Bewertung und Qualitätssicherung refraktiv-chirurgischer Eingriffe durch die DOG und den BVA

Dynamic torsional misalignment of eyes during laser in-situ keratomileusis

PURPOSE

To determine the amount and characteristics of dynamic torsional misalignment of eyes during excimer ablation in laser in-situ keratomileusis (LASIK).

METHODS

Retrospective trial for evaluation of dynamic intraoperative torsional misalignment of 179 eyes that underwent LASIK for correction of myopia and/or astigmatism. Patients were treated with the Keracor 217z excimer laser implementing 25 Hz dynamic eye tracker ACE 100 (both Technolas Perfect Vision, Munich, Germany). From dynamic torsional misalignments, temporal power spectra were obtained by Fourier analysis up to a frequency of 12.5 Hz and an amplitude of ±15° from initial torsional status (limited by the tracking system). The f90, f95, and f99 criteria were defined as the frequency below which 90 %, 95 %, and 99 % of misalignments occur. A Wilcoxon rank sum test was performed to detect differences of f90, f95, and f99 in groups' gender, age, and eye (if both eyes underwent surgery at same day). Multiple regression analysis (MRA) was performed to evaluate possible preoperative predictors of f90, f95, and f99.

RESULTS

Fourier analysis showed a dominance of high-frequency, low-power dynamic torsional misalignment. Mean f95 threshold of rotational movements was 4.89±2.12 Hz (median 4.54, ranging from 0.44 to 9.23 Hz). Wilcoxon rank sum test showed no differences in f90, f95, and f99 between groups' gender, age, and eye. MRA revealed age, gender, and optical zone as preoperative predictors on intraoperative f90, f95, and f99.

CONCLUSIONS

Dynamic intraoperative torsional misalignments of eyes undergoing LASIK are dominated by low-frequency (slow), high-power (large) movements, with 95 % being slower than 4.89Hz regarding the spectrum analyzed (0-12.5Hz, ±15°). Movements can be predicted preoperatively by eye treated, patients' gender, and age in pre-LASIK diagnostics.

[Complications of corneal lamellar refractive surgery]

Techniques available for corneal lamellar refractive surgery are laser-assisted in situ keratomileusis (LASIK) using a microkeratome or femtosecond laser incision followed by excimer laser corneal ablation, and femtosecond laser-assisted refractive lenticule extraction (ReLEx). These treatments are nowadays considered to be safe and effective standard procedures for surgical correction of mild to moderate ametropia. Possible complications include too small or decentered optical zones, intraoperative flap cutting errors and postoperative inflammation (e.g. diffuse lamellar keratitis, DLK), epithelial or flap folds, epithelial ingrowths or iatrogenic ectasia. The occurrence of complications may be significantly reduced by compliance to corresponding standards of indication and treatment that are based on current scientific knowledge.

[Avoidance and management of complications in laser in situ keratomileusis]

Laser in situ keratomileusis (LASIK) is now considered to be a safe and effective standard procedure for surgical correction of low to medium ametropia. Nevertheless, as in any other surgical intervention complex courses may occur in single rare cases. Possible complications include, but are not limited to, optically effective errors, such as too small or decentered optical zones as well as intraoperative flap cutting errors and postoperative complications, such as inflammation (e.g. diffuse lamellar keratitis, DLK), epithelial or flap folds, epithelial ingrowths or iatrogenic ectasia. Compliance to standards for indications and treatment based on the current scientific knowledge can significantly reduce the occurrence of complications. These standards include adjustment of the optical zone to the mesopic pupil diameter, the application of state of the art eye trackers, careful performance of intraoperative and postoperative procedures by a surgeon experienced in the entire spectrum of ocular surgery, the possibility of treating complications directly on occurrence and, last but not least, conservative patient selection and choice of treatment.

Anterior chamber depth and iridocorneal angle in healthy White subjects: effects of age, gender and refraction

PURPOSE

Prior to phakic intraocular lens implantation, it is important to obtain precise knowledge of the anterior chamber depth (ACD). Accurate topographic evaluation of the iridocorneal angle is helpful in estimating risk for angle-closure glaucoma. This study investigated the use of the Orbscan II system to measure ACD and the iridocorneal angle in healthy subjects and assessed the influences of age, gender and spherical equivalent on these parameters.

METHODS

The Orbscan II system was used to determine the ACD and iridocorneal angle in eight different positions in 390 healthy White subjects with a mean age of 41± 16years (range 10-80 years). The sample included 242 male and 148 female subjects. The influences of age, gender and spherical equivalent were assessed using multiple regression analysis.

RESULTS

Mean ACD was 2.87 ± 0.04 mm in male subjects and 2.81±0.37mm in female subjects. The explanatory variables relevant to the ACD were age (partial regression coefficient B = -0.0115, p < 0.0001), spherical equivalent (B = - 0.0562, p< 0.0001) and gender (B = 0.0996, p=0.0036). The mean iridocorneal angle (MIA) was 30.7 ± 2.0 ° in male and 31.6 ± 2.1° in female subjects. The variables relevant to the MIA were gender (B =- 0.865, p < 0.0001), age (B =- 0.017, p = 0.0007) and spherical equivalent (B = - 0.121, p = 0.001). The superior iridocorneal angle displayed the strongest negative correlation with age, whereas the temporal angle exhibited the least correlation with age.

CONCLUSIONS

The decline in ACD appears to be linear with age, amounting to a mean of 0.58 mm over 50 years. This may become clinically relevant in the use of phakic intraocular lenses. In addition, the angle is more severely constricted in the superior quadrant than in the temporal quadrant.

[Cataract surgery. Effect on the posterior segment of the eye]

Cataract surgery is a safe procedure with a high patient satisfaction rate. However, pseudophakia changes the physiology of the eye and immediate changes include release of inflammatory cytokines. Deformation of the globe and intraoperative fluctuations of intraocular pressure may induce microlesions and alterations of ocular perfusion. The barrier function between the anterior and the posterior segment is compromised after surgery and the geometry of the intraocular chambers changes. Especially the vitreous body is subject to increased destruction during the years after surgery. The occurrence of pseudophakic cystoid macular edema after cataract surgery is a well known complication. Several studies have described a progression of diabetic retinopathy, especially of diabetic macular edema after cataract surgery. In contrast cataract surgery does not seem to have a significant impact on the progression of age-related macular degeneration. However the risk for retinal detachment is significantly increased in pseudophakia for at least 10 years after surgery. Awareness of special risk factors can make cataract surgery, one of the most effective procedures in medicine, even safer.

[The basics of refractive lens exchange]

Removal of the crystalline lens and its replacement by an intraocular lens (IOL) is known as refractive lens exchange (RLE). RLE is performed to correct high ametropia or aniseikonia. Crystalline lens removal always leads to a complete loss of accommodation; therefore, RLE should mainly be used for patients with beginning or existing presbyopia. RLE patients usually have a good best-corrected visual acuity, which is the default value for the postoperative uncorrected visual acuity. To reach this goal, microincisional and astigmatism-neutral implantation techniques as well as special IOL optic designs are available. These optic designs offer each patient individualized best visual performance. In spite of the high requirements for postoperative optical quality, RLE can lead to an effective, safe, predictable, and stable outcome with a low risk of complications.

Basic knowledge of refractive surgery: correction of refractive errors using modern surgical procedures

INTRODUCTION

Refractive ophthalmic surgery allows refractive errors to be corrected permanently in a safe, effective, and reliable way with few complications.

METHODS

Selective literature review with special reference to the guidelines of the German Commission for Refractive Surgery.

RESULTS

With a total of almost 18 million treatments performed to date, laser in-situ keratomileusis (LASIK) is the most commonly used refractive surgical procedure worldwide. Alternatives to LASIK include surface ablation procedures (PRK, LASEK, Epi-LASIK) and phakic intraocular lens implantation. If ocular accommodation is lost, removal of the crystalline lens and implantation of modern multifocal intraocular lenses (refractive lens exchange) provide an alternative means of correcting myopia, hyperopia and presbyopia.

DISCUSSION

The treatment effect is maximized and complications kept to a minimum if strict inclusion criteria are applied and a high technical standard maintained during the procedure.

Komplikationen nach refraktiver Chirurgie im Ausland

BACKGROUND

In this article a retrospective analysis of patients presenting at a German university following refractive surgery abroad is presented.

PATIENTS AND METHODS

A total of 20 cases of patients who had undergone treatment between 1998 and 2006 in China (1 case), Greece (1 case), Iran (1 case), Russia (2 cases), Switzerland (1 case), Slovakia (1 case), Spain (2 cases), South Africa (3 cases), Turkey (6 cases) and the USA (2 cases) were analyzed retrospectively.

RESULTS

The following complications were observed: epithelial ingrowth into the interface with or without melting of the flap (6 cases), corneal ectasia (2 cases), dislocation of a phakic posterior chamber intraocular lens and prolapse into the anterior chamber with endothelial cell loss (1 case), secondary increase of intraocular pressure following implantation of a phakic intraocular lens (1 case), flap-related complications following laser-in-situ keratomileusis (LASIK) (2 cases), keratitis (1 case), dislocation of the complete flap (1 case), diffuse lamellar keratitis (DLK) grade IV (1 case), hyperopia as a consequence of radial keratotomy (1 case), and under correction/over correction and poor optical quality following laser epithelial keratomileusis (LASEK) and LASIK for high myopia (5 cases) with possible early corneal ectasia.

CONCLUSIONS

There are four important problems arising from refractive surgery abroad, often referred to as "LASIK tourism": wrong indications, insufficient management of complications, lack of postoperative care and the health economic aspect.