Contact lenses are an ever-evolving field with advancements in science and technology leading to newer materials and designs. Contact lenses serve as a mode of correction for refractive errors such as hyperopia (farsightedness), myopia (short-sightedness), astigmatism and presbyopia.
Most refractive errors can be corrected by regular or conventional contact lenses available in the market. However, few corneal conditions or eye conditions wherein the traditional contact lenses do not fit or suit them need speciality contact lenses.
The right speciality contact lens ensures vision and comfort, and safety for the eye. This article covers the need for speciality contact lenses and the types available.
What are speciality contact lenses?
These are contact lenses that are custom designed and made for a particular eye after a thorough examination and fitting trial done by a contact lens practitioner. Speciality contact lenses come in various materials and designs. They cannot be prescribed without a proper contact lens trial and examination to finalize the lens.
What are the materials available in speciality contact lenses?
Speciality contact lenses are available in several materials like soft (hydrogel and silicone hydrogel), rigid gas permeable (corneal, corneo-scleral and scleral) as well as hybrid (combination of soft and rigid gas permeable) materials.
Who requires speciality contact lenses?
Anybody with a refractive or corneal condition in which the regular contact lenses cannot provide optimum vision correction is a candidate for speciality contact lenses. Only after a contact lens examination and trial by a contact lens practitioner will the suitability of the contact lens be decided.
Eye conditions requiring speciality contact lenses
• High refractive errors in which regular contact lenses cannot fit
• High astigmatism (cylindrical correction)
• Irregular corneal conditions like Keratoconus, Pellucid marginal degeneration etc
• Refractive errors with dry eyes
• Scarring of the cornea due to congenital condition or injury
• Post-surgical distortion of the cornea like LASIK, DALK, post graft etc
• Contact lens intolerance
Are speciality contact lenses readymade?
Unlike the regular, soft lenses that are readymade and dispensed easily, speciality contact lenses are not readily available. Each speciality contact lens is custom ordered for every eye. This is done after thorough contact lens examination and trial fitting before being ordered, so these lenses are not available off the shelf. Only a contact lens practitioner is trained and experienced to fit and dispense these lenses.
Why are speciality lenses more expensive than regular lenses?
Unlike regular contact lenses, which are mass-produced and sold in the market, each speciality lens is tailor-made for every patient and every eye. The material and manufacturing process and the design are specific for the eye condition. They are never mass-produced, hence the cost.
Speciality contact lens trial also takes more chair time than regular contact lens trials. It involves the knowledge and experience of the contact lens practitioner.
Types of speciality contact lenses
Soft lenses
These lenses are made from a soft, pliable material that conforms to the shape of the cornea. These lenses are larger than the cornea and comfortable to wear, and easier to adapt. They allow oxygen to pass through them and reach the cornea.
Soft lenses are available in hydrogel and silicone hydrogel materials. Soft lenses are prescribed for correcting various refractive errors like hyperopia (farsightedness), myopia (short-sightedness), astigmatism (cylindrical power) and presbyopia.
With advancements in the contact lens field, soft lenses are also available for fitting in several corneal conditions where regular soft lenses cannot provide vision and comfort. These may include keratoconus, pellucid marginal degeneration, high cylindrical corrections etc.
Rigid Gas Permeable (RGP) lenses
These lenses are made up of rigid gas permeable materials and offer more durability and sharper vision than soft lenses and the lenses of choice for most eye conditions in which soft contact lenses do not provide quality and quantity of vision.
Several types of RGP lenses and designs are available, and their suitability depends upon the eye and its condition. It can be decided only by a contact lens practitioner after a thorough examination and trial.
Types of RGP lenses:
Corneal RGP lenses: These are small diameter rigid gas permeable lenses that are smaller than the size of the cornea. These lenses float over the tears in front of the cornea and move with each blink.
Corneo-scleral RGP lenses: These are rigid gas permeable lens designs that are slightly larger than the cornea. These lenses sit over the cornea and extend towards the white portion (sclera) of the eye hence the name. They do not move as much as corneal RGP lenses.
Scleral RGP lenses: These are large diameter rigid gas permeable lens designs used for eye conditions in which corneal and corneo-scleral lens designs do not provide optimum vision correction/fitting.
These lenses do not sit on the cornea rather vault over the cornea and rest on the sclera (white portion of the eye) hence the name. There is a fluid reservoir between the lens and the cornea and is the preferred lens of choice for highly irregular corneal conditions and dry eyes. These lenses do not move, unlike the corneal and corneoscleral RGP lenses.
Hybrid lenses
These are unique lenses and are a combination of both rigid gas permeable and soft lens material. The centre of the lens is made with a rigid gas permeable material, while the edges of the lens are made with soft lens material. These lenses offer benefits of RGP as well as soft lens materials. Suitability for these lenses is decided after a thorough examination by the contact lens practitioner.
Orthokeratology lenses
These lenses are special lenses worn during the night (overnight) and offer spectacle /contact lens-free vision during the day. These lenses gently reshape the cornea overnight, thus providing clear vision without any aid during the day.
Ortho K lenses have certain limitations for vision correction. The contact lens practitioner can decide suitability for these lenses only after a careful and comprehensive eye examination. The orthokeratology lenses are usually made up of rigid gas permeable materials.
Orthokeratology is used for the correction of refractive errors such as myopia (short-sightedness), hyperopia (long-sightedness), astigmatism (cylindrical correction) and presbyopia. These lenses are also used myopia control devices in children.
Do speciality contact lenses require special care and maintenance?
All contact lenses require special care and maintenance as these devices sit so close to the eye. Improper or lack of care and maintenance could lead to infections or severe complications in the eye.
Hygiene is an essential factor for the care and maintenance of contact lenses and should be maintained at all times. The lenses and the lens cases have to be cleaned and replaced periodically as per the advice of the contact lens practitioner. Follow up visits are a critical part of any contact lens wear. These visits help determine the condition of eye health with contact lens wear and the status of the contact lenses.
The insertion, removal, and care and maintenance of contact lenses differ depending upon the type and design of the contact lenses and should be strictly adhered to as per the advice of the contact lens practitioner.
Scheduling an appointment with a contact lens practitioner is very important as he/she will decide on the suitability of contact lenses and help determine the correct type of contact lens based on the eye condition and not compromise on the eye health.