[show abstract][hide abstract] ABSTRACT: It is well known that Tisseel Fibrin Sealant provides an excellent tissue adhesive. However, its thick and viscuous nature makes it nearly impossible to apply it in a uniform and thin layer. We propose applying the sealant phase as a dry powder and polymerizing it in-vivo by exposing it to thrombin solution after a graft has been placed.
For each experiment two rabbit corneal buttons were affixed to each other using either Tisseel or thrombin plus dry fibrinogen component, the tensile strength of the bond was then tested in the tension box. Balanced salt solution was used as an aqueous substitute.
Tisseel was demonstrated to create significant adhesive tensile force (expressed as N/m) between corneal buttons (P < 10). Using only the dry fibrinogen component followed by injection of the thrombin solution directly into the balanced salt solution did not significantly alter the strength of the bond (P = 0.18).
The use of the dry fibrinogen component followed by injection of thrombin solution into the balanced salt solution, without the accompanying fibrinolysis inhibitor, is equally effective in adhesive strength when compared to complete Tisseel. This technique may be used in lamellar corneal surgery, although there would be potential difficulties with its application in the in vivo setting.
[show abstract][hide abstract] ABSTRACT: Use the ID(50) (infectious dose to 50% of experimental animals) to quantify the most effective prophylactic dosing regimen to use with gatifloxacin 0.3% (Zymar) for the prevention of keratitis in a rabbit laser in situ keratomileusis model of Staphylococcus epidermidis infection.
University Laboratory, University of Arizona, Tucson, Arizona, USA.
Two groups of rabbits were compared in each of 2 experiments that were separated by 12 months. In the first experiment, rabbits receiving no postoperative antibiotic therapy (Group 1) were compared with rabbits receiving postoperative antibiotic therapy (Group 2). In the second experiment, postoperative antibiotic therapy (Group 3) was compared with preoperative and postoperative antibiotic therapy (Group 4). All antibiotic regimens used gatifloxacin 0.3%. Before antibiotic therapy began, corneal pockets were created in the right eye of each rabbit and all rabbits received balanced salt solution (BSS) only or BSS and S epidermidis inoculations in the corneal pocket. Rabbits were monitored for corneal infiltrates after surgery.
The ID(50) of the first, second, third, and fourth groups of rabbits was 10(2), 10(4), 10(5), and 10(7) organisms, respectively. The data showed a statistically significant difference between rabbits receiving BSS only and most rabbits receiving BSS plus inoculate at each postoperative measurement (P<.05).
The findings suggest that the use of both preoperative and postoperative antibiotic therapy may be most effective in preventing infection. Postoperative antibiotic therapy increased the number of S epidermidis necessary to cause infection by at least 100-fold over no antibiotic intervention. Preoperative plus postoperative antibiotic therapy increased the number of bacteria necessary to cause infection by at least 100-fold over postoperative therapy alone and by more than 10000-fold over no antibiotic intervention.
Journal of Cataract [?] Refractive Surgery 06/2007; 33(5):888-92. · 2.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: The femtosecond laser (Intralase) may provide advantages for dissecting a thin, uniform thickness posterior lamellar disk of donor tissue to be used for endothelial transplantation. We investigated the use of the Intralase to dissect the donor cornea from the posterior side to better obtain a thin and uniform lamellar disk. We investigated the use of a viscoelastic "cushion" to protect the endothelium during applanation and laser delivery.
Human eye bank donor buttons were placed endothelial side up, covered with a thin coat of viscoelastic, and brought into contact with the Intralase applanation lens. A 7-mm diameter, 100-microm lamellar disk was cut from the endothelial side. The endothelial viability after these procedures was determined using a live cell/dead cell assay. Controls were designed to assess the endothelial viability after applanation and laser application using only a balanced salt solution (BSS) cushion instead of viscoelastic material. Additionally, applanation without lasering using either BSS or a viscoelastic cushion was studied.
The average endothelial cell loss in the laser experiment sets were 10% (n = 5, range of 4-17%, Sodium Hyaluronate), 14% (n = 5, range of 7-19%, Sodium Hyaluronate-Sodium Chondroitin) and 6% (n = 5, range of 3-11%, Hydroxypropylmethyl-cellulose). In the controls, laser and applanation with BSS resulted in an average endothelial loss of 18% (n = 5, range of 14-26%). Applanation alone without laser dissection resulted in cell loss of 9% (n = 5, range of 7-12%) using BSS and 9% (n = 6, range 1-42%) Hydroxypropylmethyl-cellulose.
The technique of using a viscoelastic "cushion" to protect endothelial cells from damage during posterior laser dissection prior to transplantation is promising. Viscoelastic coating protects the endothelial layer from damage from the coupling lens better than a layer of BSS. The lasering process, however, causes damage in addition to applanation with the laser lens. Further studies are warranted to optimize reproducibility of endothelial cell survival and evaluate the smoothness of stromal dissections in the posterior cornea.
[show abstract][hide abstract] ABSTRACT: To investigate the efficacy of the fourth-generation fluoroquinolone, gatifloxacin 0.3%, compared to ciprofloxacin 0.3%, in preventing Streptococcus pneumoniae keratitis in a rabbit laser in situ keratomileusis (LASIK) model.
Twelve albino rabbits had bilateral lamellar flaps created. Group A (eight eyes) was given gatifloxacin 0.3%; group B (eight eyes) was given ciprofloxacin 0.3%; and group C (eight eyes) served as the controls. Groups A and B received one drop of antibiotic 20 minutes before the creation of the lamellar flap, at the conclusion of flap formation, and four times per day for 3 days. All corneas were inoculated with 0.1 mL of 4 x 10 organisms/mL of S. pneumoniae immediately after flap formation. On day 3, all corneas were examined and cultured.
Group A (gatifloxacin) had no infiltrates and three areas of 1-mm central corneal haze. On day 3, one of eight corneas had a positive culture. Group B (ciprofloxacin) had seven infiltrates, including one perforation, and six of eight corneas had positive cultures. Group C (control) had eight corneal infiltrates, and all eight corneas had positive cultures. The data show a statistically significant difference between gatifloxacin and ciprofloxacin and gatifloxacin and control for mean infiltrate size and mean culture scores.
The fourth-generation fluoroquinolone, topical gatifloxacin 0.3%, is superior to topical ciprofloxacin 0.3% for prophylaxis against a clinical isolate of S. pneumoniae in a rabbit LASIK model.
[show abstract][hide abstract] ABSTRACT: To investigate the aqueous penetration of 3 commercially available ophthalmic fluoroquinolones.
Prospective, double-masked, clinical study.
Fifty-two eyes of 52 patients.
Fifty-two patients undergoing cataract surgery were given preoperative topical gatifloxacin 0.3% (Zymar), moxifloxacin 0.5% (Vigamox), or ciprofloxacin 0.3% (Ciloxan). The patients were instructed to use their antibiotic drops 4 times a day for 3 days before surgery. On the day of surgery, patients were given their assigned antibiotic every 15 minutes for 3 doses, 1 hour before their procedure. At the time of surgery, 0.1 ml of aqueous fluid was aspirated from the anterior chamber with an air cannula needle attached to a tuberculin syringe. The aspirate was immediately stored at -70 degrees C.
Fluoroquinolone concentrations were determined by reverse-phase high-pressure liquid chromatography assay technique with ultraviolet detection at a wavelength of 275 nm.
Mean aqueous concentration of gatifloxacin in 16 eyes was 0.63 microg/ml (standard deviation [SD], 0.30), moxifloxacin in 14 eyes was 1.31 microg/ml (SD, 0.46), and the mean concentration of ciprofloxacin in 22 eyes was 0.15 microg/ml (SD, 0.11).
Both moxifloxacin (P<0.001) and gatifloxacin (P<0.005) penetrated the aqueous humor at significantly higher levels than ciprofloxacin. Moxifloxacin penetrated into the aqueous humor at significantly higher levels than gatifloxacin (P<0.05). The anterior chamber levels of moxifloxacin and gatifloxacin may be due to the difference in antibiotic concentration.
[show abstract][hide abstract] ABSTRACT: To evaluate the aqueous penetration of the fourth-generation fluoroquinolones moxifloxacin and gatifloxacin.
University of Arizona, Tucson, Arizona, USA.
Forty eyes of 20 New Zealand white rabbits were divided into 2 experimental groups. In Experiment I rabbits (20 eyes), a commercial preparation of topical gatifloxacin 0.3% was administered to 9 eyes and moxifloxacin 0.5% to 9 eyes; 2 eyes served as a control. Eyes were dosed according to a keratitis protocol; ie, every 15 minutes for 4 hours. The aqueous humor was sampled 10 minutes after the last dose. Experiment II rabbits (20 eyes) were dosed according to a cataract prophylaxis protocol; ie, 4 times a day for 10 days. The aqueous humor was sampled 1 hour after the last dose of antibiotic in 12 eyes and 24 hours after the last dose in 8 eyes. High-performance liquid chromatography was used to determine the fluoroquinolone concentration.
In the keratitis dosing protocol, the mean concentration of moxifloxacin in the aqueous (n=9) was 11.057 microg/mL (range 7.66 to 18.87 microg/mL), which was significantly higher than the mean concentration of gatifloxacin (n=8) (7.570 microg/mL [range 4.75 to 10.86 microg/mL]) (P=.030). In the cataract prophylaxis dosing protocol, the mean aqueous concentration of moxifloxacin (n=6) was 1.745 microg/mL (range 0.92 to 3.87 mg/mL). The mean concentration of gatifloxacin (n=6) was 1.207 microg/mL (range 0.44 to 2.44 microg/mL). The difference was not statistically significant (P=.359).
Higher mean levels (x1.46) of aqueous penetration were achieved with moxifloxacin than with gatifloxacin in the keratitis-dosing model. There was no statistically significant difference between the 2 drugs in the cataract prophylaxis dosing model. Both antibiotics had aqueous levels in excess of the minimum inhibitory concentration for most pathogenic organisms in both models.
Journal of Cataract [?] Refractive Surgery 11/2004; 30(10):2177-82. · 2.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aqueous penetration of the commercial preparations of the fluoroquinolone antibiotics ofloxacin, ciprofloxacin, levofloxacin, and gatifloxacin were compared following topical dosing in a rabbit model. Levofloxacin achieved the highest aqueous concentrations, with a mean aqueous level of 4.8014 microcg/mL (p = 0.002, p = 0.00002, p = 0.015.) Ofloxacin (2.5136 microcg/mL) and gatifloxacin (2.4817 microcg/mL) achieved statistically equal aqueous concentrations (p = 0.479). Ciprofloxacin reached the lowest levels in the aqueous humor (0.9616 microcg/mL, p = 0.00002, 0.00004, 0.008). Gatifloxacin alone achieved concentrations in excess of the MIC90s of gram-positive pathogens of concern.
Journal of Ocular Pharmacology and Therapeutics 07/2004; 20(3):210-6. · 1.29 Impact Factor
[show abstract][hide abstract] ABSTRACT: To describe the causes of blindness and visual impairment in a population-based sample of Hispanics.
A cross-sectional study.
A random sample of 4774 Hispanic residents of Santa Cruz and Pima Counties in Southern Arizona aged 40 years and older who participated in Proyecto VER (Vision Evaluation and Research).
Subjects were interviewed and underwent a thorough ophthalmic examination. Presenting and best-corrected visual acuity was determined using the Early Treatment of Diabetic Retinopathy Study protocol, followed by a standardized ophthalmic examination to determine the causes of visual loss. Anterior and posterior segment specialists in ophthalmology confirmed the causes.
Causes of visual loss (best-corrected acuity worse than 20/40).
The response rate of eligible participants was more than 70%. Best-corrected acuity in the better seeing eye worse than 20/40 increased from 0.3% in those aged 40 to 49 to 5.6% in those aged 65 and older. The leading cause was cataract, accounting for 42% of all visual loss, followed by age-related macular degeneration (15%), and diabetic retinopathy (13%). Among 14 people who were bilaterally blind, open-angle glaucoma was the leading cause. Women had higher age-adjusted prevalence of severe cataract compared with men and were more likely to be visually impaired from cataract, diabetic retinopathy, and open-angle glaucoma, although gender differences were not statistically significant.
Causes of visual impairment differ from those reported in Caucasian populations, with open-angle glaucoma being the leading cause of blindness. Further work on gender-based obstacles to eye care in the Hispanic community may be warranted.
[show abstract][hide abstract] ABSTRACT: We postulated that ablation of trabecular meshwork can be accomplished
without damage to Schlemm's canal and adjacent tissue. We performed
Erbium:YAG laser trabecular ablation on human autopsy eyes and confirmed
the results by histopathologic examination. We used an Erbium:YAG laser
(2.94 micrometers ) equipped with a sapphire probe and a quartz tip (350
micrometers diameter). Energy levels of 5, 10, 15, 20, and 40 mJ per
pulse were used. The probe was placed directly onto the trabecular
meshwork viewed through an operating microscope and focal ablation was
performed with single pulses. The tissue was then processed and examined
under light and scanning microscopy. The histopathologic study of the
trabecular meshwork revealed that a single pulse at an energy level of
15 mJ was optimal for ablating through the trabecular meshwork to
Schlemm's canal with a minimal amount of coagulative damage to the
surrounding tissue. The mean width of ablated tissue was 150 micrometers
+/- 29 micrometers (n equals 18) and the mean depth of ablation was 133
+/- 48 micrometers (n equals 18) at this energy level. The mean width of
coagulative damage to adjacent tissue was 16 +/- 8 micrometers (n equals
18). The ablation and coagulative damage increased with increasing
energy levels. The Erbium:YAG laser equipped with a contact probe
effectively ablates trabecular meshwork with little surrounding
coagulative damage. This feature may minimize scarring and result in a
high long-term patency rate of outflow channels created by laser
[show abstract][hide abstract] ABSTRACT: A pulsed erbium:YAG laser equipped with a 1-m zirconium fluoride fiber coupled with a sapphire tip was used to photovaporize human autopsy lens tissue. Measured diameter of photovaporization of human lens cortex with erbium:YAG laser ranged from 117 micrometers at a fluence of 3.98 J/cm2 to 227 micrometers at fluence of 15.92 J/cm2. Measured diameter of photovaporization of human lens nucleus with Erbium:YAG laser ranged from 265 micrometers at a fluence of 11 J/cm2 and 295 micrometers at a fluence of 15 J/cm2. Endolenticular phacovaporization with the Erbium:YAG laser appears to be a potentially efficient and precise means of removing the human lens.
[show abstract][hide abstract] ABSTRACT: Mid-IR lasers that operate near the absorption peak of water have a short penetration depth in ocular tissues. Ablation of tissue can be accomplished with minimal coagulative damage to underlying structures. We used an erbium:YAG laser equipped with a contact probe to create retinotomy sites in the human retina of eye bank eyes. An erbium:YAG laser (2.94 micrometers ) equipped with an infrared transmitting glass fiber and a sapphire tip (400 micrometers ) was used to directly ablate the surface of the retina. We administered both single and multiple pulses to the macula and peripheral retina using energy levels from 4 to 16 mJ per pulse. The retinas were then examined histopathologically to evaluate the extent of ablation and coagulative damage. Single pulses at low energy levels were noted to cause ablative damage to the nerve fiber layer and ganglion cell layer without a notable coagulative effect. The mean ablation depth at lower energy levels was less than the mean ablation depth at higher energy levels. Extensive laser application produced disruption of the retinal pigment epithelium, choroid and sclera. the erbium:YAG laser equipped with a contact probe is an effective means of creating retinotomies in human autopsy eyes. When used in the single pulse mode at lower energy levels, the erbium:YAG laser appears capable of removing superficial retinal layers without damaging deeper structures.
[show abstract][hide abstract] ABSTRACT: In this paper, we present our findings of the effect of the Erbium:YAG laser on cornea, trabecular meshwork, and retinal tissue. We believe the laser is a safe and effective cutting tool with tremendous potential for surgical application.
[show abstract][hide abstract] ABSTRACT: To examine the effects of laser in situ keratomileusis (LASIK) flap incision and healing on the shape of the cornea and the wavefront error of the eye.
Four weeks prior to bilateral LASIK, study subjects had a flap cut using a keratome in one eye. The fellow eye remained untouched as a control. Corneal topography and wavefront errors were measured at 1 day, 1, and 4 weeks after the flap was created. After 4 weeks, the flap was lifted and LASIK was performed. The control eye also had LASIK at this time.
Differences in corneal shape and wavefront error consistent with a mild hyperopic shift were seen as a result of the keratome incision.
Cutting the flap in LASIK causes subtle changes to corneal shape and the optics of the eye that may affect customized treatments. Additional work is needed to quantify these changes so that their effect can be incorporated into future treatments.
Journal of refractive surgery (Thorofare, N.J.: 1995) 18(5):S584-8. · 2.47 Impact Factor