Of the large number of polymers used in artificial tear formulations, natural polysaccharides - hydroxypropyl guar, sodium hyaluronate, chondroitin sulfate, dextran, etc., are gaining more and more popularity. Hydroxypropyl guar stands out through its ability to form a long-lasting structured matrix adhered to the damaged ocular surface and ensuring good wettability of the latter and regeneration of epithelial cells. At that, the viscosity of hydroxypropyl guar increases with increasing tear pH (which, in turn, correlates with the severity of xerosis) and further prolongs the moisturizing effect. According to experimental studies, the in vitro protective activity of hydroxypropyl guar surpasses that of sodium hyaluronate, which is widely used. Thus, corneal epithelial cell cultures were more tolerant to drying and pericardial leaflets showed lower friction coefficient, if pretreated with hydroxypropyl guar and not hyaluronic acid. Subsequent clinical studies showed that Systane Ultra was more effective in patients with dry eye syndrome than a carboxymethylcellulose and glycerol-containing drug. It has been also proved that Systane Balance provides a greater increase in thickness of the tear film lipid layer and in overall stability of the tear film as compared to SootheXP, which has a similar lipid composition. The present review also covers potential utility of other artificial tear formulations that, besides the moisturizing effect, are able to reduce the tear film osmolarity, prevent further oxidative stress, and abate the inflammatory process.
In the treatment of patients with dry eye syndrome, the main measure is tear replacement therapy, the most accessible for practicing physicians. It is understandably based on the instillations of artificial tear medications, whose number is steadily growing. In Russia, there are 47 registered medications of this type. Considering the set of requirements for artificial tear medications (which are expected to moisturize the ocular surface, stop the hyperosmolarity of the tear film, ensure osmo-protection and reduce inflammation in the tissues of the ocular surface, as well as activate their reparative regeneration), the most promising medications are those containing two or more active ingredients. One such medication is Oftolik ® medium-viscosity tear substitute that contains a combination of 1.4 % polyvinyl alcohol and 0.6 % polyvinylpyrrolidone. The moisturizing effect of these polymers is complemented by reparative regeneration stimulation (polyvinyl alcohol) and the production of endogenous interferon (polyvinylpyrrolidone). Multiple studies confirmed high clinical efficacy of the medication for the treatment of patients with the main pathogenetic types of dry eye syndrome, as well as its syndromal and secondary symptomatic forms (computer visual syndrome) and revealed. As these effects are achieved with no significant side effects, we can recommend Oftolik® and its preservative-free form Oftolik BK ® for wide clinical use.
Laser photocoagulation of avascular retina remains the standard method for the treatment of retinopathy of prematurity (RP). At the same time, the outcomes of combined multi-stage surgical interventions on the patients presenting with this condition leave much to be desired. In the present review, we have undertaken the analysis of more than 50 articles related to the use of antibodies against the vascular endothelial growth factor (Anti-VEGF) that were published during the period from 2005 to 2015; the analysis included the use of the “off-label” medications as the potentially promising method for the treatment of retinopathy of prematurity. In the overwhelming majority of the studies, the use of anti-VEGF therapy as monotherapy or in the combination with conventional laser photocoagulation has been shown to be efficient for the treatment of stage III+ of the active period of retinopathy of prematurity. One of the important advantages of monotherapy is it does not cause the irreversible destruction of the peripheral retina, in contrast to the action of laser photocoagulation. Moreover, the intravitreal administration of the inhibitors of angiogenesis does not interfere with the growth of blood vessels in the peripheral retina as demonstrated by fluorescein angiography and electroretinography. At the same time, the results of certain published investigations give evidence of the important role played by the vascular endothelial growth factor in the processes of angiogenesis, glomerulogenesis, and alveolarization during the normal lung development. In addition, it has been demonstrated that bevacizumab can migrate from the vitreous body and penetrate into the systemic circulation where it causes the reduction of the serum VEGF levels in the infants presenting with retinopathy of prematurity. In connection with this, the majority of the authors emphasize the necessity of further investigations (based on the results of monitoring the concentration of serum VEGF) for the evaluation of the safety of such medications, their potential long-term effects on other organs and systems in the course of their development as well as possible adverse reactions they are likely to induce. Some problems related to the timing and dosage of the intravitreal administration of the inhibitors of angiogenesis remain a matter of controversy.
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