Vision is our guide in the world. We get more than 90% of information about our surroundings with its help. Therefore, it is vital for those with very weak eyesight to get it back to normal. Many people will give a ready answer to this problem: there still exists a good chance to do it, which deals with excimer laser correction. And this is absolutely true since the application area of this method is wide enough. With its help, treatment for myopia up to – 15.0 D, hyperopia up to + 4.0 D, and astigmatism up to ± 3.0 D becomes possible.
But what is the solution for the people with even worse eyesight parameters or those with contraindications to excimer laser correction due to some individual reasons?
In these cases, ophthalmosurgery offers other methods for treating myopia.
1. Clear lens extraction (lensectomy)
Clear lens extraction (lensectomy) is used for treating high myopia up to – 20.0 D. In cases when it is inadvisable to perform excimer laser correction (refraction anomaly of higher grades) or a crystalline lens has lost its natural accommodation ability, a transparent crystalline lens is removed and an artificial lens (intraocular lens) of the necessary optical power is implanted. The point is that the optical power of a crystalline lens is equal to about 20.0 D even in case of high myopia. That is why in most cases an eye cannot focus the image onto the retina without it.
When myopia is high, a negative-powered lens may be used, and in case of high hypermetropia, not one but two lenses are inserted into the capsular bag at a time. Surgeries of this kind are performed using phacoemulsification technique (a crystalline lens is emulsified with an ultrasonic handpiece and aspirated from the eye). The surgery is performed under local (eye drops) anesthesia which is easily tolerated by patients of different age groups. An ophthalmic surgeon performs all manipulations through a 2.5 mm self-sealing micro-incision which does not require suturing. There is no need in admission to hospital since the surgery is performed in a “one-day” mode.
Nowadays, ophthalmologists have a great amount of artificial crystalline lenses at their disposal, which are chosen for each patient individually not only in regards to the state of a person’s visual system but due to his or her age and occupation.
The most popular types of artificial crystalline lenses are:
- Multifocal lenses. These lenses are specially designed to imitate the work of a natural crystalline lens of the eye and to achieve an appropriate visual acuity at both close and far distances. This allows a person to significantly decrease his dependence on glasses or to get rid of glasses at all. Multifocal lenses help people to compensate for the lost accommodation ability, being designated for patients who require visual adaptation at different distances.
- Lenses with a special yellow filter, which possess the properties similar to a natural crystalline lens of the eye. It protects the retina from a damaging effect of ultraviolet and blue light and reduces the risk of progression of age-related retinal disorders.
- Aspheric lenses with aspheric surface and a yellow lens filter. Besides protecting the retina from ultraviolet and blue light, they provide a clearer and sharper vision at nighttime. It is essential, e.g. for drivers.
This technique for treating myopia is applied when natural accommodation of the eye (the ability to clearly see objects at both close and far distances) has not been lost yet and lenses can be implanted into the eye without removing the patient’s natural crystalline lens. Phakic lens implantation is similar to the correction technique using contact lenses. The difference is that contact lenses are worn on the cornea whereas phakic lenses are implanted into the posterior or anterior chamber of the eye while preserving the natural crystalline lens in the same place.
An ophthalmic surgeon performs all manipulations through a 2.5 mm self-sealing micro-incision which does not require suturing. There is no need in admission to hospital. The key advantage of this technique is that phakic lenses make the correction of very high myopia (up to – 25.0 D) possible.
The following types of phakic lenses are distinguished based on the place of their fixation in the eye: anterior chamber phakic lenses, posterior chamber phakic lenses, iris-fixed and pupil-fixed phakic lenses. Posterior chamber phakic lenses are used most often nowadays.
Read more about the implantation of phakic IOLs.
Keratoplasty is a surgery aimed at restoration of the shape and functions of the cornea and eliminating defects and deformations of inborn and post-traumatic nature or gained after a disease. This surgery deals with the replacement of eye cornea with either donor or artificial corneal graft, which is then precisely shaped with help of software modeling. The corneal graft may be implanted into the corneal mass or placed onto the front layers of the cornea or completely replace them.
The surgical procedure is performed under local anesthesia. An ophthalmic surgeon defines the diameter of the corneal tissue to be removed and a donor corneal material of the corresponding size is laid on its place. The donor tissue is attached to the remaining peripheral region of the patient’s natural cornea.
After the procedure the ophthalmic surgeon checks whether the cornea has been adjusted equally well all over the place using a special device – keratoscope. It is highly important for the “created” corneal lens to be as even as possible, with its surface to be presented as an accurate sphere.