[Anatomical, morphological and biomechanical aspects of accommodation]. / Anatomo-morfologicheskie i biomekhanicheskie aspekty akkomodatsii.

The article reviews the findings on the anatomy, morphological and biomechanical features of the accommodation apparatus. Modern methods of imaging and biometry confirm the validity of the Helmholtz lenticular theory of accommodation, according to which its mechanism involves three main components: the ciliary body, the zonular fibres and the lens capsule, the lens itself. Based on this, there is certain interest in studying the degree of participation of each of these components in the development of age-related changes in accommodation (presbyopia).

[Assessment of age-related changes in lens capsule biomechanics using atomic force microscopy]. / Otsenka vozrastnykh izmenenii «biomekhaniki¼ kapsuly khrustalika na osnove atomno-silovoi mikroskopii.

Studies devoted to the assessment of lens capsule biomechanics can be divided into fundamental and applied. The former are oriented towards analysis of various indicators characterizing elasticity of the capsule as a basal membrane that maintains and changes the shape of the lens, and the latter deal with widespread introduction of modern microinvasive methods of phaco surgery into clinical practice. PURPOSE: To assess age-related changes in lens capsule biomechanics based on atomic force microscopy (AFM). MATERIAL AND METHODS: The study included 50 central fragments of the anterior capsule of the human lens obtained intraoperatively during ultrasonic phacoemulsification by continuous circular capsulorhexis. The measurements were carried out in the Fast Force Volume (FFV) mode. The force curves were processed in the Nanoscope Analysis software (Bruker, USA) using the Hertz model that allows calculating the Young's modulus of the capsule sample based on the dependence of the force on the puncture depth. RESULTS: There was no statistically significant difference in the «stiffness¼ of the inner and outer surfaces before and after removal of the subcapsular epithelium (p=0.25). In all cases, the inner surface of the capsule turned out to be «harder¼ than the outer one. In this case, the ratio of Young's modulus of the inner and outer surfaces has a significant dependence on age (p<0.001). With an increase in age from 50 to 90 years, this ratio decreased from ~7 to ~1.5. This was due to a simultaneous change in Young's modulus of the opposite nature: an increase in the stiffness of the outer surface and its decrease in the inner one. CONCLUSION: It is possible to assess lens capsule biomechanics using AFM if the subcapsular epithelium is present. In this case, the objects of study are the areas of the capsule free of epithelium, and the epithelial cells themselves can be used to identify the inner surface of the capsule. Regardless of age, the stiffness of the inner surface of the anterior lens capsule significantly exceeds that of the outer surface.

[Atomic force microscopy in the study of anterior eye segment structures]. / Atomno-silovaia mikroskopiia v issledovanii struktur perednego segmenta glaza.

The application of atomic force microscopy (AFM) in ophthalmology is considered with respect of the classical anatomical division of the eye into anterior and posterior segments. The review presents the findings of published research studies that involved AFM as a method for assessing anatomical and functional condition of the structures of anterior eye segment. One significant line of research is related to the use of AFM technologies for evaluation of morphological and biomechanical characteristics of various parts of the eye lens. That topic draws interest due to the need of furthering the understanding of cataractogenesis, as well as the significance of the anatomical and functional characteristics of the lens capsule in the mechanism of accommodation and modern phaco surgery.