Occupational Progressive Lenses Jim Sheedy Butzon SP, Sheedy JE, Nilsen E. The efficacy of computer glasses at reducing worker symptoms. Journal of the American Optometric Association 2002;73(4):221-30. Sheedy JE, Hardy RF. The Optics of Occupational Progressive Lenses. Optometry 2005;76:432-441.

Common optical corrections for presbyopia – how do they work at the computer? Bifocals Progressive Addition Lenses

Visual Symptoms Eye strain or ache Dry, irritated eyes Tired eyes Headaches Blurred vision Neck and back aches

PAL vs. OPL

OPL Features Lower amount of distortion – hence easy adaptation Can wear when walking around the office Don’t need to take on and off all the time Full near power in bottom of lens Unwanted distortions are higher in the lens – because indoor work is performed with downward gaze.

Occupational Progressive Lenses All designs are based upon your usual distance/near prescription Lens powers are based upon the near power “Degression” is power difference between top and bottom of lens

Prescribing OPLs Prescribe the usual Distance Rx with normal 40 cm add Specify the OPL of choice Customize if needed

Rotlex instrument

Measurement methods Lenses Rotlex measurements were parsed Ordered for plano distance, +2.50 add Emmetropic patient without accommodation Therefore viewing distance is a direct function of add power Rotlex measurements were parsed Center of coordinate system is pupil as specified by manufacturer Areas limited by 15 mm above and 25 mm below pupil Based upon generous estimate of foveal usage area. Areas constrained by 0.50 D astigmatism

AO Technica Cosmolit Office Essilor Interview Hoya Tact Shamir Office Sola Access Zeiss Gradal RD

Area of viewing zones (mm2) PALs – Intermediate range is 15-25 mm2, near range is 40-80 mm2

Display Height The screen center should be 4-9 inches lower than your eyes 10-20 degrees of ocular depression

Visual comfort contours Centered at about 15 degrees downward

Downward viewing is preferred (Menozzi et al, 1994)

OPLs with degression series Cosmolit Office Shamir Office Sola Access The desired near-intermediate zone for computer users is somewhat high in the lens for both Shamir Office and SOLA Access, whereas it is appropriately located for Cosmolit Office. For Cosmolit Office the unwanted astigmatism is in the lower portions of the lens, resulting in a narrow viewing zone at Y = -10 to -15. Despite that narrow zone, however, the area of the near-intermediate is quite large because that zone widens significantly above Y = -5 mm. Likewise, because the viewing zone widens in the upper portions of the lens, the far-intermediate zone is very wide and large for Cosmolit Office. Shamir Office, on the other hand, is opposite: the unwanted astigmatism is high in the lens and the near zone is wide and large, near-intermediate and far-intermediate zones are considerably smaller. The unwanted astigmatism for SOLA Access is lateral to lens center. This design results in very large near and near-intermediate zones. There is no far-intermediate zone in this lens - largely because the lens has a degression of only 1.25 D. whereas Cosmolit Office and Shanir Office each has a 1.75 D. degression for an add of +2.50 D. For lower adds, SOLA Access would likely also have a far-intermediate zone.

Other approaches Zeiss Gradal Essilor Interview A degression for each add power Always designed to have +0.50D in top of lens Essilor Interview Only 1 degression – 0.86D Works best for person who spends continuous time at computer Probably need to remove or change glasses to walk around office

Other approaches Essilor Interview Zeiss Gradal RD The Gradal RD (Zeiss) +0.50 add in the top portion of the lens. also has 0.25 D. power degression steps similar to Tact and Technica. greater similarity to a traditional PAL than the other OPLs. large far-intermediate zone that is located from mid-pupil upward The near-intermediate and near zones are reasonably sized. well-suited for a person who ambulates frequently in an indoor environment and who also spends a fair amount of time working at a computer. Interview (Essilor) one low power degression option to be used regardless the prescribed add amount. extremely low magnitude of astigmatism, a result of the low power degression. extremely large near and near-intermediate zones – however it should be noted that the near-intermediate zone is entirely comprised of the largest power in that range (Table 5) and is also located quite high in the lens (Figure 3). For a patient with +2.50 add, the top of this lens provides add of +1.75 or for a viewing distance of 57 cm. This lens can specifically meet the needs of a computer user while sitting at the computer workstation, but would not enable good vision for ambulation. Because of its low degression amount, this lens is good for dedicated work at a computer and for lower add levels in which the near-intermediate zone would be lower in the lens.

Essilor Interview Prescribe like a reading lens 2 degressions: 0.80 D and 1.30 D Designed for steady computer work

Zeiss Gradal RD Many degressions Selected to provide +0.50 in top

Other approaches Small area of distance power in top of lens Hoya Tact AO Technica For uses where a small area of distance clarity is required

OPLs with distance power Area (mm2) OPLs with distance power AO Technica Hoya Tact These designs appear to be optimal for those who need an OPL but also require a small area of distance vision. Examples could be a stockbroker who needs to see the stock sale display across the room or a worker on a manufacturing floor who needs to occasionally see detail across the room. Both of these designs also have greater magnitude of unwanted astigmatism than the others, a direct result of the greater power degression compared to other OPLs. Between the 2 designs, Technica has a considerably wider and larger near area, but Tact has considerably wider and larger far areas. Both designs provide the near-intermediate zone for computer viewing with an appropriate amount of ocular depression. However, the near-intermediate zone widths and areas (Tables 4 and 5) for both lenses are less than in most other designs - an outcome of the larger power degression in these 2 lens designs. The primary advantage of these 2 designs is the provision of a small far zone; however the size of the computer-viewing distances is compromised as result. Between the 2 designs, Technica should be better suited for a person that spends more time at their desk, and Tact for a person that has greater far viewing needs.

AO Technica Has full distance power Steady power change Lateral aberrations

Hoya Tact Full distance power Steady power change Lateral aberrations

Area of viewing zones (mm2) PALs – Intermediate range is 15-25 mm2, near range is 40-80 mm2

Locations of viewing zones

Summary

Member Affiliate Members Supporting groups Vision Ease Lens Crafters Shamir Insight Carl Zeiss Vision J&J Spectacle Lens Group Supporting groups Optical Laboratories Association COLTS laboratories

Collaborators Charles Campbell Ray Hardy John R. Hayes Chunning Huang Matt Helfrich Ewen King-Smith Priya Ramamoorthy Allan Yi Karl Citek Bret Andre