Laser interference biometry versus ultrasound biometry in certain clinical conditions.

PURPOSE: To compare laser interference biometry (LIB) with conventional ultrasound biometry in certain clinical conditions such as globe deformities, eccentric fixation, retinal detachment, macular edema or silicone oil-filled eyes. SETTING: Department of Ophthalmology, Würzburg University Eye Hospital, Germany. METHODS: We evaluated all patients who came to our university hospital for axial length measurement with our routine immersion biometry system (Grieshaber Biometry System) and compared the results with those obtained using the Zeiss IOLMaster of Carl Zeiss Jena, the commercially available LIB device. RESULTS: Selected case reports demonstrate the advantages and disadvantages of LIB. Advantages of LIB were found in patients with asymmetrically shaped globes, eccentric fixation, silicone oil-filled eyes and a fearful/nervous disposition. Disadvantages of the system were revealed in cases of retinal detachment, severe opacities along the visual axis and poor patient cooperation. CONCLUSION: We showed that LIB is a valuable addition to the choice of biometric devices, when used with medical understanding.

Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to Haigis.

BACKGROUND: The precision of intraocular lens (IOL) calculation is essentially determined by the accuracy of the measurement of axial length. In addition to classical ultrasound biometry, partial coherence interferometry serves as a new optical method for axial length determination. A functional prototype from Carl Zeiss Jena implementing this principle was compared with immersion ultrasound biometry in our laboratory. PATIENTS AND METHODS: In 108 patients attending the biometry laboratory for planning of cataract surgery, axial lengths were additionally measured optically. Whereas surgical decisions were based on ultrasound data, we used postoperative refraction measurements to calculate retrospectively what results would have been obtained if optical axial length data had been used for IOL calculation. For the translation of optical to geometrical lengths, five different conversion formulas were used, among them the relation which is built into the Zeiss IOL-Master. IOL calculation was carried out according to Haigis with and without optimization of constants. RESULTS: On the basis of ultrasound immersion data from our Grieshaber Biometric System (GBS), postoperative refraction after implantation of a Rayner IOL type 755 U was predicted correctly within +/- 1 D in 85.7% and within +/- 2 D in 99% of all cases. An analogous result was achieved with optical axial length data after suitable transformation of optical path lengths into geometrical distances. CONCLUSIONS: Partial coherence interferometry is a noncontact, user- and patient-friendly method for axial length determination and IOL planning with an accuracy comparable to that of high-precision immersion ultrasound.

[Low Vision Enhancement System (LVES). Initial clinical experiences with a new kind of optoelectronic rehabilitation system]. / Low-Vision-Enhancement-System (LVES). Erste klinische Erfahrungen mit einem neuartigen optoelektronischen Rehabilitationssystem.

BACKGROUND: The Low-Vision-Enhancement-System (LVES) is the first binocular optoelectronic rehabilitation device with variable focus distance. METHOD: LVES was attempted on 25 patients who were not adequately treatable with classic rehabilitation devices. Using the new device, short-distance vision as well as the ability to read and write were tested. RESULTS: In six patients, a significant improvement was achieved using LVES. In these patients, short-distance vision as measured by LVES varied from 0.63 to 1.0. All succeeded in reading fluently, and five patients, in writing. Of these patients, five suffered from large central scotomas due to macular disease, and one female patient, from post-traumatic optic nerve atrophy. In 10 patients, near-sighted vision could be improved although the ability to read and write could not be restored, while nine patients did not show any benefit. In the latter group, were four patients with retinopathia pigmentosa, who complained of the further reduction in visual field due to the system. CONCLUSION: LVES is an additional device for the rehabilitation of low-vision patients which is especially useful in cases of macular diseases.

A method of correlating and merging cerebral morphology and function by a special head holder.

A method is introduced which records and correlates topographically identical morphological and functional image data by means of a special head holder system which is adaptable to different modalities (MRI, PET, SPECT). It is based on a commercially available thermoplastic headmask. A thermoplastic form is used to mold an individual headmask (time required: 7 min) for all modalities providing a fixation of the patient during acquisition. This method guarantees an exact repositioning and therefore the same slice orientation of the images. The in-plane correlation is performed by adapting standard offset parameters determined with a homogeneous head phantom. By fusion (merging) of the brain outline contours or images themselves the accuracy was tested in MRI vs. PET resp. SPECT (transaxial accuracy: < or = 2.0 mm, axial: < or = 3.0 mm in patients with MRI-slice thickness of 6.0 mm).