Between -6 and -8 dioptres of myopia around 77.5% of patients achieve this +/- 0.5 dioptre result and beyond -8 (the limit being around -10) the figure is 60%.
When dealing with higher prescriptions it is helpful to consider those patients achieving within plus or minus 1 dioptre of emmetropia (zero prescription), since, this gives a much better correlation with patients’ satisfaction. For example, if a patient with -10 dioptres of myopia (a very high prescription) has around 90% eliminated they have only 1 dioptre “left over” and are usually thrilled with the results. They will be able to see at least ½ way down the opticians’ chart without spectacles and close reading will be very good without spectacles. In addition, if required, this residual myopia can be retreated very successfully allowing for a 3 month period of stabilisation.
David Gartry’s retreatment rate for 2014 (the last full audit year) was 3.5% – and, as can be seen from the above results, patients with high myopic prescriptions will tend to have a higher percentage chance of requiring a retreatment.
The histogram / bar chart below shows that the unaided vision achieved after Lasik clearly depends upon how high the prescription was initially. For example; 100% of patients with up to -6.00D before LASIK achieve 20/40 or 6/12 unaided (the UK minimum driving standard) unaided (or better). Ninety eight percent of patients with low to moderate degrees of myopia achieve 20/20 (6/6) or better unaided and 90% of those with -3.00 to -6.00D achieve this higher standard. The typical trend of lower percentages of patients achieving 20/20 unaided as higher degrees of myopia are treated (beyond -8.00D) can be seen.