Measurement of the axial length of cataract eyes by laser Doppler interferometry.

PURPOSE: To examine the applicability of the recently developed laser Doppler interferometry technique for measuring the axial length of cataract eyes in a realistic clinical situation. To determine the performance of the instrument as a function of cataract grade. To compare the results to those of ultrasound methods. METHODS: A total of 196 cataract eyes of 100 patients were examined. The axial eye length was determined by laser Doppler interferometry and by two different ultrasound techniques, the applanation technique and the immersion technique. The cataract grade was determined by a commercial instrument that measures backscattered light. RESULTS: Laser Doppler interferometry worked very well except in the cases of the highest cataract grades (4% of the eyes of this study were not measurable because of a too-high lens density). Only 3.5% of the other eyes were not measurable because of fixation problems of the patients. The precision of laser Doppler interferometry is not influenced by the cataract grade (except the highest grade). The standard deviation of the geometric eye length is approximately 20 microns. Linear regression analysis revealed a very good correlation of laser Doppler interferometry and ultrasonic measurements, but a systematic difference was found. The eye lengths measured by laser Doppler interferometry were about 0.18 mm longer than those measured by the immersion technique and about 0.47 mm longer than those measured by the applanation technique. CONCLUSION: These differences are attributed to the laser Doppler interferometry results including the retinal thickness and indentation of the cornea by the applanation technique. The main advantages of the laser Doppler interferometry technique are high precision, high accuracy, and more comfort for the patient because it is a noncontact method, anesthesia is unnecessary, and the risk of corneal infection is avoided.

Corneal lathing using the excimer laser and a computer-controlled positioning system: Part II--Variable trephination of corneal buttons.

A new system is presented that allows a variable trephination of donor corneas for the preparation of corneal buttons used in penetrating keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is removed, epithelial side up, in a fixation device in front of a focused excimer laser beam (ArF, lambda = 193 nm). User friendly computer software allows the surgeon to select a variety of parameters (diameter, shape, angle of trephination) of the corneal graft. Histological and electron microscopical data of human corneas trephined with this "Excimer Laser Corneal Shaping System" are presented.

Corneal lathing using the excimer laser and a computer-controlled positioning system: Part I--Lathing of epikeratoplasty lenticules.

Precise lathing of epikeratoplasty lenticules is difficult to achieve with the cryolathe due to unpredictable expansion of the lathing tools and the corneal tissue during the freezing process. In addition, the procedure destroys all viable cells in the transplant thereby possibly contributing to the prolonged period of visual rehabilitation. Non-freezing techniques using the microkeratome or the rotor-trephine, on the other hand, are technically demanding, can cause mechanical damage during cutting or fixation, and, have not given consistently reproducible refractive results. A new system is presented that allows a variable laser ablation of donor corneas into lenticules for aphakic and myopic epikeratoplasty, as well as for lamellar keratoplasty. With the help of a computer-controlled positioning system that uses high-precision micropositioning elements (both translation and rotational stages) the donor cornea is moved, epithelial side down, in a holding device in front of a focused excimer laser beam (ArF, lambda = 193 nm). This photoablation lathing process assures the viability of the stromal cells in the lenticule in close approximation to the treated surface. The user friendly computer software allows the fast and convenient selection of a variety of parameters, such as the diameter of the optical zone, the shape of the wing zone, the refractive power, the central thickness of the lenticule and the overall contour of the transplant. The first laboratory data of lenticules prepared from human corneas with this "Excimer Laser Corneal Shaping System" are presented.

Manifestations of graft-versus-host disease following allogenic bone marrow transplantation.

Sixty-seven patients undergoing allogenic bone marrow transplantation (BMT) were examined before and at regular intervals for up to 87 months (1-87 months, mean 18) after transplantation. Within a period of 1-39 months, 14 of these patients died (11 male, 3 female; age at BMT 16-46y). Five of these patients died within the first 100 days. They showed no eye involvement; three patients had intraretinal hemorrhage, in one case of squamous blepharitis and filiform keratitis developed during chronic graft-versus-host disease (GVHD). In contrast, 22 of 53 (41.5%) surviving patients (30 male, 23 female; age at BMT 1-47y) were found to have ocular involvement. Before BMT only two cases of retinal hemorrhage and central chorioretinal scars each were detected. During the stage of acute GVHD (up to day 100), nine patients were free of ocular manifestations. However, 16 of the 20 patients with chronic GVHD showed ocular involvement; 14 (70%) had reduced tearflow, ten had severe keratoconjunctivitis sicca, four suffered from sterile corneal ulcerations. Bilateral cataracts were detected in 11 patients, nine of whom only had minimal posterior subcapsular opacification, possibly resulting from highdose steroid medication. One additional case presented with bilateral multifocal recurrent chorioretinitis and panuveitis. The fundus lesions appeared some months after BMT (before cyclosporin-A treatment started) and recurred during systemic treatment. All patients undergoing allogenic BMT, especially when treated for severe chronic GVHD, require regular ocular observation to avoid complications such as keratoconjunctivitis sicca at an early stage, as late complications are often severe and hardly amenable to conservative or surgical treatment.

[Acanthamoeba keratitis--a too seldom diagnosed disease?]. / Acanthamöben-Keratitis--eine zu selten diagnostizierte Erkrankung?

Acanthamoeba keratitis has become a difficult diagnostic and management problem in contact lens patients over the last few years. A young female contact lens wearer presented with a long history of painful central corneal ulcer. The suspected diagnosis of Acanthamoeba keratitis could only be confirmed by histology and electron microscopy following penetrating keratoplasty. Special stains of scrapings and culture of material on special media failed to establish the diagnosis. This rare (or underdiagnosed?) infection must be considered in the differential diagnosis of keratitis following contact lens wear.