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Biomedical subjects

C Aras

Publications and source records attributed to C Aras.

31 records · Page 2Linked to original sources
PubMed1994

Polysulfone capillary fiber for intraocular drug delivery: in vitro and in vivo evaluations.

Studies were conducted to investigate the usefulness of polysulfone capillary fiber (PCF) as a drug delivery device for intraocular applications. Carboxyfluorescein (CF) was used as a model drug to prepare PCF-dye devices for both in vitro and in vivo kinetic studies. For the in vitro study, PCF-CF devices were incubated in 0.1 M phosphate buffer, pH 7.4 at 37 degrees C, and CF release was quantified at various times up to 5 weeks. In vitro results indicated a bi-phasic, sustained-release profile of CF from the PCF device for over 30 days. PCF-CF devices released 5% and 10% of their initial CF contents by the first and second day following incubation, respectively. By 10 days after incubation, approximately 50% of the dye content was released from the PCF-CF devices. The rate of dye release decreased thereafter, such that 65% and 90% of CF was released by 17 and 28 days after incubation, respectively. In a subsequent study, the in vivo kinetics of the PCF-CF device were determined in the rabbit eye. PCF-dye devices were prepared with the following CF formulations: 1) microsphere-incorporated CF; 2) lyophilized liposome-encapsulated CF; or 3) micronized CF powder. A PCF-dye device was implanted in the vitreous cavity, and fluorophotometry from the retina to the anterior chamber was performed at various times up to 45 days to quantify fluorescein level. At the conclusion of the study, eyes were enucleated and examined for histopathology. The time-course study showed fluorescein level for up to 45 days in the vitreous. The midvitreous concentration-time profile indicated a CF t1/2 of 10 and 30 days for the PCF-CF powder and PCF-CF liposome preparation, respectively. In contrast, the PCF device prepared with microsphere-incorporated CF showed fluorescein level with a t1/2 of less than one week in the vitreous. Histological examination of the eyes implanted with PCF or PCF-dye device showed no sign of ocular toxicity. Collectively, these results indicated that the PCF device is biocompatible and may be useful for the extended release of drugs in the posterior segment of the eye.

Analysis of Variance↗
PubMed1994

Calcein fluorophotometry in streptozocin-induced diabetic rats.

Calcein was used in vitreous fluorophotometry (VF) to study the blood-retinal barrier (BRB) in rats with streptozocin-induced diabetes. Calcein was injected intravenously in 18 diabetic rats and sodium fluorescein (NaF) in 12 diabetic rats. VF was performed at 1, 2, 4, 6, 9, and 21 hours following the single injection in these diabetic rats; it was also performed at these times in 24 normal (control) rats. On another day, the same experiment was performed using NaF. There was no significant difference between the two dyes in the diabetic and nondiabetic rats at 1 hour. However, at 4 hours and at later measurement points, there was dye leakage into the vitreous, peaking at 9 hours; the leakage was significantly greater in the diabetic rats. Also, the leakage was significantly greater with calcein than it was with NaF. The data demonstrate that calcein circulates longer and at higher levels than NaF and thus is probably more useful for BRB integrity studies.

Animals↗
PubMedDate not supplied

Flap complications in our learning curve of laser in situ keratomileusis using the Hansatome microkeratome.

PURPOSE: To determine the incidence and the type of flap complications in our initial series of eyes undergoing laser in situ keratomileusis and the impact of microkeratome-related complications on best spectacle-corrected visual acuity. METHODS: We reviewed the charts of the 630 consecutive eyes operated in the Refractive Surgery Department of Cerrahpasa Medical School, University of Istanbul, Turkey using the Hansatome microkeratome and the Summit, SVS Apex Plus excimer laser between March 1998 and November 1999. The mean follow-up was 12.6 months. RESULTS: The incidence of total flap complications was 19.8%. Flap folds (5%) were the most common complication. The incidence of epithelial ingrowth was 3.3%. Diffuse lamellar keratitis was encountered in 20 cases (3.17%). Displaced flaps were seen shortly after the procedure in 8 eyes (1.26%) and repositioned immediately. Improper keratectomy occurred in 14 eyes (2.2%) and incomplete keratectomy in four procedures (0.63%). The presence of interface debris and hemorrhage was each 1.9%. We observed one interface abscess, which was culture-negative and cured with fortified antibiotics, and one free flap. CONCLUSIONS: Although the LASIK procedure with the Hansatome had an easy learning curve without any of the serious complications that frequently occur in this phase, we still observed flap related complications that affected visual outcome.

Adult↗
PubMedDate not supplied

In vitro effect of silicone oil and liquid perfluorocarbons on platelet aggregation.

PURPOSE: To study the in vitro effect of silicone oil of different viscosities and liquid perfluorocarbons on platelet aggregation. METHODS: Silicone oil with a viscosity of 5700 cs and 1000 cs and liquid perfluorocarbons of perfluoroperhydrophenantren and perfluorodecaline were studied to investigate the effect of these agents on platelet aggregation under in vitro conditions. The experiments were performed by using platelet rich plasma with an aggregometer. Aggregation was induced with three different agonists, including 5"-adenosine diphosphate (ADP), epinephrine (EPI), and collagen (Col). The results were obtained as a percentage of maximal aggregation and compared with controls using Kruskal-Wallis one way analysis of variance test. RESULTS: The tests with ADP as aggregating agent revealed that the percentage of maximal aggregation was a mean of 72.66+/-3.51% for ADP only, 58.66+/-3.05% for silicone oil of 1000 cs, 62.66+/-2.08% for silicone oil of 5700 cs, 56.00+/-7.00% for perfluoroperhydrophenantren, and 52.3+/-3.1 % for perfluorodecaline. With EPI, aggregation was induced in all control samples with a mean of 76+/-9.54%. The mean percentage of maximal aggregation was 66.7+/-3.06 for silicone oil of 1000 cs, 72.33+/-5.5% for silicone oil of 5700 cs, 71.67+/-3.79% for perfluoroperhydrophenantren, and 70.33+/-2.52% for perfluorodecaline. With collagen, it was 86.67+/-1.53% for controls, 83.67+/-3.51% for silicone oil of 1000 cs, 85.33+/-4.51% for silicone oil of 5700 cs, 83.33+/-4.93% for perfluoroperhydrophenantren, and 81.33+/-4.16% for perfluorodecaline. Statistical analysis revealed no significant change in the percentage of maximal aggregation for all tested substances in the experiments. CONCLUSIONS: Silicone oil of different viscosities and perfluoroperhydrophenantren and perfluorodecaline have minimal antiaggregating effect on platelets. The level of effect is not statistically significant.

Adenosine Diphosphate↗
PubMedDate not supplied

Comparison of the effect of Healon, Healon GV, Healon 5, Viscoat, and Ocucoat on platelet aggregation under in vitro conditions.

PURPOSE: To study the effect of Healon, Healon GV, Healon 5, Viscoat, and OcuCoat on platelet aggregation under in vitro conditions. METHODS: Ocular viscoelastic devices including Healon, Healon GV, Healon 5, Viscoat, and OcuCoat were studied to investigate the effect of these agents on platelet aggregation under in vitro conditions. The experiments were performed by using platelet-rich plasma with an aggregometer. Aggregation was induced with three different agonists including 5''-adeno-sinediphosphate (ADP), epinephrine (EPI), and collagen (Col ). The results were obtained as a percentage of maximal aggregation and compared with controls using one-way analysis of variance (ANOVA) test. RESULTS: The tests with ADP as aggregating agent revealed that the percentages of maximal aggregation were a mean of 75 +/- 4.35% for ADP only, 67 +/- 4.35% for Healon, 59.33 +/- 3.51% for Healon GV, 70 +/- 3% for Healon 5, 58 +/- 3.46% for Viscoat, and 64 +/- 2% for OcuCoat. Kruskal-Wallis one-way ANOVA test revealed no significant decrease in the percentage of maximal aggregation for all tested substances. With EPI, aggregation was induced in all control samples with a mean of 80.66 +/- 2.08%. The mean percentage of maximal aggregation was 67 +/- 3% for Healon, 77.66 +/- 4.04% for Healon GV, 77 +/- 4% for Healon 5, 80.6 +/- 4.04% for Viscoat, and 65 +/- 5% for OcuCoat. Statistical analysis showed no significant difference. With collagen, maximum aggregation was 74 +/- 5.29% for controls, 65 +/- 4.35% for Healon, 54 +/- 2% for Healon GV, 51 +/- 2.64% for Healon 5, 59 +/- 2% for Viscoat, and 72.66 +/- 1.52% for OcuCoat. Kruskal -Wallis one-way ANOVA test revealed no significant change in the percentage of maximal aggregation for all tested substances in the experiments. CONCLUSIONS: Ophthalmic viscosurgical devices like Healon, Healon GV, Healon 5, and Viscoat that contain glycosaminoglycans and OcuCoat that contains hydroxypropyl methylcellulose have inhibitory effects on platelet aggregation but the effect is not statistically significant and there is no difference among the ocular viscoelastic devices in regard to inhibitory effect on platelet aggregation.

Adenosine Diphosphate↗
PubMedDate not supplied

Thermoablation treatment for trichiasis in trachoma using the semiconductor diode pumped laser.

PURPOSE: The aim of this prospective study was to verify the efficacy of laser therapy for trichiasis in trachoma. Trichiasis is one of the most important complications of trachoma which is endemic in Sanliurfa, a city in the southeast of Turkey. METHODS: Twenty-eight eyelids of 22 patients - 15 males and 7 females - with trichiasis related to trachoma involving the upper, lower, or both lids, were included in the study and treated with a semiconductor diode-pumped, frequency-doubled, solid-state laser operating true CW at 532 nm. RESULTS: 19 (67.9%) of the lids were successfully treated in two sessions or less. Six lids (21.4%) required a third laser session and three (10.7%) a fourth session. Mild notching or dimpling occurred in two eyelids (5.6%). Postoperative swelling was minimal or absent. CONCLUSIONS: The results show that laser treatment may be successful for trichiasis caused by trachoma. Laser thermoablation is an effective and safe method, with many advantages over other modalities.

Aged↗
PubMedDate not supplied

Photorefractive keratectomy for hyperopia and aphakia with a scanning spot excimer laser.

OBJECTIVE: To study the safety, efficacy, predictability, and stability of photorefractive keratectomy (PRK) for hyperopia and aphakia. METHODS: Fifteen eyes of 15 patients (mean age, 33 +/- 5.95 yrs) were enrolled in the study and divided into three groups. The first group was comprised of six eyes that had hyperopia ranging from +1.75 to +4.75 D; the second group had seven hyperopic eyes ranging from +5.00 to +9.75 D; the third group included two eyes of two aphakic patients. All eyes had PRK with a 193 nm argon fluoride excimer laser (Chiron-Technolas, Keracor 116) with a 10 Hz repetition rate and a fluence of 120 mJ/cm2. The total follow-up time in all eyes was 12 months. RESULTS: In the lower hyperopia group, 0% eyes were within +/- 0.50 D and 66% (N = 4) of eyes were within +/- 1.00 D of emmetropia with the other two eyes between +1.00 and +2.00 D at 1 year after PRK. In the higher hyperopia group, all eyes had at least +3.00 D of hyperopia at 1 year. In the aphakic group, both eyes achieved less than 50% of the target correction of +10.00 D at 1 year. Final uncorrected visual acuity ranged from 20/20 to 20/30 in the lower hyperopia group, 20/30 to 20/50 in the higher hyperopia group, and count fingers in the aphakic group. CONCLUSIONS: PRK is a relatively safe, stable, and effective procedure with reasonably good predictability for eyes with less than +5.00 D of baseline hyperopia, and poor predictability for eyes with more than +5.00 D of baseline hyperopia. PRK is ineffective in the correction of aphakia.

Adult↗
PubMedDate not supplied

Decreased tear secretion after laser in situ keratomileusis for high myopia.

PURPOSE: To investigate the changes in tear secretion and tear film stability after excimer laser in situ keratomileusis (LASIK) for high myopia. METHODS: One eye of 28 patients underwent unilateral LASIK for the correction of myopia with spherical equivalent refractions ranging from -6.37 to -18.25 D (mean, -11.98 +/- 3.45 D). Schirmer tear test values without anesthesia at 5 minutes and tear break-up time values were measured 4 weeks after LASIK. Unoperated contralateral eyes were used as a control for each patient. The Schirmer tear test and tear break-up time values were analyzed statistically using the independent t-test. RESULTS: The mean Schirmer tear test value was 16.17 +/- 2.50 mm in the operated eyes and 21.07 +/- 7.03 mm in the unoperated (control) eyes of the same patients (P = .001). The mean tear break-up time value was 21.0 +/- 3.55 seconds in the operated eyes and 21.27 +/- 6.79 seconds in the control eyes (P = .85). CONCLUSION: Tear secretion decreased following LASIK probably due to decrease in corneal sensitivity, but tear film stability appeared unaltered.

Adult↗
PubMedDate not supplied

Retinal detachment following laser in situ keratomileusis.

OBJECTIVE: To report the clinical characteristics, surgical management and outcome of retinal detachment following laser in situ keratomileusis (LASIK) in myopic patients. PATIENTS AND METHODS: Retrospective review of 10 eyes of 10 myopic patients with retinal detachment who had previously undergone LASIK surgery were analyzed. Included in the study were 7 males and 3 females, aged 22 to 68 years (35.2+/-2.8). RESULTS: Mean spherical equivalent refraction was -10.51+/-3.90 D (ranging from -6.37 D to -17.00 D) before surgery. The time interval between the LASIK procedure and the development of retinal detachment varied from two months to nine months (5.2 +/- 2.78 months). The number of retinal breaks was one in 7 patients, two in 2 patients and three in 1 patient. The type of retinal breaks included 7 patients with horse shoe tears, 1 patient with a retinal hole, 1 patient with a giant retinal tear, and 1 patient with retinal dialysis. Retinal breaks were located anterior to the equator in 9 patients and posterior to the equator in 1 patient. Retinal reattachment was achieved with one operation in 8 eyes (80%) and the remaining 2 eyes required a second surgery for the reattachment of the retina. CONCLUSION: This study suggests the possible association between retinal detachment and LASIK procedure in patients with myopia. Clinicians should be aware of retinal pathology predisposing to retinal detachment in patients undergoing LASIK.

Adult↗
PubMedDate not supplied

Suprachoroidal hemorrhage during silicone oil removal in Marfan syndrome.

A 30-year-old male with Marfan syndrome underwent pars plana lensectomy and vitrectomy combined with silicone oil injection for the treatment of retinal detachment with proliferative vitreoretinopathy (PVR). Four months after vitrectomy, the silicone oil was removed using an anterior chamber maintainer (AC) and a self-sealing clear corneal incision at the upper temporal quadrant. Suprachoroidal hemorrhage (SCH) developed at the end of the operation. It was limited to the nasal side of the retina. Suprachoroidal hemorrhage remained to be limited and did not show progression.

Adult↗
PubMedDate not supplied

Ocular penetration of cefepime following systemic administration in humans.

OBJECTIVE: To investigate the penetration of cefepime (a fourth generation cephalosporin) into the aqueous humor after single-dose intravenous administration in humans. PATIENTS AND METHODS: Before receiving cataract surgery, 30 patients received randomly 1 g (group 1, 15 patients) and 2 g (group 2, 15 patients) single intravenous injection of cefepime before surgery. Samples of aqueous humor and serum were obtained at 0.5, 1, 2, 4, and 12 hours after injection. Three patients were sampled each time for 1 g and 2 g of cefepime. Samples were assayed for cefepime concentrations with high performance liquid chromatography (HPLC). RESULTS: All the patients had detectable cefepime in their aqueous humor and serum measurable by HPLC. A mean peak aqueous humor level was 5.16 +/- 0.88 microg/mL in group 1 and 5.87 +/- 1.64 microg/mL in group 2 at 0.5 hour after injection. The mean level of cefepime in aqueous humor decreased after 0.5-hour measurements in both groups and was measured as 0.82 +/- 0.21 microg/mL in group 1 and 2.04 +/- 0.30 microg/mL in group 2 at 12 hours after injection. CONCLUSION: Aqueous humor levels of cefepime after single IV injection were above the minimum inhibitory concentration (MIC90) for most ocular pathogens, but the duration of exposure to an antibiotic was not sufficient for therapeutic effect.

Absorption↗
PubMedDate not supplied

Scleral tunnel for the implantation of glaucoma seton devices.

The technique described in this paper shows how to use a long scleral tunnel for the implantation of anterior tube parts of glaucoma drainage devices. It involves the creation of a scleral tunnel beginning 10 mm behind the limbus and extending to the anterior chamber. Anterior tube parts of Krupin eye valve with disk is inserted through the scleral tunnel to the anterior chamber. The disk part is secured to the episclera as used in the standard technique. We have used this technique in 6 eyes of 6 consecutive patients with refractory glaucoma. The placement of anterior tubes as part of glaucoma seton devices was done in all patients. While mean intraocular pressure (IOP) was 39.3 +/- 4.9 mm Hg (ranged from 29 to 56 mm Hg) preoperatively, it was 16.6 +/- 5.3 mm Hg (ranging from 11 to 25 mm Hg) at the end of follow up. Mean follow-up time was 7.16 +/- 1.16 months (ranging from 6 to 9 months). After surgery, conjunctival erosion or displacement of the anterior tube and dellen formation were not found in any eyes. The use of a long scleral tunnel for the implantation of anterior tube parts of glaucoma seton devices offers some advantages over standard implantation techniques.

Female↗