What is Orthokeratology (Corneal Refractive Therapy)?
Orthokeratology, or OrthoK, involves use of specially designed rigid gas-permeable (RGP) contact lenses to alter the shape of the cornea in order to reduce or correct myopia (short-sight). It can also be effective with low degrees of certain types of astigmatism (when the front of the eye is rugby ball shaped). In the past 10 years new technology has become available to accurately scan the cornea and manufacture lenses that will achieve a controlled and precise reduction in the eye’s optical imperfection. In addition, new developments in lens materials have been made that enable safe overnight wear to be possible. The technique of OrthoK is now a safe, viable and reversible alternative to refractive surgery. The cornea, whilst being mouldable, always returns to its original shape if lens wear is stopped. For this reason lenses are worn nightly or alternate nights in order to retain the effect.
Why have OrthoK done?
The main purpose of OrthoK is to be free of both contact lenses and spectacles for all waking hours. The freedom from any artificial aid appeals to myopic spectacle and contact lens wearers and is ideal for sportsmen, those who work in dusty or dirty environments or people who find spectacles and conventional contact lenses inconvenient.
Possibly one of the ideal situations for using OrthoK is for the teenager with early myopia. Not only does it have all the advantages already given above, but the procedure appears to retard the progression of the myopia (this has not yet been scientifically proven however the research is promising.)
Is everyone suitable for OrthoK?
No. The procedure works best up to a maximum of 4.00 units of myopia and 2.00 units of regular astigmatism. In addition, there are several unknown factors for each individual; the complexity of the corneal shape and the response of the cornea itself. Thus the speed of corneal moulding from one individual to the next will vary. Whilst the success rate is very high, total success cannot be guaranteed due to these factors.
What does the initial trial involve?
The initial assessment appointment includes computerized corneal topographical scanning. This gives the practitioner a chance to assess both the general condition and health of the eyes and also determine the likely effect of the procedure in that individual. OrthoK contact lenses, made from highly oxygen permeable rigid material, are then fitted using the results of the corneal scan to gently reshape the cornea towards less curvature and a more spherical shape. These will be worn for an initial overnight trial and the response evaluated in the morning. The effect should be a reduction of the myopia and astigmatism with improvement in the unaided eyesight. The corneal health will be carefully evaluated to ensure that it is not compromised. Only when the patient demonstrates an excellent response to the OrthoK trial will the treatment program commence.
What does the treatment involve?
Once a patient has shown the appropriate response to a trial, they will start to wear lenses on a regular basis, typically overnight. For the first two to four weeks the vision may not be sufficiently good for all day-to-day activities. In these circumstances daily disposable soft lenses will be worn. After the first month, excellent vision and comfort are normally maintained whilst wearing OrthoK lenses overnight. Occasionally more than one set of lenses are required to effect the desired change.
As most of the visual changes occur rapidly in the first few weeks, fairly frequent examinations and possible lens changes may need to take place. Stabilisation procedures then follow at a slower pace over the next few weeks. The program length varies between one and two months depending upon the degree of visual error. The fees for OrthoK treatment include all visits in the first year.
The final wearing time depends on many variables, but the treatment aim is good unaided vision all waking hours, with lenses being worn overnight only. Some patients will be able to wear their lenses every second night.
Does OrthoK have any advantages over laser surgery (Lasik)?
The following are some of the advantages of OrthoK:
- An ethical surgeon will not treat a patient until they are at least 18 years old.
- OrthoK does not cause the permanent hazy vision experienced by some patients following laser surgery.
- Changes in prescription over time can be dealt with without further surgery.
- The procedure is totally reversible (Lasik is not).
- There is very significant understanding of the effects of contact lens wear on the cornea, because of the many years of lens use. Lasik’s effects are not totally understood.
- There is no post-operative pain or recovering period.
- OrthoK is significantly cheaper than Lasik and does not preclude surgery in the future.
Is OrthoK expensive?
The procedure is time consuming and may involve several lens changes. For this reason the initial costs are greater than conventional contact lens correction but less than refractive surgery. Once the treatment is complete, the on-going costs are significantly less than the latest options in soft contact lens wear.
What are the advantages of OrthoK?
- Good vision without spectacles or contact lenses all day.
- This is not a surgical procedure.
- It is reversible.
- It is modifiable.
- Early research suggests it will slow down the progression of myopia in children.
- Using well established contact lens fitting techniques means that there are very few risks.
What are the disadvantages of OrthoK?
- You must be prepared to allow for four to six visits over three to six months.
- Continued lens wear is essential or the cornea will revert to its original shape.
- The degree of success is high but cannot always be guaranteed.
- The speed of reduction in the myopia varies from one person to the next.
- You must follow the instructions implicitly for the best results.