Central Corneal Research Articles

In vivo measurement of regional corneal tangent modulus

Currently available clinical devices are unable to measure corneal biomechanics other than at the central region. Corneal stiffness (S), thickness, and radius of curvature was measured at the central cornea (primary fixation) and 3 mm from the temporal limbus (primary and nasal fixations). The corneal tangent modulus (E) of 25 healthy subjects was calculated from these data. After confirming normality, repeated measures analysis of variance (RMANOVA) revealed significant difference in S (F(2, 48) = 21.36, p < 0.001) at different corneal regions and direction of fixations. E also varied significantly at different corneal regions and direction of fixations (RMANOVA: F(2, 48) = 23.06, p < 0.001). A higher S and a lower E were observed at the temporal region compared with the corneal centre. Nasal fixation further increased S and E values compared with primary fixation. Due to the specific arrangement of corneal collagen fibrils, heterogeneity of corneal biomechanical properties is expected. In future clinical practice, localized corneal biomechanical alternation and measurement might assist corneal disease detection and post-surgery management. In addition, practitioners should be aware of the fixation effect on corneal biomechanical measurement.

Intrasession repeatability of ocular anatomical measurements obtained with a multidiagnostic device in healthy eyes

BackgroundTo evaluate the intrasession repeatability of anterior chamber depth (ACD), central (CCT) and peripheral corneal thickness (PCT), white-to-white diameter (WTW), and irido-corneal angle (IA) measurements obtained with a multidiagnostic device in healthy eyes.MethodsA total of 107 eyes of 107 patients ranging in age from 23 to 65 years were examined with the VX120 system (Visionix-Luneau Technologies). Three consecutive measurements were obtained with this device to assess the intrasession repeatability of ACD, CCT, PCT at different nasal and temporal locations, WTW, and nasal and temporal IA. Data analysis included the calculation of within-subject standard deviation (Sw), intrasubject precision (1.96xSw), coefficient of variation (CV) and intraclass correlation coefficient (ICC).ResultsThe Sw and CV for ACD was 0.03 mm and 1.16%, respectively, with an ICC of 0.992. The Sw values for central and peripheral pachymetric measurements were below 9 μm, with CV of less than 1.6% and ICC of 0.976 or higher. For IA measurements, Sw values of 0.84 or lower were found, with a CV between 1 and 2%, and an ICC of more than 0.970. The Sw for WTW was 0.24 mm and the CV was 1.95%. No statistically significant correlations were found between any anatomical parameter evaluated and their Sw and CV values associated (−0.220 ≤ r ≤ 0.204, p ≥ 0.125).ConclusionsThe VX120 system is able to provide repeatable measurements of anatomical parameters in healthy eyes. Inter-observer repeatability should be evaluated in future studies.

Sub-classification of myopic glaucomatous eyes according to optic disc and peripapillary features.

PurposeTo investigate the sub-classification of myopic glaucomatous eyes by optic disc and peripapillary features.MethodsOptic disc tilt and torsion were determined from retinal nerve fiber layer photographs. Based on the location of the Bruch’s membrane (BM) opening within the β-zone of the peripapillary atrophy (PPA) area, the widths of β-zone PPA (PPA1W), PPA+BM (PPA2W), and PPA-BM (PPA3W) were measured with enhanced depth imaging spectral-domain optical coherence tomography. Cluster analysis that employed partitioning around medoids was performed with these parameters, the presence of inward rotation of BM ending axial length (AXL), and central corneal thickness.ResultsA total of 115 eyes (AXL≥24 mm) were included. Two clusters produced maximum overall silhouette widths (average = 0.43). Visual field (VF) mean deviation was not different between cluster 1 (52 eyes; -4.02±3.01 dB) and cluster 2 (63 eyes; -5.21±5.62 dB; p = 0.174). In cluster 1 compared to cluster 2, optic disc tilt was significantly greater, PPA1W and PPA3W were longer, and AXL was longer (all p<0.001). The presence of an inward rotation of BM ending was more frequent in cluster 2 (p = 0.043). Forty-one eyes (78.8%) in cluster 1 had superior VF defects while 10 eyes (19.2%) had inferior defects, and only one eye (2%) had defects in both hemifields. Eyes in cluster 2 were more evenly distributed: 55.6% had superior defects, 34.9% had inferior defects, and 9.5% had defects in both hemifields (p = 0.023).ConclusionsMyopic glaucomatous eyes characterized by optic disc and peripapillary configurations can be classified as two distinct types, and the most distinct difference between the two was degree of optic disc tilt and width of PPA. The location of VF defects were also significantly different between two clusters.

Technology of the Local Cross-linking (Part 1): Keratotensotopography and Vacuum-compression Topographic Test—New Diagnostic Possibilities for Studying the Local Biomechanical Properties of Cornea

ABSTRACT Aim The aim of this study is the development and evaluation of clinical significance methodology for determining mech­anical stress (MS) and elasticity of the cornea comparable to its topographic settings. Materials and methods Combining the data of optical pachymeter, keratotopography, and pneumotonometry through our special software allows us to get Lokolink MS distribution in the cornea in the form of maps, which we propose to call keratotensotopogram (KTT). Results Normal KTT has the form of concentric, uniform, and symmetrical zones. In keratoconus (KC), the corneal center is more tense than peripheral part of cornea. The focus zone of KC may coincide with the region of maximum MS or may be out of this area. In the process of vacuum-compression test, the reaction of profile of the cornea was markedly different in patients with healthy corneas and in patients with KC. In all cases of healthy cornea, the curvature increased in the center. In KC, the cornea became more flat in the center under high intraocular pressure (in 100% of cases). Conclusion The KTT ineyes with the cornea without pathology differs from KTT in the different cases of KC. The KTT can be used for the diagnosis and prediction of cornea's state to perform the plan of UV irradiation areas for corneal collagen cross-linking. How to cite this article Anisimov SI, Anisimova SY, Mistryukov AS, Anisimova NS. Technology of the Local Cross-linking (Part 1): Keratotensotopography and Vacuum-compression Topographic Test—New Diagnostic Possibilities for Studying the Local Biomechanical Properties of Cornea. Int J Kerat Ect Cor Dis 2017;6(1):14-16.

Usability and reproducibility of tear meniscus values generated via swept-source optical coherence tomography and the slit lamp with a graticule method

PurposeTo investigate the usability and the reproducibility of the tear meniscus values via swept-source optical coherence tomography (SS-OCT) and the conventional slit lamp microscope method with a graticule.MethodsThe right eye was examined in 90 healthy adult subjects who were grouped according to age (group 1: 20–39 years; group 2: 40–59 years; group 3: ≥60 years). The tear meniscus height (TMH) and tear meniscus area were measured using SS-OCT and TMH by the slit lamp microscope method. The reproducibility of each method was calculated using intraclass correlation coefficients (ICCs) in additionally enrolled 30 healthy young subjects. We also evaluated TMH at 3 mm from the corneal center in both temporal and nasal directions using SS-OCT.ResultsThe mean of the TMH values measured by SS-OCT was significantly higher than those measured by the slit lamp method (328 vs. 212 μm, P < 0.001, respectively). High reproducibility was observed for each method (ICC > 0.75 for both). No statistically significant differences were found in TMH among the age groups using both SS-OCT and slit lamp methods (P = 0.985, 0.380, respectively). TMH values at both sides of the corneal center were significantly smaller than those at the corneal center (P < 0.0001).ConclusionsTMH values obtained by the slit lamp method were lower than those obtained by SS-OCT. However, both methods yielded highly reproducible TMH measurements, suggesting that they are clinically useful. Tear meniscus values did not vary by age but by measurement points in our cohort.

Effect of Histone Deacetylase Inhibitor, Butyroyloxymethyl-Diethyl Phosphate (AN-7), on Corneal Neovascularization in a Mouse Model.

To examine whether butyroyloxymethyl-diethyl phosphate (AN-7), a histone deacetylase inhibitor, inhibits chemically induced corneal neovascularization (NV) in mice. Corneal NV was induced in the right eye of male C57BL mice by application of a mixture of 75% silver nitrate and 25% potassium nitrate to the corneal center. Immediately thereafter, the mice were randomized into 2 groups, receiving an intraperitoneal injection of AN-7 or saline, which served as control. Corneal NV was evaluated at constant time intervals from the corneal injury by corneal photographs and the area of corneal NV was measured. Centricity and density of the corneal vascularization were graded. Corneal flat mounts blood vessels staining and histological studies were performed on day 10. Unpaired t-test was used for group comparisons. The corneal neovascular area was statistically significantly reduced by AN-7 treatment on days 10 and 14 postinjury and compared with the untreated group. The centricity and density of the corneal NV between treated and untreated groups showed no significant difference at any time point. Systemic treatment with AN-7 had a significant inhibitory effect on chemical burn-induced corneal NV in mice. These results suggest that AN-7 should be further evaluated for its therapeutic potential for the treatment of corneal NV.

Surface coverage with single vs. multiple gaze surface topography to fit scleral lenses.

To determine surface coverage of measurements using the sMap3D® corneo-scleral topographer in patients presenting for scleral lens fitting. Twenty-five eyes of 23 scleral lens patients were examined. Up-gaze, straight-gaze, and down-gaze positions of each eye were "stitched" into a single map. The percentage surface coverage between 10mm and 20mm diameter circles from corneal center was compared between the straight-gaze and stitched images. Scleral toricity magnitude was calculated at 100% coverage and at the same diameter after 50% of the data was removed. At a 10mm diameter from corneal center, the straight-gaze and stitched images both had 100% coverage. At the 14, 15, 16, 18 and 20mm diameters, the straight-gaze image only covered 68%, 53%, 39%, 18%, and 6% of the ocular surface diameters while the stitched image covered 98%, 96%, 93%, 75%, and 32% respectively. In the case showing the most scleral coverage at 16mm (straight-gaze), there was only 75% coverage (straight-gaze) compared to 100% (stitched image); the case with the least coverage had 7% (straight gaze) and 92% (stitched image). The 95% limits of agreement between the 50% and 100% coverage scleral toricity was between -1.4D (50% coverage value larger) and 1.2D (100% coverage larger), a 2.6D spread. The absolute difference between 50% to 100% coverage scleral toricity was ≥0.50D in 28% and ≥1.0D in 16% of cases. It appears that a single straight-gaze image would introduce significant measurement inaccuracy in fitting scleral lenses using the sMap3D while a 3-gaze stitched image would not.

Association between corneal volume change and corneal biomechanical property before and after small incision lenticule extraction in myopia

Background The relationship between corneal central thickness (CCT) and corneal biomechanical property does not reflect the effective amount of ablated tissue because CCT measures only the change in a single point.Corneal volume (CV) is a representative parameter of corneal morphology, and it can fully reflect corneal thickness and tissue distribution. Objective This study was to investigate the correlation between volumetric corneal changes and corneal biomechanical properties after small incision lenticule extraction (SMILE). Methods A prospective series cases-observational study was carried out.This study protocol was approved by Ethic Committee of Tianjin Eye Hospital, and written informed consent was obtained from each patient prior to entering the cohort.Sixty-seven right eyes of 67 myopia or myopic astigmatism patients who received SMILE in Tianjin Eye Hospital from June 2014 to July 2015 were included in this study.Before and 3 months after surgery, the CV at 3, 3-5, 5-7 and 7-10 mm (CV3, CV3-5, CV5-7, CV7-10) was measured by Pentacam anterior segment analysis system, and corneal hysteresis (CH) and corneal resistance factor (CRF) were obtained by ocular response analyzer (ORA). The changes of CV (ΔCV), CH (ΔCH) and CRF (ΔCRF) were calculated, and the correlations between ΔCV and ΔCH or ΔCRF were analyzed. Results CV3, CV3-5 and CV5-7 values after SMILE were significantly lower than those before SMILE (t=36.24, 20.38, 16.17, all at P< 0.001). The CH values before and after SMILE were (10.06±1.11)mmHg and (8.10±1.05)mmHg (1 mmHg=0.133 kPa), and the CRF values before and after SMILE were (10.40±1.38)mmHg and (6.91±1.19)mmHg, respectively, showing significant reduces after SMILE than before SMILE (t=16.71, 27.41, both at P<0.001). Positive correlations were seen between the CV values at different corneal areas and CH value or CRF value.Moderate positive correlations were found between CV3 and CH or CRF (r=0.571, 0.569; both at P<0.001) before surgery, and 3 months after surgery, a weak positive correlation was seen between ΔCV3 and ΔCH (r=0.394, P<0.001) or a moderate positive correlation between ΔCV3 and ΔCRF (r=0.501, P<0.001). Conclusions The CV value is gradually increased from the central cornea to periphery cornea.The CV change is associated with CH and CRF changes after SMILE, and CV3 probably is a useful parameter for the evaluation of corneal biomechanics after refractive surgery. Key words: Biometry; Cornea; Volume; Corneal biomechanics; Corneal hysteresis; Corneal resistance factor; Small incision lenticule extraction

Effect of Isolation Technique and Location on the Phenotype of Human Corneal Stroma-Derived Cells.

Purpose To determine the effect of the isolation technique and location upon the phenotype of human corneal stroma-derived cells (CSCs). Methods CSCs were isolated from the corneal stroma center and periphery using the explant or enzymatic digestion technique. The native tissue was stained for functional markers, while cultured cells were analysed by FACS. PCR was used to determine gene expression in the cultured versus native cells. Results The native stroma was positive for α-actinin, ALDH1A1, CD31, CD34, Collagen I, and Vimentin. Cultured cells expressed CD73, CD90, CD105, CD51, Nestin, CD49a, CD49d, ABCG2, and CD47. PCR demonstrated a significant upregulation of ALDH1A1, AQP1, ITGB4, KLF4, CD31, CD34, and CXCR4 in the native tissue, while the expression of ABCG2, ITGAV, Nestin, CD73, CD90, CD105, and Vimentin were significantly higher in the cultured cells. GPC did not change. Conclusion The study finds no significant difference between the phenotype of CSCs generated by the explant or enzymatic digestion technique from the center or periphery of the stroma. Isolation of the cells can be performed without regard to the location and isolation technique used for research. Cultivated CSCs undergo a complete surface marker and genotype profile change compared to the state in situ.

Temporal and Spatial Flap Variability in Laser In-Situ Keratomileusis by Optical Coherence Tomography.

Purpose:To study changes in flap thickness made with two different microkeratome heads across different corneal locations using anterior segment optical coherence tomography (OCT).Methods:In this prospective, non-randomized, consecutive case series, subjects who had their laser in-situ keratomileusis (LASIK) flaps made using 90 μm (MSU90) or 130 μm (MSU130) disposable M2 microkeratome heads were examined using OCT. The measurements were performed at three locations (central and 2.5 mm to either side) at 1 day, 1 week, and 1 month postoperatively.Results:The central flap thickness was 123 ± 15, 130 ± 14, and 127 ± 13 μm, respectively, at 1 day, 1 week, and 1 month postoperatively in the MSU90 group (41 eyes) and 142 ± 20, 147 ± 19, and 143 ± 15 μm, respectively, in the MSU130 group (47 eyes). At 1 month, peripheral flap thickness was 161 ± 17 and 159 ± 13 μm, respectively, at 2.5 mm to the right and left of corneal center in the MSU90 group. The corresponding figures were 170 ± 14 and 167 ± 13 μm, respectively, in the MSU130 group. There was a statistically significant difference between the two groups at all locations (P < 0.001). No statistically significant change in flap thickness was detected in either group at any assessment time. There was a partial positive correlation (after controlling for preoperative manifest refractive spherical equivalent) between central flap thickness and preoperative ultrasound central pachymetry (r = 0.739, P = 0.036) in the MSU90 group but not in the MSU130 group.Conclusion:Using OCT, changes in flap thickness were minimal in the first month after LASIK. Flap thickness correlated strongly with central corneal thickness if a 90 μm head was used.

Zastosowanie wewnątrzgałkowych soczewek torycznych w trakcie operacji zaćmy u pacjentów z chorobami zniekształcającymi rogówkę

Cataract surgery in patients with distorted cornea is a challenge for the surgeon. Cornea with irregular astigmatism and dislocation of the corneal centre may result in a large refractive error after cataract surgery. It is important to assess the patient carefully, analyzing the corneal topography, and selecting a minimally invasive surgery that does not provoke secondary changes in the asymmetry of the cornea. The use of toric intraocular correction for patients suffering from significant distortion of the cornea and corneal astigmatism is a matter of difficulty stemming from weaker corneal hysteresis and instability of the corneal shape.

Two-Year Course of Corneal Densitometry After Descemet Membrane Endothelial Keratoplasty

To investigate the 2-year course of corneal densitometry following Descemet membrane endothelial keratoplasty (DMEK) for Fuchs endothelial dystrophy (FED). Retrospective, interventional case series. Densitometry values (corneal light backscatter in grayscale units) measured by Scheimpflug-based imaging and clinical records of 160 eyes of 160 patients undergoing DMEK for FED were reviewed. Outcome measures included densitometry data in 4 corneal layers (anterior layer [AL], central layer [CL], posterior layer [PL], and total layer [TL]) and 2 annuli (central annular zone 0-2mm and peripheral zone 2-10mm), central corneal thickness (CCT), best spectacle-corrected visual acuity (BSCVA), and endothelial cell density (ECD) prior to DMEK and at 1, 3, 6, 12, and 24months postoperatively. Corneal densitometry decreased in all 4 layers over 2 years after DMEK surgery. Regarding TL 0-2mm, the reduction of corneal light backscatter was statistically significant for all follow-up time points compared with preoperative values (P < .001) and compared in between follow-up periods (P ≤ .010). Corneal light backscatter reduction was significantly higher in the center (0-2mm) than in the periphery (2-10mm) for all layers at 12 and 24months (P ≤ .002). ECD and CCT did not correlate with corneal densitometry, whereas BSCVA correlated moderately for TL 0-2mm (P= .026; r= 0.449) and TL 2-10mm (P= .001; r= 0.585) at 12months. Corneal light backscatter showed a significant reduction after DMEK surgery in Fuchs endothelial dystrophy over a period of 2 years, more pronounced in the corneal center, apparently in association with visual acuity improvement.

Distribution and compensation mechanism of aberrations between anterior and posterior surface of the cornea in myopia and myopic astigmatism eyes

Objective: To study the compensation mechanism of aberrations between anterior and posterior corneal surface, and to investigate the correlations between corneal aberrations and K values, intraocular pressure and central corneal thickness. Methods: One hundred and sixty-one subjects (300 eyes) with myopia and myopic astigmatism were recruited randomly. Corneal aberrations (anterior, posterior and total) in three different optical zones (2 mm, 4 mm, and 6 mm) centered on the corneal vertex were assessed with a corneal topographer (Sirius). We also calculated compensation factors (CFs) as a measure of the relative efficiency of the aberration compensation mechanism. Astigmatism was divided into corneal astigmatism and non-corneal astigmatism. Mann-Whitney U test was utilized for the comparison of different aberrations and CFs between the two astigmatism groups. Spearman correlation was applied to analyze the correlations between corneal aberrations and K values, intraocular pressure and central corneal thickness. Results: As the order of the aberrations elevated from the second to the seventh, the RMS values decreased significantly. The larger the optical zone, the greater the values of aberrations and the lower the percentage of the compensation mechanism among all the Zernike terms. At the same time, as the order of the aberrations increased, the predominance of the compensation mechanism was increasingly obvious. Slight compensation of spherical aberration (Z40) was observed in the peripheral. In the center of the analyzing zones (2 mm), compensation mechanism represented in coma (Z3±1), and it disappeared in the peripheral. We detected slight compensation of the corneal astigmatism (Z2±2) in the surrounding zone, although the compensation factors were closed to zero in diverse optical zones. Superposition was found in trefoil (Z3±3) straightly. Nevertheless, a tendency towards compensation was discovered with the enlargement of the optical zones. And the secondary spherical aberration (Z60) behaved compensation continuously. However, similar compensation was discovered between the right eye and left eye in different analyzing optical zones. There were significant correlations between the flattest K values and Z2±2, Z3±3and Z40 in the anterior, posterior and total cornea. It was similar with the steepest K values. When the optical zone expanded to 6 mm, Z3±1 and Z40 significantly decreased with intraocular pressure (rcoma=-0.188, P<0.05. rspherical=-0.147, P<0.05). No correlation was found between various aberrations and central corneal thickness (P>0.05). Conclusions: Compensation dominated in the corneal center, while the percentage decreased gradually as the optical zone extended. Slight compensation in astigmatism and spherical aberration between the anterior and posterior cornea may be benificial to the scotopic visual quality. Corneal aberrations were significantly related to K values and intraocular pressure. (Chin J Ophthalmol, 2016, 52: 840-849).

Modulatory effects of 1,25-dihydroxyvitamin D3 on eye disorders: A critical review

ABSTRACTMany studies have shown that the presence of 1,25-dihydroxyvitamin D3 in the eye is able to modulate inflammatory responses. In fact, it has been demonstrated that topical administration of vitamin D3 inhibits Langerhans cells migration from the central cornea, corneal neovascularization, and production of cytokines (i.e., interleukin-1-6-8) in experimental animals.Moreover, both in vitro and in vivo studies have demonstrated that vitamin D is a potent inhibitor of retinal neovascularization. It has been shown that calcitriol, the biologically active form of vitamin D, inhibits angiogenesis both in cultured endothelial cells and in retinas from guinea pigs with retinoblastoma or oxygen-induced ischemic retinopathy. In addition, it seems that this compound is able to prevent the progression from early to neovascular age-related macular degeneration (AMD) and, at the same time, to down-regulate the characteristic inflammatory cascade at the retinal pigment epithelium–choroid interface due to its anti-inflammatory and immunomodulatory capabilities.Furthermore, 1,25-dihydroxyvitamin D3 and its analogue, 2-methylene-19-nor-1,25-dihydroxyvitamin D3, are able to modulate intraocular pressure (IOP) through gene expression. Several studies have suggested a role in glaucoma and diabetic retinopathy therapies for vitamin D3.In conclusion, this review summarizes our current knowledge on the potential use of vitamin D3 in the protection and treatment of ocular diseases in ophthalmology.

Anterior Corneal, Posterior Corneal, and Lenticular Contributions to Ocular Aberrations.

To determine the corneal surfaces and lens contributions to ocular aberrations. There were 61 healthy participants with ages ranging from 20 to 55 years and refractions -8.25 diopters (D) to +3.25 D. Anterior and posterior corneal topographies were obtained with an Oculus Pentacam, and ocular aberrations were obtained with an iTrace aberrometer. Raytracing through models of corneas provided total corneal and surface component aberrations for 5-mm-diameter pupils. Lenticular contributions were given as differences between ocular and corneal aberrations. Theoretical raytracing investigated influence of object distance on aberrations. Apart from defocus, the highest aberration coefficients were horizontal astigmatism, horizontal coma, and spherical aberration. Most correlations between lenticular and ocular parameters were positive and significant, with compensation of total corneal aberrations by lenticular aberrations for 5/12 coefficients. Anterior corneal aberrations were approximately three times higher than posterior corneal aberrations and usually had opposite signs. Corneal topographic centers were displaced from aberrometer pupil centers by 0.32 ± 0.19 mm nasally and 0.02 ± 0.16 mm inferiorly; disregarding corneal decentration relative to pupil center was significant for oblique astigmatism, horizontal coma, and horizontal trefoil. An object at infinity, rather than at the image in the anterior cornea, gave incorrect aberration estimates of the posterior cornea. Corneal and lenticular aberration magnitudes are similar, and aberrations of the anterior corneal surface are approximately three times those of the posterior surface. Corneal decentration relative to pupil center has significant effects on oblique astigmatism, horizontal coma, and horizontal trefoil. When estimating component aberrations, it is important to use correct object/image conjugates and heights at surfaces.

Histopathologic Features of Descemet Membrane Endothelial Keratoplasty Graft Remnants, Folds, and Detachments

To describe the histologic features of postmortem eyes after Descemet membrane endothelial keratoplasty (DMEK) and their potential clinical implications. Histopathologic study. Eleven postmortem DMEK corneas of 8 patients who underwent surgery for Fuchs endothelial dystrophy, with an average postoperative time of 4±1.9 years (range, 7 months-6.5 years). Eleven corneas transplanted with a DMEK graft were procured after death and processed for light microscopy evaluation. Histologic findings at the donor-host interface and at the host edge. Of the 11 corneas available for analysis, 9 showed normal anatomic features in the corneal center; that is, the donor-host interface resembled that of a virgin eye. One eye also had an anatomically normal periphery, but the remaining 10 eyes showed specific abnormalities in the periphery. Nine demonstrated overlapping of the DMEK graft onto the host edge of the descemetorhexis (and in 6 of these, the overlapping tissue showed a contracted inward fold at its peripheral edge with scar tissue); 1 eye showed a dense, acellular scar overlying a portion of the DMEK graft that clinically had shown a detachment followed by spontaneous adherence; 3 eyes showed subtle graft folds with scar tissue anteriorly; in 2 eyes (of the same patient), the anterior banded layer of the host Descemet membrane (DM) was still in situ across the cornea (both of these eyes had required rebubbling); and 2 eyes showed host DM remnants within the corneolimbal tunnel incision that may have interfered with incisional wound healing. Incomplete host DM removal may relate to postoperative DMEK graft detachment and wound instability. Graft detachments may reattach with interface scarring. Rebubbling procedures may be performed within 4 to 6 weeks, before portions of the detached graft scar. Subtle DMEK graft folds may explain subjective reports of monocular diplopia.

In Vivo Imaging of Corneal Endothelial Dystrophy in Boston Terriers: A Spontaneous, Canine Model for Fuchs' Endothelial Corneal Dystrophy.

PurposeBoston Terriers (BTs) have a greater prevalence of corneal endothelial dystrophy (CED), in comparison to other canine breeds. Similar to Fuchs' endothelial corneal dystrophy (FECD), this condition is characterized by endothelial cell degeneration with secondary corneal edema. This study assessed corneal morphology using in vivo confocal microscopy (IVCM) and Fourier-domain optical coherence tomography (FD-OCT) in BTs with and without CED.MethodsThe corneas of 16 BTs with CED and 15 unaffected, age-matched BTs underwent clinical evaluation and were imaged using IVCM and FD-OCT. A two-sample t-test or Mann-Whitney rank sum test were used to statistically compare parameters between groups. Data are presented as mean ± SD or median (range).ResultsMean age did not significantly differ between affected and unaffected dogs at 10.0 ± 2.0 and 10.6 ± 2.4 years, respectively (P = 0.437). Females (69%) were overrepresented among the CED-affected dogs. In CED patients, IVCM demonstrated endothelial polymegathism and pleomorphism. Corneal endothelial density was significantly less (P < 0.001) in dogs with CED (1026 ± 260 cells/mm2) versus age-matched controls (2297 ± 372 cells/mm2). Fourier-domain OCT demonstrated a significant increase (P < 0.01) in central corneal and endothelium-Descemet's complex thickness in dogs with CED versus age-matched controls at 1019 (485–1550) or 536 (464–650) μm and 32 (22–56) or 25 (15–34) μm, respectively.ConclusionsCorneal endothelial dystrophy in BTs is a bilateral, adult-onset condition that shares many similarities with FECD. Thus, CED could serve as a spontaneous disease model to study the pathogenesis of and develop novel treatments for FECD.

The potential role of neuropathic mechanisms in dry eye syndromes

Dry eye syndromes can involve both nociceptive and neuropathic symptoms. Nociceptive symptoms are the normal physiological responses to noxious stimuli. Neuropathic symptoms are caused by a lesion or disease of the somatosensory nervous system and can be the result of hypersensitisation of peripheral or central corneal and conjunctival somatosensory nerves. For example, inflammation could induce neuroplastic peripheral sensitisation of the ocular surface or lid wiper and exacerbate nociceptive symptoms. Neuropathic symptoms may explain the incommensurate relation between signs and symptoms in some dry eye syndromes although absence of signs of a dry eye syndrome may also be a consequence of inappropriate methods used when examining for them. Involvement of neuropathic mechanisms may also help explain dry eye symptoms which occur in association with reduced corneal sensitivity. This review includes a discussion of the potential for ocular symptoms involving neuropathic mechanisms to contribute to psychosocial problems such as depression, stress, anxiety and sleep disorders as well as for these types of psychosocial problems to contribute to neuropathic mechanisms and dry eye syndromes. Failure to consider the possibility that neuropathic mechanisms can contribute to dry eye syndromes may reduce accuracy of diagnosis and the suitability of treatment provided. Dry eye symptoms in the absence of commensurate evidence of tear dysfunction, and unsatisfactory response to tear dysfunction therapies should prompt consideration of neuropathic mechanisms being involved. Symptoms which persist after local anaesthetic instillation are more likely to be neuropathic in origin. Reducing inflammation may help limit any associated neuroplastic hypersensitivity.

Five year changes in central and peripheral corneal thickness: The Shahroud Eye Cohort Study.

To determine five year changes in corneal thickness from the apex to the 8mm periphery and related factors through a longitudinal population-based study of middle-aged Iranians. In the first phase, 4670 of the 5190 participants, and in the second phase, 4666 of the 4737 participants were examined with the Pentacam. In this report, analysis was done on right eye data of 2509 people who had no diabetes, pterygium, or history of eye surgery, and their image quality was displayed as "ok". Thickness changes in different parts of the cornea and their relation with age, gender, refractive error, and intraocular pressure (IOP) were assessed using repeated measures analysis of covariance. Corneal thickness reduced by 1.5±11.7μm in the apex, 2.6±11.7μm in the thinnest point, and 5.3±12.2, 7.7±14.3, and 11.4±18.6μm in peripheral rings of 2, 3, and 4mm radius, respectively (all p<0.001 with and without adjusting for baseline thickness). Of the studied thickness variables, only changes in the 4mm ring significantly related with age (p<0.001) and gender (p<0.001); there was less change in older age and in men. Thickness changes were not related to refractive error or IOP (all p>0.05). Corneal thickness decreased with age in this sample of 40-64year olds. There was significantly greater thinning in the periphery compared to the corneal center even after controlling for baseline thickness. Results of this longitudinal study can be helpful in understanding age-related changes in the cornea and the eye.

Preoperative intraocular pressure as a predictor of selective laser trabeculoplasty efficacy.

To identify predictors of intraocular pressure (IOP) reduction following selective laser trabeculoplasty (SLT) in patients with high- and low-pressure primary open-angle glaucoma, who are already taking maximally tolerated IOP-lowering medication and need further IOP reduction. In this prospective interventional case series, 157 eyes of 157 open-angle glaucoma patients who were assigned for SLT for further IOP reduction were included. Each patient had diurnal IOP measurements taken before and on average 6months following SLT. The mean of six IOP measurements was compared. The following parameters were analysed for their association with SLT success: age, gender, spherical equivalent, high-pressure or normal-pressure open-angle glaucoma, number and type of pressure-lowering medications, lens status, pre-SLT IOP, IOP at the time of diagnosis, duration of glaucoma, visual field stage and central corneal thickness. The only parameter that was predictive for absolute and relative mean diurnal IOP reduction after SLT was the preoperative mean diurnal IOP. One hundred per cent of the patients with a mean diurnal preoperative IOP of more than 18mmHg had an IOP reduction after SLT. With mean diurnal preoperative values of 14-18mmHg, 83.1% of the patients, and with values below 14mmHg only 64% of the patients, showed an IOP reduction. This difference was statistically significant (>18 compared to 14-18: p=0.002; >18 compared to <14: p=0.001; 14-18 compared to <14: p=0.030). The pressure-lowering effect of SLT can best be predicted by the individual IOP level before treatment. Patients with mean diurnal IOP levels below 14mmHg might not benefit from the procedure at all.