Femtosecond laser lenticule transplantation in rabbit cornea: experimental study

PURPOSE

To evaluate the feasibility of femtosecond laser-induced lenticule transplantation in the rabbit cornea and to observe the relative histologic characteristics of corneal tissue and nerve repair after transplantation.

METHODS

Eight healthy, purebred, New Zealand white rabbits underwent femtosecond laser small-incision lenticule extraction (SMILE) surgery in the right eye. Lenticules were inserted into a femtosecond laser-created corneal stromal pocket in the left eye, which was defined as femtosecond laser corneal lenticule transplantation. Postoperative observation and examination were completed to evaluate the surgery.

RESULTS

In the early postoperative period, inflammation of the cornea was noted, tissue around the lenticule was edematous, and cells were activated. Tissue edema remained at postoperative day 10. By 1 month, edema had resolved, activated cells gradually became quiescent, and nerve fiber regeneration was observed. By 3 months, the lenticule integrated into the recipient cornea, extracellular matrix gradually cleared, and thicker nerve fibers were noted. By 6 months postoperative, morphology and distribution of the corneal stromal fibers were close to normal, and the number of nerve fibers was reduced.

CONCLUSIONS

Femtosecond laser corneal lenticule transplantation in rabbits is feasible, as the lenticule was shown to thrive and integrate with the recipient stroma. Nerve regeneration begins after 1 month.

The effect of segment selection on acoustic analysis

OBJECTIVE/HYPOTHESIS

Acoustic analysis is a commonly used method for quantitatively measuring vocal fold function. Voice signals are analyzed by selecting a waveform segment and using various algorithms to arrive at parameters such as jitter, shimmer, and signal-to-noise ratio (SNR). Accurate and reliable methods for selecting a representative vowel segment have not been established.

STUDY DESIGN

Prospective repeated-measure experiment.

METHODS

We applied a moving window method by isolating consecutive, overlapping segments of the raw voice signal from onset through offset. Ten normal voice signals were analyzed using acoustic measures calculated from the moving window. The location and value of minimum perturbation/maximum SNR was compared across individuals. The moving window method was compared with data from the whole vowel excluding onset and offset, the mid-vowel, and the visually selected steadiest portion of the voice signal.

RESULTS

Results showed that the steadiest portion of the waveforms, as defined by minimum perturbation and maximum SNR values, was not consistent across individuals. Perturbation and nonlinear dynamic values differed significantly based on what segment of the waveform was used. Other commonly used segment selection methods resulted in significantly higher perturbation values and significantly lower SNR values than those determined by the moving window method (P<0.001).

CONCLUSIONS

The selection of a sample for acoustic analysis can introduce significant inconsistencies into the analysis procedure. The moving window technique may provide more accurate and reliable acoustic measures by objectively identifying the steadiest segment of the voice sample.

Perturbation and nonlinear dynamic analysis of adult male smokers

OBJECTIVE

Smoking results in a voice change, and the perception by smokers of an abnormal voice may encourage quitting behavior. Moreover, a disordered voice is often the first sign of vocal pathology. Efforts to evaluate voice have focused on classical acoustic analysis; however, nonlinear dynamic analysis has been shown to be a reliable objective method for the evaluation of voice. We compare the discriminatory ability of these two methods when applied to normal and smokers' voices.

STUDY DESIGN

Prospective study.

METHODS

The study included 73 subjects, 36 nonsmokers and 37 smokers. A segment of sustained vowel production was obtained from each subject. Acoustic dimension and correlation dimension (D2) analyses were applied to the data. Results were compared with a Mann-Whitney rank sum test, logistic regression, and receiver operating characteristics (ROC) analysis.

RESULTS

D2 values for smokers were significantly higher than D2 values for nonsmokers (P<0.001). Jitter and shimmer analysis showed higher values for these parameters among smokers. Logistic regression indicated a higher predictive power with D2, and ROC analysis found no significant difference between the analysis methods.

DISCUSSION

This study indicated that D2 is highly sensitive to changes associated with smoking and has the potential to be implemented clinically as an indicator of abnormal voice. Further research could focus on using nonlinear dynamic analysis to create a normative database, producing standards for monitoring voice changes caused by cigarette smoking.

Inhibitory effect on LPS-induced retinal microglial activation of downregulation of t-PA expression by siRNA interference

PURPOSE

This study investigated the expression and release of tissue plasminogen activator (t-PA) in lipopolysaccharide (LPS)-induced retinal microglia activation. We evaluated change in microglia activation following down-regulation of t-PA expression by siRNA interference.

METHODS

The primary cultured microglia cells were isolated from retinas of S-D rats and activated with different concentration of LPS (0, 3, 10, 30, 100, and 300 ng/ml). Double immunofluorescence (OX42 and tPA) and Western blot were used to detect t-PA expression. Next, tPA expression was down-regulated by siRNA interference, the microglia transfected with tPA siRNA lentivirus or blank control lentivirus were activated with 30 ng/ml of LPS, the culture supernatant was collected 1, 3, 6, 12, and 24 hours after LPS treatment for IL-1beta and TNF-alpha ELISA assays, and the cells were collected 24 hours later for immunocytochemistry of microglia markers (OX42 and Iba-1) and quantitative real-time PCR to determine the inhibitory efficiency of t-PA siRNA. Transfection efficiency was evaluated with flow cytometry by EGFP expression.

RESULTS

The microglia expressed t-PA when treated with LPS in a dose-dependent pattern. The expression was down-regulated by siRNA interference markedly; the inhibitory efficiency was 80% as determined by quantitative real-time PCR. Transfection efficiency during siRNA interference was 88%. The expression of Iba-1 and the release of IL-1beta and TNF-alpha were inhibited significantly when the t-PA expression was knocked down.

CONCLUSIONS

Activated microglia express t-PA. Down-regulation of t-PA expression can inhibit the activation of microglial cell.

Phonation threshold flow measurements in normal and pathological phonation

OBJECTIVES/HYPOTHESIS

Phonation threshold flow (PTF) may provide a tool to assess laryngeal function and could differentiate between normal and pathological voices. Both polyps and nodules contribute to an increased PTF by creating an incomplete glottal closure and increased vocal fold mass and thickness.

STUDY DESIGN

Prospective study.

METHODS

The Kay Elemetrics Phonatory Aerodynamic System (PAS) (Kay Elemetrics Corp., Lincoln Park, NJ) was used to collect mean flow rate (MFR) and PTF measurements from 40 normal subjects, 21 patients with vocal fold nodules, and 23 patients with vocal fold polyps. Gender-based differences were assessed using a t test. The effect of vocal pathology on PTF and MFR was determined with an ANOVA. Diagnostic potential was evaluated using a receiver operation characteristics (ROC) analysis.

RESULTS

Both PTF (P = .047) and MFR (P = .008) were significantly affected by gender. Using a two-way ANOVA and correcting for gender differences, the influence of pathology on PTF was determined to be significant (P < .001). Post hoc tests found a significant difference between normal and polyp subjects (P < .001) but not normal and nodule subjects (P = .177) or nodule and polyp subjects (P = .246). ROC analysis found that PTF (area under the curve [AUC] = 0.691) and MFR (AUC = 0.684) had a similar diagnostic utility.

CONCLUSIONS

PTF can be used to differentiate between normal and pathological voices. As a parameter that is experimentally sensitive to the biomechanical parameters providing its theoretical basis, it could be used clinically to analyze laryngeal functionality. Future research could focus on measuring PTF in other pathologies, such as paralysis or scarring, which would also affect the effort required to produce voice.