In last month’s article, we looked at the case study of Sally, who works in a call centre five days a week for eight hours a day.
Sally is 58 years old, and her prescription is:
RE +1.25/+0.75 X 50
LE +1.50/+0.50 X 140
Near Add +2.25 – Intermediate Add +1.25
Sally’s screen is positioned at arm’s length, at eye level, and she needs to read notes on her desk. She also has a second screen next to the first one. She drives to work and has a pair of progressive addition lenses (PALs) for general wear but finds them difficult to use at work.
Last month, we considered dispensing occupational bifocals and single vision intermediate lenses to Sally. This month, we look at occupational progressive addition lenses (OPALS) and enhanced reading lenses.
What’s the difference?
The difference between OPALS and enhanced readers is that OPALS generally allow a restricted room distance at the top of the lens, in addition to intermediate and near areas, whereas enhanced readers provide near and intermediate areas only. Neither options are suitable for driving and this must be explained to the patient.
The advantage of OPALS is that they do allow the wearer to look up and see clearly across the room (up to about four metres) whereas enhanced readers do not. They also have significantly wider intermediate and near areas than conventional PALs, although the intermediate and near areas provided by an enhanced reader are even greater.
When and why to prescribe
If we consider our case study, Sally, we need to ask careful questions to determine which lens type would be best for her. We need to know her working distance: for example, does she work on the screen only, without the need to see at any further distances?
Probing questions should be asked, such as: “Do you need to see across the room?”; or “Do you need to see anything beyond the screen?” Other questions, such as: “Does your job involve attending meetings?”, are important as this would possibly involve looking across a room.
Once we have established whether Sally needs to see beyond the screen or not, we can begin to advise her on lens choice.
As Sally has two screens at eye level, an enhanced reader would allow her to look directly at the screen through the upper part of the lens and would provide a wider area for the screen than an OPAL, whilst being able to see her notes though the lower part of the lens. This would mean she could position her chair, so her eyes were level with the screen.
If, however, Sally did need to see across the room, we could dispense an OPAL. Unlike a standard progressive lens, an OPAL does incorporate part of the reading addition at the fitting cross. This is necessary to view objects at intermediate distances. If Sally positioned her chair with her eyes level with the screen, and she looked straight ahead, she would be looking through, or close to, the fitting cross.
Depending of the screen distance, the reading addition at the fitting cross may be sufficient to view the screen clearly without significant head movement. However, she may need to tilt her head back a little to see the screen, although not as much as she would need to do with a standard progressive lens. The area above the fitting cross of an OPAL provides distance vision to about 4m, which Sally would use to see across the room. This may require Sally to drop her head slightly to look over the fitting cross.
This can be overcome by either raising her chair up or lowering the screen down – or a combination of both – so she will be looking through the correct part of the lens when looking at the screen. She would need to turn her head more to see the second screen with an OPAL, compared to an enhanced reader – but this may be a problem as she is using two screens.
It is evident that there are many lens options for a computer user, and careful questioning combined with careful lens selection will result in the best outcome for your patients.
Sue Deal FBDO R is a practising dispensing optician, ABDO College examiner, senior tutor and supervisor for dispensing opticians. She is also a practice visitor and external moderator for ABDO.
Read OA Corner Part 13: PPLs demystified here.
Links to previous articles can be found here.