Astigmatism is the difficulty to bring images into focus resulting from an imperfectly spherical morphology of the cornea caused by variable optical axes.
Whereas in myopia the image is brought into focus in front of the retina and in hypermetropia the focusing occurs beyond the retina, the processes underlying astigmatism are of a different nature altogether.
If we imagine the eyeball as a spheroid traversed longitudinally by a series of axes, we can say that when focusing occurs in accordance with one of these sagittal lines, we have astigmatism.
When astigmatism is the only visual defect exhibited by the patient, it is called simple; when it is associated with myopia or hypermetropia, it is referred to as composite myopic astigmatism or composite hypermetropic astigmatism.
When the astigmatism can be corrected, surface treatments using excimer laser to modify the curvature of the cornea are particularly challenging, especially if astigmatism occurs in conjunction with other impairments.
Dr Pinelli has devoted a great deal of attention to this important concern for any refractive surgeon, and has developed his own technique in which the delivery of the excimer laser to the corneal surface is broken down into stages.
The underlying assumption is that modifying the corneal profile of an astigmatic eye is a lengthy process, depending on the amount of corneal tissue needing to be ablated with the excimer laser.
The key concern of any eye surgeon has always been not to put the eye under excessive strain with lengthy operations. In the case of refractive surgery, the effectiveness of the procedure depends very much on the speed and lightness of the operation.
Roberto Pinelli has therefore developed a sequential ablation technique for treating astigmatism that breaks the procedure down into stages. In so doing, he has significantly reduced both operation times and the amounts of tissue needing to be vaporised as compared to the traditional approach.
Over the years, his sequential ablation has established itself as a method that guarantees excellent results for astigmatic patients, saving the eyes unnecessary strain and therefore ensuring higher levels of safety.
Download the scientific article
Pinelli R., Nchuinang Ngassa E., Scaffidi E., ‘Sequential approach to the correction of mixed astigmatism’, Journal of Refractive Surgery, Volume 22, October 2006