Dennis S.C. Lam

Choroidal vascular remodelling in central serous chorioretinopathy after indocyanine green guided photodynamic therapy with verteporfin: a novel treatment at the primary disease level.

Aims: To evaluate the changes in the choroidal vasculature in central serous chorioretinopathy (CSC) after photodynamic therapy (PDT) with verteporfin and to assess its potential role as a treatment option. Methods: A prospective, non-comparative, interventional study was performed in eyes with persistent CSC or chronic CSC that had fluorescein leakage at the fovea. All eyes received one single session of PDT with verteporfin (6 mg/m2 body surface area) followed by application of 50 J/cm2 laser at 689 nm. The laser spot size was guided by findings in ICG-A. Results: Six eyes from six patients with a mean follow up of 12.7 months were analysed. Narrowing of the original dilated choroidal vessels and decrease in extravascular leakage could be demonstrated in all (100%) PDT treated eyes. 3 months after PDT, the mean diameter of the dilated choroidal vessel reduced from 546 μm to 371 μm (p = 0.028). Five (83%) patients had improvement in visual symptoms and best corrected visual acuity. Fluorescence leakage stopped at the 1 month follow up in five eyes (83%) and at 3 months in all six eyes (100%). One eye developed choroidal neovascularisation at 3 month follow up. There was no other serious ocular or systemic complication. Conclusions: PDT is successful in stopping the fluorescein leakage in all six patients without recurrence of CSC. The ICG-A findings of choroidal vascular remodelling and decreased choroidal permeability after PDT are encouraging. As the sample size is small and the mean follow up period is short, further trials of PDT with verteporfin for CSC are required to address the optimal parameters in ensuring longer term safety and efficacy outcome.

Common variants near CAV1 and CAV2 are associated with primary open-angle glaucoma

We conducted a genome-wide association study for primary open-angle glaucoma (POAG) in 1,263 affected individuals (cases) and 34,877 controls from Iceland. We identified a common sequence variant at 7q31 (rs4236601[A], odds ratio (OR) = 1.36, P = 5.0 × 10−10). We then replicated the association in sample sets of 2,175 POAG cases and 2,064 controls from Sweden, the UK and Australia (combined OR = 1.18, P = 0.0015) and in 299 POAG cases and 580 unaffected controls from Hong Kong and Shantou, China (combined OR = 5.42, P = 0.0021). The risk variant identified here is located close to CAV1 and CAV2, both of which are expressed in the trabecular meshwork and retinal ganglion cells that are involved in the pathogenesis of POAG.

Incidence and risk factors for microbial keratitis in Hong Kong: comparison with Europe and North America.

Purpose To establish the incidence, etiology and risk factors for microbial keratitis (MK) in Hong Kong.Methods Two hundred and twenty-three new cases of presumed MK were recruited over a period of 17 months and comprehensive microbiologic studies performed. A nested case-control study was pursued for patients wearing contact lenses (CLW) to determine risk factors for MK with regards to types of CLW and hygiene practice.Results Of the 223 patients recruited, 59 (26%) wore contact lenses. Corneal scrapes yielded positive cultures from 77 patients (35% overall, 56 non-CLW, 21 CLW). Two hundred and six CLW volunteers were recruited to participate in the case-control study, of whom 135 were matched with 45 CLW patients. The annual incidence of MK was 0.63 per 10 000 population and 3.4 per 10 000 CLW with rates for daily, extended and rigid lens wear of 3.09, 9.30 and 0.44 per 10 000 CLW respectively. Pseudomonas aeruginosa was the dominant bacterial pathogen. Six cases of Acanthamoeba keratitis occurred, five in CLW (incidence 0.33 per 10 000 CLW) and one following corneal abrasion. Non-CLW developed MK at a peak age of 73, which is 10 years younger than expected for Scotland and USA.Conclusions Previous ocular surface disease and trauma were the main risk factors for MK in Hong Kong. CLW appears at least as safe as that found in Scotland and the USA. Acanthamoeba keratitis was detected but with an incidence rate five times lower than Scotland. Factors predisposing hydrogel CLWs to MK, that were statistically significant, included overnight wear, poor hygiene and smoking.

Comparison of macular thickness measurements between time domain and spectral domain optical coherence tomography.

PURPOSE To compare macular thickness measurements obtained from time domain optical coherence tomography (OCT) and spectral domain OCT and to evaluate their repeatability and agreement. METHODS Thirty-five healthy normal subjects were included. In one randomly selected eye in each subject, three serial macular measurements were obtained from a time domain OCT (Stratus OCT, Carl Zeiss Meditec, Dublin, CA) and a spectral domain OCT (3D OCT; Topcon, Tokyo, Japan) by an experienced technician in random order. Total and regional macular thicknesses obtained by the two OCTs were compared. Their agreement was examined with Bland-Altman plots. Repeatability (2.77 x within subject SD [Sw]), coefficient of variation (CVw; Sw/overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability. RESULTS Low variability for macular thickness measurements was found in both time domain and spectral domain OCTs. The range of the respective CVw and ICC values were 1.6% to 3.2% and 0.85 to 0.91 for Stratus OCT and 0.6% to 2.4% and 0.92 to 0.99 for 3D OCT. 3D OCT demonstrated better repeatability for total and regional macular thicknesses (all with P <or= 0.014). The foveal and total macular thicknesses measured by 3D OCT were significantly greater than those measured by Stratus OCT (both with P < 0.001). The spans of 95% limits of agreement for foveal and total macular thicknesses were 33.9 and 21.3 mum, respectively. CONCLUSIONS Although both time domain and spectral domain OCTs are reliable for macular thickness measurements, spectral domain OCT has better measurement repeatability compared with time domain OCT. Macular measurements obtained from the two OCT systems may not be used interchangeably.

Safety enhanced photodynamic therapy for chronic central serous chorioretinopathy: one-year results of a prospective study.

Purpose: To evaluate the efficacy of a safety enhanced photodynamic therapy (PDT) protocol with half-dose verteporfin for treating chronic central serous chorioretinopathy (CSC). Methods: Forty-eight eyes of 48 patients with symptomatic chronic CSC underwent indocyanine green angiography guided PDT with half dose (3 mg/m2) verteporfin. Outcome measures included logMAR best-corrected visual acuity (BCVA), central retinal thickness, and angiographic changes during the 12-month study period. Results: The mean CSC duration was 8.2 months (range, 3–40 months). At 12 months after PDT, the mean logMAR BCVA improved from 0.31 to 0.15 (P < 0.001). The mean improvement was 1.6 lines and 45 (95.8%) eyes had stable or improved vision. Eyes without pigment epithelial detachment (PED) had significantly greater visual improvement compared with eyes with PED (P = 0.031). Patients with CSC of 6 months or less or younger than 45 years were more likely to gain vision by two or more lines after treatment (P = 0.007 and P = 0.018, respectively). Forty (83.3%) eyes had complete resolution of serous detachment at 3 months, with 43 (89.6%) eyes at 12 months. Conclusions: The safety enhanced PDT protocol appeared to be beneficial for patients with chronic CSC. Further controlled study is warranted to evaluate the safety and efficacy of this treatment option.

Relationship between Retinal Nerve Fiber Layer Measurement and Signal Strength in Optical Coherence Tomography

PURPOSE To examine the relationship between signal strength and retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT). DESIGN Observational cross-sectional study. PARTICIPANTS Forty normal subjects were recruited. METHODS Retinal nerve fiber layer (RNFL) thickness was measured by Stratus OCT (Carl Zeiss Meditec, Dublin, CA). In each eye, the focusing knob was adjusted to obtain 6 images with different signal strengths ranging from 5 to 10. The relationships between signal strength and RNFL thickness were examined using the Spearman correlation coefficient. The differences of RNFL thicknesses were compared with repeated-measures analysis of variance. MAIN OUTCOME MEASURES Retinal nerve fiber layer thicknesses measured at different signal strengths. RESULTS Significant differences were observed between measurements obtained at signal strength of 10 and those obtained with signal strength of less than 10 at the superior, nasal, and temporal clock hours. RNFL thickness generally increased with the signal strength, with significant correlations found with the total average, superior, and nasal clock hours RNFL thicknesses. CONCLUSIONS Optical coherence tomography RNFL measurements vary significantly with signal strength. Obtaining the maximal possible signal strength is recommended for RNFL thickness measurement.

Safety enhanced photodynamic therapy with half dose verteporfin for chronic central serous chorioretinopathy: a short term pilot study.

Aim: To evaluate short term safety of an enhanced photodynamic therapy (PDT) protocol with half dose verteporfin for treating chronic central serous chorioretinopathy (CSC). Methods: 20 eyes of 18 patients with symptomatic chronic CSC underwent PDT using 3 mg/m2 verteporfin. Verteporfin was infused over 8 minutes followed by indocyanine green angiography guided laser application 2 minutes later. Serial optical coherence tomography (OCT) and multifocal electroretinography (mfERG) recordings were performed before PDT, at 4 days, 2 weeks, and 1 month after PDT. The best corrected visual acuity (BCVA), OCT central retinal thickness, and mean mfERG response amplitudes and peak latencies were compared longitudinally. Subgroup analysis was further performed for eyes with or without pigment epithelial detachment (PED). Results: At 1 month after PDT, the median BCVA improved from 20/40 to 20/30 (p = 0.001). The mean central retinal thickness also reduced from 276 μm to 158 μm (p<0.001) and 17 (85%) eyes had complete resolution of serous retinal detachment and/or PED. MfERG showed no significant changes in the mean N1 and P1 response amplitude and latency for all eyes. Subgroup analysis demonstrated that eyes without PED had a significant increase in the mean central mfERG P1 response amplitude with reduction in P1 peak latency at 1 month post-PDT. For eyes with PED, transient reduction in the mean central P1 response amplitude was observed at 4 days post-PDT. Conclusions: The modified safety enhanced PDT protocol with half dose verteporfin appeared to be a beneficial treatment option for patients with chronic CSC, especially in eyes without serous PED. Further controlled study is warranted to demonstrate the long term safety and efficacy of this treatment option.

Microbial keratitis in Hong Kong: relationship to climate, environment and contact-lens disinfection

Microbial keratitis has been studied in Hong Kong as a representative sub-tropical climate of south China. An 18-month investigation in 1997/98 of 223 cases of ulcerative keratitis (presumed microbial) was conducted in the 2 million population of Shatin and Kowloon at the Prince of Wales and Hong Kong Eye Hospitals respectively with comprehensive microbiology. A case-control study was pursued at the same time between 45 contact-lens wearers (CLW) developing microbial keratitis and 135 lens-wearing volunteers matched for age, sex, educational status and visual acuity. Home water supplies were sampled for Acanthamoeba. Previous ocular surface disease and trauma (preventable by wearing goggles for grinding) were common predisposing causes while cosmetic wear of contact lenses was responsible for 26% of cases overall. Pseudomonas aeruginosa was the commonest bacterium isolated, from both CLW and non-CLW, with infection being acquired within the community. These 28 pseudomonads remained fully sensitive to the third-generation cephalosporins, aminoglycosides and quinolone antibiotics, which is very encouraging. Fungi were isolated, predominantly Fusarium sp., but less commonly than expected. A fungal/bacterial ratio was obtained of 1/17, while in comparison, the expected ratio for a tropical climate ranges from 1/5 (Singapore) to 1/2 (South India). Acanthamoeba was the second commonest microbe isolated from keratitis of CLW. The domestic water environment of 8% of homes of both patients and controls wearing contact lenses was colonized with Acanthamoeba. Lack of hygiene, use of tap water for storing lenses, failure to air-dry lens-storage cases or use of one-step hydrogen peroxide disinfectant were identified as risk factors for keratitis in CLW. The study results commend use of multipurpose solutions by CLW in Hong Kong to achieve the lowest expected rates of infection.

Intraoperative mitomycin C to prevent recurrence of pterygium after excision: A 30-month follow-up study

OBJECTIVE The purpose of the study was to examine the efficacy of intraoperative mitomycin C (MMC) in preventing recurrence of pterygium after excision and the postoperative complications encountered. DESIGN The study design was a prospective, randomized, clinical trial. PARTICIPANTS A total of 180 primary and recurrent pterygia were recruited for the study. They were randomized into five groups: A, control with no MMC; B, 0.02% MMC for 5 minutes; C, 0.04% MMC for 5 minutes; D, 0.02% MMC for 3 minutes; and E, 0.04% MMC for 3 minutes. INTERVENTION All patients received pterygium excision with or without the above four modes of intraoperative MMC application. MAIN OUTCOME MEASURES Recurrence of pterygium and postoperative complications such as superficial scleral melting were measured. RESULTS At a mean follow-up of 30 (groups A-C) and 20 months (groups D and E), the respective recurrence rates in groups A through E were 75%, 8.3%, 8.6%, 42.9%, and 22.9%. There were two cases of postoperative superficial scleral melting in group C. Otherwise, no major postoperative complications were encountered. CONCLUSIONS The midterm results of a single intraoperative application of MMC at the concentration of 0.02% for 5 minutes are encouraging. Its application as an adjunctive therapy for the surgical treatment of pterygium appeared to be safe and effective. However, because of the possibility of serious late complications, the authors suggest that this procedure be reserved for patients who have high probability of recurrence after excision of pterygium.

Intravitreal bevacizumab (Avastin) with or without photodynamic therapy for the treatment of polypoidal choroidal vasculopathy

Aim: To evaluate the efficacy of intravitreal bevacizumab (Avastin) with or without verteporfin photodynamic therapy (PDT) in the treatment of polypoidal choroidal vasculopathy (PCV). Methods: Fifteen eyes of 15 patients with symptomatic PCV who received three monthly intravitreal bevacizumab were retrospectively reviewed. Subsequent retreatments with intravitreal bevacizumab and/or PDT were performed in patients with recurrent or persistent polypoidal lesions on indocyanine green angiography (ICGA), and persistent or recurrent subretinal fluid. Results: The mean follow-up duration was 12.8 months. At 3 months, the mean logMAR BCVA improved from 0.61 to 0.51 (p = 0.014), and the mean CFT reduced from 347 μm to 247 μm (p = 0.015). Despite the visual and anatomical improvements, persistent polyps were present in ICGA of all eyes at 3 months. At the last follow-up, mean BCVA remained at 0.51 after additional treatment with intravitreal bevacizumab and/or PDT (p = 0.022). Patients who had subsequent PDT were less likely to have persistent polypoidal lesions on ICGA at the last visit (p = 0.041). Conclusions: Intravitreal bevacizumab appeared to result in stabilisation of vision and reduction of exudative retinal detachment in PCV patients. However, intravitreal bevacizumab monotherapy had limited effectiveness in causing regression of the polypoidal lesions in ICGA, and additional PDT appeared to be useful for treating these lesions.