Murat Karacorlu

In vitro antimicrobial activity of silicone oil against endophthalmitis-causing agents.

PURPOSE To investigate the antimicrobial activity of silicone oil against endophthalmitis-causing agents in vitro. METHODS The antimicrobial activity of silicone oil was tested on Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus spp. The bacteria and fungi were separately inoculated into 1,300 centistokes silicone oil. Control inoculations were done in two different media: physiologic saline and brain-heart infusion (BHI) for bacteria and Sabouraud broth and physiologic saline for fungi. From each medium, 0.001-mL samples were taken and plated in Petri dishes. After overnight incubation, colony-forming units (CFUs) were enumerated. Culturing from the initially prepared specimens, incubating overnight, and counting CFUs was repeated until no growth of microorganisms was seen in the silicone oil-containing media. Macroscopic photography of the colonies and light microscopic photography of microorganisms were performed. RESULTS All the microorganisms showed an apparent decrease in CFUs, with elimination between 7 and 21 days in silicone oil. Colony-forming units of microorganisms remained stable in physiologic saline during the study, with the exception of gradual decrease in CFUs of S. aureus and S. epidermidis from the beginning of the third day. In BHI and Sabouraud broth, both bacteria and fungi showed a growth pattern that was compatible with the growth curve of microorganisms. CONCLUSION Silicone oil has an antimicrobial activity against S. aureus, S. epidermidis, P. aeruginosa, C. albicans, and Aspergillus spp., which are common endophthalmitis-causing agents.

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.

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.

CHANGES IN TEAR FLOW AND TEAR FILM STABILITY AFTER PHOTOREFRACTIVE KERATECTOMY

PURPOSE To investigate the changes in tear flow and tear film stability after photorefractive keratectomy (PRK) for myopia. MATERIAL AND METHOD One eye of 32 patients underwent unilateral PRK procedure for the correction of myopia ranging from -1.50 to -6.00 diopters (D) (mean -3.65 +/- 1.55 D). Schirmer test values and break-up time (BUT) scores were measured 6 weeks after the PRK procedure. Unoperated, contralateral eyes were used as control eyes for each patient. The Schirmer test scores and BUT values were statistically analyzed using independent t test. RESULTS The mean Schirmer test value was 14.45 +/- 7.79 mm in the operated eyes. It was 28.83 +/- 5.89 in the control eyes. The decrease in Schirmer test value was statistically significant (t = 8.28, p = 0.0001). The mean BUT scores were 13.19 +/- 5.09 s in the operated eyes and 27.83 +/- 9.31 s in the control eyes. The decrease was statistically significant (t = 7.86, p = 0.0001). CONCLUSION PRK causes a decrease in tear flow and tear film stability that is probably caused by decreased corneal sensation after PRK.

Corneal iron ring after hyperopic laser-assisted in situ keratomileusis.

PURPOSE To report a new corneal iron ring after hyperopic laser-assisted in situ keratomileusis (LASIK). METHODS Three patients underwent hyperopic LASIK for the correction of hyperopia in both eyes. Spherical equivalent refraction of the patients ranged from +3.37 to +6.50 diopters. LASIK procedure was performed using automated corneal shaper and 193-nm argon fluoride excimer laser. RESULTS Both eyes of the patients were noted to have a corneal iron ring located at the paracentral area at 6-7 months after surgery. The localization of iron ring corresponded with outside border of central steep zone. Twelve-month examination showed there was no change in color, shape, and density of corneal iron ring. CONCLUSIONS Corneal topographic changes induced by hyperopic LASIK may cause corneal iron ring to develop.

Intravitreal Penetration of Cefepime after Systemic Administration to Humans

Purpose: To investigate the penetration of cefepime (a fourth-generation cephalosporin) into the vitreous after single-dose intravenous administration to human subjects. Methods: Thirty phakic patients about to undergo vitreous surgery received 1 g (group 1, 15 patients) or 2 g cefepime (group 2, 15 patients) in a single intravenous injection before surgery. The indications for vitreous surgery were retinal detachment with proliferative vitreoretinopathy (24 patients), retinal detachment associated with giant retinal tear (4 patients), macular hole (1 patient) and intraocular foreign body (1 patient). Samples of vitreous and serum were obtained at 0.5, 1, 2, 4 and 12 h after injection. Three patients were used for each sampling time and 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 vitreous and serum measurable by HPLC. The level of cefepime in the vitreous peaked at 2 h and reached a minimum at 12 h after intravenous injection in both groups. A mean peak vitreous level of cefepime was 1.91 ± 0.13 µg/ml in group 1 and 2.86 ± 0.37 µg/ml in group 2. The level of cefepime in the vitreous at 12 h after injection was 0.89 ± 0.14 µg/ml in group 1 and 0.97 ± 0.30 µg/ml in group 2. Conclusion: The vitreous level of cefepime after intravenous injection was below the minimum inhibitory concentration (MIC90) against Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa, but was over the MIC90 against Proteus mirabilis, Klebsiella spp., Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes and Enterobacter spp.

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.

Failure to Detect Hepatitis B Virus in Vitreous by Polymerase Chain Reaction

Purpose: To assay the vitreous of asymptomatic hepatitis B virus (HBV) carriers for the presence of HBV DNA using polymerase chain reaction (PCR). Methods: Vitreous and serum specimens were collected from 13 carriers of HBV. The presence of HBV DNA was investigated by using PCR and Digene’s Hybrid Capture System. The presence of hepatitis B surface antigen (HBsAg) in vitreous was also investigated by using the enzyme immunoassay (EIA). Results: The serum was positive for HBV DNA in3 of the 13 asymptomatic carriers using PCR. Vitreous samples of all the patients, including 3 patients who were positive for HBV DNA in serum, were negative for HBV DNA with PCR and were negative for HBsAg with EIA. Conclusion: There is no evidence of HBV in the vitreous of asymptomatic HBV carriers.

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.