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Biomedical subjects

V R Mamikonian

Publications and source records attributed to V R Mamikonian.

At least 19 recordsLinked to original sources
PubMed2003

[An evaluation of the biomechanical parameters of the corneoscleral eye coating in kerato-refractive surgery].

The parameters characterizing the mechanical properties of the cornea and of the adjoining scleral parts as well as the influence produced by radial keratotomy and excimer laser kerato-ablation on the rigid corneal features were studied. The conclusion is that such keratorefractive surgeries (radial keratotomy and excimer laser photo-ablation) worsen the resistant corneal properties. Although the corneal thickness remains unchanged after radial keratotomy, "conditionally weak" sections take shape in the zone of keratotomic scars, in which the probability of ruptures of the cornea at damages to the eyeball increases.

Biomechanical Phenomena↗
PubMed1992

A method of surgical correction of myopia by fashioning a new optically active epithelial surface: keratoepitheliomileusis.

A new form of refractive keratoplasty for the correction of myopia was developed using a new approach to the problem. The midperipheral annular area of the recipient cornea was deepithelialized, and Bowman's layer was removed using a special bore coated with diamond crumbs. A cryolathed annular graft was placed on this prepared midperipheral area of the recipient cornea concentrically with its center. As a result of subsequent reepithelialization inside the transplanted ring, a regular optically active surface was formed. The refractive effect gradually appeared eight to ten weeks after surgery This new optically active surface acted as a lens, consisting of epithelial cells on top of the host cornea. The method required neither cutting of the stroma nor any manipulation in the optical zone of the cornea. A new term "keratoepitheliomileusis" was coined for this new procedure. Eleven patients (12 eyes) with high myopia ranging from 7.5 to 22.0D underwent keratoepitheliomileusis. The refractive and visual results found after four to 16 months of follow-up are presented. Emmetropic refraction occurred in three patients. In the other nine eyes, the deviation from emmetropia ranged from 0.75 to 2.5D. In all patients, uncorrected visual acuity was improved considerably (up to 0.3 to 1.OD) without loss in their best-corrected vision.

Adult↗
PubMed1988

The effect of radial keratotomy on contrast sensitivity.

In the period after surgical correction of myopia and astigmatism in 30 patients (44 eyes) by radial keratotomy, contrast sensitivity deteriorated slightly. The disturbances, however, were transitory, and the general trend was toward restoration of function. Strict adherence to an adequate operative technique prevented a marked decline in contrast sensitivity. The decrease must be considered before surgery, particularly in patients who need a high degree of fine motor control.

Adult↗
PubMedDate not supplied

[New modified method of phacoemulsification in lenticular subluxation].

A new method for cataract removal by phacoemulsification in impaired lenticular joints consists in fixation during surgery of the anterior lenticular chamber along the edge of the capsulorrhexis by 4 retractor hooks and subsequent implantation of a soft intraocular lens. The operation was performed in 6 patients with cataracts of different types complicated by subluxation of the lens. The operation did not involve such complications as vitreous prolapse or displacement of the incompletely dislocated lens. All operations were finished with complete evacuation of lenticular mass and implantation of soft silicone intraocular lenses. The proposed method widens the category of patients in whom modern phacoemulsification can be used.

Humans↗
PubMedDate not supplied

[Original method of extracapsule fragmentation of the lens nucleus during phacoemulsification].

Clinical estimation of different modifications of phacoemulsification revealed the formation of the second tunnel in the nucleus for its division into quadrants in "four-quadrant phaco" increases the required duration of ultrasonography (US) and irrigation, which causes greater endothelial losses associated with the use of nuclear breakdown by means of a chopper tunnel. When the authors used their own methods of "extracapsular half-nuclei" fragmentation, endothelial losses are rather greater than those with the similar method "stop & "chop", which is associated with closer disposition of the US tip to the posterior corneal surface. At the same time nuclear breakdown by means a chapper in the capsular sac by the "stop & chop" method causes dilation of Zinn's ligaments, fraught by their rupture, particularly if latent derangement or defects of the zonular apparatus, and increases the risk of damage to the posterior capsule by the chopper.

Humans↗
PubMedDate not supplied

[Possibilities of prophylaxis of the induced "suture" astigmatism in cataract extraction].

Due to a number of reasons, the traditional methods of cataract extraction, i.e. through 8-12 mm limbic incisions, are still widely used in the clinical practice. A frequent occurrence of a high postoperative astigmatism, even if the operation is successful, is the main shortcoming of different variations of the traditional method of cataract extraction. Possibilities of how to neutralize the induced "suture-like" corneal astigmatism were investigated in this study by using two methods: A. a modified technique of applying a continuous corneal Pirs' suture with elements of an accentuated impact in the projection of the horizontal meridian. B. Meridian keratorraphia--application, in the cornea, of an additional compensatory suture in the projection of the horizontal meridian. Studies were made in two groups of patients after extracapsular cataract extraction (ECE) with intraocular lens (IOL) implantation--a total of 30 patients, 30 eyes. The main group was divided into two subgroups--A and B--(10 patients and 10 eye in each) in accordance with a used method of compensating the induced astigmatism. 10 patients were in the control group. A comparative evaluation of changes of a degree of the original astigmatism, which occurred under the influence of the sealing suture, showed that the parameters of induced astigmatism in the control group essentially and reliably (p < 0.001) exceeded the similar parameters registered in both subgroups of the main group; finally, the efficiency of method B in respect to neutralizing the "suture" astigmatism out did the possibilities of method A (p < 0.01).

Astigmatism↗
PubMedDate not supplied

[A new method of macrofragmentation of dense nuclei by using loop fragmentizer].

The study results showed a principle possibility to fragmentize the most dense lens nuclei by means of a nylon cutting loop. The safety and efficiency of applying a loop fragmentizer in phacoemulsification of high-density cataract were equally demonstrated. The method advantages are conditioned by that a preliminary splitting of the nucleus into fragments without trenches being shaped cuts essentially the total capacity and duration of ultrasound impact, thus, the irrigation time and the needed volume of balance salt solution also decrease intraoperatively: it, naturally, diminishes the generally-known traumatic aftermaths of surgical intervention.

Aged↗
PubMedDate not supplied

[Results of a complex evaluation of accommodative asthenopia in using different-design video monitors].

Eighty volunteer computer operators were examined experimentally under the conditions of working with different-type video monitors, i.e. electron-beam (EB), liquid-crystal (LC), including different visual loads (typing, computer games, and gaze fixation). Experiments lasted for as long as 6 hours. The absolute accommodation volume (AAV), relative accommodation reserve (RAR) and ergograms were comparatively evaluated. A lower AAV was registered in all types of visual loads under the conditions of using different-type monitors, and it made up 0.27-1.08 diopters. A maximum reduction of AAV was detected for gaze fixation and while working with liquid-crystal monitors. The RAR reduction ranged from 0.31 to 0.63 diopters. A maximum RAR reduction was noted for gaze fixation and while using the electronic-beam monitors. The nature of changed ergography curves occurred within the interval between I and IIb types of ergograms. In case of typing, the ergogram deviations were registered to a greater extent for the liquid-crystal monitors. The value of deviations for computer games was bigger, at the experiment end, for EB rather than for LC.

Adult↗
PubMedDate not supplied

[Phacoemulsification of cataract in patients with high myopia].

We conducted a study for the purpose of developing a phacoemulsification technique for patients with high myopia optimized for the specificity of myopic eye. The study involved 124 (165 eyes) patients with high myopia and cataract. The lens density in operated patients was of degrees II-IV according to Buratto. The anterior-posterior axis of the eyeball ranged from 26.5 to 34.00 mm. the patients were shared between the experimental (92 eyes) and control (73 eyes) groups with respect to a used surgical technique. A modified procedure was applied in the experimental groups and the basic technique was used in the control group. The time of lens extraction, the volume of used irrigation liquid and the frequency rate of intra- and postoperative complications were the criteria in efficiency evaluation. The study showed the modified surgical procedure of phacoemulsification to ensure a better visualization, to reduce the load on the lens ligamentous apparatus and to facilitate, as much as possible, manipulations made on the lens nucleus of myopic eye; it also cuts the time of cataract lens extraction, which ensures a less volume of used irrigation liquid.

Adult↗
PubMedDate not supplied

[A comparative evaluation of astigmatic neutrality of 5 mm self-sealing tunnel incision of different types].

The impact produced by incisions of 2 examined types on the corneal refraction was studied in 40 patients (40 eyes) shared between 2 groups according to an incision type. 5 mm tunnel self-sealing incisions of 2 types, i.e. temporal corneal one longer by 3 mm, and upper linear sclerocorneal one stabilized by horizontal suture, were made use of. The obtained refraction was evaluated on week 1 and then in 1 and 3 months after surgery. Group 1 (surgical approach: 5 mm linear sclerocorneal tunnel incision): the mean value of induced astigmatism made 0.68 D during the initial 3 postoperative days, 0.62 D in 1 month after surgery and 0.73 D in 3 months after surgery. Group 2 (surgical approach: 5 mm temporal corneal tunnel incision): the above value made 1.1 D during the initial 3 postoperative days, 0.7 D in one month after surgery and 0.52 D in 3 months.

Astigmatism↗
PubMedDate not supplied

[Refraction epikeratoplasty in correction of high ametropia and treatment of keratoconus].

The results of 48 surgeries (refraction epikeratoplasty) for aphakia, high ametropia, and keratoconus evidence the efficacy of such operation in the afore-said conditions. Further studies are necessary to elucidate the pathogenesis of complications, improve the technique of surgery and technology of the transplant preparation in order to make it more safe and improve its functional results.

Aphakia, Postcataract↗
PubMedDate not supplied

[Keratoepitheliomilesis--a new method of surgical correction of myopia].

The technique of refraction keratoplasty for correction of myopia has been developed. On the deep epithelial surface of the cornea a ring-like layer transplant made of frozen donor cornea has been transplanted. The mechanism of the refraction effect of the operation which developed in 2.5 months after the operation is based on the specific properties of the corneal epithelium. Re-epithelialization of the transplant and the central zone of the cornea after the operation leads to the formation of a new optically active surface acting as a negative lens from the epithelial tissue. Clinical assessment of a new technique has been made in 8 patients with high myopia (from 7.5 to 22.0 diopters).

Adult↗
PubMedDate not supplied

[The 1st experience with complete stromaplasty--transplantation of the cornea].

The results of experimental and clinical trials of a new type of transplantation of the cornea, stromaplasty, have shown the possibility of a blunt detachment from Descemet's membrane and removal of the deep lamellae of recipient's stroma, followed by replacement of the defect with a through allotransplant. Further studies are necessary to validate this first successful surgery and to objectively assess the prospects of such surgery.

Adult↗