Orthokeratology, or Ortho K, involves use of specially designed 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).
Although Ortho-K is not exactly new, advances in eye scanning technology and lens manufacture have made its benefits greater in recent years.The technique of Ortho K 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 always worn nightly, alternate nights or 4-5 hours each day after the ideal corneal shape has been achieved in order to retain the effect.
The main purpose of Ortho K is to be free of both contact lenses and spectacles whilst awake. The freedom from any artificial aid appeals to myopic spectacle and contact lens wearers. In addition, those who need to have a certain degree of uncorrected vision to satisfy their employers or a licensing body (e.g. pilots, police) can also be helped by Ortho K. Most patients wear the lenses overnight and remove them on awakening, although some patients wear them solely during the day. Possibly one of the ideal situations for using Ortho K is for the child or teenager with early myopia. Not only does it have all the advantages already given above, but the procedure has also been shown to slow the progression of the myopia in some studies.
No. The procedure works best up to a maximum of 4.00 dioptres of myopia and 2.00 dioptres of regular astigmatism. Errors above this may be reduced but total correction is not usually possible. 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
The initial assessment appointment includes a full eye examination and computerised corneal topographical scanning. This gives the practitioner a chance to assess both the general condition and health of the eyes and also to determine the likely effect of the procedure in that individual. Ortho K contact lenses, made from highly oxygen permeable rigid material, are then fitted using the results of corneal scan to gently reshape the cornea towards less curvature and a more spherical shape. These will be worn for an initial trial and the response evaluated. This will typically take place overnight with a review the next 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 orthokeratology trial will the treatment programme commence.
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 2 to 4 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 ortho K lenses. 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 need to take place then. Stabilisation procedures then follow at a slower pace over the next few weeks. The programme length varies between 1 and 2 months depending upon the degree of visual error. The fees for orthokeratology 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 or most waking hours, with lenses being worn overnight or part of each day only. Some patients will be able to wear their lenses every second night.