For a lot of practitioners, the gold standard for correcting Keratoconus was a rigid gas permeable lens for decades. But with improvements of materials and research, you will learn in this article what option you have when soft contact lenses should are chosen to correct vision in combination with Keratoconus.
The contact lens whether it is soft or hard needs to compensate for the uneven corneal surface of an eye with keratoconus. When soft contact lenses this compensation can be handled with an increased lens thickness. A thicker lens will take less on the shape of the cornea than a normal soft contact lens would do which. The following parameters need to be changed in a soft contact lens when it should be used to correct keratoconus.
Customized Parameters for a soft keratoconus lens:
- Base Curve
- Diameter
- Material
- Lens power
- Size of optical zone
- Center thickness
- Lens design
Different Materials for a Soft Contact Lens in Combination With Keratoconus
In contrast to normal soft contact lenses, the choices for fitting different materials are bigger with soft contacts for keratoconus. When a normal contact lens does not work because of a dry eye for example the contact lens needs to be changed and with it the whole lens design. This is oftentimes not necessary as one lens design made for correcting keratoconus is oftentimes available in combination with different lens materials.
This gives the optician or optometrist more options to fine-tune the lens for your eye and the conditions you use the lens on a daily basis. When it comes to the choices of the materials some materials work better or worse in every individual case. The optician or optometrist will have a closer look at the eye for the first choice and during follow up care.
Modern SiHy lenses have eliminated hypoxia-related complications that some patients experienced when wearing low-Dk/t hydrogel normal lenses (Radford et al, 2009). The two most common clinical signs of hypoxia included limbal redness and vascularization.
However, normal contact lenses are much thinner than soft contact lenses for keratoconus. When the thickness is increased less oxygen will reach the cornea compared to a thinner lens. The characteristics also change when the contact lens dries out.
When the sponge-like material of a soft contact lens for keratoconus dries out the shape of the soft lens oftentimes changes. This is not good as a changed shape oftentimes leads to a lens that sits too tight on the eye.
In comparison to RGP or hard contact lens materials, you have the same shape of contact lens on your eye even when you sit in a room with an AC on all the time. This usually is a big benefit of RGPs because a lot of soft contact lenses would lead to imprints on the white part of the eye after the lens materials dry out.
What Is the Benefit of a Soft Keratoconus Lens?
The real benefit of a soft Keratoconus contact lens is the wearer can tolerate this type of lens a lot faster in comparison to a classic lens design for Keratoconus like the Rose K 2 KC. The difference here is classic Keratoconus lenses only cover a part of the cornea.
With a lens of this size, a lot of movement happens usually when the customer blinks or looks around. In a lot of cases, those smaller lenses will be tolerated in regards to the foreign body sensation but when not it is good to have other choices.
Oftentimes with very active people and sports where a ball is involved a smaller lens will not work really well because the person using the lens needs to tolerate the short lag of movement and the feeling of the lens when it moves.
Alternatives To Soft Keratoconus Lenses
In some cases, the person wearing a soft contact lens for keratoconus will still no tolerate the lens. What are the alternatives? They are listed here below:
- Scleral lenses (bigger hard contacts)
- Soft contact lens under your hard contact lens (piggyback system)
- Hybrid lens (hard contact lens center with a soft outer ring segment)
Contrary to the believe a bigger hard contact lens would lead to a stronger foreign body sensation scleral lenses which touch the white part of your eye usually produce hardly any foreign body sensations. The most important thing causing you to feel a lens is movement on the eye.
A bigger lens generally moves less up to not at all and produces therefore way less foreign body sensation and out of the experience with scleral lenses and Keratoconus they work great. Because they do not dry out as soft contacts tend to do.
The hybrid lenses are oftentimes a new thing too when I tell my customers about those lenses. They also get tolerated very fast by the wearer and are also great for keratoconus as they provide a hard center which usually delivers the best visual experience.
One option which oftentimes is tried immediately after the rigid gas permeable keratoconus lens can not be tolerated is the piggyback system. When the little hard contact lens produces just too many foreign body sensations it is possible to place a soft (usually a daily contact lens) first on the eye and then on top of that the hard contact lens is placed.
This reduces the motion of the contact lens on the eye a lot and is, therefore, a lot easier tolerated by customers in comparison to the normal wear of the little RGP lens.
Out of experience in fitting keratoconus lenses, I can tell there is not a single lens may it soft or hard for keratoconus that works every time. In some cases, the lens design needs to be switched. The best lens design individually is the one that feels good on your eye, provides great visual experiences, and does not any signs of insufficient supply of oxygen during the follow-up care.
When you do not feel comfortable with your current keratoconus lenses make an appointment with your contact lens specialist. He will take the time to for trough the options with you in your individual case and will be happy to help you out.
I wish you a great day.