Cornea

Wirostko B, Rafii MJ, Sullivan DA, Morelli J, Ding J. Novel Therapy to Treat Corneal Epithelial Defects: A Hypothesis with Growth Hormone. Ocul Surf 2015;13(3):204-212.e1.Abstract

Impaired corneal wound healing that occurs with ocular surface disease, trauma, systemic disease, or surgical intervention can lead to persistent corneal epithelial defects (PCED), which result in corneal scarring, ulceration, opacification, corneal neovascularization, and, ultimately, visual compromise and vision loss. The current standard of care can include lubricants, ointments, bandage lenses, amniotic membranes, autologous serum eye drops, and corneal transplants. Various inherent problems exist with application and administration of these treatments, which often may not result in a completely healed surface. A topically applicable compound capable of promoting corneal epithelial cell proliferation and/or migration would be ideal to accelerate healing. We hypothesize that human growth hormone (HGH) is such a compound. In a recent study, HGH was shown to activate signal transducer and activators of transcription-5 (STAT5) signaling and promote corneal wound healing by enhancing corneal epithelial migration in a co-culture system of corneal epithelial cells and fibroblasts. These effects require an intact communication between corneal epithelia and fibroblasts. Further, HGH promotes corneal wound healing in a rabbit debridement model, thus demonstrating the effectiveness of HGH in vivo as well. In conclusion, HGH may represent an exciting and effective topical therapeutic to promote corneal wound healing.

Qazi Y, Kheirkhah A, Blackie C, Cruzat A, Trinidad M, Williams C, Korb DR, Hamrah P. In vivo detection of clinically non-apparent ocular surface inflammation in patients with meibomian gland dysfunction-associated refractory dry eye symptoms: a pilot study. Eye (Lond) 2015;29(8):1099-110.Abstract

PurposeThe utility of in vivo confocal microscopy (IVCM) in the investigation of palpebral conjunctival and corneal inflammation in patients with meibomian gland dysfunction (MGD)-associated refractory dry eye symptoms following gland expression, despite objective clinical improvement.MethodsA retrospective, observational pilot study was conducted evaluating five patients with MGD-associated refractory dry eye symptoms and three control groups: symptomatic untreated MGD patients (n=3), treatment-responsive MGD patients with improved symptoms (n=3) and asymptomatic healthy normals (n=11). Ocular surface disease index (OSDI) scores, tear break-up time (TBUT), the number of meibomian glands yielding liquid secretion (MGYLS), palpebral conjunctival epithelial and substantia propria immune cell (EIC, SIC), and corneal dendritic cell (DC) densities were measured.ResultsDespite clinical improvement (TBUT: 6.4±1.2 s to 10.1±2.1 s, P=0.03; MGYLS: 3.5±0.8 glands to 7.0±1.1 glands, P=0.13) and a normal clinical examination post treatment, MGD patients remained symptomatic. IVCM revealed increased immune cells in the palpebral conjunctiva (refractory MGD EIC=592.6±110.1 cells/mm(2); untreated MGD EIC=522.6±104.7 cells/mm(2), P=0.69; responsive MGD EIC=194.9±119.4 cells/mm(2), P<0.01; normals EIC=123.7±19.2 cells/mm(2), P< 0.001), but not the cornea (refractory MGD DC=60.9±28.3 cells/mm(2); normals DC=25.9±6.3 cells/mm(2); P=0.43). EIC did not correlate with TBUT (Rs=-0.26, P=0.33). OSDI scores correlated with both EIC (Rs=0.76, P<0.001) and TBUT (Rs=-0.69, P<0.01) but not SIC. Intraglandular immune cells were also seen.ConclusionMGD-associated refractory symptoms and the symptom-sign disparity may be explained by clinically non-apparent, active inflammation of the palpebral conjunctiva as detected by IVCM. These patients may benefit from anti-inflammatory therapy.

Kruh JN, Kruh-Garcia NA, Foster SC. Evaluation of the Effect of N-Acetylcysteine on Protein Deposition on Contact Lenses in Patients with the Boston Keratoprosthesis Type I. J Ocul Pharmacol Ther 2015;31(6):314-22.Abstract

PURPOSE: To establish the efficacy of topical N-acetylcysteine (NAC) as a treatment to reduce protein deposition on the contact lens surface. METHODS: In this prospective, nonrandomized clinical trial, a total of 10 eyes (9 patients) were enrolled from a single center. All patients had a prior ocular history of either a Boston Keratoprosthesis type I or trichiasis from Stevens-Johnson syndrome, which necessitated full-time contact lens wear. Four visits were required to complete the study. During visit 1, a new contact lens was inserted and a baseline examination was performed. Visit 2 served as the control month, whereas visits 3 and 4 were month 1 and 2 on treatment with 20% NAC. At the end of each visit the contact lens was replaced. The lenses from visit 2 (control month-without NAC) and from visit 3 (treatment month-with NAC) were collected for proteomic analysis. The main outcome measures were to quantify protein deposition, as well as to assess the visual acuity and ocular surface symptoms before and after treatment. RESULTS: Topical NAC resulted in a 20% decrease in protein deposition. This correlated with a trend for improvement in visual acuity and increased subjective improvement in vision at month 1 (P=0.0153) and 2 (P=0.0016). CONCLUSIONS: NAC reduced protein deposition, decreased ocular surface symptoms, and improved contact lens transparency, thereby providing increased optical clarity.

McAlvin JB, Zhan C, Dohlman JC, Kolovou PE, Salvador-Culla B, Kohane DS. Corneal Anesthesia With Site 1 Sodium Channel Blockers and Dexmedetomidine. Invest Ophthalmol Vis Sci 2015;56(6):3820-6.Abstract

PURPOSE: Amino-amide or amino-ester local anesthetics, which are currently used for topical ocular anesthesia, are short acting and may delay corneal healing with long-term use. In contrast, site 1 sodium channel blockers (S1SCBs) are potent local anesthetics with minimal adverse tissue reaction. In this study, we examined topical local anesthesia with two S1SCBs, tetrodotoxin (TTX) or saxitoxin (STX) individually or in combination with α2-adrenergic receptor agonists (dexmedetomidine or clonidine), and compared them with the amino-ester ocular anesthetic proparacaine. The effect of test solutions on corneal healing was also studied. METHODS: Solutions of TTX ± dexmedetomidine, TTX ± clonidine, STX ± dexmedetomidine, dexmedetomidine, or proparacaine were applied to the rat cornea. Tactile sensitivity was measured by recording the blink response to probing of the cornea with a Cochet-Bonnet esthesiometer. The duration of corneal anesthesia was calculated. Cytotoxicity from anesthetic solutions was measured in vitro. The effect on corneal healing was measured in vivo after corneal debridement followed by repeated drug administration. RESULTS: Addition of dexmedetomidine to TTX or STX significantly prolonged corneal anesthesia beyond that of either drug alone, whereas clonidine did not. Tetrodotoxin or STX coadministered with dexmedetomidine resulted in two to three times longer corneal anesthesia than did proparacaine. S1SCB-dexmedetomidine formulations were not cytotoxic. Corneal healing was not delayed significantly by any of the test solutions. CONCLUSIONS: Coadministration of S1SCBs with dexmedetomidine provided prolonged corneal anesthesia without delaying corneal wound healing. Such formulations may be useful for the management of acute surgical and nonsurgical corneal pain.

Rajaiya J, Zhou X, Barequet I, Gilmore MS, Chodosh J. Novel model of innate immunity in corneal infection. In Vitro Cell Dev Biol Anim 2015;Abstract

The cornea functions as the major refractive interface for vision and protects the internal eye from insult. Current understanding of innate immune responses to corneal infection derives from a synthesis of in vitro and in vivo analyses. However, monolayer cell cultures and mouse models do not accurately duplicate all aspects of innate immunity in human patients. Here, we describe a three-dimensional culture system that incorporates human cells and extracellular matrix to more completely simulate the human cornea for studies of infection. Human corneal stromal fibroblasts were mixed with type I collagen in 3-μm pore size transwell inserts, and overlayed with Matrigel to simulate a human corneal stroma and epithelial basement membrane. These were then infected with a cornea-tropic adenovirus, and exposed on their inferior side to leukocytes derived from human peripheral blood. Subsequent analyses were performed with histology, confocal microscopy, ELISA, and fluorescence-activated cell sorting (FACS). CXCL8, a neutrophil chemokine shown previously as the first cytokine induced in infection of human corneal cells, increased upon adenovirus infection of facsimiles in a dose-responsive fashion. Myeloperoxidase-positive cells infiltrated infected corneal facsimiles in a sub-Matrigel location, possibly due to CXCL8 colocalization with heparan sulfate, a Matrigel constituent. Cellular infiltration was significantly inhibited by treatment with chemical inhibitors of p38 MAPK and Src kinase, both constituents of a signaling cascade previously suggested to regulate inflammation after adenovirus infection. FACS analysis determined that both virus and corneal fibroblasts were necessary for the induction of leukocyte migration into the facsimiles. The corneal facsimile, literally a cornea in a test tube, permits mechanistic studies on human tissue in a highly tractable system.

Lee H-S, Hos D, Blanco T, Bock F, Reyes NJ, Mathew R, Cursiefen C, Dana R, Saban DR. Involvement of corneal lymphangiogenesis in a mouse model of allergic eye disease. Invest Ophthalmol Vis Sci 2015;56(5):3140-8.Abstract

PURPOSE: The contribution of lymphangiogenesis (LA) to allergy has received considerable attention and therapeutic inhibition of this process via targeting VEGF has been considered. Likewise, certain inflammatory settings affecting the ocular mucosa can trigger pathogenic LA in the naturally avascular cornea. Chronic inflammation in allergic eye disease (AED) impacts the conjunctiva and cornea, leading to sight threatening conditions. However, whether corneal LA is involved is completely unknown. We addressed this using a validated mouse model of AED. METHODS: Allergic eye disease was induced by ovalbumin (OVA) immunization and chronic OVA exposure. Confocal microscopy of LYVE-1-stained cornea allowed evaluation of corneal LA, and qRT-PCR was used to evaluate expression of VEGF-C, -D, and -R3 in these mice. Administration of VEGF receptor (R) inhibitor was incorporated to inhibit corneal LA in AED. Immune responses were evaluated by in vitro OVA recall responses of T cells, and IgE levels in the serum. RESULTS: Confocal microscopy of LYVE-1-stained cornea revealed the distinct presence of corneal LA in AED, and corroborated by increased corneal expression of VEGF-C, -D, and -R3. Importantly, prevention of corneal LA in AED via VEGFR inhibition was associated with decreased T helper two responses and IgE production. Furthermore, VEGFR inhibition led a significant reduction in clinical signs of AED. CONCLUSIONS: Collectively, these data reveal that there is a distinct involvement of corneal LA in AED. Furthermore, VEGFR inhibition prevents corneal LA and consequent immune responses in AED.

Chauhan SK, Lee HK, Lee HS, Park EY, Jeong E, Dana R. PTK7+ Mononuclear Cells Express VEGFR2 and Contribute to Vascular Stabilization by Upregulating Angiopoietin-1. Arterioscler Thromb Vasc Biol 2015;35(7):1606-15.Abstract

OBJECTIVE: In angiogenesis, circulating mononuclear cells are recruited to vascular lesions; however, the underlying mechanisms are poorly understood. APPROACH AND RESULTS: Here, we characterize the functional role of protein tyrosine kinase 7 (PTK7)-expressing CD11b(+) mononuclear cells in vitro and in vivo using a mouse model of angiogenesis. Although the frequencies of PTK7(+)CD11b(+) cells in the bone marrow remained similar after vascular endothelial growth factor-A-induced neovascularization, we observed an 11-fold increase in the cornea. Importantly, vascular endothelial growth factor-A-induced chemotaxis of PTK7(+) cells was mediated by vascular endothelial growth factor receptor 2. In a coculture with endothelial cells, PTK7(+)CD11b(+) cells stabilized the vascular network for 2 weeks by expressing high levels of angiopoietin-1. The enhanced vascular stability was abolished by knockdown of angiopoietin-1 in PTK7(+)CD11b(+) cells and could be restored by angiopoietin-1 treatment. CONCLUSIONS: We conclude that PTK7 expression in perivascular mononuclear cells induces vascular endothelial growth factor receptor 2 and angiopoietin-1 expression and thus contributes to vascular stabilization in angiogenesis.

Robert M-C, Khreim N, Todani A, Melki SA. Anterior chamber gas bubble emergence pattern during femtosecond LASIK-flap creation. Br J Ophthalmol 2015;99(9):1201-5.Abstract

AIM: To characterise the emergence pattern of cavitation bubbles into the anterior chamber (AC) following femtosecond laser-assisted in situ keratomileusis (LASIK)-flap creation METHODS: Retrospective review of patients undergoing femtosecond LASIK surgery at Boston Laser, a private refractive surgery practice in Boston, Massachusetts, between December 2008 and February 2014. Patient charts were reviewed to identify all cases with gas bubble migration into the AC. Surgical videos were examined and the location of bubble entry was recorded separately for right and left eyes. RESULTS: Five thousand one hundred and fifty-eight patients underwent femtosecond LASIK surgery. Air bubble migration into the AC, presumably via the Schlemm's canal and trabecular meshwork, occurred in 1% of cases. Patients with AC bubbles had an average age of 33±8 years with a measured LASIK flap thickness of 96±21 μm. The occurrence of gas bubbles impaired iris registration in 64% of cases. Gas bubbles appeared preferentially in the nasal or inferior quadrants for right (92% of cases) and left (100% of cases) eyes. This bubble emergence pattern is significantly different from that expected with a random distribution (p<0.0001) and did not seem associated with decentration of the femtosecond laser docking system. CONCLUSIONS: The migration of gas bubbles into the AC is a rare occurrence during femtosecond laser flap creation. The preferential emergence of gas bubbles into the nasal and inferior quadrants of the AC may indicate a distinctive anatomy of the nasal Schlemm's canal.

Saboo US, Amparo F, Abud TB, Schaumberg DA, Dana R. Vision-Related Quality of Life in Patients with Ocular Graft-versus-Host Disease. Ophthalmology 2015;122(8):1669-74.Abstract

PURPOSE: To assess the vision-related quality of life (QOL) in a cohort of patients with ocular graft-versus-host disease (GVHD). DESIGN: Prospective study. PARTICIPANTS: Eighty-four patients diagnosed with chronic ocular GVHD. METHODS: We assessed the vision-related QOL with the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). The symptoms of ocular GVHD were assessed using the Ocular Surface Disease Index (OSDI) and Symptom Assessment in Dry Eye (SANDE) questionnaires. MAIN OUTCOME MEASURES: We assessed vision-related QOL with the NEI-VFQ-25 and compared the scores obtained from patients with ocular GVHD with those from a healthy population. In the ocular GVHD population, we also evaluated the associations between the NEI-VFQ-25 and the dry eye symptoms measured by the OSDI and SANDE questionnaires, age, duration of disease, best-corrected visual acuity (BCVA), corneal fluorescein staining (CFS), tear break-up time, and Schirmer test. RESULTS: The mean composite NEI-VFQ-25 score in patients with ocular GVHD was 76.5±17. Compared with healthy subjects, patients with ocular GVHD reported reduced scores on all NEI-VFQ-25 subscales (each P < 0.001) with the exception of color vision (P = 0.11). The NEI-VFQ-25 composite scores significantly correlated with OSDI (R = -0.81, P < 0.001), SANDE (R = -0.56, P < 0.001), CFS (R = -0.36, P = 0.001), and BCVA (R = -0.30, P = 0.004). CONCLUSIONS: Patients with ocular GVHD experience measurable impairment of vision-related QOL. This study highlights the impact of ocular GVHD on the vision-related QOL, and thus the importance of comprehensive diagnosis and treatment of this condition.

Hong J, Yu Z, Jiang C, Zhou X, Liu Z, Sun X, Xu J. Corvis ST Tonometer for Measuring Postoperative IOP in LASIK Patients. Optom Vis Sci 2015;92(5):589-95.Abstract

PURPOSE: To compare the postoperative measurements of intraocular pressure (IOP) using the Corvis ST Tonometer (CST), ocular response analyzer (ORA), and Goldmann applanation tonometry (GAT) in eyes undergoing laser in situ keratomileusis (LASIK), as well as to analyze the relationship between the corneal biomechanical parameters of the CST and the ORA. METHODS: Fifty participants who had undergone LASIK to treat myopia in the previous 3 months were enrolled. Postoperative IOP measurements of these participants were obtained using the CST, ORA (corneal-compensated IOP [IOPcc], Goldmann-correlated IOP [IOPg]), and GAT. Device agreement was calculated by Bland-Altman analysis. The metrics of corneal biomechanical properties were recorded using the ORA and the CST. Corneal biomechanical parameters were compared. RESULTS: The Bland-Altman analysis revealed a significant bias between CST and GAT, between CST and IOPcc, and between CST and IOPg of 3.4, 1.0, and 3.8, mm Hg, respectively, with 95% limits of agreement of -0.7 to 7.5 mm Hg, -2.1 to 4.2 mm Hg, and -0.4 to 8.0 mm Hg. The ORA-derived IOP measurements, CST-derived IOP, and GAT IOP values showed good correlation with each other. The CST IOP and IOPcc were higher than the GAT IOP (all p < 0.05), whereas IOPg did not differ from the GAT IOP readings. Ocular response analyzer-derived corneal biomechanical parameters (corneal hysteresis and the corneal resistance factor) showed significant correlations with CST-derived parameters, including the maximum deformation amplitude at the corneal apex and the time from start until the first applanation. CONCLUSIONS: The CST offers an alternative method for measuring postoperative IOP in LASIK patients, and it appears to obtain higher IOP values than other tonometry techniques. The technique may facilitate the investigation of corneal biomechanical property changes in LASIK-treated eyes.

Amparo F, Schaumberg DA, Dana R. Comparison of Two Questionnaires for Dry Eye Symptom Assessment: The Ocular Surface Disease Index and the Symptom Assessment in Dry Eye. Ophthalmology 2015;122(7):1498-503.Abstract

PURPOSE: The aim of this study was to compare patient-reported symptoms of dry eye disease (DED) as assessed by the Ocular Surface Disease Index (OSDI), a 12-item symptom frequency-based questionnaire, and the Symptom Assessment iN Dry Eye (SANDE), a 2-item frequency- and severity-based visual analog scale. DESIGN: Clinic-based evaluation of a diagnostic test. PARTICIPANTS: A total of 114 patients with DED. METHODS: Patients were administered the OSDI and SANDE questionnaires at baseline and follow-up visits to evaluate DED-related symptoms. The correlations between both questionnaires' scores were evaluated using the Spearman coefficient, and their clinical differences were assessed using Bland-Altman analysis. MAIN OUTCOME MEASURES: Baseline and follow-up visit OSDI and SANDE dry eye symptom scores. RESULTS: At the baseline visit, the OSDI and SANDE questionnaire scores were significantly correlated (R = 0.64; P < 0.001). Moreover, a significant correlation was found between changes in the OSDI and SANDE scores from baseline to follow-up visits (R = 0.47; P < 0.001). A Bland-Altman analysis, after score normalization, revealed a difference (bias) of less than 2 centesimal units between the scores of the 2 questionnaires. CONCLUSIONS: Data collected from the SANDE questionnaire showed a significant correlation and negligible score differences with those from the OSDI, suggesting that the SANDE visual analog scale-based questionnaire has the potential to provide clinicians with a short, quick, and reliable measure for DED symptoms.

Boynton GE, Raoof D, Niziol LM, Hussain M, Mian SI. Prospective Randomized Trial Comparing Efficacy of Topical Loteprednol Etabonate 0.5% Versus Cyclosporine-A 0.05% for Treatment of Dry Eye Syndrome Following Hematopoietic Stem Cell Transplantation. Cornea 2015;34(7):725-32.Abstract

PURPOSE: To evaluate the safety and efficacy of topical loteprednol etabonate (LE) 0.5% compared with cyclosporine A (CsA) 0.05% for the prophylaxis and treatment of dry eye syndrome (DES) after hematopoietic stem cell transplantation (HSCT). METHODS: Seventy-five patients were randomized to LE (n = 76 eyes of 38 patients) or CsA (n = 74 eyes of 37 patients) pre-HSCT. Lissamine green and fluorescein staining, tear break-up time, tear osmolarity (Osm), Schirmer score (Sch), intraocular pressure, visual acuity, and Ocular Surface Disease Index were assessed pre-HSCT, 3, 6, 9, and 12 months post-HSCT. RESULTS: There were no differences in DES incidence (P = 0.22; log-rank test) or progression (P = 0.41; log-rank test) between the 2 treatment arms during the course of the study. Among eyes with no DES at enrollment, the Kaplan-Meier analysis yielded a 90% rate of DES development in cyclosporine-treated eyes and a 79% rate of DES development in LE-treated eyes by 12 months post-HSCT. The Kaplan-Meier analysis of eyes with DES at enrollment demonstrated a 38% rate of disease progression among cyclosporine-treated eyes and a 26% rate of disease progression among loteprednol-treated eyes by 12 months. No patient in either group had an elevation of 10 mm Hg or greater from baseline at any study visit, and no patients had their treatment discontinued for elevation in intraocular pressure. CONCLUSIONS: Pre-HSCT initiation of LE 0.5% appears to be safe and may be as effective as CsA 0.5% for the treatment and prophylaxis of DES following HSCT.

Dohlman TH, Omoto M, Hua J, Stevenson W, Lee S-M, Chauhan SK, Dana R. VEGF-trap Aflibercept Significantly Improves Long-term Graft Survival in High-risk Corneal Transplantation. Transplantation 2015;99(4):678-86.Abstract

BACKGROUND: Graft failure because of immune rejection remains a significant problem in organ transplantation, and lymphatic and blood vessels are important components of the afferent and efferent arms of the host alloimmune response, respectively. We compare the effect of antihemangiogenic and antilymphangiogenic therapies on alloimmunity and graft survival in a murine model of high-risk corneal transplantation. METHODS: Orthotopic corneal transplantation was performed in hemevascularized and lymph-vascularized high-risk host beds, and graft recipients received subconjunctival vascular endothelial growth factor (VEGF)-trap, anti-VEGF-C, sVEGFR-3, or no treatment, beginning at the time of surgery. Fourteen days after transplantation, graft hemeangiogenesis and lymphangiogenesis were evaluated by immunohistochemistry. The frequencies of Th1 cells in regional lymphoid tissue and graft-infiltrating immune cells were evaluated by flow cytometry. Long-term allograft survival was compared using Kaplan-Meier curves. RESULTS: VEGF-trap significantly decreased graft hemangiogenesis as compared to the control group and was most effective in reducing the frequency of graft-infiltrating immune cells. Anti-VEGF-C and sVEGFR3 significantly decreased graft lymphangiogenesis and lymphoid Th1 cell frequencies as compared to control. VEGF-trap (72%), anti-VEGF-C (25%), and sVEGFR-3 (11%) all significantly improved in the 8-week graft survival compared to control (0%), although VEGF-trap was significantly more effective than both anti-VEGF-C (P < 0.05) and sVEGFR-3 (P < 0.05). CONCLUSION: In a clinically relevant model of high-risk corneal transplantation in which blood and lymphatic vessels are present and treatment begins at the time of transplantation, VEGF-trap is significantly more effective in improving long-term graft survival as compared to anti-VEGF-C and sVEGFR-3, but all approaches improve survival when compared to untreated control.

Kanellopoulos AJ, Asimellis G, Salvador-Culla B, Chodosh J, Ciolino JB. High-irradiance CXL combined with myopic LASIK: flap and residual stroma biomechanical properties studied ex-vivo. Br J Ophthalmol 2015;99(6):870-4.Abstract

BACKGROUND/AIMS: To evaluate ex vivo biomechanical and enzymatic digestion resistance differences between standard myopic laser in-situ keratomileusis (LASIK) compared with LASIK+CXL, in which high-irradiance cross-linking (CXL) is added. METHODS: Eight human donor corneas were subjected to femtosecond-assisted myopic LASIK. Group A (n=4) served as a control group (no CXL). The corneas in LASIK+CXL group B were subjected to concurrent prophylactic high-irradiance CXL (n=4). Saline-diluted (0.10%) riboflavin was instilled on the stroma, subsequently irradiated with UV-A through the repositioned flap. The cornea stroma and flap specimens were separately subjected to transverse biaxial resistance measurements; biomechanical differences were assessed via stress and Young's shear modulus. Subsequently, the specimens were subjected to enzymatic degradation. RESULTS: For the corneal stroma specimen, stress at 10% strain was 128±11 kPa for control group A versus 293±20 kPa for the LASIK+CXL group B (relative difference Δ=+129%, p<0.05). The stress in group B was also increased at 20% strain by +68% (p<0.05). Shear modulus in group B was increased at 10% strain by +79%, and at 20% strain by +48% (both statistically significant, p<0.05). The enzymatic degradation time to dissolution was 157.5±15.0 min in group A versus 186.25±7.5 min in group B (Δ=+18%, p=0.014). For the flaps, both biomechanical, as well as enzymatic degradation tests showed no significant differences. CONCLUSIONS: LASIK+CXL appears to provide significant increase in underlying corneal stromal rigidity, up to +130%. Additionally, there is significant relevant enzymatic digestion resistance confirmatory to the above. LASIK flaps appear unaffected biomechanically by the LASIK+CXL procedure, suggesting effective CXL just under the flap.

Kheirkhah A, Saboo US, Abud TB, Dohlman TH, Arnoldner MA, Hamrah P, Dana R. Reduced Corneal Endothelial Cell Density inPatients With Dry Eye Disease. Am J Ophthalmol 2015;159(6):1022-1026.e2.Abstract

PURPOSE: To evaluate corneal endothelial cell density (ECD) in patients with dry eye disease (DED) compared to an age-matched control group. DESIGN: Cross-sectional, controlled study. METHODS: This study included 90 eyes of 45 patients with moderate to severe DED (aged 53.7 ± 9.8 years) and 30 eyes of 15 normal controls (aged 50.7 ± 9.8 years). All subjects had a complete ophthalmic evaluation including symptom assessment using the Ocular Surface Disease Index (OSDI) and corneal fluorescein staining. In addition, laser scanning in vivo confocal microscopy was performed to measure the density of the following parameters in the central cornea: endothelial cells, subbasal nerves, and subbasal immune dendritic cells. RESULTS: Corneal ECD was significantly lower in the DED group (2595.8 ± 356.1 cells/mm(2)) than in the control group (2812.7 ± 395.2 cells/mm(2), P = .046). The DED group showed significantly lower corneal subbasal nerve density (17.1 ± 6.9 mm/mm(2)) compared to the control group (24.7 ± 4.4 mm/mm(2), P < .001). Dendritic cell density was significantly higher in the DED group than in the controls (111.7 ± 137.3 vs 32.0 ± 24.4 cells/mm(2), respectively, P = .002). There were statistically significant correlations between corneal ECD and dry eye severity parameters including the OSDI score (rs = -0.26, P = .03), and corneal fluorescein staining (rs = -0.28, P = .008). CONCLUSIONS: There is a significant reduction in corneal ECD in DED that correlates with clinical severity of the disease.

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