Syndrome of “dry eye” (SSG) in recent years is becoming increasingly practical significance. In most patients, this disease manifests relatively undefined objective signs, but in some cases, the xerotic process is accompanied by complications from the cornea, which threaten not only impaired visual function, but also the risk of loss of the eyeball. At reception at the ophthalmologist ССГ it is revealed practically at each second patient, thus the general prevalence ССГ in Russia
in patients under the age of 40 years is 12%, in patients older than 50 years – more than 67% [1-3].
The growing prevalence of RCC in young patients is associated, among other things, with an increase in the availability of contact vision correction. Prolonged wearing of contact lenses (CL) is accompanied by the appearance of symptoms of discomfort, burning, sensation of “foreign body” and “dryness” of the eyes. Periodically, patients can complain about “blurring” vision, increased eye fatigue.
With prolonged, long-term use of CL, CCG symptoms are revealed in 100% of cases . In order to prevent the appearance of symptoms of CCG, a detailed understanding of the mechanisms of the effect of CR on the surface of the cornea is required.
Pathogenesis of the development of SSH when wearing contact lenses
As the main factors contributing to the development of CCS in the wearing of CR, release mechanical, hypoxic and toxic-allergic effects. Being in direct contact with the cornea, CLs mechanically affect the epithelium of the cornea and the lacrimal membrane (SP). The degree of negative impact of CR on the structure of the eye depends on the material, design, features of planting the lens. KL promotes the hypoxic state of the eye tissues, dividing the joints into pre- and authentic, thinning the lipid and mucinous layers, enhancing the evaporation of the water layer and disrupting the metabolic function of the tear [4-6]. The irritating effect of CR on the eye surface leads to an increase in inflammatory and protective cell responses, keratinization and changes in the normal state of the conjunctival epithelium. Epitheliopathy arises with changes in the intracellular structures of epithelial cells, which result in cellular edema, intercellular contact disruption, and secretion of transmembrane mucins by epithelial cells. With prolonged wearing of CR changes the composition of the preCorneal joint venture, signs of anaerobic glycolysis appear, the protein content decreases, the content of decay products increases, and the pH shifts to the acidic side [7, 8]. The chain of these changes adversely affects the formation of goblet cells directly involved in the production of mucin tears, as well as meibomian glands producing the lipid component of the joint venture. According to observations of R. Arita et al. (2009), the state of meibomian glands with prolonged use of CR in patients of middle age of 31.8 years corresponded to that of 60-69-year-old people without wearing KL .
Also an important factor contributing to the intensification of pathological changes in the corneal epithelium when wearing a CR is the presence of active preserving and cleansing agents in CL care products [10-12].
Prevention and treatment of SSH in carriers of contact lenses
Taking into account the fact that in some patients the emergence of signs of SSH leads to the rejection of the use of CR, the most reasonable is the preventive use of tear-replacement therapy to prevent the negative impact of CR on the eye tissue [13, 14]. The choice of tear-replacement therapy should be complex, be carried out taking into account the individual characteristics of the patient, the duration of wearing the CR, the condition of the joint vent and the surface of the eye. The prophylactic use of the sludge replacements is most likely to maintain a normal balance of tear-loss, and even with prolonged length of use of the KL, correction of the changes in the ocular surface and the relief of symptoms of RCC are possible .
The purpose of the lacrimer in the CL carriers is the following:
decrease in the risk of development of hypoxic complications due to reduction of the degree of dehydration of CR, increase of its mobility, improvement of the exchange of tears
in the original space and nutrition of the cornea;
reduction of the risk of infectious-allergic complications due to increased stability of pre-coronary joints and improvement of the state of epithelial cells;
correction of neuroreflex regulation of tear production by reducing the mechanical effect on the epithelium and irritating effect on the nerve endings of tissues.
Correction of dysfunction of meibomian glands
When carrying KL an important pathogenetic mechanism should be considered a violation of the function of meibomian glands (dysfunction of meibomian glands – DMZH) and, consequently, a decrease in lipid secretion. This occurs due to the obliteration of the gland ducts, and as a result of blockage of the mouths of the meibomian glands by slipping epithelial cells against the background of the existing chronic inflammation of the surrounding tissues.
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