 4.5 mm Segment raise = +1 mm

6.Total inset = 3 mm Segment drop = –3.5 mm

7.Total inset = 5 mm Segment drop = –6 mm

For each of the following problems, lay out a flat-top bifocal lens for both the correct bifocal height and total inset. The lens should be positioned front side up for this exercise and does not need to be “spotted” ahead of time. Mark the lens with a cross with your water-soluble marking pen to indicate where the center of the block will be.

8. Right lens

A = 53 mm

B = 44 mm

DBL = 18 mm

Wearer’s PD = 65/61

Segment height = 18 mm

9. Right lens

A = 49 mm

B = 38 mm

DBL = 18 mm

Wearer’s PD = 65/62

Segment height = 18 mm

10. Left lens

A = 51 mm

B = 42 mm

DBL = 17 mm

Wearer’s PD = 61/58

Segment height = 19 mm

11. Left lens

A = 54 mm

B = 44 mm

DBL = 16 mm

Wearer’s PD = 63/59

Segment height = 18 mm

12.Right lens

Lens power is +8.00 –1.00 × 17

A = 50 mm

B = 41 mm

DBL = 20 mm

Wearer’s PD = 66/61

Segment height = 20 mm

13.Left lens

Lens power is –7.75 –0.50 × 95

A = 48 mm

B = 43 mm

DBL = 19 mm

Wearer’s PD = 64/61

Segment height = 17 mm

14.Right lens

Lens power is +1.00 –3.00 × 18

A = 52 mm

B = 42 mm

DBL = 19 mm

Wearer’s PD = 61/57

Segment height = 23 mm

S E R I E S 8

Curve-Top Bifocals

Reference: Pages 125 and 126.

Curve-top segments are positioned in a manner similar to that of flat-top bifocals. The highest part of the curve is placed at the millimeter line coinciding with the required drop. The outer segment corners must be on, or equidistant from, the same horizontal line to ensure straightness upon completion.

Carry out the centration process with curve-top lenses, marking the lens with the front-side-up. (Do not forget to mark whether the lens is the right or left.)

1.Right lens

A = 48 mm B = 45 mm

DBL = 14 mm PD = 53/50

Segment height = 18 mm

2.Right lens

A = 52 mm B = 45 mm

DBL = 22 mm PD = 64/62

Segment height = 20 mm

3.Left lens

A = 58 mm B = 47 mm

DBL = 17 mm PD = 68/64

Segment height = 18 mm

4.Right lens

A = 54 mm B = 44 mm

DBL = 16 mm PD = 67/63

Segment height = 22 mm

5.Left lens

A = 57 mm B = 53 mm

DBL = 16 mm PD = 65/62

Segment height = 23 mm

6.Left lens

A = 54 mm B = 47 mm

DBL = 16 mm PD = 61/58

Segment height = 22 mm

7.Right lens

A = 55 mm B = 48 mm

DBL = 16 mm PD = 67/63

Segment height = 25 mm

8.Left lens

A = 46 mm B = 39 mm

DBL = 22 mm PD = 64/61

Segment height = 18 mm

9.Left lens

A = 52 mm B = 47 mm

DBL = 19 mm PD = 65/61

Segment height = 19 mm

10.Right lens

A = 52 mm B = 44 mm

DBL = 19 mm PD = 62/59

Segment height = 19 mm

11.Left lens

A = 58 mm B = 48 mm

DBL = 20 mm PD = 67/65

Segment height = 22 mm

12.Right lens

A = 46 mm B = 39 mm

DBL = 20 mm PD = 65/62

Segment height = 18 mm

S E R I E S 9

Trifocal Lenses

Reference: Page 125.

Trifocal lenses are centered in exactly the same manner as their corresponding bifocal styles. Always remember that the upper of the two segment lines is used for a segment height reference point.

Using a flat-top trifocal positioned front side up, lay out and mark the lens for each of the following.

1.Left lens

A = 46 mm B = 37 mm

DBL = 22 mm PD = 67/65

Segment height = 20 mm

2.Right lens

A = 50 mm B = 42 mm

DBL = 19 mm PD = 52/49

Segment height = 20 mm

3.Right lens

A = 52 mm B = 42 mm

DBL = 20 mm PD = 60/57

Segment height = 17 mm

4.Right lens

A = 54 mm B = 51.5 mm

DBL = 16 mm PD = 67/64

Segment height = 21 mm

5.Right lens

A = 54 mm B = 46 mm

DBL = 17 mm PD = 67/64

Segment height = 24 mm

6.Left lens

A = 54 mm B = 46 mm

DBL = 24 mm PD = 69/66

Segment height = 20 mm

7.Right lens

A = 56 mm B = 52 mm

DBL = 16 mm PD = 65/63

Segment height = 22 mm

8.Right lens

A = 48 mm B = 41 mm

DBL = 19 mm PD = 58/56

Segment height = 24 mm

9.Left lens

A = 58 mm B = 50 mm

DBL = 19 mm PD = 64/61

Segment height = 21 mm

10.Left lens

A = 57 mm B = 53 mm

DBL = 16 mm PD = 65/63

Segment height = 25 mm