Botulinum toxin and facial wrinkles: a new injection procedure

BACKGROUND: Anterior stromal keratocyte cells undergo programmed cell death (apoptosis) in response to corneal epithelial injury. Keratocyte apoptosis may be an initiator of the corneal wound healing response that includes keratocyte proliferation and activation, as well as changes to the overlying epithelium, occurring following refractive surgical procedures such as photorefractive keratectomy (PRK). This study compared the effect of laser-scrape and transepithelial PRK on keratocyte apoptosis. METHODS: Photorefractive keratectomy was performed in both eyes of 10 New Zealand white rabbits using the Summit Apex excimer laser. Surgery was performed using transepithelial PRK in one eye and laser-scrape PRK in the other. The central cornea was analyzed at 4 hours after surgery using a quantitative TUNEL assay that detects fragmented DNA characteristic of apoptosis. Hepatocyte growth factor (HGF) production by keratocytes was detected by immunocytochemistry. RESULTS: Average apoptotic cells per 400X microscopic field determined by 2 independent masked observers were 0.9 +/- 0.5 (scanning electron microscopy) and 0.2 +/- 0.2 in the transepithelial PRK group compared with 5.1 +/- 2.9 and 4.1 +/- 3.2 in the laser-scrape group. The difference between the two groups was statistically significant for both observers (P < .05, ANOVA). HGF was detected within keratocytes throughout the corneal stroma. Less HGF was detected in the anterior stroma in the laser-scrape group at 4 hours after surgery, consistent with more anterior keratocyte apoptosis in this group. CONCLUSIONS: Transepithelial PRK induced less anterior keratocyte apoptosis in rabbits than laser-scrape PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and subepithelial scarring.     

Mathematical simulation of retinal image contrast after photorefractive keratectomy with a diaphragm mask

BACKGROUND: Photorefractive keratectomy (PRK) using a dilating diaphragm mask engraves a delicate three-dimensional staircase pattern into a formerly smooth corneal surface. The created steps are later smoothed by tear film and wound healing processes. The present study investigates, in a mathematical simulation, the effects that such staircase patterns and their smoothing may have on retinal image contrast. METHODS: All simulations are based on the Gullstrand eye model and calculate retinal image contrast from point spread function (PSF) analysis of Gullstrand eyes treated by simulated PRK under various conditions. RESULTS: The simulations indicate that PRK can reduce retinal contrast markedly. The most critical factor for such a reduction is the step height of the ablation pattern. With step heights below 0.4 microns, loss of contrast due to the created staircase pattern is always moderate and should be restored during early wound healing. Complete wound healing may smooth out larger step heights. Micromovements during PRK also can lead to partial loss of retinal image contrast. CONCLUSIONS: Simulation of retinal contrast after PRK shows that step heights below 0.4 microns seem to be acceptable. A minimization of the micromovements during PRK can offset some of the reduction of retinal contrast.     

Interaction of invasive bacteria with host signaling pathways

PURPOSE: Programmed cell death (apoptosis) is the controlled death of cells that occurs with minimal collateral damage to surrounding cells or tissue during development, homeostasis, and wound healing. The authors hypothesize the keratocyte apoptosis is an initiating factor in the wound-healing response after refractive surgical procedures. To evaluate the effects of different corneal manipulations, keratocyte apoptosis was examined qualitatively and quantitatively after traditional epithelial scrape-photorefractive keratectomy (PRK), transepithelial PRK, removal of a cap of superficial cornea using a microkeratome, production of a flap of superficial cornea with a microkeratome, and laser-assisted in situ keratomileusis (LASIK) compared with unwounded controls in rabbit corneas. METHODS: Refractive surgical procedures or their components were performed in rabbit eyes. Keratocyte apoptosis was monitored using the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling assay to detect DNA fragmentation. Cellular morphologic changes were evaluated by electron microscope examination. RESULTS: Keratocyte apoptosis was noted with each refractive procedure or corneal manipulation and was variable from eye to eye with each procedure. Transepithelial PRK was associated with the lowest levels of central corneal apoptosis, even if the stromal surface was scraped after the procedure. Keratocyte apoptosis is confined to the superficial stroma extending to a depth of approximately 50 microns to 75 microns after epithelial scrape-PRK and transepithelial PRK. Apoptosis was noted in the deeper central corneal keratocytes located anteriorly and posteriorly to the lamellar cut in LASIK. CONCLUSIONS: There are qualitative and quantitative differences in keratocyte apoptosis between LASIK, epithelial scrape-PRK, and transepithelial PRK. Epithelial injury is an important factor modulating keratocyte apoptosis. The level and distribution of keratocyte apoptosis, along with subsequent repopulation by activated stromal keratocytes, are likely to be important determinants of corneal wound healing associated with variability and regression after PRK and LASIK. Transepithelial PRK induces low levels of keratocyte apoptosis, and, therefore, this approach may be useful for treating higher levels of myopia and for retreatment after regression.     

Levels and patterns of alcohol consumption using timeline follow-back, daily diaries and real-time "electronic interviews"

BACKGROUND: Basic knowledge of the substances involved in wound healing after photorefractive keratectomy (PRK) is essential for development of pharmacological intervention. We present preoperative and postoperative analysis of tear fluid extracellular matrix proteins and cytokines after PRK. METHODS: Tear fluid samples from 70 patients (72 eyes) who had PRK (38 women and 32 men, mean age 31.5 yr) were studied. Samples from 18 patients (18 eyes) were analyzed in two different studies. RESULTS: Mean preoperative tear fluid flow in the collection capillary (volume divided by tear collection time) varied from 4.5 to 22.5 microliters/min in five series of patients. It increased significantly during the first two postoperative days (range of means, 55.5 to 88.8 microliters/min, p < 0.01), and decreased to the preoperative level by day 7 (range of means, 9.7 to 18.2 microliters/min). The tenascin and cytokine release rates increased significantly during the first two days after PRK and returned to the preoperative level by day 7. Mean +/- standard error for tenascin: day 0 (5.2 +/- 1.9 ng/min); day 2 (22.7 +/- 6.1 ng/min; p = 0.02). Mean +/- standard error for HGF: day 0 (3.2 +/- 0.7 pg/min); day 1 (22.8 +/- 4.2 pg/min; p = 0.0003). Mean +/- standard error for TGF-beta 1: day 0 (63.3 +/- 19.6 pg/min); days 1-2 (826.2 +/- 253.7 pg/min; p = 0.001). Mean +/- standard error for VEGF: day 0 (166.0 +/- 29.6 pg/min); days 1-2 (824.4 +/- 165.1 pg/min; p = 0.0007). Mean +/- standard error for PDGF-BB: day 0 (0.42 +/- 0.19 pg/min); day 2 (27.6 +/- 5.8 pg/min; p = 0.0000). Mean +/- standard error for TNF-alpha: day 0 (9.5 +/- 2.6 pg/min); day 2 (28.6 +/- 5.9 pg/min; p = 0.003). Excluding PDGF-BB, all substances studied were present in normal human tear fluid. PDGF-BB was present in only 17% of the preoperative samples. CONCLUSION: Corneal wounding induces an increased release of several growth modulating cytokines which may be involved in healing processes.     

Confocal microscopic characterization of wound repair after photorefractive keratectomy

PURPOSE: Development of postoperative corneal haze and regression of refractive effect are unfavorable clinical complications of excimer laser photorefractive keratectomy (PRK). Although exact mechanisms remain to be elucidated, these outcomes have been attributed to post-PRK corneal wound healing. The purpose of this study was to evaluate corneal wound repair quantitatively after PRK in a rabbit model using a newly developed in vivo technique, termed confocal microscopy through focusing (CMTF). METHODS: Twelve rabbit corneas received a monocular, 6-mm diameter, 9.0-diopter PRK myopic correction. Animals were evaluated sequentially up to 6 months after surgery by in vivo CMTF, which uses an image-intensity depth profile to measure epithelial and stromal thickness and uses corneal light reflectivity as an objective estimate of corneal haze. At differing temporal intervals, in vivo morphology was correlated with ex vivo histology using fluorescence microscopy. RESULTS: One week after PRK, an acellular layer of 86 +/- 24 microns was found anteriorly in the remaining stroma, which demonstrated surgically induced keratocyte death. Underlying keratocytes became activated and migrated toward the wound bed; repopulation was completed within 3 weeks. One week after PRK, there was a significant increase (P < 0.001) in light reflections detected from the photoablated stromal surface (1745 +/- 262 U) and from the underlying activated fibroblasts (713 +/- 607 U). Corneal reflectivity peaked at 3 weeks (4648 +/- 1263 U) and decreased linearly to 889 +/- 700 U by 6 months after the PRK; this corresponded to a reflectivity six times greater than the level seen in unoperated corneas. Two weeks after PRK, initial corneal edema had resolved, revealing an actual ablation depth (maximal stromal thinning) of 118 +/- 8 microns. Starting at 2 weeks after surgery, the stroma underwent gradual rethickening that reached 98% of the preoperative thickness at 6 months after PRK; at that time, only 6% of the initial photoablation depth persisted. By contrast, the central corneal epithelium showed no significant postoperative hyperplasia. CONCLUSIONS: Rabbit corneas treated by PRK showed a remarkable stromal wound-healing response that ultimately led to the restoration of the original stromal thickness by 6 months after surgery, demonstrating complete regression of the initial photoablative effect. Additionally, corneal wound healing was associated with increased light reflections from both the photoablated stromal surface and the activated wound-healing keratocytes underlying this area. Based on these findings, the authors hypothesize that the development of clinically observed corneal haze in PRK patients may be related, in part, to activation of corneal keratocytes and to putative changes in the extracellular matrix.     

Gelatinase B and A expression after laser in situ keratomileusis and photorefractive keratectomy

OBJECTIVE: To compare the expression of gelatinases in the corneal epithelium and stroma after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: Rabbit eyes were treated with LASIK (n=11), PRK (n=12), or corneal flap construction (n=12); 4 eyes served as unwounded controls. Zymography was performed on the central epithelium and the stroma 1, 3, and 7 days after surgery to determine the expression of gelatinases. RESULTS: Epithelial expression of gelatinase B in the LASIK group (0%-25%) was lower than that in the PRK group at all time points (50%-100%) and was identical to the corneal flap group. Stromal expression of gelatinases A and B was similar after LASIK and PRK, but was minimal after corneal flap construction at all time points. Epithelial expression of gelatinase A was similar for the first 3 days after LASIK and PRK but not thereafter. CONCLUSIONS: Gelatinase B epithelial expression was up-regulated after PRK but not after LASIK. Gelatinase B stromal expression was up-regulated after both procedures. CLINICAL RELEVANCE: Differences in wound healing and subepithelial scarring after these 2 procedures may be related to gelatinase B.     

Wound healing following intrastromal photorefractive keratectomy with the Nd:YLF picosecond laser in the cat

BACKGROUND: We studied the histopathology of the stromal wound healing response in the cat cornea following intrastromal photorefractive keratectomy (IPRK) with the Nd:YLF picosecond laser. METHODS: Intrastromal PRK was performed in the anterior stroma of cat corneas with the Nd:YLF picosecond laser. The cats were sacrificed at predetermined intervals ranging from immediately to 6 months postoperatively. Effects of the laser treatment on the epithelium, Bowman's layer, stroma, and the endothelium were evaluated using light and scanning electron microscopy. No anti-inflammatory agents were used. RESULTS: Intrastromal PRK resulted in no perceptible damage to the corneal epithelium or Bowman's layer either acutely or at 6 months. The corneal stroma showed multiple cavitations immediately after intrastromal PRK, which collapsed over several hours, followed by thinning of the cornea over 2 weeks. At 1 month, the stromal collagen was abnormal with surrounding hypercellularity. The endothelium showed no injury, acutely or at 6 months. No thermal effects on stromal collagen were observed at 6 months, and disruption of the lamellar pattern was not apparent after the cavitation bubbles were reabsorbed. CONCLUSION: Intrastromal PRK can effectively remove stromal tissue without acute damage to the adjacent lamellae, epithelium, or endothelium. There is a transient cellular wound healing response associated with a transient stromal collagen abnormality at 2 weeks to 1 month, which was not apparent 2 months after the procedure.     

Changes in corneal epithelial barrier function after excimer laser photorefractive keratectomy

PURPOSE: To use fluorophotometry to measure corneal epithelial barrier function after excimer laser photorefractive keratectomy (PRK). SETTING: Seoul National University Hospital, Seoul, Korea. METHODS: Twenty-five eyes of 21 patients (13 women, 8 men) had PRK to correct myopia. Corneal epithelial healing time was measured and corneal epithelial permeability to sodium fluorescein evaluated by fluorophotometry 1, 2, and 3 weeks after surgery. RESULTS: Epithelial permeability showed a statistically significant increase 1 week after surgery and returned to its preoperative level 1 week later. Comparative studies according to epithelial healing day and corrected diopter showed results that were not statistically significant (P > .05). CONCLUSION: These results suggest that PRK delays complete reconstruction of corneal epithelial barrier function. In humans, the corneal epithelium regained its normal barrier function 2 weeks after PRK. Thus, at least during these weeks, care should be taken to minimize further epithelial trauma.     

Transcendence: the meaning of great-grandmothering

OBJECTIVE: To investigate the wound healing of the cornea following 193 mm excimer laser photorefractive keratectomy (PRK) and the effects of corticosteroid on it. METHODS: PRK was performed on both eyes of 6 monkeys. Corticosteroid was given to the right eyes, but not to the left ones. At 4 days, 1 week, 2 weeks, 1 month, 3 months and 6 months, corneal pachymetry was examined and the eyes of one monkey were enucleated and the corneas were stained immunohistochemically for collagen type III, type IV and type VII, fibronectin and laminin. RESULTS: The expression of collagen type Vii recovered to the normal linear patter at 1 month. With corticosteroid, the deposition of collagen type III and fibronectin was markedly reduced and the pachymetry of central cornea was closer to the expected value. CONCLUSION: This study suggests that corticosteroid help to minimize the postoperative myopic regression and corneal haze after PRK.     

Potential role of hepatocyte growth factor in the maintenance of renal structure: anti-apoptotic action of HGF on epithelial cells

BACKGROUND: Mesangial cells (MC) are known to secrete various vasoactive substances that may control endothelial and epithelial cell growth. Therefore, the cell-cell interactions among these cells may be important in the control of renal function. However, the exact mechanisms of maintaining the cell-cell interactions are not yet understood. We have focused on the role of hepatocyte growth factor (HGF) in the regulation of cell-cell interactions, since HGF has many protective functions in the kidney. To investigate the role of HGF in renal injury, we examined (1) the effects of HGF on epithelial injury induced by serum deprivation, and (2) the role of local HGF production in the maintenance of renal structure. METHODS: Apoptotic changes in epithelial cells were assessed by nuclear morphology and DNA fragmentation assay. Transfection of human HGF vector into epithelial cells was performed by a highly efficient viral-liposome method. The effects of secreted HGF on the growth of renal cells were examined using a co-culture system. RESULTS: The addition of recombinant HGF (rHGF) stimulated the growth of rat and porcine epithelial cells. Moreover, the decrease in number of epithelial cells by serum deprivation was significantly attenuated by rHGF. Interestingly, apoptotic changes in epithelial cells induced by serum deprivation were also significantly attenuated by rHGF (P < 0.01). As a model of gene therapy, the effects of overexpression of human HGF gene in epithelial cells on apoptosis induced by serum deprivation were examined. Transfection of human HGF vector into epithelial cells also attenuated epithelial cell death induced by serum deprivation through the inhibition of apoptosis, accompanied by increased HGF production (P < 0.01). In addition, HGF also prevented endothelial injury induced by tumor necrosis factor-alpha and dexamethasone. Given the presence of a local HGF system, we measured local HGF secreted from renal cells. Immunoreactive HGF was observed in the conditioned medium of MC, but not epithelial cells, while the specific receptor of HGF, c-met, was expressed in epithelial cells. Of importance, co-culture of MC with epithelial cells resulted in a significant increase in number of epithelial cells, which was significantly abolished by neutralizing anti-HGF antibody. CONCLUSIONS: Overall, these results demonstrate that local production of HGF in MC may maintain the growth of epithelial and endothelial cells through its anti-apoptotic action.     

Effects of transforming growth factor beta on corneal epithelial and stromal cell function in a rat wound healing model after excimer laser keratectomy

BACKGROUND: Transforming growth factor beta (TGF-beta) regulates extracellular matrix deposition, cell proliferation, and migration, and is expressed in cornea. TGF-beta is thought to be involved in the corneal wound healing process. METHODS: The central corneal area (3 mm in diameter) of Lewis rats was ablated using PTK mode excimer laser and the wound healing process was observed at 12 and 24 h and 2, 5, 10, and 30 days after treatment. The expression of TGF-beta 1, -beta 2 and -beta 3, TGF-beta type I and type II receptors, alpha 3, alpha 5, beta 4 integrin subunits, laminin and fibronectin was studied immunohistochemically. Antibody neutralizing TGF-beta 1, -beta 2 and -beta 3 was administered intraperitoneally, 50 micrograms daily, for 5 days after the laser treatment to investigate the effects of TGF-beta function blockade. RESULTS: At the leading edge of the regenerating epithelium, no TGF-beta type I and type II receptors and beta 4 integrin subunits were expressed after 24 h. Regenerating epithelium covered the ablated area after 2 days. An abnormal fibrotic layer was formed in the subepithelial area. This layer contained round-shaped cells in the stroma in the early stage (2-5 days after laser ablation) and spindle-shaped fibroblast-like keratocytes after 10 days. Laminin and fibronectin expression increased in the fibrotic layer. The increased stromal cells expressed TGF-beta isoforms and TGF-beta receptors. Neutralizing TGF-beta inhibited the stromal cell increase in the laser ablated area after 5 days. CONCLUSION: TGF-beta may be involved in epithelial cell migration and stromal cell reaction during the corneal wound healing process after excimer laser ablation in rat models.     

A prospective randomized trial of topical soluble 0.1% indomethacin versus 0.1% diclofenac versus placebo for the control of pain following excimer laser photorefractive keratectomy

BACKGROUND AND OBJECTIVE: To compare the safety and efficacy of topical nonsteroidal antiinflammatory drugs (NSAIDs) for the control of pain after excimer laser photorefractive keratectomy (PRK). PATIENTS AND METHODS: One hundred twenty informed patients were enrolled in a double-masked, randomized, comparative study and assigned to either 0.1% indomethacin, 0.1% diclofenac, or placebo treatment. Subjective postoperative pain, symptoms, re-epithelialization rate, and systemic medications were monitored for 2 days following photoablation. RESULTS: Compared with the placebo, 0.1% indomethacin solution significantly reduced pain on the day of surgery (D0) (P < .05), whereas 0.1% diclofenac did not reach a significant level (P = .46). At D0, analgesic intake by the oral route was significantly greater in the placebo group (P < .05). Severe photophobia was significantly less frequent in the group treated with 0.1% indomethacin (P < .05). Corneal wound healing was significantly delayed in the patients treated with 0.1% diclofenac at D2 as compared with other groups (P = .04). CONCLUSION: Topical 0.1% indomethacin solution helps control the pain induced by excimer laser photoablation of the cornea without any detrimental effect to the corneal epithelial wound healing.     

Temporal sequence of changes in tear film composition during sleep

Overnight eye closure induces a shift in the nature and composition of the tear film, from a dynamic reflex tear-rich to a stagnant secretory IgA-rich layer. This is accompanied by the induction of a state of sub-clinical inflammation, as evidenced by increases in albumin levels, plasminogen activation, conversion of complement C3 to C3c, and the recruitment of polymorphonuclear (PMN) cells into the tear film. To determine the time course and functional relationship between these potentially interdependent processes, tear samples were collected from ten non-contact lens wearers after 1, 2, 3 and 5 hours of sleep. A subgroup of 6 subjects also self-collected tear samples after 8 hours of sleep. Tear samples were analysed for albumin by quantitative immunofixation assay, secretory IgA (sIgA) by radial immunodiffusion assay, plasmin-like activity using a chromogenic substrate, and complement C3 to C3c conversion by immunoblot assay. Epithelial and PMN cells in the precorneal tear film were recovered from corneal washings from the same subjects after 1, 3, 5 and 8 hours of sleep, and quantified. Results revealed that, unlike epithelial cells which exhibited a slow progressive accumulation as a function of the period of sleep, PMN cell concentration exhibited a lag phase, with recruitment occurring after between 3 and 5 hours of eye closure. This was preceded by plasminogen activation, increases in albumin and sIgA levels, and complement C3 to C3c conversion, all of which occurred within 1 to 3 hours after eye closure. Plasmin-like activity appeared to plateau after 3 hours and then decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain folates and DNA methylation in rats fed a choline deficient diet or treated with low doses of methotrexate

Photorefractive keratectomy (PRK) with the ArF excimer lasers in current use usually approximates the intended corneal curvature by a mean of a delicate step-type pattern that is smooth off afterwards by reepithelialization and tear film. The present study was based on a model eye with axial myopia of -6 D but otherwise the optical and geometric properties of the Gullstrand model eye and was designed to investigate to what extent. (1) corneal step patterns can reduce retinal image contrast and (2) smoothing effects can restore such a loss. METHODS. The corneal surface resulting from PRK in the case of a myopia of -6 D (optical zone diameter 6 mm) is calculated for the parameters of the model eye. The retinal image contrasts of bar patterns are calculated by PSF (point spread function) analysis: varying size of pupil, wavelength, bar width, ablation step height and degree of smoothing. RESULTS. Step height influences retinal image contrast crucially. With step heights above 0.4 micron a massive loss of retinal image contrast must be expected, which can, however, be corrected to a useful extent by surface-smoothing effects. CONCLUSION. This study indicates that PRK with excimer lasers should be performed with low fluence and correspondingly low corneal step heights.     

HIV infection and isosporiasis. Presentation of a case

Tear lactoferrin concentration was measured by ELISA technique and followed in 30 patients undergoing cataract surgery. On the first day following surgery, there was a significant decrease in tear lactoferrin concentration followed by a gradual return to the initial values during the postoperative observation period of 7 days. There was an inverse linear relationship between tear lactoferrin concentration and the tear secretion rate measured by a modified Schirmer I test (1 min) suggesting a constant lactoferrin secretion by the tear glands. Since lactoferrin has known antibacterial and anti-inflammatory effects, the results may contribute to further understanding of the microbial vulnerability or resistance of the eye following surgical procedures.     

Advances in the management of bronchial asthma

The ultrastructure of rat precorneal tear film was visualized by the quick freezing-freeze substitution (QF-FS) method and the conventional fixative method under the scanning electron microscope (SEM). In the QF-FS method, the eyeballs of rats were quickly frozen with an isopentane-propane mixture cooled by liquid nitrogen applied directly to the eyes. After enucleating the eyes and fracturing the frozen corneas, the corneas were prepared for SEM observation. In contrast to the conventional fixative method, by which the microvilli of the surface epithelial cells could be visualized clearly, a very thin membrane-like structure was observed to cover the corneal surface in the eyes prepared by the QF-Fs method. Between the membrane-like structure and corneal surface, a homogeneous and fine network-like structure was observed. The results suggest that the structure of the tear film might be different from the one we have believed to consist of three layers until now. The QF-FS method is considered to be useful for the morphological study of the precorneal tear film.     

Hormonal treatment of breast cancer. Implications for quality of life, communication and improved therapy]

OBJECTIVE: The study was designed to improve the safety and predictability of radial keratotomy (RK). METHOD: Penetrating keratoplasty was performed on two eyes following RK for 2 months and 2 years respectively and their corneal buttons were studied histopathologically. RESULTS: The study revealed that at 2 months, there was only bridge-like healing of corneal epithelium, and oblique "V"-shaped, discontinuous or shallow incisions were seen, at 2 years, the healing process of partial incisions had not completed, and epithelial emboli were seen in the deep part of some incisions. CONCLUSION: Postoperatively, the incisions of RK are unstable for quite a long time. The RK incisions may influence other corneal surgeries performed on the same cornea in the future and are directly related to the healing and refractive outcome of RK. It is important to standardize the operative techniques.