RGP Contact Lenses
Typically used in hospital contact lenses clinics for most irregular cornea conditions, RGP lenses typically provide excellent vision, are easy to handle and have low risk of infection.
They are also a cost effective option. Due to these reasons they are still widely used in the field of irregular cornea fitting. However they do have their downsides, including poor initial comfort, they can be prone to falling out for some people, and for very irregular eyes there are times when they just won’t fit. However they remain a very useful tool in the arsenal of a specialist contact lens fitter.
Soft Contact Lenses
Soft contact lenses are larger than RGP lenses, typically 14-15mm diameter. They are made from special plastics with water added to make them gel-like, with some also containing silicone which makes them more breathable.
They can be disposable (either disposed of daily, fortnightly or monthly), or custom made for an individual’s eye (typically replaced every 3, 6 or 12 months). Where RGP lenses are stiff and inflexible, soft lenses are squishy and floppy and will drape over the cornea.
This typically makes them less suitable for correcting irregular corneas, as instead of masking the irregularity they conform to the cornea’s distorted shape. However, in cases of simple high prescriptions, mild keratoconus or regular corneal grafts, normal disposable lenses can often work quite well. In more severe cases or when the prescription is out of the ‘normal range’, custom lenses will need to be used.
- Kerasoft range – these custom-made soft lenses are specifically designed for irregular corneas such as with keratoconus and corneal grafts, and can work well for mild-moderate cases and when RGP lenses are not well tolerated.
- Proclear Tailor-Made – these are lenses designed for ‘normal’ corneas, and come in a range of high prescriptions.
- Cosmetic lenses – when eyes are left scarred from infection, trauma or corneal or auto-immune disease, a person may choose to have cosmetic soft lenses fitted which can mask or completely hide the area, improving the cosmetic appearance of the eye.
Piggyback Contact Lenses
‘Piggybacking’ refers to when an RGP lens is worn on top of a soft lens, in the same eye.
Typically, a soft disposable lens is inserted which has little or no power and acts merely as a cushion for the RGP lens, which is placed on top of the soft lens.
This is usually done for the following reasons:
- When an RGP lens is already being worn but rubbing the cornea, causing scarring or discomfort. The soft lens acts as a bandage and stops the rubbing
- When RGPs are already being worn but the wearer lives or works somewhere dusty The soft lens prevents dust particles getting under the lens and irritating the eye
- If the cornea has extreme surface irregularities (imagine corrugated iron sheeting), the soft lens can help smooth out the surface of the cornea so that the RGP will sit better on the eye.
Downsides are the added time taken to put in and remove two lenses per eye instead of one; the added cost of the soft lenses; when two lenses are worn less oxygen will reach the cornea so the wearing time of the lenses is reduced.
SynergEyes Hybrid Contact Lenses
In 2004, a bright spark in California had the clever idea of taking the benefits of piggybacking and turning it to one lens, with an RGP centre and a soft skirt attached. This has the dual benefit of excellent RGP optics centrally providing sharp vision, with a soft skirt to provide comfort and stability. There are now 8 designs in the SynergEyes family of lenses, with a lens to fit almost any eye shape. They are particularly suited for keratoconic eyes.
Designs include ClearKone, Duette and the new UltraHealth high oxygen design for keratoconus.
Sophie has been fortunate enough to twice visit the SynergEyes headquarters in Carlsbad, California to undergo specialist training on these lenses and she was the first practitioner to fit them in the UK. Sophie has been involved in the introduction of SynergEyes lenses to the UK and have delivered training to other Optometrists on their use.
SoClear Corneoscleral Contact Lenses
SoClear lenses are known as a ‘corneoscleral’ contact lens. This means that they rest partly on the cornea and partly on the sclera. They are made from a very breathable RGP material, but are larger than a standard RGP lens, at around 14mm. This may seem large, but actually it’s only the same size as a soft lens (as you can see in the image shown). Because they are made from a rigid lens material they provide excellent optics and very clear vision. The size of the lens makes them very stable on the eye, with minimal movement. They are also extremely comfortable.
SoClear lenses are an excellent option for patients with very flat corneas following refractive surgery as they can be manufactured with flat curves centrally and a normal shape in the periphery (known as ‘reverse curve geometry), to fit the eye shape perfectly. The large optics help reduce flare/glare/halos for people with aberrations caused by having a small lasered treatment zone and large pupils. SoClears can also work beautifully for people with high prescriptions and astigmatism and there is a SoClear Multifocal design which can work well for people who need reading glasses. There is also a Keratoconus design.
- Profile 14 and Profile 16
- Rose K2 XL
Scleral Contact Lenses
Scleral contact lenses are large diameter lenses (generally between 16-23mm diameter) which vault the cornea entirely, and rest on the sclera, the white part of the eye. They are an excellent choice for patients with a very steep, asymmetric, irregular or dry cornea and when a regular RGP lens is too unstable, uncomfortable, or won’t stay in the eye.
Because scleral lenses are large and they do not move, they are very comfortable indeed. They are a particularly good option for people with an irregular or steep corneal graft or very advanced keratoconus. Or in fact anyone who needs a comfortable lens!
The space between the lens and the eye is filled with saline, so there is no friction whatsoever on the corneal surface. This makes scleral lens types the first choice option for patients with severe dry eye disease, or those who cannot tolerate any corneal touch due to a fragile epithelium (corneal surface).
If you have tried lots of different lens types with little success, these may be the lenses for you!
- ICD Mini-Scleral
- Innovative Sclerals
- Maxim CV