Contextual detection of ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms

We report a novel prototype algorithm using contextual knowledge to locate ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms. We use high-resolution images acquired by an Optos ultra-wide-field-of-view (more than 200 degrees) scanning laser ophthalmoscope. We leverage the simultaneous occurrence of ischemia with a number of other signs, detected automatically, typical for the state of progress of the condition in a diabetic patient. The specific nature of ischemic and non-ischemic regions is determined with an AdaBoost learning algorithm. Preliminary results demonstrate above 80% pixel classification accuracy against manual annotations.

Quality of life and relative importance: a comparison of time trade-off and conjoint analysis methods in patients with age-related macular degeneration

AIM

To investigate the relative priorities in quality of life (QoL) in patients with age-related macular degeneration (AMD).

METHODS

Measures of visual function, QoL and utility associated with visual loss were obtained from 122 patients with AMD classified according to macular morphology. The two methods of utility assessment were time trade-off (TTO) and conjoint analysis (CA), which have been recommended by the UK's National Institute of Clinical Excellence as techniques for the assessment of healthcare priorities.

RESULTS

Results show that the two methods for assessing utility are poorly related: TTO relates moderately to visual function and disease severity but CA does not. CA identified two different subgroups of patients: one with outdoor mobility and the other with reading as their main priority.

CONCLUSION

Further work is needed and caution required in interpreting data obtained using these methodologies for determining their relative importance in vision-related QoL studies.

Congenital Corneal Anesthesia

Congenital corneal anesthesia is a rare clinical entity that poses a diagnostic dilemma, particularly in the pediatric age group. The sensory deficit may be confined to the cornea, or extend to other divisions of the trigeminal nerve. The sensory deficit may occur as an isolated abnormality, as part of a complex neurological syndrome, or it may occur in association with multiple somatic abnormalities and congenital insensitivity to pain. This condition usually presents between the ages of 8 to 12 months. Poor vision, photophobia, conjunctival injection, and corneal ulceration in the absence of pain and distress in a child should alert the clinician to the possibility of anesthetic cornea. In the early stages of presentation, punctuate keratopathy is the main feature, which may progress to non-healing persistent corneal epithelial defects. This stage may progress to acute corneal lysis and perforation. In most patients, conservative approaches such as copious lubrication, prevention of self-harm and cautious use of bandage contact lenses are effective in preventing progressive corneal damage. Tarsorrhapy is effective in promoting epithelial healing and permanent lateral tarsorraphy may prevent further development of epithelial defects. Amniotic membrane graft may be considered in order to improve epithelial healing. Corneal grafts carry a poor prognosis. Accurate initial diagnosis, evaluation, and proper management are paramount to prevent visual loss due to long-term complications of corneal anesthesia. This review of the literature outlines the problems and approaches in diagnosis, evaluation, and management of this rare condition.

Development of a miniaturised drug delivery system with wireless power transfer and communication

The development of an implantable system designed to deliver drug doses in a controlled manner over an extended time period is reported. Key performance parameters are the physical size, the power consumption and also the ability to perform wireless communications to enable the system to be externally controlled and interrogated. The system has been designed to facilitate wireless power transfer, which is very important for miniaturisation as it removes the need for a battery.

"Worm in the eye": the rationale for treatment of DUSN in south India

AIM

To discuss the rationale for different techniques of treatment for DUSN (diffuse unilateral subacute neuroretinitis) and their effectiveness in two patients from south India.

METHODS

Two rare cases of live worms in DUSN from India are reported, where filarial Brugia malayi is endemic. Both cases presented with progressive unilateral loss of vision with no history of animal contact. They were 40 year old, apparently healthy men. In case 1, the worm (1500-2000 microm) was easy to identify with wriggling movements among crisscrossing diffuse subretinal tracks. The worm was destroyed by a single shot of laser to its advancing end, which was followed by oral steroid to control the inflammation caused by the dead worm. In case 2, the worm was small and difficult to identify. Initially diffuse neuroretinitis was diagnosed and treated with intravenous methylprednisolone and oral corticosteroid. A week later, a small live worm (400-600 microm) was found and subsequently destroyed by laser photocoagulation followed by a combination of anthelminthics.

RESULTS

The patients' vision had improved to 6/60-6/36 from counting fingers after a few weeks.

CONCLUSION

The role of a combination of laser treatment, systemic steroid, and anthelminthics is discussed.

Cellular retention on diagnostic contact lenses: an evaluation of current cleaning protocol

AIMS

To compare cellular contamination of diagnostic contact lenses after two different cleaning methods.

METHODS

Twenty-five used diagnostic contact lenses were cleaned by two different methods and the material retained on their contact surface examined for cells. Two diagnostic contact lenses were examined using electron microscopy and surface debris was subjected to x-ray photoelectron spectroscopy.

RESULTS

Significantly more cells were present on used lenses compared with controls (P<0.001). There was no significant difference in total cell count between the lenses subjected to the two cleaning strategies but the lenses simply wiped clean retained marginally more nucleated cells than controls (P=0.039). Electron microscopy showed the majority of the debris on or close to the rim of the lens. X-ray photoelectron spectroscopy confirmed the presence of proteinaceous material.

CONCLUSIONS

Regardless of cleaning method, significant cellular debris is retained on the surface of diagnostic contact lenses after use.

The aetiology and associations of conjunctival intraepithelial neoplasia

AIM

To summarise the main causes and associations of conjunctival intraepithelial neoplasia (CIN) found in the literature to date.

METHOD

Literature search using Ovid databases on the NHS Scotland E-library, Medline, and the Cochrane Library. The internet search engine Google Scholar was also used to identify relevant articles.

RESULTS

The main causes and associations of CIN in the literature are sun exposure and distance from the equator; human papillomavirus infection, increased p53 expression, and HIV seropositivity. It has been found that in HIV positive individuals CIN is on the increase with people being affected with more aggressive tumours at younger ages.

CONCLUSION

Given that CIN is becoming more common in HIV infected populations and that it has the potential to cause severe disability, it is important to improve our understanding of the condition. Early identification of CIN by an understanding of its aetiology and associations may enable the implementation of preventative measures to reduce its incidence and potentially lead to the diagnosis and further management of conditions such as HIV. Young people presenting with CIN in particular may benefit from HIV testing.

Evolving concepts on the pathogenic mechanisms of aniridia related keratopathy

Heterozygosity for PAX6 deficiency (PAX6+/-) results in aniridia. Corneal changes in aniridia-related keratopathy (ARK) include corneal vascular pannus formation, conjunctival invasion of the corneal surface, corneal epithelial erosions and epithelial abnormalities, which eventually result in corneal opacity and contribute to visual loss. Corneal changes in aniridia have been attributed to congenital deficiency of corneal limbal stem cells. The aim of this paper is to review the potential mechanisms that may underlie the pathogenesis of aniridia related keratopathy. Current evidence, based on clinical observations and an animal model of aniridia suggest that the proliferative potential of the corneal limbal stem cells may not primarily be impaired. The corneal changes in aniridia may be related to an abnormality within the limbal stem cell niche. The mechanisms underlying progressive corneal pathology in aniridia appear multi-factorial and include: (1) abnormal corneal healing responses secondary to anomalous extracellular matrix metabolism; (2) abnormal corneal epithelial differentiation leading to fragility of epithelial cells; (3) reduction in cell adhesion molecules in the PAX6 heterozygous state, rendering the cells susceptible to natural shearing forces; and (4) conjunctival and corneal changes leading to the presence of cells derived from conjunctiva on the corneal surface.

Superior forniceal conjunctival advancement pedicles (SFCAP) in the management of acute and impending corneal perforations

OBJECTIVE/AIM

Corneal perforations can result from a wide variety of disorders and can lead to devastating visual sequelae. Various surgical procedures have been described to manage nontraumatic corneal perforation. Conjunctival flaps offer an important technique in dealing with such corneal emergencies. We report a modified conjunctival flap procedure referred to as superior forniceal conjunctival advancement pedicle (SFCAP) in the successful management of corneal perforation and impending corneal perforation.

PATIENTS AND METHODS

Out of 20 patients who underwent SFCAP for non-traumatic corneal perforation and impending perforation, 16 had corneal perforations. Perforations were secondary to acne rosacea (2), advanced bacterial keratitis (6), corneal anaesthesia(2), multiple retinal procedures (2), previous corneal grafts with a compromised ocular surface (3), and advanced Mooren's ulcer (1).

RESULTS

The globe was preserved in all patients. In 14 of the 16 eyes with perforated corneas the pedicle stabilised. One patient, who was a chronic alcoholic, rubbed the eye during sleep detaching the pedicle a week after surgery. However, the ulcer healed and the integrity of the globe was restored. None of these patients developed secondary glaucoma or ptosis.

CONCLUSION

SFCAP is an appropriate procedure to manage corneal perforations and impending corneal perforations where donor material is not available and transplantation of such tissue is not suitable.

Immunolocalisation of leukaemia inhibitory factor in the cornea

AIM

Leukaemia inhibitory factor (LIF) is a pleotrophic cytokine expressed in a variety of cell types, and have shown to regulate stem cell proliferation, vascular genesis, inflammation, and immunity in various locations. Expression of LIF and its role in the cornea have not been studied previously. In this study, we examined the expression of LIF in the cornea.

MATERIALS AND METHOD

Immunohistochemistry was performed using polyclonal LIF antibodies, and Avidin-Biotin ABC complex on cultured human corneal epithelium corneal fibroblasts and wild-type murine corneal epithelium.

RESULTS

LIF was detected in the cytoplasm of murine corneal epithelium, cultured human corneal epithelium, and fibroblasts. The expression of LIF was mainly cytoplasmic.

CONCLUSION

LIF is expressed in the corneal epithelium and fibroblasts. It may have an important role in the maintenance of homeostasis of the corneal epithelium and cornea stroma. Further studies are necessary to elucidate the role of LIF in the cornea.

Development of a Forced Choice Photographic Questionnaire for Photic Phenomena and Its Testing – Repeatability, Reliability and Validity

AIM

To design, develop and test a system for analysis of photic phenomena.

METHOD

Extensive background research, patient interviews and theoretical studies led to development of a set of photographic images resembling photic phenomena experienced by patients. These photographic images were processed and digitally altered to create scales of severity for each photic phenomenon in which patients indicated their severity of symptoms by choice of image. The system was tested for stability and validity.

RESULTS

The system showed excellent repeatability and reliability. Face, content, criterion and construct validity were all found to be acceptable.

CONCLUSION

The photographic images of photic phenomena analyser is an acceptable, validated measure for the assessment of photic phenomena, in both pseudophakic patients and those with cataract.

A prospective study of visual function and quality of life following PDT in patients with wet age related macular degeneration

AIMS

(1) A prospective study to assess visual function measures and quality of life (QoL) in patients with wet age related macular degeneration (AMD) treated with photodynamic therapy (PDT). (2) To assess if PDT prevents severe visual loss (loss of six or more lines of distance visual acuity) in the treated eye.

METHODS

48 of 51 recruited patients with predominantly classic subfoveal choroidal neovascularisation (CNV) secondary AMD who were treated with PDT were followed up for 1 year. Assessment included distance and near visual acuity, contrast sensitivity, vision related quality of life and fluorescein angiography. Photodynamic therapy using Visudyne was carried out according to standard protocol. Patients were followed up every 3 months and treatment repeated if there was significant leakage from CNV.

RESULTS

At the 12 month follow up, 71% (n = 34) of the patients lost less than three lines of best corrected distance visual acuity. Although there were significant decreases in some of the QoL items tested, patients were significantly less anxious and more independent outdoors at the 12 month follow up.

CONCLUSION

This study is in keeping with published literature with PDT preventing severe visual loss in two thirds of treated patients with predominantly classic CNV.

Delayed diagnosis of HIV infection in ophthalmic practice

The introduction of potent antiretroviral drug combinations has transformed human immunodeficiency virus/acquired immunodeficiency disease syndrome (HIV/AIDS) from an intractable and rapidly fatal disease to a chronic manageable illness with prolonged life survival for many patients. This paper discusses the ophthalmic and medical histories of two young female patients who presented with 'atypical' optic neuropathy and toxoplasma gondii retinochoroiditis and were later found to be HIV infected. We discuss the need for increased vigilance in the ophthalmic community for suspecting HIV infection to allow optimal management of the ophthalmic and systemic manifestations of the disease spectrum associated with HIV/AIDS.

Ex vivo expansion of corneal limbal epithelial/stem cells for corneal surface reconstruction

PURPOSE

The management of severe ocular surface disease due to limbal stem cell deficiency has changed dramatically. The concept of limbal stem cells, as the source of corneal epithelium revolutionised the therapeutic approach of ocular surface reconstruction. Deficiency of limbal stem cells results in blinding ocular surface diseases. Grafting viable limbal tissue, from either fellow healthy eye or a donor eye, with the resident stem cell population may replenish limbal stem cells and can restore the corneal surface to normality. Transplanting the limbal tissue can be achieved through a variety of procedures that include cadaveric keratolimbal allograft (KLAL), live or living related conjunctival limbal allograft (Ir-CLAL) and limbal autograft. Advances in tissue engineering techniques have offered a viable alternative to overcome the limitation of limbal tissue available for transplantation. Epithelial stem cells harvested from a small limbal biopsy can be expanded in vitro on a suitable carrier and then transplanted to the diseased cornea to successfully restore the corneal surface. This article is a chronological review of the important steps that brought ex vivo expanded stem cell transplantation in ocular, particularly corneal surface reconstruction.

METHODS

The MEDLINE data base was searched for the years 1966-2002, using key words cornea, cell culture, ex-vivo expansion, limbus, stem cell, ocular surface and transplantation. Several articles that were not found by MEDLINE search were taken from references from other articles. Inclusion or exclusion of article was based on the relevance to the subject.

CONCLUSIONS

Corneal epithelial reconstruction with ex vivo expanded limbal cells is a potential tool in ocular surface reconstruction, although the technique is currently investigational. Strategies to achieve conjunctival epithelial restoration and tear film replenishment will allow ophthalmic surgeons to truly reconstruct the ocular surface.