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 patient’s 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.

BrJ Ophthalmol 1996; 80: 451-457) In direct relation to the dose administered allopurinol was shown to countercheck the oxidative tissue damage following lens induced uveitis (LIU). I This is believed to be due to its free radical scavenging activity and the scavenging of hypochlorous acid by its major metabolite oxypurinol. On the other hand, steroids applied as standard therapy for uveitis are known to reduce the synthesis of prostaglandins and thromboxanes by inhibition of the liberation of arachidonic acid from phospholipids. Moreover, several steroids such as methylprednisolone have scavenger activities that are dose dependent.2 3In the present study, biochemical measurements were performed to compare the therapeutic effects of allopurinol with those of steroids under the same disease conditions. In order to evaluate whether steroids and allopurinol show additive therapeutic effects the two drugs were given together.Additionally, the therapeutic effects were analysed histologically, using two methods. Materials and methods ANIMAL EXPERIMENTSThe treatment of animals conformed to the ARVO resolution on the use of animals in research. The experiments were performed with male Wistar rats (n=37). The animals were divided randomly into seven groups (two groups, five animals each for the biochemical study; five groups, five or six animals each for the slit-lamp/histological study).

A group of 160 Wistar rats (both sexes) from a larger chronic inhalation toxicity study was monitored at baseline and after 1 and 2 years with a photo-slitlamp microscope and a direct ophthalmoscope to record spontaneous age-related eye lesions and treatment-related eye lesions over a period of 24 months. A second group from the same study was monitored at the start and after 5 months of a 6-month posttreatment period immediately following the inhalation period. Rats were nose-only exposed for 6 h/day, 7 days/week, for 2 years to low (3 µg/l) or high (10 µg/l) total particulate matter concentrations of room-aged cigarette sidestream smoke (RASS) or diesel engine exhaust (DEE). Control animals were exposed to filtered fresh air. All ophthalmological examinations were performed in mydriasis, and relevant observations were documented on color slide film. At baseline, all animals with eye lesions were excluded from the study. After 1 year, only minor lesions were found: retrolental opacities (14%) and a few cases of corneal dryness with reddish lid margins. After 2 years, 23% of the animals had unilateral or bilateral retrolental opacities, but the most frequent eye lesions were posterior subcapsular cataracts (PSC, 32%). Water clefts and spokes were found in 11% of the lenses and mature cataracts in 6%. All other eye lesions observed were much less frequent. There were a few cases of glaucoma, corneal dryness and stromal neovascularization. The frequency and type of lesion in animals monitored from the start of the posttreatment period was comparable to what was seen after 2 years. Toward the end of this period the frequency of mature cataracts went up to 9% and that of (secondary) glaucomas to 5%. None of the eye lesions observed showed any association in frequency or severity of expression to the treatment, either RASS or DEE, or to the sex of the animals. In comparison to the (limited) literature data available, far fewer corneal lesions were found in this study, but PSCs and mature cataracts were more frequent. Strain differences may influence these parameters. This study provided valuable information on the nature and frequency of spontaneous age-related eye lesions (0–56%, depending on the tissue) in long-term toxicity studies in Wistar rats.

A confocal laser scan microscope is designed for the diagnosis and the examination of the anterior segment of the human eye in vivo. Any contact of the eye with the instrument optics or an immersion fluid is avoided to preclude the risk of infection or injury. Normal eyes of nine volunteers are observed and investigated. Nerve fibers and keratocytes in the stroma and the endothelium of the cornea, the capsule, and the suture of the lens, and threadlike structures in the vitreous can be observed. Cellular details in all tissues investigated can be resolved.

Up to now reading glasses are the conventional treatment of presbyopia, an age related effect for every human. According to the Helmholtz theory the reason for the development of accommodative loss is a decreasing elasticity of the lens due to the increasing sclerosis. Since the ciliary muscle and the lens capsule remain active and elastic the whole life, a possible treatment could be the increase of the flexibility by creating gliding planes with fs-laser pulses.In former studies it was shown that fs-laser pulses can increase the flexibility of ex vivo porcine as well as human donor lenses with a laboratory laser system. We will present new results with a compact 100 kHz repetition rate turn key laser system which speeds up the treatment time by a factor of 10. This will offer the opportunity for future clinical trials. Furthermore first in-vivo results on rabbits are presented.