A Decentered Near Zone for

Insufficient Performance with

Conventional Multifocals 

Bernd Brückner

- Optometrist, MSc in Vision Science and Business, Switzerland -  

Introduction

Going forward, developments such as this - customizing multifocal soft lenses to the needs and the anatomy of individual patients -  could help to decrease the massive dropout rate that happens around presbyopic age in the contact lens population.  

This article describes the fitting procedure of soft concentric multifocal contact lenses (CLs) with decentered optical zones for near vision correction in cases of pupil and/or contact lens displacement. 

For several years, the demographics of western societies have been changing, as has been well reported in the daily press: basically, the proportion of older people in the total population is increasing. Due to this demographic development, it is foreseeable that one of the future challenges – and opportunities - in the field of contact lens fitting is the supply of the presbyopic population with effective multifocal CL systems.

It is interesting to note that while the demand for visual correction increases with age, the proportion of CL wearers in the non-presbyopic age group is higher compared to that in the presbyopic age group. We often observe that existing and quite satisfied CL wearers switch back to glasses either at the onset of or with the increase in presbyopia. The reasons for this are certainly not in the motivation of the patients or in the expertise of the practitioners; rather, they are in the setup and functioning of the existing multifocal systems.

However, it is our strong belief that lens wearers who become presbyopic can continue to wear contact lenses, with new products continually becoming available and if the right technology is used.

Case report

This patient has been a satisfied soft lens wearer for 35 years. Because of developing presbyopia, he had a need for soft multifocal contact lenses. The patient rejected the correction of his presbyopia with reading glasses over his existing single vision lenses.

An initial external multifocal contact lens fitting failed due to poor lens performance. The next fitting of soft multifocal CLs with near-center optics resulted in a loss of both distance and near visual acuity and also reduced high-contrast acuity. All previous approaches such as optimization of the zone diameter, change from centrally located near optics to distance-center optics and vice versa did not provide a satisfactory improvement in the patient’s vision.

The reason for this is that his pupils are nasally displaced within the iris in both eyes (Figure 1) in conjunction with temporally displaced contact lenses. This results in inadequate coverage of the pupil by the central optical zone (Figure 2). 

To solve this problem, we used soft concentric multifocal CLs with a decentered central near zone. Based on the diameter of the central zone engraving of the trial lenses (Figure 2), it was possible to digitally measure the necessary decentration distance and the angle of the decentration.

The best experiences that we have had with such decentered near zones have been in cases in which the near zone centered nasal-inferior to the pupil. With such contact lenses, the patient in this case report obtained excellent vision for all distances.

Conclusion & Closing Remarks

In our experience, the ability to decenter the near and distance zones of a soft multifocal contact lens is a great way to enhance visual performance in presbyopes, especially in cases in which the patient complains of double vision or shadow vision in the distance and/or for near. In such cases, it may be advisable to use trial lenses that have an engraved center circle as a functional check for the determination of the necessary decentration in distance and axis.

In this case, in multifocal systems with center-near designs, the near zone should not be decentered directly over the pupillary center, but rather it should be nasal-inferior to the pupil. Thus, the distance vision is only slightly impaired. When the patient looks up close - triggered by infraduction and convergence – a lens that has sufficient movement and mobility will locate the near zone over the pupil center. In the case of multifocal systems with a center-distance design, however, the decentration of the distance zone should be located directly over the pupillary center.

Bernd Brückner - MSc Vision Science and Business and Optometrist – is the co-owner and head of professional services at Appenzeller Kontaktlinsen, Speicher – Switzerland.

He is customer relationship manager and is responsible for the consultation of optometrists and ophthalmologists fitting lenses. Bernd Brückner drives the product research at the company and manages seminars and product training.