Morthen MK, Tellefsen S, Richards SM, Lieberman SM, Rahimi Darabad R, Kam WR, Sullivan DA. Testosterone Influence on Gene Expression in Lacrimal Glands of Mouse Models of Sjögren Syndrome. Invest Ophthalmol Vis Sci 2019;60(6):2181-2197.Abstract
Purpose: Sjögren syndrome is an autoimmune disorder that occurs almost exclusively in women and is associated with extensive inflammation in lacrimal tissue, an immune-mediated destruction and/or dysfunction of glandular epithelial cells, and a significant decrease in aqueous tear secretion. We discovered that androgens suppress the inflammation in, and enhance the function of, lacrimal glands in female mouse models (e.g., MRL/MpJ-Tnfrsf6lpr [MRL/lpr]) of Sjögren syndrome. In contrast, others have reported that androgens induce an anomalous immunopathology in lacrimal glands of nonobese diabetic/LtJ (NOD) mice. We tested our hypothesis that these hormone actions reflect unique, strain- and tissue-specific effects, which involve significant changes in the expression of immune-related glandular genes. Methods: Lacrimal glands were obtained from age-matched, adult, female MRL/lpr and NOD mice after treatment with vehicle or testosterone for up to 3 weeks. Tissues were processed for analysis of differentially expressed mRNAs using CodeLink Bioarrays and Affymetrix GeneChips. Data were analyzed with bioinformatics and statistical software. Results: Testosterone significantly influenced the expression of numerous immune-related genes, ontologies, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in lacrimal glands of MRL/lpr and NOD mice. The nature of this hormone-induced immune response was dependent upon the autoimmune strain, and was not duplicated within lacrimal tissues of nonautoimmune BALB/c mice. The majority of immune-response genes regulated by testosterone were of the inflammatory type. Conclusions: Our findings support our hypothesis and indicate a major role for the lacrimal gland microenvironment in mediating androgen effects on immune gene expression.
Shu DY, Hutcheon AEK, Zieske JD, Guo X. Epidermal Growth Factor Stimulates Transforming Growth Factor-Beta Receptor Type II Expression In Corneal Epithelial Cells. Sci Rep 2019;9(1):8079.Abstract
We previously demonstrated that inhibition of epidermal growth factor receptor (EGFR) slowed corneal epithelial migration. Here we examine the effect of EGF on transforming growth factor-beta receptor II (TGF-βRII) in a corneal wound-healing model and primary human corneal epithelial cells (pHCE). Corneal debridement wounds were made and allowed to heal ± Tyrphostin AG1478 (EGFR inhibitor), and assayed for EGFR activation and EGFR and TGF-βRII localization. Primary HCE were treated with EGF ± U0126 (MEK inhibitor) and assayed for TGF-βRII expression. EGFR activation was maximal 15 minutes after wounding and localized in the migrating epithelial cells. TGF-βRII localization was also observed in the migrating epithelium and was reduced when EGFR was blocked. When pHCE were treated with EGF for 6 hours, the cells produced enhanced levels of TGF-βRII, which was blocked by U0126. Downstream signaling pathways of MEK (p38 and ERK1/2) were then examined, and TGF-β1 and EGF were found to have differential effects on the phosphorylation of p38 and ERK1/2, with TGF-β1 upregulating p-p38 but not pERK1/2 and EGF upregulating pERK1/2 but not p-p38. Taken together, these data indicate that EGF stimulates TGF-βRII through ERK1/2 and EGFR signaling, suggesting interplay between EGF- and TGF-β-signaling pathways during corneal wound repair.
Fayed M, Chen TC. Pediatric Intraocular Pressure Measurements: Tonometers, Central Corneal Thickness, and Anesthesia. Surv Ophthalmol 2019;Abstract
Measuring intraocular pressure (IOP) is the cornerstone of a comprehensive glaucoma exam. In babies or small children, however, IOP measurements are problematic, cannot often be done at the slit lamp, and are sometimes require general anesthesia. Therefore, it is essential for an ophthalmologist who examines a pediatric patient to be aware of the different tonometers used in children, as well as the effects of central corneal thickness (CCT) and anesthesia on IOP measurements. Goldmann applanation tonometry is the gold standard for IOP assessment. Most alternative tonometers tend to give higher IOP readings compared to the Goldmann applanation tonometer, and readings between different tonometers are often not interchangeable. Like Goldmann tonometry, many of these alternative tonometers are affected by CCT, with thicker corneas having artifactually high IOP readings and thinner corneas having artifactually lower IOP readings. Although various machines can be used to compensate for corneal factors (e.g. the dynamic contour tonometer and ocular response analyzer), it is important to be aware that certain ocular diseases can be associated with abnormal CCT values and that their IOP readings need to be interpreted accordingly. Because induction and anesthetics can affect IOP, office IOPs taken in awake patients are always the most accurate.
Mölzer C, Shankar SP, Griffith M, Islam MM, Forrester JV, Kuffová L. Activation of dendritic cells by crosslinked collagen hydrogels (artificial corneas) varies with their composition. J Tissue Eng Regen Med 2019;13(9):1528-1543.Abstract
Activated T cells are known to promote fibrosis, a major complication limiting the range of polymeric hydrogels as artificial corneal implants. As T cells are activated by dendritic cells (DC), minimally activating hydrogels would be optimal. In this study, we evaluated the ability of a series of engineered (manufactured/fabricated) and natural collagen matrices to either activate DC or conversely induce DC apoptosis in vitro. Bone marrow DC were cultured on a series of singly and doubly crosslinked hydrogels (made from recombinant human collagen III [RHCIII] or collagen mimetic peptide [CMP]) or on natural collagen-containing matrices, Matrigel and de-cellularised mouse corneal stroma. DC surface expression of major histocompatibility complex Class II and CD86 as well as apoptosis markers were examined. Natural matrices induced low levels of DC activation and maintained a "tolerogenic" phenotype. The same applied to singly crosslinked CMP-PEG gels. RHCIII gels singly crosslinked using either N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide with the coinitiator N-hydroxy succinimide (EDC-NHS) or N-cyclohexyl-N-(2-morpholinoethyl)carbodiimide metho-p-toulenesulfonate with NHS (CMC-NHS) induced varying levels of DC activation. In contrast, however, RHCIII hydrogels incorporating an additional polymeric network of 2-methacryloyloxyethyl phosphorylcholine did not activate DC but instead induced DC apoptosis, a phenomenon observed in natural matrices. This correlated with increased DC expression of leukocyte-associated immunoglobulin-like receptor-1. Despite low immunogenic potential, viable tolerogenic DC migrated into and through both natural and manufactured RHCIII gels. These data show that the immunogenic potential of RHCIII gels varies with the nature and composition of the gel. Preclinical evaluation of hydrogel immunogenic/fibrogenic potential is recommended.
Yazdani M, Chen X, Tashbayev B, Utheim ØA, Ræder S, Hua Y, Eidet JR, Stojanovic A, Dartt DA, Utheim TP. Evaluation of the Ocular Surface Disease Index Questionnaire as a Discriminative Test for Clinical Findings in Dry Eye Disease Patients. Curr Eye Res 2019;44(9):941-947.Abstract
: To investigate to what extent the OSDI can be utilized as a discriminative test for clinical findings. : One thousand and ninety patients with dry eye disease (DED) were consecutively included and examined for osmolarity, tear film break-up time (TFBUT), ocular protection index (OPI), ocular surface staining (OSS), Schirmer I test (ST), meibum expressibility (ME), meibum quality (MQ), and diagnosis of meibomian gland dysfunction (MGD). Receiver-operating characteristic curve (ROC) analysis considering optimum balanced sensitivity and specificity (close to 50%) was used for assessment. : The present study on more than 1,000 patients indicates that the OSDI in the ROC curve analysis is a poor discriminator of pathological scores for TFBUT ≤ 5 (AUC = 0.553; = .012) and ≤10 s (AUC = 0.608; = .002), OSS ≥ 3 (AUC = 0.54; = .043), ST ≤ 5 (AUC = 0.550; = .032) and ≤10 mm/5 min (AUC = 0.544; = .016), and ME ≥ 1 (AUC = 0.594; = <0.001). Pathological scores for osmolarity >308 and >316 mOsm/L, OPI, OSS > 1, MQ, and MGD could not be discriminated by OSDI ( > .05). : Cut-off values for the OSDI can be defined to discriminate pathological TFBUT (≤5 and ≤10), OSS (≥3), ST (≤5 and ≤10) and ME, however, the discriminability was low. Our comprehensive study emphasises the importance of taking both symptoms and signs into account in DED management.
Di Zazzo A, Micera A, Coassin M, Varacalli G, Foulsham W, De Piano M, Bonini S. InflammAging at Ocular Surface: Clinical and Biomolecular Analyses in Healthy Volunteers. Invest Ophthalmol Vis Sci 2019;60(5):1769-1775.Abstract
Purpose: To assess the ocular surface in volunteers who consider themselves as healthy, in order to evaluate how para-inflammatory mechanisms fail with age, and thus investigate the phenomenon of "InflammAging." Methods: In this observational prospective cohort study, volunteers were categorized into three groups according to age: young (19-40 years), middle-aged (41-60 years), and older adults (61-93 years). Clinical assessments included tear breakup time (T-BUT) and Schirmer test type I. Dry eye symptoms were evaluated by the Ocular Surface Disease Index (OSDI) questionnaire. Conjunctival mRNA and protein expression of intercellular adhesion molecule-1 (ICAM-1), MUC5AC, and IL-8 were measured by real-time PCR and immunofluorescence. Results: A total of 82 volunteers (38 males and 44 females) were enrolled. T-BUT decreased significantly with increasing age (young: 11.13 ± 0.18 seconds; middle-aged: 10.83 ± 0.56 seconds; older: 9.00 ± 1.00 seconds, P < 0.05). Schirmer test values decreased significantly with age (young: 20.6 ± 1.0 mm; middle-aged: 19.2 ± 1.2 mm; older: 16.0 ± 1.1 mm, P < 0.05). OSDI scores increased with age in both groups, but they were substantially higher in women. Conjunctival expression of inflammatory markers ICAM-1, IL-8, and MUC5AC increased with age. Conclusions: Clinical signs, symptoms, and biomarkers of chronic inflammation increased with age in a cohort of volunteers who considered themselves healthy, indicating an age-related progressive impairment of ocular surface system function.
Hutcheon AEK, Zieske JD, Guo X. 3D in vitro model for human corneal endothelial cell maturation. Exp Eye Res 2019;184:183-191.Abstract
Corneal endothelium is a cellular monolayer positioned on the Descemet's membrane at the anterior cornea, and it plays a critical role in maintaining corneal clarity. Our present study examines the feasibility of utilizing our 3-dimensional (3D) corneal stromal construct, which consists of human corneal fibroblasts (HCF) and their self-assembled matrix, to observe the development and maturation of human corneal endothelial cells (HCEndoCs) in a co-culture model. Three-dimensional HCF constructs were created by growing the HCFs on Transwell membranes in Eagles' minimum essential medium (EMEM) + 10% FBS + 0.5 mM Vitamin C (VitC) for about 4 weeks. HCEndoCs, either primary (pHCEndoC) or cell line (HCEndoCL), were either seeded in chamber slides, directly on the Transwell membranes, or on the 3D HCF constructs and cultivated for 5 days or 2 weeks. The HCEndoCs that were seeded directly on the Transwell membranes were exposed indirectly to HCF by culturing the HCF on the plate beneath the membrane. Cultures were examined for morphology and ultrastructure using light and transmission electron microscopy (TEM). In addition, indirect-immunofluorescence microscopy (IF) was used to examine tight junction formation (ZO-1), maturation (ALDH1A1), basement membrane formation (Laminin), cell proliferation (Ki67), cell death (caspase-3), and fibrotic response (CTGF). As expected, both pHCEndoCs and HCEndoCLs formed monolayers on the constructs; however, the morphology of the HCEndoCLs appeared to be similar to that seen in vivo, uniform and closely packed, whereas the pHCEndoCs remained elongated. The IF data showed that laminin localization was present in the HCEndoCs' cytoplasm as cell-cell contact increased, and when they were grown in the 3D co-culture, the beginnings of what appears to be a continuous DM-like structure was observed. In addition, in co-cultures, ALDH1A1-positive HCEndoCs were present, ZO-1 expression localized within the tight junctions, minimal numbers of HCEndoCs were Ki67-or Caspase-3-positive, and CTGF was positive in both the HCEndoCs cytoplasm and the matrix of the co-culture. Also, laminin localization was stimulated in HCEndoCs upon indirect stimuli secreted by HCF. The present data suggests our 3D co-culture model is useful for studying corneal endothelium maturation in vitro since the co-culture promotes new DM-like formation, HCEndoCs develop in vivo-like characteristics, and the fibrotic response is activated. Our current findings are applicable to understanding the implications of corneal endothelial injection therapy, such as if the abnormal DM has to be removed from the patient, the newly injected endothelial cells will seed onto the wound area and deposit a new DM-like membrane. However, caution should be observed and as much of the normal DM should be left intact since removal of the DM can cause a posterior stromal fibrotic response.
Botten N, Hodges RR, Li D, Bair JA, Shatos MA, Utheim TP, Serhan CN, Dartt DA. Resolvin D2 elevates cAMP to increase intracellular [Ca] and stimulate secretion from conjunctival goblet cells. FASEB J 2019;33(7):8468-8478.Abstract
Under physiologic conditions, conjunctival goblet cells (CGCs) secrete mucins into the tear film to preserve ocular surface homeostasis. Specialized proresolving mediators (SPMs), like resolvins (Rvs), regulate secretion from CGCs and actively terminate inflammation. The purpose of this study was to determine if RvD2 stimulated mucin secretion and to investigate the cellular signaling components. Goblet cells were cultured from rat conjunctiva. Secretion was measured by an enzyme-linked lectin assay, change in intracellular [Ca] ([Ca]) using Fura-2, and cellular cAMP levels by ELISA. RvD2 (10-10 M) stimulated secretion, increased cellular cAMP levels and the [Ca]. RvD2-stimulated increase in [Ca] and secretion was blocked by Ca chelator 1,2-bis(2-aminophenoxy)ethane-,,','-tetraacetic acid tetrakis and the PKA inhibitor -[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride but not by the cAMP exchange protein inhibitor α-[2-(3-chlorophenyl)hydrazinylidene]-5-(1,1-dimethylethyl)-b-oxo-3-isoxazolepropanenitrile. Forskolin, 3-isobutyl-1-methylxanthine, and 8-bromo-cAMP (8-Br-cAMP) increased [Ca]. Increasing cAMP with 8-Br-cAMP inhibited the increase in [Ca] stimulated by the cAMP-independent agonist cholinergic agonist carbachol. In conclusion, RvD2 uses both cellular cAMP and [Ca] to stimulate glycoconjugate secretion from CGCs, but the interaction of cAMP and [Ca] is context dependent. Thus RvD2 likely assists in the maintenance of the mucous layer of the tear film to sustain ocular surface homeostasis and has potential as a novel treatment for dry eye disease.-Botten, N., Hodges, R. R., Li, D., Bair, J. A., Shatos, M. A., Utheim, T. P., Serhan, C. N., Dartt, D. A. Resolvin D2 elevates cAMP to increase intracellular [Ca] and stimulate secretion from conjunctival goblet cells.
Marmalidou A, Palioura S, Dana R, Kheirkhah A. Medical and surgical management of conjunctivochalasis. Ocul Surf 2019;Abstract
Conjunctivochalasis (CCH) is a bilateral conjunctival condition characterized by loose, redundant conjunctival folds, typically in the inferior bulbar conjunctiva. It is a common cause of ocular irritation, especially in older age. For asymptomatic CCH, no treatment is necessary. For treatment of symptomatic CCH, however, a variety of medical and surgical approaches are currently available, which will be thoroughly appraised in this review article. The first step in the management is medical therapy, which involves enhanced lubrication and use of anti-inflammatory medications. In refractory cases, a surgical approach may be undertaken for symptom relief. Several techniques have been described for this, with varying success rates. These include conjunctival cauterization, conjunctival excision, scleral fixation of the conjunctiva, conjunctival ligation, laser conjunctivoplasty, and radiowave electrosurgery. Among these, conjunctival cauterization and excision of the redundant conjunctiva, with or without tissue grafting, have gained popularity.
Deiner MS, McLeod SD, Wong J, Chodosh J, Lietman TM, Porco TC. Google Searches and Detection of Conjunctivitis Epidemics Worldwide. Ophthalmology 2019;126(9):1219-1229.Abstract
PURPOSE: Epidemic and seasonal infectious conjunctivitis outbreaks can impact education, workforce, and economy adversely. Yet conjunctivitis typically is not a reportable disease, potentially delaying mitigating intervention. Our study objective was to determine if conjunctivitis epidemics could be identified using Google Trends search data. DESIGN: Search data for conjunctivitis-related and control search terms from 5 years and countries worldwide were obtained. Country and term were masked. Temporal scan statistics were applied to identify candidate epidemics. Candidates then were assessed for geotemporal concordance with an a priori defined collection of known reported conjunctivitis outbreaks, as a measure of sensitivity. PARTICIPANTS: Populations by country that searched Google's search engine using our study terms. MAIN OUTCOME MEASURES: Percent of known conjunctivitis outbreaks also found in the same country and period by our candidate epidemics, identified from conjunctivitis-related searches. RESULTS: We identified 135 candidate conjunctivitis epidemic periods from 77 countries. Compared with our a priori defined collection of known reported outbreaks, candidate conjunctivitis epidemics identified 18 of 26 (69% sensitivity) of the reported country-wide or island nationwide outbreaks, or both; 9 of 20 (45% sensitivity) of the reported region or district-wide outbreaks, or both; but far fewer nosocomial and reported smaller outbreaks. Similar overall and individual sensitivity, as well as specificity, were found on a country-level basis. We also found that 83% of our candidate epidemics had start dates before (of those, 20% were more than 12 weeks before) their concurrent reported outbreak's report issuance date. Permutation tests provided evidence that on average, conjunctivitis candidate epidemics occurred geotemporally closer to outbreak reports than chance alone suggests (P < 0.001) unlike control term candidates (P = 0.40). CONCLUSIONS: Conjunctivitis outbreaks can be detected using temporal scan analysis of Google search data alone, with more than 80% detected before an outbreak report's issuance date, some as early as the reported outbreak's start date. Future approaches using data from smaller regions, social media, and more search terms may improve sensitivity further and cross-validate detected candidates, allowing identification of candidate conjunctivitis epidemics from Internet search data potentially to complementarily benefit traditional reporting and detection systems to improve epidemic awareness.
Garza-Leon M, Amparo F, Ortíz G, de la Parra-Colin P, Sanchez-Huerta V, Beltran F, Hernandez-Quintela E. Translation and validation of the contact lens dry eye questionnaire-8 (CLDEQ-8) to the Spanish language. Cont Lens Anterior Eye 2019;42(2):155-158.Abstract
PURPOSE: To present the process of cultural and psychometric adaptation, and clinical validation of a new version in the Spanish language of the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8). MATERIALS AND METHODS: The translation-retro-translation method was applied to the CLDEQ-8 questionnaire. Two independent native Spanish-speaking translators adapted the questionnaire from English to Spanish, and then a committee of experienced clinicians (CE) evaluated the semantic equivalence and designed a Spanish version of the CLDEQ-8 questionnaire. The resulting translated version was tested conducting a pilot study in contact lens users and assessing their perception and overall understanding of the terminology. The results were analyzed and a final version was designed. The final version was retro-translated to English by a native English-speaking translator and compared with the original CLDEQ-8 version to confirm there were no meaningful differences. To clinically validate the new instrument, a prospective study was conducted to apply the new Spanish CLDEQ-8 to 50 contact lens users. RESULTS: Fifty patients were studied with an average age of 21.50 ± 1.66 years. The average CLDEQ-8 score was 13.28 ± 6.81 points (range 1-31). The internal consistency (Cronbach's alpha) was 0.89, with a corrected index of homogeneity >0.50 for all evaluated items. CONCLUSIONS: The process of trans-cultural adaptation of the questionnaire CLDEQ-8 resulted in the elaboration of a reliable and much needed instrument capable of measuring frequency and intensity of dry eye symptoms in Spanish-speaking contact lens users.
Coco G, Amparo F, Patel SP, Foulsham W, Carreno-Galeano JT, Stockslager SG, Ciolino JB, Yin J, Dana R. Oral guaifenesin for treatment of filamentary keratitis: A pilot study. Ocul Surf 2019;Abstract
PURPOSE: Pilot study to evaluate the safety and efficacy of oral guaifenesin in reducing the signs and symptoms of filamentary keratitis. METHODS: Prospective, uncontrolled open-label pilot study. Twelve patients with non-Sjögren dry eye disease (DED) and secondary filamentary keratitis received treatment with oral guaifenesin 600 mg twice a day (total dose of 1.2 g/day) for 4 weeks. Adverse events, change in the number of corneal filaments, corneal fluorescein staining (CFS; NEI grading system), and symptoms (Ocular Surface Disease Index) were assessed. RESULTS: Before starting oral guaifenesin, all patients were on topical medical therapy for their condition. At baseline, the mean number of filaments was 5.8 ± 2.9, CFS score 7.3 ± 3.2, and OSDI score 55.6 ± 25. After 4 weeks of treatment, the number of filaments was 2.1 ± 2.2 (p = 0.04 vs. baseline), CFS score 6.5 ± 3.1 (p = 0.5), and OSDI score 46.1 ± 30.9 (p = 0.2). One patient discontinued the medication due to gastrointestinal side effects. CONCLUSIONS: Oral guaifenesin was safe and generally well tolerated, and demonstrated modest efficacy in reducing the severity of filamentary keratitis. These results should be considered preliminary; however, placebo-controlled investigations would be justified to evaluate the therapeutic efficacy of oral guaifenesin as a mucolytic in treatment of filamentary keratitis.
Shanbhag SS, Chodosh J, Saeed HN. Sutureless amniotic membrane transplantation with cyanoacrylate glue for acute Stevens-Johnson syndrome/toxic epidermal necrolysis. Ocul Surf 2019;Abstract
Amniotic membrane (AM) transplantation, when performed in the acute phase in Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) for patients with ocular complications, is known to reduce the morbidity of ocular complications in the chronic phase. In conditions such as SJS/TEN, AM needs to be secured to the ocular surface as well as the eyelids. Previously, techniques of securing a large sheet of AM with fibrin glue to the ocular surface and with sutures and bolsters to the eyelids have been described in the acute phase of SJS/TEN. These techniques often necessitate the use of an operating room in acutely ill patients. We describe a bedside technique that uses cyanoacrylate glue to secure the AM to the eyelids, as well as long-term outcomes in 4 patients with acute SJS/TEN. The combination of a custom symblepharon ring to secure AM over the entire ocular surface and cyanoacrylate glue to secure AM to the eyelid margins is quick, painless, does not require local or general anesthesia, and might prove useful in other conditions previously shown to benefit from AMT, such as ocular chemical injuries.
Utheim OA, Pasovic L, Raeder S, Eidet JR, Fostad IG, Sehic A, Roald B, de la Paz MF, Lyberg T, Dartt DA, Utheim TP. Effects of explant size on epithelial outgrowth, thickness, stratification, ultrastructure and phenotype of cultured limbal epithelial cells. PLoS One 2019;14(3):e0212524.Abstract
PURPOSE: Transplantation of limbal stem cells is a promising therapy for limbal stem cell deficiency. Limbal cells can be harvested from either a healthy part of the patient's eye or the eye of a donor. Small explants are less likely to inflict injury to the donor site. We investigated the effects of limbal explant size on multiple characteristics known to be important for transplant function. METHODS: Human limbal epithelial cells were expanded from large versus small explants (3 versus 1 mm of the corneal circumference) for 3 weeks and characterized by light microscopy, immunohistochemistry, and transmission electron microscopy. Epithelial thickness, stratification, outgrowth, ultrastructure and phenotype were assessed. RESULTS: Epithelial thickness and stratification were similar between the groups. Outgrowth size correlated positively with explant size (r = 0.37; P = 0.01), whereas fold growth correlated negatively with explant size (r = -0.55; P < 0.0001). Percentage of cells expressing the limbal epithelial cell marker K19 was higher in cells derived from large explants (99.1±1.2%) compared to cells derived from small explants (93.2±13.6%, P = 0.024). The percentage of cells expressing ABCG2, integrin β1, p63, and p63α that are markers suggestive of an immature phenotype; Keratin 3, Connexin 43, and E-Cadherin that are markers of differentiation; and Ki67 and PCNA that indicate cell proliferation were equal in both groups. Desmosome and hemidesmosome densities were equal between the groups. CONCLUSION: For donor- and culture conditions used in the present study, large explants are preferable to small in terms of outgrowth area. As regards limbal epithelial cell thickness, stratification, mechanical strength, and the attainment of a predominantly immature phenotype, both large and small explants are sufficient.