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A study aimed at assessing the efficiency of presbyopia correction by bifocal contact lenses (BCL) was undertaken; it envisaged a comprehensive evaluation of subjective data provided by patients and measurements of a number of functional parameters of the visual quality for far and near, including mono- and binocular measurements with BCL of different constructions versus a maximal sphero-cylindrical spectacle correction for far and for near. Soft Acuvue Bifocal BCL as well as soft and rigid BCL manufactured in the optical-and-mechanical laboratory of the Research Institute for Eye Disease of the Russian Academy of Medical Sciences and Russian-made and imported bifocal soft and rigid lenses, respectively, were made use of in the study. A reduced contrast sensitivity (mainly in high frequencies) to 7% with Russian-made BCL, to 12.5% with Acuvue Bifocal BCL, to 8.7% with monofocal BCL and to 13.4% with the "mono-vision" system was registered. A decreased visual working ability to 13% with soft bifocal Russian-made BCL, to 17.3% with Acuvue Bifocal BCL and to 20.7% with the "mono-vision" system was detected versus the spectacle correction. A reduction by 25% was noted in the stereoscopic vision indices with the "mono-vision" system. A study of sensitivity to dazzling did not show any statistically reliable differences between various correction types.

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Radiometry of distribution of drugs introduced with soft contact lenses (with 40 and 70% humor content and thickness of 0.2 and 0.7 mm) in the ocular cavity was carried out to compare this mode of drug administration with the traditional methods. The maximal concentrations of the drugs in the anterior chamber humor and in the vitreous body were attained by using saturated highly hydrophilic 0.7 mm thick contact lenses. The drug content in the anterior chamber of the eye upon such a mode of administration was higher than after injection and much higher than after instillation.

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The in vitro kinetics (specifically, absorption and desorption) of drugs belonging to various pharmacological groups (atropine sulfate, gentamicin sulfate, dexamethasone, lecozyme, and poludan) in soft contact lenses (low-hydrophilic with 40% aqueous content and highly hydrophilic with 74% aqueous content. 0.2 and 0.7 mm thick) was studied by radiometry, as were the effects of chemical structure of a drug, hydrophilic properties and thickness of soft contact lenses, and temperature of solution on these processes.

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The accuracy of fixation topogometry that allows to assess the form of the cornea along its whole surface has been studied experimentally. For this purpose, a special metallic standard with a mirror surface has been manufactured, representing a paraboloid of rotation (by the formula Y2 = 2RX, where R = 7.7 mm). The standard was fixated on a face support of ophthalmometers (of the firms "Rodenstock" and "Karl Zeiss") by means of a support providing transference of the standard in two reciprocally perpendicular meridians on the given (5-35) number of grades. The measurements were made in 15 points. At first sagittal radii of the cornea were determined, then the distance height of the points from the central axis (h) and the sag (P) were calculated. The position of points built with the help of P and h in coordinate axes was compared with the standard curve. The range of divergences was minimum (0.01-0.04 mm), this speaking about sufficient accuracy of the method of fixation topogometry.

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The paper analyses results after examination of 276 patients (495 eyes) with different types of rigid and soft contact lenses. A study of some ways for improvement of contact lens tolerance has shown that improvement of rigid contact lenses can be achieved both by perfection of their construction (in particular by using spherotoric rigid lenses) and with the help of gas-permeable materials (in particular, cellulase acetobutyrate). The improvement of soft lens tolerance can be achieved by reducing the thickness of the lens as well us by using highly hydrophilic gels. If the known methods for improvement of contact lens tolerance fail to be effective, medicamentous preparations (such as solcoseryl, taufon, emoxipin) can be used as a method of choice; their usage is justified in keratoconus of stages II-IV, when rigid lenses are a single kind of optic correction and their tolerance is lowered.

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