Corneal endothelial cell analysis using two non-contact specular microscopes in healthy subjects

Corneal Endothelial Microscopy: Does a Manual Recognition of the Endothelial Cells Help the Morphometric Analysis Compared to a Fully Automatic Approach?

This study investigated whether manual integration in the recognition of the endothelial cells produces different outcomes of morphometric parameters compared to a fully automatic approach. Eight hundred and ninety endothelial images, originally acquired by the Perseus Specular Microscope (CSO, Florence, Italy), from seven positions of right and left corneas were selected from the database of the Research Centre in Optics and Optometry at the University of Milano-Bicocca. For each image selected, two procedures of cell identification were performed by the Perseus: an automatic identification and a manual-integrated procedure to add potential additional cells with the available editing tool. At the end of both procedures, the endothelial cell density (ECD), coefficient of variation (CV), and hexagonality (HEX) of the mosaic were calculated. The HEX in the two procedures was significantly different for all comparisons (p < 0.001), but clinically negligible. No significant differences were found for the CV and ECD in the images of both eyes irrespective of the corneal position of acquisition (except for ECD in three corneal portions, p < 0.05). To conclude, it is possible to recognise a significantly higher number of cells using the manual-integrated procedure than it is using the fully automatic one, but this does not change the morphological parameters achieved.

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.

Postoperative, but not preoperative, central corneal thickness correlates with the postoperative visual outcomes of Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) restores visual acuity in patients with progressive corneal endothelial diseases such as Fuchs endothelial corneal dystrophy (FECD). However, patients often prefer to delay the surgery as long as possible, even though outcomes are poorer in advanced FECD. A recent study proposed that preoperative central corneal thickness (CCT) of ≥625 μm associated with worse best spectacle-corrected visual acuity (BSCVA) after DMEK for FECD. Since this threshold could signal to both surgeons and patients when to perform DMEK, we further explored the relationship between CCT and BSCVA with a retrospective cohort study. The cohort consisted of all patients with FECD who underwent DMEK in a tertiary-care hospital in 2015-2020 and were followed for 12 months. Extremely decompensated corneas were not included. Relationships between preoperative CCT and BSCVA on days 8 and 15 and months 1, 3, 6, and 12 were examined with Pearson correlation analyses. Eyes with preoperative CCT <625 or ≥625 μm were also compared in terms of postoperative BSCVA. Relationships between postoperative CCT and final BSCVA were also explored. The cohort consisted of 124 first-operated eyes. Preoperative CCT did not correlate with postoperative BSCVA at any timepoint. Eye subgroups did not differ in postoperative BSCVA. However, postoperative CCT at 1-12 months correlated significantly with 12-month BSCVA (r = 0.29-0.49, p = 0.020-0.001). Thus, postoperative, but not preoperative, CCT correlated with postoperative BSCVA. This phenomenon may reflect factors that distort preoperative CCT measurements but disappear after surgery. This observation and our analysis of the literature suggest that while there is a relationship between CCT and post-DMEK visual acuity, preoperative CCT measurements may not always adequately reflect that relationship and may therefore not be a reliable predictor of DMEK visual outcomes.

Effectiveness of surgical management of malignant glaucoma in phakic eyes

AIM

To assess the effectiveness of core vitrectomy-phacoemulsification-intraocular lens (IOL) implantation-capsulo-hyaloidotomy in treating phakic eye at least 1mo after the onset of malignant glaucoma.

METHODS

A retrospective analysis were performed on malignant glaucoma patients treated in Zhongshan Ophthalmic Center between 2016 and 2018. Demographic and clinical data were described. The preoperative and postoperative visual acuity (VA), intraocular pressure (IOP), number of IOP-lowering medications used, and anterior chamber depth (ACD) of the case series were compared by Wilcoxon signed-rank test.

RESULTS

Thirteen phakic eyes with long time intervals between onset and surgery were identified in this case series. Core vitrectomy-phacoemulsification-IOL implantation-capsulo-hyaloidotomy reduced the IOP (P=0.046) and the number of IOP-lowering medications used (P=0.004), deepened the ACD (P=0.005). Complete success was achieved in 38.5% of the eyes, and anatomical success was achieved in 100% of the eyes without any recurrence. The only postoperative complication observed is corneal endothelial decompensation. It occurred in two cases.

CONCLUSION

Core vitrectomy-phacoemulsification-IOL implantation-capsulo-hyaloidotomy is safe and effective for treatment of long onset phakic malignant glaucoma.

Potential Factors of Corneal Endothelial Cells for Progression in Children with Uveitis

Objective

To observe the morphological changes and abnormal structure of corneal endothelial cells in children with uveitis, to analyze the related factors affecting the morphological changes of corneal endothelial cells, and to explore the clinical application of a corneal endothelial microscope in children with uveitis.

Methods

The corneal endothelial cells of 70 patients with uveitis were photographed with the Topcon SP-3000 noncontact corneal endothelial microscope, and the corneal endothelial cell density (CD), average cell area (AVE), coefficient of variation of the cell area (CV), and percentage of hexagonal cells (PHC) were measured with the IMAGEnet system. Twenty-eight patients (56 eyes) with monocular uveitis were selected, with the affected eyes (28 eyes) as the experimental group and the contralateral healthy eyes (28 eyes) as the control group. The corneal endothelial cell parameters between the two groups were statistically analyzed. The parameters of corneal endothelial cells in 70 children with uveitis were compared, and the effects of the course of the disease, inflammatory cells in the anterior chamber, and posterior corneal deposition (KP) on the parameters of corneal endothelial cells were analyzed.

Results

There are four abnormal forms of the corneal endothelium in children with uveitis: enlarged cell area gap, irregular cell shape, blurred intercellular space, and cell loss. KP showed irregular high reflective white spots in the corneal endothelial microscope images, surrounded by dark areas, and existed in all the eyes with dusty KP found in slit lamp examination and a small number of eyes without obvious KP. Comparing the corneal endothelial cell parameters between the experimental group and the control group, it was found that the corneal endothelial CD and PHC of the former were lower than those of the latter, and the difference was statistically significant (P < 0.001 and P = 0.018, respectively). The AVE and CA of the former were higher than those of the latter (P = 0.013 and P = 0.046, respectively). The corneal endothelial cell density of the eyes with a course of the disease of more than 1 year was lower than that of the eyes with a course of the disease less than 1 year, the coefficient of variation of the corneal endothelial cell area of the eyes with KP was higher than that of the eyes without KP, and the difference was statistically significant (P = 0.003 and P = 0.030, respectively).

Conclusion

Corneal endothelial microscopy is one of the important methods for the detection of uveitis with high sensitivity. The change of morphological parameters of corneal endothelial cells is one of the important indexes to assist in the diagnosis of uveitis and can be further promoted in ophthalmological examination.

Two-year results after combined phacoemulsification and iris-fixated phakic intraocular lens removal

PURPOSE

To describe and present results after a technique for cataract surgery combined with explantation of an iris-fixated phakic intraocular lens (IF-pIOL).

METHODS

The medical records of all patients, who had undergone cataract surgery combined with IF-pIOL explantation and subsequent implantation of a posterior chamber IOL by the Single Incision Technique (SIT), were reviewed. Data collection included preoperative and postoperative corrected distance visual acuity (CDVA), manifest refraction, and endothelial cell density (ECD) up to a follow-up time of 24 months.

RESULTS

Fifty myopic eyes (34 patients) and 9 hyperopic eyes (6 patients) had undergone a SIT procedure mainly because of cataract (67%). Postoperative CDVA improved in both the myopic eyes to 0.16 ± 0.37 logMAR, as in the hyperopic eyes to - 0.10 ± 0.55 logMAR with no eyes having loss of Snellen lines. Mean postoperative spherical equivalent was - 0.34 ± 0.72 D and - 0.10 ± 0.55 D, respectively. ECD loss 6 months after surgery was 5% and remained stable thereafter.

CONCLUSION

SIT for combined phacoemulsification and IF-pIOL removal yields good visual and refractive results and is a safe procedure in regard to ECD loss. The technique has advantages over the conventional procedure and is easy to perform.

[Specular microscopy findings in active uveitis]

PURPOSE

To study the effect of ocular inflammation in active uveitis on the corneal endothelium.

MATERIALS AND METHODS

This is a prospective cross-sectional study involving 63 eyes of 38 patients with active newly-diagnosed uveitis. Eighty-four eyes of 42 non-uveitic subjects served as a control group. All patients underwent detailed ophthalmic examination, laser flare photometry, and non-contact specular microscopy. Eyes with uveitis had a follow-up visit at one month after initiation of treatment, including laser flare photometry and specular microscopy.

RESULTS

The mean age of the active uveitis patients was 33 (range: 9-67 years) with 21 men (55%) and 17 women (45%). For the uveitis patients at baseline, the mean flare value was 32ph/ms (range: 15-100ph/ms) with flare photometry value ≥50ph/ms in 13 eyes (21%) and<50ph/ms in 50 eyes (79%). At baseline, cell density (CD) of the uveitis patients was similar to CD in control eyes (p꞊0.16). The percent of hexagonality was significantly lower (p<0.0001), and the coefficient of variance (CV) (p<0.0001) and central corneal thickness (CCT) (p<0.0001) were significantly higher than in the control group. After one month, there was a significant decrease in flare photometry values (p<0.0001), with a mean flare value of 14.5ph/ms (range: 4-60ph/ms). In the active uveitis group, the overall results of specular microscopy did not significantly vary between the initial examination and the 1-month examination. For eyes with flare photometry value ≥50ph/ms at baseline, CD and hexagonal cell count significantly increased on the 1-month examination (p꞊0.01 and p꞊0.02 respectively), while CV and CCT decreased significantly at the one-month follow-up visit (p꞊0.007/p꞊0.03 respectively). For eyes with flare photometry value at baseline <50ph/ms, there was no significant differences in specular microscopy results between the initial examination and the 1-month examination.

CONCLUSIONS

In eyes with newly-diagnosed uveitis and active anterior chamber inflammation, specular microscopy shows transient qualitative abnormalities of the corneal endothelium that depend on the severity of the anterior chamber inflammation as measured by the laser flare meter.

Examination of the effects of COVID 19 on corneal endothelium

PURPOSE

To demonstrate the effects of the disease on the corneal endothelium in individuals recovering from COVID-19 through specular microscopy.

METHODS

Eighty individuals recovering from COVID-19 (group 1) and 72 healthy controls (group 2) were included in this prospective study. After examining visual acuity, refractive defect detection, anterior and posterior segment examinations, and specular microscopy measurements were calculated from images with at least 100 cells. The mean cell density (CD), mean coefficient of variation (CV), mean hexagonal cell percentage, mean cell area (AVG), and central corneal thickness (CCT) were evaluated.

RESULTS

The mean time from diagnosis of the disease in group 1 was 54.25 ± 6.36 days. The mean time elapsed since the PCR test became negative was 38.45 ± 6.87 days. Only four were treated in the hospital. Specular microscopy data showed that the CD was 2713.56 ± 246.25 and 2845.80 ± 299.27 in groups 1 and 2, respectively (p = 0.003). The CV values were 42.92 ± 6.79 and 40.16 ± 5.97, respectively (p = 0.009). The hexagonality were 46.51 ± 7.35 and 49.12 ± 6.87, respectively (p = 0.024). The AVG was 371.60 ± 34.64 and 353.16 ± 35.29, respectively (p = 0.007). The CCT values were 553.00 ± 73.2, and 526.84 ± 33.57, respectively (p = 0.005).

CONCLUSION

A decrease in the number of endothelial cells and hexagonal cells (polymorphism) as well as an increase in the cell area change coefficient (polymegatism) and the average cell area were observed from corneal specular microscopic examination of individuals recovering from COVID-19 in the early period of the disease. These results may be important in understanding the systemic effects of the disease.

Middle- and long-term results after iris-fixated phakic intraocular lens implantation in myopic and hyperopic patients: a meta-analysis

The iris-fixated phakic intraocular lens (pIOL) has been available for over 25 years. To provide a clear picture of outcomes and risks, for this systematic review and meta-analysis, the literature was searched for reports on middle- and long-term effects. The iris-fixated phakic intraocular lens (pIOL) has been available for over 25 years. To provide a clear picture of outcomes and risks, for this systematic review and meta-analysis, the literature was searched for reports on middle- and long-term effects of iris-fixated pIOLs on myopic and hyperopic eyes with a follow-up of at least 2 to 4 years. Visual and refractive results after implantation for correction of myopia are positive and the complication rate is low. Endothelial cell loss appears to be at an acceptable rate, although the range of endothelial cell change is too wide to draw firm conclusions. Care should be taken when considering an iris-fixated pIOL for hyperopic eyes because complication rates, particularly pigment dispersion, might be higher than those in myopic eyes. More well-designed, long-term studies are needed, especially in hyperopic eyes. The authors advocate for standardized reporting of refractive surgery data. Initiatives proposed by journal authors and editors to achieve uniformity should be supported.

The effect of long-term hydroxychloroquine use on the corneal endothelium in patients with systemic lupus erythematosus

PURPOSE

To evaluate the effect of long-term effects of hydroxychloroquine (HCQ) use on the corneal endothelium in patients with systemic lupus erythematosus (SLE).

METHODS

The study included 30 eyes of 15 patients who used HCQ for at least five years and were followed up in the rheumatology clinic for SLE and 29 eyes of 15 patients newly diagnosed with SLE who had not taken any medication. All patients underwent complete ophthalmologic examinations, central corneal thickness measurements, endothelial cell counts and endothelial morphological examinations by specular microscopy.

RESULTS

The mean age was 41.25 ± 6.89 years in group 1 and 41.81 ± 5.78 years in group 2 (p = 0.737). The mean corneal endothelial cell density was 2662 ± 184 cells/mm2 in group 1 and 2649 ± 315 cells/mm2 in group 2 (p = 0.843). The percentage of cell hexagonality was 46.6 ± 11.8% in group 1 and 48.7 ± 13.8% in group 2 (p = 0.625). A difference was noted in endothelial cell variation in both groups, at 36.7 ± 6.9% in group 1 and 39.9 ± 6.2% in group 2 (p = 0.057) but not statistically significant. No difference was observed between the two groups in terms of central corneal thickness. The duration of HCQ use was negatively correlated with hexagonality (r = -0.564, p = 0.001) CONCLUSION: Long-term use of HCQ in SLE patients had no negative effect on endothelial cell density and cell variation, but a negative correlation existed between the duration of HCQ usage and hexagonality.

Improved Interchangeability with Different Corneal Specular Microscopes for Quantitative Endothelial Cell Analysis

Introduction

During our clinical practice and research, we encountered an interchangeability problem when using the SP-2000P and SP-3000P TopCon corneal specular microscopes (CSMs) (TopCon Medical Systems, Tokyo, Japan) regarding the endothelial cell count (ECC). We describe a method to improve interchangeability between these CSMs.

Methods

Five consecutive good-quality endothelial cell photographs were obtained in 22 eyes of 11 subjects. An ECC comparison between the two CSMs was performed after (I) gauging and calibration by the manufacturer, (II) adjustment of the magnification, (III) correction after external horizontal and vertical calibration.

Results

There was a statistically significant difference between the ECC of the SP-2000P and SP-3000P at the start. The SP-2000P counted an average of 500 cells/mm² more than the SP-3000P (p=0.00). After correction for magnification and determining a correction factor based on external calibration, the difference between the ECC of the SP-2000P and the SP-3000P was then found to be 0.4 cells/mm² and was not statistically significant (p=0.98).

Discussion

We propose a method for improving interchangeability, which involves checking magnification settings, re-checking magnification calibration with external calibration devices, and then calculating correction factors. This method can be applied to various specular or confocal microscopes and their associated endothelial cell analysis software packages to be able to keep performing precise endothelial cell counts and to enable comparison of ECCs when a CSM needs to be replaced or when results from different microscopes need to be compared.

Measurement of corneal thickness using Pentacam HR versus Nidek CEM-530 specular microscopy

Objective

To compare corneal thickness (CT) measurements using the CEM-530 (Nidal, Gamagori, Japan) and Pentacam HR (Oculus, Wetzlar, Germany).

Methods

The CT of 209 healthy subjects (209 right eyes) aged 24 to 89 years (71.35 ± 10.72 years) was measured at the corneal apex (CA), pupil center (PC), and thinnest point (TP) with the Pentacam HR and at the corneal center with the CEM-530 in random order at the same time of day.

Results

A good correlation but statistically significant difference was found between the CEM-530 and Pentacam HR measurements at the CA (6.10 ± 8.12 µm, R² = 0.8947), PC (7.46 ± 8.57 µm, R² = 0.8826), and TP (12.44 ± 10.04 µm, R² = 0.8392). Comparison of the two devices produced the following regression formulas: y = 0.8859x + 57.644 for the CA, y = 0.8852x +56.657 for the PC, and y = 0.8557x + 68.148 for the TP, where x is the CT obtained with the CEM-530 and y is that obtained with the Pentacam HR.

Conclusions

These findings indicate that the CEM-530 produces a thicker corneal measurement than the Pentacam HR. The herein-proposed correcting factors are needed to reliably compare these devices.

Significant differences between specular microscopy and corneal bank endothelial cell counts - a pilot study

BACKGROUND

It was shown recently that endothelial cell count performed by cornea banks overestimates the real number of endothelial cells. The aim of this study was to investigate the internal quality of preclinical ECD in human donor corneas using two widely used methods for endothelial cell counting, transmitted light microscopy used in organ culture tissue bank and clinically used specular microscopy.

METHODS

Twenty human donor corneas that could not be transplanted were included in this analysis. Differences in evaluating endothelial cell density (ECD) and hexagonal endothelial cell ratio (HEX) between clinical specular microscopy (CSM) and corneal bank transmitted light microscope (CBLM) were evaluated as well as differences between automated and manual cell counts.

RESULTS

Automated CBLM showed a higher ECD of 31.85% compared to automated CSM, while manual CBLM counting is 10.51% higher compared to manual CSM (p < 0.01). Further, higher average ECD values result in a higher difference between CSM and CBLM measurements. The manual CBLM ECDs were significantly higher compared to automated derived ECD from CSM (p < 0.01). However, no systematic bias can be detected when comparing the differences of the measurements with the average ECD measurements of both methods.

CONCLUSION

This preclinical pilot study confirmed a significant higher ECD using transmitted light microscopy in organ culture compared to clinical specular microscopy. This indicates that the early rapid decrease of EC universally observed after surgery might be partly artefactual.

On the regional variability of averaged cell area estimates for the human corneal endothelium in relation to the extent of polymegethism

Purpose

To assess variability in the coefficient of variation (COV) in cell area estimates when using different numbers of cells for endothelial morphometry.

Methods

Using non-contact specular microscopy images of the corneal endothelium, 4 sets of 20 cases were selected that included 200 cells and had overall (global) COV values of less than 30 (group 1), 31–40 (group 2), 41–50 (group 3) and over 50% (group 4). Subjects could be normal, or had ophthalmic disease (such as diabetes), a history of rigid or soft contact lens wear or were assessed after cataract surgery. A step-wise analysis was undertaken, 20 cells at a time, of the variability in cell area estimates when using different numbers of cells for the calculations.

Results

Variability in the average cell area values was higher if only 20–60 cells were used in the calculations and then tended to decrease. The standard deviation values on these average cell area values and the calculated COV showed the same overall trends and were more than twice as large for endothelia with marked polymegethism. Using more than 100 cells/image in markedly polymegethous endothelia only increased the variability in the calculations.

Conclusions

These analyses indicate that substantial region variability in cell area values can be expected in polymegethous endothelia. The analysis further confirm that using only small numbers of cells (e.g. less than 50/image) in such cases is likely to yield far less reliable estimates of COV.

Comparison of central corneal thickness and endothelial cell measurements by Scheimpflug camera system and two noncontact specular microscopes

PURPOSE

To investigate the correlation of Scheimpflug camera system and two noncontact specular microscopes in terms of central corneal thickness (CCT) and corneal endothelial cell morphology measurements.

METHODS

One hundred eyes of 50 healthy subjects were examined by Pentacam Scheimpflug Analyzer, CEM-530 (Nidek Co, Ltd, Gamagori, Japan) and CellChek XL (Konan Medical, California, USA) via fully automated image analysis with no corrections made. Measurement differences and agreement between instruments were determined by intraclass correlation analysis.

RESULTS

The mean age of the subjects was 36.74 ± 8.59 (range 22-57). CCTs were well correlated among all devices, with having CEM-530 the thinnest and CellChek XL the thickest measurements (intraclass correlation coefficient (ICC) = 0.83; p < 0.001 and ICC = 0.78; p < 0.001, respectively). Mean endothelial cell density (ECD) given by CEM-530 was lower than CellChek XL (2613.17 ± 228.62 and 2862.72 ± 170.42 cells/mm², respectively; ICC = 0.43; p < 0.001). Mean value for coefficient of variation (CV) was 28.57 ± 3.61 in CEM-530 and 30.30 ± 3.53 in CellChek XL. Cell hexagonality (HEX) with CEM-530 was higher than with CellChek XL (68.70 ± 4.16% and 45.19 ± 6.58%, respectively).

CONCLUSIONS

ECDs with CellChek XL and CEM-530 have good correlation, but the values obtained by CellChek XL are higher than CEM-530. Measurements for HEX and CV differ significantly and show weak correlation. Thus, we do not recommend interchangeable use of CellChek XL and CEM-530. In terms of CCTs, Pentacam, CEM-530 and CellChek XL specular microscopy instruments are reliable devices.

A novel method for examining corneal endothelial cell morphology in infants

Previous studies have suggested that central corneal endothelial cell density (ECD) decreases from 6,100 cells/mm² in neonates to 3,100 cells/mm² in 10-year-olds. Currently data on ECD in young children as well as the trend for ECD decrease during childhood is sparse because of the difficulty of examination using existing clinic-based specular microscopes. We developed a novel method of imaging young children intraoperatively with the goal of beginning to establish age-specific normative data for ECD and hexagonality of cells (%HEX). Children were imaged using our novel technique under general anesthesia or awake in clinic using a child-friendly technique. A total of 58 children were recruited (mean age, 5.50; range, 0.44-10.36). Our cohort displayed a significant linear decrease in ECD with age (r = -0.56, P < 0.001). No correlation was found between %HEX and age (r = -0.10, P = 0.48).