Essential Xtra Fitting Guide

Lenses>SpecialtyGP>Multifocal> ESSentialXtraGP>Fitting Guide

Parameter Selection:

1. Initial Base Curve/Diameter Selection

Select initial base curve according to the base curve selection chart.

Select diameter according to diameter selection chart.

Base Curve Selection Chart
Select base curve according to corneal cylinder
Determine Flat K	0.00D to 0.62D	0.75D and UP
40.00 to 40.37	8.30	8.20
40.50 to 40.87	8.20	8.10
41.00 to 41.37	8.10	8.00
41.50 to 41.87	8.00	7.90
42.00 to 42.37	7.90	7.80
42.50 to 43.00	7.80	7.70
43.12 to 43.62	7.70	7.60
43.75 to 44.25	7.60	7.50
44.37 to 44.87	7.50	7.40
45.00 to 45.50	7.40	7.30
45.62 to 46.12	7.30	7.20
46.25 to 46.75	7.20	7.10
46.87 to 47.37	7.10	7.00

Diameter selection chart
Select diameter according to corneal cylinder
Base curve	Myopes	Hyperopes
< 7.30mm	9.2mm	9.5mm
7.40 to 7.90mm	9.5mm	9.5mm
>8.00mm	9.5mm	9.7mm

2. Add Series Selection

Select add series according to patient's add
Patient's Add	Add series
+0.50 to +1.50	Series 1
+1.75 to +2.25	Series 2
+2.50 and up	Series 3

3. Lens Position and Movement

Evaluate lens position and movement; the ideal fit will be superior central (upper lid attachment) with a fluorescein pattern that demonstrates alignment along the flattest corneal meridian. Make base curve and diameter changes accordingly (see Troubleshooting guide).

4. Lens Power

Perform your over-refraction with loose trial lenses to determine the final distance Rx. Expect final Rx to be -0.50 D more than the existing contact lens Rx. Place the over-refraction in a trial frame and evaluate the transition from distance to near vision. If the over-refraction leads to acceptable distance but unacceptable near vision, reassess your base curve and/or add selection.

Important Note: In order to maximize the ADD available in each series, the lens needs to translate upward along the vertical corneal meridian as the patient looks from distance to reading tasks. An upper lid attachment will facilitate the upward transition of the lens.

Troubleshooting Guide

Clinical Observations	Common Symptoms	Fitting Goal	Remedy
High-Riding Lens	Excellent near, Excessive minus Over-refraction to achieve good distance.	Lower the lens to pick up more distance power in the center of the lens.	Steepen B.C. by 0.10mm and specify a thin edge design And/Or Reduce lens diameter by 0.3mm, and specify a thin edge design Last Alternative Steepen B.C. by 0.10, reduce diameter by 0.3mm, specify a thin edge design and increase the lens center thickness by 0.05mm
Lens Rides Temporally	Near is usually excellent, distance requires additional -0.50D to -0.75D.	Get lens to center more by changing the dynamics between the upper lid and the lens.	Diameter < 9.3mm Increase lens diameter by 0.50mm and specify a minus carrier. Diameter>9.3mm Increase lens diameter by 0.3m and specify a minus carrier
Low-riding lens	Good to excellent distance, near almost non-existent.	Need to achieve an upper lid attachment, making the greater plus power on the periphery of the lens available for near tasks.	Diameter < 9.3mm Increase lens diameter by 0.5mm and specify a minus carrier Diameter>9.3mm Increase lens diameter by 0.3mm and specify a minus carrier Last Alternative Flatten B.C. by 0.10mm (only if the fit allows to do so).
Lens that centers	Excellent distance, reading difficult	Get the lens to translate upward upon downward gaze.	Increase lens diameter by 0.3mm and specify a minus carrier.
Lens Rides Nasally	Distance is difficult and near vision is almost non-existent.	Get the lens to center more, by changing the dynamics between the upper lid and the lens.	Diameter < 9.3mm Increase lens diameter by 0.50mm and specify a minus carrier Diameter>9.3mm Increase lens diameter by 0.30mm and specify a minus carrier.