Contact lenses

Contact lenses work following the same principle as glasses: the right convergence of light rays on the retina is re-established in order to have a clear image of what you’re looking at.

Contact lenses’s advantages are mainly three:

  • Unchanged visual appearance 
  • Re-establish your natural line of sight enabling you  to carry out any activities while correcting visual defects
  • Contact lenses can be worn at any age: the contactologist needs to check in any case whether the lenses ensure an optimal visual correction and the oxygenation of the cornea.

    It is essential to include a brief settling period, other than adequately instructing the patient on the right use and on the maintenance of the lenses. In order to comfortably use contact lenses it is needed to have a fair tear secretion that lubricates and moisturises the lenses thereby  reducing the friction between the eyelid, the lens and the eye, keeping constant over time the chemical and physical characteristics of the lenses, mainly the soft ones.

    Every eye lens (LAC) wearer needs to be advised and directed towards the most suitable contact lenses as ideal as possible to their needs and expectations.

    Therefore it is fundamental to contact a specialist in contact lenses with a proven knowledge of the material used and any issues that may occur. Other than choosing the most suitable lenses, the specialist in contact lenses will also advise a possible visit to the ophthalmologist if the LAC starts to compromise eye health.

    Nowadays on the market it is possible to find several types of LAC. The main difference between each one of them lies in the time of usage, the material and the geometry (curvature and diameter).

    In general there are two different types of contact lenses materials : rigid and soft lenses

    • Rigid lenses  ensure the eye oxygenation even if used for a long time, however the lacrimation is  limited and have the flaw of being sensed by the eye
    • Soft lenses are thinner and the oxygenation depends on the hydration of the lenses and the material used.

rigid eye contact lenses (rigid, gas permeable)

Amongst rigid lenses two different types stand out, one is the result of the other.

The first ones are the so-called rigid lenses PMMA.

The PMMA is the polymer of the methyl methacrylate, which was used in the 40’ and is also known as Perspex. It is a stable and inert  material which has a waterproof surface if untreated and it is also impermeable to oxygen.

The second ones are the so-called LAC RGP, the most recent innovation in the rigid LAC field, they retain a low absorption to liquids and are permeable to oxygen.

At Ranieri opticians it is possible to find the best materials on the market for rigid gas permeable LAC.

The continuous development of contactology, oriented towards new polymers, geometries and innovative surface treatments, enables to increase the comfort and time of use.

A wide range of traditional geometries, multi-curves, aspheric spheres and aspheric which can be associated with the material more suitable to each case. 

The lens back surface can be made with two different curvatures ( Toric lenses) which improves the alignment of the lenses with the corneal surface and it also improves the astigmatism compensation. 

To these kinds the most advanced devices are bound:

  • Progressive external profiles
  • Aberration compensation modules

Rigid contact lenses are used particularly to correct pathology-induced ametropias like the KERATOCONUS. 

The rigid lens represents the only visual device that enables the patient affected by keratoconus to get back a satisfying vision, delaying as much as possible corneal transplant surgery. 

soft contact lenses

Are made of hydrophilic plastics that are able to bond with water molecules. The hydration of the soft contact lenses can go from 25% to 80%. Soft contact lenses are divided into lenses with a low percentage of water (under 50%) and lenses with a high percentage of water (above 50%) with a respective gas permeability.

Using a hydrogel  LAC, picking the right material has a significant importance. 

It is essential to make the right choice:

  • Define the corrective needs and the portability requirement
  • Evaluate the ocular morphology 
  • Evaluate the precorneal tear film

There is a wide range of geometries , spherical, ellipticals, all of them are customizable. Moreover there is the range of astigmatism lenses, internal and external toric lenses, characterised by advanced stabilisation systems.

To all the customizable lenses it is possible to associate to the several geometries the best polymer to fulfil the need of each one of them, paying rigorous attention to the delicate balance of the tissue and the corneal metabolism.

Apart from customizable lenses there are also disposable ones:

  • Soft lenses with frequent replacement (Lac disposable): their use is steadily increasing as they require less thorough maintenance and can have a monthly duration or can last two weeks; Nowadays the monthly lenses are the more advanced frequent replacement lenses, they are composed of:
    • Silicone hydrogel with high oxygen delivery and low dehydration.
    •  Phosphorylcholine (natural phospholipide found in cell membranes and used to give a cell-like biocompatibility  to the material in which it is integrated).
  • Daily disposable lenses: are very convenient as they require relative care, given they are thrown away after the 24 hours of use. Daily disposable lenses are the most used and the most comfortable and are also a great adjunct to the use of glasses to do particular activities like a sport. Nowadays Daily disposable lenses have new formulations to reduce distraction and integrated UV filter