Bifocal Semi Finished Lens Blanks , Flat Top CR39 1.499 Ophthalmic Blanks

Model: Semi Finished Bifocal
Brand: Aogang
Code: 9001509900
Refractive Index: 1.499
Diameter: 70/28mm
Monomer: CR39
Abbe Value: 58
Specific Gravity: 1.32
Transmission: > 97%
Coating Choice: UC
Power Range: Base: 2/4/6/8 ADD; +1.00~+3.50

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Technical Data

1.499 S/F FLAT TOP BIFOCAL BLANKS
MARTERIAL REFRACTIVE INDEX=1.499 TOOLING INDEX=1.530
Diameter(mm)	Nominal Curve	Front Radius	T.C	Back Radius	BACK T.C	CT/ET	Frong sag Ring 50mm	RX Range Recommended
ɸ70	200B	234.27	2.26	94.93	5.58	10.0/14.0	1.34	-5.25Dto-8.00D
ɸ70	400B	127.62	4.15	94.93	5.58	10.0/12.0	2.47	+2.00Dto-5.00
ɸ70	600B	87.18	6.08	161.04	3.29	9.0/6.0	3.66	0.00Dto+4.00D
ɸ70	800B	66.49	7.97	161.04	3.29	13.0/6.0	4.88	-4.25Dto+6.00D

Bifocal Semi Finished Lens Blanks , Flat Top CR39 1.499 Ophthalmic Blanks

Product Features

Bifocals have the unique ability to give two lens powers so that you can see both near and far. The bottom portion of the lens is used for seeing up close like with reading or computer work. The top portion is for distance but some people do not need it so sometimes that portion has no prescription in it at all. It will vary with each person.

As their name suggests, bifocal eyeglass lenses have two lens powers — one for distance and one for near.

The lower half of a bifocal lens contains the near segment for reading and other close-up tasks. The rest of the lens is usually a distance correction, but sometimes has no correction at all in it, if you have good distance vision.

Bifocal Semi Finished Lens Blanks , Flat Top CR39 1.499 Ophthalmic Blanks

When people inch closer to forty, they may find that their eyes are not adjusting to distances as they used to, the lens of the eyes begin to lose flexibility. It becomes difficult to focus on close objects. This condition is called presbyopia. It can be managed to a large extent with the use of bifocals.