Why Do New Contact Lenses Require Examination?

Why Do New Contact Lenses Require Examination?

by Brian Chou, OD, FAAO, FSLS

  • July 20, 2023

In the US, disposable contact lenses are Class II medical devices which require a prescription for purchase. Nonetheless, contact lens manufacturers market them directly to consumers as if no prescription is required. Despite the misleading suggestion that contact lenses are a do-it-yourself purchase, your doctor has a responsibility to prescribe contact lenses that are safe, comfortable, and correct vision.

Switching Contact Lens Types

Consumers often mistakenly believe that switching from one type of disposable contact lens to another is just about a new lens type with the same power specifications. This often is not the case. The contact lens power to achieve similar visual performance can significantly differ from one line of lenses to another — particularly for contacts addressing astigmatism or presbyopia.

Soft disposable contact lenses for astigmatism are rotationally stabilized on the eye for the best vision. The lens stabilization strategy is different from one type of contact lens to another. For example, the CooperVision Biofinity Toric contact lens uses what’s called a “uniform horizontal ISO thickness and wide ballast band”. By comparison, the Alcon DAILIES AquaComfort Plus Toric contact lens uses dual thin zones where blinking pressure of the upper and lower eyelids facilitates rotational stability. In other words, a Biofinity Toric and Alcon DAILIES AquaComfort Plus Toric contact lens can give very different visual outcomes on the same eye since the lens rotational position depends on how the lens design interacts with the eye. Professional evaluation of diagnostic contact lenses on the eye allows the practitioner to determine if compensations in lens rotation is needed to enhance vision for a particular lens type.

Similarly, multifocal contact lenses for presbyopia each have proprietary optical designs which do not translate from one to another. Some disposable multifocal contact lenses have reading power in the center whereas other designs have reading power in the periphery. This means that a +1.00 add power in one multifocal contact lens is not the same as a +1.00 add power in another multifocal lens.

The Cost of Contact Lens Evaluation and Prescribing

As you might expect, the cost of contact lens service increases in lockstep with the amount of time you spend in the exam chair. If you are on a wild goose chase to try six different soft disposable contact lenses for astigmatism, expect to incur a lot more expense related to the required professional time. For the majority of patients, you are best to accept your doctor’s experience and familiarity of what will bring you the best results in an efficient and cost-effective manner.

To make your contact lens services efficient and to minimize associated costs, your eye doctor needs to know the exact specifications of the contact lenses evaluated on your eyes. That is why if you are a new patient, it helps if you bring to examination the labeled blister packs or boxes corresponding to the contacts on your eyes. Otherwise, your doctor may apply new diagnostic contact lenses on your eyes to evaluate. Due to the inventory management of diagnostic lenses by staff, expect to incur some cost related to the time to replenish the lenses consumed.


ReVision Optometry is a referral-based practice in San Diego providing scleral contact lens services for patients with keratoconus and other complex eye conditions. To schedule an appointment, request your examination online or call our office at 619.299.6064.