Pho Nguyen

Correlation between optical coherence tomography-derived assessments of lower tear meniscus parameters and clinical features of dry eye disease

Purpose: To measure the correlation between subjective symptom score, conventional clinical tests, and Fourier-domain optical coherence tomography (FD-OCT) of lower tear meniscus parameters in patients with dry eye disease. Methods: Eighteen patients with dry eye disease requiring medical therapy and/or punctal occlusion were recruited for this prospective, nonrandomized, observational case series. Severity of symptoms of dry eye disease was assessed using the Indiana University Dry Eye Questionnaire 2002. Clinical assessments were completed using slit-lamp biomicroscopy, rose bengal dye staining, fluorescein tear breakup time (TBUT), and a 5-minute Schirmer test with topical anesthesia. The lower tear meniscus was imaged using an FD-OCT system with 5-&mgr;m axial resolution and measured manually by a masked grader using computer calipers. Correlation was assessed using Spearman correlation coefficient (&rgr;). Results: The mean (±SD) scaled symptom score was 58 ± 21, with a range of 0 to 100. Vital staining test averaged 1.7 ± 3.4, TBUT averaged 4.4 ± 1.8 seconds, and Schirmer tests averaged 10.2 ± 8.1 mm. As determined by optical coherence tomography, the meniscus height was 228 ± 153 &mgr;m, depth was 127 ± 79 &mgr;m, and cross-sectional area was 0.018 ± 0.021 mm2. Optical coherence tomography meniscus area was negatively correlated with the symptom questionnaire score (P < 0.01) and positively correlated with Schirmer test results (P < 0.01). There was no significant correlation between symptom score and rose bengal staining, TBUT, or Schirmer test results (P > 0.01). Conclusions: Lower tear meniscus measurement with FD-OCT is an objective noninvasive test that correlates well with symptoms of dry eye disease and the Schirmer test.

Ocular surface reconstruction: recent advances and future outlook.

Purpose of review Ocular surface disorder underlies a diverse group of prevalent diseases in the United States, caused by biological aging, autoimmune conditions, trauma, or iatrogenic factors. Left untreated, these conditions can progress to vision loss or destruction of the globe itself. This review discusses the most recent and relevant clinical and experimental advances in the treatment options for ocular surface disorders. Recent findings Current literature suggests that recent progress in tissue bioengineering, and molecular and cellular biology research presents many potential interventional therapies for ocular surface diseases. Depending on the pathogenesis of each condition, treatment options include bioengineered amniotic membrane graft, limbal stem cell transplantation, conjunctival and extraocular tissue transplantation, multiagent immunosuppressant therapy, and bioartificial devices such as lacrimal gland microdevices and keratoprostheses, or tissue adhesives. Summary Much progress has been made in the fields of microbiology, stem-cell research, tissue engineering, and bioartificial devices for the treatment of the heterogeneous group of ocular surface disorders. Intensive efforts are underway to ensure the adaptation and accessibility of these therapeutic options to the general population.

Applications of optical coherence tomography in cataract surgery.

Purpose of review The rapid emergence and widespread adoption of optical coherence tomography (OCT) has spurred the development of many ophthalmic applications. Spectral domain OCT provides high-resolution in-vivo images of both anterior and posterior segments of the eye. Innovations in anterior segment OCT (AS-OCT) aim to improve refractive accuracy and reduce surgical risks. This review focuses on the utility of AS-OCT in cataract surgery for preoperative assessment, intraoperative assistance, and postoperative management to improve surgical outcomes. Recent findings Recent advances in AS-OCT for preoperative planning include characterization of dry eye and ocular surface conditions, calculation of intraocular lens (IOL) power, delineation of anterior chamber structures, and assessment of risk factors for postoperative complications. Successful intraoperative use of AS-OCT has been described for in-vivo assessment of clear cornea wound architecture and OCT-guided femtosecond laser-assisted cataract surgery. The essential roles of OCT in managing postoperative complications include characterization of maculopathy or corneal wound integrity, assessment of IOL stability or optical changes, and evaluation of laser-assisted in situ keratomileusis flaps after cataract surgery. Summary In its rapidly evolving state, the utility of OCT in cataract surgery continues to broaden with applications from preoperative planning, intraoperative image-based treatments, and postoperative care. We advocate the judicious use of OCT, wherever clinically indicated, because routine use may not be clinically necessary or economically feasible for each stage of cataract evaluation and management.

Between-grader repeatability of tear meniscus measurements using Fourier-domain OCT in patients with dry eye.

BACKGROUND AND OBJECTIVE To examine the between-grader repeatability of height, depth, and cross-sectional area measurements of the lower tear meniscus, using a Fourier-domain optical coherence tomography (OCT) system. PATIENTS AND METHODS A total of 16 patients with dry eye had the lower tear meniscus of the right eye imaged twice in rapid succession. The tear meniscus height, depth, and cross-sectional area were measured by two masked graders using computer calipers. The between-grader variability, calculated using the pooled coefficient of variation (CV%), assessed the repeatability of the measurements. RESULTS The between-grader CV% was 12.1%, 15.7%, and 19.5% for height, depth, and area, respectively. The between-image variability was 17.1%, 13.4%, and 35.4% for height, depth, and area, respectively. The overall intraclass correlation was 99%. There was no systematic bias between the two graders. CONCLUSION Fourier-domain OCT demonstrates good between-grader and between-image repeatability in measuring the height, depth, and cross-sectional area of the tear meniscus in patients with dry eye. Measurement variability was primarily due to the difference between images rather than graders.

Applications of nanobiotechnology in ophthalmology--Part I.

Much progress has been achieved in the field of nanotechnology and its applications in ophthalmology. It is evident that drug delivery, gene therapy, implantable devices and regenerative medicine are some of the key areas of active research. To the best of our knowledge, there is limited review work on this subject area in the current literature. To assist the interested clinicians and scientists, this bipartite commentary will focus the discussion on emerging researches in nano-ophthalmology and other enabling technologies that soon may be available in the clinician’s armamentarium to maintain and restore eye sight. This installment will focus on recent discoveries in drug delivery, gene therapy, imaging and visual prostheses; the second installment will discuss the impact of nanotechnology on artificial environment, cell-nanostructure interaction, other enabling nano-ophthalmic technologies, and safety and biocompatibility of nanostructures. We will take this opportunity to introduce some exciting nano-ophthalmic applications under investigation in our laboratory. The accomplishments by the scientific community are tremendous and the future prospects are wide open.

Ocular surface reconstruction: recent innovations, surgical candidate selection and postoperative management

Intricate homeostasis maintains the rich complexity and functionality of the ocular surface. Severe ocular surface diseases cause significant morbidities, including blindness. Ocular surface reconstruction strategies restore this homeostasis. Patients with limbal deficiency may benefit from limbal stem cell transplantation to alleviate persistent epithelial defects, maintain conjunctivalization regression and corneal avascularity, and restore vision. Amniotic membrane and other substrates function as tissue surrogates and substrates for expansion of stem cells. Maximum graft survivability necessitates aggressive and comprehensive preoperative management of inflammation, infection, microtrauma, dry eye conditions and HLA compatibility. Restoration of lacrimal gland function is important, as is implementation of aggressive immunosuppression. Future advancements in stem cell biology, tissue engineering, bioartificial microsystems or regenerative medicine will supplement the therapeutic armamentarium. The next decade will be an exciting time for corneal surgeons.

Strategies for local gene therapy of corneal allograft rejection.

Penetrating keratoplasty is the most common type of tissue transplant in humans. Irreversible immune rejection leads to loss of vision and graft failure. This complex immune response further predisposes future corneal transplants to rejection and failure. A diverse armamentarium of surgical and pharmacologic tools is available to improve graft survival. In this review, we will discuss the various gene therapeutic strategies aimed at potentiating the anterior chamber-associated immune deviation to extend graft survival.

Imaging studies in a case of infectious scleritis after pterygium excision

A 44-year-old woman presented with a painful red eye for 2 weeks. Ultrasound biomicroscopy and optical coherence tomography were instrumental in the diagnosis and management of this case of infectious scleritis associated with previous pterygium excision complicated by choroidal and retinal detachments.

Ocular Surface Reconstitution

1.1 The ocular surface – anatomy and pathology The corneal epithelium, conjunctival epithelium, and the lacrimal system constitute the ocular surface. A healthy corneal epithelium is essential for corneal health and visual function. The corneal epithelium is a 5to 6-cell-thick layer that provides a defensive barrier against pathologic organisms. It exists in a dynamic equilibrium, with superficial cells being constantly shed into the tear film. Populations of pluripotent stem cells reside in the palisades of Vogt at the human corneoscleral limbus and generate transient amplified cells that centripetally migrate toward the central cornea. These transient amplified cells undergo terminal differentiation into epithelial cells and repopulate the corneal epithelium, i.e. the XYZ hypothesis (Thoft et al., 1983). Severe ocular surface disorders, such as infection, keratoconjunctivitis sicca, Stevens-Johnson syndrome, ocular cicatricial pemphigoid or chemical/thermal injuries, can progress to corneal scarring, conjunctivalization, neovascularization, or stromal melts. Depletion of the limbal stem cells may follow, resulting in impaired vision or eventual corneal blindness. According to the World Health Organization, corneal disorders, e.g. trachoma or onchocerciasis, constitute a significant cause of loss of vision and blindness in the world (Thylefors et al., 1995). The conjunctiva is a thin, transparent, mucus membrane, overlying a thin vascular stroma. It is divided into three geographic zones: bulbar, forniceal, and palpebral. The conjunctival nonkeratinized stratified epithelium contains mucin-producing goblet cells, which are important for tear film stability. Additionally, the conjunctiva participates in the ocular surface antimicrobial defense via the conjunctiva-associated lymphoid tissue, as well as secretory antimicrobial peptides, such as defensins (Haynes et al., 1999). Disorders of the conjunctiva include elastotic changes, fibrovascular proliferation, malignancies, and autoimmune conditions such as Stevens-Johnson syndrome or cicatricial pemphigoid. Complications include dysfunctional tear syndrome, keratinization, symblepharon formation, eyelid disfigurement, and eyelash misalignment. Patient discomfort, cosmetic imperfection, increased risk of infection, and visual impairment are some notable concerns. A normal tear film is essential for maintenance of the corneal and conjunctival epithelia. Composed of three layers, mucin, aqueous and lipid layers, the human tripartite tear film has antimicrobial, epitheliotrophic, mechanical, and optical properties. A wide range of physiologic or pathologic conditions, such as biologic aging, hormonal changes, chemical or thermal injuries, chronic inflammation, or autoimmune disorders, may disrupt the tear film and trigger a deleterious cascade, injuring ocular surface epithelia. Furthermore, suboptimal