Risk factors for contact lens-related microbial keratitis in Singapore

PURPOSE

To investigate independent risk factors for contact lens-related microbial keratitis in Singapore and estimate their impact on disease load.

METHODS

Cases were contact lens wearers presenting to Singapore National Eye Centre with microbial keratitis between 2008 and 2010. Community contact lens wearers were recruited as controls. All wearers completed a previously validated questionnaire describing contact lens wear history, hygiene and compliance habits, and demographics. Risk factors significant in univariate analysis (P<0.2) were evaluated in a multivariate model.

RESULTS

In all, 58 cases of microbial keratitis and 152 contemporaneous controls were identified. When controlling for other variables, Chinese had a 7 × lower risk compared with other races (95% CI: 2.3-21.3, P=0.001). Those aged between 25 and 44 years were at 3 × increased risk compared with younger wearers (95% CI: 1.1-9.6, P=0.04). Occasional overnight contact lens wear (less often than one night per week) was associated with a 4 × higher risk (95% CI: 1.2-15.4, P=0.03) compared with daily use. Not washing hands before handling was associated with a 13 × increased risk (95% CI: 1.9-84.8, P=0.008). Use of multipurpose solution A carried a 16 × higher risk compared with hydrogen peroxide (95% CI: 1.5-174.0, P=0.02). The combined PAR% for modifiable risk factors (occasional overnight wear, not washing of hands, and MPS A) was 82%.

CONCLUSIONS

Consistent with previous findings, independent risk factors for contact lens-related microbial keratitis include poor hand hygiene, occasional overnight wear, and type of lens care solution. Prolonged overnight or extended contact lens use was infrequent in this population.

Comparison of intra-ocular pressure changes with liquid or flat applanation interfaces in a femtosecond laser platform

Cataract surgery is the most common surgical procedure and femtosecond laser assisted cataract surgery (FLACS) has gained increased popularity. FLACS requires the application of a suction device to stabilize the laser head and focus the laser beam accurately. This may cause a significant escalation in intra-ocular pressure (IOP), which poses potential risks for patients undergoing cataract surgery. In this study we aimed to assess the effect of the Ziemer LDV Z8 femtosecond cataract machine on IOP. We demonstrated through a porcine model that IOP was significantly higher with a flat interface but could be abrogated by reducing surgical compression and vacuum. Pressure was lower with a liquid interface, and further altering angulation of the laser arm could reduce the IOP to 36 mmHg. A pilot series in patients showed comparable pressure rises with the porcine model (30 mmHg). These strategies may improve the safety profile in patients vulnerable to high pressure when employing FLACS with the Ziemer LDV Z8.

Demographics and Behaviour of Patients with Contact Lens-Related Infectious Keratitis in Singapore

Introduction: This study aims to identify the demographics and hygiene behaviours associated with contact lens (CL)-related microbial keratitis in Singapore. Materials and Methods: The hygiene and social behaviours of lens wearers presenting with infectious keratitis in Singapore were examined using an externally validated questionnaire. Fifty-eight consecutive lens wearers who presented with infectious keratitis at Singapore National Eye Centre were surveyed using a self-administered questionnaire. Patients’ demographics, CL-related behaviour, attitude to aftercare visits and microbial study results were collected and analysed. Results: More than half (55%) of the patients surveyed were female, and the average age of the participants was 25.7 ± 6.4 years. Ninety-six percent of participants used soft CL, with the majority wearing monthly disposable lenses (74.1%). Myopia was the commonest reason for use of CL. CL overwear (81%), sleeping (50.9%) and swimming (33%) with their CL were the major non-compliant behaviours discovered. When encountered with eye discomfort as a result of lens-related infective keratitis, 83% of patients sought the advice of general medical practitioners prior to presentation at the hospital. Many (59%) patients have encountered media coverage but only 24% had any behavioural change as a result. Many patients relied on the recommendations of eyecare practitioners when purchasing disinfecting solutions (26%) and other hygiene practices. Pseudomonas Aeruginosa was the most common organism grown in 22.4% of patients while 47% of patients were culture-negative. Conclusion: Inadequate lens cleaning, poor aftercare, sleeping and swimming with CL were the major non-compliant behaviours among participants, and these are significant factors when assessing risks in acquiring CL-related infectious keratitis. General eyecare practitioners are the first-line of contact in patients presenting with keratitis symptoms and play an important role in emphasising the need for regular aftercare and good hygiene practices to CL wearers. Key words: Contact lens, Corneal ulcer, Infective keratitis

In vivo biocompatibility of two PEG/PAA interpenetrating polymer networks as corneal inlays following deep stromal pocket implantation

This study compared the effects of implanting two interpenetrating polymer networks (IPNs) into rabbit corneas. The first (Implant 1) was based on PEG-diacrylate, the second (Implant 2) was based on PEG-diacrylamide. There were inserted into deep stromal pockets created using a manual surgical technique for either 3 or 6 months. The implanted corneas were compared with normal and sham-operated corneas through slit lamp observation, anterior segment optical coherence tomography, in vivo confocal scanning and histological examination. Corneas with Implant 1 (based on PEG-diacrylate) developed diffuse haze, ulcers and opacities within 3 months, while corneas with Implant 2 (based on PEG-diacrylamide) remained clear at 6 months. They also exhibited normal numbers of epithelial cell layers, without any immune cell infiltration, inflammation, oedema or neovascularisation at post-operative 6 month. Morphological studies showed transient epithelial layer thinning over the hydrogel inserted area and elevated keratocyte activity at 3 months; however, the epithelium thickness and keratocyte morphology were improved at 6 months. Implant 2 exhibited superior in vivo biocompatibility and higher optical clarity than Implant 1. PEG-diacrylamide-based IPN hydrogel is therefore a potential candidate for corneal inlays to correct refractive error.

Paradigm Shifts in Corneal Transplantation

Conventional corneal transplantation, in the form of penetrating keratoplasty (PK), involves full-thickness replacement of the cornea, and is a highly successful procedure. However, the cornea is anatomically a multi-layered structure. Pathology may only affect individual layers of the cornea, hence selective lamellar surgical replacement of only the diseased corneal layers whilst retaining unaffected layers represents a new paradigm shift in the field. Recent advancements in surgical techniques and instrumentation have resulted in several forms of manual, microkeratome and femto-second laser-assisted lamellar transplantation procedures. Anterior lamellar keratoplasty (ALK) aims at replacing only diseased or scarred corneal stroma, whilst retaining the unaffected corneal endothelial layer, thus obviating the risk of endothelial allograft rejection. Posterior lamellar keratoplasty/endothelial keratoplasty (PLK/EK) involves the replacement of the dysfunctional endothelial cell layer only. Whilst significant technical and surgical challenges are involved in performing lamellar micro-dissection of a tissue which is only 0.5 mm thick, the benefits of a more controlled surgical procedure and improved graft survival rates have resulted in a shift away from conventional PK. This review details the current advances in emerging lamellar corneal surgical procedures and highlights the main advantages and disadvantages of these new lamellar corneal procedures. Key words: Deep anterior lamellar keratoplasty, Descemet’s stripping endothelial keratoplasty, Endothelial keratoplasty, Lamellar keratoplasty, Penetrating keratoplasty

Characterisation of Human Tear Proteins Using High-resolution Mass Spectrometry

Introduction: The proteins found in tears play an important role in maintaining the ocular surface and changes in tear protein components may reflect changes in the health of the ocular surface. Proteomics provides a comprehensive approach for cataloguing all the proteins of the tear proteome, which will help to elucidate disease pathogenesis, make clinical diagnoses and evaluate the influence of medications on the structure, composition and secretion of tear proteins. In this study, an alternative proteomic strategy was investigated to explore the human tear proteome. Materials and Methods: Tear samples were obtained from patients who had pterygium and were collected on the first day and third day after pterygium surgery. Tears pooled from 6 patients were used in the analysis. Reverse-phase high-pressure liquid chromatograph (RP-HPLC) was used as the first step to separate intact proteins into 21 peaks. Each fraction was then tryptic-digested and analysed by nanoLC-nano-ESI-MS/MS to characterise the protein components in each fraction. Results: In total, 60 tear proteins were identified with high confidence, including well-known abundant tear proteins, and tear-specific proteins such as lacritin and proline-rich proteins. Among them, proline-rich protein 5 was found for the first time in tear fluid. A large number of plasma proteins were also observed in tear fluid. Conclusions: The results showed that the proteomic strategy used in this study was successfully applied to analyse tear proteome. Key words: Human tear proteins, Human tear proteome, NanoLC-nanoESI-MS/MS, Tear proteomics

Enhancement of the Mechanical and Biological Properties of a Biomembrane for Tissue Engineering the Ocular Surface

Introduction: In this study, we have developed and optimised a novel gelatin-chitosan (GC) substrate for use as a cellular carrier for tissue-engineered conjunctival epithelium. Materials and Methods: The substrate was fabricated by casting and the mechanical properties of the substrate, including tensile strength and elongation, were measured. Using the MTT, cell proliferation assay with rabbit conjunctival fibroblasts, we optimised the G:C ratio to enhance cytocompatibility. Rabbit conjunctival epithelial cells were immunostained using monoclonal antibodies for keratin 4 and pancytokeratin to investigate the biological effects of the GC substrate on the proliferation and differentiation of epithelial cells. Results: We found that increasing the amount of gelatin resulted in an increase in elasticity (from 1:9 to 1:1 ratio), reaching a maximum (101.89% ± 7.13%) at a ratio of 1:1. The MTT assay showed that the proliferation of conjunctival fibroblasts significantly increased from 0.068 ± 0.017 to 0.177 ± 0.011 (P = 0.014) as the gelatin was increased from 20% (1:4) to 50% (1:1). Additional studies using tissue-cultured conjunctiva explants showed that these explants grew well on the substrate, forming a multilayered epithelium. Cell morphology on this substrate was similar to that of cells grown on culture dishes alone. Positive staining of keratin 4 and pancytokeratin indicated that the substrate supported normal differentiation of conjunctival epithelial cells. Conclusion: By enhancing the proportion of gelatin, both the mechanical and biological properties of the chitosan substrate were improved. The results also suggest that this GC biomembrane may be a useful candidate for reconstructive tissue engineering of the conjunctiva.

Corneal replacement using a synthetic hydrogel cornea, AlphaCor: device, preliminary outcomes and complications

PURPOSE

Clinical assessment of outcome of corneal replacement with a synthetic cornea, AlphaCor, in patients considered at too high risk for conventional penetrating keratoplasty with donor tissue to be successful, but excluding indications such as end-stage dry eye that might be suited to traditional prosthokeratoplasty.

METHODS

All patients in the multicentre clinical trial were managed according to an approved protocol, with Ethics Committee approval in each centre. Preoperative visual acuity ranged from perception of light (PL) to 6/60 (20/200). Implantation was by means of an intralamellar technique, with a conjunctival flap in most cases. Tissues anterior to the optic were removed as a secondary procedure.

RESULTS

Up to 30 November 2001, 40 AlphaCor devices had been implanted in 38 patients, of mean age 60 years. Follow-up ranged from 0.5 months to 3 years. There had been one extrusion (2.5%) and four cases (10%) where a device had been removed due to melt-related complications. All five of these cases received a donor corneal graft after the device was removed, with these grafts remaining anatomically satisfactory and epithelialised to date. Corneal melts in AlphaCor recipients were found to be strongly associated with a history of ocular herpes simplex infection. Two further devices (5%) were removed owing to reduced optic clarity after presumed drug-related deposition, and have been successfully replaced with second devices. Mean preoperative best-corrected visual acuity was hand movements. Visual acuities after surgery ranged from PL to 6/6(-2) (20/20(-2)).

CONCLUSIONS

Early results suggest that the AlphaCor, previously known as the Chirila keratoprosthesis (Chirila KPro), has a low incidence of the complications traditionally associated with keratoprostheses and can be effective in restoring vision in patients considered untreatable by conventional corneal transplantation. Importantly, the device can be replaced with a donor graft in the event of development of a significant complication. A history of ocular herpes simplex is a contraindication to AlphaCor implantation. Ongoing monitoring of clinical outcomes in all patients will allow the indications for AlphaCor, as opposed to donor grafts, to be determined.

Corneal and refractive error astigmatism in Singaporean schoolchildren: a vector-based Javal's rule

BACKGROUND

Traditional approaches to Javal's rule do not use data from subjects with oblique astigmatism and have not been used to make predictions about subjects with oblique astigmatism. Vector approaches to analyzing refractive error can circumvent these problems.

METHODS

Subjects were 993 Singaporean schoolchildren. We performed linear regression of refractive error astigmatism on corneal astigmatism, using J0 vectors to describe with-the-rule and against-the-rule astigmatism and J45 vectors to describe oblique astigmatism.

RESULTS

We obtained the following statistically significant regression relationships: RJ0 = 0.931 x CJ0 - 0.276 and RJ45 = 0.638 x CJ45 + 0.010, where R and C denote refractive error astigmatism and corneal astigmatism, respectively.

CONCLUSION

Our vector-based Javal's rule gives closer predictions of refractive astigmatism than the original Javal's rule and the simplified Javal's rule and can be applied in cases of corneal oblique astigmatism.

Randomized clinical trial of Surodex steroid drug delivery system for cataract surgery: anterior versus posterior placement of two Surodex in the eye

OBJECTIVE

To evaluate safety and antiinflammatory efficacy of placing two Surodex (Oculex Pharmaceuticals, Inc., Sunnyvale, CA) in the eye after cataract surgery in comparison with steroid eyedrops and to compare anterior versus posterior chamber placement.

DESIGN

Randomized, masked, controlled trial.

PARTICIPANTS

One hundred four eyes of 104 Asian patients undergoing extracapsular cataract extraction with intraocular lens implantation were examined. Of these, 33 eyes of 33 patients served as control eyes (group A).

INTERVENTION

Two Surodex pellets were inserted in the anterior chamber (AC) of 35 eyes (group B), and two Surodex pellets were inserted in the ciliary sulcus of 36 eyes (group C) at the conclusion of surgery. Control eyes received neither Surodex nor a placebo implant, but were prescribed conventional 0.1% dexamethasone eyedrops four times daily for 4 weeks.

MAIN OUTCOME MEASURES

Anterior chamber flare and cells were graded clinically at the slit lamp. Anterior chamber flare was assessed objectively with the Kowa FC500 Laser Flare Meter (Kowa Co. Ltd, Tokyo, Japan). Intraocular pressure and corneal endothelial specular microscopy with morphometric cell analysis were performed for up to 1 year after surgery.

RESULTS

Lower flare meter readings occurred in both Surodex groups at all postoperative visits, as compared with the dexamethasone eyedrop group, with statistical significance at days 4 (P = 0.001), 8 (P = 0.001), and 15 (P = 0.02). No difference in flare occurred between AC and ciliary sulcus placement. Clinical slit-lamp assessment of anterior chamber flare and cells showed no difference between Surodex-treated eyes and dexamethasone-treated eyes. Nine of 33 eyes (27.3%) in group A required steroid augmentation, as opposed to 4 of 71 eyes (5.6%) in groups B and C. Inflammatory symptoms were reduced in the Surodex-treated eyes, with statistical significance for ocular discomfort (P = 0.001), photophobia (P = 0.04), and lacrimation (P = 0.01). No complications occurred with Surodex-treated eyes, and no significant difference in endothelial cell loss was noted between Surodex-treated eyes and dexamethasone-treated eyes up to 1 year after surgery.

CONCLUSIONS

Intraocular placement of two Surodex is a safe and effective treatment method to reduce intraocular inflammation after cataract surgery and clearly is superior to eyedrops in reducing inflammatory symptoms and aqueous flare as measured with the laser flare meter. No difference in efficacy between AC placement and ciliary sulcus placement of Surodex was detected in this study.

Therapeutic lamellar keratoplasty for limbal dermoids

PURPOSE

To assess the surgical outcomes of appearance, vision, refraction, and graft survival and integrity in patients with histologically proven limbal dermoid choristomata who underwent lamellar keratoplasty.

DESIGN

Retrospective noncomparative analysis of a consecutive case series with patient recall and examination.

PARTICIPANTS

Eleven patients (six female, five male, median age, 9.6 years; range, 1-29 years) with 12 limbal dermoids in 11 eyes operated on between 1995 and 1998 were identified from the eye bank database at the Singapore National Eye Centre.

METHODS

Case records, photographs, and eye bank data were examined. Patients not already seen by the authors within the previous 3 months were recalled and examined.

OUTCOME MEASURES

Descriptive data: size and location of the dermoid, presence of lipid keratopathy; visual acuity; refraction and astigmatism, vector analysis, surgically induced refractive change; corneoscleral and limbal match, haze, vascularity; graft integrity, clarity, vascularization, and rejection episodes.

RESULTS

Most (7 of 11) patients had single inferotemporal limbal dermoids, although one patient had two dermoids in one eye. Median follow-up time was 21.6 months (range, 9.0-46.4 months). Most (8 of 11) patients had good or excellent cosmetic results with minimal interface haze and no vascularization. Two cases with previously excised lesions had postoperative vascularization develop. One of these cases had graft infection develop, underwent subsequent debridement, and has an opaque graft. Best-corrected visual acuity was maintained or slightly improved in 9 of 11 patients. For the group and most individual patients, mean astigmatism, spherical equivalent, and refraction, as assessed by surgically induced refractive change and h-vector analysis, were not significantly changed.

CONCLUSION

Lamellar keratoplasty as primary surgery for limbal dermoids gave good cosmetic results. However, improvement in refractive, astigmatic, and visual status is not guaranteed, and these procedures should be viewed more cautiously, although established good vision was maintained in our series.

Therapeutic use of Bausch & Lomb PureVision contact lenses

PURPOSE

To evaluate the Bausch & Lomb PureVision contact lens as a continuous wear contact lens for therapeutic indications in a prospective open-ended non-randomized clinical trial.

METHODS

Patients with a variety of corneal and ocular surface disease conditions presenting at the Singapore National Eye Centre who required therapeutic continuous contact lens wear were enrolled. Therapeutic indications included pain relief, corneal protection, and enhancement of corneal wound healing. Success or failure of specific treatment indications was assessed in all cases, with evaluation of lens performance and fit characteristics, and the presence of ocular complications or lens-related complications was noted.

RESULTS

There were 54 patients (54 eyes), and the mean duration of continuous contact lens wear was 1.1 months. Conditions treated included post-surgical indications (n = 36) (post-keratoplasty or ocular surface transplantation, post-LASIK or PRK surgery) bullous keratopathy (n = 7), chemical burns (n = 3), epithelial abrasions or recurrent corneal erosion syndromes (n = 3), corneal perforations (n = 3), neurotrophic ulcer (n = 1), and corneal laceration (n = 1). For the indication of corneal healing (40 eyes), improved healing was noted in 38 eyes (96%), with full healing occurring in 33 eyes (83%). For pain relief (28 eyes), 27 patients (96%) had considerable or complete pain relief, and the remaining patient reported partial pain relief. For corneal protection (21 eyes), lens wear was fully protective in all cases. The lens performance and fitting characteristics surpassed any previous therapeutic lenses used by the investigators. Complications related to contact lens wear were limited to one case of a culture-negative corneal infiltrate requiring cessation of therapeutic lens wear and one case of a loosely fit lens.

CONCLUSIONS

Our results show that the PureVision contact lens exhibits good safety and efficacy when utilized as a continuous wear therapeutic lens. With the theoretical advantage of increased oxygen transmissibility reducing the risk of hypoxia-related complications, this new lens may be one step closer to the ideal therapeutic contact lens. The PureVision contact lens is now our primary bandage lens of choice in our corneal, external disease, and refractive surgery services.

Patient reliability in the administration of topical ocular medication

PURPOSE

To evaluate patient's reliability in the administration of eyedrops.

METHOD

The study is based on a randomised, controlled clinical trial in which a steroid-containing drug delivery system (DDS) was directly compared to conventional steroid eyedrops after cataract surgery. 32 eyes undergoing extracapsular cataract extraction with intra-ocular lens insertion received a DDS, while 31 eyes received 0.1% dexamethasone eyedrops q.d.s for 30 days. Patients with DDS were given a placebo eyedrop in the form of 0.9% sodium chloride, while all 63 eyes received topical chloramphenicol eyedrops q.d.s for 30 days. At the conclusion of the 30 day visit, the eyedrop containers were collected and the residual volume of medication remaining in each bottle was then measured to the nearest 10 microlitre using a pipette.

RESULTS

31 patients returned the complete set of eyedrop containers. There was no statistical significant difference in the volume used between the types of eyedrops, sex and diabetic status. All the patients used more than the prescribed amount. Older patients tended to use less medication.

CONCLUSION

The amount of medication that patients actually administered in this trial varied widely according to the individual, and patient age may be a factor affecting compliance in using eyedrops.

Recurrent corneal erosion after laser in situ keratomileusis

PURPOSE

To describe how laser-assisted in situ keratomileusis (LASIK) may induce recurrent corneal erosion (RCE) syndrome and the preventive measures for avoiding this complication. METHODS. A case series was used.

RESULTS

We report the development of RCE syndrome in eight eyes of six patients after LASIK. In five cases, the RCE was triggered by epithelial trauma at the time of the LASIK procedure, as evidenced by the observation of RCE occurring at the same site as the initial epithelial disturbance. In case 6, RCE occurred with undiagnosed basement membrane dystrophy. The patients responded to treatment with ocular lubricants with one patient undergoing penetrating keratoplasty for RCE after LASIK.

CONCLUSION

LASIK can induce or precipitate RCE, and RCE should perhaps be included as a potential complication in the informed consent process. It is important to minimize epithelial damage to prevent RCE after LASIK, and measures to reduce this include adequate irrigation of the corneal surface immediately before the microkeratome pass and careful attention to flap epithelium during flap replacement. Cases in which loose epithelium is noted after LASIK should be identified as potential RCE cases, and extra care should be taken for subsequent enhancement procedures or LASIK of the second eye.

Short-term small-dose intravenous iron trial to detect functional iron deficiency in dialysis patients

BACKGROUND/AIM

Management of renal anemia in end-stage renal disease requires careful evaluation of the iron status before and in particular during erythropoietin treatment. However, there is no simple and practical iron index accurately predictive of functional iron deficiency in these patients till now. The purpose of this prospective study, therefore, is to evaluate whether a short course of low-dose intravenous iron challenge can detect functional iron deficiency in hemodialysis patients.

METHODS

Twenty-four patients with baseline serum ferritin levels between 100 and 500 ng/ml were treated with intravenous saccharated ferric oxide, 960 mg over 24 hemodialysis treatments, and the hemoglobin level was checked every week.

RESULTS

Patients whose hemoglobin value increased at least by 1 g/dl within the 8-week period were classified as having functional iron deficiency or as responders (n = 26; 81.2%). All other subjects were classified as having adequate iron levels or as nonresponders (n = 6; 18.8%). There were no significant differences in age, sex, dialysis years, Kt/V, dialyzers, hemoglobin, and basal and final transferrin saturation and ferritin between responders and nonresponders. In addition, there were no iron indices with acceptable levels of sensitivity and specificity. On the contrary, the cutoff value of increments of hemoglobin of at least 0.2 g/dl after a 2-week intravenous iron trial had a sensitivity of 96.2% and a specificity of 100% in all patients (n = 32) and a sensitivity of 100% and a specificity of 100% after patients with transferrin saturation <20% were excluded (n = 24). These values had the greatest utility of the tests studied in this work.

CONCLUSION

A 240-mg intravenous iron challenge during a 2-week period may be a simple, accurate, and straightforward method to detect a functional iron deficiency status in hemodialysis patients undergoing erythropoietin therapy.

Vascular patterns in pterygium and conjunctival autografting: a pilot study using indocyanine green anterior segment angiography

AIMS

To characterise the vasculature of pterygium using indocyanine green (ICG) anterior segment angiography and to demonstrate the pattern of revascularisation following conjunctival autografting.

METHODS

ICG anterior segment angiography was performed on nine patients with pterygium. Angiography was repeated at 1-2 weeks and 2 months following conjunctival autografting in these patients.

RESULTS

Angiography showed a single feeder vessel originating from the anterior conjunctival circulation in six cases (66.7%). This vessel branched to form the radial vessels of the pterygium. Following conjunctival autografting, reperfusion of the vessels in the conjunctival autograft was demonstrable as early as 1 week postoperatively from the episcleral bed. At 2 months postoperatively, the graft appeared well perfused with mild leakage demonstrable at the edges of the graft.

CONCLUSIONS

A single feeder vessel from the anterior conjunctival circulation branches to form the radial vessels in pterygium. Reperfusion of conjunctival autografts occurs as early as 1 week postoperatively from the episcleral bed.

The prevalence and risk factors for pterygium in an adult Chinese population in Singapore: the Tanjong Pagar survey

PURPOSE

To determine the prevalence and risk factors for pterygium in the Chinese population of Singapore.

METHODS

A population-based survey was conducted in Singapore, an island located 1 degree north of the equator with a stable tropical climate. A disproportionate, stratified, clustered, random sampling procedure was used to select the names of 2000 Chinese people aged 40 to 79 years from the 1996 electoral register in the Tanjong Pagar district of Singapore. Selected subjects underwent a comprehensive interview and ocular examination. Pterygium was diagnosed and graded clinically as grade 1 (transparent), 2 (intermediate), and 3 (opaque). Risks factors associated with pterygium and grade 3 pterygium were evaluated with logistic regression models.

RESULTS

From a total of 1717 eligible subjects, 1232 (71.8%) were examined. There were 120 people with either unilateral (n = 70) or bilateral (n = 50) pterygium, equivalent to an overall prevalence of 6.9% (95% confidence interval [CI], 5.2, 8.8) in the Chinese population aged 40 and older. The prevalence increased linearly with age (chi-square test of trend P <.001) and was higher among men than women (age-adjusted odds ratio [OR], 4.2; 95% CI, 2.5, 6.9). Men aged 70 and above had the highest overall prevalence of 25.4% (95% CI, 18.2, 19.4), but pterygium was not seen in women aged 40 to -49 years. In multivariate analysis, ptergyium was independently associated with increasing age (OR, 7.8; 95% CI, 3.2, 18.8 for persons 70 to 81 years, compared with 40 to 49 years), male sex (OR, 5.1; 95% CI, 2.9, 9.3) and certain occupations; factory workers, production workers and machine operators (OR, 3.1; 95% CI, 1.5, 6.3), as well as laborers and agricultural workers (OR, 3.3; 95% CI, 1.6, 7.0) had higher risks, compared with professionals and office workers. Grade 3 pterygium (n = 36) was also independently associated with male sex (OR, 11.6; 95% CI, 3.5, 38.6) and similar occupations but was not related to age.

CONCLUSIONS

The prevalence of pterygium in Singapore is 7% among Chinese aged 40 years and older. Independent associations with increasing age, male sex, and occupations linked to outdoor work and other exposures suggest a multifactorial cause of this condition.

Environmental lead exposure and progressive renal insufficiency

BACKGROUND

Several recent studies show that serum creatinine level or creatinine clearance is inversely associated with blood lead levels. However, the studies did not allow direct inferences about causality.

OBJECTIVE

To evaluate the relation between body lead burden (BLB) and progressive renal insufficiency in patients without previous heavy lead exposure.

DESIGN

A prospective, longitudinal study with a controlled clinical trial.

PATIENTS

One hundred ten patients with chronic renal insufficiency (serum creatinine level, 133-354 micromol/L [1.5-4.0 mg/dL]) and normal BLB (EDTA mobilization tests, <600 microg per 72-hour urine collection) and without a history of previous heavy lead exposure were divided into 2 groups according to BLB: the high-normal BLB group (BLB > or =80 microg and <600 microg) and the low BLB group (BLB <80 microg). Patients were prospectively followed up for 2 years.

MAIN OUTCOME MEASURES

The primary outcome was a 1.5 times increase in the initial creatinine level. The secondary outcome was a change over time in the value of creatinine clearance. At the end of follow-up, a 3-month clinical trial with chelation therapy for patients with high-normal BLB was performed to clarify the role of environmental lead exposure in progressive renal insufficiency.

RESULTS

Fifteen patients (14 in the high-normal BLB group and 1 in the low BLB group) reached the primary outcome within 24 months. Renal outcome was significantly better in the low BLB group (P<.001). From month 12 to month 24, renal function of high-normal BLB patients had a greater rate of progressive renal insufficiency than that of low BLB patients. In the Cox multivariate regression analysis, BLB was the most important risk factor for determining the progression of renal insufficiency. After chelation therapy, significant improvement in renal function was noted. In addition, the effect of improving renal function lasted for more than 12 months in these patients.

CONCLUSIONS

Long-term low-level environmental lead exposure may subtly affect progressive renal insufficiency in the general population. Progressive renal insufficiency may be improved for at least 1 year after lead chelating therapy. Further investigations are needed to clarify this observation.

Effect of splanchnectomy on jejunal motility and fos expression in brain stem after intestinal anaphylaxis in rat

This study was to determine whether alterations in jejunal motility observed after antigen challenge of sensitized rats occurred after extirpation of the celiac-superior mesenteric ganglia. Hooded-Lister rats were prepared with an intact or extirpated celiac-superior mesenteric ganglion, an isolated Thiry-Vella loop of ileum for instillation of antigen, and jejunal electrodes for myoelectric recording. Animals were sensitized by injection of 10 microg egg albumin (EA, ip), and specific anti-EA IgE titers were determined to be >1:64. In both control and splanchnectomized rats, normal fasting migrating myoelectric complexes (MMC) were observed before challenge with EA. MMCs were disrupted, and diarrhea was observed immediately after EA challenge of control but not splanchnectomized animals. Brain stems were removed and processed for Fos immunoreactivity. The absence of perivascular neuropeptide Y immunoreactivity in the submucosa was used to confirm the success of splanchnectomy. The number of Fos-immunoreactive neuronal nuclei was significantly reduced in the brain stem after splanchnectomy. Thus the mesenteric sympathetic ganglia are an integral part of the extramural neuronal pathways required for altered motility in this model of intestinal anaphylaxis.

High-pressure paint gun injury to the orbit and ocular adnexa

High-pressure injection injury to the orbit and adnexa is a rare but potentially blinding type of trauma. Few cases of such injury have been reported in the literature. A 27-year-old Indian man accidentally injected paint material from a high-pressure nozzle gun into his left eye. Radiological investigation revealed the presence of paint material in the orbital tissues and the ethmoidal sinuses. The patient underwent two orbital surgeries to remove the paint material. He later developed signs suggestive of limbal stem cell failure and was treated with limbal stem cell autografting. He also has ophthalmoplegia with a compensatory anomalous head posture that was managed conservatively. We report the clinical course and outcome of this unfortunate patient to highlight the complexity of such an injury and the need for a multidisciplinary approach in its management.

Necrotising scleritis after bare sclera excision of pterygium

AIM

To report cases of scleral necrosis after simple pterygium excision in which adjunctive treatment was not used.

METHODS

We reviewed four patients who presented with scleral melt after pterygium excision without the use of adjunctive treatment in the form of beta irradiation, mitomycin C, or thiotepa. Each patient was thoroughly investigated to exclude underlying disease.

RESULTS

Certain similarities were found between our patients with pterygium melt and cases of surgically induced necrotising scleritis including the location of melt, associated inflammation, and its response to steroid treatment in the latent period before they presented.

CONCLUSION

Bare sclera pterygium excision can cause surgically induced necrotising scleritis years after the surgery.

Flow cytometry measurements of DNA content in primary and recurrent pterygia

PURPOSE

To evaluate DNA content and cellular proliferation rates in primary and recurrent pterygia.

METHODS

Matched pterygium and superior conjunctiva tissue were obtained in 36 eyes of 36 patients undergoing pterygium excision with conjunctival autografting (24 primary pterygia, 12 recurrent pterygia). Epithelial and fibrovascular layers were separated for analysis. Matched superior conjunctiva obtained at the time of surgery were used as controls. Samples were prepared according to Thompson's method, and flow cytometry was performed with a Becton-Dickinson FACScan. Analysis of histograms and calculations of cell percentages in cell cycle phases were carried out using CellFit software (version 2.0). Mean proliferation indices (MPIs) were compared using the Wilcoxon matched-pair signed-rank test.

RESULTS

The MPI of pterygium fibrovascular tissue (13.4) was significantly higher than the MPI of pterygium epithelium (3.1; P = 0.0001). The MPI of pterygium fibrovascular tissue was also significantly higher than that of superior conjunctival fibrovascular tissue (6.0; P = 0.0001). There was no difference in MPI values between pterygium epithelium and superior conjunctival epithelium (3.55; P = 0.12). The MPI of fibrovascular tissue from recurrent pterygium (73.75) was significantly higher than the MPI of fibrovascular tissue from primary pterygium (7.3; P = 0.003).

CONCLUSIONS

The finding of high levels of cellular proliferation in the subepithelial fibrovascular layer of pterygium confirms that pterygium is a disorder of excessive cellular proliferation and that the fibrovascular layer is the site of cellular proliferation. Markedly raised levels of cellular proliferation in recurrent pterygium tissue suggest a clinical correlation between fibrovascular tissue upregulation and pterygium recurrence after surgery.

Reverse geometry contact lens wear after photorefractive keratectomy, radial keratotomy, or penetrating keratoplasty

PURPOSE

To determine if a super diffusion coefficient of lens/lens thickness (Dk/L) reverse geometry gas permeable (steep peripheral and flatter central curve) contact lenses can be successfully worn after excimer photorefractive keratectomy (PRK), radial keratotomy (RK), or penetrating keratoplasty (PK).

METHODS

Patients with residual ametropia after PRK, RK, or PK were fitted with reverse geometry lenses (Plateau lens in SF-P material; Menicon USA, Inc, Clovis, CA, U.S.A.). Contact lens fit characteristics and comfort were assessed. Lens centration, visual quality, and ocular surface status were graded and visual acuity charted.

RESULTS

Thirteen eyes of 11 patients were fitted; eight eyes with PRK, one eye with RK, and four eyes with PK previously performed. The mean follow up of the patients was six months. The visual acuity prior to lenses ranged from 6/12 to counting fingers, and the acuity with lenses ranged from 6/6 to 6/30. Eight of the 11 patients wore the lenses the whole day without problems; 3 patients discontinued lens wear due to discomfort or unsatisfactory vision.

CONCLUSIONS

The combination of super Dk/L and reverse geometry lenses facilitate lens wear and is associated with good visual acuity.

Effect of food-simulating liquids on the flexural strength of composite and polyacid-modified composite restoratives

This study investigates the effects of food-simulating liquids on composite and polyacid-modified composite restoratives. Three composite (Z100, Spectrum TPH, and Tetric Ceram) and three polyacid-modified composite (F2000, Dyract AP, and Compoglass) restoratives from the same manufacturers were selected for the study. Flexural strength specimens (25 x 2 x 2 mm) based on ISO 4049 specifications were fabricated according to the manufacturers recommendations. After light polymerization, the specimens were removed from their molds and conditioned for one week at 37 degrees C in the following mediums: (1) deionized water, (2) 0.02 M citric acid, (3) heptane, and (4) 50% ethanol-water solution. Specimens stored in air were used as controls. The sample size was five for each material-medium combination. After conditioning, the specimens were blotted dry, measured, and subjected to flexural strength testing using an Instron Universal Testing Machine with a crosshead speed of 0.05 mm/minute. With the exception of Compoglass, flexural strength of all restoratives after conditioning in heptane was significantly greater than that after conditioning in all other mediums and the control. Although no significant difference in flexural strength values was observed between the different restoratives when the materials were conditioned in heptane or air (control), significant differences were observed between the different restoratives after conditioning in aqueous solutions (water, citric acid, and ethanol-water solution). The flexural strengths of the composites were generally significantly higher than their polyacid-modified counterparts after conditioning in the various aqueous solutions. The detrimental effects of aqueous solutions on flexural strength appeared to be greater with polyacid-modified composite resins than with composite restoratives.

Suppression of TGF-beta signaling in both normal conjunctival fibroblasts and pterygial body fibroblasts by amniotic membrane

PURPOSE

When used as an alternative substrate following bare sclera removal of pterygium and other ocular surface diseases, amniotic membrane transplantation can reduce scarring on the reconstructed conjunctival surface. This study was carried out to determine if the amniotic membrane (AM) suppresses the expression of the TGFb signaling system in cultured normal conjunctival (HCF) and pterygial body fibroblasts (PBF).

METHODS

HCF and PBF were cultured on AM and plastic wells in serum-containing and serum-free DMEM with or without TGF-beta1. Total RNA was extracted and subjected to Northern hybridization with probes of TGF-beta1, b2 and b3; TGF-beta receptors (TGF- beta R) type I, II and III; a-smooth muscle actin (alpha-SM), b1-integrin, CD44, fibroblast growth factor receptor 1 (FGF-R1/ flg) and platelet-derived growth factor receptor b (PDGFR-beta); and GAPDH as a loading control. MTT assay was used for cell proliferation.

RESULTS

Amniotic membrane markedly suppressed the transcript expression of TGF-beta2, b3 and all three types of TGF-beta receptors by both fibroblasts as compared to their cultures on plastic surface. In addition, expression of CD44 transcript was also markedly suppressed while that of b1 integrin, a-SM actin, and FGFR1/flg was mildly suppressed. In contrast, expression of TGF-beta1 and PDGFR-beta remained largely unchanged. The cell proliferation of HCF and PBF grown on AM was also significantly suppressed.

CONCLUSIONS

Amniotic membrane matrix uniquely suppresses TGF- beta signaling in both types of fibroblasts. It may also suppress signaling via CD44, b1 integrin and FGFR1/flg. As a result, the phenotype may become less mitogenic, contractile and fibrogenic. These data support in part why amniotic membrane transplantation has an anti-scarring effect for conjunctival surface reconstruction.

Analysis of variation in success rates in conjunctival autografting for primary and recurrent pterygium

AIMS

To evaluate the success rates of conjunctival autografting for primary and recurrent pterygium performed in a tertiary ophthalmic centre.

METHODS

The outcome of 139 cases with primary pterygia and 64 cases with recurrent pterygia who underwent excision with conjunctival autografting was retrospectively reviewed. Outcome was evaluated in terms of recurrence of pterygia onto the cornea. The recurrence rates were determined using Weibull survival functions, in a mixture model that included a component allowing for cure. The suitability of this model was verified using Turnbull's non-parametric method for interval censored data (1974). Estimated recurrence free probabilities were based on the fitted Weibull survival curves.

RESULTS

Mean follow up was 8.4 months in the primary group, and 9.5 months for the recurrent group. 29 out of 139 cases of primary pterygia recurred (20.8%) while 20 out of 64 cases in the recurrent group (31.2%) recurred. Recurrence rates varied widely among surgeons, ranging from 5% to 82%. Recurrence rates were inversely related to previous experience in performing conjunctival grafting. The recurrence free probability was 84% at 3 months, 73% at 1 year for primary pterygia, and 80% at 3 months, 67% at 1 year for recurrent pterygia. There was no statistical difference in recurrence rates between primary and recurrent groups (p= 0.80).

CONCLUSION

The success of conjunctival autografting for pterygium in this series varies widely, and may be related to a significant learning curve or differing surgical techniques for this procedure. This may account for the wide variation in reported success of this procedure in the ophthalmic literature.

Apoptosis and apoptosis related gene expression in normal conjunctiva and pterygium

BACKGROUND

Pterygium is a relatively common eye disease in the tropics whose aetiology and pathogenesis remain uncertain. As such, interest has focused on understanding the underlying mechanism of pterygia development.

METHODS

15 specimens of pterygia from 15 eyes were examined, together with normal conjunctival tissue from the same eyes for the pattern of gene expression of genes associated with the induction or repression of apoptosis (p53, bcl-2, and bax). In addition, the samples directly for apoptotic cells were examined by the terminal deoxynucleotide transferase (TdT) mediated nick end labelling (TUNEL) methodology.

RESULTS

In pterygia specimens apoptotic cells were found mainly confined to the basal layer of cells of the epithelial layer, situated immediately adjacent to the fibrovascular support layer. These cells were shown to express significant levels of p53 and bax, as well as the apoptosis inhibiting protein bcl-2. In contrast, normal conjunctival specimens displayed no bcl-2 expression and apoptotic cells were seen throughout the entire width of the epithelial layer, coupled with high levels of bax expression.

CONCLUSION

These results support a model whereby pterygia development is a result of disruption of the normal process of apoptosis occurring in the conjunctiva.

Lamellar corneal autograft for corneal perforation

BACKGROUND

Corneal perforation secondary to exteriorization of the haptic foot of the anterior chamber intraocular lens (IOL) is a rare complication in IOL surgery.

CASE REPORT

A superior penetrating corneal defect developed in the right eye of a 74-year-old woman associated with exteriorization of the superior haptic of an anterior chamber IOL.

METHODS

We describe the technique of repositioning and successful patching of the defect using a lamellar cornea-sclera rotational autograft.

CONCLUSIONS

This technique is useful for small perforations when cornea donor tissue is not available.

Excimer laser phototherapeutic keratectomy for recurrent corneal erosions

The purpose of this paper was to review the Singapore National Eye Centre's (SNEC) experience with excimer laser phototherapeutic keratectomy (PTK) for treating recurrent corneal erosions (RCE). Thirty-five eyes of 32 patients who had PTK between 1992 and 1997 in SNEC were studied retrospectively. There was a history of previous ocular trauma in 15 eyes. Sixteen eyes had anterior corneal dystrophy. All had received conventional therapy without improvement in symptoms. The mean duration of symptoms prior to PTK was 19 months (range 1 to 71 months). PTK was performed with one of two 193 nm excimer lasers (Summit UV200LA, Summit Technology, Waltham, USA or Visx 20/20B, Visx Corp, Santa Clara, USA). An average of 30 laser pulses were delivered to Bowman's membrane after debridement of the corneal epithelium. The mean follow-up time was 12 months (range 0 to 56 months). Among those with adequate length of follow-up, 26/27 eyes (96%) were symptom-free for 3 months, 19/22 eyes (86%) were symptom-free for 6 months and 9/13 eyes (69%) were symptom-free for 1 year. Three eyes had repeat PTK. Mild corneal haze was seen in 3 eyes. No visually threatening complications were encountered. PTK is a safe and effective procedure for RCE refractory to conventional treatment.

Amniotic membrane transplantation for symptomatic bullous keratopathy

OBJECTIVE

To determine whether amniotic membrane transplantation can be used to treat symptomatic bullous keratopathy displaying poor visual potential.

METHODS

Amniotic membrane transplantation was performed at 5 centers on 50 consecutive eyes (50 patients) with symptomatic bullous keratopathy and poor visual potential. The underlying causes of bullous keratopathy included aphakia (9 eyes), pseudophakia (19 eyes), failed grafts (9 eyes), and others (13 eyes).

RESULTS

During the follow-up period of 33.8 weeks (3-96 weeks) after amniotic membrane transplantation, 43 (90%) of 48 eyes with intolerable pain preoperatively became pain free postoperatively. Among the 5 eyes with residual pain, 3 received repeated amniotic membrane transplantation, 1 required a conjunctival flap for pain relief, and 1 had reduced pain. Epithelial defects in 45 (90%) of 50 eyes created and covered by amniotic membrane healed rapidly within 3 weeks. Only 4 eyes (8%) showed recurrent surface breakdown. Epithelial edema or bullae recurred in a smaller area in 5 eyes (10%) and pseudopterygium developed in 1 eye.

CONCLUSION

Amniotic membrane transplantation can be considered as an alternative to conjunctival flaps in alleviating pain, promoting epithelial healing, and preserving cosmetic appearance in patients with symptomatic bullous keratopathy and poor visual potential.

Contact lens wear after photorefractive keratectomy: comparison between rigid gas permeable and soft contact lenses

PURPOSE

To determine if rigid gas permeable (RGP) or soft contact lenses can be successfully worn after photorefractive keratectomy (PRK) to correct residual refractive errors.

METHODS

Patients with residual stable ametropia after PRK were fit with RGP or soft lenses. Manifest refraction, corneal topography, and keratometry were performed, and post-PRK corneal haze was graded during the study visits. Contact lens fit characteristics and comfort were assessed. Lens centration, visual quality, and ocular surface status were graded, and visual acuity with contact lenses was charted.

RESULTS

Eighteen patients were recruited for RGP lens fitting. The mean refractive error post-PRK was +0.80 D +/- 2.03 (range: -3.50 to+3.00 D). The mean contact lens power was -3.90 D +/- 2.03 (range: 0 to -7.00 D), and the mean contact lens base curve was 7.88 mm +/-0.16. A significant positive tear film at the site of the central ablation was noted, contributing to excessive minus lens power in all cases. Despite mild to moderate lens instability and de-centration, 14 patients reported excellent visual quality with the lenses, and pre-PRK best-corrected acuity was achieved in all patients. Twenty-five percent (4 of 16) of the patients were able to wear the lenses all day. Eleven patients were recruited for soft contact lens fitting-five from the RGP trial. The mean refractive error post-PRK was -0.64 D +/- 2.01 (range: -3.50 to +1.75D). The mean contact lens power was -0.60 D +/- 2.07 (range: -3.75 to +2.5 D), and the mean contact lens base curve was 8.33 mm +/- 0.42. Eight patients were corrected with lenses to their pre-PRK best-corrected acuity, and nine patients reported excellent visual quality with the lenses. All the patients had excellent lens centration. Thirty-six percent (four of 11) of patients were wearing the lenses all day.

CONCLUSIONS

Fitting RGP lenses after PRK results in good visual acuity but may be associated with mild to moderate lens instability and decentration. Soft contact lens fitting also results in good visual acuity. Soft lenses were better tolerated by the subjects in our study because of improved lens centration and stability.

Postoperative inflammation: extracapsular cataract extraction versus phacoemulsification

PURPOSE

To quantitatively compare postoperative inflammation after extracapsular cataract extraction (ECCE) with that after phacoemulsification in an Asian population.

SETTING

Singapore National Eye Center, Singapore.

METHODS

In this prospective, randomized, double-masked clinical trial, patients having cataract surgery were randomized to receive ECCE (n = 16) or phacoemulsification (n = 18). Diabetics were excluded. Two surgeons performed both types of surgery and implanted a 6.0 mm optic intraocular lens. Inflammation was assessed qualitatively by slitlamp grading of cells and flare and quantitatively using the Kowa flare meter. One independent postoperative investigator performed the slitlamp examination and laser flare meter readings.

RESULTS

The ECCE and phacoemulsification groups were comparable (P > .05) in age, sex, ethnicity, and preoperative flare levels. The combined slitlamp inflammatory scores (anterior chamber cells and flare) and mean laser flare meter readings showed the ECCE group had significantly higher mean flare measurements than the phacoemulsification group at days 4 (P = .0012), 8 (P = .0013), 15 (P = .0013), 30 (P = .0004), and 60 (P = .0164). Flare levels in the ECCE group returned to preoperative values by the second month; the phacoemulsification group achieved preoperative levels by 1 month. The clinical inflammatory assessment score correlated closely to the flare level readings.

CONCLUSION

Phacoemulsification induced less inflammation than ECCE, with the difference most marked in the first month after surgery.

Undernournishment and Yersinia enterocolitica enterocolitis alter intestinal contractility in the rabbit: role of smooth muscle contractile protein content

Previous studies have demonstrated that the longitudinal smooth muscle of rabbits infected with Yersinia enterocolitica and undernourished because of reduced food intake exhibit a significantly reduced ability to develop tension in response to carbachol compared with pair-fed animals, which are uninfected but equivalently undernourished. To determine whether the alteration in smooth muscle contractility results from changes in cell number (hypo- or hyperplasia), or in contractile protein content or isoform distribution, New Zealand White rabbits (600 to 1000 g) were randomly assigned to one of three treatment groups: infected, pair-fed or control. Tissue contractility was measured, morphometric studies were performed and immunoassays were developed for the measurement of total actin, gamma-enteric and alpha-vascular isoactins, and myosin heavy chain. Consistent with what was found in previous reports, the contractility of longitudinal smooth muscle in response to carbachol was found to increase in pair-fed animals and to decrease in Y enterocolitica-infected animals. There was no significant change in the proportional thickness of the ileal longitudinal smooth muscle coat, and the number of cross-sectioned longitudinal smooth muscle cells/mm2 was not significantly different in infected, pair-fed or control tissues. Immunoassay indicated that the proportion of each specific contractile protein, relative to total protein content in the muscularis propria, was unaffected by Y enterocolitica infection or by pair-feeding. Thus, the alterations in intestinal longitudinal smooth muscle function observed after Y enterocolitica infection were concluded not to be associated with tissue hypo- or hyperplasia, or changes in the total content or isoform distribution of contractile proteins in the muscularis propria.

Randomized clinical trial of a new dexamethasone delivery system (Surodex) for treatment of post-cataract surgery inflammation

OBJECTIVE

To evaluate the safety of Surodex Drug Delivery System (Oculex Pharmaceuticals, Inc., Sunnyvale, CA) containing dexamethasone 60 micrograms, for use in cataract surgery, and to compare its anti-inflammatory efficacy with conventional dexamethasone 0.1% eyedrops.

DESIGN

Randomized, masked, and partially controlled trial.

PARTICIPANTS

Sixty eyes of 60 Asian patients undergoing extracapsular cataract extraction with intraocular lens implantation were examined. Of these, 28 eyes of 28 patients served as control eyes. Patients were stratified for age and presence of diabetes mellitus.

INTERVENTION

Surodex was inserted in the anterior chamber of 32 eyes at the conclusion of surgery. These eyes received placebo eyedrops four times a day after surgery for 4 weeks. Control eyes received neither Surodex nor a placebo implant but were prescribed conventional 0.1% dexamethasone eyedrops four times a day for 4 weeks.

MAIN OUTCOME MEASURES

Anterior chamber cells and flare were clinically graded at the slit lamp. Anterior chamber flare was objectively assessed with the Kowa FM500 Laser Flare Meter (Kowa Co. Ltd, Tokyo, Japan) for up to 3 months after surgery. Intraocular pressure and corneal endothelial specular microscopy with morphometric cell analysis were performed for up to 1 year after surgery.

RESULTS

Clinical slit-lamp assessment of anterior chamber flare and cells showed no difference between Surodex-treated eyes and dexamethasone eyedrop-treated eyes. Flare meter readings showed lower flare levels in the Surodex group at all postoperative visits compared with the dexamethasone eyedrop group. Flare reduction in the Surodex group reached statistical significance at days 4, 8, 15, and 30 after surgery. At 3 months, flare was reduced to preoperative levels in the Surodex group but was still raised in the dexamethasone eyedrop group. Five eyes in the dexamethasone eyedrop group required augmentation of steroids and were deemed therapeutic failures as opposed to one eye in the Surodex group. One patient in the dexamethasone eyedrop group developed postoperative open-angle glaucoma with profound visual field loss and optic disc cupping, resulting in hand movements vision. No significant difference in endothelial cell loss was noted between Surodex-inserted eyes and dexamethasone eyedrop-treated eyes for up to 1 year after surgery.

CONCLUSIONS

Intraocular placement of a single Surodex is a safe and effective treatment method to reduce intraocular inflammation after cataract surgery. There was no statistical difference in efficacy between Surodex and 0.1% dexamethasone eyedrops in reducing intraocular inflammation, as measured by clinical methods, while Surodex was clearly superior to eyedrops in reducing aqueous flare as objectively assessed with the laser flare meter.

Conjunctival rotation autograft for pterygium. An alternative to conjunctival autografting

OBJECTIVE

To determine the safety and efficacy of conjunctival rotation autografting (CRA) as an alternative to conventional conjunctival autograft after pterygium excision.

DESIGN

Prospective noncomparative case series.

PARTICIPANTS

Consecutive patients seen at the Pterygium Clinic of the Singapore National Eye Centre who were thought to be unsuitable for conventional conjunctival autografting underwent a modified surgical procedure, which the authors describe as CRA. There were 51 rotation autografts performed on 45 eyes of 43 patients.

INTERVENTION

In this procedure, the underlying fibrovascular pterygium tissue was removed and the original epithelium (with minimal subepithelial tissue included) replaced over the bare sclera with a 180 degrees rotation. Surgeries were performed by one surgeon (DT) from April 1995 to May 1996.

MAIN OUTCOME MEASURE

Pterygium recurrence and complications of CRA were measured.

RESULTS

The mean follow-up time was 12 months (range, 2-22 months). There were 46 primary and 5 recurrent pterygia. The indications for CRA were combined cataract and pterygium surgery (39.2%), double pterygia (31.4%), the need to preserve the superior conjunctiva (21.6%), and superior conjunctival scarring (7.8%). There were two recurrences (4% recurrence rate), one occurring at 4 months and the other occurring at 7 months after surgery. No significant complications were encountered. However, 50% of the grafts remained mildly injected for more than 3 months, and some remained injected for up to 13 months after surgery (average of 4 months). Pigmentary changes were also noted in six grafts (12%).

CONCLUSION

Conjunctival rotation autografting is a useful technique of conjunctival grafting in cases in which it is not possible or desirable to use the superior conjunctiva as a donor source.

Altered migrating myoelectrical complex in an animal model of cholesterol gallstone disease: the effect of erythromycin

BACKGROUND

The ground squirrel on a high cholesterol diet exhibits prolonged intestinal transit, a pathogenetic factor in cholesterol gallstone formation.

AIMS

To examine the effect of a high cholesterol diet on the characteristics of the migrating myoelectrical complex (MMC) and the potential benefit of erythromycin.

METHODS

Twenty four animals received either a trace (controls) or a 1% (high) cholesterol diet. After four weeks, five bipolar jejunal and terminal ileal electrodes were implanted. Seven days later, myoelectric activity was measured in conscious, fasted animals before and after treatment with erythromycin. Biliary lipid composition was assessed.

RESULTS

Compared with controls, animals fed the high cholesterol diet exhibited a prolonged MMC cycle period (70 (6) versus 83 (3) minutes; p<0.05), whereas MMC migration velocity and the proportions of the MMC represented by phases I, II, and III were unchanged. Oral erythromycin significantly shortened the MMC cycle period in animals on the control and high cholesterol diet by 59% and 54% respectively, and increased the proportion of the cycle period occupied by phase III of the MMC in both dietary groups. Gall bladder bile became saturated with cholesterol and crystals developed in nine of 12 animals on the high cholesterol diet; controls had none.

CONCLUSION

Animals fed a high cholesterol diet had a prolonged MMC cycle period. This, along with diminished gall bladder motility, impairs the enterohepatic cycling of bile salts and reduces their hepatic secretion, contributing to the formation of abnormal bile. Erythromycin initiated more frequent cycling of the MMC. Its therapeutic value in cholesterol gallstone formation warrants further evaluation.

Anaphylaxis-induced alterations in intestinal motility: role of extrinsic neural pathways

The roles of mast cells and extrinsic and vagal neural pathways in the anaphylaxis-induced alterations in motility observed at sites remote from antigen exposure were explored. Rats were sensitized to egg albumin (EA) and prepared with 1) electrodes to monitor intestinal myoelectric activity, 2) an isolated intestinal loop, and 3) either intact vagal innervation or a subdiaphragmatic vagotomy. Fasting myoelectric activity was recorded before and after challenge of the jejunum in continuity or the isolated loop with EA or BSA. Intestinal segments and the brain stems were processed for mast cell identification (intestine) or Fos immunoreactivity (brain stem). EA but not BSA challenge of the jejunum or the isolated loop induced altered motility at both sites and diarrhea. Granulated mast cells were significantly reduced at the site local to but not remote from challenge. Vagotomy did not inhibit antigen-induced alterations in motility or diarrhea. The number of Fos-immunoreactive nuclei in vagal sensory or motor nuclei was not significantly altered by vagotomy. Thus antigen challenge of sensitized animals causes mast cell degranulation only at the site of direct challenge but alters motility at sites local and remote from challenge. The remote response requires intact extrinsic but not necessarily vagal neural pathways.

Effect of the prokinetic agent, erythromycin, in the Richardson ground squirrel model of cholesterol gallstone disease

Impaired gallbladder motility and delayed intestinal transit contribute to cholesterol gallstone formation by impeding the enterohepatic circulation of bile salts and causing gallbladder stasis. The therapeutic value of erythromycin, a prokinetic motilin analog, was evaluated in an animal model of gallstone formation. Eighty ground squirrels were fed either a trace- (control) or a high- (1%) cholesterol diet. Half of each diet group received either erythromycin stearate or placebo orally twice daily for 4 weeks. Biliary lipid secretion and bile salt pool size were determined via common duct cannulation. Gallbladder contractile response to cholecystokinin (CCK) was studied in vitro. Intestinal transit was evaluated in vivo by 51Cr marker. In the placebo-treated group, fed the high- versus the trace-cholesterol diet, bile salt secretion decreased (trace-cholesterol + placebo, 21.0 +/- 1.8 nmol/min/g liver vs. high-cholesterol + placebo, 9.3 +/- 1.4 nmol/min/g liver), cholesterol saturation index (CSI) doubled (trace-cholesterol + placebo, 0.61 +/- 0.06 vs. high-cholesterol + placebo, 1.30 +/- 0.04), nucleation time shortened (trace-cholesterol + placebo, > 21 days vs. high-cholesterol + placebo, 6.4 +/- 1.0 days), cholesterol crystals formed, gallbladder contractility diminished, and intestinal transit was delayed (each P < .05). Erythromycin treatment of animals on the high-cholesterol diet restored gallbladder contractility and intestinal transit to control levels, increased bile salt secretion, reduced the total bile salt pool, lowered the cholesterol saturation of bile, lengthened the nucleation time, and so reduced crystal formation (each P < .05). Erythromycin enhances gallbladder motility and hastens intestinal transit, promoting more rapid enterohepatic cycling of bile salts. This increases bile salt secretion, improves cholesterol solubility, and reduces crystal development.

Clinical and microbial spectrum of fungal keratitis in Singapore: a 5-year retrospective study

BACKGROUND

The epidemiology of fungal keratitis varies geographically, but commonly occurs in warm, tropical climates. To determine the microbial and clinical characteristics of this disease in Singapore, we conducted a 5-year hospital-based retrospective study.

METHODS

A retrospective review of culture-positive fungal keratitis at the Singapore National Eye Center and Singapore General Hospital, from January 1991 to December 1995.

RESULTS

Twenty-nine consecutive cases of culture-positive fungal keratitis were seen over the study period. The mean age of the cases was 41 years and 23 were males. Amongst the varied occupations, 9 were construction workers. The most common cultured organisms were Fusarium sp. (52%) and Aspergillus flavus (17%). More than half had a history of ocular trauma prior to the development of keratitis, while a quarter had antecedent topical corticosteroid therapy. In contrast, only 2 patients were contact-lens wearers. Despite medical therapy, 10 patients eventually required therapeutic penetrating keratoplasties; of these, 6 were caused by Fusarium species.

CONCLUSION

Fusarium is the commonest cultured organism in fungal keratitis in Singapore and is associated with significant ocular morbidity.

Refractive change following pterygium surgery

PURPOSE

We conducted a prospective study of patients with primary pterygia to analyze surgically-induced astigmatic changes following pterygium surgery and their relation to pterygium morphology and size.

METHODS

One hundred twenty-three eyes of 123 adult patients with primary pterygia were evaluated. Pterygium was graded according to morphology and the extent of corneal encroachment. Manifest refraction was performed preoperatively and at 1, 3, and 6 months postoperatively. Patients underwent either the bare sclera technique of pterygium excision or conjunctival grafting. Surgery was performed by one surgeon. Olsen's method of vector decomposition was used to analyze surgically-induced astigmatism.

RESULTS

The mean magnitude of preoperative astigmatism was 0.99 D, with vector decomposition revealing a relative flattening of the cornea in the horizontal meridian. Astigmatism of 1.00 D or more was seen when the pterygium exceeded 3.5 mm beyond the limbus. Postoperatively, a steepening of the cornea in the horizontal meridian was demonstrated, the magnitude of which was related to pterygium size (P = 0.0001). ANOVA testing showed no significant difference (P > 0.05) when pterygia were divided according to morphology.

CONCLUSIONS

This study confirms that pterygium excision induces a reversal of pterygium-related corneal flattening. A strong correlation was also found between the horizontal extent of pterygium encroachment and astigmatic change following surgery.

Effects of Giardia lamblia infection on gastrointestinal transit and contractility in Mongolian gerbils

To determine if Giardia lamblia infection is associated with altered gastrointestinal transit and smooth muscle contractile function, Mongolian gerbils were infected orogastrically with 2 x 10(5) trophozoites (infected) or vehicle (uninfected controls). At the time of peak colonization, control and infected animals were infused either orogastrically or intraduodenally with 51Cr. Gastric emptying of isotope and intestinal transit (measured by the geometric center of distribution of intestinal 51Cr transit) were significantly (P < 0.05) greater in the infected compared to control animals in both the fasted and the fed states. Then, to determine whether Giardia lamblia has an effect on the contractility of longitudinal and circular smooth muscle, isometric tension of jejunal segments was recorded. The development of active tension with stretch and the dose-response curve to bethanechol were significantly increased in the longitudinal muscle of infected animals compared to controls. However, the circular smooth muscle did not show a similar increase in contractility. These findings suggest that an altered gastrointestinal transit and smooth muscle contractility may be involved in the pathophysiology of giardiasis.

Effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision

OBJECTIVES

To compare success rates of conjunctival autografting and bare sclera excision for primary and recurrent pterygium in the tropics and to evaluate risk factors for pterygium recurrence.

METHODS

A prospective, controlled clinical trial was performed in which 123 primary and 34 recurrent pterygia, matched for age and pterygium morphology, were randomized in 2 separate studies to receive either bare sclera excision or conjunctival autograft. The surgical procedures were performed by one surgeon and reviewed at 1, 3, 6, and 12 months after surgery by an independent observer. Pterygium morphology was clinically graded as atrophic, intermediate, or fleshy according to an assessment of pterygium translucency. Risk factors were assessed using likelihood ratio tests. Weibull curves were used to estimate recurrence rates allowing for the interval censoring.

RESULTS

In the group with primary pterygium (mean follow-up, 15.1 months), 38 (61%) of the 62 cases of bare sclera excision (heretofore referred to as the bare sclera group) had pterygium recur in contrast with 1 (2%) of the 61 cases of conjunctival autograft (heretofore referred to as the conjunctival autograph group) (P<.001, likelihood ratio X2 test). Nontranslucency, or fleshiness of the pterygium, and not age was a significant risk factor for recurrence in the bare sclera group (P<.001, likelihood ratio X2 test). In the group with recurrent pterygium (mean follow-up, 13.2 months), 14 (82%) of the 17 bare sclera group had pterygium recur, while no recurrences occurred among 17 cases in the conjunctival autograft group. Nontranslucency was again a highly significant factor for recurrence (P<.001, likelihood ratio X2 test).

CONCLUSIONS

Pterygium recurrence is related to pterygium morphology and fleshiness of the pterygium is a significant risk factor for recurrence if bare sclera excision is performed. Conjunctival autografting for primary and recurrent pterygium is effective in reducing pterygium recurrence compared with bare sclera excision.

Risk factors and clinical outcomes between fungal and bacterial keratitis: a comparative study

PURPOSE

Previous studies on fungal and bacterial keratitis were descriptive single case series analysis. We conducted a hospital-based retrospective study to evaluate fungal and bacterial keratitis using a case-control design to compare risk factors and clinical outcomes.

METHODS

Twenty-nine cases of culture-positive fungal keratitis seen over a 5-year period were compared to 51 cases of culture-positive bacterial keratitis seen over a 21 months period. Using bacterial keratitis as the reference group, case-control odds ratios (OR) for predisposing factors and cohort relative risks (RR) for clinical outcomes associated with fungal keratitis were derived. Mantel-Haenszel adjustment procedures were used to examine the respective roles of confounding and intermediate variables.

RESULTS

Compared to bacterial keratitis, fungal keratitis was significantly more likely to be associated with ocular trauma (OR = 2.69, 95% confidence interval [CI], 1.06-6.86) but significantly less likely to be associated with contact lens wear (OR = 0.16, 95% CI, 0.04-0.67) and preexisting ocular diseases (OR = 0.23, 95% CI, 0.07-0.72). Fungal keratitis was more likely to perforate than bacterial keratitis (RR = 5.28, 95% CI, 1.35-20.66) and to require penetrating keratoplasty (OR = 5.86, 95% CI, 2.06-16.69).

CONCLUSIONS

Fungal keratitis appears more likely to result from ocular trauma, whereas bacterial keratitis is more likely to result from contact lens wear and pre-existing ocular diseases. Fungal keratitis is more likely than bacterial keratitis to result in perforation and require penetrating keratoplasty.

Combined penetrating keratoplasty and limbal allograft transplantation for severe corneal burns

The management of ocular surface disease presents a significant challenge to ophthalmologists. Recent advances in the etiology and pathophysiology of ocular surface diseases, such as chemical and thermal burns or Stevens-Johnson syndrome, include the concept of the limbal stem cell. Limbal stem cell theory suggests that the corneal limbus contains epithelial stem cells that are responsible for a continuous supply of corneal epithelial cells, which not only migrate from the deep to superficial epithelial layers, but also progress in a centripetal direction, inward from the limbus. Support for this concept is provided indirectly by the relatively poor prognosis for penetrating keratoplasty for these types of ocular surface diseases. In such cases, it is suggested that limbal damage and depletion is present and is a significant factor in loss of integrity of the ocular surface; therefore, conventional penetrating keratoplasty, which does not include limbal tissue, does not have a high success rate.

Penetrating keratoplasty in the Singapore National Eye Centre and donor cornea acquisition in the Singapore Eye Bank

We analyzed all penetrating keratoplasties performed in the Singapore National Eye Centre from 1 January 1991 to 31 December 1995, using records of the Singapore Eye Bank Registry, evaluating the indications, complications, causes of graft failure, visual outcome and graft survival rate. We also looked into donor cornea acquisition in the Singapore Eye Bank and its influence on the development of corneal transplantation in the Singapore National Eye Centre. A total of 327 penetrating keratoplasties were performed during the 5-year period. Bullous keratopathy was an indication in 26.3% of cases. Of these, aphakic bullous keratopathy accounted for 11.6% of all cases, while pseudophakic bullous keratopathy accounted for 11.3%. Other indications were regrafts (11.9%), corneal dystrophies (10.4%), traumatic corneal scarring (10.1%) and keratoconus (9.8%). Graft rejection was a complication in 20% of all cases. Of these, 40.9% led to graft failure. Other major complications were raised intraocular pressure (18%), epithelium-related problems (7.3%), wound dehiscence (4.3%), cataract (3.3%) and microbial keratitis (3.1%). The main causes of graft failure were graft rejection (8.2%), endothelial failure (2.4%), infection (2.4%) and glaucoma (2.1%). Of the 327 grafts, 40.3% achieved best corrected visual acuity of 6/12 or better; 70.8% achieved vision of 6/24 or better. The overall graft survival rate was 82.3% after a mean follow-up period of 2 years. Donor corneas for the penetrating keratoplasties were obtained from foreign eye banks as well as locally, with the local donation rate steadily increasing from 1991 to 1996, with the establishment of proper eye banking facilities and the Singapore Eye Bank. These results show that the indications and outcome of penetrating keratoplasty in the Singapore National Eye Centre are similar and comparable to that of other centres with established corneal grafting programmes. The establishment of the Singapore Eye Bank has ensured the proper co-ordination of acquisition of donor material which has been vital to the development of corneal transplantation in the Singapore National Eye Centre.