Information about irregular cornea/astigmatism
Irregular Astigmatism is the most common form of irregular Cornea. Irregular astigmatism can be the result of an illness, an accident or eye surgery. Additional irruglarities may also be present due to Corneal scarring. These can cause major limitations in vision and lead to a reduced quality of life.
Causes of irregular cornea:
- Infectious diseases with corneal scars
- Extremely dry eyes combined with the “scrubbing” motion of the eyelids
- surgery, medical procedures (e.g. Cataract removal) or aesthetic reason (LASIK and PRK)
- Conjunctival degenerations such as Pterygium
Types of corneal surgery
- Myopia (LASIK surgery)
- Photorefractive keratectomy (PRK),
- corneal transplant or corneal grafting in Keratoconus , dystrophies, degeneration and scarring
- corneal transplant or Corneal grafting in severe cases of structural damage for the restoration of corneal integrity.
- Therapeutic transplantation (removal of infected corneal tissue)
Contact lenses for irregular cornea
Traditionally special RGP contact lenses are recommended as a first choice in case of irregular corneas after transplantation or grafting. Due to modern manufacturing technologies combined with advanced material technologies it is possible, now, to considere soft contact lenses as a viable alternative.
For example the classic RGP scleral lens which overlies only the conjunctiva to “bridge” the cornea entirely;
customized soft lenses can now be adjusted as well due to a nano-metric level. The made to measure lens-surface can modellise nearly all irregularities of cornea. With a high oxygen permeable material like silicone hydrogel the possibilities for greater patient satisfaction and improved clinical results cannot be ignored.
LASIK surgery – correction of visual acuity
The 95% success rate world wide for this surgical procedure is quite high. However this leaves a residual rate of 5% of patients with post operative problems.
Often sufferers complain about:
Halos, night blindness, dry eyes, foggy vision and poor visual acuity. These symptoms can be tackled by using eye drops or other medications, often in combination with glasses or contact lenses.
There may be other secondary effects after LASIK or similar procedures:
The cornea develops an irregular surface:
- Visual acuity decreases, astigmatism occurs
- Halos, foggy vision
- Need of reading glasses
- Desire to wear multifocal contact lenses
Glasses become an option, however patients who entered into LASIK surgery would probably want to avoid to wear glasses if possible. In this case a correction with multifocal contact lenses can show a better option.
The variety of different contact lenses on the international market is huge, but the difficulty is to find a lens suitable for a surgically treated cornea
SwissLens has taken this issue to heart, and it is now possible, with modern contact lens materials, to optimally correct a cornea which has undergone surgical laser treatment.
The “HydroMed” and “FlexMed” contact lens designs can offer both: good visual acuity and comfort – due to their back surface bicurve design, adjusted to take into account the central lasered corneal area.
Motivation for Lasik
The decision for laser treatment is often due to the problems that occur while wearing contact lenses or simply the desire to be independent from glasses and to see properly. If the patient is given good advice including the potential risks involved, the chances of success are high.
Potential problems with LASIK surgery
Unfortunately, like any other medical procedure, some laser surgery is unsuccessful, unexpected side effects can lead to unsatisfying visual results. For example vision can be affected by an irregular corneal surface, or because the patient was poorly adviced. Fortunately, this percentage is very small; however for those affected that’s of no of consolation.
Often, these corneal situations are very complex. An additional difficulty is the fact that the treatened area of the cornea has become strongly thin.
Choosing a contact lens with the correct geometry can restore or at least greatly improve the vision.
When do I need post-LASIK contact lenses?
LASIK and other eye laser procedures involves the reshaping of the eyes natural refractive system by removing tissue from the anterior surface of the cornea. Occasionally this can lead to corneal irregularities, which can decrease the quality of vision compared to the vision the patient used to know with spectacles or contact lenses prior to the laser-treatment being carried out, for example, it may lead to a natural myopia, which then needs to be re-corrected.
This kind of myopia and other irregularities can be re-treated by follow-up-laser surgery. But if the cornea has become too thin for a second laser treatment, or there are other problems – the best choice would be to fit a contact lens to increase the quality of vision.
Special contact lenses designed to fit a post surgery cornea
During laser treatment, the central area of the cornea is irreversible flattened to dress the patient’s myopia. This leads to an important transformation of the corneal surface and consequently a greater challenge when fitting a contact lens compared to an eye with natural geometry.
Consequently regular contact lens geometries will not fit a post Lasik cornea and they cannot center properly. Also regular contact lenses fitted to a post Lasik cornea leads to unstable and blurred vision and patient discomfort.
In these cases it is recommended to choose a special post Lasik design (“HydroMed“) soft contact lens. The geometry of this new kind of design is significantly flatter in the center than in the periphery (its called reverse-geometry), and is suited to the corneal geometry found in Post Lasik patients
Special measuring instruments are recommended to determine exact “point-to-point” measurements of the post-operative anterior corneal surface to thereby define the best possible fitting geometry and correction. These measuring instruments, called corneal topographers, are used in clinics to measure the cornea before the operation takes place.
Presbyopia and LASIK?
What if the inevitable presbyopic prescription occurs?
The desire to see well without glasses always exists! From about 45 years of age, presbyopia becomes noticeable and you cannot avoid reading glasses. Multifocal contact lenses offer the possibility to read without glasses and to work on the computer without losing vision at longer distances.
General complications after laser treatments:
- Increased feeling of dry eye
- Degraded vision or halos at dusk or in darkness
- The affects of presbyopia always makes itself felt, and must be corrected at about 45 years of age. Therefore a laser treatment at an age of around 35 years has to be considered!
Normally, a keratoplasty (PKP) takes place in a late stage of keratokonus. As well as in case of high corneal irregularities or after infects, when there are no more options to correct visual acuity – only by transplantation of a new cornea.
During such operations it is very difficult to fix the graft on the remaining cornea leaving no residual vision errors, particularly irregular astigmatism. Therefore these patients could well benefit from a contact lens to improve their vision.
Irregular astigmatism is where the principal meridians are not perpendicular. It is often caused by an illness, an accident or an eye operation. In most cases, scarring on the cornea is an additional aspect that leads to the irregularity. The condition can lead to major limitations in vision, effecting daily work and a general reduced quality of life.
Causes of an irregular cornea:
- Infectious diseases with corneal scarring
- Injuries with scarring of the cornea
- Extremely dry eyes with “Scouring” the eyelids
- Surgical procedures, medically induced (e.g. keratoplasty for keratoconus) or aesthetic surgery (for example LASIK)
- Conjunctival degenerations such as Pterygium
LASIK, keratoplasty, and irregular cornea
Rigid gas permeable contact lenses have been traditionally used on Irregular Corneas after LASIK and especially after keratoplasty procedures. With the advent of new advanced manufacturing technologies customised soft lenses can now be lathe cut to accommodate corneal shape and corneal irregularities resulting in an optimal fit across the entire corneal surface.
SwissLens has developed the innovative “HydroMed” soft lens with a bi-curve or tri-curve back surface option. This allows an excellent fit, avoiding pressure on any part of the anterior corneal surface promoting comfort and potentially longer wearing times. These lenses are made in high permeable materials such as Silicone Hydrogel allowing an optimal supply of oxygen.
- HydroMed S1S: Soft contact lenses for post LASIK care
- HydroMed P S1S: Soft contact lenses for post LASIK care and correction of presbyopia
- HydroMed S2S: soft contact lenses for care of the irregular cornea and post-Keratoplasty
- HydroMed S2S: soft contact lenses for care of the irregular cornea and post Keratoplasty and the correction of presbyopia
SwissLens offer the following rigid gas-permeable contact lenses: