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Biomedical subjects

Lutz E Pillunat

Publications and source records attributed to Lutz E Pillunat.

9 recordsLinked to original sources
PubMed2006

Effect of central corneal thickness, corneal curvature, and axial length on applanation tonometry.

OBJECTIVE: To evaluate the effect of central corneal thickness (CCT), corneal curvature, and axial length on applanation tonometry in an in vivo study. METHODS: In a masked, prospective clinical trial, we examined 125 eyes of 125 patients scheduled for cataract surgery. Corneal curvature was measured by means of keratometry and axial length by A-scan ultrasonography. By cannulating the anterior chamber before surgery, intraocular pressure (IOP) was set to 20, 35, and 50 mm Hg in a closed system by means of a water column. After measuring thickness, the IOP was measured with an applanation tonometer. Pearson product moment correlations and multiple linear regression analyses were performed, and significance levels were evaluated by the paired, 2-tailed t test. RESULTS: The difference between measured and real IOP was significantly dependent (P < .001) on CCT. The associations between IOP and corneal curvature or IOP and axial length were not statistically significant (P = .31). The association between IOP reading and CCT is shown in the "Dresdner correction table," which illustrates an approximately 1-mm Hg correction for every 25-microm deviation from a CCT of 550 microm. The correction values were positive as thickness decreased and negative as thickness increased. CONCLUSIONS: Central corneal thickness significantly affects IOP readings obtained by applanation tonometry according to the Goldmann principle. A correction of IOP readings by considering CCT according to the Dresdner correction table might be helpful for determining an accurate IOP value.

Adolescent↗
PubMed2006

Biomechanical evidence of the distribution of cross-links in corneas treated with riboflavin and ultraviolet A light.

PURPOSE: To examine to which depth of the cornea the stiffening effect is biomechanically detectable. SETTING: Department of Ophthalmology, University of Dresden, Dresden, Germany. METHODS: Of 40 enucleated porcine eyes, 20 eyes were treated with the photosensitizer riboflavin (0.1%) and ultraviolet A (UVA) light (370 nm, 3 mW/cm2, 30 minutes); the other 20 eyes served as control. From each eye, 2 flaps of 200 microm thickness were cut with a microkeratome, and strips of 5 mm width and 7 mm length were prepared. Stress-strain behavior was measured with a material tester to characterize the stiffening effect. Five pairs of human donor eyes were tested in the same way. RESULTS: In porcine corneas, the stiffening effect was stronger in the anterior-treated flaps than in the posterior-treated flaps and the control flaps (P = .001). A 5% strain was achieved at a stress of 261.7 +/- 133.2 x 10(3) N/m2 in the anterior-treated flaps and 104.1 +/- 52.7 x 10(3) N/m2 in the anterior control flaps. The posterior-treated flaps (105.0 +/- 55.8 x 10(3) N/m2) and the posterior control flaps (103.7 +/- 61.8 x 10(3) N/m2) showed no difference (P = .95). A similar stiffening effect was observed in human eyes, but contrary to findings in porcine corneas, in human corneas the anterior control flaps were stiffer than the posterior control flaps (P = .027). CONCLUSIONS: Treatment of the cornea with riboflavin and UVA significantly stiffened the cornea only in the anterior 200 microm. This depth-dependent stiffening effect may be explained by the absorption behavior for UVA in the riboflavin-treated cornea. Sixty-five percent to 70% of UVA irradiation was absorbed within the anterior 200 microm and only 20% in the next 200 microm. Therefore, deeper structures and even the endothelium are not affected.

Aged↗
PubMed2005

The influence of various substances on the biomechanical behavior of lamina cribrosa and peripapillary sclera.

PURPOSE: Changes in the biomechanical properties of the lamina cribrosa (LC) and of the peripapillary sclera (ppSc) may play a role in the pathogenesis of glaucoma. The purpose of this study was to assess the influence of glyceraldehyde, methylglyoxal, and collagenase A on the mechanical properties of the LC and ppSc. METHODS: Two strips of 1-mm width were cut from each of 80 porcine eyes and 24 pairs of enucleated human eyes. One strip contained the LC and the other the adjacent superior ppSc. One half of the strips was divided into groups and treated with 0.5 M glyceraldehyde, 0.5 M methylglyoxal, and 0.1% collagenase A. The other strips served as the control. The stress strain relation was measured in the stress range of 0.02 to 6.0 MPa by a biomaterial tester. RESULTS: Stress values at 20% strain of the human LC changed from 1.97 +/- 1.48 to 3.40 +/- 1.60 MPa after incubation with glyceraldehyde (P = 0.029), from 2.42 +/- 2.22 to 5.46 +/- 1.91 MPa (P = 0.014) after incubation with methylglyoxal, and from 2.43 +/- 1.3 to 1.35 +/- 0.19 MPa after incubation with collagenase A. The stress values of human ppSc without glyceraldehyde were 3.40 +/- 2.59 and 7.45 +/- 4.46 MPa after incubation with glyceraldehyde (P = 0.047), 4.80 +/- 3.05 MPa without methylglyoxal and 16.10 +/- 5.53 MPa (P = 0.001) after incubation with methylglyoxal, 4.14 +/- 2.56 MPa without collagenase A, and 1.97 +/- 0.55 MPa after incubation with collagenase A. At a 20% strain, Young's moduli of the untreated LC were in the range of E = 11.8 to 15.6 MPa and E = 28.5 to 36.0 MPa of the untreated ppSc. CONCLUSIONS: Glyceraldehyde and methylglyoxal increase the stiffness of the LC and of the ppSc in human and in porcine eyes. These substances induce changes in the extracellular matrix according to the Maillard reaction as it occurs during the ageing process or in case of high blood glucose levels. Collagenase reduces the stiffness of the tissues.

Animals↗
PubMed2005

The effect of age on optic nerve head blood flow.

PURPOSE: To examine whether optic nerve head blood flow changes with aging. METHODS: One randomly chosen eye of each of 103 healthy subjects (age range, 22-76 years) was examined by laser Doppler flowmetry. Relative capillary blood flow, velocity, and volume of the moving red blood cells were measured at the temporal and nasal neuroretinal rim of the optic nerve head. For statistical analysis, linear regression analysis and partial correlations were calculated. RESULTS: Velocity increased with age. The Pearson correlation coefficient (R) between age and velocity was 0.49 temporally and 0.56 nasally. The correlation was significantly different from 0 (both P < 0.0005). Volume decreased with increasing age. The Pearson correlation coefficient between age and volume was -0.47 temporally and -0.40 nasally. The correlation was significantly different from 0 (both P < 0.0005). Flow decreased with increasing age. The Pearson correlation coefficient between age and flow was -0.27 temporally and -0.31 nasally. The correlations were significantly different from 0 (P = 0.006 and P = 0.002, respectively). Partial correlation coefficients between the perfusion parameters and age, after correcting for systolic and diastolic blood pressure, heart rate, gender, and IOP, were similar compared to the Pearson correlation coefficients and remained statistically significant. CONCLUSIONS: The perfusion of the optic nerve head is altered with increasing age. The results suggest that the blood supply is reduced in elderly subjects.

Adult↗
PubMed2004

[Reversible Perimacular Retinopathy by Long-Time Interferon alpha Therapy].

BACKGROUND: Recently interferon therapy has become increasingly important in the treatment of viral and malignant diseases. Subsequently, a variety of adverse effects of interferon use has been reported. Ocular complications following interferon therapy include retinal ischaemia with cotton wool spots, retinal haemorrhages, capillary nonperfusion, vasospasm, and arteriolar occlusion. CASE REPORT: A 37-year old male complained about increasingly blurred vision in his right eye. Because of a chronic type B hepatitis he has been treated with interferon alpha for a total of 35 weeks. Visual acuity was slightly reduced (OD cc 0.9, OS cc 1.0 p). Dilated fundus examination and fluorescein angiography showed an incipient ischaemic retinopathy with perimacular arteriolar alterations in both eyes and single cotton wool spots in his right eye. Perimetry showed a slight reduction of the mean deviation. Amsler-grid did not show any pathology. As the retinopathy was thought to be related to the interferon treatment, it was decided to discontinue this therapy immediately. 2 weeks later visual acuity was improved (OD cc 1.25 p, OS cc 1.0) and dilated fundus examination showed no signs of perimacular ischaemic retinopathy and the initial cotton wool spots had been resolved. CONCLUSION: In patients with long-time interferon treatment non-specific visual complaints like blurred vision or dark spots might be symptoms of an early ischaemic retinopathy. Retinal alterations might be reversible if treatment is discontinued. If an ischaemic retinopathy is present it should be considered to abandon interferon therapy, since permanent loss of vision has been described in advanced capillary non-perfusion and arteriolar occlusion. However, the decision to discontinue the interferon therapy should be made interdisciplinary while considering diagnosis and therapy indication.

Adult↗
PubMed2003

Short posterior ciliary artery, central retinal artery, and choroidal hemodynamics in brimonidine-treated primary open-angle glaucoma patients.

PURPOSE: Malfunction in peripapillary hemodynamics has been suggested to play a major part in the pathogenesis of primary open-angle glaucoma (POAG). The aim of this study was to determine whether topically applied brimonidine can influence blood hemodynamic characteristics associated with the perioptic short posterior ciliary arteries (SPCAs), central retinal artery (CRA), and choroidal vascular system in POAG patients. DESIGN: Randomized clinical trial. In this prospective, institutional, double-masked, vehicle-controlled, randomized clinical trial, the intraocular pressure (IOP) and vascular dynamics of the SPCAs, CRA, and choroidal vascular system were analyzed in both eyes of 17 POAG patients, before and after treatment with 0.2% brimonidine for 4 weeks. RESULTS: Mean IOP reduction was significant (18.7%) following treatment with brimonidine. However, no clear changes were recorded with respect to blood perfusion parameters (peak systolic velocity, end-diastolic velocity, pulsatility, and resistance indices) associated with the SPCAs and CRA or the choroidal ocular pulse amplitude. CONCLUSIONS: Topical treatment of brimonidine to POAG patients causes a significant reduction of IOP, but blood hemodynamic properties associated with the SPCAs, CRA, and choroidal vascular systems appeared unaffected. Topically applied brimonidine, therefore, appears not to constrict or dilate peripapillary blood vessels.

Administration, Topical↗
PubMed2003

[Diagnostic and therapeutic problems in chronic progressive external ophthalmoplegia (CPEO)].

BACKGROUND: Strictly speaking, CPEO is defined as paralysis of the external ocular muscles combined with ptosis. In Kearns-Sayre syndrome additional neurological or muscular deficits can be observed, sometimes even decades after the onset of ocular symptoms. METHOD: Three patients with classical CPEO and one patient with Kearns-Sayre syndrome where included in the present study. The clinical examinations included electromyography, various serological parameters and histological biopsies. RESULTS: The onset of ocular symptoms with divergent strabism and ptosis could be dated back to the age of 7, 27, 38 and 44 years starting on one eye and progressing slowly over years to both eyes. In the Kearns-Sayre syndrome patient a general decrease in cardio-respiratory fitness and occasional collapses were noted. In three patients ptosis and strabism surgery led to the relief of the ocular symptoms. CONCLUSIONS: In CPEO respectively Kearns-Sayre syndrome the onset of the disease is variable. The final correct diagnosis is often delayed due to the mild beginning of the symptoms and the slow progression of the paralyses. Early EMG and muscle biopsy examination may facilitate the diagnosis.

Adult↗
PubMed2002

Visual function and perfusion of the optic nerve head after application of centrally acting calcium-channel blockers.

BACKGROUND: In a previous study it was shown that nimodipine 30 mg twice daily leads to an improvement in the visual field in a subgroup of normal-pressure glaucoma patients. To understand the mechanism of action of nimodipine on the visual system, the aim of this study was to examine the influence of nimodipine on different hemodynamic parameters and contrast sensitivity in healthy subjects. METHODS: Thirty-two healthy subjects (21-49 years old, mean age 28 years, 10 male, 22 female) received either nimodipine 30 mg twice a day or a placebo according to the same dosage regimen in a double-blind cross-over study design. The ocular blood flow was measured by means of the ocular blood flow system, the optic nerve head blood flow with the continuous laser Doppler flowmeter (Riva), and contrast sensitivity using the MCT 8000 Multivision Contrast Tester. Measurements were taken at baseline (1T0), 120 min after initial dose (1T3) and after 3 days (3T3) of therapy with 150 mg nimodipine or placebo in total. RESULTS: Contrast sensitivity improved significantly throughout almost all spatial frequencies in the nimodipine-treated subjects ( P=0.01), whereas there was no change in the placebo group. Ocular blood flow and optic nerve head blood flow increased slightly but not significantly in the nimodipine group (1T0: 706.6 microl/min, 9.33 AU; 3T3: 854.3 microl/min, 9.39 AU) and remained unchanged or were even lower in the placebo group ( P>0.05). CONCLUSION: The results showed a significant increase in contrast sensitivity during treatment with nimodipine in healthy subjects. This increase in visual function, however, was not correlated with an increase in ocular or optic nerve head blood flow. Therefore, another mechanism, e.g., a direct effect on the visual system, might be responsible for the improvement in visual function in healthy volunteers under nimodipine therapy.

Adult↗