[Aspheric profiles for refractive laser ablation of the cornea]. / Asphärische profile für refraktiven laserabtrag an der hornhaut.

Conventional ablation profiles for excimer lasers for myopic refractive correction of the cornea are of spheric geometry. Therefore, they induce additional imaging aberrations into the optical system of the eye, most notably spherical aberration. This is a major cause of the observed deterioration of visual quality after such corrections, especially under low illumination and ensuing larger pupil diameter. Therefore, aspheric ablation profiles compromizing the preexisting imaging/visual quality of the eye as little as possible are currently being developed and optimized for all laser platforms. Employed methods include customized correction profiles on the basis of individual wavefront data of the anterior corneal topography on the one hand, and correction profiles that minimize the induced spherical aberration in a "standardized" way on the other hand. We demonstrate for a particular laser platform how such profiles must be developed and optimized. Mathematical theoretical calculations appear to be an indispensable but insufficient prerequisite. The biological reaction of the corneal stroma and epithelium ("biodynamic response") can only be determined experimentally and must lead to adjustment of the calculated ablation algorithm. The results show that aspheric profiles developed on this basis can lead to significant reduction of induced spherical aberration. The obtainable effect is, however, limited by the biological response and the ensuing peripheral ablation depth and volume.

[Complications with foldable intraocular lenses with subsequent explantation in 1998 and 1999. Results of a questionnaire evaluation]. / Komplikationen faltbarer Intraokularlinsen mit der Folge der Explantation von 1998 und 1999. Ergebnisse einer Fragebogenauswertung.

PURPOSE: A questionnaire was sent to all members of the German Society of Ophthalmic Surgeons to evaluate complications of foldable intraocular lenses (IOLs) that required explanation. METHODS: Information on preoperative visual acuity, foldable IOL design and material as well as the reason for IOL explantation was obtained and analysed. We received 167 completed questionnaires for 1998 and 1999. RESULTS: In 1998 and 1999 the most common reasons for IOL explantation were as follows: incorrect lens power for 56% of the 3-piece hydrophobic acrylic IOLs, 16% because of glare or other photic phenomena, 40% of the 1-piece hydrophilic acrylic IOLs were explanted because of incorrect lens power and 30% for IOL damage. For the 3-piece monofocal silicone IOLs, 41% were explanted because of incorrect IOL power and 32% because of IOL decentration. For the 1-piece Hydrogel IOL, 76% were explanted because of opacification of the optic and 14% because of incorrect lens power. Most multifocal IOLs were explanted because of photic phenomena. CONCLUSION: In addition to the most common complications such as decentration and incorrect IOL power observed in rigid IOLs, new complications associated with foldable IOLs occurred such as optic opacification, glare and photic phenomena. Some complications seemed to appear in particular IOL types (opacification: SC-60BOUV, MDR), while others were observed in all types of foldable lenses. Accurate calculation of the IOL power and further improvement of the IOL material and design seem to be necessary to minimise the rate of explantations.

[Complications of foldable intraocular lenses requiring explantation. Results of the 2000 and 2001 survey in Germany]. / Komplikationen faltbarer Intraokularlinsen mit der Folge der Explantation. Untersuchungsergebnisse der Jahre 2000 und 2001.

PURPOSE: A survey was sent to all members of the German Society of Ophthalmic Surgeons to evaluate complications that required explantation of foldable intraocular lenses (IOLs). METHODS: Data on preoperative visual acuity, foldable IOL design and material, and the reason for explantation were obtained and analysed. We received 185 surveys for 2000 and 2001. RESULTS: In 2000 and 2001, the most common reasons for IOL explantation were: incorrect lens power (31%) and dislocation (19%) in three-piece acrylic IOLs, incorrect power (31%) and decentration (17%) in monofocal silicone IOLs, and opacification (46%) in hydrophilic IOLs. The most common reasons for the exchange of monofocal IOLs were lens opacification in 2000 and incorrect IOL power in 2001. CONCLUSION: Besides the most frequent complications of decentration and incorrect power observed in rigid IOLs,new complications associated with foldable IOLs occurred (e.g., optic opacification and calcification). Accurate calculation of IOL power and further improvements in material and design are still necessary to minimize the rate of explantations.