Charles N.J. McGhee

An Immunohistochemical Study of Inflammatory Cell Changes and Matrix Remodeling With and Without Acute Hydrops in Keratoconus.

PURPOSE To determine the inflammatory cell and matrix changes in advanced keratoconus, including acute hydrops, using immunohistochemical analysis. METHODS The corneal tissue from eight subjects with keratoconus undergoing corneal transplantation (three keratoconic buttons, five buttons post acute hydrops—one of them with extensive neovascularization following hydrops) was compared with tissue from two normal corneoscleral rims (n = 10). The corneas were sectioned and analyzed with specific markers for macrophages, lymphocytes, dendritic cells, and scar associated matrix molecules laminin, fibronectin, tenascin-C, and type III collagen. RESULTS Populations of cells using markers for macrophages, leucocytes and antigen presenting cells were found to be associated with the epithelium and stroma of keratoconic tissue. Populations of these cells appeared decreased in hydrops-associated keratoconus except for a large increase in leucocytes in the stroma and endothelium associated with neovascularization. Extracellular matrix deposition was found to be uniquely demonstrated in localized areas of the stroma, corresponding to the site of hydrops involvement. CONCLUSIONS Immunohistochemical analysis revealed a chronic, inflammatory process with recruitment of immunoinflammatory cells and deposition of scar tissue in keratoconus. The inflammatory markers were somewhat attenuated in hydrops-associated keratoconus corneas and thus inflammation was not considered to be a major factor in the development of acute corneal hydrops.

Identifying relationships between tomography-derived corneal thickness, curvature, and diameter and in vivo confocal microscopic assessment of the endothelium in healthy corneas of young adults

PurposeDespite the importance of a healthy endothelial layer in anterior segment surgery, the possible influence of corneal parameters on endothelial cell density (ECD) has largely been ignored in the young adult eye. This study investigated the possible associations between corneal tomographic parameters and ECD values in young adults.MethodsSubjects aged 21–30 years, with normal corneas were recruited. Mean ECD, mean cell area (MCA), coefficient of variation for cell area (COVA), and proportion of hexagonal cells were derived by in vivoconfocal microscopy. The Orbscan II system was used to measure corneal parameters including: thickness, horizontal corneal diameter, corneal curvature, anterior and posterior elevation, and eccentricity.ResultsSixty-two subjects (42 female, 20 male) were included (mean age 25±3 years). Overall mean ECD was 3169±309 cells/mm2 with no differences between genders. Mean percentage of hexagonality was 53±5%, male subjects (55%) had a higher percentage of hexagonal cells than female subjects (51%) (P=0.02). Central corneal thickness (CCT) was 529±43 μm. Central ECD was significantly correlated with CCT (Pearsons r=0.26, P=0.04). However, horizontal corneal diameter (r=0.19, P=0.14), anterior corneal curvature (r=−0.07, P=0.6), and posterior corneal curvature (r=−0.07, P=0.6) were not correlated with ECD or percentage of hexagonality. There was no statistically significant association between anterior chamber depth (3.6±0.3 mm) and ECD (r=0.15, P=0.3).ConclusionCorneal thickness is related to ECD in normal young adult eye, with lower ECD values identified in thinner corneas; however, corneal diameter and corneal curvature do not have a significant correlation with ECD.

Sphere-forming cells from peripheral cornea demonstrate the ability to repopulate the ocular surface

BackgroundThe limbus forms the outer rim of the cornea at the corneoscleral junction and harbours a population of stem cells for corneal maintenance. Injuries to the limbus, through disease or accidents such as chemical injuries or burns, may lead to significant visual impairment due to depletion of the native stem cells of the tissue.MethodsSphere-forming cells were isolated from peripheral cornea for potential use as transplantable elements for limbal stem cell repopulation and limbal reconstruction. Immunocytochemistry, live cell imaging and quantitative PCR were used to characterize spheres and elucidate activity post implantation into human cadaveric corneal tissue.ResultsSpheres stained positively for stem cell markers ∆NP63α, ABCG2 and ABCB5 as well as the basal limbal marker and putative niche marker, notch 1. In addition, spheres also stained positively for markers of corneal cells, vimentin, keratin 3, keratocan and laminin, indicating a heterogeneous mix of stromal and epithelial-origin cells. Upon implantation into decellularized corneoscleral tissue, 3D, polarized and radially orientated cell migration with cell proliferation was observed. Cells migrated out from the spheres and repopulated the entire corneal surface over 14 days. Post-implantation analysis revealed qualitative evidence of stem, stromal and epithelial cell markers while quantitative PCR showed a quantitative reduction in keratocan and laminin expression indicative of an enhanced progenitor cell response. Proliferation, quantified by PCNA expression, significantly increased at 4 days subsequently followed by a decrease at day 7 post implantation.ConclusionThese observations suggest great promise for the potential of peripheral corneal spheres as transplantable units for corneal repair, targeting ocular surface regeneration and stem cell repopulation.

The need for all cataract surgeons to run a regular vitreous loss fire drill

Calling all cataract surgeons! Is your low vitreous loss rate storing up future problems for your staff or trainees? Vitreous loss is a rare but inevitable complication of cataract surgery, occurring in ~ 2% of phacoemulsification surgeries, yet the predicted probability for this complication can range from o0.75 to 475%, depending on the patient’s risk profile.1 Despite risk stratification, these numbers can be unduly influenced and confounded in a training university hospital environment by the experience level of the surgeon and the degree of supervision provided. As capsule rupture and vitreous loss can be a stressful situation, it follows then that a robust plan is required to ensure proper management, particularly when it is a relatively rare occurrence. Proper management requires that the necessary equipment be readily available and that both the surgeon and theatre staff be familiar with its setup and use. The proper and timely management of vitreous loss can have a significant impact on patient outcomes, principally retinal detachment and cystoid macular oedema.1,2 A recent publication from the UK National Ophthalmology Database Study of Cataract Surgery suggested that a surgeon’s level of experience was a risk factor in pseudophakic retinal detachment, which they extrapolated to be related to the quality of the management of vitreous loss.2 A trainee ophthalmologist may only see vitreous loss on two occasions every 100 cataract surgeries. The actual rate may be much lower if the senior surgeon operates on the complex cases. A recent publication demonstrated that opportunities to manage such surgical complications as a trainee are scarce.3 In the private practice setting, the cataract surgeon’s low complication rate can result in a lack of familiarity for the theatre staff to the practical measures required to address vitreous loss. This lack of familiarity can be magnified with new trainees, a rapid turnover of theatre staff, or a new theatre environment. The best way to address this situation is to regularly run a ‘vitreous loss practice drill’; to educate and evaluate the surgical team’s ability to anticipate and deal with this event. To test this theory, ophthalmologists attending a recent West of Scotland postgraduate teaching session were surveyed regarding their level of experience of cataract surgery. Subsequently, they were asked to identify any additional items required to perform an anterior vitrectomy and specify their location in the theatre suite. There were 22 responses in total, comprising 13 consultants and 9 trainees from a range of hospitals. No respondent had ever previously participated in a ‘practice drill’. Additional items requested included: anterior vitrector (91%), triamcinolone (73%), miochol (59%), suture (41%), and a threepiece IOL (36%), and 23% requested an experienced theatre nurse! Only 13% of surgeons could identify exactly where to find the required equipment. Indeed, 13% stated they were in a (non-specific) cupboard, 23% would ask the theatre nurse, and 50% stated that they did not know the precise location. Following this exercise, an educational session was delivered to all attendees and theatre staff to improve knowledge and orientate them to the theatre environment. This ‘vitreous loss fire drill’ has since been repeated at 6 monthly intervals to maintain awareness and optimize training exposure. The purpose of a ‘fire drill’ is to familiarize the participants with an uncommon emergency procedure (safe evacuation) during a stressful situation (eg, a fire) that requires effective action for an optimum outcome. A similar exercise has been performed for intravitreal antibiotics in the emergency setting.4 We recommend that similar practice runs should be conducted with all new trainees, surgeons, and staff for the safe and effective management of vitreous loss. A simple survey can be a cost-effective teaching tool and C O M M E N T Eye (2017) 31, 1120–1121

Analysis of Glaucoma Subtypes and Corresponding Demographics in a New Zealand Population

Purpose: The aim of this paper was to determine the diagnosis distribution and demographic characteristics of glaucoma in a New Zealand population. Methods: The clinical records of all patients presenting consecutively to the Auckland District Health Board Glaucoma Service over a 6-month period were reviewed. Demographic parameters including ethnicity, age at presentation, and gender were collected along with all clinical data. Results: The case records of 857 patients were reviewed. Primary open-angle glaucoma (POAG) was the most common diagnosis (39.0%, n = 235), followed by primary-angle closure (PAC) diagnoses (24.8%, n = 149). This group was formed by the combination of narrow angle 18.1% (n = 109), narrow-angle glaucoma 0.3% (n = 2), PAC 2.1% (n = 13), and PAC glaucoma 4.2% (n = 25). Normal-tension glaucoma (NTG; 17.4%, n = 105), secondary glaucoma (SG; 11.5%, n = 69), ocular hypertension (5.0%, n = 30), and mixed mechanism (2.3%, n = 14) were also found. There was a significant difference in the ethnic distribution in the study population compared to the catchment population (p < 0.001). Caucasian and Indian ethnicities were overrepresented, whereas the Pacific Island Nation ethnicity was underrepresented in all groups except SG. The Maori ethnicity was underrepresented in all groups except PAC. The underrepresentation was most prominent in POAG (only 2 patients of Pacific origin and 1 Maori patient with POAG). Significant differences were identified in gender distribution including a higher preponderance of females in NTG and PAC. Significant differences in age at presentation were also identified between different glaucoma subtypes and ethnicities. Markers of glaucoma severity did not vary with respect to demographic characteristics. Conclusion: In a tertiary glaucoma service in New Zealand, Maori, Pacific peoples, and, to a lesser extent, Asians are underrepresented, while Caucasians and Indians are overrepresented in the glaucoma population.

The Sheep Cornea: Structural and Clinical Characteristics

ABSTRACT Purpose: The aim of this study was to perform qualitative and quantitative analyses to characterize the corneas of young, healthy sheep. Materials and methods: Eight healthy male sheep, 10 months to 1 year of age, were included as experimental subjects. Central corneal thickness was measured using a handheld pachymeter, and an Easygraph corneal topographer provided topographic maps. Microstructural imaging of corneal layers was achieved by using the Heidelberg Retina Tomograph III Rostock Corneal Module in vivo corneal microscope (IVCM). An Ocular Response Analyzer (ORA) provided quantitative measurements of intraocular pressure (IOP), corneal hysteresis (CH), and corneal resistance factor. Tissue histology and immunohistochemistry were carried out to obtain detail on the corneal layers. Results: Light microscopy and immunohistochemical labeling revealed a stratified epithelium, a limbus with numerous limbal crypts, a thick basement membrane, a thin Bowman’s layer, a thick corneal stroma with a dense population of keratocytes, and a thick, hyper-reflective Descemet’s membrane. Using IVCM, the cell density of the basal layer was noted to be significantly higher than that of other epithelial cell types. The density of keratocytes was significantly higher (P value = 0.0223) in the anterior compared to the posterior stroma. The endothelial cells were organized in a characteristic honeycomb pattern. The mean and standard deviation values for central corneal pachymetry were 623.14 ± 19.5 μm and 616.37 ± 34.87 μm for the left and right eyes, respectively. ORA-derived mean values for IOPcc and CH for the left and right eyes were 14.93 ± 1.73 mm Hg and 15.16 ± 2.02 mm Hg and 3.56 ± 0.72 mm Hg and 3.73 ± 0.49 mm Hg, respectively. Conclusions: The anatomical and clinical characteristics of the sheep cornea, as outlined in this study, make the sheep a suitable and relevant model for corneal research. This study provides researchers with important data on the suitability of sheep as a model for ophthalmic experiments.