Substitutions and Contact Lens Patient Safety

by Courtney Dryer, OD

As eye care professionals, the eye health and vision of patients is our priority. Many patients are unaware of the adverse effects to eye health and vision that may result from improper substitution of one brand of contact lens for another. We must educate patients on our rational for lens selection for their specific ocular health and lifestyle.

In early 2022, the Department of Justice (DOJ) and Federal Trade Commission (FTC) announced that the government will collect $1.5 million in civil penalties and $2 million in consumer recompence from the online contact lens company, Vision Path Inc., doing business as Hubble contacts. The American Optometric Association (AOA) previously requested an investigation from the DOJ and repeatedly emphasized Hubble’s disregard for patient health and safety.

According to the ruling, Hubble violated the Fairness to Contact Lens Consumers Act and the FTC’s Contact Lens Rule by failing to verify contact lens prescriptions and substituting Hubble’s own brand of contacts for those prescribed by ECPs. Samuel Levine, the director of the FTC Bureau of Consumer Protection stated, “Hubble’s business model boosted its bottom line but created needless risk for its customers’ eye health.” (Healio)

Online retailers like Hubble make lens substitutions without consideration for adverse complications in lens wearers. All lenses are not created equal and should not be substituted without oversight by a trained ECP (Efron 2022).

Soft Contact Lens Considerations by ECPs

An ECP conducts a detailed patient history to best prescribe a contact lens. Lens properties to consider include (Sindt 2007) (Efron 2021) ocular physiology, refractive power, design, care solutions, and cost (Efron 2022). There is clear evidence, if any of the properties (except for back surface design) are changed, there may be adverse effects for the lens wearer. Substitution of one brand for another by a lens retailer, may lead to wearer dissatisfaction, lens dropout (Naroo 2012) and/or ocular complications (Efron 2022).

Edge Profile

Soft contact lenses typically have one of several edge profiles which impact both patient comfort and ocular health. A hydrogel lens with greater edge thickness has been found to move more than one with a thinner edge. Silicone hydrogel lenses with a thin, knife edge design are associated with improved comfort when compared to chisel or round designs but may result in conjunctival staining. Edge profile selection enhances patient comfort and if substituted can result in dissatisfaction and adverse ocular complications (Efron 2021).

Optical Design

There is significance variance in optical design between brands in toric and multifocal contact lenses. A substitution in a multifocal lens can significantly affect visual performance and patient satisfaction. The lens brand must be specified in a legal prescription to optimize the vision needs of the patient and cannot be safety assessed without a trial lens evaluation. In presbyopes, substitutions can lead to reduced safety for driving and increased fixation time.  If the optical design is inappropriately substituted, significant issues can occur including a reduction in safety, ocular discomfort, and a greater likelihood of lens dropout (Efron 2021).


If there are significant differences between the prescribed power and the substitution, the wearer’s vision and comfort could be compromised. Some reports indicate an association between myopic hydrogel lens wearers (-9.00DS or greater) and an increase in the incidence of corneal infiltrates and corneal neovascularization, a result of decreased oxygen to the peripheral cornea. Substitutions in lens power can also affect lens thickness and may lead to mechanical ocular surface complications or handling difficulties (Efron 2021).

Color (tint)

Colored tinted lenses have been shown to significantly increase ocular aberrations and decrease both optical quality and contrast sensitivity resulting in a decline in functional vision. In certain lighting conditions, patients report a reduction in vision which can be seen on assessment by observing the diameter of the pigment free zone of the lens vs. the diameter of the pupil in varying light levels.  Surface tints can increase surface roughness which may increase bacterial adhesion to the surface and generate an increased risk of developing microbial keratitis. Tinted lenses are desired by patients for cosmetic purposes and a substitution may not have the desired cosmetic effect (Efron 2021).

UV Protection

Though UV-blocking lenses are typically prescribed as an additional lens benefit, substitution of a non-UV blocking lens may be problematic for a patient who was prescribed UV lenses by the ECP specifically for an outdoor occupation or sport (Efron 2021).

Wearing Modality

The number of prescriptions written for overnight wear remains low due to a 10x greater risk of corneal infection. If a patient has a daily wear lens substituted for an overnight lens without proper instruction or precautions, they may overlook the signs and symptoms of sight-threatening ocular conditions (Efron 2021).

Replacement Frequency

Replacement frequency can affect the clinical performance of a lens. ECPs prescribe a specific modality to reduce or eliminate adverse ocular effects. Daily lenses are associated with greater patient compliance, less severe infections, lower likelihood of vision loss, and a lower rate of corneal infiltrative events. Reports also find decreased rates of corneal staining and papillary conjunctivitis with daily disposable contact lenses. Substitution of daily disposable lenses for reusable lenses can compromise ocular health and increase the lens wearers’ risk of developing corneal infiltrates.


Contact lens thickness is important for lens handling and oxygen transmissibility. Variations in thickness due to power differences can have an impact on both central and peripheral oxygen transmissibility particularly in high power plus and minus lenses.

Thicker lenses reduce oxygen transmissibility and are associated with increased bacterial binding to the epithelium, corneal vascularization, corneal swelling and reduced corneal sensitivity (Efron 2021). Thinner hydrogel lenses have greater initial comfort than thicker lenses on the eye (Nichols 2004). Inappropriate substitutions (thick for thin lens) for hydrogel lenses can result in reduced comfort, corneal hypoxia, and increased dropout rates (Sulley 2018).

Surface Treatment

Silicone hydrogel lenses have the surface treated or have internal agents within the material to make the lens more wettable for improved comfort. Depending on the surface treatment of the lens, the size and hydrophobic nature of certain solutions may interact resulting in corneal staining (Efron 2021).

Internal Wetting Agents

Internal wetting agents are associated with an increase in quality vision because of lens surface wettability. Multiple studies have confirmed a link between patient reported comfort and vision (Deic 2021). A reduction in the quality of vision results in a reduction in the lens comfort which may increase patient dissatisfaction and lens drop-out. The addition of internal wetting agents has improved comfort for both previously symptomatic wearers and in challenging environments (Efron 2021).

Patients report differences in comfort with varying surface properties and wetting agents. Lens substitution can lead to patient discomfort, poor vision, corneal complications (Efron 2021), and contact lens dropout (Pucker 2019).

Oxygen Permeability

There is a significant difference in oxygen permeability between hydrogels and silicone hydrogel lenses.  Silicone hydrogels, with increased oxygen permeability, have reduced the complications of overnight wear like microbial keratitis. Studies have yielded few differences in cases of corneal neovascularization between hydrogel and silicone hydrogel lenses; however corneal swelling due to overnight wear varies by individual. Patients with high prescriptions are at increased risk. Oxygen permeability may be most important in toric and multifocal lenses lens wearers with high prescriptions. Both types of lenses have thick zones that restrict oxygen to the ocular surface.

Substitution of a higher oxygen transmissibility lens for a lower oxygen transmissibility lens can result in corneal hypoxia and microbial keratitis if worn overnight (Efron 2021)

Water Content

The water content of a lens affects both corneal health and lens handling. Substitution of a high-water content lens for a low content lens could result in corneal hypoxia especially in hydrogel lenses. With hydrogel lenses, a high-water content lens will allow more oxygen to the cornea but may damage more easily. A high-water content lens may be more difficult to handle for patients with poor dexterity. They tend to be floppier and more difficult to insert. Improper substitution of a lens with a differing water content may lead to frustration in handling and discontinuation of contact lens wear (Efron 2021).


Silicone hydrogels have increased elasticity when compared to hydrogel lenses; however, there does not seem to be a difference in comfort. Complications such as superior epithelial arcuate lesions, mucin ball formation, and contact-lens induced papillary conjunctivitis have been reported and are speculated to be a result of the mechanics of silicone hydrogel lenses (Efron 2021). Substitution of lenses with a different modulus can lead to handling difficulties (Tranoudis 2004), discomfort, and mechanically induced ocular complications (Efron 2021).

Total Diameter

A change in total lens diameter is most likely to cause patient dissatisfaction when compared to all other contact lens properties. By decreasing the total diameter of the lens, the lens is made flatter, leading to more on-eye movement.  Looser fitting lenses are less comfortable (Fang 2021) and may be associated with increased bulbar and limbal hyperemia. Tighter lenses may cause peripheral corneal ulcers (Efron 2021).

Even if the diameter is initially similar, high water content hydrogel lenses have been shown to reduce in diameter after 1 day of wear. This effect can only be recognized by fitting and evaluating the lens on the eye. Substitutions in lens diameter may lead to unhappy lens wearers.

Back Optic Zone Radius

Changing the back optic zone radius of the lens can affect lens movement on the eye. Aflatter back optic zone radius results in a looser fitting lens. Looser fitting lenses increase lens discomfort and may be associated with inflammatory conditions like peripheral corneal ulcers.

For large changes, substitution of back optic zone radius can affect lens fitting characteristics, increase corneal complications, and decrease comfort (Efron 2021).

Back Surface Design

Substitution of lenses with differing back surface designs does not adversely affect the lens wearer (Efron 2021).

Patient Education

ECPs must educate our lens wearers if they are not compliant with purchasing the prescribed brand and lens modality, using the recommended care system, and replacing as instructed, their vision, comfort and ocular health may be adversely affected (Efron 2022).

"All contact lenses are not created equal."
-Nathan Efron

Only an ECP with full knowledge of contact lens properties and comprehensive knowledge of the patient including ocular characteristics, lifestyle, and expectations, should be prescribing contact lenses. The ECP alone can weigh the lens benefits against potential adverse effects and patient dissatisfaction.


Courtney Dryer is a 2011 graduate of SCO. She opened 4 Eyes Optometry in her hometown of Charlotte, NC in February of 2013. After 5 years, the practice name was changed to Autarchic Spec Shop to renew the practice's commitment to independent optometry. In addition to consulting with new graduate optometrists on start-up practices, she contributes regularly to New Grad Optometry and has guest blogged for Invision Magazine. The unique design of her boutique practice was featured in Women in Optometry. In 2015, Vision Monday named her a Rising Star, and one of the most influential women in optical.




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