Laser ophthalmology

To date, ophthalmology has developed a new direction - eye microsurgery. Its main feature is a minimal trauma to the eye during surgery. This allowed to move some eye operations from the hospital in the ambulance.
Particularly impressive is the use in the specified field of laser surgical techniques. Without opening the eyeball were held surgery for anterior segment of the eye and in the rear segment. The laser beam was able to "weld" detached retina, and do other operative intervention.
The principle of thermal influence was laid in the first ophthalmologic laser installations. The laser beam high intensity heated cloth eyes. Depending on the heating temperature was achieved effects - from coagulation to the evaporation of the irradiated area.
Studies have shown that the temperature not only depends on the laser intensity and duration of exposure, but also on the spectral composition of radiation and absorption ability of the fabric, its thermal properties and other factors.
Reducing the length of exposure reduced unwanted overheating neighboring tissue. So there was a pulse photocoagulator with pulse duration from a few hundredths of seconds to 1 MS. Further compression of up to 1 MS and less led to a new effect. Laser treatment has become a "cold"because for such a short period of time due to the inertia of the heat does not spread to surrounding tissues. In place of exposure to the laser beam, very high intensity reached in the compressed pulse, there is an instant evaporation tissue. This process is similar to the local microexplosion. The focal point of the laser radiation of a hole. When such operations coagulation effect is undesirable, as it results in long-term period to overgrowing specially created perforation holes.
The described principle is implemented in pulsed ruby laser modulation factor, which is applied in the first ophthalmologic installation of this type "Yatagan".
The installation of these are designed for operations on the anterior segment of the eye using a focused laser beam. They allow to perform surgery without opening the eyeball and any anesthesia. This virtually eliminates the possibility of postoperative complications.
Installation "Yatagan" used to treat open-angle and angle-closure glaucoma, soft and secondary cataracts, occlusions of the pupil and cysts iris. In the basis of the above transactions is the creation of eye tissues sprocket holes, through which in the future by the outflow of the fluid. The long existence of the holes from several months to several years provided by the fact that in a very short laser pulse not have time to develop coagulation and inflammation processes that lead to the obliteration of the damaged tissue.
Installation type "Yatagan" are produced in two modifications "Yatagan-1" and "Yatagan-2". Part of the installation "Yatagan-1 includes pulsed ruby laser modulation factor, helium-neon laser, binocular microscope, the protector eye doctor from the effects of reflected laser beam, the coordinate table, calorimeter for control of pulse energy, remote control and power supply. Part of the installation "Yatagan-2", besides the above, includes advanced slit lamp.
The working body of the installation "Yatagan" - pulsed ruby laser modulation quality. A ruby crystal, which is based alumina with partial replacement of ions of aluminum, chromium ions is irradiated by a powerful light source xenomai pulse hassanagas lamp. Located in the ground state of chromium ions, absorbing the light quanta hassanagas lamp, go into the excited state. But as a result of thermal treatment with the crystal lattice go into metastable state with a lower energy level. The residence time of chromium ions in metastable state is quite long. In case of spontaneous transition of chromium ions from the metastable state in regulation and is coherent monochromatic radiation at two wavelengths of the order of 0,69 microns. If you provide managed within a very short period of time the transition process, generates a short pulse with a significant level of radiation intensity. To obtain such pulses applied in setting the modulator of footropes type. For many years in laser microsurgery of open-angle glaucoma has been the problem of obtaining the long-term functioning of holes in the inner wall of the canal of schlemm's. Attempts to use with this aim lasers coagulating effect proved the possibility of perforation trabeculae, however, to solve the problem of education of the long-term functioning of holes using the "heat" of lasers for a long time failed due developing rough Scar changes in the area of laser irradiation. The reason of above mentioned changes were connected with insufficient for these purposes, the radiation power of lasers of this type.
Technically, the problem was carried out with the help of lasers with a maximum destructive and minimum coagulating effect. The use of lasers of this type in ophthalmology became possible thanks to the studies of academician of AMS of the USSR, Professor M. M. Krasnov (1970-1972). For the treatment of open-angle glaucoma he proposed a method of tapping the walls of schlemm's channel from the front camera with the power of ruby laser with a q-switched.
Focusing the beam on the structure of the anterior chamber is carried out by means of direct operational gonioscope M. M. Krasnov. At the bottom, as a rule, the widest part of the chamber angle (patient while looking down most) a ruby laser beam destroy trabecular tissue in the area of the projection of schlemm's channel. The beam is focused in places of the greatest congestion of pigment. Pulses are applied approximately on equal distance from each other so that the impact zone as a whole amounted to 1/4 - 1/6 part of the circumference of the chamber angle. The number of pulses during one session ranged from 10 to 30. In repeated sessions area laser exposure remains the same or is located next to it. Laservariorakurs performed under local anesthesia safely, easily tolerated by patients.
The criterion of validity of opening the internal stitches schlemm's channel - independent or induced bleeding from sinus in front of the camera via formed in the trabecula holes. This phenomenon remains positive and long-term (over 5 years) after laservariorakurs that is a clinical confirmation of the long-term functioning of holes in the inner wall of the canal of schlemm's.
In the research Institute of eye diseases in the Department of laser methods of treatment laservariorakurs successfully applied within 10 years. Over this period was
therapy more than 400 patients with primary open-angle glaucoma. Laservariorakurs (with proper definition of the indications) leads to long-term and stable compensation of intraocular pressure (IOP) and hydrodynamics with stabilization of visual functions, IOP is reduced on average by 8.5 mm RT. century, and the coefficient ease of movement increases by 2-3 times. 85% of the patients, laservariorakurs allowed to avoid surgical treatment. Miocici were completely cancelled after laservariorakurs 38%and 62% mitotic regime was considerably weakened.
Complications observed in laservariorakurs (dot destruction of the corneal epithelium, increased intraocular pressure, corneal edema, injured root iris), a short, usually reversible and do not lead to violation of visual functions.
Laser iridectomy a qualitatively new stage of treatment and prevention of glaucoma private corner. The method has changed the traditional understanding of iridectomy - as laservariorakurs, the procedure is not accompanied by the opening of the eyeball, minimally traumatic and is conducted in the outpatient setting. In the absence of effects after laser iridectomy not excluded traditional surgical intervention. Advantages of laser iridectomy undoubted with intolerance of drugs, with severe somatic state of the patient, when surgery is contraindicated.
In recent years published enough of works devoted to application of laser iridectomy when glaucoma. Coloboma in the iris can be obtained by radiation of an argon laser, the mechanism of action is dominated by thermal component. Through hole in the iris is formed as a result of repeated sessions of the argon coagulation with different time intervals or at one time session.
For the first time the method of laser capsuleaccutane (LQFP) soft cataracts by setting "Yatagan" was developed in 1975 by academician M. M. Krasnov and the Department of laser methods of treatment research Institute of eye diseases of the Ministry of health of the USSR, candidate of medical Sciences C. S. Hakobyan.
In some cases, in order to strengthen decizionala effect of laser applications artificially achieve the appearance of clusters of pigment on the front lens capsule. This is achieved by an argon laser coagulation of the iris on pupillary edge on the background of the preliminary medical Misa. After 5-6 days induced laser coagulation back synechia break through frequent (5 to 6 times a day) local instillation midriatikov (for example, a 1%solution of atropine). Applications modulated laser radiation is applied precisely in the areas of accumulation left on front lens capsule pigment.
After treatment, all patients constantly appoint instillation midriatichesky of funds to support the pupil in the expanded state to avoid the rear of adhesions and pupillary box due to swelling and waning of lenticular masses. Periodically exercise control intraocular pressure.
According to M. M. Krasnov, and C. S. Hakobyan (1976), 5 patients from 15 subjected LQFP, there was a full resolution content of the crystalline lens. Three of these patients achieved visual acuity corresponded 0,9-1,0. Two patients (cases of unilateral congenital cataracts) improvement of visual acuity does not occurred, apparently, because of the deep obscurations amblyopia. Eight patients as a result of partial resorption cloudy substance of the lens getting better visual acuity with svetoshumovye to 0.2 to 0.8.
In two cases (despite significant opening the front lens capsule) after swelling lenticular substances tended to organization of the masses, and resorption followed. These patients were subsequently subjected to the surgery (aspiration), which produced a high visual acuity.
One patient who was a partial resorption of the mass of the lens, was also operated. Since in this case there was a unilateral cataract, a significant improvement in visual acuity does not come.
During the whole period of observation of dynamics resorption soft cataracts after capsuleaccutane (duration up to 8 years) in any case not observed phenomena pokojnogo iridocyclitis or secondary hypertension.
The method of laser decizii energy simulated laser ("Yatagan-2") films secondary (true and false) cataracts was first proposed in 1975 by academician M. M. Krasnov.
As with laser capsuleaccutane, radiation is bringing helium-neon laser installation "Yatagan-2" focus angle of 45-60° under the control of a slit lamp microscope on the film surface secondary cataract in Central and most of her slim to identify the last use of the optical section). If on the film surface there are separate clusters or glybki pigment located in the Central or paracentral areas, radiation try to focus on them.
It should be emphasized high efficiency of the procedure of laser decizii films secondary cataract held by setting "Yatagan-2". So, in the case of macular pathology, corresponding aphaktic correction allows to achieve high patterns of view in the first 10-15 minutes after the operation. As easy and painless have a positive psychological impact on the sick, relieving him from the need of repeated surgical intervention.