Personalized laser vision correction

Often patients familiarizing themselves with the list of operations offered by a medical institution notice how the price tag differs from a common surgery type. This is especially true for the so-called personalized (individual or customized) methods, i.e. personalized laser eye surgery. The marketing term "Super" is often placed next to the type of a surgery. Why do clinics overcharge because of this "Super"? Let's figure it out together. We want to make a reservation right away that not everyone does this. It looks like the price for the same type of surgery in different clinics may differ by a factor of two or more, although the same equipment is used. Conventional laser vision correction for the treatment of refractive errors accounts for the lion's share of laser refractive corneal surgery. Nevertheless, there are about 10% of patients (we speak from our own experience) who need an individual approach.

Sometimes this approach is necessary in order to try to eliminate irregularities (see Fig. 1) and to achieve a better result or some kind of scars on the surface of the cornea for therapeutic purposes (scar eyes), irregular astigmatism (see Myopia, astigmatism and laser vision correction). Eye laser correction of presbyopia is often referred to individual methods as there an additional depth of field is achieved in the distance and for reading ^{1 2}. Individual approach is also necessary to correct any consequences of unsuccessful operations. Such irregularities are called high-order aberrations. Low order aberrations include myopia, hyperopia, and astigmatism. Roughly speaking, an individual approach is needed in cases where high visual acuity cannot be achieved with glasses. In such cases, there are various effects like ghosting, glare or splitting at the edges of the image, etc.

Fig. 1. Schematic representation of irregularities

If you have a prescription for your glasses, then there are low order aberrations. One of the first will be recorded, for example myopia Sph. -2Dpt. with astigmatism in the form of the presented refractive cylinder Cyl. -1Dpt., Rotated by any degree (see Astigmatism). And as we know, this is temporarily corrected by a simple selection of glasses at the doctor’s office. In this case, the recipe for myopic astigmatism is Sph. -2 diopters / Cyl. -1Dpt. @ 180^o.

Personalized laser ablation requires a thorough analysis of the topography of the eye, i.e. maps of corneal irregularities and its optical power in each area, each of which has an effect on the quality of vision. Such a measurement is made by a device called a topographer. Therefore, you cannot simply take and evaporate the same amount of tissue in nearby areas like in common optimized surgery types. It may not be enough to investigate how the cornea focuses light; additional scattering comes from the lens of the eye. For such purposes, a so-called aberrometer is needed, a device for measuring the total distortion of light in the eye.

It should be understood that the measurement of the surface and refraction of the eye is repeated several times in order to avoid the possibility of errors. Based on the data obtained, the attending surgeon chooses the best one from all the available topography maps and compares the data with the subjective selection of glasses in order to find the best compromise between them. All this requires both time and experience of the surgeon in order to accurately compensate for all existing irregularities that affect poor visual acuity. When the surgeon makes a choice, the data is loaded into the laser and performed with both superficial and flap-types of laser vision correction. Now we understand why clinics often inflate prices for this method of surgery.

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Bibliography

1. Sinjab MM, Cummings AB. Customized Laser Vision Correction. Springer International Publishing AG; 2018. doi:10.1007%2F978-3-319-72263-4
2. Li SM, Kang MT, Wang NL, Abariga SA. Wavefront excimer laser refractive surgery for adults with refractive errors (Review). Cochrane database Syst Rev. 2020;12:CD012687. doi:10.1002/14651858.CD012687.pub2