The "Yogurt" Technique for Descemet Membrane Endothelial Keratoplasty Graft Preparation: A Novel Quick and Safe Method for Both Inexperienced and Senior Surgeons.

PURPOSE: To describe and evaluate the efficacy and safety of a novel technique to prepare Descemet membrane endothelial keratoplasty (DMEK) donor grafts using a newly designed partial-thickness hinge punch. METHODS: The novel punch has a circular guarded blade missing 1 clock hour, creating an uncut hinge on the donor cornea. In addition, 2 straight cuts are made by the punch perpendicular to the edge of trephination toward the trabecular meshwork in the hinge area. After the donor corneoscleral rim is positioned endothelial side up, a partial-thickness trephination is performed avoiding any rotational movements. Descemet membrane is lifted from Schwalbe line in the hinge area, and DMEK graft is peeled after desired marking without further preparation. RESULTS: Three surgeons of different experience levels on DMEK (senior/independent/fellow) initially applied the new technique in 18 research corneas, divided into equal groups. Two failures in graft preparation were noted, defined as radial tears extending ≥0.5 mm. The mean preparation time was 6.21 ± 1.45 minutes. No statistically significant differences were noted in success rate, duration, and endothelial cell loss (ECL) between surgeons (P > 0.05). ECL was evaluated as an average of 5 readings on randomly selected graft areas, not including graft periphery. Fifteen additional research corneas were stripped by 1 single user in an eye bank setting. No tissue loss was recorded, whereas ECL and mortality rate remained unaffected after preparation (P = 0.64 and P = 0.72, respectively). CONCLUSIONS: This new DMEK graft preparation technique, simulating the opening of a yogurt cup, seems to be a safe and an efficient method, providing shorter preparation time and low failure rates independent of surgeon's experience level.

The Influence of Speed During Stripping in Descemet Membrane Endothelial Keratoplasty Tissue Preparation.

PURPOSE: To evaluate whether the speed of stripping a Descemet membrane endothelial keratoplasty graft influences the graft scroll width. METHODS: Human corneas suitable for research were selected for the study. Pairs of corneas were randomly divided into 2 groups: 1 cornea was stripped with a slow speed (group 1) and the contralateral with a fast speed (group 2). Slow speed was defined as the total time greater than 150 seconds or speed <0.057 mm/s. Fast peeling was defined as less than 75 seconds or speed >0.11 mm/s. The grafts acquired were evaluated by microscopy for the graft scroll width and endothelial cell density change pre- and post-preparation. RESULTS: Twenty corneas of 10 donors were included in the analysis. The mean donor age was 68.6 ± 7.58 years. The mean total time of the tissue preparation in group 1 was 282.7 ± 28 seconds and in group 2 was 126 ± 50 seconds (P-value = 0.00000047). The mean speed of stripping in group 1 was 0.045 ± 0.006 mm/s and in group 2 was 0.266 ± 0.093 mm/s (P-value = 0.000027). The graft width in group 1 was 6.4 ± 0.92 mm and in group 2 was 2.87 ± 0.32 mm (P-value = 0.00000014). The mean endothelial cell loss in group 1 was 389 ± 149 cells/mm and in group 2 was 186 ± 63.44 cells/mm (P-value = 0.00134). CONCLUSION: We found a correlation between the speed of stripping, scroll width, and endothelial cell loss. Slow-peeled Descemet membrane endothelial keratoplasty grafts result in a wider scroll width but were associated with a greater reduction in endothelial cell density.

Intraobserver reproducibility and interobserver agreement of demarcation line depth measurements following corneal cross linking.

PURPOSE: The aim of this study was to evaluate the intraobserver reproducibility of demarcation line depth measurement in keratoconic patients after epithelium-off corneal collagen cross linking and assess the interobserver variability/agreement among examiners of various experience levels. METHODS: 56 eyes of 56 patients undergoing corneal collagen cross linking for progressive keratoconus were enrolled. After 4 weeks, all patients underwent an anterior segment optical coherence tomography (AS-OCT; CASIA SS-1000; Tomey, Nagoya, Japan) in the cross-linked eye by four masked examiners (two medical students (S1 and S2) and two corneal fellows (F1 and F2)) in order to identify and measure the demarcation line depth in experienced and non-experienced users. The intraclass correlation coefficient and the coefficient of variation were calculated. Agreement between raters was evaluated using Bland-Altman plots, intraclass correlation coefficient and weighted-kappa statistics comparing raters in pairs. RESULTS: The average demarcation line depth of all measurements was 254.34 ± 72.3 µm, varying from 84 to 459 µm. The intraclass correlation coefficient evaluating the reproducibility of measurements for F1 was 0.9379 (95% confidence interval (CI) =0.9035-0.9619), for the second (F2), it was 0.9837 (95% confidence interval = 0.9743-0.9901), while intraclass correlation coefficient between medical students was calculated 0.844. The overall intraclass correlation coefficient among all four observers was 0.8706 (95% confidence interval = 0.8061-0.9185). The coefficient of variation for repeated measurements was 5.981 µm (95% confidence interval = 3.966-7.471) and 3.312 µm (95% confidence interval = 2.468-3.981) for F1 and F2 raters, respectively. The percentage of demarcation line detection was 90.32%. CONCLUSION: The reproducibility of demarcation line measures although very good (intraclass correlation coefficient > 0.9), yielded a difference between the two experienced raters. Furthermore, the novice raters did not reach an excellent level of agreement with the expert ones showing greater variability in their recordings.

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction.

OBJECTIVE: Prediction errors are increased among patients presenting for cataract surgery post laser vision correction (LVC) as biometric relationships are altered. We investigated the prediction errors of five formulae among these patients. METHODS AND ANALYSIS: The intended refractive error was calculated as a sphero-cylinder and as a spherical equivalent for analysis. For determining the difference between the intended and postoperative refractive error, data were transformed into components of Long's formalism, before changing into sphero-cylinder notation. These differences in refractive errors were compared between the five formulae and to that of a control group using a Kruskal-Wallis test. An F-test was used to compare the variances of the difference distributions. RESULTS: 22 eyes post LVC and 19 control eyes were included for analysis. Comparing both groups, there were significant differences in the postoperative refractive error (p=0.038). The differences between the intended and postoperative refractive error were greater in post LVC eyes than control eyes (p=0.012), irrespective of the calculation method for the intended refractive error (p<0.01). The mean difference between the intended and postoperative refractive error was relatively small, but its variance was significantly greater among post LVC eyes than control eyes (p<0.01). Among post LVC eyes, there were no significant differences between the mean intended target refraction and between the intended and postoperative refractive error using five biometry formulae (p=0.76). CONCLUSION: Biometry calculations were less precise for patients who had LVC than patients without LVC. No particular biometry formula appears to be superior among patients post LVC.

Assessment of the Association Between In Vivo Corneal Biomechanical Changes After Corneal Cross-linking and Depth of Demarcation Line.

PURPOSE: To test for an association between stiffening following corneal cross-linking (CXL) and demarcation line depth. METHODS: Sixty-six eyes of 66 patients treated with CXL for progressive keratoconus were included. Dynamic corneal response parameters (DCRs) were measured with the Corvis ST (Oculus Optikgeräte GmbH; Wetzlar, Germany) on the day of CXL and after 1 month. Demarcation line was measured 4 weeks after CXL. A multivariate general linear model was used to test for an association between the change in DCRs and the ratio between demarcation line depth and the postoperative pachymetry. RESULTS: The authors found no significant associations between the change in inverse concave integrated radius (1/R) and the demarcation line ratio (P = .46), age (P = .33), sex (P = .11), preoperative maximum keratometry (P = .10), and laterality (P = .82). Similarly, there was no significant correlation between the change in 1/R and the demarcation line ratio (R2 = .002 and P = .75). However, there was a significant association between the preoperative values of 1/R and the respective change in 1/R (P < .0001). The change in 1/R was inversely proportional to the patient's preoperative 1/R; stiffer corneas (lower values of 1/R) were less affected than less stiff corneas (R2 = .23, P < .0001). CONCLUSIONS: CXL is associated with changes in DCRs, suggesting a change in corneal biomechanics following CXL. These changes do not appear to be associated with the demarcation line depth. [J Refract Surg. 2019;35(3):202-206.].

Progression of Keratoconus in Patients While Awaiting Corneal Cross-linking: A Prospective Clinical Study.

PURPOSE: To assess topographical changes in patients with keratoconus while awaiting corneal cross-linking (CXL) treatment. METHODS: In this prospective, double-center, observational clinical study, patients with keratoconus were enrolled. Progression was defined as a change in the curvature within the cone area of at least 1.00 diopter (D) on tangential map and a thinning of 20 µm at the thinnest point after measurements taken at least 3 months apart. Morphological parameters were assessed at baseline (day of listing for CXL) and on the day of CXL treatment, including slit-lamp biomicroscopy, keratometry (maximum, minimum, and mean), and thinnest corneal thickness using corneal tomography (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany). RESULTS: One hundred four eyes of 104 patients were included. The waiting time was 84.8 ± 62.9 days. Twenty-five percent of patients showed evidence of progression while waiting for treatment. Patients who progressed while waiting for treatment were younger (22.2 ± 6.79 years) compared to those who did not show evidence of progression (25.4 ± 5.62 years) (P = .02). Stratification by age groups showed a significant worsening of maximum keratometry of 1.18 ± 1.37 D in patients younger than 18 years compared to those 18 to 26 years of age and those older than 26 years (P = .002 and .042, respectively). The multivariate model confirmed that the progression steepening of the maximum keratometry while waiting for treatment was associated with age (P = .028). CONCLUSIONS: The results suggest that stratification of waiting time according to the patient's age is required to reduce the risk of further progression of keratoconus. [J Refract Surg. 2018;34(3):177-180.].

In Vivo Early Corneal Biomechanical Changes After Corneal Cross-linking in Patients With Progressive Keratoconus.

PURPOSE: To report early corneal biomechanical changes after corneal cross-linking (CXL) in patients with keratoconus. METHODS: Thirty-four eyes of 34 patients undergoing CXL for progressive keratoconus were included in this prospective clinical study. Dynamic corneal response (DCR) parameters obtained with the Corvis ST (OCULUS Optikgeräte GmbH; Wetzlar, Germany) were assessed at baseline (day of CXL) and after 1 month of follow-up; conversely, corneal tomography with the Pentacam (OCULUS Optikgeräte GmbH) was assessed at baseline and at 1, 3, and 6 months after CXL. RESULTS: At the last follow-up visit (123.7 ± 69.6 days), all morphological parameters including steepest point (Kmax) and thinnest corneal thickness (ThCT) indicated stabilization of keratoconus (P > .05). Comparative analyses showed a rise of corneal stiffness demonstrated by a significant increase of Stiffness Parameter A1 (SP-A1) and Highest Concavity (SP-HC) and a significant decrease of Inverse Concave Radius (1/R) and Deformation Amplitude Ratio (DA Ratio) (P < .05). There was a significant correlation between the preoperative keratoconus characteristics (Kmax, Belin/Ambrósio final D value [BAD-D], and ThCT) and the DCR parameters (P < .05). Kmax and BAD-D showed a significant positive correlation with DA Ratio, Deflection Amplitude (DefA), and 1/R and a significant negative correlation with SPA1 and SP-HC. ThCT showed a significant positive correlation with SP-A1 and SP-HC and a significant negative correlation with DA Ratio, DefA, and 1/R. CONCLUSIONS: This study suggests that the new DCR parameters of the Corvis ST are able to detect early changes in biomechanics following CXL and those that are measurable before corneal shape modifications take place. Based on these results, the authors suggest the use of these metrics to assess the early efficacy of cross-linking. [J Refract Surg. 2017;33(12):840-846.].

Presumed non-accidental injury with retinal haemorrhages--findings from a tertiary referral centre in the United Kingdom.

AIM: To describe the clinical and demographic features of patients with retinal haemorrhages from presumed non-accidental injury (NAI) at a tertiary referral centre in Leeds over a 2-year period. METHODS: All patients with retinal haemorrhages from presumed NAI between 1 January 2007 and 31 December 2008 were retrospectively identified from the hospital RetCam® (Clarity Medical System, Pleasanton, CA, USA) database. Case-notes, fundus photographs and radiological studies were retrieved for all patients and examined. RESULTS: Over the study period, 14 infants had retinal haemorrhages secondary to presumed NAI. All were male with a mean age of 18 ± 15 weeks (range 2-47) and came from areas with a mean Index of Multiple Deprivation (IMD 2007) rank of 34 ± 27% (range 0.97-68). Seizure/collapse was the reason for presentation in 71% (10/14). Retinal haemorrhages were bilateral in 64% (9/14) and unilateral in 36% (5/14). They were single-layered in 71% (10/14) and multi-layered in 29% (4/14). Subdural haemorrhages were found in 93% (13/14) and were symmetrical in 77% (10/13). Skeletal survey was positive in 28% (4/14). CONCLUSIONS: In the context of presumed NAI, there is a strong association between presence of retinal haemorrhages and the likelihood of underlying subdural haemorrhage. In this region, male infants under 12 months, from deprived areas, appear to constitute a vulnerable group.

Drusen and the misleading optic disc.

Optic disc drusen are acellular calcified deposits occurring in small optic discs. They have a prevalence of up to approximately 2% and are bilateral in 75% of cases. Their size and fundosc pic visibility increase with age, and they are commonly responsible for the misdiagnosis of papilloedema by the unwary. Although largely asymptomatic, they can be associated with vascular problems affecting the optic nerve. Ocular ultrasonography is the most sensitive method for their detection. This article highlights their commonly encountered clinical presentations and the practical aspects of diagnosis and management.