Delta Bifocal | Custom fit contact lens
The Delta bifocal is a modern equivalent of a tangent streak bifocal. This can provide patients with single vision quality distance vision and on downgaze built in reading glasses vision! The Delta segment is adjustable on both position and angle and is available as spherical and bi-toric using the CC back surface for ease of fitting and patient satisfaction.
Ordering by specification based on Initial Trial Lens Parameters below or supplying spectacle Rx, BVD and Ks will generally provide an optimal fitting lens. Trial lens sets are available for spherical BOZR range.
- For new wearers instil anaesthetic to stabilise lens fit and optimise initial patient experience.
- Assess lens fit with fluorescein and yellow filter at slip lamp.
- With toric lenses note flat axis marks (- -) rotation.
In an optimum fit lenses will move post blink vertically. Toric lenses will also appear as pictured. A lens that rides high and does not move with the lid is a high riding fit. This is usually due to lid interaction and corneal shape, altering the lens will not centre high riding lenses. Some lenses will drop and not move, especially high plus powers, reducing the lens diameter 0.5mm will reduce the weight and thickness of the lens. Low riding lens fits can be tolerated, increase the diameter if the pupil is not covered.
Delta Initial Trial Lens Parameters
|0.00 to 1.75 D Cyl
Ks differ up to 0.35rd
|Base Curve 0.1mm steeper than flat K Corneoscleral||Power -0.50 more than spec Rx sphere|
|Over 2.00 D Cyl
Ks differ 0.40 or more
|KFLAT BOZR -0.05mm
KSTEEP BOZR +0.05mm
|PowerFLAT -0.25 more than spec Rx
PowerSTEEP +0.25 more than spec Rx
Spectacle Rx should be minus cyl form. Correct for BVD is spec Rx is over +4.50