[Corneal changes in Fuchs endothelial corneal dystrophy and bullous keratopathy]. / Izmeneniya rogovitsy pri endotelial'noi distrofii Fuksa i vtorichnoi bulleznoi keratopatii.

OBJECTIVE: Evaluation of structural and immunohistochemical features of cornea in Fuchs endothelial corneal dystrophy (FECD) and bullous keratopathy (BK). MATERIAL AND METHODS: Group 1 - 44 patients (46 eyes) with FECD, group 2 - 42 patients (42 eyes) with BK. All patients underwent keratoplasty. Preoperative anterior segment optical coherence tomography (AS-OCT, RTVue-100, Optovue, USA) was performed. Endothelium-Descemet membrane (EDM) complexes, corneal buttons were obtained intraoperatively. Morphological (H&E staining) and immunohistochemical (primary antibodies to pancytokeratin, vimentin, fibronectin) studies were performed at the light microscope level (Leica DM-2500, Leica Application Suite V4.8, Leica Microsystems, Switzerland). RESULTS: A direct correlation is found between the results of DM analysis in vivo with OCT and ex vivo with light microscopy. DM thickness (AS-OCT) was significantly greater in FECD (23.0 [19.0; 27.0] µm), than in BK (13.0 [12.0; 14.0] µm). Morphological study of EDM and corneal buttons showed similar difference in DM thickness: 17.9 [16.1; 20.0] µm in FECD and 11.9 [11.3; 13.0] µm in BK. Irregular optical density of stroma is a feature of edema and local fibrosis. In FECD and BK pancytokeratin is expressed in epithelial and endothelial cells, vimentin - in keratocytes, macrophages and vascular endothelium, fibronectin - in DM. In FECD, vimentin is expressed in endothelial cells. CONCLUSION: FECD and BK are associated with different DM' and endothelium' abnormalities, which lead to similar changes of stroma and epithelium. AS-OCT is a useful method of FECD and BK in vivo diagnostics and the selection of treatment option.

Assessing Corneal Endothelial Damage Using Terahertz Time-Domain Spectroscopy and Support Vector Machines.

The endothelial layer of the cornea plays a critical role in regulating its hydration by actively controlling fluid intake in the tissue via transporting the excess fluid out to the aqueous humor. A damaged corneal endothelial layer leads to perturbations in tissue hydration and edema, which can impact corneal transparency and visual acuity. We utilized a non-contact terahertz (THz) scanner designed for imaging spherical targets to discriminate between ex vivo corneal samples with intact and damaged endothelial layers. To create varying grades of corneal edema, the intraocular pressures of the whole porcine eye globe samples (n = 19) were increased to either 25, 35 or 45 mmHg for 4 h before returning to normal pressure levels at 15 mmHg for the remaining 4 h. Changes in tissue hydration were assessed by differences in spectral slopes between 0.4 and 0.8 THz. Our results indicate that the THz response of the corneal samples can vary according to the differences in the endothelial cell density, as determined by SEM imaging. We show that this spectroscopic difference is statistically significant and can be used to assess the intactness of the endothelial layer. These results demonstrate that THz can noninvasively assess the corneal endothelium and provide valuable complimentary information for the study and diagnosis of corneal diseases that perturb the tissue hydration.

[Imaging features of posterior polymorphous corneal dystrophy observed by in vivo confocal microscopy].

Objective: To identify and analyze imaging features of posterior polymorphous corneal dystrophy (PPCD) by in vivo confocal microscopy (IVCM). Methods: This retrospective case series enrolled 27 eyes of 18 patients (including 10 males and 8 females) who were diagnosed with PPCD at the Department of Ophthalmology in Peking University Third Hospital between January 2013 and December 2019. The mean age was (23.61±14.81) years. There were 9 monocular and 9 binocular cases. All patients were examined by slit-lamp biomicroscopy and IVCM. The visual acuity, the mean endothelial cell density, and the images of IVCM were analyzed in all cases. Results: The mean best-corrected visual acuity was 0.76±0.33, and the mean endothelial cell density was (1 723.6±698.3) cells/mm2. The IVCM images of type 1 PPCD (vesicular lesions) showed hyperreflective, placoid or homocentric lesions at the level of the Descemet's membrane, hyporeflective, oval or round lesions at the level of the Descemet's membrane, and hyporeflective, crater-like lesions at the level of the endothelial cell layer. The IVCM images of type 2 PPCD (band lesions) displayed hyperreflective, band lesions and a fibrous strand structure at the level of the Descemet's membrane, hyporeflective, vesicular lesions at the level of the Descemet's membrane, and hyporeflective, trough-and ridge-like lesions at the level of the endothelial cell layer. The IVCM images of type 3 PPCD (geographic placoid opacities) showed loss of the hexagonal features of endothelial cells and epithelial-like cell transformation. Conclusions: PPCD primarily affects the endothelium and Descemet's membrane. IVCM could highlight the special characteristics of PPCD including hyperreflective lesions at the level of the Descemet's membrane, hyporeflective lesions at the level of the endothelial cell layer, and epithelial-like cell transformation of endothelial cells. IVCM is an invaluable tool for clinical diagnosis and dynamic monitoring of PPCD.

Lack of association between obstructive sleep apnea syndrome and specular microscopic features of the corneal endothelium.

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent episodes of hypoxemia and hypercapnia during sleep. The aim of this study was to determine whether OSAS causes significant changes in corneal endothelium detectable by specular microscopy. METHODS: This prospective, cross-sectional study compared the specular microscopic features of the corneal endothelium of patients with OSAS and age-and gender-matched controls. Patients diagnosed with OSAS by polysomnography in the sleep unit were classified using apnea-hypopnea indexes into two groups as mild-moderate OSAS group and severe OSAS group. All participants were divided into three age groups: 30-45, 46-60, and > 60 years. Corneal endothelial cell density (ECD), percentage of hexagonal cells (Hex), and coefficient of variation of cell area (CV) were obtained using a non-contact specular microscope. The measurements of each group were compared statistically. RESULTS: A total of 66 patients (51.1 ± 9.4 years) and 88 controls (49.2 ± 10.5 years) were examined. The mild-moderate OSAS group and the severe OSAS group had no significant differences in measures of specular microscopy compared with the controls (ECD, p = 0.84; Hex, p = 0.18; CV, p = 0.41). The mean values of ECD, Hex, and CV were 2552.56 ± 302.49 cells/mm2, 54.13 ± 8.13%, and 36.41 ± 5.92, respectively, in the mild-moderate OSAS group; 2510.52 ± 377.12 cells/mm2, 54.85 ± 8.68%, and 34.77 ± 5.02, respectively, in the severe OSAS group; 2543.37 ± 286.94 cells/mm2, 51.89 ± 9.09%, and 36.03 ± 5.32, respectively, in the control group. CONCLUSIONS: There were no significant differences in corneal endothelial features between patients and controls. Although OSAS causes systemic hypoxia, its effects do not appear to result in corneal endothelial alterations detectable by specular microscopy.

The effect of smoking on corneal densitometry and endothelial cell morphology.

PURPOSE: We investigated corneal endothelial morphology and corneal densitometry in smokers and compared our results with findings observed in non-smokers. MATERIALS AND METHODS: This cross-sectional observational study included 100 participants (50 smokers, 50 non-smokers) aged 18-80 years in whom corneal endothelial morphology was analysed using a non-contact Tomey EM-4000 specular microscope (Tomey Corporation, Japan). The Pentacam HR system was used to measure corneal densitometry spatially in three concentric zones (from the centre to the periphery) and at three different corneal depths (from the anterior to the posterior aspects). Endothelial morphology findings and corneal densitometry values were recorded in all participants, and these results were compared between smokers and non-smokers. RESULTS: Endothelial morphology and corneal densitometry analysis showed significantly lower endothelial cell counts (Num) in smokers (228 cells/mm2 vs. 246 cells/mm2, p = 0.02) in addition to increased maximum cell area (Max) values (986.5 µm2 vs. 935 µm2, p = 0.04). We observed no statistically significant intergroup difference in corneal densitometry values (p > 0.05 for each zone); however, we observed a moderately positive correlation between densitometry values in the 6-10 mm concentric zone and between the all total corneal zones and number of pack-years in smokers. CONCLUSIONS: Our study highlights that among the morphometric corneal endothelial variables analysed in this study, only the Num value was significantly correlated with smoking. We observed no statistically significant intergroup difference in corneal densitometry values in this study; however, a positive correlation was observed between the number of pack-years and corneal densitometry findings. Therefore, as the pack-years increase, the increase in corneal densitometry values may indicate a decrease in corneal clarity, considering the possible contribution of secondary factors such as age.

Corneal endothelial cell density in patients receiving chemotherapy.

PURPOSE: This study aimed to determine if the corneal endothelium was affected by chemotherapy. METHODS: Chemotherapy patients were recruited to undergo specular microscopy before treatment and again at 1- and 2-year follow-up visits. One eye per patient, per follow-up, was selected for comparison to baseline. RESULTS: Forty-six volunteers completed baseline and at least one follow-up assessment. From 51 eyes, there was no significant change in endothelial cell density for 41 eyes assessed at one year (MD = 0.73%, 95% CI -1.33 to 2.78%) and 18 eyes at two years (MD = 0.31%, 95% CI -3.53 to 4.15%). CONCLUSION: Although other studies have shown that chemotherapy can adversely affect the corneal epithelium, this study showed no measurable change in endothelial cell density.

Evaluation of corneal safety in systemic lupus erythematosus patients undergoing long-term hydroxychloroquine treatment.

PURPOSE: The aim of this study was to examine the effects of long-term use of hydroxychloroquine (HQ) on the pachymetric, aberrometric, and densitometric values of the cornea and corneal endothelium in lupus patients. METHOD: Twenty-two eyes (study group) of 22 patients using HQ for treatment of lupus and 25 eyes (control group) of 25 healthy individuals were included in this prospective study. A specular microscopy was used to measure corneal endothelial cell density (ECD), percentage of hexagonal cells (HEX%), coefficient of variation of the cell size (CV). Then, a Pentacam® HR corneal tomography system was used to measure central corneal thickness (CCT), corneal aberrometry values in 6-mm pupil diameters and corneal densitometry values in 6-mm corneal zones (0-2 mm and 2-6 mm). RESULTS: While ECD was significantly lower in the study group than in the control group (p = 0.034), CCT was significantly higher in the study group (p = 0.032). The higher-order aberrations values and the anterior corneal densitometry values in the 0-2 mm and 2-6 mm corneal zones in the study group were found to be significantly higher than the control group (p = 0.021, p = 0.007 and p = 0.013). CONCLUSION: Prolonged use of HQ may cause some changes in the cornea. In the follow-up of these cases, detailed examination of the cornea as well as the macula may be important for the protection of corneal health.

The findings of corneal specular microscopy in patients with type-2 diabetes mellitus.

BACKGROUND: We aimed to compare the morphological characteristics of corneal endothelial cells in type 2 diabetic patients and age-matched healthy subjects by specular microscopy. We also aimed to determine the association of corneal morphological features with the general characteristics and laboratory data of diabetic patients, including disease duration, haemoglobin A1c (HbA1c) levels and urine albumin creatinine ratio. METHODS: A total of 195 diabetic patients and 100 healthy controls were enrolled in the study. All participants underwent a complete ophthalmological examination. Corneal endothelial measurements were performed using a noncontact specular microscopy. Laboratory data including serum fasting glucose, haemoglobin A1c levels, creatinine levels, and the urinary albumin-to-creatinine ratio were recorded. Diabetic patients were further subdivided into 3 groups according to the presence and stage of diabetic retinopathy. Specular microscopy findings and central corneal thickness of all patients were compared. RESULTS: The ECD and hexagonal cell ratio were significantly lower, while the average cell size, CV%, and central corneal thickness were determined to be significantly higher in diabetic patients than in healthy controls (p = 0.001). With the presence and advancement of diabetic retinopathy, the ECD and hexagonal cell ratio decreased, while the average cell size, CV%, and central corneal thickness increased. When correlation analysis was performed between corneal morphological features and laboratory data of diabetic patients, ECD showed a significant negative correlation with diabetes duration (p = 0.028). HbA1c levels, urinary albumin-creatinine ratio (p = 0.041), average cell size and CV showed a positive correlation with these parameters. CONCLUSION: In conclusion, keratopathy is an important complication of type 2 diabetes. With an increase in the stage of diabetic retinopathy, alterations in corneal findings also increased. In that respect, we can suggest that keratopathy should be evaluated more cautiously in diabetic patients.

[Imaging features of Fuchs endothelial corneal dystrophy].

Objective: To investigate the imaging features of Fuchs endothelial corneal dystrophy (FECD) and to provide imaging evidence for the diagnosis of this disease. Methods: Retrospective case series study. A total of 128 eyes (64 patients, including 19 males and 45 females) diagnosed with FECD at the Beijing Tongren Eye Center of Capital Medical University from January 2014 to December 2016 were enrolled. The average age was 57.8±12.9 years. There were 25 eyes of stage Ⅰ (19.5%), 81 eyes of stage Ⅱ (63.3%), 16 eyes of stage Ⅲ (12.5%) and 6 eyes of stage Ⅳ (4.7%).All patients underwent specular microscopy, and 41 patients (82 eyes) had in vivo confocal microscopy (IVCM). The patients' general data, clinical stage, and image features of specular microscopy and IVCM were analyzed. The enumeration data was compared by chi-square test. Differences of measurement data were compared by ANOVA. Data which cannot be accurately measured was compared by rank sum test. Results: As the disease progressed, the number, incidence rate, and fusing rate of dark"holes"on specular microscopy increased. The number of guttata on IVCM increased, and the fusing pattern of guttata developed from pair-like, chain-like to group-like. On specular microscopy, the mean rank of stage Ⅰ (78.2), stage Ⅱ (228.4), stage Ⅲ (284.5) and stage Ⅳ (288.5) was statistically different (χ²=84.183, P=0.000). All positions of all eyes of stage I had no fusion of the dark "holes". The incidence of fusion on the peripheral cornea gradually increased significantly (χ²=27.167, P=0.000) from stage Ⅱ (45.1%, 146/324), stage Ⅲ (76.3%, 45/59) to stage Ⅳ (83.3%, 15/18). Conclusions: The imaging features of specular microscopy and IVCM can be applied as an important basis for early diagnosis of FECD. Specular microscopy is a practical method for rapid screening of FECD. IVCM is an important imaging basis for clarifying the appearance of guttata and analyzing fusion features, so as to guide the differentiation of stages. (Chin J Ophthalmol, 2020, 56:938-943).

Vulnerability of corneal endothelial cells to mechanical trauma from indentation forces assessed using contact mechanics and fluorescence microscopy.

Corneal endothelial cell (CEC) loss occurs from tissue manipulation during anterior segment surgery and corneal transplantation as well as from contact with synthetic materials like intraocular lenses and tube shunts. While several studies have quantified CEC loss for specific surgical steps, the vulnerability of CECs to isolated, controllable and measurable mechanical forces has not been assessed previously. The purpose of this study was to develop an experimental testing platform where the susceptibility of CECs to controlled mechanical trauma could be measured. The corneal endothelial surfaces of freshly dissected porcine corneas were subjected to a range of indentation forces via a spherical stainless steel bead. A cell viability assay in combination with high-resolution fluorescence microscopy was used to visualize and quantify injured/dead CEC densities before and after mechanical loading. In specimens subjected to an indentation force of 9 mN, the mean ±â€¯SD peak contact pressure P0 was 18.64 ±â€¯3.59 kPa (139.81 ±â€¯26.93 mmHg) in the center of indentation and decreased radially outward. Injured/dead CEC densities were significantly greater (p ≤ 0.001) after mechanical indentation of 9 mN (167 ±â€¯97 cells/mm2) compared to before indentation (39 ±â€¯52 cells/mm2) and compared to the sham group (34 ±â€¯31 cells/mm2). In specimens subjected to "contact only" - defined as an applied indentation force of 0.65 mN - the peak contact pressure P0 was 7.31 ±â€¯1.5 kPa (54.83 ±â€¯11.25 mmHg). In regions where the contact pressures was below 78% of P0 (<5.7 kPa or 42.75 mmHg), injured/dead CEC densities were within the range of CEC loss observed in the sham group, suggesting negligible cell death. These findings indicate that CECs are highly susceptible to mechanical trauma via indentation, supporting the established "no-touch" policy for ophthalmological procedures. While CECs can potentially remain viable below contact pressures of 5.7 kPa (42.75 mmHg), this low threshold suggests that prevention of indentation-associated CEC loss may be challenging.

Morphological analysis of corneal findings modifications after death: A preliminary OCT study on an animal model.

The aim of this work was to describe, for the first time, the morphological modifications, in a three-dimensional mode, of the central cornea at different intervals since death. The study design involved the analysis of 30 eyes (15 heads) of female, adult sheep (>2 years) sacrificed at a local slaughterhouse. The eyes, after animal decapitation, were examined in situ, without enucleation. Ocular globes were stored at well-known temperature (within a range of 12-22 °C) and humidity (within a range of 50-60%). The instrumental analysis was executed using a portable spectral-domain OCT (SD-OCT) system (iVue SD-OCT, Optovue Inc, Fremont, CA) calibrated to the corneal mode. OCT imaging was performed at different time-points since death. Pachymetric map, morphological and ultrastructural analysis (epithelium, stroma, and endothelium), were performed for each time-point. After an initial thinning of tissues and an enhancement of epithelial reflectivity, stromal thickness increased from the 2nd up to the 6th hour. Subsequently, a new trend incorneal thinning was observed in association with the appearance ofone or more demarcation lines between the anterior andposterior stroma. After the 12th hour, a recurrence of corneal swelling was detected in association with thedelamination of stromal tissue. Since the 24th hour, the epithelium disappeared in 50% of cases and the anterior chamberdepth progressively decreased. At the 48th hour, various ocular structures showed the onset of putrefaction processes, such as theappearance of hyper-reflective dots in anterior chamber, iridocorneal contact, and the massive vacuolization of theposterior stroma until the total delamination. The portable OCT system is a useful approach for in situ postmortem corneal examination, and it may be potentially applied for the selection of donor cornea in transplantology and for the determination of post-mortem intervals in forensic medicine.

Scheimpflug Camera Measurement of Optical Density of the Corneal Epithelium, Stroma, and Endothelium in Patients with Pseudoexfoliation Syndrome.

BACKGROUND The present study evaluated the optical density of particular layers of the cornea and anterior lens capsule in patients with pseudoexfoliation syndrome (PEX). MATERIAL AND METHODS Sixty patients with cataract and PEX (mean age 76.6±5.6 years, range 62-88 years) were compared to 55 controls with cataract without PEX syndrome (mean age 76.3±6.09 years, range 62-90 years; P>0.05). The anterior segment of one eye was examined in each patient using Pentacam HR by Oculus before the planned cataract surgery. RESULTS The average optical density of the corneal epithelium, stroma, and endothelium was 25.3±6.09% and 19.9±3.41% (P<0.001), 23.1±5.5% and 19.2±3.6% (P<0.0001), and 14.6±3.4% and 12.3±2.1% (P<0.0001) in the PEX and control groups, respectively. The optical density of the anterior lens capsule was 13.6±4.2% in the PEX group and 9.74± 2.23% in the control group (P<0.0001). The average thickness of the cornea was 555 µm and 556 µm and the average optical density of endothelial cells 2240/mm² and 2323/mm² in the PEX and control groups, respectively (P<0.05). CONCLUSIONS In patients with PEX, increased optical density was observed not only in the structures with pseudoexfoliative material detectable by a slit-lamp), but also in the corneal epithelium and stroma. The increased optical density was not associated with reduced endothelial cell density or increased central cornea thickness.

Assessment of the safety and efficacy of primary retropupillary fixation of iris-claw intraocular lenses in children with large lens subluxations.

PURPOSE: To evaluate whether retropupillary fixation of the iris-claw intraocular lens (IOL) is a safe and effective treatment option in children with large lens subluxations. METHODS: Fourteen eyes of children between the ages of 8-17 years with lens subluxations more than 7 clock hours underwent pars plana lensectomy-vitrectomy with implantation of the iris-claw IOL in the retropupillary position as a primary procedure. The best corrected visual acuity (BCVA), intraocular pressure (IOP), corneal endothelial count (EC) and the lens position using ultrasound biomicroscopy (UBM) were assessed pre- and postoperatively. RESULTS: Postoperatively, all patients had an increase in the BCVA with a mean of 0.351 ± 0.154 log MAR units which was statistically significant as compared to the preoperative value of 0.771 ± 0.132 log MAR units (p = 0.003). The difference between the mean preoperative IOP (13.642 ± 2.437 mmHg) and the mean postoperative intraocular pressure at the end of 6 months (13.5 ± 2.244 mmHg) was not statistically significant (p = 0.671). The mean EC decreased by 0.99% from 2838.42 ± 474.76 cells/mm2 preoperatively to 2810 ± 461.24 cells/mm2 at the end of 6 months postoperatively (p = 0.117). The lens position was analyzed using UBM and was found to be parallel to the iris plane in all cases at the end of 6 months. CONCLUSIONS: Our study shows that primary retropupillary iris-claw IOL implantation can be a safe and efficacious option for children with large (>7 clock hours) lens subluxations that is at least comparable to scleral-fixated PCIOLs.

Measurements of donor endothelial keratoplasty lenticules prepared from fresh donated whole eyes by using ultrasound and optical coherence tomography.

This study was conducted to analyze the profile and thickness of endothelial keratoplasty lenticules prepared from fresh donated whole eyes with Visante optical coherence tomography (V-OCT) compared to measurements obtained from ultrasound pachymetry (USP) at the Central Eye Bank of Iran. Microkeratome-assisted precut corneas were prepared for Descemet stripping automated endothelial keratoplasty by using standard eye bank protocol. Central posterior lenticule thickness (CPLT) on fresh whole eye, before excising corneoscleral disc and transferring to Optisol-GS, was measured by USP. V-OCT was used to measure central, paracentral, and midperipheral thicknesses of lenticules after transferring the tissue to Optisol-GS. Chi Square and Bonferroni tests were respectively used to uncover the differences between the USP and V-OCT measurements and also the thickness profile of lenticules. Postoperative reports for the entire transplanted lenticules were recorded. Accordingly, on evaluation of 312 enrolled precut corneas, CPLT measurements by V-OCT versus USP were statistically different (mean: 136 µm vs 165 µm, respectively; P = 0.008). Thickness profile of the posterior lenticules revealed increased thickness from the central to the peripheral parts of the cornea (mean increase of 16 µm at the pericentral and 64.2 µm at the peripheral locations, respectively); however, the increase in the thickness was relatively symmetrical. Postoperative reports of transplanted lenticules were unremarkable, since there were no posterior flap detachments. In essence, V-OCT measurements of microkeratome-assisted precut lenticules prepared from fresh donated whole eyes averaged 29 µm thinner than USP measurements and revealed a significant but symmetric increase of thickness towards the peripheral parts of the corneas. However, the variation in the thickness profile did not affect the attachment or the clarity of transplanted precut lenticlues.

[Objective assessment of donor material for penetrating corneal transplantation]. / Ob''ektivizatsiia otsenki donorskogo materiala dlia skvoznoi peresadki rogovitsy.

Reliable suitability evaluation of donor material is the crucial issue of penetrating corneal transplantation. The main parameter to be considered is endothelial cell density (ECD). However, when it comes to practice, one has to admit significant variation in ECD readings of cadaver corneas obtained by different methods. AIM: to investigate discrepancies in ECD measurements and to define objective criteria for the evaluation of a donor cornea before full-thickness grafting. MATERIAL AND METHODS: In a hundred cadaver eyes, discrepancies in ECD measurements by different methods (specular microscopy, confocal microscopy, and keratoanalyzer) were studied and objective evaluation criteria developed along with an optimal algorithm of pretransplantation assessment. Digital fluorescence microscopy was chosen as the reference method. RESULTS: It has been established that a triple measurement average obtained with any of the tested methods is informative enough as to the state of the donor cornea. CONCLUSION: The highest ECD values were obtained with specular microscopy, the lowest - with confocal microscopy. For reliable evaluation of donor corneas, we recommend that the average of a triple ECD measurement be taken using one of the mentioned methods.

[Influence of endothelial graft thickness on postoperative visual acuity]. / Otsenka vliianiia tolshchiny éndotelial'nogo transplantata na posleoperatsionnuiu ostrotu zreniia.

AIM: to assess the influence of the endothelial graft thickness on postoperative visual acuity following modified endothelial keratoplasty (UTDSAEK). MATERIAL AND METHODS: The study included 49 patients with pseudophakic bullous keratopathy and no concomitant disorders of either the retina or optic nerve. Ultrathin Descemet's stripping automated endothelial keratoplasty (UTDSAEK) was performed in all cases. Corneal graft thickness was measured 1 year after UTDSAEK by means of optical coherence tomography. Postoperative visual acuity values were compared in patients with the endothelial graft thickness from 51 to 98 microns (27 eyes) and those with the endothelial graft thickness from 102 to 121 microns (22 eyes). The dynamics of the graft thickness change after surgery was also assessed. RESULTS: The thickness of the graft gets reduced by an average of 21% over the first 2-3 weeks after UTDSAEK and by approximately 5% over 2 more months. For the next few years it remains relatively stable (the maximum follow-up period was 5 years). The study showed no statistically significant difference in visual acuity between two groups of patients with the endothelial graft thickness of less than and greater than 100 microns (p=0.7). CONCLUSION: The thickness of the endothelial graft for UTDSAEK has no statistically significant effect on postoperative visual acuity. The optimal thickness of the graft being cut out lies in the range from 100 to 150 microns. Such grafts adapt well to the posterior surface of the recipient cornea with no significant changes to its topography. Moreover, thicker grafts are easier manipulated before insertion into the anterior chamber and are associated with a lower risk of perforation during acquisition as compared to grafts of under 100 microns.

Visualization of precut DSAEK and pre-stripped DMEK donor corneas by intraoperative optical coherence tomography using the RESCAN 700.

BACKGROUND: To report the feasibility of intraoperative spectral domain optical coherence tomography (OCT) using the RESCAN 700 for the visualization and evaluation of precut Descemet's stripping automated endothelial keratoplasty (DSAEK) and prestripped Descemet's membrane endothelial keratoplasty (DMEK) donor tissue. METHODS: Precut DSAEK (n = 11), prestripped DMEK (n = 4) preserved in a viewing chamber were examined by intraoperative OCT. Wholly intact donor corneas for penetrating keratoplasty (PK) (n = 8) were also examined as controls. The obtained images were analyzed qualitatively for characteristics of each type of donor. RESULTS: For each type of donor, characteristic images were consistently obtained by intraoperative OCT in both the front and back views through the viewing chamber. In wholly intact donors for PK, appearance of normal corneal curvature and stromal texture with high reflectivity of epithelium and endothelium cell layers were clearly visualized. In precut DSAEK donors, precut lines were characteristically visualized in addition to the intact donor cornea images. In prestripped DMEK donors, identical OCT images to the intact donor cornea were noted when observed from the anterior surface. However, peripheral partial detachments of Descemet's membrane were characteristically observed in all prestripped DMEK donors when viewed from the back of the viewing chamber. CONCLUSION: Rapid visualization and rough evaluation of donor tissues for PK, precut DSAEK and prestripped DMEK donor corneas by intraoperative OCT was consistently possible through the viewing chamber. Therefore, this device may be used as an alternative of AS-OCT when the eyebank does not have their own AS-OCT. Although the peripheral detachment in DMEK donors are quite common and clinically non-problematic in DMEK donor quality and subsequent DMEK surgeries, it may be useful to distinguish between wholly intact PK donors and prestripped DMEK donors, enabling to prevent mix-ups of donors, especially when several different types of keratoplasties are scheduled in a same day in one operating theater.

Effects of Glaucoma Tube Surgery on Corneal Endothelial Cells: A Review.

The etiology of corneal decompensation after aqueous shunt implantation remains poorly understood. With the use of anterior segment optical coherence tomography and specular microscopy, the relationship of these implants to the surrounding tissues can be investigated over time. This article will review the current knowledge pertaining to endothelial cell loss related to glaucoma and surgery and highlight possible causes that have been proposed for endothelial cell loss after aqueous shunt implantation.

[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.