[Effect of conventional and orthokeratological hard contact lenses on anatomical and functional characteristics of the cornea]. / Vliyanie traditsionnykh i ortokeratologicheskikh zhestkikh kontaktnykh linz na anatomo-funktsional'noe sostoyanie rogovitsy.

Contact lenses are widely used for correction of myopia due to their accessibility, effectiveness and relative safety. PURPOSE: This study evaluated the potential effects of conventional hard contact lenses (HCL) and orthokeratological contact lenses (OKL) on anatomical and functional condition of the cornea in myopia correction. MATERIAL AND METHODS: The study included 80 patients (159 eyes) with low, moderate and high myopia. Group 1 consisted of 40 patients (79 eyes) who used conventional HCL; group 2 included 40 patients (80 eyes) who used OKL. All patients underwent topographic keratometry, corneal pachymetry mapping (Pentacam, Oculus, Germany; Visante OCT, Carl Zeiss, Germany), high-order aberrometry (OPD Scan, Nidek, Japan), confocal microscopy (Confoscan 4, Nidek, Japan), evaluation of corneal biomechanical properties (ORA, Reichert Technologies, USA) and corneal light scattering (Pentacam, Oculus, Germany). Examinations were taken before the treatment started and after 8-12 months of contact lens wear. RESULTS: Group 1 showed corneal thickness increase in all zones (by 0.9-1.1%), no significant changes in corneal refraction, and increase in corneal hysteresis and corneal resistance factor. OKL wear led to a significant flattening of anterior surface of the cornea and steepening of its paracentral area, decrease in central corneal thickness (by 2.8%) and increase in mid-peripheral thickness (by 2.2%). No significant changes in posterior corneal surface were observed in the study patients. More significant increase in higher-order aberrations and the degree of light scattering was observed in group 2, while changes in subepithelial nerve plexus and stromal structure were more significant in group 1. CONCLUSION: Long-term OKL wear shows more significant morphological and functional corneal changes compared to RGP lens.

[Changes in precorneal tear film and ocular surface in keratoconic patients after corneal collagen cross-linking]. / Izmenenie sostoyaniya prerogovichnoi sleznoi plenki i glaznoi poverkhnosti posle krosslinkinga rogovichnogo kollagena pri keratokonuse.

The article reviews the current available data on the signs and symptoms of dry eye syndrome (DES) in patients with keratoconus (KC), describes the clinical features of DES in KC patients and the morphological features of this type of keratectasia that lead to manifestations of the «dry eye¼, and highlights the risk factors, consequences of therapeutic measures, concomitant ophthalmological and general somatic diseases that contribute to the development of DES in KC.

[Prospects for early detection of keratoconus based on systems built for computer-assisted diagnostics of structural changes in the cornea]. / Perspektivy rannego vyyavleniya keratokonusa na osnove postroeniya sistem mashinnoi diagnostiki strukturnykh izmenenii rogovitsy.

The article is devoted to the problem of diagnosing subclinical keratoconus (KK). The need to identify early signs of KK is primarily associated with the potential for the development of iatrogenic keratoectasia in cases of underdiagnosis of the disease when determining the conditions for laser keratorefractive surgery involving a decrease in the thickness of the cornea. Today generally accepted algorithms for early computer-assisted diagnosis of KK are mainly based on the analysis of various morphometric parameters of the cornea, reflecting changes in its shape and thickness induced by structural abnormalities. Direct detection of structural changes in the cornea characteristic of early KK requires the use of high-tech imaging methods that are not always applicable in everyday clinical practice. The promising approach proposed in this study is based on the fact that a digital image of a corneal «slice¼ obtained using serial analyzers such as the Scheimpflug camera widely used in clinical practice provides indirect information about the structure of the epithelial layer, the local thickening of which takes place in the initial stages KK. It is this criterion that underlies the proposed system of computer-assisted diagnosis of KK. The carried out studies have shown the high sensitivity of this algorithm, and its specificity can be increased by involving the known diagnostic indicators of KK.

[Precorneal tear film after corneal collagen cross-linking in keratoconus (preliminary report)]. / Sostoyanie prekorneal'noi sleznoi plenki posle krosslinkinga rogovichnogo kollagena pri keratokonuse (predvaritel'noe soobshchenie).

PURPOSE: To study the condition of precorneal tear film in keratoconus patients after corneal collagen cross-linking (CXL). MATERIAL AND METHODS: The study enrolled 24 patients (30 eyes) with stages I-III progressive keratoconus. All study patients underwent standard (Dresden) protocol CXL. Patients were examined before the surgery and 1 week, 1 month, and 3 months postoperatively. The condition of precorneal tear film was evaluated based on the results of Norn test (the tear film break-up time), Schirmer test, Jones test, optical coherence tomography based lacrimal meniscometry, and improved tearscopy. RESULTS: One month after CXL, patients with keratoconus experienced transient changes in the precorneal tear film condition - the tear film break-up time was reduced, the tear secretion was elevated, the lacrimal meniscus biometry parameters were increased, and the thickness of the tear film lipid layer was decreased. CONCLUSION: Corneal changes resulting from CXL lead to transient disorders of the mucin and lipid layers of the precorneal tear film, which requires adequate tear substitute therapy in the postoperative period.

[The effects of corneal collagen cross-linking on the corneal structure in keratoconus]. / Vliyanie krosslinkinga rogovichnogo kollagena na strukturu rogovitsy pri keratokonuse.

The article reviews the key information regarding morphological changes in keratoconic corneas and dramatic alterations of the corneal tissue induced by corneal cross-linking according to data obtained with in vivo corneal confocal microscopy, presents basic information on keratoconus visualization techniques widely used for diagnosis, monitoring of ectasia, as well as efficacy assessment of its treatment, and lists basic principles of corneal cross-linking procedure and confocal microscopy with consideration of morphology specifics of keratoconic corneas. The article also discusses prospective benefits of further research and longitudinal studies aimed to define the origin of keratoconus and to develop advanced corneal cross-linking protocols.

[Biomechanical properties of the cornea and tonometry measurements]. / Biomekhanicheskie svoistva rogovitsy i pokazateli tonometrii.

PURPOSE: To study peculiarities of intraocular pressure (IOP) measurement by different methods in patients with changes in corneal biomechanical properties. MATERIAL AND METHODS: The study enrolled 154 patients (290 eyes) divided into 3 groups according to the condition of their corneas in terms of biomechanical properties. Group I consisted of 84 patients (168 eyes) with conditionally 'normal' cornea and corneal thickness ranging from 470 to 660 µm. Group II included 44 patients (70 eyes) with keratokonus. Group III consisted of 26 patients (52 eyes) after LASIK. IOP pressure was measured in each patient by pneumotonometry, Maklakov tonometry, and dynamic bidirectional pneumo-applanation of the cornea. Biomechanical properties were evaluated with dynamic pneumo-impression method. RESULTS: The study revealed that in patients of groups I and III, corneal biomechanics affected indices of corneal compensated IOP and Maklakov's IOP to a lesser extent, as opposed to measurements of Goldman tonometry and pneumotonometry. In group II, Maklakov's tonometry had less IOP measurement inaccuracies in comparison to other evaluated methods due to larger applanation surface. CONCLUSION: Changes in biomechanical properties of the cornea can complicate interpretation of the results of different methods of IOP measurement. Accurate determination of IOP requires consideration of biomechanical properties of the cornea, as well as anamnesis data on past corneal diseases or keratorefractive surgeries.

[Changes in biomechanical properties of the cornea after keratorefractive surgery]. / Izmeneniia biomekhanicheskikh svoistv rogovitsy posle keratorefraktsionnykh vmeshatel'stv.

Biomechanical properties of the cornea are important for the functioning of the ocular optical system. They affect such qualities of the system as correct diffraction and resistance to different external action. Keratorefractive surgery widely used in clinical practice nowadays significantly upsets corneal biomechanics, which introduces a margin of error for IOP measurements done by different methods. The article reviews literature devoted to the problem of changes of corneal biomechanical properties after refractive surgeries.

[Structural changes in the ocular anterior segment against elevation of intraocular pressure after repeated intravitreal injections]. / Izmeneniia struktur perednego otrezka glaza na fone povysheniia vnutriglaznogo davleniia posle povtornykh intravitreal'nykh in''ektsii.

Numerous studies have demonstrated the efficacy of anti-VEGF medications for exudative (wet) age-related macular degeneration (AMD). Significant IOP elevation is one of the side effects of anti-VEGF intravitreal injection. PURPOSE: To study the changes in the parameters of anterior segment of the eyeball against acute IOP elevation after repeated intravitreal injections (IVI) of anti-VEGF medication. MATERIAL AND METHODS: The study was conducted on a random sample of 45 patients (45 eyes) diagnosed with exudative (wet) form of AMD. All patients received two 0.05 ml intravitreal injections of ranibizumab with one-month interval. Measurements of IOP were performed with rebound tonometer Icare-Pro (ICare, Finland) before intravitreal injection, then one minute, 30 minutes and 3 hours after. The parameters of the ocular anterior segment, namely thickness and optical density of the cornea, volume and angle of the anterior chamber were evaluated by Scheimpflug imaging (Pentacam HR, Oculus, Germany) before IVI, and 15 minutes after. RESULTS: Statistically significant (p<0.05) elevation of IOP to 40 mm Hg (confidence interval 32-48 mm Hg) was recorded one minute after injecting 0.05 mL of ranibizumab solution into the vitreous cavity with IOP having the tendency for gradual normalization. When measured 15 minutes after IVI, the following parameters of the ocular anterior segment structures had reliably changed in the setting of elevated IOP: corneal thickness had increased to 27 µm (confidence interval 14-38 µm), corneal optical density - to 16.7 (confidence interval 10.4-19.5). No significant changes of either volume or angle of anterior chamber were revealed. Comparative analysis showed no significant changes of parameters after the 1st and the 2nd IVI. CONCLUSION: The revealed changes were transient in nature and did not require any corrections since all parameters returned to baseline after each injection.

[Secondary dry eye syndrome after keratorefractive surgeries and approaches to its treatment and prevention]. / Vtorichnyi sindrom 'sukhogo glaza' posle keratorefraktsionnykh vmeshatel'stv i podkhody k lecheniiu i profilaktike.

The article reviews the particularities of development and pathogenesis of secondary dry eye syndrome (DES) after refractive surgeries including a complex of problems related to changes in tear film content, damage of eye surface and neurotrophic epitheliopathy. Additionally, modern algorithms of treatment and prevention of secondary DES in patients after refractive surgeries are described. Despite the transient nature of the changes, excimer-laser surgery can lead to lasting deficiencies of eye surface in some patients. Therefore, intensive and early treatment of secondary DES during the early follow-up period after refractive surgery may significantly reduce risks of tear dysfunction and neurotrophic epitheliopathy development in the long term.

[Changes in intraocular pressure after intravitreal injections]. / Izmeneniia urovnia VGD posle intravitreal'nykh in''ektsii.

At present, intravitreal drug injections are used for treatment of various diseases of posterior segment of the eye. Among its side effects is significant rise of intraocular pressure (IOP). PURPOSE: To study the changes in IOP levels after two intravitreal injections. MATERIAL AND METHODS: The study was performed on a random selection of 335 patients (335 eyes) diagnosed with choroidal neovascular membrane (CNVM). All the patients received intravitreal injections of ranibizumab according to medical indications. IOP was measured by rebound tonometer Icare-Pro (Icare, Finland) before intravitreal injection, as well as 1 minute, 30 minutes and 3 hours post-injection. Injection was repeated one months after the initial procedure. RESULTS: Intravitreal injection of additional liquid volume causes significant IOP rise, up to 38 mm Hg in average (confidence interval 30-45 mm Hg, p<0.05), with further tendency for IOP to self-normalize. After 30 minutes, IOP remained slightly higher than the initial level - 18 mm Hg (confidence interval 15-21 mm Hg, p<0.05). After 3 hours, IOP approached baseline level - 14 mm Hg (confidence interval 12-16 mm Hg, p<0.05). After the second injection, IOP was observed to decrease slower, causing more patients (28% compared to 21% after the first injection) to have IOP raised by 6 to 10 mm Hg from the initial level 30 minutes after the procedure. CONCLUSION: The revealed changes can serve as a pathophysiological model for studying changes of biometric parameters of anterior and posterior eye segments and biomechanical properties of fibrous tunic.

[Modern methods of treatment of amblyopia]. / Sovremennye metody lecheniia ambliopii.

Throughout the history of pediatric ophthalmology, pathophysiological state has always played an important role. It's characterized by reduced central vision, often paired with disruption of binocular vision, which is interpreted as amblyopia. Central vision is necessary for social integration, so its disorders cause great quality of life changes in patients limiting their professional activities and complicating everyday life. Despite large number of proposed methods of treatment, amblyopia still remains a pressing problem and its prevalence has not changed significantly over the years.

[Intraocular pressure, ocular blood flow, and corneal biomechanics changes after LASIK surgery for myopia]. / Vliyanie operatsii LASIK pri miopii na pokazateli oftal'motonusa, ob''emnogo glaznogo krovotoka i «biomekhaniki¼ rogovitsy.

AIM: to study changes in intraocular pressure (IOP), volumetric ocular blood flow (OBF) rate, and biomechanical properties of the cornea after excimer laser ablation in patients with myopia of different degrees. MATERIAL AND METHODS: A total of 16 patients (32 eyes) with myopia ranging from 2.75 to 9.0 D were examined before and after LASIK. Ocular Blood Flow Analyzer (OBFA) was used to measure IOP and OBF as well as pulse amplitude and volume. Ocular Response Analyzer (ORA) was also employed to provide the following data: Goldmann-equivalent IOP, corneal compensated IOP, corneal hysteresis, and corneal resistance factor. The eyes were then divided into two groups: group 1 - 15 eyes with less than 70-µm deep ablation of the cornea and group 2 - 17 eyes with more than 70-µm deep ablation. RESULTS: Group 1 demonstrated a statistically reliable decrease in IOP values provided by either method and biomechanical parameters of the cornea (p<0.005), but no difference in pre- and postoperative OBF, or pulse amplitude, or pulse volume (p>0.05). In group 2, all the parameters changed reliably, except for the pulse volume (p>0.05). In particular, a decrease was recorded for IOP (with no dependence to the method of measurement; p<0.001), pulse amplitude (p<0.01), corneal hysteresis (p<0.001), and corneal resistance factor (p<0.001); an increase - for OBF (p<0.05). CONCLUSION: One should allow for possible mismeasurement of IOP and OBF as well as biomechanical parameters of the cornea in post-LASIK patients, keeping in mind that the extent of error depends on the depth of ablation. Shallow ablation (no more than 70-µm deep) has no statistically significant effect on OBF readings, while IOP seems to decrease considerably. In deep ablation (more than 70-µm deep), both parameters are reliably lower than at baseline.

[Reasons to reconsider interpretation of densitometry for corneal transparency]. / O neobkhodimosti peresmotra interpretatsii dannykh densitometricheskoi otsenki prozrachnosti rogovitsy.

AIM: To assess the effect of light scattering in the corneal epithelium on densitometric brightness of the stroma through mathematical modeling of the interaction between a light beam and the two-layer epithelium-stroma system. MATERIAL AND METHODS: In order to study the scattering behavior of a plane-parallel non-coherent beam at the epithelium-stroma interface, a multi-age group was formed (87 patients, 174 eyes) that comprised two subgroups with equal number of assign participants: healthy patients with no systemic changes and mixed patients with undisturbed corneal transparency that, nevertheless, were under instillation therapy. In the first subgroup, the assessment of light scattering was done at random times, while in the second subgroup - within the first 200 seconds after the instillation in order to avoid a reaction of the ocular surface structures, including epithelium (rapid response of epithelial cells to instillations). Light scattering intensity was measured with Pentacam (USA). The densitometric curve and brightness maxima of the epithelium and neighboring stroma as well as the mid and upper stroma were recorded for each patient. RESULTS: A physico-mathematical model of the interaction between a light beam and the two-layer epithelium-stroma system was created. The study confirmed our theoretical CONCLUSION: on the effect size of light scattering intensity on the apparent densitometric brightness of the stroma. CONCLUSION: Direct densitometry of multilayered spherical objects, of which each layer possesses its own optical properties, has been proved inaccurate. Complex optical interactions in a multilayered model cause a false increase in brightness of more transparent layers that lie behind those with pronounced light scattering properties. The function that describes the false increase in scattering ability of the layer that is more transparent rises sharply at the border between the layers.

[Variability in biomechanical properties of the fibrous tunic of the eye in a healthy population].

UNLABELLED: Studying biomechanical properties of the fibrous tunic of the eye meets current clinical demands. Previous studies have proved bidirectional corneal applanation suitable for this purpose. The so called corneal elasticity coefficient is more informative in terms of corneal elastance than the two other parameters measured during bidirectional corneal applanation, namely, corneal resistance factor and corneal hysteresis. All three are known to have wide normal ranges. The aim of the present study was to determine the range of corneal resistance factor, corneal hysteresis, and corneal elasticity coefficient in a normal population. MATERIAL AND METHODS: This work summarizes data from 2205 patients (4410 eyes) with no ophthalmic pathology who got their ocular biomechanics examined with an Ocular Response Analyzer. RESULTS: Normal ranges of biomechanical parameters of the fibrous tunic have been determined. Considerable variation has been demonstrated in central corneal thickness (from 448 to 685 µm, with the mean of 563 ± 37 µm). Moreover, the corneal resistance factor, corneal hysteresis, and corneal elasticity coefficient have been shown to have almost equal means and to decrease with age.

[Long-term efficacy of corneal collagen cross-linking in patients with progressive keratoconus].

AIM: to study the efficacy of corneal collagen cross-linking in patients with progressive keratoconus over longer (up to 2 years) follow-up periods. MATERIAL AND METHODS: A total of 52 patients (104 eyes) aged 23-34 years with stage I-III progressive keratoconus were enrolled. Besides routine examinations (automatic refractometry, uncorrected and best corrected visual acuity (UCVA and BCVA) evaluation, pneumatic tonometry), Pentacam keratotopography and pachymetry ("Oculus", Germany) were performed in all cases. Corneal biomechanical properties were assessed with an Ocular Response Analyzer ("Reichert", USA). In all patients cross-linking procedure was carried out in the eye with more advanced keratoconus, the fellow eye being used as the control. RESULTS: Judging from the results of UCVA and BCVA evaluation, keratotopography, and pachymetry obtained 2 years after the standard corneal cross-linking procedure, stabilization has been achieved in 97% of cases. In the remaining 3% of eyes corresponding parameters declined, although to a lesser extent than in the controls. Indices describing biomechanical properties of the cornea, such as corneal hysteresis, corneal resistance factor, as well as elastonometry results did not differ significantly throughout the whole observation period, which agrees with literature data. CONCLUSION: Corneal collagen cross-linking has been proved capable of stopping keratoconus progression in most of the patients (97%). Further studies with even longer follow-up periods are needed.

[Clinical and experimental aspects of investigation of biomechanical properties of corneoscleral shell].

The article summarizes the results of long-term clinical and experimental studies on biomechanical properties of corneoscleral shell performed over the last few years in the Research Institute of Eye Diseases of the Russian Academy of Medical Sciences. A total of 2432 patients (4775 eyes) were assessed. Dynamic bidirectional pneumatic corneal applanation, dynamic pneumatic corneal impression, and elastotonometry were used for in vivo evaluation. A new method of biomechanical assessment--luminescent polariscopy--was studied experimentally. The findings allow correct judgment on biomechanical properties of fibrous tunic in norm and pathology, such as ectatic cornea, glaucoma or previous refractive surgery.

Experimental study on the mechanical strain of corneal collagen.

Currently, investigations of biomechanical properties of the fibrous tunic are becoming even more topical, especially for diagnosis of corneal ectatic disease, as well as correct interpretation of intraocular pressure (IOP) parameters, particularly in patients with prior surgery on cornea. The study principle is based on the ability of substances to change optical anisotropy depending on mechanical strain applied to them. An experimental set-up was constructed which allows assessment of polarization degree of light which is emitted during luminescence of strained collagen. The study was performed on 18 corneoscleral discs of chinchilla rabbit eyes at 15 and 50mm Hg pressure, among them in 6 cases before and after making radial incisions, and in 6 cases before and after conducting the mechanical cornea abrasions that were asymmetrical by depth until reaching the local zone of iatrogenic keratectasia. Corneal collagen mechanical strain mappings were formed on 3 experimental models (intact cornea, cornea post radial keratotomy and keratectasia) under intra-chamber pressure of 15 and 50mm Hg. Corneal collagen mechanical strain is evenly allocated in the intact cornea. After radial keratotomy the main mechanical loading was concentrated over the middle part of corneal periphery, particularly in the bottom of keratotomic incisions. The increased intra-chamber pressure made the strain rise in those models. Upon cornea abrasion the main straining is distributed within the thinning zone, and the increase of intra-chamber pressure only increases the load over residual stroma. A new principle of corneal biomechanical properties investigation based on assessment of degree of light polarization emitted during luminescence of strained collagen, has been proposed and experimentally tested.

[Fibrous tunic biomechanics and biometric indicies. Report 1. The impact of axial length, thickness and corneal curvature].

The degree of impact of several fibrous tunic biomechanical parameters on biomechanical indices was studied using multifactor correlation analysis. In patients with "normal" cornea corneal thickness was found to be the most significant factor influencing corneal hysteresis, corneal resistance factor, elasticity coefficient and elasticity rise, hence values of corneal biomechanical properties prevail over all other biomechanical indices studied in this work. However influence of significant changes in scleral biomechanics (e. g. in high myopia) on these factors (especially corneal hysteresis and elasticity rise) can not be excluded.

[Fibrous tunic biomechanics and biometric indicies. Report 2. The impact of topographic features in keratoconus].

The potential relation of biomechanical indices with topographic features in keratoconus was studied using multifactor correlation analysis. Topographic features in keratoconus were found to have influence on biomechanical measurements in the central zone of the cornea. If the zone of ectasia is distant from the central part of the cornea the central biomechanics can remain normal. Elasticity coefficient was found to be the most sensitive and keratoconus topography-dependent biomechanical index compared with other biomechanical parameters studied in this work.

[Efficacy of catalin eyed drops in age-related cataract agents].

The present investigation studied the efficacy of Catalin eye drops (Senju Pharmaceutical Co, Osaka, Japan) in patients with early senile cataract. An objective procedure for the densitometric analysis of lens transparency images with a Pentacam apparatus (Oculus GmbH, Germany) was used to assess the results of the investigation. Unlike the control group, the patients using Catalin had a lower optical density in the anterior and posterior cortical lens layers and beneath the posterior capsule in the first months of therapy. In the other lens layers, the transparency remained unchanged whereas in the controls it was increased throughout the follow-up.