Choosing Your
Bifocal Lenses
Bifocals have been correcting presbyopia for over two centuries — and for many patients they remain the most practical, reliable, and comfortable choice. This guide covers everything: types, who they suit, honest comparison with varifocals, and what to expect when you first wear them.
Bifocals are not a step down from varifocals. For many patients — particularly drivers, outdoor workers, and those who failed to adapt to progressives — bifocals are the better clinical choice. We will always advise the lens that suits your lifestyle, not the most expensive option.
Section 01
What Are Bifocal Lenses?
A bifocal lens has two optically distinct zones — a large upper area for distance vision, and a smaller lower segment for reading. They remain the most reliable solution for presbyopia when only two focal distances are needed.
Distance zone (upper)
The large upper portion corrects your distance vision — driving, watching television, seeing faces across a room. This zone is wider than the equivalent zone in any varifocal, giving an unobstructed field of view.
Near segment (lower)
A clearly defined optical insert in the lower portion adds the ADD power for reading, phone screens, and close-up work. The segment line between the two zones is visible on close inspection but far less obvious than most patients expect.
Presbyopia — why bifocals exist
Presbyopia is the age-related stiffening of the crystalline lens inside the eye, gradually reducing its ability to change focus between distances. It typically becomes noticeable in the mid-40s — you may find you need to hold reading material further away, or close work causes headaches. It affects everyone eventually. Bifocals correct presbyopia with predictable, reliable optics — no corridor to find, no peripheral distortion, no two-week adaptation period.
Section 02
Types of Bifocal Lens
The type dispensed affects the size of the near zone, the visibility of the line, and how smoothly the eye crosses between the two sections.
D28 Flat-Top
The standard bifocal dispensed today. A straight horizontal top edge (the flat top of the "D") sits in the lower portion of the lens. 28mm wide — generous for most reading tasks.
The flat-top design minimises image jump because the optical centre of the segment is close to the top of the D — significantly more comfortable than older round-segment designs.
D35 Flat-Top
A wider segment — 35mm across — giving a larger near reading field. Ideal for detailed close work (crafts, music, engineering drawings) or high ADD powers.
Requires a deeper frame to accommodate the wider segment without encroaching on the distance zone.
Executive
The segment runs the full width of the lens edge to edge. Provides the widest possible near field with zero image jump.
Rarely dispensed today due to weight and cosmetics, but still used in occupational and low-vision applications.
Section 03
Bifocal vs Varifocal — An Honest Comparison
Neither lens is universally better. The right choice depends entirely on your lifestyle, visual demands, and personal preference.
Bifocals
Varifocals
The computer question. Bifocals do not correct the intermediate distance of a typical monitor (50–75cm). If you spend significant time at a screen, we'd discuss a separate pair of computer spectacles or occupational lenses — or consider whether varifocals better suit your working day overall.
Section 04
Getting Used to Bifocals
Most patients adapt within a few days. Understanding what to expect makes the transition significantly easier.
Head position adjustment. You'll consciously lower your chin slightly to bring the near segment into your line of sight for reading.
The segment line becomes less noticeable. Your brain begins to discount it in peripheral vision, as it does with any familiar object.
Full adaptation for most patients. The glasses feel completely natural and the segment is no longer consciously noticed.
Image jump — and why D-seg minimises it
Image jump is the slight visual shift you perceive as your eye crosses the segment boundary. The D-seg (flat-top) design places the optical centre of the segment close to its top edge, minimising this prismatic jump — a key reason why D-seg has replaced round-segment designs. Most patients barely notice it after the first day or two.
Safety on stairs. When descending stairs in the first few days, look through the upper distance portion — not down through the near segment. The near segment can blur step edges at stair distance. Use the handrail for the first week. This becomes habitual quickly.
Section 05
Who Benefits Most from Bifocals?
For certain lifestyles and visual demands, bifocals are the superior choice. The patients who benefit most are those who value a clear, unobstructed distance view above everything else.
Drivers
The full, undistorted upper distance zone is arguably safer than a varifocal. No need to hold your head at a precise angle — just look straight ahead.
Trades & Workshop
Joinery, engineering, mechanics — precise near vision for gauges and drawings with an unrestricted distance view of the work environment.
Outdoor Activities
Fishing, gardening, walking — clear distance vision for the environment, with near access for labels, maps or phone by simply looking down.
Reading-Dominant Lifestyles
For those whose primary needs are driving and reading — without significant computer use. The two-zone solution works perfectly.
Musicians
Reading sheet music at a specific stand distance, with distance vision for the conductor. The near segment can be set to an exact working distance.
Failed Varifocal Patients
5–10% of patients don't adapt to varifocals. For these patients, bifocals are not a compromise — they are the right clinical answer.
Section 06
Common Questions
Questions we hear most often about bifocal lenses.
Will people be able to see the line?
Will bifocals make me look old?
Can I use bifocals for the computer?
Can I drive safely in bifocals?
I failed to adapt to varifocals — will bifocals work for me?
Bifocal or Varifocal — Stewart Will Guide You
The right lens depends on your lifestyle and visual needs, not on what's most expensive. Book a consultation and we'll recommend the lens that genuinely suits you.