Comparison between laser scanning in vivo confocal microscopy and noncontact specular microscopy in assessing corneal endothelial cell density and central corneal thickness

Modified Method for Nanothin Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

The purpose of this study was to describe a method to achieve a high success rate for nanothin (NT, ≤50 μm) Descemet stripping automated endothelial keratoplasty (DSAEK) graft preparation using anterior chamber pressurizer (ACP) with a modified setting and evaluate its postoperative efficacy.

METHODS

A prospective cohort (study group) of 24 patients with corneal endothelial dysfunction was consecutively enrolled and received DSAEK grafts using the modified ACP method from December 2021 to May 2022. The control group included 24 historical patients who received DSAEK grafts using conventional ACP procedure. Central graft thickness (CGT), graft regularity (3-mm and 5-mm diameter zones), best spectacle-corrected visual acuity, and endothelial cell density (ECD) were compared between 2 groups.

RESULTS

A 100% ultrathin (UT, ≤100 μm) DSAEK rate and 62.5% NT-DSAEK rate was achieved at 3 months postsurgery in the study group, with a 51.3 ± 14.8 μm CGT, while a 70.8% UT-DSAEK rate and 4.2% NT-DSAEK rate was achieved in the control group, with an 89.0 ± 15.4 μm CGT ( P <0.001). At 3-month postoperative follow-up, the regularity of graft thickness was significantly better in the study group (central-to-peripheral thickness difference: P = 0.044 and 0.014 for 3-mm and 5-mm diameter zones, respectively, graft thickness uniformity: P <0.001 and 0.012, respectively). There was no statistical difference in the best spectacle-corrected visual acuity ( P = 0.170) or ECD ( P = 0.833) between 2 groups at 3-month postoperative follow-up.

CONCLUSIONS

DSAEK grafts harvested using modified ACP method were thinner and more regular compared with the conventional ACP method.

Impact of postoperative intraocular pressure elevation on graft endothelial cells in non-preexisting glaucoma eyes undergoing descemet membrane endothelial keratoplasty: a cohort study

BACKGROUND

Descemet membrane endothelial keratoplasty (DMEK) has become the dominant keratoplasty procedure. However, the impact of high intraocular pressure (IOP) on the DMEK prognosis in patients without preexisting glaucoma remains unknown.

METHODS

Non-glaucoma patients who underwent DMEK in Peking University Third Hospital between July 2017 and March 2023 with a follow-up duration longer than six months were included in this cohort study. Eyes were divided into three groups: Group A) normal IOP; Group B) early IOP elevation (IOP ≥ 30 mmHg or increase of more than 10 mmHg from baseline within 3 days); Group C) intermediate-term IOP elevation (IOP > 21 mmHg or increase of more than 10 mmHg from baseline after 14 days postoperatively). The postoperative IOP, endothelial cell density (ECD), central corneal thickness (CCT), best-corrected visual acuity (BCVA) and rate of graft failure were analysed.

RESULTS

Forty-seven eyes from forty-seven patients were included. Thirty-seven eyes were bullous keratopathy, and ten were Fuchs endothelial corneal dystrophy. Twenty-five eyes were classified as Group A, six as Group B and sixteen as Group C. The mean peak IOP was 49.00 ± 4.99 mmHg in Group B eyes and 31.89 ± 11.75 mmHg in Group C eyes. The postoperative BCVA significantly differed from that before surgery (P < 0.001). The ECD at 3 months after surgery in eyes with intermediate-term IOP elevation was lower (P = 0.032). Four eyes with intermediate-term IOP elevation developed graft failure (P = 0.001).

CONCLUSIONS

Intermediate-term IOP elevation after DMEK may reduce the graft ECD and lead to graft failure within six months after surgery. However, early IOP elevation had no effect on the prognosis. Careful IOP monitoring and intermediate-term IOP management should be conducted for graft protection.

Applications of Imaging Technologies in Fuchs Endothelial Corneal Dystrophy: A Narrative Literature Review

Fuchs endothelial corneal dystrophy (FECD) is a complex genetic disorder characterized by the slow and progressive degeneration of corneal endothelial cells. Thus, it may result in corneal endothelial decompensation and irreversible corneal edema. Moreover, FECD is associated with alterations in all corneal layers, such as thickening of the Descemet membrane, stromal scarring, subepithelial fibrosis, and the formation of epithelial bullae. Hence, anterior segment imaging devices that enable precise measurement of functional and anatomical changes in the cornea are essential for the management of FECD. In this review, the authors will introduce studies on the application of various imaging modalities, such as anterior segment optical coherence tomography, Scheimpflug corneal tomography, specular microscopy, in vitro confocal microscopy, and retroillumination photography, in the diagnosis and monitoring of FECD and discuss the results of these studies. The application of novel technologies, including image processing technology and artificial intelligence, that are expected to further enhance the accuracy, precision, and speed of the imaging technologies will also be discussed.

Diagnostic Techniques to Increase the Safety of Phakic Intraocular Lenses

Preoperative and postoperative diagnostics play an important role in ensuring the safety of patients with phakic intraocular lenses (pIOLs). The risk of endothelial cell loss can be addressed by regularly measuring the endothelial cell density using specular microscopy and considering the endothelial cell loss rate and the endothelial reserve in accordance with the patient's age when deciding whether to explant a pIOL. The anterior chamber morphometrics, including the anterior chamber depth and the distance between the pIOL and the endothelium, measured using Scheimpflug tomography and anterior segment optical coherence tomography (AS-OCT), can help to assess the risk of the endothelial cell loss. In patients undergoing posterior chamber pIOL implantation, accurate prediction of the vault and its postoperative measurements using AS-OCT or Scheimpflug tomography are important when assessing the risk of anterior subcapsular cataract and secondary glaucoma. Novel approaches based on ultrasound biomicroscopy and AS-OCT have been proposed to increase the vault prediction accuracy and to identify eyes in which prediction errors are more likely. Careful patient selection and regular postoperative follow-up visits can reduce the complication risk and enable early intervention if a complication occurs.

Corneal Endothelial Cell Density in Normal Tension Glaucoma Compared to Healthy Controls

The purpose of this study was to investigate corneal endothelial cell density (ECD) and morphology between normal tension glaucoma (NTG) and controls. A cross-sectional, single center study of 24 NTG and 26 age-matched healthy eyes were included. ECD, mean cell size (MCA) and coefficient of variance (CV) were analyzed, controlling for age and number and duration of concurrent glaucoma medications. NTG subjects had significantly lower ECD (2307 ± 514.7 vs. 2558 ± 278.5, p = 0.044) and larger MCA (458.3 ± 94.8 vs. 386.7 ± 57.3, p = 0.004), but no difference in CV compared to healthy subjects. NTG subjects stratified by number of glaucoma medications showed significant differences in ECD (p = 0.024) and MCA (p = 0.021), but no difference in CV. There were no significant differences in ECD, MCA or CV between subjects stratified by duration of glaucoma medication usage. After age-adjusting, there was no dose-dependent relationship between mean ECD or MCA and number of glaucoma medications. Post hoc analysis demonstrated only NTG subjects on three or more glaucoma medications had statistically significant differences in ECD (p = 0.032) and MCA (p = 0.037) compared to NTG subjects on two glaucoma medications. This study suggests that NTG is associated with lower corneal endothelial cell density and mean cell size.

Segmentation methods and morphometry of confocal microscopy imaged corneal epithelial cells

PURPOSE

To develop and explore automated cell identification and segmentation methods for morphometry of confocal microscopy imaged corneal epithelial cells using ImageJ software.

METHODS

In vivo confocal microscopy images of the intermediate (wing) and basal cell layers of the central and peripheral corneas of 20 healthy participants were analysed. The intermediate and basal cell areas obtained using the two new techniques (i.e., manual- and auto- thresholding) were compared with the widely used manual tracing technique. A predefined range of epithelial cell morphometric parameters was used as image descriptors to improve cell identification and segmentation.

RESULTS

The mean intermediate cell area obtained using the manual tracing (central; 120 ± 14 µm², peripheral; 123 ± 15 µm²) was statistically similar (p > 0.05) to the manual thresholding (central; 119 ± 7 µm², peripheral; 119 ± 8) but not with the auto thresholding technique (central; 101 ± 8 µm², peripheral; 101 ± 7 µm²). Bland-Altman limits of agreement for the mean difference (measurement bias) in central and peripheral intermediate cell area determined via manual tracing and manual thresholding techniques were 1 µm² (+25 to - 23 µm²) and 4 µm² (+29.8 to - 21.9 µm²). There were statistically significant differences in basal cell area between the three methods.

CONCLUSION

The manual thresholding technique may be used for automated identification and segmentation of corneal epithelial intermediate cells (central and peripheral) for assessing various morphometric parameters. However, measurement of the corneal epithelial basal cells is less reliable using thresholding techniques.

Descemet Membrane Endothelial Keratoplasty: Development of Contrast Sensitivity and Color Vision in Patients With Fuchs Endothelial Corneal Dystrophy

PURPOSE

To assess the developments in contrast sensitivity, color vision, and subjective perception after Descemet membrane endothelial keratoplasty (DMEK) in patients with Fuchs endothelial corneal dystrophy (FECD).

METHODS

Included in this study were pseudophakic, unilateral DMEK patients with bilateral FECD having a follow-up period of 6 months (n = 23). The mean age at surgery was 70 years (range: 52-81 years). Pseudophakic eyes without history of other ocular pathology or surgery served as a control (n = 10). Pelli-Robson contrast sensitivity and Panel-D15 color vision tests were used. Best-corrected visual acuity, modified visual functioning questionnaire-25, central corneal thickness, and endothelial cell density were assessed. We visualized the subjective impression of patients with bilateral FECD after unilateral DMEK in a subgroup using Photoshop CS6.

RESULTS

Contrast sensitivity improved significantly from 1.35 ± 0.26 to 1.64 ± 0.17 (P = 0.002; control eyes: 1.92 ± 0.09). No difference in the color vision error score was observed for preoperative and postoperative eyes (P = 0.063). The best-corrected visual acuity improved significantly after surgery (P = 0.001). The average values in the Logarithm of the Minimum Angle of Resolution were 0.59 ± 0.42 preoperatively and 0.1 ± 0.10 postoperatively (control eyes: 0.01 ± 0.03). Examinations revealed a decrease of the central corneal thickness and endothelial cell density after surgery (P = 0.001; P = 0.001, respectively). Scores in the general and the driving questionnaire were significantly higher after surgery (P = 0.001; P = 0.005, respectively).

CONCLUSIONS

This study showed significant improvement in subjective patient satisfaction and contrast sensitivity. Spontaneous subjective color vision improvement might be explained by significantly improved contrast sensitivity. Contrast sensitivity might be considered as a parameter in preoperative decision-making and evaluation of surgical outcome.

Agreement of Corneal Endothelial Cell Analysis Between Konan-Noncon Robo SP-6000 and Tomey EM-3000 Specular Microscopes in Healthy Subjects

PURPOSE

To compare corneal endothelium parameters taken by two common noncontact specular microscopes in healthy subjects.

METHODS

Healthy participants visiting the outpatient eye clinic at the Rabin Medical Center, Petah Tikva, Israel, were recruited prospectively. All participants underwent three consecutive corneal endothelial cell photographs with both the Konan-Noncon Robo SP-6000 and the Tomey EM-3000 specular microscopes. Endothelial cell density (ECD) was evaluated using the manual center technique in both machines. Bland-Altman graphs were used to assess the agreement between the devices, and intraclass correlation coefficient (ICC) served to assess intraobserver variability for each device.

RESULTS

Recruited were 49 healthy subjects with a mean age of 48.9±15.6 years, 49 right eyes were included. The mean ECD was comparable between the Tomey EM-3000 and the Konan-Noncon Robo SP-6000 (2,713.2±242.4 vs. 2,700.8±300.5 cells/mm2, respectively, P=0.47) with a mean difference of 12.4 cells/mm2 (0.67%), a mean ECD absolute difference of 93.3 cells/mm2, and low 95% limits of agreement of -222.0 to +246.9 cells/mm2. A folded empirical distribution function curve showed that all differences fell within 525.4 cells/mm2, centered around a median of 13.3 cells/mm2. Intraclass correlation coefficient was high for both the Konan-Noncon Robo SP-6000 (0.93, 95% confidence interval [CI]: 0.89-0.95) and the Tomey EM-3000 (0.88, 95% CI: 0.82-0.93).

CONCLUSIONS

The difference in endothelial cell measurements between the Konan SP-6000 and the Tomey EM-3000 specular microscopes through the center and the L-count analyzing techniques, respectively, is clinically small and not statistically significant. Nevertheless, caution should be taken when used interchangeably because ECD difference between the two machines can be as high as 525.4 cells/mm2.

Corneal endothelial cells changes in different stages of Keratoconus: a multi-Centre clinical study

Purpose

To assess the corneal endothelial cells morphology and count in keratoconus patients and their correlation with different stages of keratoconus.

Methods

Prospective non randomized multi-centric clinical study included 150 eyes of 150 keratoconus patients. Four centers in Egypt participated in this study included: Departments of Ophthalmology in Alexandria University, Tanta University and Port Said University and Alex I-Care hospital. Pentacam (Wavelight Oculyzer II) and specular microscopy (Tomey EM-3000) were done to all eyes. Keratoconic eyes were classified according to Amsler classification into stage 1, 2 and 3. Stage 1 included 99 eyes, stage 2 included 32 eyes & stage 3 included 19 eyes.

Results

The mean age of keratoconus patients was 24.07 ± 6.154 years. Forty five cases were males (30%) and 105 cases were females (70%). There was statistically significant difference in endothelial cell density (p < 0.001) and coefficient of variation (p = 0.012) between different stages of keratoconus eyes. Regarding cell surface area, there was statistically significant difference in cell surface area between different stages of keratoconus eyes (p < 0.001). In addition, for cell morphology, there was statistically significant difference between different stages of keratoconus eyes (p < 0.001).

Conclusions

Qualitative and quantitative structural changes were seen in endothelial cells of keratoconus eyes by using specular microscopy. For stages 1 and 2, keratoconus may not affect the corneal endothelim significantly. The endothelium in stage 3 shows significant changes regarding polymegathism and pleomorphism.

Survival of the fittest: phacoemulsification outcomes in four corneal transplants by Dr Ramon Castroviejo

AIM

To evaluate and report the outcomes following phacoemulsification on four eyes, 45 years or more after corneal transplantation.

METHODS

A retrospective case series of four eyes in three patients (P1, P2, P3), undergoing phacoemulsification at least 45 years after corneal transplantation by Dr Ramon Castroviejo. Corneal graft survival outcome measures included central corneal thickness (CCT), best-corrected visual acuity (BCVA), corneal clarity and endothelial cell count (ECC).

RESULTS

Phacoemulsification was successfully completed in all four cases with no instances of graft failure during the postoperative follow-up period, which ranged from 17 months to 76 months. At the conclusion of the follow-up period, all four grafts remained clear, and BCVA remained better than or similar to preoperative values. Long-term follow-up revealed no meaningful changes in CCT after phacoemulsification. All but one case experienced a decrease in ECC, with ECC values in the four cases ranging from 538 cells/mm² to 1436 cells/mm² at the conclusion of postoperative follow-up.

CONCLUSION

Limited data have been published on the long-term survival of corneal grafts after intraocular surgery, especially for extremely 'mature' corneal transplants. This case series demonstrates that with appropriate preoperative, intraoperative and postoperative measures, successful phacoemulsification can be performed in these cases with excellent long-term results.

Quantitative assessment of human donor corneal endothelium with Gabor domain optical coherence microscopy

We report on a pathway for Gabor domain optical coherence microscopy (GD-OCM)-based metrology to assess the donor’s corneal endothelial layers ex vivo. Six corneas from the Lions Eye Bank at Albany and Rochester were imaged with GD-OCM. The raw 3-D images of the curved corneas were flattened using custom software to enhance the 2-D visualization of endothelial cells (ECs); then the ECs within a circle of 500-μm-diameter were analyzed using a custom corner method and a cell counting plugin in ImageJ. The EC number, EC area, endothelial cell density (ECD), and polymegethism (CV) were quantified in five different locations for each cornea. The robustness of the method (defined as the repeatability of measurement together with interoperator variability) was evaluated by independently repeating the entire ECD measurement procedure six times by three different examiners. The results from the six corneas show that the current modality reproduces the ECDs with a standard deviation of 2.3% of the mean ECD in every location, whereas the mean ECD across five locations varies by 5.1%. The resolution and imaging area provided through the use of GD-OCM may help to ultimately better assess the quality of donor corneas in transplantation.

Variability of Central Corneal Thickness Measurements-Comparing Zeiss IOL Master and Tomey Corneal Specular Microscope

PURPOSE

The aim of this study was to compare the intraobserver repeatability and agreement of central corneal thickness (CCT) measurements by 2 commonly available instruments, Zeiss IOL Master 700 (SS-OCT-based optical biometry device) and Tomey corneal specular microscope EM-3000 (Noncontact specular microscopy).

DESIGN

Retrospective study.

METHODS

This is a retrospective analysis of data from routine clinical practice in which preoperative CCT measurements of 105 patients scheduled for cataract surgery were analyzed. Two consecutive CCT measurements were measured using Zeiss IOL Master 700 and Tomey corneal specular microscope EM-3000 by the same examiner. The repeatability of CCT measurements was analyzed by mean intraobserver difference, coefficient of repeatability (CR), and intraclass correlation. The agreement between the 2 methods was analyzed by mean difference and limits of agreement (LoA) using the Bland-Altman method.

RESULTS

The mean absolute intraobserver difference between the 2 measurements by Zeiss and Tomey were 3.41 ± 3.98 μm and 8.62 ± 9.52 μm (P < 0.0001), respectively. For Zeiss, the CR was 10.3 μm with 95% LoA of -10.5 to 10.1 μm. For Tomey, the CR was 25.2 μm with 95% LoA of -25.2 to 25.2 μm. The mean CCT measurements ± standard deviation by Zeiss and Tomey were 544.0 ± 38.1 μm and 532.6 ± 40.0 μm, respectively (P = 0.003). The 95% LoA in CCT between the 2 methods was -15.8 to 38.7 μm.

CONCLUSIONS

Zeiss IOL Master 700 has superior intraobserver repeatability and consistency than Tomey EM-3000. Zeiss produced higher CCT measurements than Tomey; hence, in clinical practice, interchangeability between these 2 methods is limited.

Imaging the Corneal Endothelium in Fuchs Corneal Endothelial Dystrophy

Fuchs endothelial corneal dystrophy (FECD) is characterized by the progressive degeneration of the corneal endothelium (CE). The purpose of this article is to review the diagnostic tools available to image and assess the CE in FECD. Slit-lamp biomicroscopy with specular reflection and retroillumination are important techniques to assess the CE. Objective diagnostic tests, such as retroillumination photographic analysis, specular microscopy, in vivo confocal microscopy (IVCM), and anterior segment optical coherence tomography, are valuable tools to evaluate the CE in FECD. Specular microscopy can be performed rapidly without touching the eye but requires a clear cornea with a smooth CE. In contrast, IVCM can image all layers of the cornea, even in advanced FECD. However, IVCM is contact-based and more technically challenging. It is important to select the appropriate objective diagnostic test to image and assess the CE in managing patients with FECD.

Comparison of Noncontact Specular and Confocal Microscopy for Evaluation of Corneal Endothelium

PURPOSE

To compare endothelial cell analysis obtained by noncontact specular and confocal microscopy, using the Konan NSP-9900 and Nidek ConfoScan4 systems, respectively.

METHODS

Three groups including 70 healthy eyes, 49 eyes with Fuchs endothelial corneal dystrophy (FECD), and 78 eyes with glaucoma were examined with both the Konan NSP-9900 specular microscope and the Nidek ConfocScan4 confocal microscope. Certified graders at the Doheny Image Reading Center compared corneal endothelial images from both instruments side by side to assess image quality. Endothelial cell density (ECD) measurements were calculated and compared using three different modalities: (1) each instrument's fully automated analysis; (2) each instrument's semiautomatic analysis with grader input; and (3) manual grading methods by certified grader.

RESULTS

All normal eyes yielded gradable endothelial images, and most but not all glaucomatous eyes yielded images with high enough image quality to allow grading. In addition, in corneas with severe FECD, poor image quality precluded ECD grading by specular microscopy in 20 eyes (40.8%) but in only 4 (8.2%) confocal images from the same eyes. For the gradable images, the ECD values obtained using the manual grading method from either device were comparable with no statistically significant difference (P>0.05) between specular and confocal devices. Machine-generated ECD values were significantly different from manual results, measuring greater in all cases with specular microscopy. Machine-generated ECD values from confocal microscopy also differed significantly from manual determinations, but not in a consistent direction. Semiautomatic methods for both instruments obtained clinically acceptable ECD values.

CONCLUSIONS

Automatic machine-generated ECD measurements differed significantly from manual assessments of corneal endothelium by both specular and confocal microscopy, suggesting that automated results should be used with caution. But ECD values derived manually were comparable between the two devices in both normal and glaucomatous eyes, suggesting that manually graded images from the two instruments can be used interchangeably for reliable ECD measurements. Because of a higher proportion of gradable images, confocal microscopy may be superior to specular microscopy for ECD measurements in FECD.

Corneal Endothelial Cell Segmentation by Classifier-Driven Merging of Oversegmented Images

Corneal endothelium images obtained by in vivo specular microscopy provide important information to assess the health status of the cornea. Estimation of clinical parameters, such as cell density, polymegethism, and pleomorphism, requires accurate cell segmentation. State-of-the-art techniques to automatically segment the endothelium are error-prone when applied to images with low contrast and/or large variation in cell size. Here, we propose an automatic method to segment the endothelium. Starting with an oversegmented image comprised of superpixels obtained from a stochastic watershed segmentation, the proposed method uses intensity and shape information of the superpixels to identify and merge those that constitute a cell, using support vector machines. We evaluated the automatic segmentation on a data set of in vivo specular microscopy images (Topcon SP-1P), obtaining 95.8% correctly merged cells and 2.0% undersegmented cells. We also evaluated the parameter estimation against the results of the vendor's built-in software, obtaining a statistically significant better precision in all parameters and a similar or better accuracy. The parameter estimation was also evaluated on three other data sets from different imaging modalities (confocal microscopy, phase-contrast microscopy, and fluorescence confocal microscopy) and tissue types (ex vivo corneal endothelium and retinal pigment epithelium). In comparison with the estimates of the data sets' authors, we achieved statistically significant better accuracy and precision in all parameters except pleomorphism, where a similar accuracy and precision were obtained.

Automated morphometric description of human corneal endothelium from in-vivo specular and confocal microscopy

Corneal images acquired by in-vivo specular and confocal microscopy provide clinical information on the cornea endothelium health state. Indeed, the normal hexagonal shape of endothelial cells is usually affected by age and pathologies. At present, the analysis is based on manual or semi-automatic methods and the segmentation of a large number of endothelial cells is required for a meaningful estimation of the clinical parameters. We propose an automated method that detects the centers of endothelial cells by convolving the original image with customized two-dimensional kernels, derives a structure made by connected vertices from the recognized centers using the Euclidean distance, and fine-tunes the derived structure through a genetic algorithm, which combines information about the typical regularity of endothelial cells shape with the pixels intensity of the actual image. The final structure of connected vertices forms a set of polygons that fit the underlying cells contours. From these contours the morphometric parameters of clinical interest can be easily computed. The procedure was applied to 15 images acquired with the SP-3000P (Topcon, Japan) specular microscope and 15 images acquired with the Confoscan4 (Nidek Technologies, Italy) confocal microscope, from both healthy and pathological subjects. Ground truth values for the morphometric parameters were obtained from manually carefully drawn cell contours. Results show that the mean percent absolute difference between the automated and the manual estimate of the clinical parameters is between 2 and 6%, and no statistically significant difference was found between them. The proposed totally automatic method appears capable of detecting contour of hundreds of cells covering a large area, and of obtaining a reliable estimation of the relevant morphometric parameters used in clinical practice.

Measurements of central corneal thickness and endothelial parameters with three different non-contact specular microscopy devices

We aimed to compare the measurements of central corneal thickness (CCT) and endothelial parameters with three different non-contact specular microscopy (SM) devices. Fifteen eyes of 15 healthy individuals (6 males; 9 females) were enrolled in the study. Mean age was 37.93 ± 15.13 years. Endothelial parameters and CCT were measured with Nidek CEM-530, Topcon SP-3000P, and Tomey EM-3000 SM devices by the same physician. Endothelial parameters included endothelial cell count (ECC), maximum, minimum, and average endothelial cell size. and hexagonality ratio. There were no statistically significant differences in ECC, CTT, and average endothelial size (AES) between the devices (p > 0.05). The measurement of maximum endothelial size (MES) was different between Nidek SM and Topcon SM devices (p = 0.001), but there was no difference in MES between Nidek SM and Tomey SM (p = 0.058), and between Topcon SM and Tomey SM (p = 0.081). There was no difference in minimum endothelial size (MinES) between Nidek SM and Topcon SM (p = 0.794); however, there was a significant difference in MinES between Tomey SM and Nidek SM (p < 0.001), and between Tomey SM and Topcon SM (p < 0.001). Comparison of hexagonality ratio showed statistically significant difference between the devices (p < 0.001). No significant differences in the measurements of ECC, CCT, and AES were detected between different SM devices, whereas a statistically significant difference in hexagonality ratio was detected between the devices. These devices should not be used alternatively in the endothelial morphology assessment in patient's follow-up.

Assessing the Reproducibility of Quantitative In Vivo Confocal Microscopy of Corneal Nerves in Different Corneal Locations

PURPOSE

To evaluate the reproducibility of in vivo confocal microscopy for quantitative corneal nerve analysis in different corneal locations.

METHODS

Corneal confocal microscopy was performed on 10 healthy participants, and the corneal nerve fiber length, corneal nerve fiber density, corneal nerve branch density, and tortuosity coefficient were measured at 5 predetermined locations for only the right eye. Bland-Altman plots, intraclass correlation coefficient (ICC), and coefficient of variation of all 4 corneal nerve measurements were compared between 2 visits and between readers to assess reproducibility. Two technicians performed a masked analysis of images from both visits.

RESULTS

Ten participants with a mean age of 31.3 ± 2.8 years were imaged at 2 different time points separated by a mean of 4.3 ± 4.3 weeks. The interobserver agreements were better than the intervisit agreements for all the 4 corneal nerve measurements as evaluated using Bland-Altman plots. The intervisit ICC ranged from 0.13 to 0.45, and the interobserver ICC ranged from 0.55 to 0.94. The differences between observers and the differences between sessions were not statistically different among all the 5 locations (P > 0.1) for each corneal nerve measurement.

CONCLUSIONS

Single confocal images have poor reliability for any of the 4 corneal nerve measurements, and there is no single location on the cornea that has improved reproducibility. Averaging 5 images, from different locations, improves the reproducibility and is essential for obtaining clinically meaningful data.

A Pilot Study to Propose a "Harm Scale", a New Method to Predict Risk of Harm to the Corneal Endothelium Caused by Longitudinal Phacoemulsification, and the Subsequent Effect of Endothelial Damage on Post Operative Visual Acuity

PURPOSE

To study the effect of longitudinal phacoemulsification energy on corneal endothelium and to evaluate the relationship between changes of endothelial cells and postoperative visual acuity.

METHODS

This prospective clinical observational cohort study included 50 patients with cataract who underwent longitudinal phacoemulsification. Sequential quantitative and qualitative morphometric endothelial cell analyses of the cornea were performed 4 weeks preoperatively and 6 weeks postoperatively using noncontact specular microscopy.

RESULTS

There was a relationship between ECL percentage (ECL%) and the 5-score harm scale, well-described by a linear model (one-way ANOVA, R2 = 73.3%). Analyzing the distribution of ECL% Mean with Tukey post-hoc pairwise comparison test (P < 0.001), the value of ECL = 20% has been regarded as cut-off to discriminate patients who obtained an excellent postoperative best-corrected visual acuity (BCVA > 85 letters) from those who just had a good visual outcome (BCVA ≤ 85 letters). There was a significant correlation among the 5-score harm scale, phaco energy intraoperatively delivered, and average cell area postoperatively.

CONCLUSIONS

The 5-score harm scale, a new method that enables to pigeonhole cataracts taking into account nucleus hardness and phaco times, allows to predict the harm on corneal endothelium after longitudinal phacoemulsification. Assessment of ECL% permits to discriminate between patients with excellent BCVA and with just good BCVA, postoperatively.

A 1-year randomized study of the clinical and confocal effects of tafluprost and latanoprost in newly diagnosed glaucoma patients

Introduction

The aim of the present study was to compare the confocal and clinical features of newly diagnosed glaucoma patients receiving unpreserved prostaglandins (tafluprost) versus preserved prostaglandins (latanoprost).

Materials and Methods

40 patients were randomized to tafluprost 0.0015% (20 patients; 32 eyes) or latanoprost 0.005% + benzalkonium chloride 0.02% (20 patients; 35 eyes) once daily for 1 year. Inclusion criteria were new glaucoma diagnosis, and no ocular treatments for 6 months before the study. Patients were evaluated at baseline and every 3 months with a complete ophthalmologic evaluation, Schirmer’s test, break-up time test, confocal microscopy of the central cornea, and measurement of intraocular pressure (IOP). Investigators were masked to treatment. Both eyes were analyzed if they fulfilled inclusion criteria. Treatments and changes between follow-up and baseline were compared by analysis of variance (ANOVA), t test and Chi-square test.

Results

At baseline, the two groups had similar age, ocular surface and confocal findings; keratocyte activation was present in 40%, branching pattern in 85%, and beading in 75%, with no inter-group differences. At follow-up, no significant clinical changes were detected, apart from a drop of IOP by 3.6–4.2 mmHg in the two groups (p < 0.001, with no difference between treatments). Despite inter-treatment ANOVA for confocal microscopy being negative, subtle changes were present. During follow-up, all eyes without nerve branching pattern at baseline progressively developed it when treated with latanoprost, whereas no change occurred using tafluprost treatment (p = 0.05). None of the eyes without beading at baseline developed it at the end of the study in the tafluprost group, whereas beading did occur in 75% of patients treated with latanoprost (p = 0.05). Both treatments were associated with increased keratocyte activation at follow-up; the change from baseline was statistically significant after month 3 with latanoprost (p = 0.02) and after month 6 with tafluprost (p = 0.04).

Conclusions

The two study treatments had similar clinical effects, but tafluprost had a more favorable profile for some confocal parameters of the cornea.

Funding

Merck Sharp & Dohme International.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-015-0205-5) contains supplementary material, which is available to authorized users.

Corneal involvement in uneventful cataract surgery: an in vivo confocal microscopy study

PURPOSE

To evaluate corneal subbasal layer changes after uneventful cataract surgery by means of in vivo confocal microscopy.

METHODS

This prospective study included 30 patients. Before surgery, and 1, 3, 6, 8 and 10 months after cataract surgery, all patients underwent a complete ophthalmological and confocal microscopy examination in the central and temporal corneal areas. Number of fibers, beading, tortuosity and reflectivity were analyzed.

RESULTS

Important changes were shown in the central cornea up to 3 months after surgery: a reduction in nerve fiber number (baseline: 4.4 ± 1.7; month 1: 1.2 ± 0.5, p < 0.0001; month 3: 2.5 ± 1.2, p < 0.005) and reflectivity (baseline: 3.6 ± 0.5; month 1: 1.4 ± 0.6, p < 0.0001; month 3: 1.9 ± 0.9, p < 0. 0001), and an increase in beading (baseline: 0.3 ± 0.5 beads/100 µm(2); month 1: 2.7 ± 0.6 beads/100 µm(2), p < 0.0001; month 3: 2.6 ± 0.5 beads/100 µm(2), p < 0. 0001). The confocal parameters completely progressively recovered thereafter (60% at 6 months, 87% at 8 and 10 months). The temporal plexus was absent at 1 month and fully recovered in all patients at month 8.

CONCLUSION

Uneventful cataract surgery induces relevant corneal modifications when inspected by means of confocal microscopy.

Assessment of a variable frame (polygonal) method to estimate corneal endothelial cell counts after corneal transplantation

PURPOSE

To assess the agreement of the 'polygonal' variable frame cell count option on a confocal microscope after keratoplasty, with planimetry as the reference method.

METHODS

One hundred clear corneal grafts of 83 patients attending the cornea clinic at Gartnavel General Hospital in Glasgow underwent slit-scanning in vivoconfocal microscopy. Endothelial cell images were assessed with the Nidek Advanced Vision Information System (NAVIS), using the polygonal variable frame and the manual fixed-frame methods. Planimetry was used as the reference. The agreement between methods was assessed by Bland-Altman analysis.

RESULTS

Planimetry provided a mean (± SD) endothelial cell density (ECD) of 1348 ± 726 cells/mm(2), a value that was very similar to that found by the polygonal method (1404 ± 784 cells/mm(2)). The fixed-frame method provided lower cell counts with a mean ECD of 1026 ± 610 cells/mm(2) (P<0.001). When compared with the reference ECD, the polygonal method overestimated the ECD only very slightly with a mean difference of 58 cells/mm(2) (limits of agreement, LoA, of -222 and 339 cells/mm(2)). Manual counting underestimated the ECD with a mean difference of -320 cells/mm(2) (LoA -814 and 173 cell/mm(2)).

CONCLUSION

Following keratoplasty, endothelial cell counts with the NAVIS polygonal method are in good agreement with planimetry. The 'polygonal' option is proposed as the method of choice for clinical applications with this confocal microscope and a good compromise between reliability and ease of use.

Assessment of corneal thickness and keratocyte density in a rabbit model of laser in situ keratomileusis using scanning laser confocal microscopy

PURPOSE

To determine the repeatability of corneal thickness and keratocyte density using in vivo confocal scanning laser microscopy in a rabbit model of laser in situ keratomileusis.

DESIGN

Prospective, experimental animal study.

METHODS

En face tomographic images of corneal tissue were captured from 5 New Zealand white rabbits. Central corneal thickness was compared with conventional ultrasonic pachymetry. Keratocyte density was measured as a function of stromal depth at baseline and 6 weeks after a 130-μm lamellar incision in the following regions: first countable stromal image (30 to 39 μm), anterior stroma (40 to 75 μm), incision zone (76 to 150 μm), mid stroma (151 to 250 μm), and deep stroma (251 to 400 μm).

RESULTS

The mean residual difference between ultrasonic and confocal corneal thickness measurements was 2.1 μm (95% confidence interval [CI], -7.0 to 11.2 μm; P = .61). Before the lamellar incision, keratocyte density was highest in the first countable frame of the anterior stroma, 53 800 cells/mm(3) (95% CI, 35 000 to 72 000 cells/mm(3)) and was least in deep stroma, 27 100 cells/mm(3) (95% CI, 22 400 to 32 000 cells/mm(3)). Six weeks after stromal lamellar incision, keratocyte density was unchanged in the first countable frame of the anterior stroma, 43 700 cells/mm(3) (95% CI, 31 800 to 55 500 cells/mm(3); P = .29). There were no changes in cell density in deeper stromal regions.

CONCLUSIONS

There was excellent agreement between ultrasonic and confocal microscopy measurements of corneal thickness. In vivo repeatability of keratocyte density estimation using scanning laser confocal microscopy is comparable with the results of previous reports using tandem-scanning confocal microscopy. Keratocyte density was more varied, but not significantly different, in the anterior-most corneal stroma 6 weeks after a lamellar incision.