Enping Chen

An objective and rapid method for the determination of light dissemination in the lens

Abstract. A method for the objective measurement of light dissemination in the lens was developed. There is an exponential relationship between the concentration of standard solutions and the intensity of light disseminated forwards. The light disseminated in non‐pathological lenses from Sprague Dawley rats was registered as the equivalent standard concentration, C, and then transformed to log10 (C + 1) and was found not to deviate from the normal distribution. The tolerance limit for light dissemination was derived by setting the probability to classify a non‐pathological lens as pathological. An analysis of variance demonstrated that the inter‐animal variation was the dominating source of imprecision. It is anticipated that the developed system will be useful in experimental toxicological risk assessment.

Dose-response function for lens forward light scattering after in vivo exposure to ultraviolet radiation.

Abstract · Background: It is known that different types of radiation, as well as aging and metabolic disorders, can cause cataract. Several epidemiological investigations show a correlation between cataract development and the dose of ultraviolet radiation (UVR) received. It is well established experimentally that exposure of animal eyes to UVR induces cataract. The purpose of the present study was to determine the dose-response function for UVR-induced opacities in the rat lens after in vivo exposure. · Methods: Sprague-Dawley rats received 0.1, 0.4, 1.3, 3, 5, 8 or 14 kJ/m2 UVR (λMAX=300 nm, λ0.5=10 nm) unilaterally for 15 min. At 1 week after exposure both lenses were removed, photographs were taken and the intensity of forward-scattered light was measured. · Results: One week after UVR exposure, opacities occurred on the lens surface, as observed with a microscope. With increased UVR dose the opacities became more intense and occurred also in the equatorial area of the lens, but not in the nucleus. The intensity of forward light scattering increased with increased UVR dose between 3 and 14 kJ/m2. No significant change in intensity of forward light scattering was observed for lower UVR doses. · Conclusion: The intensity of forward light scattering in the rat lens increases exponentially with increased UVR dose between 0.1 and 14 kJ/m2.

Cytochrome oxidase activity in rat retina after exposure to 404 nm blue light.

Cytochrome oxidase (CYO), a key enzyme in the respiratory chain, was observed as an indicator of retinal metabolism after an in vivo blue light exposure. Thirty Sprague-Dawley rats were exposed to optic radiation of 404 nm with a retinal dose of 110kJ/m2. Immediately after exposure, the CYO activity in the pigment epithelium, in the outer and inner segments of photoreceptors, and in the outer plexiform layer of the exposed retina, was reduced to one-third-to-half of the control level. However, there was an increase in CYO activity in the exposed retina one day after exposure. One week after exposure, the CYO activity in the inner segment and the outer plexiform layer was higher, while the activity in the other two layers was lower, than that at one day, although still higher than in the control. Two weeks after exposure, the CYO activity in the four retinal layers returned to the level of the control retina, as did the activity four weeks after. After exposure, no ophthalmoscopically visible retinal change and no light-microscopically evident morphological alterations were found. There was no retinal edema or loss of photoreceptor cells. The observed alteration in CYO activity after blue light exposure may represent an inhibition of retinal metabolism. The inhibition was reversible. If this compensation mechanism is overwhelmed, retinal damage may occur.

Universal Opacity Standard for Scheimpflug Photography

Purpose: To develop a universal standard for comparison of the results from different studies using Scheimpflug photography. Material and Method: A suspension including polystyrene spheres was selected as the universal standard. The polystyrene suspension was diluted into 10 concentrations by adding spectroscopic quality water. An artificial eye chamber was designed to hold the diluted suspension for photography. Each concentration was photographed by both a Topcon SL-45 slit-lamp camera and a Nidek EAS-1000 system. The intensity of back-scattered light was analyzed statistically. Results: The relationship between the concentration of the polystyrene suspension and the internal gray scale step within the Topcon SL-45 camera can be described by a second-order polynomial. The relationship between the concentration of the polystyrene suspension and the measurement of the Nidek EAS-1000 system can also be expressed by a second-order polynomial. The relationship between the Topcon SL-45 camera and the Nidek EAS-1000 system is linear. Conclusions: The results of lens nuclear opacity measured with different Scheimpflug cameras can be compared using the method established in the study. The linear relationship between the Topcon SL-45 and Nidek EAS-1000 systems can be used to convert measurements from one system to the other.

Comparison of selective laser trabeculoplasty (SLT) in primary open angle glaucoma and pseudoexfoliation glaucoma.

Background and objective The aim of the present study was to compare intraocular pressure (IOP) reduction and inflammation after selective laser trabeculoplasty (SLT) treatment in patients suffering from primary open angle (POAG) vs pseudoexfoliative (PXFG) glaucoma. Study design/patients and methods Sixty patients (60 eyes) participated in the study. Glaucoma patients (POAG or PXFG) scheduled for treatment with SLT were included. Inflammation was measured with a laser flare meter (Kowa FM-500). Measurements were made before SLT and 2 hours, 1 week, and 1 month after SLT treatment. IOP was also checked at the same time intervals. Results Inflammation after SLT showed no significant difference between the groups (t-test, before: P = 0.16; 2 hours: P = 0.14; 1 week: P = 0.12; and 1 month: P = 0.36). IOP reduction was the same in both groups (t-test, P = 0.27). Conclusion SLT safely reduces IOP in both POAG and PXFG. Pseudoexfoliation does not seem to be a risk factor for post-laser complications.

Predictive factors of success in selective laser trabeculoplasty (SLT) treatment.

Purpose: Glaucoma is a progressive optic neuropathy that may lead to blindness. Reducing intraocular pressure (IOP) is the only known treatment to slow progression in glaucoma. IOP can be reduced by pharmaceutical treatment, laser and surgery. The aim of the present study was to assess predictive factors of success after selective laser trabeculoplasty (SLT) treatment. Methods: We used a retrospective chart review of eyes that underwent SLT between January 1, 2005 and December 31, 2005. The dependent variable was time to failure after SLT treatment. Failure after SLT was defined as any changes in the medical treatment, and/or a new SLT treatment was performed and/or the patient was sent for surgery. All patients were treated with 90° SLT. A multivariate regression analysis was performed to assess correlation between time to failure after SLT and age, gender, IOP before treatment, number of medications used, SLT number, amount of spots, laser energy used, grade of angle, pigmentation and diagnosis. Results: 120 eyes of 120 patients were identified. The average time to failure after SLT was 18 months. The predictive factors identified were: age, IOP before SLT and dose. Conclusion: Predictive factors identified in our study were high baseline IOP, age and amount of laser energy used. Our study confirms previous results about baseline IOP as a predictive factor.

3 Year simvastatin treatment and lens nuclear back scattering

AIM To determine if 3 year treatment of hypercholesterolaemia with simvastatin causes an increase of lens nuclear back scattering. METHODS 160 patients with hypercholesterolaemia in the Scandinavian Simvastatin Survival Study (4S) were followed for 3 years. Half (80) of the patients took simvastatin and half (80) received placebo. The lens was photographed with a Topcon SL-45 slit lamp camera at the beginning and at 1 year intervals. A common lens nuclear area was used for measuring lens nuclear back scattering. RESULTS Nuclear back scattering increased with age and there was more pronounced scattering in women than in men. Lens nuclear back scattering did not differ significantly between the simvastatin and placebo groups, but the power was low (0.2). Lens nuclear back scattering increased during the study period independently of baseline back scattering, age, and sex for both groups. CONCLUSION Although no significant difference was found between the simvastatin and placebo groups, the currently available data are insufficient for exclusion of the possibility that taking simvastatin during a 3 year period increases nuclear back scattering. However, a possible minor increase of nuclear back scattering is clinically irrelevant considering known beneficial effects of simvastatin on coronary heart disease.

Corneal hysteresis in mucopolysaccharidosis I and VI.

Purpose:  High intraocular pressure (IOP) and glaucoma are often suspected in patients with mucopolysaccharidosis (MPS). To determine corneal hysteresis (CH) and IOP in children with mucopolysaccharidosis I‐Hurler (MPS I‐H) and MPS VI.

Angular dependence of the intensity of backscattered light from human lenses with nuclear cataract: implications for measurement

It is concluded that there is no angular dependence of back scattering of light from a nuclear cataract. This implicates that reading one meridian, e.g. the 90 degree, is enough for measurement of nuclear cataract with slit lamp microscopy with Scheimpflug projection. Altogether, ten patients with nuclear cataract were measured with the NIDEK EAS-1000 system in 6 meridians. There was a slight angular dependence fitting a second order polynomial with a maximum at 90 degrees. In total, three different concentrations of standard scattering solution were measured with the same system at the same meridians. Also for these measurements, there was a slight angular dependence fitting a second order polynomial with the maximum at 90 degrees. Thus, there is a system related factor that causes a slight change of intensity of back scattered light as function of meridian.

Inflammation assessment after selective laser trabeculoplasty (SLT) treatment

Purpose:  Selective laser trabeculoplasty (SLT) appears to be a safe and effective method to lower intraocular pressure (IOP). The exact mechanism of action for reducing IOP and inflammation levels is not known.