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A 17-year-old girl with a few years' history of declining vision, photophobia, and dry eye symptoms was referred to our clinic. She noted that the vision in the right eye declined significantly over the past several months. On her last year examination, her uncorrected distance visual acuity (UDVA) was recorded as 20/25 in both eyes with a corrected distance visual acuity (CDVA) of 20/20 in both eyes with minimal refractive error, with a diagnosis of bilateral Salzmann nodular degeneration. The patient was given artificial tears and was encouraged to wear sunglasses. On examination now, UDVA was 20/70 in the right eye and 20/40 in the left eye. The manifest refraction was -2.00 + 1.25 × 96 in the right eye and -1.00 + 2.00× 34 in the left eye, with a CDVA of 20/50 and 20/30, respectively. Slitlamp examination revealed superficial reticular stromal scar with clear intervening spaces involving the anterior 75 μm of the stromal cornea in the central 6.0 mm optical zone (Figure 1).JOURNAL/jcrs/04.03/02158034-202104000-00021/figure1/v/2021-04-19T183640Z/r/image-tiffJOURNAL/jcrs/04.03/02158034-202104000-00021/figure2/v/2021-04-19T183640Z/r/image-tiff The rest of the anterior and posterior segment examination was completely normal and noncontributory. Anterior segment optical coherence tomography (AS-OCT) revealed subepithelial lesion involving the central aspect of the cornea in the right eye more than that in the left eye (Figure 2). Family history was significant for an older sister with a similar problem who never required medical attention. She also has mild photophobia and dry eye symptoms. What is your differential diagnosis? What diagnostic test will help you in your diagnosis and clinical decision-making? What is the most likely diagnosis in this case? Do you recommend medical and/or surgical intervention in the right eye, realizing that there has been exacerbation of her ocular condition in the most recent year? What is the long-term prognosis and future plan for a patient with this potential condition?

The Purpose of present study was to investigate the effect of riboflavin/ultraviolet-A-induced collagen cross-linking (CXL) on central cornea, limbus and intraocular pressure (IOP). This was an animal experimental study. The right corneas of 10 rabbits were ultraviolet-A irradiated (3 mW/cm2 for 30 minutes) after de-epithelialization and instillation of 0.1% riboflavin / 20% Dextran drops. Left corneas served as controls. Samples were examined histologically one month postoperatively. Before and after treatment, IOP measurements were recorded bilaterally. At central cornea of eyes underwent CXL keratocyte repopulation, normal arrangement of collagen fibres and a statistically significant change in fibres diameter were detected, compared to controls. At limbus area, there were not any significant histological differences after CXL. There was no statistically significant difference between pre- and postoperative IOP in all eyes.

Purpose To compare small nerve fiber damage in the central cornea and whorl area in participants with diabetic peripheral neuropathy (DPN) and to examine the accuracy of evaluating these 2 anatomical sites for the diagnosis of DPN. Methods A cohort of 187 participants (107 with type 1 diabetes and 80 controls) was enrolled. The neuropathy disability score (NDS) was used for the identification of DPN. The corneal nerve fiber length at the central cornea (CNFLcenter) and whorl (CNFLwhorl) was quantified using corneal confocal microscopy and a fully automated morphometric technique and compared according to the DPN status. Receiver operating characteristic analyses were used to compare the accuracy of the 2 corneal locations for the diagnosis of DPN. Results CNFLcenter and CNFLwhorl were able to differentiate all 3 groups (diabetic participants with and without DPN and controls) (P < 0.001). There was a weak but significant linear relationship for CNFLcenter and CNFLwhorl versus NDS (P < 0.001); however, the corneal location x NDS interaction was not statistically significant (P = 0.17). The area under the receiver operating characteristic curve was similar for CNFLcenter and CNFLwhorl (0.76 and 0.77, respectively, P = 0.98). The sensitivity and specificity of the cutoff points were 0.9 and 0.5 for CNFLcenter and 0.8 and 0.6 for CNFLwhorl. Conclusions Small nerve fiber pathology is comparable at the central and whorl anatomical sites of the cornea. Quantification of CNFL from the corneal center is as accurate as CNFL quantification of the whorl area for the diagnosis of DPN.

Keratolimbal allograft (KLAL) transplantation has been proved to be a useful surgical procedure for limbal stem cell deficiency patients. However, information about in vivo ocular surface changes in those patients is limited, due to the lack of a reliable and non-invasive technique for closely monitoring the changes of KLAL grafts. The aim of this study is to characterize the cellular changes in the limbus and central cornea after KLAL in patients with severe ocular chemical injury, using in vivo laser scanning confocal microscopy (LSCM). This is a prospective, noncomparative, observational case series. Twenty-three patients (23 eyes) with total limbal stem cell deficiency due to ocular chemical injury were recruited. KLAL with or without other concurrent surgery were performed. LSCM and slit-lamp examination were performed on the limbus and the central cornea before surgery and at 6 and 12 months postoperatively. Presence of palisades of Vogt, limbal basal epithelial cell density within the palisades of Vogt (LEC), limbal dendritic cells (DC) density, and central corneal basal epithelial cell (CEC) density were assessed by LSCM. All patients completed 12 months of follow-up. Twenty-one patients were male and two were female, with a mean age of 39.5 ± 12.5 years. Six cases were due to acid burns, and the others were alkali burns. Palisades of Vogt were observed in all surviving grafts but were absent in graft failure. The epithelial cells in the central cornea of the failed graft had lost the classic polygonal morphology of the normal corneal basal epithelial cells. The cell density of LEC and CEC decreased significantly, whereas DC density increased in the failed grafts over time. In vivo LSCM is a useful tool for monitoring the cellular changes in KLAL grafts, and has the potential to diagnose the failure of KLAL grafts at the cellular level.

Purpose: To report the in-vivo confocal microscopic findings of dendritiform cells in the central corneal epithelial layer in a case of mixed bacterial keratitis associated with severe immunologic reaction. Design: Observational case report. Methods: A 25-year-old male suffered from contact lens-related mixed bacterial keratitis with a dense eccentric immune ring. In-vivo confocal microscopy was performed to study the different layers of the central and peripheral cornea in the lesion and the fellow eye. Results: Several dendritiform cells were found in the basal and superficial epithelial layers of the central cornea in the lesion eye, which was also the area of the dense immune ring formation. No such cells could be identified in the fellow eye or the unaffected area of the lesion eye. Conclusion: Corneal dendritiform cells, possibly dendritic or Langerhans cells, can be identified in severe corneal immunologic conditions using in-vivo confocal microscopy. The role of these cells in ocular immunity is i...

The purpose of this study was to evaluate the penetration of gentamicin into the central, midperipheral and peripheral cornea of rabbits following iontophoresis to the central 3 mm of the cornea. Four groups (groups 1-4) of five rabbits (one eye per rabbit) underwent corneal iontophoresis using gentamicin dissolved in agar. Low (1 mg/ml) and high (10 mg/ml) concentrations of gentamicin in agar were used for one or ten minutes. Two control groups (groups 5 and 6) of five eyes each underwent mock iontophoresis with low and high concentrations of agar-gentamicin mixture. Following sacrifice of the rabbits, the central, midperipheral and peripheral parts of each cornea were excised. Gentamicin concentration was determined in each part of every cornea. High concentrations of gentamicin (951.6 +/- 369.4 microg/ml to 26.6 +/- 41.34 microg/ml) were obtained in the central parts of all the iontophoresis-treated corneas. In each group, except group 6, central corneas had higher concentrations of gentamicin compared to midperipheral corneas (p = 0.038 to p = 0.021), and midperipheral corneas had higher levels than peripheral corneas (p = 0.038 to p = 0.021). Following iontophoresis, gentamicin is found in all portions of the corneas; however, the highest concentration of the drug remains in the central cornea.

Central cornea thickness (CCT) was measured in 32 patients with systemic sclerosis by the Haag-Streit pachymeter with improved centrality. Results were compared with measurements in 29 healthy adults matched with respect to sex and age. CCT was increased (P less than 0.001) in patients with systemic sclerosis (mean 0.56 mm, average SD right and left side 0.0297 mm) as compared to the controls (mean 0.51 mm, SD 0.0109 mm). CCT of right and left eye was increased in 69% and 72% of patients with systemic sclerosis as compared to controls (mean 0.51 mm +/- 2 SD). CCT increased during the first 8 years of the disease (correlation coefficient 0.593) reaching a plateau after 8 years (correlation coefficient 0.005). CCT did not increase during medical treatment with collagen inhibitors. Measurement of CCT may be useful as a supplement to other quantitative methods for diagnosis and control of systemic sclerosis.

Microwave thermokeratoplasty (MTK) is a surgical procedure for the correction of pathologic corneal steepening. The purpose of this study was to examine the postoperative outcomes of eyes with advanced keratoconus that underwent femtosecond-laser zig-zag penetrating keratoplasty (z-PK) following MTK for reshaping of the central cornea. This study involved 32 eyes of 32 consecutive advanced keratoconus patients; i.e., 25 eyes of 25 patients who underwent MTK prior to z-PK (MTK + z-PK group), and 7 eyes of 7 patients who underwent z-PK alone (z-PK group). In all treated eyes, visual acuity (VA) and corneal topography were measured before surgery and at 6-months postoperative. At 6-months postoperative, the mean uncorrected distance VA (logarithm of the minimum angle of resolution) and surface regularity index (SRI) of the MTK + z-PK group was 0.62 ± 0.39 (mean ± standard deviation) and 1.26 ± 0.45, respectively, while that in the z-PK group was 1.02 ± 0.18 and 7.64 ± 3.22, respectively. Both variables were significantly better in the MTK + z-PK group than in the z-PK group (P

Purpose. The purpose of this study was to confirm the presence of specific patterns of epithelial response in corneal buttons from keratoconus patients. Methods. This was a retrospective and descriptive study. 90 penetrating keratoplasty specimens obtained from patients diagnosed with keratoconus were evaluated using bright-field microscopy. Morphologically identifiable characteristics including epithelial cell density and epithelial thickness were analyzed on hematoxylin and eosin- (H&E-) and periodic acid of Schiff- (PAS-) stained slides. Results. Three distinctive patterns of epithelial alteration of the central cornea were established. Pattern 3, in which the central epithelium was as thick as peripheral epithelium, was the commonest (44.4%), followed by the pattern 2, defined as central epithelium thinner than periphery epithelium (38.9%), and the uncommonest pattern was number 1, with central epithelium thicker than the periphery (16.7%). Conclusions. Three distinctive histologic patterns that could potentially have a diagnostic and prognostic value in keratoconus patients were found.

PURPOSE To ascertain whether offsetting the Descemet membrane endothelial keratoplasty (DMEK) punch can expand the donor pool in conjunction with prepunched and preloaded services by recapturing the corneas otherwise excluded by the conventional central clear zone criteria. METHODS In this retrospective review of corneas recovered and processed for DMEK by a single eye bank between March 2017 and October 2018, corneas failing to meet the conventional central clear zone requirement during initial evaluation (defined as an area in the central cornea where an 7.5- to 8.0-mm diameter graft can be obtained free of previous surgical scars, Descemet tears, or confined areas of endothelial defects) were further evaluated for offset punching. Corneas with a central endothelial cell density of at least 2000 cells/mm at the initial screening (average of 3 specular images assessed with the center dot method) that had a clear zone of 7.5- to 8.0-mm diameter where a graft could be obtained were designated as eligible for offset punching for either prepunched or preloaded DMEK. RESULTS A total of 2607 corneas were found to be suitable for DMEK using the conventional central clear zone criteria. An additional 62 corneas were deemed DMEK suitable by offsetting the punch, yielding a 2.4% increase in the availability of DMEK suitable corneas. CONCLUSIONS Offsetting the DMEK punch can recapture corneas otherwise excluded from the DMEK donor pool because of a failure to meet the conventional central clear zone criteria, and by our estimation may help eye banks meet the growing demand for DMEK tissue while maximizing the transplant potential of every cornea.

PURPOSE To explore the relationship between the degree of iris pigmentation and corneal sensitivity threshold (CST) on a variety of different ethnicities, using the air-jet noncontact corneal aesthesiometer and by applying a consistent method of subject iris pigmentation classification. METHODS A total of 200 subjects (mean age 23.7 ± 3.1 years, 127 women) participated in this clinical cross-sectional study: 100 whites, 40 Asians, 40 Chinese, and 20 Afro-Caribbeans. CST was assessed within the central cornea using a noncontact corneal aesthesiometer, and the degree of iris pigmentation of each subject was noted according to the Seddon method using a set of graded photographs of iris pigmentation (grades 1-5). Inclusion criteria were absence of ocular disease including dry eye, no contact lens wear, and no use of artificial tears. Statistical testing between ethnicities was made by the pairwise t test with Holm adjustment, and a linear model was set up to analyze the effects of ethnicity and iris grade. RESULTS A moderate trend for increasing CST with increasing iris pigmentation grade for all ethnicities was observed (R = 0.46; P < 0.0001), with CST changing from 0.66 ± 0.16 mbars for grade 1, 0.74 ± 0.18 mbars for grade 2, 0.86 ± 0.31 mbars for grade 3, 0.85 ± 0.32 mbars for grade 4, and 1.08 ± 0.40 mbars for grade 5. This correlation was stronger within the white group, representing the only ethnicity with all iris pigmentation grades (R = 0.50; P < 0.0001). CONCLUSIONS There is a moderate relationship between corneal sensitivity and the degree of iris pigmentation, with sensitivity increasing as iris pigmentation decreases. This relationship is stronger within whites.

Purpose To investigate corneal sublayer alterations during the postoperative period after small-incision lenticule extraction (SMILE). Setting Synslaser clinic, Oslo, Norway. Study design Retrospective. Methods Patients who underwent SMILE for treating myopia were included. The thicknesses of the corneal epithelium, cap, stromal part of the cap (StromaCap), residual stromal bed (StromaRes), and total stroma (StromaTot) were measured using spectral-domain optical coherence tomography at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively. Postoperative changes in the corneal sublayer thicknesses were analyzed and correlated with changes in spherical equivalence and anterior and posterior keratometry (K). Results The study was based on analyses of the right eyes of 51 patients. From 1 day to 6 months postoperatively, the corneal epithelium, cap, StromaCap, StromaRes, and StromaTot thicknesses increased from 54.4 ± 4.0 µm to 57.3 ± 5.2 µm; 137.1 ± 5.5 µm to 140.3 ± 5.1 µm; 82.7 ± 5.9 µm to 82.8 ± 6.3 µm; 375.0 ± 40.8 µm to 381.4 ± 30.6 µm; and 457.6 ± 41.1 µm to 462.1 ± 36.7 µm, respectively. Between 1 month and 6 months postoperatively, the increase in anterior K correlated significantly with the thickening of the cap (r = 0.37, P = .03) and the stromal component of the cap (r = 0.36, P = .04) within the central cornea. Conclusions The post-SMILE remodeling behavior between the anterior (StromaCap) and posterior (StromaRes) stroma were dissimilar. There was a significant correlation between changes in anterior K and the central cap and the stromal component of the cap. This might be because of biomechanical changes, tissue remodeling, and wound healing or a combination of some or all of the aforementioned processes.

Purpose To evaluate the effect of a single rebubbling procedure after Descemet membrane endothelial keratoplasty (DMEK) on corneal backscatter and endothelial cell loss (ECL). Methods Medical records of 130 consecutive DMEK cases (118 patients) were reviewed and 3 groups were formed: group 1 (n = 32), consisting of DMEK cases followed by 1 rebubbling; group 2a (n = 55), including uneventful DMEK cases with complete graft attachment; and group 2b (n = 25), including uneventful DMEK cases with minor peripheral detachment, not requiring rebubbling. Scheimpflug corneal densitometry (CD) of the central (0-2 mm), paracentral (2-6 mm), and mid-peripheral (6-10 mm) zones, endothelial cell density, central corneal thickness, and corneal volume were measured preoperatively and at 3, 6, 12, and 24 months. Results Central CD in group 1 decreased from 32.3 ± 8.3 grayscale units preoperatively, to 21.2 ± 3.5 at 24 months. In group 2a, CD decreased from 37.0 ± 11.9 to 19.4 ± 3.0 and in group 2b from 32.5 ± 8.8 to 19.8 ± 3.1. No significant differences were observed among the 3 groups at any examination time point (P ≥ 0.12). At 3 months, paracentral CD of group 2a was significantly lower than that of group 1 (P = 0.047). Endothelial cell density at 3 months was higher in group 2a (1613 ± 503 cells/mm) than in group 1 (1350 ± 557 cells/mm; P = 0.033). ECL at 24 months was 56%, 43%, and 53% in groups 1, 2a, and 2b, respectively. Group 2a showed the lowest ECL, central corneal thickness, and corneal volume throughout the study period. Conclusions A single rebubbling procedure does not increase the CD of the central cornea and but results in significantly higher ECL compared with uneventful DMEK with complete graft attachment.

A 13-year-old Japanese female diagnosed with spondyloepiphyseal dysplasia congenita (SEDC) was referred for ophthalmologic evaluation. Examination with slit-lamp and optical coherence tomography revealed bilateral thin cornea with diffuse corneal opacity which was localised at the posterior stromal depth in the central cornea. Unlike the two previously reported cases of diffuse and nodular patterns of corneal opacity in SEDC, the current case exhibited a rare form of corneal opacity. SEDC is one of the type II collagenopathies, characterised by dwarfism because the mutations in COL2A1 prevent bone growth. Although the existence of type II collagen has not been reported in the human corneal stroma, the aetiology of the opacity in the corneal stroma in SEDC type II collagenopathy is of interest.

Fifty-two guinea pigs ( Cavia porcellus ) with normal ophthalmic examinations were included in this study to determine whether there are differences in the intraocular pressure (IOP) according to age, while assessing the clinical usefulness of 2 different tonometry methods for this species. The animals were divided into 2 groups according to age: young (4 weeks old, 29 animals) and adult (3 to 36 months, 23 animals). Tonometry was performed oculus utro (OU) in the central cornea according to the manufacturer's recommendations. Only measurements with low standard deviation (SD 0.05) nor between sexes (p > 0.05). TonoVet readings were obtained faster than Tono-Pen VET readings (less than 1min vs 3.38 ± 1.27min, respectively [p

To compare changes in the shape and astigmatism of the total, anterior, and posterior cornea between eyes with long-length clear corneal incisions (CCIs) and eyes with short-length CCIs in cataract surgery.Hayashi Eye Hospital, Fukuoka, Japan.Prospective case series.Both eyes of patients having phacoemulsification with temporal CCIs were randomized to have a long-length (≥1.75 mm) or short-length (1.75 mm) CCI. Corneal astigmatic changes were decomposed to vertical/horizontal (Jackson cross-cylinder, axes at 180 degrees and 90 degrees [J0]) and oblique changes (Jackson cross-cylinder, axes at 45 degrees and 135 degrees [J45]) using power vector analysis. Corneal shape changes were assessed using the average of the difference map on videokeratography 2 days and 2, 4, and 8 weeks postoperatively.The mean J0 and J45 values of the total cornea in the 120 eyes evaluated were significantly greater in the long CCI group than in the short CCI group at all follow-ups (P ≤ .0290). The videokeratography showed a wedge-shaped flattening in the total and anterior cornea and a steepening in the posterior cornea around the CCI 2 days postoperatively in both groups. This wound-related flattening of the total and anterior cornea rapidly reduced but persisted until 8 weeks, whereas the steepening of the posterior cornea disappeared within 4 weeks. These changes extended closer to the central cornea in the long CCI group than in the short CCI group.Corneal astigmatic changes were significantly greater after long CCI than after short CCI. The wound-related shape changes occurred immediately postoperatively but rapidly diminished.

Factors governing the steady-state IOP have been extensively studied; however, the dynamic aspects of IOP are less understood. Clinical studies have suggested that intraocular pressure (IOP) fluctuation may be associated with glaucoma risk. This study aims to investigate how stiffening of corneoscleral biomechanical properties affects IOP spikes induced by rapid microvolumetric change. Porcine eyes (n = 25 in total) were subjected to volumetric infusions before and after external treatment of a circular area (11 mm diameter) in either the central cornea or posterior sclera. The treated area in the control group was immersed in phosphate-buffered saline (PBS) for 40 min, while the treated area of the chemical crosslinking group was immersed in 4% glutaraldehyde/PBS for 40 min. A subset of the sham-treated eyes was also subjected to volumetric infusions at a raised steady-state IOP. The magnitude of IOP spikes increased after localized chemical crosslinking of either the cornea (27.5% increase, p < 0.001) or the sclera (14.3% increase, p < 0.001) with corneal crosslinking having a stronger effect than scleral crosslinking (p = 0.018). We also observed that raising the steady-state IOP from 15 to 25 mmHg resulted in marked increase in IOP spike magnitudes by 63.9% (p < 0.001). These results suggested that an increased corneoscleral stiffness could significantly increase IOP spike magnitudes at the same volumetric change. Corneal stiffness appeared to have a strong impact on the IOP spike magnitude and may play a major role in regulating rapid volume-pressure dynamics. An increase in steady-state IOP also resulted in larger IOP fluctuations due to the increased “apparent” stiffness of the ocular shell, suggesting a potential interaction between the magnitude of IOP and its fluctuations. Corneoscleral properties may represent additional pathways for understanding and managing glaucoma risk and warrant future investigation.

Objective To determine the efficacy of collagen cross-linking (CXL) as an adjunct to suturing in the repair of corneal lacerations. Methods A cadaveric study was undertaken in which a linear 5 mm corneal laceration was created in the central cornea of 20 eyes. The eyes were then randomized to receive 1 (n = 8), 2 (n = 8), or 3 (n = 4) standard corneal sutures. The burst pressure of the wound was then measured. All eyes in the 1- and 2-suture group then underwent standard CXL, with burst pressure repeated afterward. Results The initial wound burst pressure in the 1-, 2-, and 3-suture groups was 54.9, 74.0, and 201.2 mm Hg, respectively. After CXL, wound burst pressure increased by a mean of 3.2 and 62.3 mm Hg in the 1- and 2-suture groups, respectively. This change was statistically significant in the 2-suture group ( p = 0.017). After CXL, the 2-suture group still had a significantly lower burst pressure compared with the 3-suture group ( p = 0.011). Conclusions The study highlights a potential novel application for CXL to strengthen corneal wounds. Provided that suture density is sufficient to appose the wound edges, CXL may result in short-term wound strengthening. This could potentially allow for decreased corneal suture density and a corresponding decrease in suture-related complications.

Mohammad Reza Djodeyre,1 Jaime Beltran,2 Julio Ortega-Usobiaga,3 Felix Gonzalez-Lopez,4 Ana Isabel Ruiz-Rizaldos,1 Julio Baviera2 1Department of Refractive Surgery, Clinica Baviera, Zaragoza, 2Department of Refractive Surgery, Clinica Baviera, Valencia, 3Department of Research and Development, Clinica Baviera, Bilbao, 4Department of Refractive Surgery, Clinica Baviera, Madrid, Spain Purpose: To study long-term refractive and visual outcomes of laser in situ keratomileusis (LASIK) in eyes with a postoperative thin central cornea. Methods: In this retrospective observational case series, we studied 282 myopic eyes with a normal preoperative topographic pattern and postoperative thin corneas (275 µm. Keywords: LASIK, thin, cornea, ectasia, myopia, pachymetry, topography

To investigate the influence of benzalkonium chloride (BAC) on corneal Langerhans cells (LCs) and on the development of dry eye.A randomized double-blind clinical trial was performed in 20 healthy volunteers. One eye of each subject was treated with a 0.01% BAC solution (and the fellow eye with a placebo solution) three times daily for 12 weeks. The distribution and density of LCs in the central and peripheral corneal epithelium were evaluated by in-vivo confocal laser-scanning microscopy (CLSM). The subjects were monitored for dry eye (subjective discomfort, slit-lamp biomicroscopy, tear film break-up time, Schirmer's test).In the BAC group, compared with placebo, a marked increase in LC density was found in the central cornea at Week 6 and in the central and peripheral cornea at Week 12. LC density then decreased again in both zones after the end of treatment, falling toward (or even below) baseline levels. Significant changes in the LC count relative to baseline were found at Week 12 in the central and peripheral cornea in the BAC group as well as in the peripheral cornea in the placebo group. LC density in the BAC group increased more rapidly in the central than in the peripheral cornea. During therapy the BAC group showed no signs of dry eye.12-week application of a 0.01% BAC solution in healthy volunteers induces a significant increase in LCs in the central cornea at Week 12 without dry-eye changes. The return of LC counts toward (or even below) baseline levels just four weeks after the end of BAC administration demonstrates the rapid normalization of the inflammatory environment.

PurposeCharacterization of the biomechanical properties of the human eye has a number of potential utilities. One novel purpose is to provide the basis for development of suitable tissue-mimicking material. The purpose of this study was to determine the indentation and needle insertion characteristics on human eye globes and tissue strips.MethodsAn indenter assessed the elastic response of human eye globes and tissue strips under increasing compressive loads. Needle insertion determined the force (N) needed to penetrate various areas of the eye wall.ResultsThe results demonstrated that globes underwent slightly greater indentation at the midline than at the central cornea, and corneal strips indented twofold more than scleral strips, although neither difference was significant (P=0.400 and P=0.100, respectively). Significant differences were observed among various areas of needle insertion (P

Aim To investigate the effects of fibrovascular traction and the pooling of tears at the pterygium apex on the corneal topographic changes induced by pterygium. Methods A total of 16 eyes of 14 cases with primary pterygium were included in the study. A computerized corneal topography system was used for corneal topography examinations. Baseline keratographs were taken two times at straight gaze. A repeat corneoscope photograph was immediately obtained in temporal gaze. Then the tears at the pterygium apex were dried with a cellulose sponge, and a new corneoscope photograph was immediately obtained without allowing one to blink. Corneal topographic maps (numeric maps) were divided into 301 fields in 24 meridians. One colour was allocated to each field, representing its mean refractive power for all groups. In all eyes, keratometric astigmatism at the 3 mm central cornea and total mean corneal refractive power were found. Data were compared using paired-samples two-tailed t-tests. Results Keratometric astigmatism at the 3 mm central cornea was significantly reduced at the temporal gaze (3.10±2.34 D, t=3.40, P=0.027) and dried eyes (2.12±1.01 D, t=4.74, P=0.001) according to the first baseline measurement (4.31±1.91 D) of the total mean corneal refractive power was found to be 43.45±1.28 D (39.29–45.87) at the first baseline measurement. There was no change at the temporal gaze (43.54±1.06 D, P>0.05). However, the total corneal refractive power was significantly higher in dried eyes (44.26±0.93 D, t=34.92, P

a b s t r a c t Background/Purpose: Although scleral contact lenses are prescribed with increasing frequency, little is known about their long-term effects on ocular physiology. The main goal of this paper is to predict values of oxygen transmissibility of scleral lens systems by applying the concept of resistors in series to parameters characteristic of current scleral lenses. A second aim is to find the maximal lens and post-lens tear layer thickness combinations above which hypoxia-induced corneal swelling would be found. Methods: Theoretical calculations were used to predict the oxygen transmissibility of scleral lens systems, considering several material permeabilities (Dks 100–170), varying lens thicknesses (250–500 m), the known tear permeability (Dk of 80) and expected post-lens tear layer thicknesses (100–400 m). The Holden–Mertz Dk/t criteria of 24 Fatt units for the central cornea and the Harvitt–Bonanno criteria of 35 Fatt units for the limbal area were used as reference points. Results: Our calculations of oxygen transmissibility, with varying tear layer and lens thicknesses, ranged from 10 to 36.7 at the scleral lens centers and from 17.4 to 62.6 at the peripheries. Our calculations of maximum central lens thicknesses show a practical range of 250–495 m, in conjunction with a post-lens tear layer thickness of 100–250 m. Conclusion: Our computations show that most modern scleral lenses, with recommended fitting techniques, should lead to some level of hypoxia-induced corneal swelling. Recommendations are made to minimize hypoxia-induced corneal swelling: highest Dk available (>150) lens with a maximal central thickness of 250 m and fitted with a clearance that does not exceed 200 m.

PURPOSE To determine the distribution of central and peripheral corneal thickness values and its determinants in an Iranian population. METHODS This population-based study was conducted between 2009 and 2010 in Shahroud, with a response rate of 82.2%. Here in, we present the data on central and peripheral corneal thickness in 3890 participants of the study, which included all 40- to 64-year-old participants except those with a history of ocular surgery. Measurements were done with the Pentacam, and correlations with age, gender, height, body mass index, and refraction were tested. RESULTS The mean age (± standard deviation) of the participants was 50.7 years (± 6.2 years). Mean corneal thickness in the thinnest point, the center, and 3 mm away from it in the inferior, superior, nasal, and temporal directions were 525.5 ± 35.9 μm, 528.5 ± 35.8 μm, 608.2 ± 39.8 μm, 635.5 ± 41.9 μm, 611.7 ± 43.2 μm, and 601.0 ± 40.4 μm, respectively. The thinnest point was in the inferotemporal quadrant in 87.5% of cases. The center of the cornea was thinner than 500 μm in 36.6% of myopic cases and 21.8% of hyperopic cases. The thickness and location difference between the center and thinnest point were statistically significant (P < 0.001). Central corneal thickness was directly correlated with refraction (P = 0.028) and inversely with age (P = 0.027). CONCLUSIONS In this population-based study, the thinnest point was usually located inferotemporally and the thickest point superiorly. The peripheral cornea was significantly thicker than the central cornea but thinned faster with age. The thickness difference between the thinnest and central points was significantly greater in men. People with hyperopia had thicker corneas compared with those with myopia.

To investigate the influence of positional deviations on the rebound tonometer measurement.Ten white rabbits were used. A bottle of balanced salt solution was connected to the anterior chamber, and the IOP was altered by changing the height of the bottle. A pressure transducer was also connected to the anterior chamber. The IOP was measured by the rebound tonometer (RBT), the Tonopen XL, and the Perkins handheld applanation tonometer at optimal conditions and compared each tonometer. Then, the effect of placing the RBT probe at different distances, different lateral positions, and different angles to the cornea on the IOP was determined.The RBT had the lowest variance in all three tonometers. The IOP measured with the RBT was not significantly altered when the distance from the cornea was 4 to 8 mm, or when the probe was displaced 2 mm to the central cornea, or when the probe was placed at an angle of 20° from the central axis.The low variance of the RBT measurements and the non-significant changes in the IOP when the probe of the RBT was not on the central axis indicate that the RBT is useful for animal models of glaucoma. Further studies examining its use (repeatability and reliability) in human infants whose eyes and head are usually moving are required.

PURPOSE It has been said that Langerhans cells can be induced to migrate into the central cornea by various stimuli. We investigated whether extended wear of hydrogel lenses induced the migration of Langerhans cells into the central cornea. METHODS Guinea-pig eyes were fitted with hydrogel contact lenses, and the number of adenosine triphosphatase (ATPase)-positive dendritic cells at the limbus, peripheral, and central corneal epithelium was quantified after 1, 2, 4, and 8 nights of extended wear. The cells were identified with histochemical procedures using ATPase stain. RESULTS At baseline, ATPase-positive dendritic cells were seen at the limbus and peripheral cornea, with the density decreasing from limbus to peripheral cornea. There were no cells in the central cornea. With extended wear, cells increased in number at the peripheral cornea from 2 nights onward, and cells were seen in the central cornea from 4 nights onward. CONCLUSION Extended wear of hydrogel lenses induced migration of ATPase-positive dendritic cells (Langerhans cells) into the central cornea. It is possible that they may play a role in the pathophysiology of some of the adverse events seen with contact lens wear.

The objective of this study was to assess the variability of readings made using the Tonovet® rebound tonometer for measurement of intraocular pressure (IOP) in the peripheral cornea and in angulated positions on the canine corneal surface. Forty-six client-owned dogs admitted for ophthalmic evaluation at the Queen's Veterinary School Hospital, University of Cambridge were included in the study. IOP readings were taken at a variety of locations and using the tonometer at a number of different angles to the cornea: 1) Perpendicularly at center of the cornea (CC); 2) At the center of the cornea but with the tonometer positioned at four angles, and 3) At four different points on the peripheral cornea. All values were compared with the values recorded at the recommended CC position. IOP values were significantly underestimated in seven positions, with median and interquartile range from 12.1 ± 4 mmHg (nasal on periphery) to 15 ± 5 mmHg (laterally angled at center), varying between 0 mmHg to 2.9 mmHg from the CC value. While dorsally angled in the central cornea were not significantly different from those at CC (p = 0.09). Median values were lower for measurements in peripheral positions when compared to angled central positions. These results demonstrate that angling the tonometer or measuring in peripheral regions can result in small but statistically significant underestimation of IOP values.

BACKGROUND INTACS are two, arc like, PMMA segments which were designed to be surgically inserted into the deep corneal stroma to flatten the central cornea. Their original application was for the refractive correction of mild myopia (−1 to −3D). However, because of the superior accuracy and familiarity with the excimer laser by refractive surgeons, they are rarely used for this indication, except in patients with forme fruste keratoconus or extremely thin corneas with less than 3D of Myopia (1,2). Dr. Joseph Colin in France first conceived of the concept of using INTACS to treat patients with keratoconus and published his first report on the safety and efficacy for this indication in 2001(3). At 1 year, all 10 patients he operated became contact lens tolerant and demonstrated an improvement in both uncorrected and best-corrected acuity (4). Since his pioneering work, corneal surgeons throughout the word have adopted this technology to treat patients with mild to moderate keratoconus who are contact lens intolerant and/or who desire a modest improvement in uncorrected and best-corrected visual acuity (5-14). In the United States 0.25mm, 0.275mm, 0.30mm, 0.325mm and 0.35mm segments are available for use. They are approved in the United States by the FDA under an Human Devise Exemption for compassionate therapeutic use. Outside of the United States .40mm and 0.45mm sized segments are also available. Competitive devices the Ferrara ring and the Keraring are also sold and marketed outside of the United States since they do not have FDA approval in the USA. The main difference between these two devices is that with INTACS the optical zone is approximately 7mm while the Ferrara and Kerarings have an optical zone of the order of 4.5 to 5mm. Recently Intacs SK was introduced outside of the United States. They have an optical zone of 6 mm and have a round design to minimize glare. They may be used to correct larger myopic and astigmatic refractive errors than INTACS because of their design and closer proximity to the visual axis(15)

Purpose: To examine if central corneal thickness (CCT) is different in emmetropia and high myopia. Methods: 57 emmetropic subjects (0 to + 1.5 D) and 48 high myopes (all more than − 6 D in spherical equivalent refraction) were studied. CCT was measured by a Haag–Streit Optical Low-Coherence Reflectometry (OLCR) pachymeter, a recently developed high precision pachymeter with a standard deviation (SD) for repeated measurements of 1 µm. Results: Mean CCT for the emmetropic group was 538.6 µm (SD = 32.1), and for the myopic group 527.7 µm (SD = 35.0). Neither the mean CCT nor the variance from the two groups showed a statistically significant different (p > 0.05). Conclusion: CCT is not systematically altered in myopia. The process by which the myopia progresses does not to a measurable degree influence the central cornea.

In vivo confocal microscopy was performed on the central cornea of both eyes of a patient with megalocornea and central mosaic dystrophy. In the stroma, starting just below Bowman's membrane, polygonal, moderately reflective areas of opacification separated by diagonal hyporeflective striations were observed. The opaque areas appeared smaller in the anterior stromal layers and seemed to get larger towards the posterior stroma. The epithelium, Bowman's membrane and endothelium appeared normal. In vivo confocal microscopy is helpful in evaluating the morphological characteristics of corneal dystrophies, degenerations or developmental abnormalities of the cornea, and may prove to be helpful in understanding their pathophysiology.

Purpose. To investigate inter- and intra-system variations and the effect of corneal drying using a recently developed pDEM. Methods. pDEM was used to simulate “normal” and “dry eye” conditions using two “lacrimation-blink” intervals (20 s and 60 s). Corneas were examined/graded with sodium fluorescein before and after the experiment. At the end of each experiment, corneas were assessed by trypan blue exclusion technique. Two duplicated pDEM systems were set up and tested to investigate reproducibility. Results. There was no significant difference in the results produced by the two pDEM systems. In the eyes under “normal” condition, there was no significant increase in the fluorescein grading. However, in eyes under “dry eye” condition, fluorescein staining increased and the number of non-viable cells in the central cornea increased. Conclusions. This novel pDEM system provides a useful assessment tool for the study of causative factors and new treatment strategies for dry eye syndrome.

Two sets of corneal thickness (CT) measurements at five corneal locations were made with Orbscan on 33 normal young adults. No significant intravisit and intervisit differences at any of the corneal locations were found (Repeated measures ANOVA, F 0.49). The 95% limits of agreement (95% LA) for between-measurement differences for the central cornea was about +/-19 microm (or 3%), indicating good repeatability; for the inferior, temporal and nasal corneal locations, the 95% LA were close to +/-30 microm (approximately 4-5%); and for the superior corneal location, they were about +/-35 microm (or 5.5%). The estimated number of repeated measurements that should be taken for accurate CT measurements (at any of the five corneal locations and excluding outliers of >3 S.D.) of 2% (standard error) is < or =2, and of 3% is 1. This study shows that only central CT measurements with the Orbscan are repeatable. The role of the Orbscan pachometry is therefore limited and is recommended for central CT measurements only.

Desiccation of the ocular surface in dry environments is one of the factors contributing to discomfort in dry eye patients. An in vivo desiccation model was used to test efficacy of artificial tear products for prevention of ocular surface damage during extended desiccating exposure. One drop of an artificial tear or a lens rewetting solution was placed on the eye of an anesthetized rabbit and the eye was held open with a speculum for 2 hr. Desiccated eyes were held open for 2 hr without application of a tear solution. Eyes were stained with 1% methylene blue in BSS. Naive control eyes were stained with methylene blue without prior desiccation. The percentage of corneal area stained was scored and a 8-mm button of central cornea was extracted in acetone:saturated sodium sulfate (7:3). Absorbance of extracts was measured at 660 nm. Extract analysis showed that four of the five tear products tested offered complete protection from desiccation (not different from naive control), while one solution, which was...

We examined the morphology of the corneal surface epithelial cells in 13 eyes of 13 subjects using specular microscopy. We determined cell area, perimeter, and shape comparing the central cornea with the inferior and superior periphery. We found surface epithelial cells are significantly smaller in the central cornea. The cells measured 560 +/- 93 square microns in the central cornea, 850 +/- 135 square microns in the superior cornea and 777 +/- 176 square microns in the inferior cornea (p less than .005). Newly emerged surface cells are smaller and are thought to enlarge with time. We postulate that lid shearing forces are greater in the central cornea and contribute to epithelial cell exfoliation. We further postulate that preferential shearing of central corneal surface cells is an important factor driving the centripetal movement of corneal epithelial cells.

amaclandi. Gerec ve Yontem: Daha once glokom tanisi almamis ve rutin muayenede cup/disk orani (C/D) ≥ 0.6 olan fizyolojik cukurlasmali 57 olgunun 57 gozu ile C/D ≤ 0.4 olan 55 olgunun 55 gozu (normal grup) ve glokom birimimizde takipli erken glokomatoz hasari olan 56 hastanin 56 gozu calismaya alindi. Tum olgulara tam oftalmolojik muayene, gun ici intraokuler basinc takibi, gonyoskopi, santral kornea kalinligi (SKK), OKT ile RSLT kalinlik analizleri, HRT ile OSB parametreleri olcumleri ve GA testleri yapildi. Tum olgularin birer gozleri randomize olarak secildi. Bulgular: OKT ve HRT ile yapilan olcumlerde uc grup arasinda anlami farklilik oldugu goruldu (p

The healing of stroma and endothelium after a standardized corneal alkali wound was evaluated in sodium-hyaluronan (Na-HA)-treated eyes. Alkali wounds were produced in one eye of each rabbit by applying a 5.5-mm round filter paper soaked in 1 N NaOH onto the central cornea for 60 s. Eyes were then treated with either 1% Na-HA (the treatment group) or phosphate-buffered saline (the control group) 4 times per day for 3 weeks. Endothelial wound morphometry was performed after alizarin red and trypan blue staining, while stromal healing was assessed by counting polymorphonuclear leukocytes (PMNs) and keratocytes in the central and marginal wound areas. During the early healing period the stroma treated with Na-HA had less PMNs than that of the control group. The size of the endothelial defect area measured 5 days after injury was significantly smaller in the Na-HA group than in the control corneas. The present findings indicate that topically applied 1% Na-HA affects stromal and endothelial healing during the early repair process after corneal alkali wounds.

The present study investigated the effect of Na-hyaluronan (Na-HA) on the hemidesmosome morphogenesis in n-heptanol-induced corneal wounds. Central epithelial wounds were induced in the rabbit cornea by applying a 5.5-mm round filter paper, which was soaked in n-heptanol, for 60 s. 1% Na-HA in phosphate-buffered saline (PBS) or PBS alone were topically administered to the wounded cornea 4 times daily for up to 7 days. Epithelial healing rates during the first 2 days were not altered by Na-HA. The number of hemidesmosomes in the basement membrane of the central cornea was significantly increased in both 3- and 7-day groups after treatment with 1% Na-HA. The results suggest that topically applied 1% Na-HA may enhance the formation of hemidesmosomes during the early healing phase in n-heptanol-induced corneal wounds.

Subepithelial haze and concomittant refractive regression are the most important complications of photorefractive keratectomies (PRK) in the higher diopter range. Twenty previously photokeratectomized myopic eyes, which showed a certain level of subepithelial scarring, were examined in the present study. The range of PRK treatment varied between — 4.0 and - 12.0 D (on average - 7.4 ± 3.88 D). Subsequent subepithelial haze was graded between 0.5 and 4.0, according to Hanna et al. The first ultrasound biomicroscopy (UBM) was performed between 1 and 3 months following PRK with the 50–80 MHz transducer of a Zeiss-Humphrey Model 840 ultrasound biomicroscope. A control UBM examination was carried out in each patient 3 months after the initial assessment. The severity of subepithelial haze correlated with the previous photo-ablation depth. Below and including Haze Grade 2.0, UBM showed loss of the Bowman’s membrane and a slight thinning of the central 5.5 mm diameter cornea. Above Grade 2.0, the reflectivity of the anterior stromal parts began to increase. Between Grades 3.0 and 4.0, a hyper-reflective one-third of the anterior stroma with irregular borders was observed. In conclusion, haze graded below 2.0 was not observable with UBM. Haze graded more than 2.0 caused increased anterior stromal reflectivity in the central cornea. Ultrasound biomicroscopy was found to be a suitable method for presenting and following data over time for each patient with serious haze phenomena after excimer laser photo-ablation.

Purpose: To investigate the configuration of the living human corneal subbasal nerve plexus in paired eyes of normal subjects using in vivo confocal microscopy. Methods: Laser scanning in vivo confocal microscopy was performed on both corneas of healthy human subjects, and a grid fixation pattern facilitated examination of consistent areas of central to midperipheral cornea. Macromedia/Adobe Freehand 10 was used to manually arrange images into contiguous montages. The subbasal nerve density and overall patterns were analyzed. Results: Both eyes of 6 subjects (3 women and 3 men, aged between 25 and 36 years) were examined. In all subjects, the subbasal nerve plexus exhibited a clockwise whorl configuration inferior to the central cornea. The mean subbasal nerve density at the whorl was 39.17 ± 4.95 mm/mm 2 and 41.36 ± 4.19 mm/mm 2 in the right and left eyes, respectively. There was no significant difference in the nerve density between the eyes (P = 0.61). Bland and Altman analysis confirmed high intraobserver repeatability and moderate interobserver repeatability. Conclusions: This study reveals the marked similarities between the corneal subbasal nerve plexus configuration in the right and left eyes of the living human cornea, highlighting that the typical mirrorimage symmetry in corneal topographic patterns is not obeyed in respect to corneal innervation and that a clockwise orientation of the subbasal plexus is typically encountered. There was no statistical difference in the subbasal nerve density between the eyes.

Sixty-three eyes of 49 patients with keratoconus were studied by means of computer-assisted corneal topographic analysis. Two patients with keratoconus in one eye had no topographic evidence of keratoconus in the opposite eye. Keratoconic topographic alterations were classified into two groups. The majority of the patients (72%) had peripheral cones, with steepening extending to the limbus. In this group, the steepening was commonly restricted to one or two quadrants. In some cases, however, the changes involved nearly the entire corneal surface. The remaining group (about one quarter of the keratoconus patients) had steepening that was restricted to the central cornea. In either group, the topographic alterations in the two eyes of any single patient were characterized by a high degree of nonsuperimposable mirror-image symmetry (enantiomorphism). In the majority of patients, however, there was a large and statistically significant disparity between the two eyes in the power at the apex of the cone and the total cylinder [mean differences 8.2 +/- 6.0 D (p less than 0.0001) and 4.3 +/- 2.7 D (p less than 0.0001), respectively].

We describe a novel technique on the use of fibrin glue to seal a longstanding partial thickness corneal laceration. A 67-year-old lady was referred to the corneal service with an asymptomatic, partial thickness corneal laceration in the right eye (RE) that had failed to heal spontaneously over a 12-month period. She had no recollection of any history of trauma to that eye, but the laceration appeared clean-cut with well-defined edges, indicating that a sharp object may have caused it. On examination, the best corrected visual acuities were 6/12 RE and 6/6 in her pseudophakic LE. Slit-lamp biomicroscopy of her RE showed a partial thickness corneal laceration 6 mm in length. It started close to the inferotemporal limbus and extended towards the central cornea without passing through the visual axis (figure 1). On high magnification, there were classic epithelial pearls on the surface of …

Purpose: To determine if midperipheral corneal thickness (MCT) has an influence on intraocular pressure (IOP) measurements using noncontact tonometry (NCT). Methods: The corneal thickness profile over a 5-mm diameter (Orbscan IIz) and the IOP (Topcon CT-80 noncontact tonometer) was measured for 51 eyes of 51 healthy subjects aged 21.1±1.6 years; the relationships between corneal thickness and IOP were assessed by Pearson correlation and linear regression. Results: The central corneal thickness (CCT) was 556.1±32.9 μm and generally increased toward the midperiphery, though the magnitude of the midperipheral increase in corneal thickness (MICT, where MICT=MCT-CCT) was not consistently correlated to the CCT. The IOP was related to the CCT (r=0.445, P=0.001) and to the MCT at all midperipheral locations (r=0.357 to r=0.527, P

PURPOSE To describe a patient with Thygeson's superficial punctate keratitis who underwent photorefractive keratectomy for the correction of myopia. METHODS A 49-year-old woman with unilateral Thygeson's keratitis was examined before and after photorefractive keratectomy. RESULTS A myopic patient underwent photorefractive keratectomy in the left eye and gained 20/20 uncorrected visual acuity. Seventeen months after surgery, symptomatic Thygeson's keratitis lesions recurred in the peripheral but not the central cornea. CONCLUSION Photorefractive keratectomy reliably corrected myopia in a patient with previous Thygeson's keratitis. The recurrence of lesions only in the peripheral untreated cornea suggests that the inflammatory signal in Thygeson's keratitis may reside in the superficial corneal stroma.

Just recently studies on glaucoma have emphasised the significance of intraocular pressure in the diagnosis of glaucoma and the importance of intraocular pressure reduction in the management of glaucoma. Central cornea! thickness appears to play an important role in the exact measurement of intraocular pressure and in the diagnostic assessment of glaucoma. Numerous studies have verified that corneal thickness shows systematic differences in different forms of glaucoma. Since deviations of corneal thickness from normal can possibly result in an artificial change of Goldmann applanation values, it would be a most important source of error in the diagnosis of glaucoma to ignore central corneal thickness. Corrections of intraocular pressure measured with applanation tonometry can be achieved in various ways but there is considerable divergence in the results. The absence of a generally accepted algorithm for the correction of intraocular pressure measured with applanation tonometry should not prevent us from a wide application of pachymetry, since it delivers valuable additional information on the individual risk of glaucoma.

Purpose To examine the long-term longitudinal changes in corneal surface configuration as determined by Fourier series harmonic analysis of videokeratography data and of visual acuity and refraction after penetrating keratoplasty (PK). Design Interventional case series. Methods One hundred thirty eyes of 130 consecutive patients who were scheduled for PK using 16 interrupted 10-0 nylon sutures were recruited. Spherical equivalent power, regular astigmatism component, irregular astigmatism (asymmetry and higher-order irregularity) component of the central cornea as determined by Fourier analysis of videokeragraphic data, spectacle-corrected visual acuity, and spherical equivalent were examined at 1 week, and at 1, 3, 6, 9, 12, 18, and 24 months after PK. Results Spherical equivalent power increased considerably for up to 1 month after PK, but thereafter showed no further appreciable change up to the final follow-up at 24 months. The regular astigmatism component decreased markedly for up to 6 months after PK, while the total irregular astigmatism (sum of the asymmetry and higher-order irregularity) component decreased considerably up to approximately 3 months, and then these showed no further relevant change for up to 24 months. Spectacle-corrected visual acuity also improved markedly until approximately 3 months after PK, after which it was virtually stable. Furthermore, important correlations were found between regular and irregular astigmatism and the spectacle-corrected visual acuity. Conclusions Corneal surface configuration after PK appears to be stable by approximately 6 months after PK, concurrent with postkeratoplasty stabilization of visual acuity.