Automated, computerized, feature-based phenotype analysis of slit lamp images of the mouse lens

Longitudinal studies of a variety of transgenic mouse models for lens development can create substantial challenges in database management and analysis. We report a novel, automated, feature-based informatics approach to screening lens phenotypes in a large database of slit lamp images. Digital slit lamp images of normal and abnormal lenses in eyes of wild type (wt), SC1 null and SPARC null transgenic mice were recorded for quantitative evaluation of their structural phenotype. The images were processed to improve the contrast of structural features that corresponded to rings of opacity and fluctuations in scattering intensity in the lenses. Measurable attributes were assigned to the features in the lens images and given as an output vector of 46 dimensions. Characteristic patterns were correlated with the structural phenotype of each mutant and wt lens and a statistical fit for each phenotype was defined. The genotype was identified correctly in nearly 85% of the slit lamp images on the basis of an automated computer analysis of the lens structural phenotype. The automated computer algorithm has the potential to evaluate a large database of slit lamp images and distinguish mouse genotypes on the basis of lens phenotypes objectively using a neural network analysis of the structural features observed in the slit lamp images. The neural network approach is a promising technology for objective evaluation of genotype/phenotype relationships based on structural features and light scattering in lenses. Further improvements in the automated method can be expected to simplify and increase the accuracy and efficiency of the feature based analysis of structural phenotypes linked to genetic variation.     

Mobilizing slit lamp to the field: A new affordable solution

We are describing a simple and affordable design to pack and carry the slit lamp to the field. Orbis staff working on the Flying Eye Hospital (FEH) developed this design to facilitate mobilization of the slit lamp to the field during various FEH programs. The solution involves using a big toolbox, a central plywood apparatus, and foam. These supplies were cut to measure and used to support the slit lamp after being fitted snuggly in the box. This design allows easy and safe mobilization of the slit lamp to remote places. It was developed with the efficient use of space in mind and it can be easily reproduced in developing countries using same or similar supplies. Mobilizing slit lamp will be of great help for staff and institutes doing regular outreach clinical work.     

功能裂隙灯生物显微镜对正常成人结膜微血管血流动力学指标的检测和临床应用价值

目的 探讨功能裂隙灯生物显微镜(functional slit lamp biomicroscopy,FSLB)对正常成人结膜微血管血流动力学指标的检测和临床应用价值.方法 随机抽取南昌大学医学院和中山眼科中心硕士研究生16人,其中男8人,女8人;年龄21～ 25岁.应用FSLB并使用软件程序(BenoitTM,TruSoft Inc,St.Petersburg,FL,USA)对受试者结膜微血管密度、微血管长度、微血管直径、微动脉血流速度、微静脉血流速度等指标进行检测,并分析受试者各指标特征.结果 受试者右眼微血管密度、长度、直径、微动脉血流速度、微静脉血流速度上方和下方、鼻侧和颞侧差异均无统计学意义(均为P＞0.05);受试者右眼微血管密度、长度、直径上方、下方均较鼻侧、颞侧减小,差异均有统计学意义(均为P＜0.05);受试者微动脉血流速度、微静脉血流速度右眼上方、下方均较鼻侧、颞侧明显增加,差异均有统计学意义(均为P＜0.05).左眼以及总眼数的情况和右眼相一致.结论 利用FSLB可以较为清晰地获得正常成人结膜微血管血流动力学指标,有很好的临床价值.     

Assessment of the ocular media absorption index

Purpose: To determine a practical method for quantifying in vivo lens absorption by human crystalline, obtaining an index of lens density in our population. Method: 62 normal subjects were evaluated in this study (ages ranging from 20 to 71 years). Testing procedure: Measurements of dark-adapted scotopic thresholds for 450 nm and 656 nm stimuli were obtained (Tubinger perimeter) in order to determine ocular media absorption. Van Norren and Vos's procedure was used to calculate ocular media absorption transmission loss. Least-squares linear regressions were used to correlate lens density to age. Results: A gradual and approximately linear increase in average lens absorbance was found under 55 years of age. Elder subjects showed a higher increase in this absorbance with higher variability. A correction factor for age-related ocular media absorption was obtained from the calculated curve. The range was approximately 1 to 5 dB. Conclusion: Determination of the transmission characteristics of the preretinal media is essential for interpreting threshold sensitivity values. Increase in lens absorption has been shown to be selective for short wavelengths. Due to this fact, a correction factor for the age-related ocular media absorption should be applied to avoid misinterpretation of the Blue-on-Yellow perimetry absolute results. That factor may discriminate sensitivity losses due to changes in the lens from those due to retinal or neuronal dysfunction.     

Scanning beyond the limits of standard OCT with a Fourier domain optical coherence tomography integrated into a slit lamp: the SL SCAN-1

Purpose

With a new Fourier domain optical coherence tomography (FD OCT) device, SL SCAN-1 (Topcon Europe Medical BV, Capelle a/d IJssel, The Netherlands), integrated into a slit-lamp OCT, scans can be obtained through a handheld lens. The necessary adjustment of the reference arm is possible by fast Z-alignment. This study was performed to prove the capability of SL SCAN-1 to scan through a three-mirror contact lens, scanning the peripheral retina and anterior chamber angle.

Methods

Different representative pathologies of the peripheral retina and anterior chamber were simultaneously observed and scanned with the SL SCAN-1. The scans of peripheral retinal lesions were obtained both through a handheld lens and through a three-mirror contact lens. The anterior chamber angle was scanned directly with the SL SCAN-1 in anterior mode, and through the gonio-mirror of a three-mirror contact lens with the SL SCAN-1 in posterior mode.

Results

OCT scans could be obtained with the SL SCAN-1 of the peripheral retina through both, a common handheld lens and a three-mirror contact lens. The scans obtained through a three-mirror contact lens were of better quality, visualizing details of the different layers of the retina more clearly. The scans of the anterior chamber, obtained through the gonio-mirror of a three-mirror contact lens, visualized the open anterior chamber angle, with details of fine structures.

Conclusions

The SL SCAN-1 is a unique FD OCT system, which is able to scan not only the posterior pole and anterior segment but also the anterior chamber angle and the more peripheral retina. These four modalities combined into one device could make the SL SCAN-1 a very powerful aid in daily practice.     

Straylight in the human eye: testing objectivity and optical character of the psychophysical measurement

The point spread function or PSF of the human eye encompasses hugely different domains: a small-angle, high-intensity domain, called the 'PSF core', and a large-angle, low-intensity domain, usually referred to as 'straylight'. The first domain can be assessed by available double-pass or other optical techniques. For the second domain psychophysical techniques have been developed, in particular the Compensation Comparison or CC technique, recently made available for clinical application in the C-Quant instrument. We address the question of whether the psychophysical technique gives measures of straylight that are compatible with those made by optical methods. With a small adaptation the CC method can be used to assess straylight from physical light scattering samples, instead of straylight in the eye, using the same psychophysics, but without interference from the ocular straylight. The light scattered by each of seven light-scattering samples, encompassing the range of straylight values observed in human eyes, was measured by two optical methods and by the psychophysical technique. The results showed that the optical and psychophysical measurements for the seven samples were almost identical.     

Further observations on the effect of galactose on the development of X-ray-induced cataract in mice

The effect of a 30% galactose diet on the progression of X-ray-induced cataract in mice was evaluated by following morphological changes as seen by light and transmission electron microscopy in different regions of the lens. Lens opacities as observed with the slit-lamp biomicroscope developed at a slower rate in galactose-fed animals than in those on a normal diet. The protective effect of galactose on X-ray cataract was seen whether galactose feeding was initiated either 1 week before or after exposure to X-ray. At 4 months after X-ray approximately 50% of galactose-fed animals had mature cataracts, compared to 100% in the control group. Similarly, at two weeks after exposure to X-ray, before any lens opacities were observed, morphological changes were more severe in the control group; cells in the meridional row were more disorganized in the control than in the galactose-fed groups. However, the progression of mature cataracts in the two galactose-fed groups were not significantly different. Since free radicals produced by X-ray are thought to be short-lived, the protective effect of galactose feeding after X-ray was unexpected, raising the possibility that some of the active species may be long-lasting. The nature of such radicals, if any, is unknown and remains to be investigated.     

Sex, age and the birefringence of the human crystalline lens

Measurements were made of the birefringence of intact human crystalline lenses and of single lens fibres in the age range of 4 to 93 years. Birefringence changes were observed when the lenses were stressed. It was possible to obtain high correlations between the optical and mechanical properties of the lenses. Male and female lenses had significantly different properties, the latter pointing to a greater disposition to irreversible changes under minimal stress. Age produced systematic changes. Both stress and age parameters are analyzed.     

Ultraviolet light exposure and its penetrance through the eye in a porcine model

AIM: To determine the amount of ultraviolet (UV) light irradiance that various layers of the eye receive as sunlight passes through the eye, and to investigate the protective benefits of UV light-blocking contact lenses. METHODS: Twenty-four porcine eyes were prepared in one of three ways: isolated cornea, cornea and lens together, or whole eye preparation. UV light irradiance was measured with a UV-A/B light meter before and after the eye preparations were placed over the meter to measure UV light penetration in each eye structure. In the whole eye preparation, a hole was placed in the fovea to measure light as it passed through the vitreous. Subsequently, UV-protective contact lenses were placed over the structures, and UV light penetrance was measured. Measurements of UV light exposure were taken outdoors at various locations and times. RESULTS: Cornea absorbed 63.56% of UV light that reached the eye. Cornea and lens absorbed 99.34% of UV light. Whole eye absorbed 99.77% of UV light. When UV-protective contact lenses were placed, absorption was 98.90%, 99.55%, and 99.87%, respectively. UV light exposure was dependent on directionality and time of day, and was greatest in areas of high albedo that reflect significant amounts of light, such as a beach. CONCLUSION: Cornea absorbs the majority of UV light that reaches the eye in this model. UV-protective contact lenses reduce UV exposure to the eye. Locations with high albedo expose the eye to higher levels of UV light.     

Intraocular lenses in children: changes in axial length, corneal curvature, and refraction

AIM: To assess changes in axial length, corneal curvature, and refraction in paediatric pseudophakia. METHODS: 35 eyes of 24 patients with congenital or developmental lens opacities underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation. Serial measurements were made of axial length, corneal curvature, objective refraction, and visual acuity. RESULTS: For patients with congenital cataracts (onset < 1 year age) the mean age at surgery was 24 weeks. Over the mean follow up period of 2.7 years, the mean increase in axial length of 3.41 mm was not significantly different from the value of an expected mean growth of 3.44 mm (paired t test, p = 0.97) after correction for gestational age. In the developmental cataract group (onset > 1 year of age) the mean age at surgery was 6.4 years with a mean follow up of 2.86 years. This group showed a mean growth in axial length of 0.36 mm that was not significantly different from an expected value of 0.47 mm (paired t test, p = 0.63). The mean preoperative keratometry was 47.78 D in the congenital group and 44.35 D in the developmental group. At final follow up the mean keratometry in the congenital group was 46.15 D and in the developmental group it was 43.63 D. In eyes followed for at least 2 years, there was an observed myopic shift by 24 months postoperatively of 3.26 D in the congenital cases (n = 10) and 0.96 D in the developmental cases (n = 18). CONCLUSION: The pattern of axial elongation and corneal flattening was similar in the congenital and developmental groups to that observed in normal eyes. No significant retardation or acceleration of axial growth was found in the eyes implanted with IOLs compared with normal eyes. A myopic shift was seen particularly in eyes operated on at 4-8 weeks of age and it is recommended that these eyes are made 6 D hypermetropic initially with the residual refractive error being corrected with spectacles.     

Impact on visual function from light scattering and glistenings in intraocular lenses,a long‐term study

Purpose: To investigate the impact on visual function from light scattering and glistenings in intraocular lenses (IOLs) in patients who had cataract surgery 10 years previously. Setting: Eye clinic, Norrlands university hospital, Umeå, Sweden. Methods: One hundred and three patients, who had phacoemulsification with implantation of Acrysof^® MA60BM IOLs 10 years previously, were evaluated with best corrected visual acuity (VA), and low contrast visual acuity (LCVA) 10% and 2.5%. The light scattering from the IOLs was measured by Scheimpflug photography. The degree of glistenings was also quantified at the slit‐lamp. Eyes with coexisting pathology that could affect VA and LCVA were excluded. Results: The patients were divided into various groups according to the degree of light scattering and grade of glistenings. In two subsets of patients, paired data from the patients’ eyes were analysed. It was not possible to detect any significant impact on visual function, best corrected visual acuity (BCVA) and LCVA 10% and 2.5% in eyes with a more pronounced light scattering or a higher grade of glistenings seen at the slit‐lamp. The correlation between IOL dioptric power and both the total light scattering of the IOL, and the subjective grading of the intensity of the glistenings at the slit‐lamp was statistically significant (r_P = 0.25; p = 0.012; r_S = 0.23; p = 0.019, respectively). Conclusion: Most patients in this case series operated 10 years previously had severe glistenings and a high level of light scattering from their intraocular lenses. No detectable impact on BCVA, LCVA 10% and 2.5% was found.     

Deciding what to see: the role of intention and attention in the perception of apparent motion

Apparent motion is an illusory perception of movement that can be induced by alternating presentations of static objects. Already in Wertheimer's early investigation of the phenomenon [Wertheimer, M. (1912). Experimentelle Studien über das Sehen von Bewegung. Zeitschrift fur Psychologie, 61, 161-265], he mentions that voluntary attention can influence the way in which an ambiguous apparent motion display is perceived. But until now, few studies have investigated how strong the modulation of apparent motion through attention can be under different stimulus and task conditions. We used bistable motion quartets of two different sizes, where the perception of vertical and horizontal motion is equally likely. Eleven observers participated in two experiments. In Experiment 1, participants were instructed to either (a) hold the current movement direction as long as possible, (b) passively view the stimulus, or (c) switch the movement directions as quickly as possible. With the respective instructions, observers could almost double phase durations in (a) and more than halve durations in (c) relative to the passive condition. This modulation effect was stronger for the large quartets. In Experiment 2, observers' attention was diverted from the stimulus by a detection task at fixation while they still had to report their conscious perception. This manipulation prolonged dominance durations for up to 100%. The experiments reveal a high susceptibility of ambiguous apparent motion to attentional modulation. We discuss how feature- and space-based attention mechanisms might contribute to those effects.     

Evolution of light scattering and redox balance in the rat lens after in vivo exposure to close‐to‐threshold dose ultraviolet radiation

Acta Ophthalmol. 2010: 88: 779–785

Abstract.

Purpose: To investigate the evolution of cataract development and glutathione redox balance in the rat lens after in vivo close‐to‐threshold dose exposure to ultraviolet radiation (UVR) around 300 nm. Methods: Three groups of 10 Sprague–Dawley rats were unilaterally exposed to 8 kJ/m² UVR‐300 nm for 15 min, and a fourth group of 10 rats was kept without UVR exposure as nonexposed control animals. The exposed animals were killed at 1, 3 and 7 days after exposure. Both lenses from all animals were extracted and photographed and the intensity of forward light scattering was measured quantitatively. Thereafter, the lenses were homogenized. The concentration of reduced glutathione (GSH) and oxidized glutathione (GSSG), and the activity of glutathione reductase (GR) and glutathione peroxidase (GPx), respectively, were determined spectrophotometrically. The mean paired differences between exposed and nonexposed lenses were used as primary data in the statistical analyses. Results: All exposed lenses developed cataract. Lens light scattering increased throughout the 7 days after UVR exposure. GSH concentration and GPx rate transiently increased at 1 day after exposure and then decreased throughout follow‐up, with GSH concentration having a negative balance at the end. GSSG concentration and GR activity did not change after UVR exposure. Conclusion: In vivo close‐to‐threshold UVR exposure induces a gradual increase in rat lens opacification/cataract development and time dependently alters the redox balance in the lens.     

The Shearing Intraocular Lens: Where Does It Go and What Does It Do in the Eye?

Seven Shearing lenses were inserted in four dogs that were selected because their ciliary body sulcus diameter was approximately equal to that of humans. These animals were killed at intervals ranging from 4.5 to 11 months and the eyes submitted for histopathology. In all instances, gross examination revealed the lenses to be well tolerated; however in two eyes there was migration of the peripheral loop into the peripheral iris stroma and, in one case, ciliary body sulcus necrosis was seen. No vitreous hemorrhage was found in any of the eyes. One intraocular lens was removed before the animal was killed and the eye did not appear to be damaged. This study raises the possibility of ciliary body damage in those eyes in which the lens is slightly displaced so that one loop exerts pressure on the ciliary body. For this reason, we feel that posterior vitreous hemorrhages must be carefully looked for.     

Toric IOL植入术与PCRI联合传统IOL植入术矫正白内障患者角膜散光的Meta分析

目的：:系统评价Toric人工晶状体（Toric IOL）植入术与传统IOL植入联合角膜缘松解术（PCRI）在矫正年龄相关性白内障患者合并≤3 D角膜散光的有效性、安全性以及对视功能的影响。方法：:循证医学研究。采用Cochrane系统评价方法,计算机检索PubMed、EMBASE、Cochrane图书馆、Clinic...     

Enzymhistochemical identification of microglial cells in the rat retina: light and electron microscopic studies

We used the method of thiamine pyrophosphatase (TPPase) enzyme histochemistry and flat-mounted and transverse-sectioned retinas to identify microglial cells. Light microscopically, TPPase activity was demonstrated on the outer surfaces of glial cells located in the inner plexiform layer (IPL) and the ganglion cell layer (GCL) of the entire retinal regions, and also on the outer surfaces of blood vessels. Electron microscopically, TPPase activity was observed on the plasma membranes of the glial cells, the endothelial cells of microvessels and the pericytes. The TPPase-positive glial cells had a dark nucleus with large clumps of chromatin beneath the nuclear envelope. These findings strongly suggest that the glial cells with TPPase activity observed in the IPL and the GCL of the rat retina were microglial cells.     

Pigmented Striae of the Anterior Lens Capsule and Age-Associated Pigment Dispersion of Variable Degree in a Group of Older African-Americans: An Age, Race, and Gender Matched Study

PURPOSE: To investigate pigmented striae of the anterior lens capsule in African-Americans, a potential indicator of significant anterior segment pigment dispersion. METHODS: A group of 40 African-American subjects who exhibited pigmented lens striae (PLS) were identified from a non-referred, primary eye care population in Chicago, IL, USA. These subjects were then compared to an age, race, and gender matched control group relative to refractive error and the presence or absence of diabetes and hypertension. RESULTS: The PLS subjects (mean age = 65.4 +/- 8.8 years, range = 50-87 years) consisted of 36 females and 4 males. PLS were bilateral in 36 (85%) of the 40 subjects. Among the eyes with PLS, 21 (55%) of 38 right eyes and 22 (61%) of 36 left eyes also had significant corneal endothelial pigment dusting, commonly in the shape of a Krukenberg's spindle. Ten (25%) of the PLS subjects had either glaucoma or ocular hypertension (7 bilateral, 3 unilateral). The presence of trabecular meshwork pigment varied from minimal to heavy. The mean +/- SD (range) refractive error of the PLS right eyes was +1.61 +/- 1.43D (-1.50 to +5.00D) and +1.77 +/- 1.37D (-1.00 to +5.00D) for the left eyes. Based on these data, the PLS right eyes were +1.63D (Student's t, p = 0.0001; 95% CI = +0.82 to +2.44D) more hyperopic on average than the control right eyes, and the PLS left eyes were +1.77D (p = 0.0001; 95% CI = +0.92 to +2.63D) more hyperopic on average than the control left eyes. Trend analysis showed a gradually increasing likelihood of PLS with increasing magnitude of hyperopia in both eyes (Mantel-Haenszel chi-square, p = 0.001). Among PLS subjects, 24 (60%) of 40 were hypertensive and 9 (23%) of 40 were diabetic. However, these proportions were not significantly different (two-tailed Fisher's exact test; hypertension: p = 0.30; diabetes: p = 0.70) from the randomly selected controls. CONCLUSIONS: Among our African-American group, which consisted predominately of females >50 years of age, the likelihood of PLS increased with increasing hyperopic refractive error. This finding is consistent with the possibility that PLS may, in some circumstances, indicate a significant pigment dispersal process due to iris-lens rubbing that may be associated with crowding of anterior segment structures. Additional study is warranted to further assess the nature of PLS, their precise relationship with an age-related pigment dispersal process, and their true significance as a risk factor for development of glaucoma.