Measuring Corneal Haze by Using Scheimpflug Photography and Confocal Microscopy

Monitoring the transition from corneal ulceration to healed scar using a Scheimpflug tomography-based densitometry

PURPOSE

To compare corneal haze between active ulcer and healed scarring using a Scheimpflug densitometry.

MATERIALS AND METHODS

A prospective longitudinal study enrolled 30 patients (30 eyes) with ulcerative keratitis (UK). Each subject's corneal optical density (COD) was measured with a Scheimpflug corneal densitometry, Pentacam® AXL (Oculus GmbH, Wetzlar, Germany), at the active ulcerative and complete scarring stage. The COD data were analyzed through distinct methods (inbuilt, sorted annular partitions, and ulcer-matching densitometric maps). We compared different CODs to select the better index for clinically monitoring the transition from corneal ulceration to healed scar.

RESULTS

The CODs of the periphery (P = 0.0024) and outside of the active ulcer (P = 0.0002) significantly decreased after scarring. Partitioning the cornea into different depths and annular zones, the anterior layer, center layer, and the 2-6 mm annular zone had a more remarkable COD decrease after scar formation. The 3rd-sorted COD in the anterior layer revealed the highest area under the receiver-operating characteristic curves (0.709), in which 90% of subjects had COD reduction during the ulcer-to-scar transition.

CONCLUSIONS

Aside from subjective judgment based on clinical signs, the Scheimpflug tomography-based densitometry could provide objective and efficient monitoring of the corneal opacity evolution in UK patients. Because the 3rd-sorted annular COD is a better index than the inbuilt or mapping CODs in differentiating active ulcers from healed scars, this COD could be a clinically promising parameter to monitor the progression of UK patients.

Corneal Backscatter, Pachymetric Indices, and Ectasia Indices for the Assessment of Fuchs Endothelial Corneal Dystrophy

PURPOSE

To determine whether corneal backscatter, pachymetric indices, and ectasia indices derived from Scheimpflug tomography can identify Fuchs endothelial corneal dystrophy (FECD) corneas with abnormal tomography, the relationships between these parameters and tomographic edema in FECD, and if these parameters help predict improvement in central corneal thickness (CCT) after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Tomography maps of 132 eyes of 80 subjects with FECD were analyzed to determine how backscatter, pachymetric, and ectasia parameters compared with the instrument's normative database and if any predicted tomographic edema. Tomography maps from a separate group undergoing DMEK were split into derivation (48 eyes of 39 subjects) and validation (45 eyes of 41 subjects) subgroups to derive a predictive model of improvement in CCT after DMEK. Backscatter, pachymetric, and ectasia parameters were incorporated to determine if the model could be enhanced.

RESULTS

Among all ectasia, pachymetric, and backscatter parameters, at best only 65% of FECD corneas with definite tomographic edema could be identified based on the instrument's normative database. Among all parameters individually, the highest sensitivity for detecting tomographic edema was 77%. Anterior and mid-corneal backscatter featured in a model predicting improvement in CCT after DMEK with high performance in derivation (R2 = 0.79; 95% confidence interval, 0.65-0.87) and validation (R2 = 0.72; 95% confidence interval, 0.52-0.83) subgroups.

CONCLUSIONS

The Scheimpflug camera software program could not reliably detect abnormal tomography in FECD from corneal backscatter, pachymetric indices, or ectasia indices. Corneal backscatter contributes to, but does not enhance, a predictive model of improvement in CCT after DMEK.

Three-Dimensional Assessment of Descemet Membrane Reflectivity by Optical Coherence Tomography in Fuchs Endothelial Corneal Dystrophy

PURPOSE

This study aimed to evaluate Descemet membrane reflectivity using anterior segment optical coherence tomography (AS-OCT) in eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

We retrospectively assessed 144 eyes of 88 consecutive participants (41 FECD, 15 pseudophakic bullous keratopathies [BKs], and 32 healthy controls, 63.5 ± 16.5 years). FECD was graded 0 to 3 based on the guttae areas using specular microscopy. The sum of AS-OCT reflectivity of the 3-dimensional volume from 10 μm thickness from the endothelial surface of the cornea and residual stromal area was calculated as D sum (endo) and D sum (stroma) in the central area of 3- and 6-mm diameters, respectively. The D ES ratio was defined as the ratio of D sum (endo) to D sum (stroma). The percentage of the guttae area in the specular images was calculated using MATLAB. D sum (endo) and D ES ratio were compared among FECD, BK, and healthy controls.

RESULTS

D sum (endo) in FECD grade 3 was significantly higher than that in healthy control eyes, FECD patients with mild and moderate guttae, and BK (all P ≤ 0.040). The D ES ratio in FECD patients with mild to severe guttae (grade 1-3) was significantly higher than that in healthy control eyes and BK (all P ≤ 0.035). The percentage of the guttae area was significantly correlated with D sum (endo) (R = 0.488, P < 0.001 for 3 mm, R = 0.512, P < 0.001 for 6 mm) and D ES ratio (R = 0.450, P < 0.001 for 3 mm, R = 0.588, P < 0.001 for 6 mm).

CONCLUSIONS

Descemet membrane reflectivity in AS-OCT can be objective biomarkers for assessing guttae and FECD severity from early to end-stage FECD.

Systematic Review of the Diagnostic Criteria and Severity Classification for Fuchs Endothelial Corneal Dystrophy

PURPOSE

There are no defined diagnostic criteria and severity classification for Fuchs endothelial corneal dystrophy (FECD), which are required for objective standardized assessments. Therefore, we performed a systematic literature review of the current diagnosis and severity classification of FECD.

METHODS

We searched the Ovid MEDLINE and Web of Science databases for studies published until January 13, 2021. We excluded review articles, conference abstracts, editorials, case reports with <5 patients, and letters.

RESULTS

Among 468 articles identified, we excluded 173 and 165 articles in the first and second screenings, respectively. Among the 130 included articles, 61 (47%) and 99 (76%) mentioned the diagnostic criteria for FECD and described its severity classification, respectively. Regarding diagnosis, slitlamp microscope alone was the most frequently used device in 31 (51%) of 61 articles. Regarding diagnostic findings, corneal guttae alone was the most common parameter [adopted in 23 articles (38%)]. Regarding severity classification, slitlamp microscopes were used in 88 articles (89%). The original or modified Krachmer grading scale was used in 77 articles (78%), followed by Adami's classification in six (6%). Specular microscopes or Scheimpflug tomography were used in four articles (4%) and anterior segment optical coherence tomography in one (1%).

CONCLUSIONS

FECD is globally diagnosed by the corneal guttae using slitlamp examination, and its severity is predominantly determined by the original or modified Krachmer grading scale. Objective severity grading using Scheimpflug or anterior segment optical coherence tomography can be applied in the future innovative therapies such as cell injection therapy or novel small molecules.

Scheimpflug Corneal Densitometry Patterns at the Graft-Host Interface in DMEK and DSAEK: A 12-Month Longitudinal Comparative Study

BACKGROUND

To compare corneal densitometry (CD) patterns at the graft-host interface between Descemet Membrane Endothelial Keratoplasty (DMEK) and Descemet Stripping Automated Endothelial Keratoplasty (DSAEK). Corneal densitometry is a quantitative assessment that objectively evaluates corneal clarity and optical quality by measuring the light backscatter from the cornea.

METHODS

Fifty-one eyes that received DMEK or DSAEK surgery for corneal endothelium dysfunction were evaluated. The primary endpoint included CD patterns at the graft-host interface, which were assessed by the Pentacam HR device at the center point of the corneal horizontal meridian (CDcentral), and at six points on the central circumference of the cornea (with a total diameter of 4 mm) (CDI,II,III,IV,V,VI). Secondary endpoints included the best-corrected distance visual acuity (BCDVA), central corneal thickness (CCT), and graft thickness (GT). All of the evaluations were performed at follow-up appointments one, three, six and twelve months after the procedure.

RESULTS

DMEK showed a significant overall CD reduction of -7.9 ± 8.5 grayscale unit (GSU) compared to DSAEK (p < 0.001). In addition, the DMEK group showed significantly lower CDCentral,I,II,III,IV,V,VI values at follow-up appointments one, three, six and twelve months after the procedure compared to the DSAEK group (p < 0.001). BCDVA, CCT and GT were in favor of the DMEK group with a mean value of 0.39 ± 0.35 LogMar, 552.2 ± 71.1 µm and 11.03 ± 1.4 µm, respectively (p < 0.001).

CONCLUSIONS

CD patterns at the graft-host interface seem to be different depending on the endothelial keratoplasty procedure. This provides specific insight into CD changes in this critical region of surgery, which may provide a better understanding of the postoperative evolution of these patients.

Evaluation of corneal backward light scattering in type 2 diabetes mellitus

AIM

To compare the corneal backward light scattering values in type 2 diabetes mellitus (DM) patients with those of age and sex-matched healthy controls.

METHODS

The study included 30 patients (30 eyes) with type 2 DM and 30 control subjects (30 eyes). Duration of diabetes, most recent hemoglobin A1c levels, along with the status of diabetic retinopathy, and existing medical treatment of all subjects were recorded. All subjects underwent a complete ophthalmologic examination. In addition, backward light scattering (densitometry) was measured to assess changes in corneal transparency using tomography (Pentacam HR).

RESULTS

The type 2 DM patients included 12 males and 18 females and control subjects included 16 males and 14 females. The age was 50.40±7.80y (range: 40-68y) of the diabetic group and 49.30±9.50y (rang: 40-73y) of control group. The diabetic group demonstrated significantly higher mean densitometry values of the anterior (6-10 mm) zone (P=0.047), the total anterior layer (P=0.036) and the total cornea (P=0.043) than control group. The corneal densitometry of the diabetic eyes demonstrated no significant correlation with hemoglobin A1c levels and DM duration.

CONCLUSION

Diabetic group has higher densitometry in anterior corneal (6-10 mm) zone, total anterior cornea, and total cornea and with no correlation with hemoglobin A1c levels and DM duration.

Refractive outcomes after DMEK: meta-analysis

In this meta-analysis and systematic literature review of refractive outcomes after Descemet membrane endothelial keratoplasty (DMEK), the extent of the refractive shift and an overview of reasons for refractive shift after DMEK are provided. The PubMed library was screened for articles containing the terms "Descemet membrane endothelial keratoplasty," "DMEK," "Descemet membrane endothelial keratoplasty combined with cataract surgery," "triple-DMEK" combined with "refractive outcomes," "refractive shift," and "hyperopic shift." The refractive outcomes after DMEK were analyzed and compared using a fixed and random effects model. The overall mean change of the spherical equivalent outcome when compared with the preoperative value in cases of DMEK or when compared with the preoperative target refraction in cases of DMEK combined with cataract surgery was +0.43 diopters (D) (95% CI, 0.31-0.55). When DMEK is combined with cataract surgery, a target refraction of -0.5 D is recommended to achieve emmetropia. Changes in the posterior corneal curvature are identified as the main cause of the refractive hyperopic shift.

Seven-year corneal densitometry changes after small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis

This study aims to investigate the 7-year changes in corneal densitometry (CD) after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Forty-two eyes undergoing SMILE and thirty-one undergoing FS-LASIK were included in this retrospective study. CD was measured preoperatively and at 3 and 7 years postoperatively. Three concentric radial zones (0-2, 2-6, and 6-10 mm) of three different corneal depths (anterior 120 μm, posterior 60 μm, and central layer) were analyzed. In all three zones of the three corneal layers, no significant difference in CD was found between the two groups preoperatively and at 3 and 7 years postoperatively (all P > 0.05). All CD values in the three zones of the anterior and central layers significantly declined at 3 years postoperatively (all P < 0.001), and then increased at 7 years postoperatively compared to corresponding 3-year values (all P < 0.01). In the posterior layer, CD values in the 0-2-mm and 2-6-mm zones decreased at 3 years postoperatively (all P < 0.01) and continued to decrease at 7 years postoperatively (all P < 0.01). Similar CD trends were observed after SMILE and FS-LASIK. Posterior layer CD showed a decrease throughout the study period. In the anterior and central layers, CD values decreased and then increased at 7 years postoperatively. The transparency changes might have been due to age-related three-dimensional growth of collagen fibers and wound-healing reactions.

Distribution of 50-layer corneal densitometry values and related factors

PURPOSE

To investigate the distribution of 50 layers of corneal densitometry and related factors.

METHODS

Clinical data, including age, sex, central corneal thickness, corneal keratometry, and diopters, were collected from 102 healthy participants (102 eyes) in this retrospective study. The cornea was divided into 50 layers, and densitometry of each layer at 19 points was measured by the Pentacam. The value versus the depth curve was plotted. Paired-sample t test and one-way analysis of variance were used to compare densitometry in different regions or depth. Statistical significance was defined as P < .05.

RESULTS

The densitometry values of the Bowman membrane (10-14% depth), anterior stroma (14-30% depth), epithelium (0-10% depth), and Descemet membrane (94-98% depth) decreased sequentially, and the densitometry values of the middle and posterior stroma (30-94% depth) and endothelium (98-100% depth) were the lowest. The higher the degree of astigmatism, the higher the second densitometry peak (R = 0.277, P < .001). The densitometry values of the vertex and superior parts of the cornea were higher than those in the periphery and inferior parts, respectively (all P < .001). In the Bowman membrane, the densitometry is lowest in the inferior nasal part, while in the Descemet membrane, it is lowest in the inferior temporal part.

CONCLUSION

Two densitometry peaks appeared near the Bowman membrane and Descemet membrane. For different depths, the distribution of densitometry within a layer is different. We provide a methodological reference and data basis for corneal research based on local changes in densitometry, and help understand the details of corneal structure from an optical perspective through detailed layering and zoning analysis of densitometry.

Corneal optical density: Structural basis, measurements, influencing factors, and roles in refractive surgery

The cornea is the main refractive medium of the human eye, and its clarity is critical to visual acuity. Corneal optical density (COD) is an important index to describe corneal transparency. Intact corneal epithelial and endothelial cells, regular arrangement of collagen fibers in the stroma, and normal substance metabolism are all integral for the cornea to maintain its transparency. In the last two decades, the Pentacam Scheimpflug imaging system has emerged as a breakthrough for the measurement of COD (also called corneal densitometry). It has been found that a wide variety of factors such as age, refractive status, and corneal diseases can affect COD. Different corneal refractive surgery methods also change COD in different corneal regions and layers and affect visual acuity following the surgery. Thus, COD has gradually become a significant indicator to evaluate corneal health, one on which the attention of clinicians has been increasingly focused.

Corneal densitometry: an innovative method to quantitatively evaluate corneal changes after phacovitrectomy

BACKGROUND

To quantitatively investigate corneal changes and the correlation between corneal densitometry (CD) and endothelial parameters after phacovitrectomy.

METHODS

Thirty-eight eyes with idiopathic full-thickness macular holes (iFTMHs) and cataracts underwent phacovitrectomy. Examinations were conducted at baseline and Day 1, Day 7, Month 1, and Month 3 postoperatively. CD and central corneal thickness (CCT) were measured using Pentacam. Corneal endothelial cell density (ECD), coefficient of variation (CV), and hexagonality (HEX) were measured using specular microscopy.

RESULTS

ECD and HEX significantly decreased after surgery and the change in HEX occurred prior to CV. CCT increased immediately after surgery and recovered 3 months postoperatively. CD values increased significantly 1 day after surgery and then gradually decreased. For CD in the 0-2 mm zone, it took 1 month to recover in the central and posterior layers and 3 months in the anterior and total layers. For CD in the 2-6 mm zone, the central layer recovered at Day 7, the anterior and total layers recovered at 1 month, and the posterior layer did not recover until 3 months postoperatively. The CD within all layers in the 0-2 mm zone was positively correlated with CCT. Posterior CD in the 0-2 mm zone was negatively correlated with ECD and HEX.

CONCLUSIONS

CD is not only correlated with CCT, ECD, and HEX but also reflects the state of the whole cornea and each layer. CD can be an objective, rapid, and noninvasive tool that reflects corneal health and undetectable edema and monitors the process of lesion repair.

TRIAL REGISTRATION

This study was registered with the Chinese Clinical Trial Registry (31/10/2021, ChiCTR2100052554).

Diurnal Variation in Straylight in Patients With Fuchs Endothelial Corneal Dystrophy and Controls

PURPOSE

The goal of this study was to investigate diurnal changes in intraocular straylight in relation to other corneal parameters and subjective complaints in patients with Fuchs endothelial dystrophy and healthy controls.

METHODS

This is a prospective study conducted in 2 tertiary care hospitals in Germany and the Netherlands. Patients with Fuchs endothelial dystrophy (n = 71) and healthy controls (n = 34) were included. Patients with Fuchs dystrophy were grouped by the presence of subjective complaints and measured over multiple time points during the day. Measurements included intraocular straylight using the C-Quant and corneal thickness and backscatter using a Scheimpflug camera. A separate group of healthy controls was measured intensively with repeated straylight measurements directly after waking. An exponential decay model was used to model the diurnal change.

RESULTS

Healthy controls showed an average straylight baseline of 1.17 log(s) with an increase in straylight after waking of 0.22 log(s). In the repeated measurements subgroup, the increase in morning straylight lasted for 22 minutes. Patients with Fuchs dystrophy showed a morning increase in straylight of 0.21 log(s) present up to 4 hours after waking before reaching an average baseline of 1.30 log(s). Straylight was positively correlated with anterior corneal backscatter, r = 0.21, P = 0.022, and corneal thickness, r = 0.46, P < 0.01.

CONCLUSIONS

Healthy eyes experience a diurnal straylight increase similar to patients with Fuchs dystrophy in intensity. However, in Fuchs dystrophy, the resolution of increased straylight is prolonged over multiple hours compared with minutes in healthy eyes. This suggests pathological exacerbation of a physiological diurnal change. This mechanism can play a role in subjective complaints experienced by patients with Fuchs dystrophy.

The effect of anterior segment parameters on surgical success of Descemet membrane endothelial keratoplasty: a prospective study

PURPOSE

To investigate how anterior segment parameters affect the success of Descemet membrane endothelial keratoplasty (DMEK) in patients with endothelial insufficiency without stromal opacities and to identify factors predisposing them to repeat keratoplasty.

METHODS

Our prospective observational study included patients who underwent primary DMEK for Fuchs' endothelial dystrophy and pseudophakic bullous keratopathy between March 2019 and March 2020. After a detailed ophthalmologic examination, corneal topographic analysis, anterior segment optical coherence tomography (AS-OCT) scans, endothelial cell density (ECD) and axial length (AL) measurements were performed. Surgical success was defined as no endothelial dysfunction during follow-up. Changes in the parameters and how preoperative parameters affect surgical success were investigated.

RESULTS

In 43 eyes of 43 patients (mean age: 68.58 ± 8.51 years), mean visual acuity was 1.73 ± 0.74 LogMAR before DMEK and 0.31 ± 0.29 LogMAR in the final visit. Central corneal thickness (CCT, p = 0.026) and mean anterior chamber depth (ACD, p = 0.001) affected surgical success. Preoperative CCT values greater than 770 µm increased the risk of repeat keratoplasty by 8.75-fold, whereas preoperative ACD values less than 2.5 mm increased the risk by 2.92-fold.

CONCLUSION

Preoperative higher CCT and lower ACD values were associated with surgical failure after DMEK. Early surgery may be considered for more successful results.

TRIAL REGISTRATION

This prospective study has been registered on the ClinicalTrials.gov system with the registration number NCT04420429 on 06/06/2020.

Graft Detachment after Descemet Membrane Endothelial Keratoplasty with and without Cataract Surgery

PURPOSE

To evaluate graft detachment after Descemet membrane endothelial keratoplasty (DMEK) in pseudophakic eyes and DMEK combined with cataract surgery (triple DMEK).

DESIGN

Analysis of 3 single-center prospective cohort studies and 1 randomized controlled trial.

PARTICIPANTS

Participants with Fuchs' endothelial corneal dystrophy.

METHODS

A validated neural network for image segmentation quantified graft detachment on anterior segment OCT (AS-OCT) images 3 days after DMEK and at the 2-week postoperative visit. Area and volume of graft detachment were compared between DMEK only and triple DMEK using generalized estimating equation models and adjusting for participant age and the size of the air bubble.

MAIN OUTCOME MEASURES

Area and volume of DMEK graft detachment.

RESULTS

Among 207 participants with 270 eyes included, 75 pseudophakic eyes had DMEK only and 195 eyes had triple DMEK. A total of 147 eyes had less than one third of detachment at day 3. In 139 of these eyes (95%), detachment was still less than one third at the 2-week scan, indicating that postoperative graft detachment at 2 weeks occurred mainly in eyes with early detachment. When superimposing all 3-dimensional maps from 2 weeks after surgery, the central graft was mainly attached and detachment was located at the graft margin. The mean area of graft detachment decreased from 28% in DMEK only and 38% in triple DMEK to 16% in DMEK only and 25% in triple DMEK at the 2-week postoperative visit. At 2 weeks, the mean area of detachment was 1.85-fold higher (95% confidence interval [CI], 1.34-2.56) and the mean volume was 2.41-fold higher (95% CI, 1.51-3.86) in triple DMEK compared with DMEK. A total of 46 eyes received rebubbling procedures, with 7 eyes (9%) in the DMEK group and 39 eyes (20%) in the triple DMEK group (adjusted risk ratio, 3.1; 95% CI, 1.3-7.1), indicating that rebubbling was more common in eyes undergoing triple DMEK.

CONCLUSIONS

Automated segmentation of AS-OCT images allowed precise quantification of graft detachment over time and identified DMEK combined with cataract surgery as a risk factor. Frequency of operative follow-up might be guided by extent of detachment in the first postoperative days after DMEK.

Loss of Corneal Nerves and Corneal Haze in Patients with Fuchs' Endothelial Corneal Dystrophy with the Transcription Factor 4 Gene Trinucleotide Repeat Expansion

Objective

Seventy percent of Fuchs' endothelial corneal dystrophy (FECD) cases are caused by an intronic trinucleotide repeat expansion in the transcription factor 4 gene (TCF4). The objective of this study was to characterize the corneal subbasal nerve plexus and corneal haze in patients with FECD with (RE+) and without the trinucleotide repeat expansion (RE-) and to assess the correlation of these parameters with disease severity.

Design

Cross-sectional, single-center study.

Participants

Fifty-two eyes of 29 subjects with a modified Krachmer grade of FECD severity from 1 to 6 were included in the study. Fifteen of the 29 subjects carried an expanded TCF4 allele length of ≥ 40 cytosine-thymine-guanine repeats (RE+).

Main Outcomes Measures

In vivo confocal microscopy assessments of corneal nerve fiber length (CNFL), corneal nerve branch density, corneal nerve fiber density (CNFD), and anterior corneal stromal backscatter (haze); Scheimpflug tomography densitometry measurements of haze in anterior, central, and posterior corneal layers.

Results

Using confocal microscopy, we detected a negative correlation between FECD severity and both CNFL and CNFD in the eyes of RE+ subjects (Spearman ρ = -0.45, P = 0.029 and ρ = -0.62, P = 0.0015, respectively) but not in the eyes of RE- subjects. Additionally, CNFD negatively correlated with the repeat length of the expanded allele in the RE+ subjects (Spearman ρ = -0.42, P = 0.038). We found a positive correlation between anterior stromal backscatter and severity in both the RE+ and RE- groups (ρ = 0.60, P = 0.0023 and ρ = 0.44, P = 0.024, respectively). The anterior, central, and posterior Scheimpflug densitometry measurements also positively correlated with severity in both the RE+ and RE- groups (P = 5.5 × 10^-5, 2.5 × 10^-4, and 2.9 × 10^-4, respectively, after adjusting for the expansion status in a pooled analysis. However, for patients with severe FECD (Krachmer grades 5 and 6), the posterior densitometry measurements were higher in the RE+ group than in the RE- group (P < 0.05).

Conclusions

Loss of corneal nerves in FECD supports the classification of the TCF4 trinucleotide repeat expansion disorder as a neurodegenerative disease. Haze in the anterior, central, and posterior cornea correlate with severity, irrespective of the genotype. Quantitative assessments of corneal nerves and corneal haze may be useful to gauge and monitor FECD disease severity in RE+ patients.

Predicting Corneal Improvement after Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Corneal Dystrophy

PURPOSE

To develop a model to predict corneal improvement after Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial corneal dystrophy (FECD) from Scheimpflug tomography.

DESIGN

Cross-sectional study.

PARTICIPANTS

Forty-eight eyes (derivation group) and 45 eyes (validation group) with a range of severity of FECD undergoing DMEK.

METHODS

Scheimpflug images were obtained before and after DMEK. Before DMEK, pachymetry map and posterior elevation map patterns were quantified by a special image analysis program measuring tomographic features of edema (loss of regular isopachs, displacement of the thinnest point of the cornea, posterior surface depression). Image-derived novel parameters were combined with instrument-derived parameters, and the relative influences of parameters associated with the change in central corneal thickness (CCT) after DMEK in the derivation group were determined by using a gradient boosting machine learning model. The parameters with highest relative influence were then fit in a linear regression model. The derived model was applied to the validation group. Correlations and agreement were assessed between predicted and observed changes in CCT.

MAIN OUTCOME MEASURES

Predictive power (R ²) and mean difference between predicted and observed change in CCT.

RESULTS

The gradient boosting machine model identified 4 novel parameters of isopach circularity and eccentricity and 1 instrument-derived parameter (posterior surface radius); preoperative CCT was a poor predictor. In the derivation group, the model strongly predicted the change in CCT after DMEK (R ² = 0.80; 95% confidence interval [CI], 0.71-0.89) and the mean difference between predicted and observed change was, by definition, 0 μm. When the same 5 parameters were fit to the validation group, the model performed very highly (R ² = 0.89; 95% CI, 0.84-0.94). When the coefficient estimates from the derivation model were used to predict the change in CCT in the validation group, the predictive power was also high (R ² = 0.78; 95% CI, 0.68-0.88), and the mean difference was 4 μm (predicted minus observed).

CONCLUSIONS

Scheimpflug tomography maps of corneas with FECD can predict the improvement in CCT after DMEK, independent of preoperative corneal thickness measurement. The model could be applied in clinical practice or for clinical research of FECD.

Corneal Oedema: Aetiology, Diagnostic Testing, and Treatment

Corneal oedema results from an underlying pathology, which can be diverse in origin, and may be mechanical, dystrophic, or inflammatory, and affect any layer of the cornea. Diagnostic tools such as Scheimpflug imaging and anterior segment optical coherence tomography have standardised quantification of corneal oedema and have become important aids in clinical practice. Timely diagnosis and treatment are key to preventing irreversible damage to the corneal ultrastructure, such as anterior corneal fibrosis or endothelial cell damage. The oedema usually resolves quickly when the underlying cause has been addressed. Symptomatic treatment using hyperosmolar agents has failed to show any benefits in oedema resolution or improvement in visual acuity compared to placebo. In contrast, rho-associated protein kinase (ROCK) inhibitors offer a promising option for medical treatment in cases of endothelial dysfunction, but their safety and efficacy must be further validated in large scale clinical trials. Until then, endothelial or penetrating keratoplasties remain the mainstay treatment where structural changes to the cornea have occurred.

Isolation and Propagation of Human Corneal Stromal Keratocytes for Tissue Engineering and Cell Therapy

The human corneal stroma contains corneal stromal keratocytes (CSKs) that synthesize and deposit collagens and keratan sulfate proteoglycans into the stromal matrix to maintain the corneal structural integrity and transparency. In adult corneas, CSKs are quiescent and arrested in the G0 phase of the cell cycle. Following injury, some CSKs undergo apoptosis, whereas the surviving cells are activated to become stromal fibroblasts (SFs) and myofibroblasts (MyoFBs), as a natural mechanism of wound healing. The SFs and MyoFBs secrete abnormal extracellular matrix proteins, leading to corneal fibrosis and scar formation (corneal opacification). The issue is compounded by the fact that CSK transformation into SFs or MyoFBs is irreversible in vivo, which leads to chronic opacification. In this scenario, corneal transplantation is the only recourse. The application of cell therapy by replenishing CSKs, propagated in vitro, in the injured corneas has been demonstrated to be efficacious in resolving early-onset corneal opacification. However, expanding CSKs is challenging and has been the limiting factor for the application in corneal tissue engineering and cell therapy. The supplementation of serum in the culture medium promotes cell division but inevitably converts the CSKs into SFs. Similar to the in vivo conditions, the transformation is irreversible, even when the SF culture is switched to a serum-free medium. In the current article, we present a detailed protocol on the isolation and propagation of bona fide human CSKs and the morphological and genotypic differences from SFs.

Repeatability of Corneal Densitometry Measurements using a Scheimpflug Camera in Healthy Normal Corneas

Purpose

To determine the repeatability of corneal densitometry measured by the Scheimpflug imaging system.

Methods

This cross-sectional study was conducted on photorefractive keratectomy candidates. One eye of each participant underwent imaging using Pentacam HR three times, 10 min apart. The repeatability of densitometry measurements was evaluated in four concentric annuli around the corneal apex and in different corneal depths. The repeatability of the measurements was evaluated using the intraclass correlation coefficient (ICC), repeatability coefficient (RC), and coefficient of variation (CV). The difference of repeatability between layers and zones was tested by tolerance index (TI).

Results

Sixty eyes of sixty patients with a mean age of 27.76 ± 3.93 years were studied. Half of the participants were female (n = 30, 50%). ICC was above 0.9 in all corneal parts. The posterior layer and central zones showed the least variability of densitometry measurements considering the CV values. The RC was 2.06, 1.17, and 0.92 in anterior, central, and posterior layers, respectively. The RC was 0.88, 0.71, 1.51, and 4.56 in 0-2, 2-6, 6-10, and 10-12 mm circles, respectively. Only the reliability of densitometry in 10-12 mm annulus was statistically lower than the central zone (TI = 0.71).

Conclusions

Corneal densitometry measurements provided by the Pentacam had good repeatability. The repeatability of densitometry measurements decreased from the center to the periphery (with an exception for 0-2 mm and 2-6 mm) and from the posterior to the anterior of the cornea. The reliability of the 10-12 mm zone was markedly less than other zones.

Epithelial Flap Corneal Cross-linking

PURPOSE

To compare standard epithelium-off corneal cross-linking (standard Epi-Off CXL) to corneal cross-linking with an epithelial flap (Epi-Flap CXL).

METHODS

Patients who had undergone sequential bilateral CXL for progressive keratoconus were included in this comparative interventional case series. One eye was treated with the Epi-Off CXL technique and the fellow eye with the Epi-Flap CXL technique. Postoperative pain was measured using the Verbal Rating Scale and corneal densitometry using a Scheimpflug camera. Sex, age, corrected distance visual acuity, keratometry, and corneal thickness were also recorded.

RESULTS

Twenty-four eyes of 12 patients with keratoconus with a mean age of 27.15 ± 5.15 years were included. The Verbal Rating Scale scores were significantly lower in patients who had Epi-Flap CXL on the first (1.00 [interquartile range (IQR): 0.00 to 1.00] vs 3.00 [IQR: 3.00 to 3.75], P = .01) and third (0.00 [IQR: 0.00 to 1.00] vs 1.00 [IQR: 0.00 to 1.00], P = .01) postoperative day compared to the Epi-Off CXL group. No pain was observed in both groups after the third day. After 12 months, the Epi-Flap CXL group showed significantly less anterior corneal haze (measured as corneal densitometry) compared to the patients treated with Epi-Off CXL (P = .01). Both groups demonstrated stability of keratometry and corneal thickness at 12 months after CXL (P < .01).

CONCLUSIONS

Epi-Flap CXL is associated with less postoperative pain and anterior stromal haze in patients undergoing CXL for progressive keratoconus with no loss of efficacy. [J Refract Surg. 2021;37(11):741-745.].

Effect of Laser-assisted Subepithelial Keratectomy with Mitomycin C on Corneal Optical Density Measured with Confocal Microscopy

SIGNIFICANCE

The development of confocal microscopy allows one to obtain high-resolution corneal images like its optical density. Some studies have evaluated the optical density with Scheimpflug cameras in the early post-operative period after photorefractive keratectomy, but no studies have evaluated the long-term evolution of optical density after surface ablation when mitomycin C is used.

PURPOSE

This work aimed to study the changes in corneal optical density measured with confocal microscopy in eyes treated with laser-assisted subepithelial keratectomy (LASEK) and intraoperative mitomycin C (MMC) to correct myopia.

METHODS

A study of 24 consecutive myopic eyes that underwent LASEK with 0.02% MMC and a control group of 24 healthy nontreated eyes was performed. Optical density was measured using the images by the confocal microscopy of the Heidelberg Retina Tomograph II with the Rostock Cornea Module. An analysis of confocal microscopy images was performed using the ImageJ software to obtain the optical density, in gray-scale units (GSU). The optical density of the stromal bed was evaluated 3 months, 15 months, and 3 years after surgery and was compared with the optical density at the equivalent depth of the stroma in controls.

RESULTS

The mean values of optical density for the LASEK group were 81.7 ± 9.7, 78.6 ± 11.7, and 73.6 ± 18.7 GSU at 3 months, 15 months, and 3 years, respectively, and it was 61.8 ± 8.2 GSU for the control group. A statistically higher optical density 3 and 15 months after LASEK with MMC was found compared with controls (P < .001). No significant difference was found in optical density at 3 years post-operatively.

CONCLUSIONS

Our study suggests that, after LASEK with MMC, the anterior corneal stroma has a higher optical density at 3 and 15 months post-operatively, which gradually returns to normal values 3 years after surgery.

Hyperosmolar Eye Drops for Diurnal Corneal Edema in Fuchs' Endothelial Dystrophy: A Double-Masked, Randomized Controlled Trial

PURPOSE

The Eye Drops for Early Morning-Associated Swelling (EDEMAS) trial assessed the efficacy of hyperosmolar eye drops on corneal edema resolution.

DESIGN

Double-masked, randomized controlled trial of hyperosmolar eye drops.

PARTICIPANTS

Participants with Fuchs' dystrophy scheduled for Descemet membrane endothelial keratoplasty.

METHODS

One eye was randomized to hyperosmolar eye drops (treatment); the fellow eye was randomized to artificial tears (placebo). After baseline examination in the afternoon, corneas were examined using Scheimpflug tomography after eye opening in the morning. Participants received eye drops twice. Imaging was repeated every 30 minutes up to 4 hours.

MAIN OUTCOME MEASURES

Decrease in central corneal thickness 1 hour after eye opening (primary end point), corneal thickness, subjective visual function, glare, visual acuity, and adverse events (AEs) (secondary end points).

RESULTS

A total of 68 participants received the allocated intervention (59 eyes received treatment; 55 eyes received placebo). All eyes had stromal edema; none had epithelial edema. Corneal thickness was 626 μm in the treatment arm and 622 μm in the placebo arm after eye opening, indicating an early morning edema compared with baseline of +21 μm and +24 μm, respectively. Decrease in corneal thickness after 1 hour was -10.5 μm in the treatment arm (95% confidence interval [CI], -12.8 to -8.2) and -11.2 μm (95% CI, -13.6 to -8.9) in the placebo arm (between-arm difference, 0.7 μm, 95% CI, -2.0 to 3.5; P = 0.59), indicating no clinically relevant effect of hyperosmolar eye drops on early morning corneal edema. Results were not compatible with a relevant treatment effect on corneal thickness, visual acuity, and glare over the entire course of the study. Increase in subjective visual function was less rapid in the treatment arm than in the placebo arm. Adverse events, most commonly burning after eye drop application, were more common with treatment (30 eyes) than placebo (1 eye; risk difference, 49 percentage points; 95% CI, 36-62).

CONCLUSIONS

In this double-masked, randomized controlled trial, resolution of early morning stromal edema was not accelerated by hyperosmolar eye drops, which more frequently caused AEs. These results are not compatible with a clinically relevant effect of hyperosmolar eye drops and do not support their routine use.

Predicting Edema Resolution After Descemet Membrane Endothelial Keratoplasty for Fuchs Dystrophy Using Scheimpflug Tomography

Importance

Predicting the extent of corneal edema resolution after Descemet membrane endothelial keratoplasty (DMEK) may help in preoperative decision-making by identifying patients who may benefit from restoring endothelial function.

Objective

To develop and validate a predictive model for edema resolution after DMEK using Scheimpflug tomographic imaging.

Design, Setting, and Participants

Two prospective studies recruited participants with advanced Fuchs dystrophy at a university-based tertiary referral center between July 1, 2017, and August 31, 2019. Analyses were designed in November 2019 and completed on June 30, 2020. Development of a predictive model using linear least absolute shrinkage and selection operator regression was conducted in a derivation cohort (100 eyes). Overall performance, discrimination, and calibration were tested in the separate validation cohort (32 eyes).

Exposures

Preoperative Scheimpflug parameters and patient-reported visual disability were considered as potential predictors of edema resolution: (1) tomographic features (irregularity of lines of equal corneal thickness, displacement of the thinnest point of corneal thickness from the inferior-temporal quadrant, and absolute amount of focal posterior corneal depression), (2) standardized anterior and posterior corneal backscatter, (3) preoperative central corneal thickness, and (4) Fuchs dystrophy-specific visual disability.

Main Outcomes and Measures

Decrease in central corneal thickness after DMEK indicative of edema resolution.

Results

Of the 88 patients included in the analysis, 54 were women (61%); median age was 68 years (interquartile range [IQR], 59-76 years). A median of 13 months after DMEK (IQR, 9-16 months), median corneal thickness was 77 μm lower (IQR, 51-94 μm) in the derivation cohort and 75 μm lower in the validation cohort (IQR, 54-96 μm) than before surgery. Per 10-μm edema resolution, eyes gained 0.66 Early Treatment Diabetic Retinopathy Study letters (95% CI, 0.09-1.23) in best-corrected visual acuity. Three tomographic features were present in 68 of 100 eyes (68%) in the derivation cohort and in 18 of 32 eyes (56%) in the validation cohort before DMEK and in only 1 of 132 eyes (1%) after DMEK. To predict edema resolution after DMEK based on preoperative assessment, 5 variables were selected by the statistical learning algorithm: nonparallel isopachs, focal posterior depression, anterior and posterior corneal backscatter, and central corneal thickness. In the separate validation cohort, the model showed high overall performance, discrimination, and calibration.

Conclusions and Relevance

These post hoc analyses of prospective cohorts support a model for use in the prediction of edema resolution after DMEK using Scheimpflug measurement to identify patients benefitting most from DMEK.

A four-year observation of corneal densitometry after implantable collamer lens V4c implantation

Background

To observe the changes in corneal densitometry (CD) with a Pentacam after implantable collamer lens (ICL) V4c implantation in myopia patients, and to investigate potential influencing factors.

Methods

We reviewed 65 eyes of 33 patients (mean age, 29.08±5.54 years) with myopia or myopic astigmatism who underwent ICL V4c implantation. Clinic parameters and Pentacam images of corneal topography and CD were obtained pre- and postoperatively.

Results

After an average of 52±2.2 months follow-up, the efficacy and safety indexes assessed at the last follow-up were 1.03±0.18 and 1.21±0.21, respectively. Except in the central annular zone of 0-2 mm, the CD values increased significantly at postoperative day 1 and decreased significantly until postoperative 1 year (P<0.05). The increase in CD values at different annular zones at postoperative day 1 was ranked as: 0-2 mm <2-6 mm < 6-10 mm. No significant difference was observed in corneal density at 1 week, 1 month, and 1-year follow-up when compared with the preoperative value (P>0.05). The CD value at 4 years follow-up increased significantly and correlated positively with age and preoperative uncorrected distance visual acuity, and negatively with preoperative spherical equivalent and intraocular pressure (IOP) (P<0.05).

Conclusions

ICL V4c implantation demonstrated safety and efficacy for myopia correction. The CD value increased at 4 years postoperatively and correlated with age, preoperative spherical equivalent, uncorrected distance visual acuity, and IOP.

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

Corneal Scheimpflug Densitometry in Photorefractive Keratectomy Candidates

PURPOSE

To describe the normative data of corneal densitometry in photorefractive Keratectomy (PRK) candidates by using a Scheimpflug camera.

METHODS

Five hundred twenty-two eyes of 261 PRK candidates that underwent comprehensive optometric and ophthalmic examinations were enrolled in this study. Corneal densitometry values were obtained using a Scheimpflug camera (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) and displayed in grayscale units (GSU).

RESULTS

Of 261 participants, 187 (71.6%) were women. The mean age of the participants was 28.79 ± 5.02 years (range: 21-40 years). The mean entire corneal densitometry was 14.86 ± 2.37 GSU. According to corneal depth, maximum and minimum densitometry values were seen in the anterior (30.28 ± 7.42 GSU) and posterior (9.86 ± 2.08 GSU) layers, respectively (P < 0.001). Based on the annulus over the cornea, the highest and lowest densitometry values were seen in the 10- to 12-mm (21.31 ± 4.26 GSU) and 2- to 6-mm zones (13.26 ± 2.34 GSU), respectively. However, this difference was not seen after 35 years of age. Individuals aged 30 to 35 years showed higher corneal densitometry values compared with subjects aged 20 to 25 years old (P < 0.001). In generalized linear models, the corneal thickness was associated with the densitometry value in the central and posterior corneal layers. There were no significant differences in sex and refractive errors among participants.

CONCLUSIONS

This study provided normal corneal densitometry data in PRK candidates. Corneal densitometry increased with age until 35 years of age and then decreased thereafter. This finding should be considered in patient selection for PRK and their postoperative examinations.

Evaluation and grading of Kayser-Fleischer ring in Wilson disease by Scheimpflug camera

PURPOSE

Evaluation the anterior segment parameters of Wilson disease patients with Kayser-Fleischer ring, the diagnostic power of Scheimpflug imaging for Kayser-Fleischer ring and suggest a scoring system.

MATERIALS AND METHODS

A total of 44 eyes of 22 Wilson disease patients with Kayser-Fleischer ring and 40 right eyes of 40 healthy age matched subjects were enrolled to the study. Serum ceruloplasmin and urine copper/24 hours levels were recorded. Anterior segment parameters including steep and flat keratometry, corneal thickness at central, 2, 4, 6, 8 and 10 mm, anterior chamber angle width, volume and depth, corneal volume, pupillary diameter were evaluated by Scheimpflug imaging. Images of cornea were scored according to Kayser-Fleischer ring size.

RESULTS

Serum ceruloplasmin level was below 10 mg/dL in 17 patients and was 12, 18.5, 20, 22, 37 mg/dl in the remaining five patients. Urinary copper/24 hours was 249.55 ± 304.14 (23-1050) µg/day. Central corneal thickness and corneal thickness at 2 mm were statistically different (p values 0.02, 0.04, respectively). Scheimpflug images apparently showed Kayser-Fleischer ring as a hyper-reflective band at the corneal endothelial surface. Kayser-Fleischer ring in 24 eyes was grade 1, 16 eyes were grade 2 and 4 eyes were grade 3.

CONCLUSION

Scheimpflug imaging seems to be a helpful diagnostic tool for detecting and grading the Kayser-Fleischer ring. Corneal thickness in Wilson disease patients with Kayser-Fleischer ring tends to be higher, so that the possible affection in corneal thickness should be kept in mind for clinical evaluation of these patients.

Visual rehabilitation of patients with corneal diseases

BACKGROUND

Although most patients with visual impairment due to corneal diseases can be treated successfully with surgery, some require visual rehabilitation to restore reading ability. To evaluate the best LVAs especially in terms of reading speed and characterize this specific patient group we performed a prospective, randomized cross-over trial.

METHODS

All 34 patients underwent a detailed examination (slit-lamp, funduscopy, SD-OCT, ETDRS) as screening. Only patients with corneal diseases without other ocular diseases were included. Reading-speed was assessed with International-Reading-Speed-Texts (IReST) consecutively with five different LVAs (low vision aids) during one day in a randomized cross-over design. Corneal haze was quantified with corneal densitometry (Pentacam).

RESULTS

Patients were either visually impaired (n = 28), severely impaired (n = 4) or legally blind (n = 2). Patients read significantly faster with LVAs (p < 0.0001). Fastest reading speed could be achieved with video magnifier (CCTV). Optical magnifier and portable-electronic magnifier enabled significantly lower reading speeds (p < 0.01). In a subgroup of patients (VA < 3/60,n = 6) black background enabled patients to read significantly faster compared to white background (p = 0.03).

CONCLUSION

Patients with low magnification requirement can be treated successfully with optical LVAs and portable-electronic magnifiers. More severely afflicted patients need a CCTV. Black background enables fastest reading-speeds, probably due to less blinding. Visual impairment can be estimated with corneal densitometry. Our trial confirms the capability of LVAs to successfully restore the reading ability in patients with corneal diseases, which is a crucial part of visual rehabilitation.

TRIAL REGISTRATION

This trial was registered at the German Clinical Trials Register as DRKS00010887 at 09.08.2016.

Oral l-Cysteine Supplementation Enhances the Long Term-Effect of Topical Basic Fibroblast Growth Factor (bFGF) in Reducing the Corneal Haze after Photorefractive Keratectomy in Myopic Patients

We aimed at evaluating the long-term effects of l-cysteine oral supplementation to basic fibroblast growth factor (bFGF) eye-drops on corneal re-epithelization and transparency in myopic patients subjected to photorefractive keratectomy (PRK). Forty patients subjected to bilateral PRK for myopia were enrolled and randomly divided into two groups receiving an additional therapy together with the standard postoperative treatment consisting in local tobramycin 0.3%, dexamethasone 0.1%, diclofenac 0.1%, and 0.2% hyaluronate. Group 1 included 20 patients (11 males and 9 females; 34.09 ± 8 years of age) receiving only bFGF eye-drops (10 μg/10 μL) four times a day for 7 days starting from the day of surgery; Group 2 included 20 patients (12 males and 8 females; 37.35 ± 11.5 years of age) who were postoperatively administered with topical basic fibroblast growth factor (bFGF; 10 μg/10 μL) four times a day for 7 days plus oral l-cysteine supplementation (500 mg/capsule) once a day for 15 days, starting 7 days before PRK. Patients were followed-up for 12 months. Clinical ophthalmologic parameters were recorded for all the 80 examined eyes. The corneal transparency was evaluated in vivo by slit lamp and confocal microscopy. The data showed that: (a) the corneal haze occurred in a smaller percentage of the patients who were postoperatively administered with topical bFGF plus oral l-cysteine supplementation (Group 2) compared to patients who received only bFGF (Group 1); (b) at 6 months of follow-up, the stromal mean image brightness of the patients belonging to Group 2 was significantly lower than that of the Group 1 (p < 0.03), and, interestingly, the difference was even more evident at 12 month from the treatment (p < 0.001). Moreover, the final mean of the spherical equivalent refraction was −0.06 ± 0.2 D in Group 1 and −0.08 ± 0.3 D in Group 2, whereas the final uncorrected distance visual acuity (UDVA) was equal or superior to 20/25 in 100% of eyes in both Group 1 and 2. Post refractive patients can benefit from the administration of l-cysteine before the surgery and in association with bFGF in the early postoperative period, showing a faster corneal re-epithelization able to prevent corneal haze in the long-term recovery.

Incidence and quantification of corneal haze by Pentacam Scheimpflug densitometry following photorefractive keratectomy for myopia in virgin and post corneal transplant eyes with dark irides

PURPOSE:

To assess the incidence and quantification of corneal haze after myopic photorefractive keratectomy in virgin and post corneal transplant eyes with dark irides.

METHODS:

In this retrospective study at the tertiary eye hospital, the corneal haze was evaluated by slit-lamp and quantified by Pentacam Scheimpflug densitometry after myopic photorefractive keratectomy with mitomycin C in virgin eyes (group I) and post corneal transplant eyes (group II) with dark irides over 12 months.

RESULTS:

Group I compromised 126eyes from 77patients (35males and 42females) aged 31.31 years (24.11–36.18 years), and group II compromised 44eyes from 33patients (18males and 15females) aged of 32.25 years (26.15–36.66 years). The incidence of corneal haze was 9.5% (95%CI: 5.0%–16%) and 6.8% (95%CI: 1.4–18.7%) in group I and II respectively (P = 0.587). The corneal densitometry was 22.69 ± 8.28GSU preoperatively and 17.98 ± 3.13GSU at 12 months postoperatively (P = 0.010) in group I. The corneal densitometry was 21.86 ± 6.22GSU preoperatively and 21.23 ± 4.29GSU at 12 months postoperatively (P = 0.815) in group II. High corneal maximal densitometry was associated with the thin central corneal thickness (P = 0.027), the presence of haze (P = 0.028), post-keratoplasty (P = 0.004), steep keratometry (P = 0.035).

CONCLUSION:

The incidence of corneal haze was comparable in virgin and post corneal transplant eyes. The Pentacam Scheimflug densitometry can be helpful in the diagnosis of corneal haze; however, the cutoff values need to be studied further in larger studies.

A new method for detecting the outer corneal contour in images from an ultra-fast Scheimpflug camera

Background

The Corvis^® ST tonometer is an innovative device which, by combining a classic non-contact tonometer with an ultra-fast Scheimpflug camera, provides a number of parameters allowing for the assessment of corneal biomechanics. The acquired biomechanical parameters improve medical diagnosis of selected eye diseases. One of the key elements in biomechanical measurements is the correct corneal contour detection, which is the basis for further calculations. The presented study deals with the problem of outer corneal edge detection based on a series of images from the afore-mentioned device. Corneal contour detection is the first and extremely important stage in the acquisition and analysis of corneal dynamic parameters.

Result

A total of 15,400 images from the Corvis^® ST tonometer acquired from 110 patients undergoing routine ophthalmologic examinations were analysed. A method of outer corneal edge detection on the basis of a series of images from the Corvis^® ST was proposed. The method was compared with known and commonly used edge detectors: Sobel, Roberts, and Canny operators, as well as others, known from the literature. The analysis was carried out in MATLAB^® version 9.0.0.341360 (R2016a) with the Image Processing Toolbox (version 9.4) and the Neural Network Toolbox (version 9.0). The method presented in this paper provided the smallest values of the mean error (0.16%), stability (standard deviation 0.19%) and resistance to noise, characteristic for Corvis^® ST tonometry tests, compared to the methods known from the literature. The errors were 5.78 ± 9.19%, 3.43 ± 6.21%, and 1.26 ± 3.11% for the Roberts, Sobel, and Canny methods, respectively.

Conclusions

The proposed new method for detecting the outer corneal contour increases the accuracy of intraocular pressure measurements. It can be used to analyse dynamic parameters of the cornea.

Preoperative Risk Assessment for Progression to Descemet Membrane Endothelial Keratoplasty Following Cataract Surgery in Fuchs Endothelial Corneal Dystrophy

PURPOSE

To identify preoperative corneal tomographic features that predict progression to endothelial keratoplasty (EK) following cataract surgery in Fuchs endothelial corneal dystrophy (FECD) and establish a regression model to identify high-risk patients.

DESIGN

Prospective, observational cohort study.

METHODS

Setting: Hospital Universitario Ramón y Cajal, Madrid, Spain.

STUDY POPULATION

Sixty-eight patients (84 eyes) with FECD who underwent phacoemulsification.

INTERVENTION

We assessed preoperative best-corrected visual acuity; ultrasound central corneal thickness; pachymetric, anterior chamber depth, and corneal backscatter variables using Scheimpflug imaging; and endothelial cell density.

MAIN OUTCOME MEASURES

Progression to EK.

RESULTS

A total of 33 eyes (39.3%) needed EK after phacoemulsification to rehabilitate vision. On multivariate analysis, anterior layer (AL) corneal backscatter between 0 and 2 mm from the apex and relative increase in central corneal thickness from the "relative pachymetry display" by the Pentacam were significant predictors of the risk of progression to EK. Using these 2 variables, a risk score (RISC score) was derived from the regression model (area under the curve = 0.973; best cutoff point with a specificity of 95% representing a sensitivity of 96%). Excluding corneal backscatter data from the multivariate regression model, corneal thickness at the pupil center by the Pentacam and relative increase in central corneal thickness were significant predictors and provided a modified risk score (RIPT score) with similar performance.

CONCLUSION

Both scores demonstrated accuracy in predicting progression to EK using easily accessible preoperative data. This approach, which can be readily implemented by surgeons, allows for individualized risk assessment.

Diurnal Variation in Corneal Edema in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The extent of diurnal variation in corneal edema in Fuchs dystrophy is unknown. We measured corneal thickness and posterior profile over the course of the day using Scheimpflug imaging.

DESIGN

Prospective cohort study.

METHODS

Participants with clinically advanced Fuchs dystrophy eyes undergoing endothelial keratoplasty and participants with healthy corneas were assessed around noon the day before surgery and late afternoon, in presumed steady state. After controlled overnight patching to standardize eyelid closure, participants were assessed immediately upon eye opening in hospital the morning of surgery.

RESULTS

Directly upon awakening, patients had mean corneal thickness of 663 μm (interquartile range [IQR], 625-707) in Fuchs dystrophy (n = 44) and controls (n = 11) had thickness of 557 μm (IQR, 527-601). In control corneas, there were no systematic changes with time. In Fuchs dystrophy eyes, corneal thickness decreased after awakening. Ninety-five percent of patients can be expected to have a decrease in corneal thickness over the first 4 hours after awakening between 31 μm and 58 μm (95% prediction interval). Posterior Q decreased on average by 0.15 (95% confidence interval [CI], 0.07-0.23) and posterior radius of curvature decreased by 0.20 mm (95% CI, 0.14-0.27) over the first 4 hours, indicating that edema resolution steepened the central posterior cornea. Beyond 4 hours after awakening, corneas no longer changed considerably in Fuchs dystrophy.

CONCLUSION

Impaired hydration control in clinically advanced Fuchs dystrophy makes measurements of key corneal parameters unreliable directly after eye opening. Beyond the first hours after eye opening, corneal thickness measurements are unlikely to vary more in Fuchs dystrophy eyes than in normal eyes.

Predicting the Prognosis of Fuchs Endothelial Corneal Dystrophy by Using Scheimpflug Tomography

PURPOSE

To determine if Scheimpflug tomography pachymetry map and posterior elevation map patterns, central corneal thickness (CCT), and corneal backscatter can predict the prognosis of Fuchs endothelial corneal dystrophy (FECD).

DESIGN

Cross-sectional study with follow-up of outcomes.

PARTICIPANTS

Ninety-six eyes (56 subjects) with a range of severity of FECD.

METHODS

Corneas were graded by cornea specialists according to the area and confluence of guttae and the presence of clinically definite edema. Masked and randomized Scheimpflug imaging pachymetry map and posterior elevation map patterns were assessed by 1 observer for loss of regular isopachs, displacement of the thinnest point of the cornea, and the presence of posterior surface depression. The prognosis of eyes over a 5-year (median) follow-up period was determined based on FECD progression (new onset of clinically definite edema or ≥5% increase in CCT) or intervention by endothelial keratoplasty. Cumulative probabilities of progression and intervention were estimated from survival analyses, with risk factors determined by using Cox proportional hazards models.

MAIN OUTCOME MEASURES

Pachymetry map and posterior elevation map patterns, corneal backscatter, and CCT (ultrasonic pachymetry).

RESULTS

In univariate analyses, loss of regular isopachs (hazard ratio [HR], 18.00) displacement of the thinnest point (HR, 11.53), focal posterior surface depression (HR, 10.21), and anterior corneal backscatter (HR, 1.22, per 1-grayscale unit increment), were risk factors for progression or intervention (P < 0.001), whereas CCT (HR, 1.30, per 25-μm increment) was not (P = 0.15). In multivariate analyses, loss of regular isopachs (HR, 11.57; P < 0.001) and displacement of the thinnest point (HR, 5.61; P = 0.02) were independent and clinically important risk factors for progression and intervention. The 5-year cumulative risk of disease progression and intervention was 7%, 48%, and 89% when none, 1 or 2, and all 3 pachymetry map and posterior elevation map parameters were present, respectively (P <0.001). The 4-year cumulative risk of disease progression and intervention after uncomplicated cataract surgery was 0%, 50%, and 75% when none, 1 or 2, and all 3 pachymetry map and posterior elevation map parameters were present, respectively (P < 0.001).

CONCLUSIONS

Three Scheimpflug tomography pachymetry map and posterior elevation map patterns can predict FECD prognosis independent of CCT. The risk of FECD progression and intervention, including after uncomplicated cataract surgery, increases according to the number of parameters present.

Towards Clinical Trials in Fuchs Endothelial Corneal Dystrophy: Classification and Outcome Measures-The Bowman Club Lecture 2019

The surgical treatment of Fuchs endothelial corneal dystrophy (FECD) has advanced dramatically over the last two decades. Penetrating keratoplasty has been superseded by various iterations of endothelial keratoplasty, and currently, surgical removal of host Descemet membrane without keratoplasty is being investigated. These surgical advances have been accompanied by significant improvement of our understanding of the underlying disease mechanisms, not least the discovery that FECD in western populations is predominantly an intronic trinucleotide repeat expansion disorder in the transcription factor 4 gene that results in RNA toxicity and mis-splicing. Understanding the disease mechanisms augurs well for developing targeted molecular medical therapies, which will require careful clinical investigation through trials to prove their efficacy and safety. As the field advances towards clinical trials, investigators should carefully define the disease state being treated and consider the options for outcome measures relevant to the type of intervention. FECD, and the outcomes of interventions to treat the disease, can be measured in terms of corneal morphology, corneal function and clinical impact. Standardising the approach for defining FECD and careful thought about the outcomes of intervention that are reported will help make the results of future trials for FECD applicable in clinical practice.

Impact of classifying keratoconus location based on keratometry or pachymetry on progression parameters

BACKGROUND

This study sought to assess the impact of classifying keratoconus location based on thinnest pachymetry or maximum keratometry (Kmax) on progression parameters after corneal crosslinking (CXL).

METHODS

In this observational study, patients were followed up at one, three, six and 12 months after CXL. All patients underwent visual acuity, Scheimpflug tomography and slitlamp assessment at all follow-ups. Keratoconus was classified as central, paracentral and peripheral based on X and Y co-ordinates of either thinnest pachymetry (Group 1) or Kmax (Group 2). Progression parameters Kmax, ABCD grading, anterior, posterior and total wavefront (WF) aberrations were compared between the groups.

RESULTS

Fifty-two eyes (43 patients) were classified into Groups 1 and 2: there were 82.8 per cent, 13.4 per cent, 3.8 per cent and 42.3 per cent, 38.4 per cent, 19.2 per cent central, paracentral and peripheral cones respectively. Central cones: Group 1: 'C' decreased after three months, Kmax, 'A', anterior and total WF decreased after six months. Group 2: Kmax, anterior and total WF decreased after three months, 'A' decreased at 12 months, whereas 'C' increased from three months. Paracentral cones: Group 1: no significant changes. Group 2: Kmax and 'A' decreased after six months, 'C' increased after three months. Peripheral cones: Group 1: no significant changes. Group 2: 'C' increased only at one month.

CONCLUSION

Thinnest pachymetry and Kmax should not be used interchangeably when categorising keratoconus. Although keratoconus may have thin cornea centrally, the Kmax may not be central. For the majority of parameters considered for monitoring progression, changes were noticed earlier when the keratoconus was classified based on Kmax.

Quantitative evaluation of corneal epithelial edema after cataract surgery using corneal densitometry: a prospective study

PURPOSE

The optical density of the cornea can be evaluated quantitatively by "densitometry" using a rotating Scheimpflug camera. Densitometry allows evaluation of corneal opacity in the anterior segment of the eye by quantitative measurement of scattering light. In the present investigation, we evaluate quantitatively minimal subclinical corneal edema after cataract surgery using densitometry.

METHODS

Fifty four eyes of 34 patients who underwent cataract surgery were enrolled. Measurement of corneal density was performed using Pentacam® before and on days 1, 3 and 7 after surgery.

RESULTS

Densitometry scores increased from 18.12 ± 1.76 before cataract surgery to 21.03 ± 3.84 on day 1 (P < 0.001) and 19.90 ± 2.46 on day 3 (P = 0.018), but recovered to 19.44 ± 1.58 on day 7 (P = 0.131). Total corneal thickness was 549.1 ± 32.7 μm before surgery and increased to 582.7 ± 46.3 μm on day 1 (P = 0.001), but recovered to 566.4 ± 29.7 μm on day 3 (P = 0.097). Densitometry reading correlated positively with corneal thickness (correlation coefficient = 0.13, P = 0.003).

CONCLUSIONS

Densitometry is useful to detect corneal edema that is not detectable by slit-lamp examination.

Can we predict the refractive outcome after triple Descemet membrane endothelial keratoplasty?

Purpose:

To analyze and correlate corneal parameters with refractive shift after Descemet membrane endothelial keratoplasty combined with cataract surgery (triple Descemet membrane endothelial keratoplasty).

Methods:

This single-center retrospective observational case series included 152 eyes of 152 consecutive patients undergoing triple Descemet membrane endothelial keratoplasty in the first eye for Fuchs endothelial corneal dystrophy. Patients were examined preoperatively, as well as at 3, 6, and 12 months after surgery. The main outcome measures were: refractive shift (predicted refractive outcome based on intraocular lens calculation compared to actual postoperative refractive outcome), central corneal thickness, corneal volume, anterior and posterior corneal curvature, and corneal densitometry. These parameters were analyzed and correlated with the refractive shift after surgery.

Results:

After 3 months from surgery, a mean refractive shift of +1.12 ± 1.10 D was observed and remained stable until the last follow-up at 12 months (+1.24 ± 1.07 D). Correlation analysis showed a weak but significant positive correlation between refractive shift and preoperative posterior curvature (rho = 0.314; p = 0.002) or preoperative posterior densitometry (rho = 0.227; p = 0.008). No correlation was found between refractive shift and preoperative central corneal thickness, corneal volume, anterior curvature, or anterior/mid-cornea densitometry.

Conclusion:

Changes of the posterior cornea may have an influence on the refractive shift. Patients with flatter posterior corneal curvature or higher posterior corneal density seem to exhibit a higher hyperopic shift. The weak correlations indicate a poor predictive value of any preoperative parameter used in our study.

Corneal Optical Changes Associated with Induced Edema in Fuchs Endothelial Corneal Dystrophy

PURPOSE

Patients with Fuchs endothelial corneal dystrophy (FECD) often notice poor vision in the morning that improves as the day progresses. In this study, we determined changes in corneal optical properties associated with induced corneal edema.

METHODS

Twenty-three phakic eyes (23 participants) with FECD (grades 1-6, modified Krachmer scale) and 8 normal eyes (8 participants) were examined by Scheimpflug photography. Central corneal thickness, high-order aberrations from anterior and posterior corneal surfaces, and backscatter from the anterior, mid-, and posterior cornea were determined from the Scheimpflug images. A low-oxygen permeable contact lens was placed on the eye, and eyes were closed for 2 hours, after which the lens was removed and Scheimpflug photography was repeated for up to 5 hours to determine changes in backscatter and high-order aberrations.

RESULTS

Corneas swelled by 10% [95% confidence interval (CI), 9-10]. Backscatter from the anterior cornea increased by 416 scatter units (SU, 95% CI, 344-488; P < 0.001), independent of the presence and severity of FECD. Recovery of anterior backscatter was slower in advanced FECD (81 SU/h, 95% CI, 60-120) compared with normal (123 SU/h, 95% CI, 95-150; P = 0.019). Anterior and posterior corneal high-order aberrations, and mid and posterior backscatter, did not increase with induced swelling.

CONCLUSIONS

Inducing corneal edema increases anterior corneal backscatter but not high-order aberrations. Subjective poor vision in the morning in FECD is probably caused by scattered light rather than by high-order aberrations, suggesting that these patients experience more disability glare than decreased visual acuity.

A Three-Year Observation of Corneal Backscatter After Small Incision Lenticule Extraction (SMILE)

PURPOSE

To investigate changes in corneal backscatter after small incision lenticule extraction (SMILE).

METHODS

One eye was randomly selected from 34 patients who underwent SMILE procedures. Corneal backscatter was analyzed using Scheimpflug technology before surgery and at postoperative 1 day, 1 week, 1 month, 3, 6, and 12 months, and 3 years. Three different corneal depths (the anterior 120 µm, the center, and the posterior 60 µm) and three concentric radial zones (0 to 2, 2 to 6, and 6 to 10 mm) were analyzed. Another 40 eyes of 40 patients who underwent femtosecond laser-assisted LASIK (FS-LASIK) were examined before surgery and at postoperative 1 day and 3 years as the control group.

RESULTS

At postoperative day 1, a significant increase in corneal backscatter was detected in the SMILE group compared to preoperative values in the central 0 to 6 mm zone of the anterior layer and the 0 to 2 mm zone of the central layer (all P < .01). This increase was higher than the increase in the FS-LASIK group in the central 0 to 6 mm zone of the anterior and central layers (all P < .01). No significant differences in corneal backscatter were detected between preoperative values and the 1-week, and 1-, 3-, 6-, and 12-month follow-up visits in the SMILE group (all P > .05). Moreover, a significant decrease in corneal backscatter was detected in the three zones of all three layers in the two groups at 3 years postoperatively compared to preoperative values (all P < .001) and no significant difference was found between the two groups (all P < .05).

CONCLUSIONS

Corneal backscatter peaks and declines to the baseline in the early period after SMILE and corneal transparency achieves an improvement within 3 years postoperatively. [J Refract Surg. 2017;33(6):377-382.].

Two-Year Refractive Outcomes After Descemet Membrane Endothelial Keratoplasty

PURPOSE

To monitor refractive changes after Descemet membrane endothelial keratoplasty (DMEK) and to determine what may influence these changes and the time point of stabilization.

METHODS

From 67 pseudophakic DMEK eyes operated on for Fuchs endothelial dystrophy at a tertiary referral center, biomicroscopy, visual acuity, subjective refraction, and Scheimpflug-based corneal tomography data were obtained before and up to 2 years postoperatively. Visual acuity and changes in spherical equivalent (SE), mean anterior and posterior simulated keratometry (Km), and central pachymetry were analyzed.

RESULTS

At 3 months postoperatively, both hyperopic (28/67 eyes) and myopic (21/67 eyes) shifts were observed; 18/67 eyes showed no SE change. The mean change in SE at 3 months was +0.33 diopters (D) (95% confidence interval = [0.11, 0.54], P = 0.028), which stabilized thereafter (P > 0.466). Initial flattening of mean anterior Km by 0.66D (95% confidence interval = [-0.81, -0.51], P < 0.001) at 3 months was followed by a slow steepening, which became significant between 1 and 2 years postoperatively (P < 0.001). Posterior Km stabilized after 3 months (P > 0.252). Preoperative to 3 months postoperative absolute changes in anterior Km were positively related to preoperative backscattered light from the central anterior cornea (P = 0.035), and the presence of partial graft detachment postoperatively (P = 0.013).

CONCLUSIONS

After DMEK, SE and posterior corneal curvature were on average stable at 3 months after surgery, whereas the mean anterior corneal curvature showed an ongoing gradual change. Changes in anterior corneal curvature may be related to preoperative anterior corneal densitometry or postoperative partial graft detachment.

Corneal Hydration Control in Fuchs' Endothelial Corneal Dystrophy

Purpose

To assess corneal hydration control across a range of severity of Fuchs' endothelial corneal dystrophy (FECD) by measuring the percent recovery per hour (PRPH) of central corneal thickness after swelling the cornea and to determine its association with corneal morphologic parameters.

Methods

Twenty-three corneas of 23 phakic FECD patients and 8 corneas of 8 healthy control participants devoid of guttae were graded (modified Krachmer scale). Effective endothelial cell density (ECD_e) was determined from the area of guttae and local cell density in confocal microscopy images. Steady-state corneal thickness (CT_ss) and standardized central corneal backscatter were derived from Scheimpflug images. Corneal swelling was induced by wearing a low-oxygen transmissible contact lens for 2 hours in the morning. De-swelling was measured over 5 hours after lens removal or until corneal thickness returned to CT_ss. Percent recovery per hour was 100 × (1 – e^−k), where k was determined from CT(t) = (de^−kt) + CT_ss, and where d was the initial change from CT_ss.

Results

After contact lens wear, corneas swelled by 9% (95% CI 9–10). Percent recovery per hour was 49%/h (95% CI 41–57) in controls and 37%/h in advanced FECD (95% CI 29–43, P = 0.028). Low PRPH was associated with disease severity, low ECD_e, and increased anterior and posterior corneal backscatter. Anterior backscatter was associated with PRPH in a multivariable model (R² = 0.44).

Conclusions

Corneal hydration control is impaired in advanced FECD and is inversely related to anterior corneal backscatter. Anterior corneal backscatter might serve as an indicator of impaired endothelium in FECD.