A. Wegener

Photography of the anterior eye segment according to Scheimpflug's principle: options and limitations – a review

Scheimpflug photography and densitometric image analysis are very precise techniques for light scattering measurement and biometry in the anterior segment of the eye. They provide reproducible data on the characteristics of the anterior eye segment in clinical and experimental studies and the set of data obtained allows discrimination of light scattering changes because of ageing, disease or toxic effects. The techniques can also be used to determine no‐effect levels or maximally tolerable dosages of physical and chemical noxious factors. Several Scheimpflug cameras have been marketed, but the only cameras commercially available today are the Nidek EAS 1000 and the Oculus Pentacam. This review outlines the development of the technique and its introduction into ophthalmology. Furthermore, the application of the technique in clinical and experimental ophthalmology as well as in ocular toxicology are presented and discussed.

Knockout of the intermediate filament protein CP49 destabilises the lens fibre cell cytoskeleton and decreases lens optical quality, but does not induce cataract

In this report, the phenotype associated with the first targeted knockout of the lens specific intermediate filament gene CP49 is described. Several surprising observations have been made. The first was that no cataract was observed despite the fact that the beaded filaments of the lens fibre cells had been disrupted. Light scatter and the lens optical properties had, however, deteriorated in the CP49 knockout lenses compared to litter mate controls. These changes were accompanied by dramatic changes in plasma membrane organisation of the fibre cells as revealed by detailed morphological examinations and providing the second surprising result. The CP49 knockout mouse is therefore an important model to study the functional link between lens transparency, the cytoskeleton and plasma membrane organisation.

Cataract prevalence and prevention in Europe: a literature review.

This literature review is aimed at the evaluation of the potential for cataract prevention in Europe. It was performed using PubMed with Mesh and free‐text terms. Studies included were (i) performed on a population of Caucasian origin at an age range of 40–95 years, (ii) cataract was clinically verified, (iii) drug record of prescriptions, their indication, a record of every diagnosis, dosage and quantity of prescribed medicine were available, (iv) sample size >300 and (v) published between 1990 and 2009. The results of 29 articles were reviewed. Former [3.75 (2.26–6.21)] or current smoking [2.34 (1.07–5.15)], diabetes of duration >10 years [2.72 (1.72–4.28)], asthma or chronic bronchitis [2.04 (1.04–3.81)], and cardiovascular disease [1.96 (1.22–3.14)] increased the risk of cataract. Cataract was more common in patients taking chlorpromazine during ≥90 days with a dosage ≥300 mg [8.8 (3.1–25.1)] and corticosteroids >5 years [3.25 (1.39–7.58)] in a daily dose >1600 mg [1.69 (1.17–2.43)]. Intake of a multivitamin/mineral formulation [2.00 (1.35–2.98)] or corticosteroids [2.12 (1.93–2.33)] also increased the risk of cataract. Corticosteroids applied orally [3.25 (1.39–7.58)], parenteral [1.56 (1.34–1.82)] or inhalational [1.58 (1.46–1.71)] lead to cataract more frequently than those applied topically: nasal [1.33 (1.21–1.45)], ear [1.31 (1.19–1.45)] or skin [1.43 (1.36–1.50)]. Outpatient cataract surgery was negatively associated with total cataract surgery costs, and chlorpromazine, corticosteroids and multivitamin/mineral formation increase the risk of posterior subcapsular cataract dependent on dose, treatment application and duration. This review presented a comprehensive overview of specific and general cataract risk factors and an update on most recent experimental studies and randomized control trials directed at cataract prevention.

Anterior Chamber Angle Biometry: A Comparison of Scheimpflug Photography and Ultrasound Biomicroscopy

Scheimpflug photography and ultrasound biomicroscopy allow measurement of anterior chamber angle width. To analyze the value of both diagnostic tools, measurements of the same subjects were correlated. Anterior chamber angle width in both eyes of 20 volunteers without any ophthalmological case history was measured in eight meridians. Scheimpflug photographs were recorded on Kodak T-max 400 black-and-white film using a Topcon SL-45 camera. Measurement of chamber angle was done with the aid of a self-programmed PC software. Ultrasound biomicroscopic measurements were obtained using a Humphrey UBM 840 system with a 50-MHz transducer. The chamber angle was measured as described by Pavlin et al. The data of both methods were correlated and analysed for statistically significant differences using a paired t test (level of significance p < or = 0.05). Both methods showed similar changes in chamber angle width and were able to document a variation in angle width with regard to location. The correlation averaged at 0.64. In 4 meridians significant differences were found between the two methods. Scheimpflug photography, however, is unable to visualize directly the angle itself. Both methods are limited by the fact that the angle is defined by curvilinear structures, i.e. posterior corneal surface and anterior iris surface. Scheimpflug photography is able to document changes in angle configuration. Ultrasound biomicroscopy, however, is a more precise method, because it allows direct documentation of all structures involved in chamber angle configuration.

In vivo studies on the effect of UV-radiation on the eye lens in animals

Ultraviolet light is a non-ionizing radiation that induces photochemical reactions in the tissue. Its spectral A and B ranges are partially absorbed by the cornea and/or lens thus causing damage on the cellular, cell physiological and molecular level. UV-A does not seem to damage the cornea permanently and its effects in the lens have a very prolonged latency period. Typical reactions of the cornea are oedema, punctate keratitis (photoelectric keratitis) and neovascularization. In the lens all reactions that could be evidenced, were located in the epithelium and in the outer cortical fiber cells.In vivo UV-A induces swelling and slight vacuolation of the anterior suture system, but apart from these transient effects, only very limited permanent damage could be demonstrated. UV-B induces the formation of an anterior subcapsular cataract, starting also with vacuolation of the suture system. These morphological characteristics can be visualized at the slitlamp microscope. Histologically, sutural irregularities (UV-A) and epithelial hyperplasia with capsular multiplication (UV-B) as well as desintegration of the anterior suture system could be observed. Patho-physiologically, a reduction of lens fresh weight (UV-B) as well as changes of the equilibrium of reduced and oxidized glutathione (GSH/GSSG) could be demonstrated. On the protein-biochemical level, changes in the ratio of water-soluble versus water-insoluble protein could be evidenced, as well as effects on specific crystallin fractions, namelyα-crystallin. In addition, the appearance of a newly synthetized 31 kDa protein could be demonstrated in UV-B irradiated mice.

Femtosecond laser induced flexibility change of human donor lenses.

BACKGROUND According to the Helmholtz theory of accommodation the loss of accommodation amplitude is caused by the growing sclerosis of the crystalline lens, whereas the ciliary muscle and the lens capsule are mainly uneffected by age. A permanent treatment method for presbyopia which offers a dynamic accommodation ability is a recent field of study. The concept followed in this paper uses femtosecond laser pulses to potentially overcome the loss of deformation ability of the crystalline lens by creating gliding planes inside the lens tissue to improve its flexibility. METHODS The aim of the study is to show that the flexibility of human donor lenses can be increased by applying tightly focused near infrared femtosecond laser pulses into the lens tissue. Thereby the tissue is separated by the photodisruption effect. A certain pattern of gliding planes is cut inside the tissue of 41 human donor lenses and the deformation ability of the lenses are compared using the Fisher spinning test before and after laser treatment. RESULTS The laser treatment results in an increased deformation ability of the crystalline lens. The lens a-p thickness increases on average by 97 microm+/-14 microm after the treatment. The Fisher spinning test shows an increase of 16% in deformation ability of the lens at a rotational speed of 1620 rpm. CONCLUSION The creation of gliding planes with a fs laser inside the crystalline lens tissue can change the deformation ability of the lens. This might be an indication for a possible method to treat presbyopia in future.

Improved Biometry of the Anterior Eye Segment

In this paper, a method is presented to evaluate the true values of several optical parameters of the anterior eye segment. These are: the thicknesses of the cornea and lens, the depth of the anterior chamber and the anterior and posterior curvatures of the cornea and lens. First, a photo is taken of each patients eye with a Topcon SL-45 Scheimpflug camera. There are two effects distorting the photo. As the film plane and the object plane are perpendicular to each other, the imaging scale is not constant over the photo, a phenomenon which is called the camera distortion. As the light passes through different refractive media on its way from the inner structures of the eye to the camera, the rays of light are refracted, which is called the refractive distortion of the eye. Following these distortions, the proportions on the photo do not correspond to those in the human eye. The intention of this paper is to calculate the true optical parameters of the anterior eye segment. The seeming optical parameters are taken from the photo and the path of light from a point in the film plane through the camera and the refracting surfaces into the eye is constructed by ray tracing. A set of representative points calculated according to ray tracing provides a basis to evaluate the true optical parameters. This work is done using a Basic program, that accepts the seeming parameters from the photo as input values and provides the true values as output. The adjectives seeming and true added to the optical parameters indicate a value correlating with a distorted photo and a value that was corrected by the theory. The two terms were chosen by mnemonic reasons, although another pair of adjectives such as distorted and corrected might have been of higher precision. For an average adult human eye the optical parameters from the photo were compared with the calculated ones. A phantom eye with well-known optical parameters was constructed and photos were taken from this eye to verify the calculations.

Femtosecond lentotomy: generating gliding planes inside the crystalline lens to regain accommodation ability

Based on Helmholtz Theory for accommodation the increasing sclerosis of lens nucleus and cortex is the main cause for the developments of presbyopia. Existing therapies, however, do not reverse the stiffness of the crystalline lens and thus do not regain real accommodation ability. A new approach to restore the flexibility of the lens could be realized by photodisruption using ultrafast laser pulses. This process, known as fs-lentotomy, was used to create micro-incisions which act as gliding planes inside the crystalline lens without opening the eye globe.

The Intermediate Filament Systems in the Eye Lens

Publisher Summary This chapter describes the basic methods to purify important lens fractions and to track the distribution of IF proteins in the eye lens and their associated proteins. It also provides the description of the methods used for the preparation, sectioning, and examination of eye lenses. The IF proteins of the lens help in determining its optical properties. Whereas, a transparent lens is normal, a lens with either a reduced level of transparency or a localized opacity is abnormal and/or pathological. One of the pitfalls in the purification of lens proteins is proteolysis, especially when urea buffers are used, but the methods in the chapter describe the effective purification of CP49, filensin, and vimentin for use in vitro assembly and structural studies. The animal models can help to understand the mechanisms of cataractogensis, and in combination with the optical studies the futuristic possibility of regenerating superlenses for combating cataract may be expected.

Absence of glutaredoxin1 increases lens susceptibility to oxidative stress induced by UVR-B

We investigated if the absence of glutaredoxin1, a critical protein thiol repair enzyme, increases lens susceptibility to oxidative stress caused by in vivo exposure to ultraviolet radiation type B (UVR-B). Glrx(-/-) mice and Glrx(+/+) mice were unilaterally exposed in vivo to UVR-B for 15 min. Groups of 12 animals each received 4.3, 8.7, and 14.5 kJ/m(2) respectively. 48 h post UVR-B exposure, the induced cataract was quantified as forward lens light scattering. Cataract morphology was documented with darkfield illumination photography. Glutathione (GSH/GSSG) content was analyzed in Glrx(-/-) and Glrx(+/+) lenses. UVR-B exposure induced anterior sub-capsular cataract (ASC) in Glrx(-/-) and Glrx(+/+) mice. In Glrx(-/-) lenses the opacities extended further towards the lens equator than in wild type animals (Glrx(+/+)). Lens light scattering in Glrx(-/-) mice was increased in all dose groups compared to lenses with normal glutaredoxin1 function. The difference was more pronounced with increasing exposure dose. Lens sensitivity for UVR-B induced damage was significantly higher in Glrx(-/-) lenses compared to Glrx(+/+) lenses. The Glrx gene provides a 44% increase of protection against close to threshold UVR-B induced oxidative stress compared to the absence of the Glrx gene. In conclusion, the absence of glutaredoxin1 increases lens susceptibility to UVR-B induced oxidative stress in the mouse.