GP insights

GP Lens Fitting Made Simple

GP insights
GP Lens Fitting Made Simple


Fitting GP contact lenses diagnostically has traditionally represented the gold standard by which established contact lens fitters have approached the GP fitting process. It allows us to assess the lens-to-cornea fitting relationship and make changes, if necessary. It also often allows patients to experience more confidence about their ultimate success as a result of the time taken to achieve an optimum fit.

Go Empirical for Spherical

Without a doubt, using diagnostic lenses is especially important when fitting specialty designs in which you may need several lenses to achieve an optimum fit and for which material costs are higher. However, today it's important to understand the competition.

Silicone hydrogel lenses and disposable soft torics have provided healthier options to patients than their predecessors. We need to simplify the GP fitting process today and optimize patients' initial GP lens experiences, and empirical fitting can help us do that.

Whenever possible, the first GP lens a patient wears must be in his prescription so he can immediately experience the most powerful benefit of GP lenses: excellent quality of vision. This "wow factor" offers tremendous motivation during adaptation and makes other factors -- especially initial awareness -- less apparent.

Newer lathes and polishing methods have improved the manufacturing quality of today's GP lenses, producing consistent edges, ultrathin profiles and aspheric or pseudoaspheric peripheries. Therefore, although I've always believed -- as do so many established GP fitters -- that an important benefit of GP lenses is their custom nature, this benefit doesn't extend to spherical GP designs today. Determining edge lift values, peripheral curve radii and widths as well as center and lenticular junction thickness is important, but doing so represents a negative attribute to practitioners who prefer a "soft lens-like," simpler approach to lens design and fitting.

Ordering a patient's spherical lenses empirically simply makes more sense than applying a diagnostic lens that's not close to his prescription and deprives him of the "wow factor." Of course, you may need to make lens changes because the first pair that you dispense to the patient essentially serves as his diagnostic lenses.

The Best of Both Methods

Keeping in mind what we just discussed, consider using an inventory fitting approach that enables you to fit most patients directly from the inventory as well as to immediately make any lens changes to improve vision or fitting relationship. This approach provides the best of both worlds: good initial quality of vision and the ability to optimize the fit at the initial visit. Several Contact Lens Manufacturers Association member laboratories offer this option, via various plans, to interested practitioners.

A new design with great potential is the Naturalens Dispensing Inventory System from Key Distributed Products International ( This 120-lens system features a relatively large lens diameter (10.3mm) with a unique inverse curve periphery. Standard overall diameter, center thickness and peripheral systems will prove successful for most myopic patients, so you can inventory these lenses in low to moderate myopic powers, with base curves in 0.50D steps and one diameter. Such an inventory allows us to fit GP lenses in a manner similar to soft lenses, while providing better vision.

Offer Your Patients the Best

GP lenses are not specialty designs, despite efforts to categorize them as such. They are mainstream lenses, and most patients would benefit from the opportunity to experience the quality of vision they provide.

Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and is executive director of the GP Lens Institute.