Alternative treatment of the cornea
The concept of the modern treatment of keratoconus is based on three basic conditions:
- To stabilize the anatomy of the cornea;
- To slow down the progression of the disease;
- To achieve the highest possible visual acuity.
Effective medical care for patients with keratoconus at various stages of the pathological process may be implemented by the following operational methods:
- Corneal collagen cross-linking;
- Implantation of intrastromal segments;
- Penetrating keratoplasty using a corneal graft.
Corneal collagen cross-linking
The main problem associated with the development of keratoconus – thinning of the cornea. Weakened cornea gradually deforms with the participation of the intraocular tension. On this background, the person has a rapidly developing and progressing uncorrectable astigmatism, which leads to a significant vision deterioration.
The first symptoms begin to appear on one eye – there are complaints about discomfort while wearing the lenses, the need for frequent change of the optical power of glasses.
Ignoring the disease can lead to serious consequences, when the only treatment option is implantation of a corneal graft – keratoplasty. But today there are other modern methods of treatment of keratoconus – cross-linking of the corneal collagen.
The method is indicated in case of progressive keratoconus at early stages of development, severe keratoconus without corneal opacity, as well as iatrogenic keratectasia (protrusion of the cornea after performing excimer laser refractive surgeries).
The mechanism of action of cross-linking is to unite separated corneal stroma fibers into a single solid network under the action of low-intensity UV light in the presence of the photosensitive substance – riboflavin. Thus, is achieved strengthening of the properties of the cornea, increases its resistance to the formation of its protrusions, stops the progression, and, in some cases, even a possible regression of the disease.
In the development of this method, a significant role was played by the group of scientists from the Eye Clinic of the Technical University of Dresden (Germany) under the guidance of prof. Theo Seiler. Cross-linking has also received the European certificate and is widely used in many leading clinics in Europe.
The method made a revolution in the treatment of keratoconus and was awarded with the highest award of the American Ophthalmological Society – the Kellman Prize in 2008.
The effectiveness of the method has surpassed the expectations of many experts. According to the reports of ophthalmic clinics, the stabilization of the pathological process at keratoconus after the operation of cross-linking occurs in about 95% of cases. In the reports submitted by experts at ESCRS Congress (European Society of Cataract & Refractive Surgeons) were published the results of an extended monitoring according to groups of treated patients. The average value of the corneal refractive power is reduced by 3-4 diopters, astigmatism by 2-3 diopters. Visual acuity improved by 1-4 lines and continues to rise during the second year of attendance.
In the Dnepropetrovsk Regional Clinical Ophthalmological Hospital this method has been implemented since 2009. To date, in the clinic were operated 131 such patients, 15 of whom are children.
Contraindications for cross-linking
- · The method is not indicated at corneal excessively small thickness (less than 400 microns) because of the potential damage to the endothelium by ultraviolet;
- · Excessive top holding of keratoconus;
- · Opacity of the cornea and low visual acuity with correction;
- · Increased sensitivity to riboflavin;
- · Active comorbidities (e.g., allergy and infectious diseases at the acute stage);
- · Pregnancy.
Before deciding to have a cross-linking operation in an ophthalmic hospital, you need to conduct a full eye examination, similar to examination before refractive surgery.
The procedure is performed in the operating room and consists of several steps:
- Previously anesthetic eye drops are spotted, 1 pill with analgesic effect is taken; and also are spotted special drops containing a photosensitive component, which saturates the stromal layer of the cornea.
- For a better penetration of riboflavin into the tissue, ophthalmic surgeon affects with a laser the saturated by the substance cornea by removing the cover layer (epithelium) from the central part of the cornea;
- The corneal coat gradually saturates by riboflavin with the help of frequent spotting during 30 minutes;
- After obtaining the desired concentration of riboflavin is produced the illumination of the cornea with ultraviolet light during 30 minutes while spotting the solution at the same time.
In the result of the procedure happens "cementing” of the cornea with strengthening of its structure, which slows down its further thinning and bulging in the center – stops the progression of keratoconus and eye refraction remains stable.
The entire procedure takes about one hour and a half (one eye) and runs absolutely painlessly.
After the surgery, the patient a special soft contact lens within a few days, painkillers are prescribed. Antibacterial drops are used; means that accelerate the recovery of the epithelium. It is advisable to wear sunglasses.
The patient should be checked during the first 3-4 days after surgery, then – in a week, month, and 3 months after intervention.
Upon request of the patient further dispensary observation is possible.
Since the procedure involves ultraviolet effect and almost complete removal of the surface layer (epithelium) of the cornea, then almost always arise:
- A slight pain in the eye (they slowly subside almost disappear, usually after 48 hours);
- Redness of the eye for about 5-7 days after surgery;
- Blurred vision (corneal stromal edema), may continue (slowly decreasing) for 6-8 weeks.
After this period, visual acuity stabilizes. Up to about 6 months after surgery at an early stage of disease visual acuity may increase in comparison with the original.
After the cross-linking there is no improvement of the refraction, the procedure is aimed only at strengthening the cornea, but not at optical correction of keratoconus.
Cross-linking is carried out once, and in most cases gives a stable increase in the strength of the cornea from 4 to 10 years, after which the procedure can be repeated if necessary.
The method meets all modern safety requirements. To date, significant side effects were not detected.
In the result of clinical trial cross-linking procedures which were conducted in 5 European countries, there were no pathological effects of UV radiation neither on the lens, nor on the retina, due to dosed penetration through the cornea saturated with riboflavin.
Implantation of intrastromal segments
Implantation of intrastromal corneal segments is an effective and safe method of the treatment and correction of ametropia in case of keratoconus. In the result of this operation takes place the displacement of the corneal vertex to its physiological position on centre of the optical axis, which allows to improve visual acuity.
First, the idea of using alloplastic materials for refractive error correction was proposed by Barraquer in 1949. Since that time, there were suggested several types of corneal implants (Keraring, Ferrara poly, Intacs), which are used for the correction of aphakia, myopia or presbyopia.
Over the past decade the implantation of intrastromal corneal segments has become the operation of choice in the treatment and correction of ametropia at keratoconus. In addition, other indications for implantation keraring are iatrogenic keratectasia and pellucid marginal degeneration of the cornea (disease from the keratoconus group, but is different in peripheral location of ectasia). Positive clinical results show a persistent effect of the operation.
A promising direction at the stage of forming corneal tunnel is the use of a femtosecond laser, which allows to control the depth, size and shape of the intrastromal tunnel, as well as reduces the risk of intra- and postoperative complications.
Additional conducting of cross-linking of corneal collagen in terms of 6 ± 1 months after implantation of intrastromal corneal segments reduces indices of the Ophthalmometer, increases visual acuity and corneal rigidity, which demonstrates an even greater improvement in the refractive indices and the biomechanical properties of the cornea, as well as the suspension of the pathological process (A.V. Penkina and co-author of the Research Institute of eye diseases named after Helmholtz Ministry of Health, Moscow, 2012).
Clinical and functional studies have proven the efficacy and safety of this procedure after the implantation of corneal segments. Thus, femtolaser implantation of intrastromal corneal segments combined with corneal collagen cross-linking allows to achieve higher and more stable results in the treatment of keratoconus.
Penetrating keratoplasty using a corneal graft
Currently in European countries keratoconus is the most common indication for penetrating keratoplasty (PKP) – it accounts for about a quarter of all conducted penetrating keratoplasty. In Israel keratoconus holds the first place, in the United States and Canada – the third most frequent indications for PKP. High importance of keratoplasty at keratoconus is determined not only by the significant prevalence of this disease, but also a predominant lesion of the young and middle-aged adults.
Today, the PKP for the treatment of far-gone keratoconus is the most successful and productive compared to keratoplasty for other corneal diseases. The PKP continues to be the only radical treatment for keratoconus, which enables to obtain a high visual acuity and fully rehabilitate the patient.
In recent years, thanks to improved technologies of the PKP and restriction of measures of post-operative care, biological outcomes of the operation are becoming more promising. But in most cases, low visual acuity does not correspond to perfect biological results of keratoplasty at keratoconus. One of the causes of poor functional outcome after PKP at transparent engraftment of the implant there are residual ametropies, among which are dominant myopic refraction of varying degree and astigmatism.
Astigmatism of varying degree after conventional penetrating keratoplasty develops in 100% of cases. According to the literature, the main cause of astigmatism after the PKP is a discrepancy of the form of the transplanted graft to the burr hole configuration in the cornea of the recipient because of the difficulty in obtaining a smooth, steep cornea cut around the circle without additional cutting with scissors or a diamond blade, inaccurate arbitrary pre-fixation of the implant, the uneven encircling saturation.
The disadvantages of traditional PKP can be attributed to the inability to obtain the various profiles of discission, endothelial injury, a lack of sealing and biomechanical instability of post-operative wound, a risk of corneal infection.
Taking into account these factors, at the present stage there is a need to establish a safe, predictable and effective PKP method using a femtosecond laser to improve the clinical and functional results of the PKP at keratoconus.
Femtosecond penetrating keratoplasty at keratoconus:
- Gives possibility to form the corneal profile, sticking to a well-defined shape and size, providing optimal opposition of the donor and recipient tissues. Architectonics of the surgical wound provides prevention of displacement of the implant, it contributes to good sealing of the wound.
- Allows you to fix the implant with less tension of loops of the corneal suture, thereby reducing the degree of postoperative astigmatism up to 3,25 ± 1,0 diopters, helping to achieve higher visual acuity (MEE 0,8 ± 0,11 (0,6-1,0 ).
- Reduces recovery time to 8-10 months.
- It reduces the chance of infection, thereby increasing the safety of surgery. (Lebid L.V., N.P. Pashtaev, Cheboksary branch of FDM "ISTC" Eye Microsurgery " named after Acad. S.N. Fedorov RusMedTechnologies", 2012)
Femtosecond penetrating keratoplasty using a corneal graft helps to achieve the best results in the treatment of keratoconus at stages, when the possibility of using other methods of treatment of the disease have been exhausted.
Since August 2013 in the Dnepropetrovsk Regional Clinical Ophthalmological Hospital have successfully been performed femtosecond penetrating keratoplasty using a corneal graft.
Modern diagnostic and operational equipment, knowledge and experience of the clinic’s surgeons allow to provide medical care for patients with keratoconus at different stages of the disease at the level of the advanced world standards.