Ocular Surface Structures Research Articles

Investigation of antioxidant systems in human meibomian gland and conjunctival tissues

Oxidative stress (OS) associated with direct contact with the environment and light exposure is a very potent and continuous stressor of the ocular surface and internal structures of the eye that are required to manage its effects. Constant replenishment of tears together with the superficial lipid layer produced by the meibomian glands (MG) is one protective mechanism. The lipid-rich fraction of the tears coats the deeper aqueous fraction, preventing its evaporation. However, lipids are particularly sensitive to oxidative damage that could alter tear film quality. To counteract oxidative damage, MG along with other structures of the ocular surface use primary antioxidant (AO) systems to limit OS damage such as lipid peroxidation. Limited information concerning the primary enzymatic AO system of the human MG prompted this investigation. Using different approaches (RT-PCR, enzymatic activity assays and immuno-fluorescent microscopy), we determined the presence, distribution and subcellular locations of the major AO enzymes belonging to the classical catalytic triad (superoxide dismutase, catalase and glutathione peroxidases) in adult human MG and conjunctiva (Conj). We showed that both tissues exhibit glutathione peroxidase expression. In addition to the ubiquitous cytosolic GPx1 protein, there was significant expression of GPx2, GPx4 and GPx7. These isoforms are known to preferentially scavenge phospholipid-hydroperoxide compounds. This characterization of the primary AO system of human MG and Conj may help pave the way for the development of diagnostic procedures and have implications for treatment of common MG dysfunction (MGD) and dry eye syndrome (DES).

Clinical observation of pterygium excision combined with conjunctival autograft for the treatment of pterygium

Objective To observe the therapeutic effect of pterygium excision combined with autologous conjunctival transplantation in the treatment of pterygium. Methods The medical records of 95 eyes of 80 cases with pterygium in our hospital from February 2011 to January 2012 were analyzed.The patients were divided into two groups randomly.The observation group had 47 eyes of 40 cases and the control group had 48 eyes of 40 cases.The pterygium had been resected under a microscope.The patients of the observe group had been transplanted with autologous limbal conjunctiva on the the pterygium excised area.All patients had been followed-up for 3 years after surgery. Results 86 eyes of 71 cases (90.53%) of pterygium were fully cured with normal wound healing and transparent corneal epithelia. Only 9 cases (9.47%) had recurrenced, in which 1 case from the observation group and 8 cases from the control group. The recurred cases returned to normal after the secondary operation. Conclusion Pterygium excision with conjunctival autograft transplantation promotes the rapid recovery of ocular surface structure and function, and it has important significance to reduce the recurrent rate. Key words: Pterygium; Transplantation, conjunctival, limbal

The role of dinucleoside polyphosphates on the ocular surface and other eye structures.

Dinucleoside polyphosphates comprises a group of dinucleotides formed by two nucleosides linked by a variable number of phosphates, abbreviated NpnN (where n represents the number of phosphates). These compounds are naturally occurring substances present in tears, aqueous humour and in the retina. As the consequence of their presence, these dinucleotides contribute to many ocular physiological processes. On the ocular surface, dinucleoside polyphosphates can stimulate tear secretion, mucin release from goblet cells and they help epithelial wound healing by accelerating cell migration rate. These dinucleotides can also stimulate the presence of proteins known to protect the ocular surface against microorganisms, such as lysozyme and lactoferrin. One of the latest discoveries is the ability of some dinucleotides to facilitate the paracellular way on the cornea, therefore allowing the delivery of compounds, such as antiglaucomatous ones, more easily within the eye. The compound Ap4A has been described being abnormally elevated in patient's tears suffering of dry eye, Sjogren syndrome, congenital aniridia, or after refractive surgery, suggesting this molecule as biomarker for dry eye condition. At the intraocular level, some diadenosine polyphosphates are abnormally elevated in glaucoma patients, and this can be related to the stimulation of a P2Y2 receptor that increases the chloride efflux and water movement in the ciliary epithelium. In the retina, the dinucleotide dCp4U, has been proven to be useful to help in the recovery of retinal detachments. Altogether, dinucleoside polyphosphates are a group of compounds which present relevant physiological actions but which also can perform promising therapeutic benefits.

Contact lenses as drug controlled release systems: a narrative review

Topically applied therapy is the most common way to treat ocular diseases, however given the anatomical and physiological constraints of the eye, frequent dosing is required with possible repercussions in terms of patient compliance. Beyond refractive error correction, contact lenses (CLs) have, in the last few decades emerged as a potential ophthalmic drug controlled release system (DCRS). Extensive research is underway to understand how to best modify CLs to increase residence time and bioavailability of drugs within therapeutic levels on the ocular surface.These devices may simultaneously correct ametropia and have a role in managing ophthalmic disorders that can hinder CL wear such as dry eye, glaucoma, ocular allergy and cornea infection and injury. In this narrative review the authors explain how the ocular surface structures determine drug diffusion in the eye and summarize the strategies to enhance drug residence time and bioavailability. They synthesize findings and clinical applications of drug soaked CLs as DCRS combined with delivery diffusion barriers, incorporation of functional monomers, ion related controlled release, molecular imprinting, nanoparticles and layering. The authors draw conclusions about the impact of these novel ophthalmic agents delivery systems in improving drug transport in the target tissue and patient compliance, in reducing systemic absorption and undesired side effects, and discuss future perspectives.

Reasons to reconsider interpretation of densitometry for corneal transparency

To assess the effect of light scattering in the corneal epithelium on densitometric brightness of the stroma through mathematical modeling of the interaction between a light beam and the two-layer epithelium-stroma system. In order to study the scattering behavior of a plane-parallel non-coherent beam at the epithelium-stroma interface, a multi-age group was formed (87 patients, 174 eyes) that comprised two subgroups with equal number of assign participants: healthy patients with no systemic changes and mixed patients with undisturbed corneal transparency that, nevertheless, were under instillation therapy. In the first subgroup, the assessment of light scattering was done at random times, while in the second subgroup - within the first 200 seconds after the instillation in order to avoid a reaction of the ocular surface structures, including epithelium (rapid response of epithelial cells to instillations). Light scattering intensity was measured with Pentacam (USA). The densitometric curve and brightness maxima of the epithelium and neighboring stroma as well as the mid and upper stroma were recorded for each patient. A physico-mathematical model of the interaction between a light beam and the two-layer epithelium-stroma system was created. The study confirmed our theoretical CONCLUSION: on the effect size of light scattering intensity on the apparent densitometric brightness of the stroma. Direct densitometry of multilayered spherical objects, of which each layer possesses its own optical properties, has been proved inaccurate. Complex optical interactions in a multilayered model cause a false increase in brightness of more transparent layers that lie behind those with pronounced light scattering properties. The function that describes the false increase in scattering ability of the layer that is more transparent rises sharply at the border between the layers.

In Vivo Laser Scanning Confocal Microscopy of the Ocular Surface in Glaucoma

Over the past decade, knowledge about the ocular surface in glaucoma has significantly increased through the use of in vivo laser scanning confocal microscopy (LSCM). This in vivo imaging method can show modifications at the cellular level induced by anti-glaucoma drugs on ocular surface structures and adnexa in the eye. High-quality images of the conjunctiva, cornea, limbus, meibomian glands, and lymphoid structures during therapy can be obtained. In addition, LSCM opened new fields of research on the patho-physiology of aqueous humor (AH) hydrodynamics in untreated, and in medically or surgically treated glaucomatous patients. In these conditions, an enhancement of the trans-scleral AH outflow contributed to clarification of the mechanism of action of different anti-glaucoma medications and surgical approaches. Finally, the use of LSCM represented a huge advance in evaluation of bleb functionality after filtration surgery, defining the hallmarks of AH filtration through the bleb-wall and distinguishing functional from nonfunctional blebs. Thus, signs seen with LSCM may anticipate clinical failure, guiding the clinician in planning the appropriate timing of the various steps in bleb management. In this review we summarize the current knowledge about in vivo LSCM of the ocular surface in glaucoma.

Bioimage informatics approach to automated meibomian gland analysis in infrared images of meibography

BackgroundInfrared (IR) meibography is an imaging technique to capture the Meibomian glands in the eyelids. These ocular surface structures are responsible for producing the lipid layer of the tear film which helps to reduce tear evaporation. In a normal healthy eye, the glands have similar morphological features in terms of spatial width, in-plane elongation, length. On the other hand, eyes with Meibomian gland dysfunction show visible structural irregularities that help in the diagnosis and prognosis of the disease. However, currently there is no universally accepted algorithm for detection of these image features which will be clinically useful. We aim to develop a method of automated gland segmentation which allows images to be classified. MethodsA set of 131 meibography images were acquired from patients from the Singapore National Eye Center. We used a method of automated gland segmentation using Gabor wavelets. Features of the imaged glands including orientation, width, length and curvature were extracted and the IR images enhanced. The images were classified as ‘healthy’, ‘intermediate’ or ‘unhealthy’, through the use of a support vector machine classifier (SVM). Half the images were used for training the SVM and the other half for validation. Independently of this procedure, the meibographs were classified by an expert clinician into the same 3 grades. ResultsThe algorithm correctly detected 94% and 98% of mid-line pixels of gland and inter-gland regions, respectively, on healthy images. On intermediate images, correct detection rates of 92% and 97% of mid-line pixels of gland and inter-gland regions were achieved respectively. The true positive rate of detecting healthy images was 86%, and for intermediate images, 74%. The corresponding false positive rates were 15% and 31% respectively. Using the SVM, the proposed method has 88% accuracy in classifying images into the 3 classes. The classification of images into healthy and unhealthy classes achieved a 100% accuracy, but 7/38 intermediate images were incorrectly classified. ConclusionsThis technique of image analysis in meibography can help clinicians to interpret the degree of gland destruction in patients with dry eye and meibomian gland dysfunction.

Effect of wearing of soft corneal contact lens for long term on apoptosis of corneal epithelial cell

Background Wearing of soft contact lens,as one of the important methods to correct ametropia,has been widely applied at present.The clinically deleterious effects of soft contact lens have been reported,but researches about influence of apoptosis of corneal epithelial cells are scant.Objective This study was to detect and compare the ratio of apoptosis of corneal epithelial cells between the patients with contact lens wearing and without contact lens wearing,and explore the influence of soft contact lens wearing for long term on growth of corneal epithelial cells after injury.Methods A retrospective nest case-controlled study was designed.Forty eyes of 20 myopic patients with wearing of soft contact lens for ≥5 years and 40 eyes of 20 myopic patients without wearing of soft contact lens were included in Affiliated Hospital of Guiyang Medical College.All the patients received the off-flap epipolis laser in situ keratomileusis (Epi-LASIK) from 2010 October to 2011 June.The corneal flaps were collected during the surgery.The apoptosis of corneal epithelial cells was detected by flow cytometry(FCM),and the difference of apoptotic proportion between the two groups was compared using independent sample t test.Results The FCM scatter plot showed that compared to the without contact lens wearing group,the early stage of apoptotic cells with high staining annexin V and low staining proaium iodide (PI) were much more,and survival cells with low staining annexin V and PI were less,and necrotic and late stage of apoptotic cells with high staining of annexin V/PI were more in the with contact lens wearing group.The early stage of apoptosis proportion of corneal epithelial cells was (11.23 ± 5.31)％ in the with contact lens wearing group,and that in the without contact lens wearing group was (7.31± 5.43)％,showing a significant difference between them (t=2.754,P=0.008).Conclusions A long term wearing of contact lens induce more apoptosis of corneal epithelial cells,which can result in a disorder of structure and function of ocular surface during the wound healing stage. Key words: Soft contact lens; Epipolis laser in situ keratomileusis; Corneal epithelial cell; Apoptosis; Flow cytometry

Nutrition and Dry Eye

The tear film is a complex mixture of molecules such as lipids, mucins and water, whose function is to protect the eye from external factors such as environmental stimuli, traumas and infections. It is secreted by specific structures, but also, in part, derives from the blood stream. Substances taken with food can directly or indirectly influence tear film composition so inducing changes of the ocular surface. When the tear film is altered a condition known as dry eye may develop. Diet derived substances can be of help in the treatment of this condition. Among these substances essential fatty acids, of the omega-6 and 3 series, can play a role in the control of inflammation and in promoting the recovery of the ocular surface structures. Also some aminoacid implementation, with molecules that participate to collage composition, may participate in the recovery of the ocular surface structures undergoing the inflammatory stress.

A New Safety Concern for Glaucoma Treatment Demonstrated by Mass Spectrometry Imaging of Benzalkonium Chloride Distribution in the Eye, an Experimental Study in Rabbits

We investigated in a rabbit model, the eye distribution of topically instilled benzalkonium_(BAK) chloride a commonly used preservative in eye drops using mass spectrometry imaging. Three groups of three New Zealand rabbits each were used: a control one without instillation, one receiving 0.01%BAK twice a day for 5 months and one with 0.2%BAK one drop a day for 1 month. After sacrifice, eyes were embedded and frozen in tragacanth gum. Serial cryosections were alternately deposited on glass slides for histological (hematoxylin-eosin staining) and immunohistological controls (CD45, RLA-DR and vimentin for inflammatory cell infiltration as well as vimentin for Müller glial cell activation) and ITO or stainless steel plates for MSI experiments using Matrix-assisted laser desorption ionization time-of-flight. The MSI results were confirmed by a round-robin study on several adjacent sections conducted in two different laboratories using different sample preparation methods, mass spectrometers and data analysis softwares. BAK was shown to penetrate healthy eyes even after a short duration and was not only detected on the ocular surface structures, but also in deeper tissues, especially in sensitive areas involved in glaucoma pathophysiology, such as the trabecular meshwork and the optic nerve areas, as confirmed by images with histological stainings. CD45-, RLA-DR- and vimentin-positive cells increased in treated eyes. Vimentin was found only in the inner layer of retina in normal eyes and increased in all retinal layers in treated eyes, confirming an activation response to a cell stress. This ocular toxicological study confirms the presence of BAK preservative in ocular surface structures as well as in deeper structures involved in glaucoma disease. The inflammatory cell infiltration and Müller glial cell activation confirmed the deleterious effect of BAK. Although these results were obtained in animals, they highlight the importance of the safety-first principle for the treatment of glaucoma patients.

Dry eye analysis of diabetes with cataract patients after phacoemulsification

Background Cataract phacoemulsification combined with intraocular lens (IOL) implantation is a primary treatment for cataract.However,tear film stability and ocular surface structure are affected after surgery,especially some cataract patients with diabetes.Researches determined that tear film dysfunction is an important causative factor of dry eye.Objective This study was to investigate the change of tear film after phacoemulsification in cataract patient with diabetes.Methods A non-randomized cases-controlled study was designed.Thirty-six cataract patients with diabetes (54 eyes)and matched 32 patients (40 eyes)with age-related cataract were included in this study in Tianjin First Center Hospital from October,2010 to May,2011.Phacoemulsification and IOL implantation was performed on the all patients with the same topical eyedrops in both groups.Dry eye-related symptom was surveyed and scored by questionnaire,and tear film break-up time (BUT),Schirmer Ⅰ test(S Ⅰ t)and corneal fluorescein(FL) were examined 3 days before operation and 1 day,1 week,1month,3 months after operation.Written informed consent was obtained from each patient before entering this trial.Results The percentage with preoperative symptoms of dry eye was 36.2％ and postoperative dry eye symptoms accounted for 75.8％.Significant differences were seen in dry eye symptom score,FL score,BUT value and S Ⅰ t value between the diabetic cataract group and only cataract group as well as among 4 time points(dry eye symptom score:Fgroup =139.347,P =0.000 ; Ftime =342.741,P =0.000 ; FL score: Fgroup =14.073,P =0.000 ; Ftime =332.697,P =0.000 ; BUT value: Fgroup =28.198,P =0.000 ; Ftime =868.364,P =0.000 ; S Ⅰ t value: Fgroup =2.848,P =0.095 ; Ftime =564.017,P=0.000).FL scores of 2 groups were significantly higher in postoperation than those in preoperation (P＜0.05),and those of diabetic cataract group were significantly higher than only cataract group(P＜0.05),but no significant difference was found between postoperation 3 months and preoperation (P＞0.05).BUT was shorter in postoperation than that in preoperation in the diabetic cataract group(P＜0.05).S Ⅰ t values in postoperative 1 day and 1 week were significantly lower than in preoperation in both groups(P＜0.05).However,S Ⅰ t values returned to normal from 1 month through 3 months in both groups(P＞0.05).Conclusions Tear film dysfunction occurs after operationin cataract patient with type 2 diabetes.It is thought that cataract patient with diabetes is susceptible population of dry eye.Dry eye appears more early and severer in diabetes patients after phacoemulsification combined with IOL implantation. Key words: Diabetes; Cataract; Phacoemulsification; Dry eye

The Role of Dyslipidemia on Ocular Surface, Lacrimal and Meibomian Gland Structure and Function

Purpose: Dyslipidemia is characterized by high lipid blood levels that are risk factors for cardiovascular diseases, which are leading causes of death. However, it is unclear whether dyslipidemia is a cause of the dry eye syndrome (DES). Therefore we determined in transgenic mice models of dyslipidemia, whether there is an association with DES development.Methods: Dyslipidemic models included male and female adult mice overexpressing apolipoprotein CIII (Apo CIII), LDL receptor knockout (LDLR-KO) and ApoE knockout (ApoE-KO). They were compared with age- and gender-matched C57BL/6 mice. Ocular health was evaluated based on corneal slit lamp assessment, phenol red thread test (PRT) and impression cytology. Blood lipid profiles and histology of meibomian and lacrimal glands were also evaluated. Effects of high-fat diet and aging were observed in LDLR-KO and ApoCIII strains, respectively.Results: Body weight and lacrimal gland weight were significantly higher in male mice compared to females of the same strain (P < 0.05). Body weight was significantly lower in LDLRKO mice receiving high lipid diet compared to their controls (P = 0.0043). ApoE-KO were hypercholesterolemic and ApoCIII hypertriglyceridemic while LDLR-KO showed increases in both parameters. The PRT test was lower in male LDLR-KO mice with high-fat diet than control mice with standard diet (P = 0.0273). Aging did not affect lacrimal structural or functional parameters of ApoCIII strain.Conclusions: DES development is not solely dependent on dyslipidemia in relevant mice models promoting this condition. On the other hand, lacrimal gland structure and function are differentially impacted by lipid profile changes in male and female mice. This dissociation suggests that other factors beside dyslipidemia impact on tear film dysfunction and DES development.

Management of Ocular Conditions in the Burn Unit: Thermal and Chemical Burns and Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis

Patients in burn intensive care units suffer from potentially life-threatening conditions including thermal or chemical burns and Stevens-Johnson syndrome/toxic epidermal necrolysis. There is often involvement of the ocular surface or adnexal structures which may be present at the time of hospital admission or may develop later in the hospital course. This article will describe the types of ocular burns, the mechanisms and manifestations of Stevens-Johnson syndrome/toxic epidermal necrolysis, the circumstances that may influence outcome, and acute and long-term treatment strategies, including new and evolving options.

Drug Delivery Systems for Ophthalmic Administration of Antiinflammatory Agents

Anti-inflammatory agents are routinely used to treat inflammatory diseases affecting both anterior and/or posterior segments of the eye. Corticosteroids and NSAIDs can be administered either topically onto the ocular surface structures or injected into the eye. However, one of the most important handicaps of ocular treatments is the presence of several anatomical and physiological barriers in the eye that drastically reduce drug access to the target site. The hydrophobicity of anti-inflammatory agents, low drug bioavailability, and the invasiveness of intraocular drug delivery are main reasons to explore the potential application of drug delivery-related technologies to develop new antiinflammatory ocular therapies. This review summarizes conventional anti-inflammatory treatments for ocular diseases and the ongoing research efforts to develop improved drug delivery systems. Micro-size intraocular implants, microparticles, nanoparticles, and liposomes are the preferred delivery systems in study.

Conjunctival–Corneal Intraepithelial Neoplasia (Bowen Disease) Treated With Orthovoltage

To report an exceptionally large conjunctival-corneal intraepithelial neoplasia (CCIN) (Bowen disease), for which the size of the tumor made classical treatment difficult, and to highlight the role of orthovoltage as an alternative treatment mode with good results. Observational case report of a healthy 61-year-old man with CCIN. Given its extension, alternative treatment was performed with orthovoltage, thus avoiding surgery, with adjuvant cryotherapy and mitomycin C, and potential complications. After administering topical anesthetic, a therapeutic contact lens was placed on the cornea; then, the eyelids were held open with a blepharostat. A 1-mm lead plate with a window was placed over the blepharostat. The shape of the window reproduced the shape of the tumor to protect the rest of the eye structures from radiation. Orthovoltage was administered with direct field radiation that was focused on the tumor through the window. The patient received 500 cGy in 2 sessions/week for 2 weeks (2000 cGy) and then 7 sessions 300 cGy daily (2100 cGy). Evolution was good without side effects. After one-year follow-up, the patient was asymptomatic, without alterations of ocular surface or deep structures. Safely administered orthovoltage may be a good therapeutic option for the treatment of CCIN when complete surgical resection is complicated by the extension of the tumor. Compared with topical treatment, radiation is easier to administer, shortens and simplifies the treatment, and is independent of patient compliance.

Ocular Tolerance to a Topical Formulation of Hyaluronic Acid and Chitosan-Based Nanoparticles

Hyaluronic acid-chitosan nanoparticles (HA-CS NPs) have the potential to serve as a reliable drug delivery system to topically treat ocular surface disorders. We evaluated the in vivo uptake by ocular structures, the acute tolerance, and possible alterations of tear film physiology in rabbits. Fluorescent HA-CS NPs (fl-HA-CS NPs) were prepared by ionotropic gelation using fluoresceinamine-labeled hyaluronic acid and resuspended in buffer. fl-HA-CS NPs (30 microL, 0.5 mg/mL) and fluoresceinamine-HA conjugate (30 microL) were instilled into rabbit eyes every 30 minutes for 6 hours. In vivo uptake and acute tolerance were characterized 24 hours after the first instillation and compared with preinstillation measurements. Clinical signs, including tear production, lacrimal drainage system patency and reflux, and ocular surface pathology, were evaluated. The rabbits showed no signs of ocular discomfort or irritation after exposure to HA-CS NPs. No macroscopic alteration in ocular surface structures was observed. fl-HA-CS NPs were present inside conjunctival and corneal epithelial cells, although the distribution within the cells was different. The fl-HA-CS NPs had no significant effects on tissue morphology and functionality, tear production, or drainage. Taken together, these data demonstrate that HA-CS NPs are a safe drug carrier for ocular surface application.

Prevalence of Dry Eye in the Normal Population in Jeddah, Saudi Arabia

Purpose: To estimate the prevalence of dry eye disease in the normal non-complaining population.Methods: Prospective systematic random sampling study of 251 subjects who accompanied patients with appointments to the eye clinic. Interviewers administered a dry eye symptoms and risk factor questionnaire. Tear film break up time, fluorescein corneal staining and Schirmer’s test were performed. Slit lamp examination to evaluate the lid margins, Meibomian glands and ocular surface structures was also performed.Results: Dry eye was diagnosed in 234 (93.2%) subjects on the basis of presence of one or more symptoms occurring often or most of the time, together with one or more of the following signs: tear film break up time ≤ 10 seconds, fluorescein corneal staining ≥ grade 1 and Schirmer test score ≤ 5 mm. There was no statistically significant association between dry eye with advancing age or gender. Blepharitis was detected in 215 (91.9%) of the dry eye cases. Smoking was found to be the second most common risk factor as 18.8% of the dry eye cases were smokers. Sicca syndrome was found in 24.4% of the subjects.Conclusion: Dry eye is very prevalent disease. Blepharitis was found to be very common among dry eye cases. There was no statistically significant association between dry eye and age or gender in our study population.

Diffraction-enhanced imaging of a porcine eye

Background: Diffraction-enhanced imaging (DEI) is a synchrotron-based x-ray imaging technique that has dramatically improved contrast over standard x-ray imaging techniques. It is possible to acquire images that analyze the x-ray refraction and the apparent absorption (elimination of small-angle scattering) of the object. Methods: Three formalin-fixed porcine eyes were studied at the National Synchrotron Light Source using DEI. Conventional absorption-type radiography was conducted for comparison. Results: Conventional absorption radiography did not yield significant detail of the eye anatomy. DEI showed excellent characterization of many ocular structures. The cornea, iris, lens, retina, optic nerve, as well as choroidal vasculature and the ampullae of the vortex veins could all be visualized. Interpretation: DEI represents a novel, high-resolution imaging technique that has excellent characterization of ocular anatomy. Further application of this imaging modality will be undertaken to study cataract and choroidal tumors and to examine ocular surface structures, such as the extraocular muscle insertions, more closely.

In vivo confocal microscopy of the cornea

AbstractConfocal in‐vivo microscopy so far has not found its place in routine diagnostic of anterior segment disease. But progress has been made with recent developments mainly based on Laser scanning technology. This allows an optical sectioning of less than 5 μm thickness of high contrast and in well defined distances from the corneal surface as well as the examination of conjunctiva, sclera and the lid region.Information is given how to differentiate subpopulations of the epithelium (superficial, intermedial, basal cells) as well as overall epithelial thickness measurements. This is exemplified in normal individuals, contact lens wearers and patients with various kinds of ocular surface disease.Stromal keratocytes are displayed and quantified in different corneal layers. Information on keratocyte activation by higher densities of scatterers in the cytoplasm is possible, indicating increased metabolic activity.A more wide spread use of in‐vivo confocal microscopy will allow to judge on woundhealing in all kind of corneal disease and repair mechanisms such as corneal re‐innovation following refractive corneal surgery.Cell populations such as Langerhans cells are displayed and quantified allowing information on immunological corneal activity in‐vivo. Woundhealing modulation in Glaucoma filtering surgery can be displayed on a cellular level and microcyst formation depending on the influence of Mitomicin C and 5 FU are demonstrated at various stages after surgery. This information may influence the postoperative management considerably.In‐vivo confocal microscopy recently has become easy to handle with improved imaging quality and possibilities of quantitative evaluation of ocular surface structures.

In vivo fibreoptic confocal imaging (FOCI) of the human ocular surface

Recent developments in the miniaturization of confocal imaging technology have resulted in the development of a hand-held confocal microscope probe. There are many structures of interest in the human eye that are within reach of a fluorescence-mode confocal microscope; this study assessed the feasibility of in vivo human ocular imaging. Safety analysis was undertaken to ensure that the laser light applied to the ocular surface structures constituted no threat to patient safety. A fibreoptic confocal imaging (FOCI) probe using an illumination wavelength of 488 nm was applied to the ocular surface of four volunteers after topical administration of sodium fluorescein. Stabilization of the probe on the ocular surface was difficult, but movement artefacts could be minimized to a satisfactory level in most subjects by a variety of procedures. High-quality images of conjunctival epithelial and goblet cells, lamina propria structures, accessory lacrimal glands, lacrimal ducts and superficial sclera were obtained. Lateral resolution was 1-1.5 microm and axial resolution was approximately 30 microm; individual erythrocytes could be seen in conjunctival vessels. The rete ridges and intervening epithelial components, including the probable location of corneal limbal stem cells, could be viewed, although it was not possible to distinguish cell subgroups. The study showed that fluorescence-mode imaging of the ocular surface is a viable and promising tool for assessment of diseases and processes involving superficial ocular structures. Refinement of equipment and techniques, particularly probe stabilization, is necessary to realize fully the potential of FOCI for ocular use.