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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 The success of Descemet stripping only (DSO) is optimized by performing a well-centered, accurately sized diameter of descemetorhexis with a smooth curvilinear border. To achieve this success, we describe a repeatable and relatively straightforward technique to optimize this descemetorhexis for DSO. Methods The "two-flaps" technique uses the Gorovoy DSO forceps. The technique takes advantage of the flat and smooth surface of the forceps to create the desired 4-mm Descemet stripping with minimal stromal trauma along with a continuous curvilinear descemetorhexis, minimizing the risk of postoperative stromal scarring and extension of the rhexis beyond 4 mm. Results This technique has been used successfully in 11 cases performed by 1 surgeon or directly supervised by him. All cases achieved the desired 4-mm circumference without any residual tags or visually significant stromal scarring, with successful clearing of the central cornea and endothelial cells repopulating the central stripped area. Conclusions This technique described provides a consistent, reproducible, and relatively trauma-free peeling of Descemet membrane and associated endothelial cells/guttae to optimize the success of DSO.

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.

PURPOSE To evaluate the morphological features of the corneal limbus as measured by in vivo confocal microscopy (IVCM) following standard and accelerated corneal collagen cross-linking (CXL) for keratoconus. METHODS Patients with progressive keratoconus scheduled to undergo standard CXL (group 1; 31 patients, 3 mW/cm, 370 nm, 30 minutes), or accelerated CXL (group 2; 20 patients, 9 mW/cm, 370 nm, 10 minutes) in the worse eye were included in this prospective study. Thirty eyes of 30 age-matched patients served as controls (group 3). All patient eyes underwent IVCM scanning of the central cornea and the inferior limbal area at baseline and 1, 3, and 6 months after CXL. RESULTS After CXL, epithelial regrowth was complete by day 4 in both groups 1 and 2. There were no statistically significant differences between the baseline mean central corneal wing or basal cell density, limbus-palisade middle or basal cell densities of groups 1, 2, or 3. At postoperative months 1, 3, and 6, there were no statistically significant differences in either central or limbus-palisade epithelial cell densities or diameters in keratoconic eyes that underwent standard or accelerated CXL (P > 0.05). The morphology of the limbal cells was preserved as well. CONCLUSIONS The morphology of limbus structures seems to be preserved following standard and accelerated CXL in short-term follow-up, as measured using IVCM.

Purpose To evaluate and compare corneal and conjunctival biomarkers for immunocytochemical diagnosis of limbal stem cell deficiency (LSCD). Methods In accordance with the current literature, we selected K12 as the corneal biomarker and K7/K13/K19/MUC5AC as the conjunctival ones. The specificity and accuracy for each biomarker were assessed and compared on 10 healthy subjects and tissues of deceased donors. Twelve eyes of 9 patients clinically suspected of LSCD were enrolled. Epithelial cells (ECs) from the central cornea were collected using impression cytology (IC) and assessed for each biomarker. The presence of conjunctival cells in the central cornea was diagnostic proof of LSCD, whereas the detection of corneal residual cells would quantify the degree of LSCD. Results K12 and K7/K13/MUC5AC are, respectively, highly specific of corneal and conjunctival differentiation, whereas K19 is not. Normal corneal ECs are not desquamative enough to be suitable for IC. Among 12 eyes with suspected LSCD, 84% (10 of 12) of IC samples were suitable for analysis. K3/K7/K19 immunostaining was positive in 100%, MUC5AC in 40%, and K12 was never observed. Conclusions Clinical examination can lead to misdiagnosis of LSCD. Immunocytochemical detection of K7/K13 on corneal ECs collected by IC is reproducible, noninvasive, and highly effective in this indication, but without any quantification of the degree of the disease. This time-consuming technique requires skilled technicians and laboratory facilities, reserving it for planned limbal reconstruction.

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.

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.

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.

Corneal refractive surgery results in nerve damage. Nerve regeneration is a complex process that involves nerve growth factor (NGF). Here, a comparative study was conducted to determine the NGF level in the central cornea after laser in situ keratomileusis (LASIK) and epipolis laser in situ keratomileusis (epi-LASIK) treatment.Twenty-four New Zealand white rabbits underwent randomly assigned epi-LASIK treatment on 1 eye and LASIK treatment on the other eye. Experimental animals were sacrificed 1 day, 3 days, 7 days, and 1 month after treatment, and the NGF level was determined by immunohistochemistry and Western blot analyses. Statistical analyses were performed using a Student t test (P0.05).Immunohistochemical staining demonstrated a weak NGF signal in the cornea of control and LASIK-treated rabbit eyes. After epi-LASIK treatment, the level of NGF increased significantly in the epithelial layer at the 1- and 3-day time point, and returned to control levels 7 days after treatment. Western blot analyses showed that the NGF level was significantly lower after LASIK treatment as compared to epi-LASIK treatment, 1 day and 3 days after treatment (t = -6.50, -5.85; P = 0.023, 0.028), with no significant difference between the two groups at the 7-day and 1-month time points (P0.05).This study demonstrates for the first time that the NGF level in the central corneal epithelial layer of rabbit eyes is significantly increased early after epi-LASIK treatment in contrast to LASIK treatment, and decreased to control levels 1 week after treatment.

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].

PURPOSE To present an unusual case in which the honeycomb opacities of Thiel-Behnke corneal dystrophy disappeared during a course of chronic Thygeson superficial punctate keratitis. CASE A 29-year-old woman with a 5-year history of decreased visual acuity in both eyes had bilateral honeycomb-shaped corneal opacities, located mainly in the superficial central cornea. She was diagnosed as having Thiel-Behnke corneal dystrophy, which we confirmed genetically. During follow-up, her left eye was affected by chronic Thygeson superficial punctate keratitis, and the honeycomb opacity in this eye was noted to have disappeared. CONCLUSIONS We observed the dissolution of honeycomb-like corneal opacities in a patient with confirmed Thiel-Behnke corneal dystrophy after the patient subsequently contracted chronic Thygeson superficial punctate keratitis. We surmise that epithelial inflammation associated with Thygeson epithelial keratitis may play a role in dissolving the honeycomb opacities.

Purpose To determine changes in corneal thickness after topical anesthesia. Methods Corneal thickness was measured before and 3 minutes after administration of two drops of oxybuprocaine 0.4% to 26 patients (26 eyes). We analyzed the corneal thickness of a control group, which was made up of 26 patients (26 eyes) before and 3 minutes after administration of two drops of saline solution. Corneal thickness was measured with the Orbscan Topography System II (Bausch Lomb Surg., Barcelona). Results Variations higher than ± 10 μm were found following the instillation of 2 oxybuprocaine eye drops in eight eyes (30.76%) at the inferonasal cornea, in six eyes (23.08%) at the superotemporal, temporal and inferotemporal cornea, in five eyes (19.23%) at the nasal cornea, in three eyes (11.53%) at the central cornea, and in two eyes (7.69%) at the superonasal cornea. Nevertheless, no significant differences in the mean corneal thickness at each corneal location between the first and the second corneal thickness measurements were found in anesthetized eyes. Conclusions Some individuals can present important increases and decreases in corneal thickness values after anesthetic eye drops. This effect of anesthetic eye drops must be considered by refractive surgeons when carrying out preoperative laser in situ keratomileusis corneal thickness measurements.

PURPOSE To report a case with bilateral disciform keratopathy after laser in situ keratomileusis (LASIK). RESULTS A 28-year-old man was referred to us with complaints of progressive painless diminution of vision, 5 days after having undergone bilateral simultaneous LASIK for hyperopia. The surgery was performed on the Chiron Technolas 217 excimer laser machine along with the hansatome, in which previously used blades were installed. Slit-lamp biomicroscopy revealed bilateral translucent disc-shaped lesions in the central cornea of both eyes. The lesions resolved after intense topical steroid therapy over a period of 3 weeks. CONCLUSION Reuse of the microkeratome blade may have been the cause of this complication. The use of a new blade and meticulous cleaning of the microkeratome prior to use in each eye may help to prevent this complication.

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.

The effect on central corneal curvature of radial keratectomy was examined. Ten rabbits had six equally spaced radial wedges removed from the cornea of one eye. Preoperative and serial postoperative keratometry readings were performed to follow the change in refractive power. The follow-up period was 3 months. Radial keratectomy produced an initial steepening of the central cornea, but this effect had disappeared by the end of the follow-up period. It is suggested that this could well have been because the 10/0 prolene sutures pulled through the rabbit cornea, which does not possess a Bowman's membrane.