Applanation tonometry estimates intraocular pressure (IOP) by quantifying the force needed to create a defined amount of deformation of the cornea (Goldmann tonometer) or by estimating the diameter of the circular contact area of the cornea and flat tonometer of defined load (Maklakov tonometer). The first simplest models of the applanation method for measurement of the IOP were based on approach, in which an eyeball is modelled as a thin-walled spherical liquid-filled soft shell with corneal biomechanical properties. It was usually supposed that these properties were the same for all patients. In this work numerical simulation have been carried out using finite element code ANSYS. The eye shell is modeled as two joint shells (cornea and sclera) with different mechanical properties. The results are obtained for numerous sets of parameters and were compared to clinical data. For statistics the measurements of IOP for both eyes of 120 patients before and one month after refractive surgery are used. All parameter of refractive surgery (depth, the width and the place of ablation -refractive surgery for myopia or hypermetropia) have effect on IOP reading obtained with both Goldmann and Maklakov tonometry. The results obtained by Goldmann tonometer are significantly more sensitive to all parameters of refractive surgery than those found with Maklakov tonometer with load 10 g. Actuality of the topic. Materials and methodsIntraocular pressure (IOP) is one of the most important characteristics of a live eye. For half a century the Goldman tonometer was considered to be one of the most reliable classical methods of intraocular pressure measurements. Still presently one can find many works, discussing the sensitivity of measurements by Goldman tonometer in accordance with the central cornea thickness (see [1]). This dependence can be especially visible after keratorefracting surgeries (see [2]). Standardization of IOP measurements and examination of the effect of different parameters of the eyeball onto the value of intraocular pressure are among urgent questions today.Applanation tonometer to the Goldmann tips estimates IOP by quantifying the force needed to generate a defined amount of deformation of the cornea. Maklakov tonometer estimate the diameter of the circular contact area of the cornea and flat tonometer of defined load. Both Goldmann tonometer and Maklakov tonometer can be described by the same mathematical model. One of the models for IOP measurement by the Maklakov method was presented in [3]. The shell of eye was modeled by two spherical segments, the cornea was treated as a soft membrane. Under these assumptions deformation of the cornea is described as well as it was initially assumed in the applanation tonometry, by the relation p = W/S, where p means IOP, W means the weight of the tonometer, and S means the area of the contact zone. The calculations presented in [3] for different parameters of cornea and sclera give results, which correspond well to the data presented in calibration tables, and depend j...

Purpose To investigate CCT and IOP in myopic adult Chinese and to estimate its relationship with age, refraction, sex before excimer surgery in Eye Department of Daqing People’s Hospital (the 5‐th Affiliated Hospital of Harbin Medical University). Methods We studied a series of 402 healthy eyes of 201 patients (76 male /37.8%/, 125 female /62.2%/) who underwent excimer surgery for the correction of myopia with the sphere up to ‐13.5.0 D and the cylinder to ‐4.50 D. All ophthalmic investigations were made including pneumotonometry (“”Canon” TX‐10 and T‐F) and ultrasound (US‐) corneal pakhymetry with CCT‐measurements (“Nidek” UP‐1000). We performed accurate statistical analysis by using “Statistica” program. Results The age of our patients was 26.5+/‐6.3 years. UCVA and BCVA of all patients were 0.13+/‐0.09 and 0.97+/‐0.09 consequently. The results showed that mean US‐CCT of our male patients was 548.03+/‐29.12 microns. But mean CCT of our female patients was 537.77+/‐32.09 microns, 10.26 microns less than that of male patients (p<0.01). The mean IOP of male participants was 16.23+/‐2.94 mm Hg, and mean IOP of female participants was 14.82+/‐2.74 mm Hg (p<0.01). Conclusion Our results confirmed some data (P. Li et al., 2006) that mean US‐CCT of male patients was statistically significant more than such measurements in female ones in myopic adult Chinese. We revealed that pneumotonometric IOP was positively related to US‐CCT (r>0.85). None of the authors has no financial interest in this work.

Purpose To estimate the visual and refractive outcomes of simultaneous bilateral PRK (FAREK) for the correction of difficult cases of high myopia with steepest and very thin cornea in Chinese patients. Methods We studied a series of 38 eyes of 19 patients who underwent simultaneous bilateral PRK (FAREK) for the correction of myopia with the sphere up to ‐15.6 D and the cylinder to ‐2.75 D in difficult cases with the steepest and very thin cornea. Coefficient K2 was up to 49,0D and central corneal thickness was 504.3+/‐33.5 microns. Simultaneous bilateral PRK by using Mytomicin C, soft contact lenses, cooling effects was performed by Russian surgeons with the NIDEK EC‐5000. Follow‐up period was up to 3 months. The age of our patients was 25.2+/‐5.3 years. Pre‐op UCVA and BCVA were 0.12+/‐0.10 and 0.94+/‐0.14 consequently. Results Day of epithelization was 3.3+/‐0.8. Post‐op UCVA was 0.48+/‐0.18 in the epithelization’ day, 0.63+/‐0.21 in the first week, 0.79+/‐0.25 in the first month and 0.89+/‐0.25 in the third month after FAREK. Pre‐op IOP was 13.9+/‐2.9 mm Hg. Post‐op IOP was 8.2+/‐1.8 in the epithelization’ day, 7.8+/‐1.6 in the first week, 9.7+/‐2.2 in the first month and 10.0+/‐2.3 in the third month. UCVA was equal or more than 1.0 in 2.6% in the epithelization’ day, 13.8% in the first week and 41.6% in the first month after FAREK. There were no serious complications including hypertensions in all cases. Conclusion We called our method FAREK – fast recovery excimer keratectomy. FAREK is a safe, reliable and effective method for the correction of difficult cases of high myopia with steepest and very thin cornea in Chinese patients. None of the authors has no financial interest in this work.

Purpose To investigate the results of LASIK surgery for myopia in Chinese patients in Joint Russian‐Chinese Ophthalmic Center. Methods We reviewed our consecutive 296 cases (148 chinese patients, including 92 women and 56 men) of LASIK surgery for myopia with the sphere from ‐1.0 to ‐13.5 D and the cylinder till ‐4.5 D. LASIK was performed by Russian surgeons with the NIDEK EC‐5000 excimer laser and microkeratomes LSK Evolution‐2 (“Moria”). Follow‐up period was up to 3 months. The age of our patients was 26.7+/‐6.2 years. Pre‐op UCVA and BCVA were 0.13+/‐0.08 and 0.97+/‐0.08 consequently. All patients had standard ophthalmic examinations, including pneumotonometry, refractometry etc. We performed statistical analysis by using "Statistica" programm. Results Ablation depth was 89.3+/‐24.5 microns, ablation time was 47.53+/‐15.26 sec. Post‐op UCVA was 0.85+/‐0.24 in the first day, 0.97+/‐0.23 in the first week, 1.05+/‐0.20 in the first month and 1.10+/‐0.11 in the third month after LASIK. Pre‐op IOP was 15.6+/‐2.9 mm Hg. Post‐op IOP was 10.2+/‐2.7 in the first day, 10.5+/‐2.5 in the first week, 10.7+/‐2.9 in the first month and 9.1+/‐2.6 in the third month. UCVA was equal or more than 1.0 in 51.0% in the first day, 71.1% in the first week and 79.1% in the first month after LASIK. There were no serious complications in all cases. Conclusion The results of LASIK surgery for myopia in Chinese patients in the Joint Russian‐Chinese Ophthalmic Center were effective and successful. LASIK surgery by using NIDEK EC‐5000 excimer laser gives predictable and good results in Chinese patients. None of the authors has no financial interest in this work.