Astigmatismus

Der Astigmatismus ist der weltweit häufigste Refraktionsfehler vor Hypermetropie und Myopie. Man unterscheidet den äußeren vom inneren Astigmatismus. Der äußere Astigmatismus kann weiter in „mit der Regel“, „gegen die Regel“ und „schräg“ unterteilt werden. Die Summierung des äußeren und inneren Astigmatismus ergibt den refraktiven Zylinder. Astigmatismus wurde lange als zweidimensionales Phänomen gesehen, doch erst die dreidimensionale Betrachtung hat den Blick auf bestehende Analyseverfahren (Topo- und Tomographie) erweitert. Die Vektoranalyse nach Alpins ist hierbei eine bekannte Methode zur Therapieplanung. Zur Therapie des Astigmatismus stehen konservative Optionen wie Brille oder torische Kontaktlinse sowie unterschiedlichste chirurgische Verfahren wie photorefraktive Keratektomie, Femtosekundenlaser-assistierte Keratotomie, Laser-in-situ-Keratomileusis, „small-incision lenticule extraction“ und die Implantation torischer Intraokularlinsen zur Verfügung.

[Astigmatism]

Astigmatism is the most frequent refractive error worldwide followed by hyperopia and myopia. Internal astigmatism has to be differentiated from external astigmatism. Furthermore, external astigmatism can be divided into "with the rule", "against the rule" and "oblique". The summation of internal and external astigmatism results in the refractive cylinder. Astigmatism has for a long time been regarded as a two-dimensional phenomenon; however, only a three-dimensional consideration expanded the view on existing analytical methods (topography and tomography). Alpins' vector analysis is a commonly used method for treatment planning. Multiple options exist for treatment of astigmatism with conservative approaches, such as eyeglasses or toric contact lenses as well as various surgical procedures, such as photorefractive keratectomy, femtosecond laser-assisted keratotomy, laser in-situ keratomileusis, small incision lenticule extraction and toric intraocular lens implantation.

[Multifocal intraocular lens (MIOL) surgery in young non-presbyopic ametropes : Reasonable and safe?]

BACKGROUND

Refractive lens exchange and implantation of a multifocal intraocular lens (MIOL) is mainly advised for ametropes with presbyopia. Non-presbyopic young ametropes who wish spectacle-independence are usually treated with corneal refractive surgery or phakic lenses.

OBJECTIVES

This retrospective case series aimed to analyse the refractive and subjective satisfaction outcome after MIOL surgery in both eyes of non-presbyopic ametropes where other treatment options were not possible.

MATERIALS AND METHODS

This retrospective case series comprised consecutively treated 32 eyes of 16 patients (5 myopic, 11 hyperopic patients; mean age 31 ± 6 years) who wished spectacle-independence and thus received an aspheric bifocal biconvex refractive-diffractive single-piece MIOL (Acri.Lisa 366/809, Carl Zeiss Meditec AG). Refractive data prior to and after surgery as well as subjective satisfaction at the 1‑year follow-up examination were assessed.

RESULTS

Related to distance corrected near visual acuity myopic eyes had a median efficacy index (EI) of 0.92 (±0.20) and hyperopes of 0.91 (±0.12) (P = 0.415). For intermediate vision, in both groups a lower EI (<0.5; P = 0.188) resulted in lower subjective satisfaction, which was higher for near and distance vision. Some of hyperopic patients reported limitations in near and distance vision, only one hyperopic patient would not have chosen this surgery again. None had a related complication during the follow-up.

CONCLUSIONS

When neither laser refractive surgery nor implantation of a phakic lens is possible, young non-presbyopic ametropes do profit from MIOL surgery with an aspheric bifocal biconvex refractive-diffractive MIOL.

[Perspectives of laser-assisted keratoplasty: current overview and first preliminary results with the picosecond infrared laser (λ = 3 µm)]

BACKGROUND

This article provides a review of the current state of laser-assisted keratoplasty and describes a first proof of concept study to test the feasibility of a new mid-infrared (MIR) picosecond laser to perform applanation-free corneal trephination.

METHODS

The procedure is based on a specially adapted laser system (PIRL-HP2-1064 OPA-3000, Attodyne, Canada) which works with a wavelength of 3,000 ± 90 nm, a pulse duration of 300 ps and a repetition rate of 1 kHz. The picosecond infrared laser (PIRL) beam is delivered to the sample by a custom-made optics system with an implemented scanning mechanism. Corneal specimens were mounted on an artificial anterior chamber and subsequent trephination was performed with the PIRL under stable intraocular pressure conditions.

RESULTS

A defined corneal ablation pattern, e.g. circular, linear, rectangular or disc-shaped, can be selected and its specific dimensions are defined by the user. Circular and linear ablation patterns were employed for the incisions in this study. Linear and circular penetrating PIRL incisions were examined by macroscopic inspection, histology, confocal microscopy and environmental scanning electron microscopy (ESEM) for characterization of the incisional quality. Using PIRL reproducible and stable incisions could be made in human and porcine corneal samples with minimal damage to the surrounding tissue.

CONCLUSION

The PIRL laser radiation in the mid-infrared spectrum with a wavelength of 3 µm is exactly tuned to one of the dominant vibrational excitation bands of the water molecule, serves as an effective tool for applanation-free corneal incision and might broaden the armamentarium of corneal transplant surgery.

Pharmacotherapy of alcohol-withdrawal syndrome in hospitalised patients. Clinical and methodological aspects

Because of the unreliability of the alcoholic, these suggestions are only intended for inpatients. Effective agents are presented first, and then the often very different pharmacological concepts are critically reviewed. Physicians use target symptoms as checkpoints for the effective pharmacological treatment of the alcohol-withdrawal syndrome. Clomethiazole and benzodiazepines are regarded as proven monotherapeutics against delirium. However, their somatic side effects and above all the problems of drug dependence make it necessary to look for a lower-risk medication. In every case, physicians must look more closely into the possibility of treating the individual alcohol-withdrawal syndrome with an agent less liable to cause addiction. Attractive, adequately tested alternatives are now becoming available for the large number of withdrawal syndromes which are below the level of delirium in terms of severity. This paper discusses the significance of substances without dependence potential, e.g. carbamazepine. This aspect is of special interest for the psychiatrist, whose task it is to guarantee the patient's abstinence after detoxification. We also look at other possible advantages of these substances when given in combination with drugs of the alcohol-barbiturate group against severe alcohol-withdrawal syndromes. Following a discussion of priority questions for further research, we draw attention to methodological deficiencies in earlier evaluation studies, and make suggestions for improved designs of drug trials.