Statistical Evaluation of Correlated Measurement Data in Longitudinal Setting Based on Bilateral Corneal Cross-Linking

PURPOSE

In ophthalmology, data from both eyes of a person are frequently included in the statistical evaluation. This violates the requirement of data independence for classical statistical tests (e.g. t-Test or analysis of variance (ANOVA)) because it is correlated data. Linear mixed models (LMM) were used as a possibility to include the data of both eyes in the statistical evaluation.

METHODS

The LMM is available for a variety of statistical software such as SPSS or R. The application was applied to a retrospective longitudinal analysis of an accelerated corneal cross-linking (ACXL (9*10)) treatment in progressive keratoconus (KC) with a follow-up period of 36 months. Forty eyes of 20 patients were included, whereas sequential bilateral CXL treatment was performed within 12 months. LMM and ANOVA for repeated measurements were used for statistical evaluation of topographical and tomographical data measured by Pentacam (Oculus, Wetzlar, Germany).

RESULTS

Both eyes were classified into a worse and better eye concerning corneal topography. Visual acuity, keratometric values and minimal corneal thickness were statistically significant between them at baseline (p < 0.05). A significant correlation between worse and better eye was shown (p < 0.05). Therefore, analyzing the data at each follow-up visit using ANOVA partially led to an overestimation of the statistical effect that could be avoided by using LMM. After 36 months, ACXL has significantly improved BCVA and flattened the cornea.

CONCLUSION

The evaluation of data of both eyes without considering their correlation using classical statistical tests leads to an overestimation of the statistical effect, which can be avoided by using the LMM.

[The Effect of Multifocal Toric Lens Rotation on Visual Quality]

PURPOSE

The aim of the study was evaluation and comparison of rotational stability and the effect of multifocal toric intraocular lens rotation (T-MIOL) at visual quality of two types of intraocular lens AcrySof IQ ReSTOR Toric SND1Tx (Alcon Laboratories, Inc.) and AT LISA toric 909M (Carl Zeiss Meditec AG). There was evaluated a pseudophakic dysphotopsia based on patients subjective feelings as well as the independence on glasses and overall satisfaction with the visual quality after T-MIOLs were implanted.

METHODS

The retrospective study included 68 eyes (100 %) of 34 patients, who underwent an uncomplicated cataract surgery with multifocal toric intraocular lens was implanted. 68 eyes were divided into two groups. Group A consisted of 48 eyes (70,6 %) with AcrySof IQ ReSTOR Toric SND1Tx and group B included 20 eyes (29,4 %) with AT LISA toric 909M multifocal toric intraocular lenses were implanted. The T-MIOL position, planned axis and misalignment were evaluated one week and 6 months after surgery. Surgical lens reposition was indicated in case of worsening visual quality due to T-MIOL rotation from its planned position.

RESULTS

In the group of 68 eyes, the mean uncorrected distance visual acuity (UDVA) before surgery was 0,08 (n = 48) in group A and 0,09 (n = 20) in group B. The mean UDVA after T-MIOL were implanted improved to 0,83 ± 0,06 (n = 48) in group A and 0,75 ± 0,08 (n = 20) in group B. The mean UDVA in patients before T-MIOL surgical rotation was 0,57 ± 0,03 (n = 5) in group A and 0,59 ± 0,08 (n = 5) in group B. At six months after T-MIOL surgical rotation, the uncorrected distance visual acuity was 1,0 in both groups (p = 0.70). The surgical rotation of T MIOL was performed in 10 eyes (14,7 %) of 68 eyes (p = 0.48), in group A (n = 48) in 5 eyes (10,4 %) and in group B (n = 20) in 5 eyes (25,0 %). Mean deviation from the planned axis was 8,2 ± 1,78 degrees in group A and 13,4 ± 3,04 degrees in group B. At six months postoperatively, the T-MIOL rotational stability showed less than 5 degrees for all surgically rotated lenses in both groups. Mean cylinder decreased in all patients from -2,92 ± 1,85Dcyl to -0.85 ± 0.61Dcyl after surgery. The mean spherical equivalent for all patients decreased from 0,56 ± 4,75D to 0,06 ± 1,33D after surgery. Presence of disturbing fotic phenomenon had reported 11 (32.4 %) of 34 patients, 9 of them they were subsequently indicated T-MIOL reposition. All 34 patients were able to perform normal daily tasks independently on spectacle correction. At six months after surgery, there was very high satisfaction with the quality of postoperative vision in both groups.

CONCLUSION

Implantation of toric multifocal intraocular lens, both of AcrySof ReSTOR Toric SND1Tx (Alcon Laboratories, Inc.) and AT LISA toric 909M (Zeiss Meditec AG Carl) in cataract patients is safe and effective method to correct corneal astigmatism and maintain the visual multifocality. Early surgical T-MIOL reposition should be performed to put the T-MIOL to planned axis in steepest meridian if unwanted lens rotation is identified.

KEY WORDS

cataract surgery, toric multifocal intraocular lens, rotation, rotational stability, quality of vision.

[Cross-Linking in Keratoconus: "Epi-off" or "Epi-on"?]

Corneal cross-linking can halt the progression of keratoconus, but what is the best approach for treatment? There are a number of treatment options for keratoconus, but only corneal cross-linking (CXL) appears to halt the progression of the disease. To guarantee effective cross-linking, CXL treatment involves removal of the corneal epithelium prior to riboflavin application and ultraviolet light illumination - "epi-off" CXL. Several methods of "epi-on" (transepithelial) CXL have been proposed, such as keeping the corneal epithelium intact which should be less painful and help avoid other CXL-associated adverse events. The evidence so far is that epi-off CXL remains the most effective method of strengthening the cornea and slowing keratoconus progression - but transepithelial methods are gaining ground.

[Analysis of reasons of intraocular lenses explantation]

AIM

To analyze the reasons of intraocular lenses (IOL) explantation.

METHODS

Retrospective study of 22 eyes of 21 patients. Those patients underwent explantation of intraocular lenses between the years 2008 to 2011. The study group included two eye groups. Group A included eyes with explanted monofocal IOL (14 eyes of 13 patients) and group B included eyes with explanted multifocal IOL (8 eyes of 7 patients). Reasons requiring explantation were analyzed based on subjective patient complaints and on objective ocular findings in health documentation as well.

RESULTS

The most common indications of explantation in Group A of monofocal lenses were incorrect IOL power, followed by IOL luxation, decentration and IOL opacity. In Group B of multifocal IOL, the most common reasons for IOL removing were halo and glare, inadequate postoperative expectations and incorrect IOL power.

CONCLUSION

The main reason for IOL exchange in Group A of monofocal lenses was the incorrect power, while in Group B of multifocal IOL the main reason were the disturbing photic phenomenon like glare and halo. Careful patient selection, good surgical technique, optimally selected IOL power measurements based on precise biometry readings as well high quality of IOL materials are the most important factors in minimizing the risk for IOL explantation.

[Autoimmune ovarian failure in adolescent girls]

BACKGROUND

The aim of the study was to map the incidence of antiovarian antibodies (AOA) in adolescent girls with ovarian cycle irregularities in comparison with girls with the regular cycle. The relation between the AOA positivity and structural changes in the bioptic samples of ovaria was examined.

MATERIAL AND RESULTS

The studied cohort included 39 girls with primary amenorrhea (N = 18) and oligo/secondary amenorrhea (N = 21). All patients were tested for the presence of antiovarian antibodies (AOA) in the serum and levels of FSH and LH. The examination was done at the beginning of the study and after six months of therapy, in most of the cases by the hormone substitution treatment. In indicated cases the laparoscopic ovarian biopsy was done. A patients with serious failure of ovarian cycle the positivity of antibodies against various components of ovaria was found. Significantly higher levels of FSH was also found, LH levels were not higher. In our patients the depletion and alteration of the follicular apparatus in the cortex of ovaria belonged to the common findings. The control examination after the six month of hormonal substitution brought about lower levels of AOA, in some patients AOA fully disappeared.

CONCLUSIONS

Incidence mapping of antiovarian antibodies in patients with ovarian cycle irregularities correlate with findings of elevated atresia. Ovarian cycle irregularities can later or earlier turn into the extinction of the follicular apparatus and fibrotization of the ovarian cortex.

[Possibilities of surgical treatment of upper cervical spine in patients with rheumatoid arthritis]

PURPOSE OF THE STUDY

Patients with rheumatoid arthritis (RA) often suffer from instability of the upper cervical spine. The most common instability is anterior atlanto-axial subluxation (AAS). Instability may lead to neurologic deficits from spinal cord compression and intractable pain, decreasing quality of life and its length.

MATERIAL AND METHODS

This prospective study analyzed different fixation methods and the influence of atlanto-axial and occipito-cervical fusion on clinical and radiological outcome. 41 patients with RA with instability of the upper cervical spine were treated surgically for progressive instability, pain and neurological deficit. Average age of our patients was 52.4 years (21-76 years). At the time of surgery, duration of the disease was in average 18.6 years (2-47 years). Patients had advanced stage of the disease according to Steinbroker, on hands stage 3.7 and feet stage 2.9. Atlanto-axial fixation was done for AAS in 27 (24 Magerl transarticular fixations and Brooks-Jenkins technique in 3 patients). Occipito-cervical fusion was done in 13 patients (3 with Ransford loop and sublaminar wires and 9 with CerviFix). One patient was managed in halo-cast fixation. Spinal fusion was performed in all patients using autologenous bone graft. Patients were evaluated by using Functional Rating Index (FRI), Health Assessment Questionnaire (HAQ) and visual pain analogue scale (VAS) before and after surgery in set intervals, when radiological examination was also performed including dynamic films.

RESULTS

Three patients died in the postoperative period (3 weeks, 11 and 18 months). 38 patients remained for follow up, which was in average 28.4 months. Fusion was considered when hardware was intact and patient was satisfied, no motion was detected on dynamic X rays or bony fusion was clearly visible. Fusion was assessed in 40 patients, 32 fused, 8 had fibrous non-union. 3 of these patients had hardware failure. 9 patients had preoperatively verified panus formation peridentally, which resorbed after the surgery. FRI evaluation was done in 40 patients, 30 improved (14 patients by more than 10 points), 6 patients did not change and 4 worsened. The improvement after 3 and 12 months was statistically significant (p < 0.001). Average HAQ score decreased after surgery, but the change was not statistically significant (p > 0.05). Average VAS score decreased significantly after surgery (p < 0.05). There were 5 hardware related complications including one vertebral artery injury. None of these complications required subsequent surgery nor had any influence on good clinical outcome.

DISCUSSION

Results of FRI and VAS show the benefit from early indication of surgical stabilization of upper cervical spine in patients with RA. Based on our experience, as well as other authors, fixation of AAS by transarticular screw fixation according to Magerl is the preferred method in the younger patient group. Once destruction of the atlanto-axial joints, lateral subluxation or cranial migration of the dens is present, occipito-cervical fusion using titanium malleable implant (CerviFix) is necessary.

CONCLUSION

Positive clinical outcomes advocate early surgical intervention as described in recent literature. Surgery prevents subsequent neurological damage life quality deterioration and shortening of life expectancy.

Determination of biogenic amines in cheese by ion exchange chromatography

A sensitive, fully automated method, yielding reproducible results, was developed for the determination of relevant biogenic amines in cheese. Histamine, tyramine, putrescine, cadaverine, tryptamine, agmatine, spermidine and spermine were separated in the ion exchanger of OSTION LG ANB column of the automatic amino acid analyser Mikrotechna 339 T. Elution was carried out at 60 degrees C using a system of two buffers. The samples were extracted and precipitated by trichloroacetic acid and purified, after removal of fat, by membrane filtration. The recovery for individual amines in cheese ranged between 86% and 108%. The detection limit was of 1-5 mg of the respective amine per 1 kg of cheese and the method was linear within the dose range of 0.1-10 micrograms (for tryptamine 0.5-10 micrograms).

[The picture of focal liver disease in ultrasound, computer tomography and angiography]

In a group of 25 patients examined by sonography, computer tomography and angiography with diagnoses confirmed during operation and by histology, the author compared the efficiency of the individual methods and a complex examination. Computer tomography proved to be the most efficient method which enabled, in addition to precise localization, appreciation of size and relation of the pathological focus to adjacent structures, to determine their nature in some. The complex examination in indicated cases significantly increased the diagnostic efficiency.

[Indications for liver resection]

In a group of 103 resections of the liver made in 1978-1987 at the Surgical Clinic of the Medical Faculty of Hygiene, Charles University the authors evaluated the diagnostic possibilities of circumscribed hepatic lesions. They evaluated orientational and aimed methods which make it possible to plan the extent of the surgical operation. The diagnostic system elaborated by the authors makes it possible to outline the indications more accurately and serves the elaboration of the tactics of the operation proper.