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Biomedical subjects

Yusuf Akar

Publications and source records attributed to Yusuf Akar.

At least 19 recordsLinked to original sources
PubMed2006

Phacoemulsification with topical anesthesia: Resident experience.

PURPOSE: To compare the intraoperative and postoperative complications and outcomes of phacoemulsification performed by residents using topical and retrobulbar anesthesia. SETTING: Two university ophthalmology departments. METHODS: One hundred fifty phacoemulsification procedures were performed by 3 residents who used retrobulbar anesthesia (retrobulbar group), and 146 phacoemulsification procedures were performed by another 3 residents who used topical anesthesia and who had no experience with retrobulbar or peribulbar anesthesia (topical group). Case notes were prospectively compared. The data analyzed included the ocular history, intraoperative and postoperative complications, and final best spectacle-corrected visual acuity (BSCVA). RESULTS: There were no differences between the 2 groups in complication rates. Anterior capsule tears occurred in 8 eyes (5.3%) in the retrobulbar group and 7 eyes (4.7%) in topical group. Capsulorhexis was continuous but not curvilinear in 14 eyes (9.3%) and 12 eyes (8.2%), respectively. Capsulorhexis tear or posterior capsule rupture that necessitated conversion to extracapsular cataract extraction occurred in 3 eyes (2.0%) in the retrobulbar group and in 1 eye (0.6%) in the topical group. Posterior capsule rupture with vitreous loss occurred in 10 eyes (6.6%) and 9 eyes (6.1%), respectively. Loss of lens fragments in the vitreous cavity occurred in 3 eyes (2.0%) and 4 eyes (2.7%), respectively. The 63 postoperative complications (41 eyes [27.3%], retrobulbar group; 22 eyes [15.0%], topical group) included cystoid macular edema, intraocular lens decentration, endophthalmitis, bullous keratopathy, transient intraocular pressure elevation, temporary corneal edema, and vitreous hemorrhage. Some cases had more than 1 complication. The BSCVA, including in eyes with preexisting ocular pathology, was 20/40 or better in 86.7% in the retrobulbar group and 84.9% in the topical group. CONCLUSION: When supervised and in selected patients, residents who have no retrobulbar or peribulbar anesthesia experience can safely perform phacoemulsification using topical anesthesia.

Adult↗
PubMed2006

Brinzolamide 1% versus apraclonidine 0.5% to prevent intraocular pressure elevation after neodymium:YAG laser posterior capsulotomy.

PURPOSE: To compare the efficacy of brinzolamide 1% with that of apraclonidine 0.5% in preventing intraocular pressure (IOP) rise after neodymium:YAG (Nd:YAG) laser posterior capsulotomy. SETTING: Department of Ophthalmology, Akdeniz University, Antalya, Turkey. METHODS: One hundred fifteen patients who had Nd:YAG laser posterior capsulotomy for posterior capsule opacification were prospectively randomized to receive brinzolamide 1% (57 patients) or apraclonidine 0.5% (58 patients) approximately 1 hour before laser surgery. A masked observer measured IOP by Goldmann applanation tonometry before treatment and after treatment at 1, 2, and 3 hours and 7 days. RESULTS: The mean IOP changes from baseline were not statistically different between the study groups at 1, 2, and 3 hours and 7 days (P =.109, P = .764, P =.275, and P =.879, respectively). The incidence of IOP elevation of 5 mm Hg or higher was 12.2% (7 of 57 eyes) in the brinzolamide group and 10.3% (6 of 58 eyes) in the apraclonidine group (P = .743); IOP elevations of 10 mm Hg and greater occurred in 3.5% (2 of 57 eyes) and 1.7% (1 of 58 eyes) (P = .618), respectively. There were no IOP elevations greater than 20 mm Hg in either group. CONCLUSION: Brinzolamide 1% and apraclonidine 0.5% given prophylactically before Nd:YAG laser capsulotomy were effective in preventing IOP spikes after treatment.

Adrenergic alpha-Agonists↗
PubMed2006

Outbreak of toxic anterior segment syndrome associated with glutaraldehyde after cataract surgery.

PURPOSE: To present clinical findings of a cluster of cases of toxic anterior segment syndrome (TASS) after uneventful phacoemulsification cataract surgery. SETTING: Department of Ophthalmology, Akdeniz University, Antalya, Turkey. METHODS: Six eyes of 6 patients developed TASS after uneventful phacoemulsification cataract surgery with implantation of a 3-piece acrylic IOL performed by 2 ophthalmologists on the same day. Clinical findings included corneal edema, Descemet's membrane folds, anterior chamber reaction, fibrin formation, and irregular, dilated, and unreactive pupils. RESULTS: Glutaraldehyde 2% solution was used inadvertently by the operating room staff who cleaned and sterilized reusable ocular instruments before autoclaving. None of the affected corneas improved. Additional surgical procedures were required and included penetrating keratoplasty, trabeculectomy, and glaucoma tube implantation. CONCLUSIONS: Glutaraldehyde in concentrations generally used for cold sterilization is highly toxic to the corneal endothelium. The operating room staff involved in sterilizing instruments should be well educated about and careful to follow the protocols to properly clean and sterilize reusable ocular instruments.

Aged↗
PubMed2006

Transmission electron microscopy and autofluorescence findings in the cornea of diabetic rats treated with aminoguanidine.

BACKGROUND: The accumulation of advanced glycation end products (AGEs) has been implicated in the pathogenesis of diabetic keratopathy. The present study was aimed to understand if aminoguanidine (AG), an AGE inhibitor, was protective against the development of corneal complications in a diabetic rat model. METHODS: Wistar rats were divided into three experimental groups: control, diabetic, and AG-treated diabetic. Diabetes was induced in rats via a single intraperitoneal injection (60 mg/kg) of streptozocin (STZ) and AG was administered in drinking water at a dose of 1 g/L. All animals were sacrificed at the end of 10 weeks and corneas from diabetic and nondiabetic rats were analyzed via transmission electron microscopy (TEM). Corneal autofluorescence measurements were also performed in all experimental groups. RESULTS: Electron microscopic evaluation revealed that aminoguanidine treatment in diabetic rats prevented the formation of intracellular spaces between neighbouring cells in the superficial corneal epithelium. Hyperglycemia-induced degeneration of intracellular organelles and formation of cytoplasmic vacuoles in the corneal stroma was also prevented with the treatment of AG. Corneal autofluorescence detected in the diabetic group (5.98 +/- 2.17 Fi/mg protein) was found to be significantly greater than the control (3.92 +/- 0.56 Fi/mg protein) and the AG-treated diabetic group (4.18 +/- 0.59 Fi/mg protein) (p < 0.05). INTERPRETATION: The presented data provide evidence that AG is preventive against corneal alterations in experimental diabetes.

Animals↗
PubMed2006

Nitrotyrosine formation and apoptosis in rat models of ocular injury.

This study was performed to examine inducible nitric oxide synthase (NOS-2) expression, nitrotyrosine formation and apoptosis in rats with elevated intraocular pressure (IOP) and/or ocular inflammation. Ocular inflammation was induced via injection of intra-vitreal lipopolysaccharide (LPS) while IOP was elevated by episcleral vessel cauterization. Animals were randomized to one of the following conditions: elevated IOP, LPS, elevated IOP+LPS, and control. Immunohistochemical staining and western blot analysis of retinal lysates revealed NOS-2 and nitrotyrosine immunoreactivity in all disease groups. NOS-2 expression and protein nitration was significantly greater in rats with elevated IOP+LPS compared to elevated IOP, LPS, and control groups. Nitrite levels in the retina affirmed significantly increased levels of nitric oxide generation in LPS-treated rats with elevated IOP (346+/-23.8 microM) vs LPS-treated, elevated IOP and control groups (195.6+/-12.6, 130+/-2.5 and 76.6+/-15.6 microM, respectively). Retinal TUNEL staining showed apoptosis in all diseased groups. Percent of apoptotic cells was significantly greater in the elevated IOP+LPS group compared to LPS-treated or elevated IOP groups. Presented data illustrates that both elevated IOP and ocular inflammation augment NOS-2 expression, retinal protein nitration and apoptosis in rats.

Animals↗
PubMed2005

Menstrual cycle-dependent changes in white-on-white visual field analysis of diabetic women.

AIM: To determine the effect of the menstrual cycle on white-on-white perimetry (WWP) tests of diabetic women. SUBJECTS AND METHODS: Left eyes of 129 normally menstruating women (81 type 1 diabetes mellitus (DM) with mild (n = 43) and severe (n = 38) non-proliferative diabetic retinopathy (NPDR), and 48 healthy control females) were included in the study. All subjects underwent complete ocular examination and WWP tests both in the follicular (7-10th day of the cycle) and luteal phases (days 3-7 before the bleeding) of two consecutive menstrual cycles. WWP was performed using Humphrey Field Analyzer II with SITA Standard, central 30-2 program. Mean sensitivity (MS) of points located at central 3, 9, 15, 21 and 27 degrees retinal locations (4, 12, 18, 24 and 16 points, respectively) were calculated in all menstrual phases. RESULTS: The mean age of diabetic patients with mild and severe NPDR and control subjects were 28.8 +/- 4.7, 30.1 +/- 5.9 and 29.4 +/- 5.1 years, respectively (p > 0.05). Their mean MS values were 30.7 +/- 1.0, 30.4 +/- 1.0 and 30.8 +/- 0.8 dB, respectively (p > 0.05). Diabetic patients with severe NPDR demonstrated significant decreases in mean MS values of peripheral 21 and 27 degrees visual field locations in the luteal phase (p < 0.05). However, changes in that of the locations within central 15 degrees visual field were non-significant (p > 0.05). Diabetic patients with mild NPDR and control subjects demonstrated no significant changes in mean MS values of any of the visual field locations (p > 0.05). CONCLUSION: Peripheral, rather than central, locations of central visual field of diabetic women with severe NPDR demonstrated a significant retinal sensitivity loss in the luteal phase. These findings should be taken into consideration during the clinical follow-up of diabetic women at risk of glaucoma and ocular hypertension.

Adult↗
PubMed2005

Cataract progression after intravitreal triamcinolone injection.

PURPOSE: To assess cataract progression after intravitreal triamcinolone injection. DESIGN: Retrospective, interventional, case-control study. METHODS: Forty-two phakic eyes of 37 patients were injected one, two, or three times with intravitreal triamcinolone for various indications. Noninjected phakic fellow eyes served as the control. The mean follow-up time for single injection was 12 months, for multiple injections was 14 months, and for control group was 13 months. Lens status, best-corrected visual acuity, and refractive errors were recorded at baseline and at each follow-up examination. RESULTS: At the last follow-up, changes in posterior subcapsular cataract and refractive error from baseline were significantly different between single triamcinolone-injected eyes and the control group [0.7 +/- 0.2 (mean +/- SEM [arbitrary unit] vs 0.2 +/- 0.1, P = .02; and -0.5 +/- 0.1 diopter vs -0.2 +/- 0.1 diopter, P = .01, respectively). For multiple-injected eyes and control eyes, change from baseline in corticonuclear cataract (1.1 +/- 0.2 vs 0.2 +/- 0.1), posterior subcapsular cataract (1.1 +/- 0.2) and refractive error (-1.8 +/- 0.4 diopters) were significantly different (P < .001, P < .001, and P < .001, respectively). Visual acuity did not change after single injection (P = .83) and in control group (P = .19) but decreased after multiple injections (P = .006). Eleven study eyes and two control group eyes underwent cataract extraction during study period. Corticonuclear and posterior subcapsular cataract progression significantly correlated with follow-up time (P = .003 and P = .02, respectively) and number of injections (P = .01 and P = .04, respectively). CONCLUSIONS: Single intravitreal triamcinolone injection induces posterior subcapsular cataract development, whereas multiple injections result in all-layer cataract progression.

Aged↗
PubMed2005

Influence of relaxing retinotomy on surgical outcomes in proliferative vitreoretinopathy.

PURPOSE: This study sought to determine the influence of relaxing retinotomy (RR) incisions upon surgical outcomes in the repair of recurrent retinal detachment (RD) attributable to proliferative vitreoretinopathy (PVR). DESIGN: Retrospective, consecutive, nonrandomized, single-center series. METHODS: Eighty-one eyes with recurrent RD attributable to PVR were retrospectively reviewed. Exclusion criteria were giant retinal tear, uveitis, trauma, proliferative diabetic retinopathy, and age under 18 years. A total of 52 eyes underwent RR at the time of surgery (64.2%); 29 eyes were repaired without this technique. Perfluorocarbon gas (n = 34) or silicone oil (n = 47) was used as postoperative tamponade. Statistical analyses were performed using the Fisher exact test. RESULTS: Eyes that received RR had significantly higher rates of anterior PVR (P = .009). Eyes receiving silicone oil for postoperative tamponade had worse baseline characteristics compared with those receiving gas. The use of RR in eyes receiving gas tamponade had no marked influence on the initial anatomic outcomes, with recurrent retinal detachment occurring in five of 14 eyes that received an RR and seven of 20 eyes that did not receive an RR (P = .62). Eyes in which silicone oil was used as a postoperative tamponade had a significantly lower rate of recurrent RD requiring additional surgery when RR was employed (one of 38 eyes) when compared with eyes that did not receive an RR (three of nine eyes, P = .02). Ultimately, surgical reattachment was attained in all eyes except one. Eyes that received gas tamponade without RR had significantly better median vision (P = .008). CONCLUSIONS: Surgical management of PVR often results in ultimate retinal reattachment. An RR incision does not appear to influence initial anatomic repair when gas tamponade is used after vitrectomy surgery for PVR. However, RR may increase the initial surgical success rate in eyes receiving silicone oil tamponade for PVR. In eyes undergoing RR for the treatment of severe PVR, the use of silicone oil may increase the initial rate of reattachment compared with the use of gas tamponade.

Adult↗
PubMed2005

Long-term fluctuation of retinal sensitivity during pregnancy.

BACKGROUND: We investigated the effect of pregnancy on the long-term fluctuation of retinal sensitivity in healthy women. METHODS: Candidates for the study were healthy women who were likely to become pregnant. A complete ocular examination of both eyes was performed in 41 women, and 1 eye each was chosen at random for the study. This initial examination included 2 sets of visual field measurements consisting of 5 individual measures done at least a day apart. After pregnancy, ocular examinations were repeated once between 10 and 15 weeks of gestation and once between 29 and 34 weeks. The mean threshold sensitivity (MS) of the visual field and the coefficient of variation of MS measurements for upper temporal, upper nasal, lower temporal, and lower nasal quadrants were calculated in each series. RESULTS: The visual field MS of the subjects increased significantly in the third trimester (p < 0.01). The coefficient of variation of the visual field MS measurements did not change significantly in the nasal quadrants. However, it decreased significantly in both upper and lower temporal quadrants. INTERPRETATION: Visual field MS and the reproducibility of MS measurements for temporal visual field increased significantly in the third trimester of the pregnancy. Further studies on the role of pregnancy-related ocular hemodynamic changes may provide insight into the etiopathogenesis of hormone-related processes.

Adult↗
PubMed2005

Effect of the menstrual cycle on the optic nerve head in diabetes: analysis by confocal scanning laser ophthalmoscopy.

BACKGROUND: The purpose of this study was to examine and compare menstrual-cycle-dependent topographic changes in the optic nerve head of normally menstruating women with different grades of type 2 diabetes mellitus. METHODS: We studied the right eyes of 123 normally menstruating women (36 with severe nonproliferative diabetic retinopathy [NPDR], 42 with mild NPDR and 45 healthy subjects). All subjects underwent a complete ocular examination at baseline. At 4 hormonally distinct phases of the menstrual cycle (early follicular, late follicular, mid-luteal and late luteal), we analysed the topography of the optic nerve head, using a confocal scanning laser ophthalmoscope, and measured the serum levels of estradiol, progesterone and luteinizing hormone. RESULTS: We excluded from analysis the data for 8 patients with severe NPDR, 10 patients with mild NPDR and 15 control subjects who were lost to follow-up examinations during the menstrual cycle. The mean age and optic disc area did not differ significantly among the 3 groups. The duration of diabetes was significantly longer in the patients with severe NPDR than in those with mild NPDR (p < 0.05). The women with severe NPDR had a significantly increased neuroretinal rim area and a significantly decreased cup-shape measure, linear cup/disc ratio, cup/disc area ratio and cup area in the late luteal phase compared with the other phases of the menstrual cycle (p < 0.05). Those with mild NPDR or a normal retina had no significant topographic changes in the optic nerve head during the menstrual cycle. INTERPRETATION: Severe NPDR is associated with significant topographic changes in the rim and cup of the optic nerve head during the menstrual cycle. This must be considered in the evaluation of women with both diabetes and glaucoma. The normal fluctuations in serum sex hormone levels during the menstrual cycle of diabetic women seem to affect the optic nerve head more when the disease is advanced.

Adult↗
PubMed2005

Effect of the menstrual cycle on standard achromatic and blue-on-yellow visual field analysis of women with migraine.

BACKGROUND: It has been postulated that migraine and glaucoma may have common vascular causative factors. Significant sex-based differences in the incidence of many important ocular conditions raise the possibility that estrogens may have direct effects on the eye. We performed a study to determine the effect of the menstrual cycle on standard achromatic automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) (blue-on-yellow perimetry) of women with migraine. METHODS: Both eyes of 73 normally menstruating women (31 subjects with migraine and 42 healthy control subjects) were included in the study. Subjects underwent a complete ocular examination including SAP and SWAP in both the follicular phase (12th to 13th day of the cycle) and the luteal phase (1 to 2 days before the onset of bleeding) of two consecutive menstrual cycles.We performed visual field analysis using the Humphrey Field Analyzer II with the full-threshold central 30-2 program. Mean sensitivity was calculated for the superior temporal, inferior temporal, superior nasal and inferior nasal regions separately. RESULTS: Thirteen subjects were lost to follow-up (5 in the migraine group and 8 in the control group), leaving 26 subjects and 34 subjects respectively. There was no significant difference in mean age between the two groups (33.9 years [standard deviation (SD) 3.4 years] vs. 35.1 years [SD 3.3 years]). The mean duration of migraine was 7.6 (SD 3.1) years (range 3-14 years). In both groups, serum estradiol levels were significantly lower (p = 0.001) and serum progesterone levels were significantly higher (p < 0.001) in the luteal phase than in the follicular phase. In the control group, the mean sensitivity values with SWAP were significantly lower in the luteal phase than in the follicular phase (p = 0.04). A similar decrease was observed for the subjects with migraine with both SAP and SWAP (p = 0.01). There was no difference in regional mean sensitivity between the two phases with either perimetric test in the control group. For the subjects with migraine, there was no difference in regional mean sensitivity between the two phases with SAP. However, with SWAP, the mean sensitivity for the nasal visual field locations was significantly lower in the luteal phase than in the follicular phase (p = 0.01). INTERPRETATION: Our study provides further evidence of an effect of sex hormones on the visual field of women with migraine. In addition to assessment of intraocular pressure, menstrual cycle phases should be considered in women with migraine at risk for glaucomatous optic neuropathy.

Adult↗
PubMed2005

The effect of the menstrual cycle on the optic nerve head analysis of migrainous women.

PURPOSE: To determine the effect of the menstrual cycle on the optic nerve head topographic analysis of normally menstruating migrainous women. MATERIAL AND METHODS: Randomly selected one eye of 44 migrainous and 49 healthy control women with regular menstrual cycles were included in the study. All subjects underwent complete ocular examination. Optic nervehead topographic analysis were performed using a confocal scanning laser ophthalmoscope, HRT II (Heidelberg Retinal Tomograph II, software version 1.6;Heidelberg Engineering, Heidelberg, Germany). They were repeated for two times during the menstrual cycle: in follicular phase (7th to 10th day of the cycle) and in the luteal phase (days 3 to 4 before the menstrual bleeding). Serum estradiol, progesterone, and luteinizing hormone measurements were repeated at each menstrual phase. RESULTS: The mean age of migrainous and control subjects were 31.5 + 5.1 years and 33.4 +/- 3.7 years, respectively (P > 0.05). Their mean disc areas were 2.26 +/- 0.46 mm(2) and 1.95 +/- 0.39 mm(2), respectively(P < 0.05). Control subjects did not demonstrate any difference in the disc topography (P > 0.05). The parameter rim volume decreased, while the parameters cup volume and cup shape measure increased significantly in the luteal phase of the migrainous women (all P values <0.05). Mean intraocular pressure of the migrainous women decreased significantly in luteal phase (P < 0.05). CONCLUSION: Significant differences exist in the optic rim and cup parameters during the menstrual cycle of the migrainous women. Further clinical trials on ocular blood flow changes during the menstrual cycle of the migrainous women may highlight the role of sex steroids in the optic nerve head of the migrainous women.

Adolescent↗
PubMed2005

Menstrual cycle-dependent differences between right and left visual hemifields in perimetry.

PURPOSE: To evaluate the effect of the menstrual cycle and gender on right and left visual hemifields in healthy subjects. METHODS: One randomly selected eye from each of 42 healthy normally menstruating women and of 37 men with no systemic and ocular problems, other than refractive error, were included in the study. Subjects underwent complete ocular examination and standard acromatic perimetric (SAP) and short-wavelength automated perimetric (SWAP) analysis in both follicular (7th to 10th day of the cycle) and luteal phases (days 3 to 7 before the menstrual bleeding) of the menstrual cycle. Visual field analysis was performed using Model 750 Humphrey Field Analyzer II (Carl Zeiss Meditec, Dublin, CA, USA) with full-threshold, central 30-2 program. RESULTS: The mean age of female (n = 42) and the male subjects (n = 37) were 35.2 +/- 3.1 years and 34.8 +/- 2.9 years, respectively (p = 0.58). Neither females nor males showed any statistically significant differences in the right and left hemifield tests with SAP (both p values > 0.05). However, using SWAP, in luteal phase of female subjects, left hemifield sensitivity was significantly less than (with a mean of 0.47 dB) right hemifield. In follicular phase, there was no significant interhemifield difference (p > 0.05). Male subjects did not show any significant differences between the sensitivity of the two hemifields with SWAP tests. CONCLUSIONS: There has been a significant difference between the mean SWAP sensitivity of right and left visual hemifields in luteal phase of the menstrual cycle. In case of a suspected hemifield difference, SAP rather than SWAP may be used to confirm suspected neurological defects as SAP is not affected by the menstrual cycle.

Adult↗
PubMed2005

Systemic toxicity of tacrolimus given by various routes and the response to dose reduction.

PURPOSE: To evaluate the long-term systemic toxicity of tacrolimus (FK-506) administered by various routes, and to assess the effect of dose reduction on toxicity. METHODS: The study animals were 120 experimentally naive adult female Wistar rats weighing 200-250 g each. The rats were randomly divided into 10 equal groups (n=12 in each) and treated with tacrolimus administered topically (in drops, 0.3%, q.i.d.), intravitreally (0.5 mg/kg bodyweight/week), intramuscularly (1 mg/kg bodyweight/week), low-dose intravenously (1 mg/kg bodyweight/week) and in high-dose intravenously (2 mg/kg bodyweight/week) for 3 months. The rats in the control groups (one for each different route of administration) were treated with 0.9% NaCl. The blood concentration of tacrolimus, complete blood count and biochemistry parameters were measured each month for the 3-month study period. RESULTS: The rats in the control groups and experimental groups administered topical and intravitreal tacrolimus did not demonstrate any systemic toxic effects. The rats that developed certain toxic effects (hyperglycaemia, hyperkalaemia and nephrotoxicity) in the groups given low-dose or high-dose i.v. tacrolimus responded well to dose reduction. Following dose reduction, blood glucose concentrations decreased from 247.4 +/- 42.3 mg/dL to 189.6 +/- 37.9 mg/dL (P <0.05), and from 237.4 +/- 41.1 mg/dL to 182.3 +/- 22.7 mg/dL (P <0.05) in the low- and high-dose i.v. tacrolimus-treated rats, respectively. The rats that developed impaired hepatic function after high-dose tacrolimus did not respond to dose reduction. Baseline cholesterol concentrations for the intramuscular and low- and high-dose i.v. tacrolimus-treated groups, demonstrated decreases, respectively, from 87.4 +/- 14.0 mg/dL, 86.4 +/- 14.0 mg/dL and 90.4 +/- 14.3 mg/dL to 53.6 +/- 9.8 mg/dL, 52.1 +/- 12.5 mg/dL and 63.5 +/- 11.7 mg/dL by the end of the second month. The differences were found to be statistically significant (P <0.05 for each result). CONCLUSION: Topical or intravitreal administration of tacrolimus seems to be systemically safe whereas parenteral administration can cause some systemic haematological changes such as dose-dependent decreased serum cholesterol concentrations. Dose reduction may prevent such adverse effects.

Administration, Topical↗
PubMed2004

Effect of hypercholesterolemia on inducible nitric oxide synthase expression in a rat model of elevated intraocular pressure.

PURPOSE: This study was performed to examine the effect of hypercholesterolemia on inducible nitric oxide synthase (NOS-2) expression and oxidative tissue injury in an experimental rat model of elevated IOP. METHODS: Wistar rats were maintained on either regular chow or a high-cholesterol diet for 24 weeks. Intraocular pressure (IOP) was elevated in hypercholesterolemic rats by unilaterally cauterizing three episcleral vessels. Rats were divided into four experimental groups as follows; hypercholesterolemia, hypercholesterolemia+elevated IOP, elevated IOP and control. NOS-2 distribution, lipid peroxidation and retinal nerve fiber layer (RNFL) thickness was evaluated in all experimental groups at the end of 24 weeks. RESULTS: Light microscopic evaluation of retinas in hypercholesterolemic rats revealed breaks and discontinuation in focal areas in the outer nuclear layer (ONL). NOS-2 positive staining was observed throughout the outer plexiform layer (OPL), inner plexiform layer (IPL) and ganglion cell layer (GCL) in rats with elevated IOP and/or hypercholesterolemia. Calculated values of RNFL thickness in hypercholesterolemic rats were significantly higher than those in the control and elevated IOP group. Vitreous malondialdehyde (MDA) levels detected in elevated IOP (3.51+/-0.31 nmol/mg protein) and hypercholesterolemia+elevated IOP (5.14+/-1.28 nmol/mg protein) groups were significantly higher than those detected in hypercholesterolemic (1.92+/-1.43 nmol/mg protein) and control (1.89+/-0.24 nmol/mg protein) groups. CONCLUSION: The presented data confirms hypercholesterolemia as a risk factor in the development of glaucomatous optic neuropathy (GON) and suggests that increased circulating cholesterol may exacerbate disease progression by inducing NOS-2 expression and elevating oxidant tissue injury.

Animals↗
PubMed2004

Major determinants of optic nerve head topographic characteristics in a normal Turkish population.

AIM: To determine the factors affecting the topographic characteristics of the optic nerve head in a normal Turkish population. METHODS: A cross-sectional study was performed on the optic nerve head of the right eyes of 613 healthy subjects of both sexes aged 11-77 years using a confocal scanning laser ophthalmoscope. The study population was divided into three groups (<20 years, 20-50 years, and>50 years) to evaluate age-related changes in the optic nerve head topography. A total of 15 variables were determined. Statistical analysis was performed using Student's t-test, anova, Tukey HSD test, linear regression analysis and Pearson's correlation coefficient. RESULTS: Four eyes were excluded from the study due to poor image quality. There were 307 female subjects and 302 male subjects. The mean age of the subjects was 42.1 +/- 15.1 years. The mean optic disc areas were 1.99 +/- 0.45 mm2 and 1.97 +/- 0.41 mm2 for male and female subjects, respectively. The disc area of the subjects ranged between 1.01 and 4.19 mm2. Disc area was found to be associated with all of the optic nerve head variables studied, and was also found to be significantly increased with advancing age (P < 0.05). The only variable that showed a sex-related difference was neuroretinal rim volume, which was found to be higher in female subjects in all cases. CONCLUSION: Optic disc area was found to be the main determinant of the optic nerve head topography in a normal population. Optic disc area was found to be significantly increased with ageing in a normal population. These acquired changes to the optic disc could suggest stretching of the scleral ring, which may highlight the role of advancing age on the pathogenesis of glaucomatous optic neuropathy.

Adolescent↗
PubMed2004

The effect of prematurity on tear production.

PURPOSE: To evaluate the effect of the birth weight and the postconceptional age on the tear production of preterm and term newborn infants and to evaluate the changes in tear production during the first two months of life. SUBJECTS--METHODS: Both eyes of medically stable term and preterm infants were included in the study. Based on postconceptional age and birth weight, we divided preterm infants into three groups. Then, we measured the basal and reflex tear secretions of both eyes by Schirmer tests before and after instillation of topical anesthetic agent. We performed initial tear measurements on the second day of life (between first 24 hours to first 48 hours after birth): and at 2 weeks, 4 weeks and 8 weeks after birth. RESULTS: We tested a total of 138 infants (63 preterm and 75 term), 72 males and 66 females. Schirmer-1-test of preterm and terms on the 2nd day of life revealed a mean basal tear secretion (BTS) of 4.8 +/- 4.1 and 8.8 +/- 3.2 mm, respectively (p < 0.0001). The mean reflex tear secretion (RTS) within 48 hours of life was 6.1 +/- 3.9 mm and 10.3 +/- 4.4 mm in preterm and term infants, respectively (p < 0.0001). The mean values of both basal and reflex tear secretion were significantly lower in the preterm than the term infants during the first two months of the life. In preterm infants, both basal and reflex tear secretions were found to be highly correlated with postconceptional age (r: 0.79 and 0.74, respectively, both p values: 0.001); however, there was a weak correlation with birth weight (r: 0.16 and 0.19, respectively, both p values: 0.01). Statistically significant differences for both BTS and RTS existed among the three postconceptional age groups: there were no such difference among the three different birth weight groups. We found no gender or laterality dependent (side of the eyes) differences in the tear production (both p values >0.05). CONCLUSIONS: Preterm infants have significantly reduced tear secretion compared with term infants. Postconceptional age, rather than birth weight, seems to be more correlated with the tear secretion. Sex and laterality does not appear to have an effect on tear production in infants. Tear production of preterm infants is significantly reduced than that of term infants during the first two months of life. Term infants increased their tear production significantly in each examination during the neonatal period while the preterms increase tear production significantly only at mean postconceptional age of eight and a half (8.5) months.

Birth Weight↗