Karl-Georg Schmidt

Influence of physical exercise and nifedipine on ocular pulse amplitude

Abstract• Background: Ocular pulse amplitude (OPA) was measured to investigate the influence of peripheral vasoconstriction and vasodilatation on choroidal perfusion in healthy volunteers and to determine whether low OPA in low-tension glaucoma (LTG) patients is associated with a vasospastic reaction and its response to the calcium channel blocker nifedipine.• Methods: OPA was determined using the Langham ocular blood flow (OBF) system, applanation intraocular pressure (IOP), systemic blood pressure, and heart rate were measured, and ocular perfusion pressure was calculated before and after exercise and smoking in 12 otherwise nonsmoking, healthy volunteers and prior to and for 3 months after initiation of nifedipine therapy in 32 LTG patients with and without a vasospastic reaction as manifested by a nailfold capillary blood flow test.• Results: Exercise significantly (P<0.05) increased heart rate, systolic blood pressure and ocular perfusion pressure, while it significantly (P<0.05) reduced IOP and diastolic blood pressure. However, OPA was not significantly (P>0.1) affected by changes in these parameters. Smoking significantly (P<0.05) increased systolic and diastolic blood pressure, heart rate, and ocular perfusion pressure but did not significantly (P>0.09) alter OPA. There were two distinct LTG subtypes, with and without a vasospastic reaction. Only those with a vasospastic reaction showed a significant (P<0.001) increase in OPA after 3 months of nifedipine treatment, while all other parameters tested were not significantly altered.• Conclusion: Despite affecting ocular and systemic perfusion parameters, exercise and smoking did not alter OPA, suggesting functional isolation, i.e. autoregulation of the choroidal and/or ophthalmic artery circulation in healthy volunteers. Low OPA in LTG was increased by nifedipine only in vasospastic LTG patients, suggesting different, vasotonus-related pathologies. Calcium channel blockers and other vasodilators may be useful in vasoreactive LTG patients with reduced OPA.

Ocular pulse amplitude in diabetes mellitus.

BACKGROUND The influence of diabetes mellitus on ocular pulse amplitude (OPA), an indirect measure of choroidal perfusion, is unclear. METHODS OPA, using the Langham ocular blood flow (OBF) system, applanation intraocular pressure (IOP), systemic blood pressure (BP), heart rate, and haemoglobin (Hb) A1c were measured in patients with insulin dependent diabetes mellitus (IDDM) with no (DR-0, n = 22) non-proliferative (DR-1, n = 24), and proliferative (DR-2, n = 18) diabetic retinopathy. RESULTS Neither local (OPA, IOP) nor systemic perfusion parameters (BPs, HR) nor HbA1c were significantly altered in DR-0, DR-1, or DR-2 IDDM patients. CONCLUSION Choroidal circulation remains unaffected as diabetic retinopathy advances.

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.

Influence of Panretinal Photocoagulation on the Ocular Pulse Curve

PURPOSE To study the ocular pulsation amplitude (an indicator of choroidal circulation) and systolic ophthalmic artery pressure after panretinal photocoagulation. METHODS Prospectively, in 10 patients with diabetes mellitus (eight with type II and two with type I; mean age, 64 years) and severe, hitherto untreated, bilateral proliferative diabetic retinopathy, we performed intensive, unilateral panretinal photocoagulation with 1,500 argon laser burns (spot size, 500 microm) in two sessions (interval, 3 weeks). Before and (in 3-week intervals) up to 9 weeks after treatment, we recorded ocular pulse curves using oculo-oscillodynamography and determined each patients ocular pulsation amplitude and systolic ophthalmic artery pressure. RESULTS Compared with the untreated contra-lateral eyes, panretinal photocoagulation led to a reduction of ocular pulsation amplitude. Three weeks after the first coagulation, the reduction averaged 20%. Maximum reduction was found 9 weeks after onset of treatment (6 weeks after the second coagulation) and amounted to 29.9%. The differences between photocoagulated and untreated eyes were highly significant on average (P < .01; analysis of variance) as well as for time course (P < .001). Systolic ophthalmic artery pressure was not changed significantly during panretinal photocoagulation follow-up. CONCLUSIONS Ocular pulsation amplitude is determined by the cardiac cycle-related intraocular volume changes that depend predominantly on choroidal blood flow. The morphologic substrate is probably choriocapillary closure after photocoagulation.

Autofluorescence of the retinal pigment epithelium in patients with central serous chorioretinopathy

SummaryPurpose: The lack of histopathological material has placed limitations on our knowledge on lipofuscin in central serous chorio-retinopathy (CSCR). This study was designed to document the pathological changes of the retinal pigment epithelium (RPE) in CSCR using in vivo recording of fundus autofluorescence. Methods: Fundus autofluorescence was documented in 62 eyes of 44 subjects with CSCR using a laser scanning ophthalmoscope (Zeiss, Oberkochen; excitation wavelength: 488 nm, barrier filter at 521 nm). Images were compared to the respective fundus appearance and fluorescein angiograms. Results: Neurososensory retinal detachments showed diffuse increased autofluorescence corresponding to the detached area. Long-standing lesions showed very irregular autofluorescence with regions greater and less than the background levels of autofluorescence. Conclusion: Focal accumulation of autofluorescent material occurs at the level of the RPE in patients with CSCR, relating to variation in metabolic activity of the RPE. This technique may be useful in selecting patients for laser photocoagulation.ZusammenfassungHintergrund: Der Mangel an histopathologischem Material begrenzte bisher den Wissensstand über die strukturellen Veränderungen bei Chorioretinopathia centralis serosa (CRCS). Ziel dieser Arbeit war es, anhand der Methode der bildlichen Darstellung der Fundus-Autofluoreszenz Erkenntnisse über die pathologischen Veränderungen des retinalen Pigmentepithels (RPE) bei CRCS zu gewinnen. Patienten und Methoden: Das Verteilungsmuster von Lipofuszin im RPE wurde mit einem konfokalen Laser Scanning Ophthalmoskop (LSO, Zeiss, Oberkochen; Exzitationswellenlänge: 488 nm, Leistung: 250 μW, Filter ab 521 nm, Bildauflösung: 768 × 572 Pixel) an 62 Augen von 44 Patienten mit CRCS untersucht. Ergebnisse: Die Areale mit subretinaler Flüssigkeitsansammlung entsprachen im Frühstadium einer vermehrten Fundus-Autofluoreszenz, im fortgeschrittenen Stadium einem gemischten Bild von vermehrter und verminderter Autofluoreszenz. Schlußfolgerungen: Die Veränderungen der Autofluoreszenz im RPE, ein Index der Stoffwechselaktivität, treten bei CRCS fokal auf. Der Nachweis vorhandener, reduzierter oder fehlender Stoffwechselaktivität des RPE könnte zur Indikationsstellung einer Lasertherapie beitragen.

Clonidine provides an allergy-free alternative in glaucoma patients with proven allergy to apraclonidine

Abstract · Purpose: The aim of this study was to determine allergic responses to clonidine hydrochloride 0.25% in glaucoma patients with proven allergic reaction to apraclonidine 0.5%. · Methods: Fifteen consecutive glaucoma patients with allergic reaction to apraclonidine were prospectively challenged with clonidine hydrochloride 0.25% and evaluated for recurrence of allergic reactions and efficacy of treatment. Intraocular pressure (IOP), conjunctival hyperemia, blood pressure and resting pulse rate were determined at baseline and after 1, 3, 6 and 12 months. · Results: None of the patients developed ocular allergic reaction during 12 months on clonidine therapy. Blood pressure and pulse rate did not change significantly with clonidine treatment. Clonidine caused a significant reduction of IOP from baseline. In one patient, topical clonidine caused fatigue, dizziness and dry mouth. · Conclusion: Clonidine did not cause allergic reaction in patients with proven allergy to apraclonidine, indicating that there is no cross-reactivity with apraclonidine. Due to the small series, however, we cannot assume that allergy will not occur with clonidine 0.25% given time and a larger number of patients.

Studies of the distribution of lipofuscin in the retinal pigment epithelium using an enhanced image resolution

SummaryBackground: The fundus autofluorescence imaging technique has been modified allowing improved image resolution (768 × 572 pixel). We present results of fundus autofluorescence studies using this technique. Materials and methods: Fundus autofluorescence was studied in 286 eyes of 143 patients with retinitis pigmentosa, macular dystrophies and age-related macular degeneration using a confocal laser scanning ophthalmoscope prototype (Zeiss, Oberkochen; excitation wavelength: 488 nm, cut-off filter at 521 nm). Results: The spatial distribution of autofluorescence was different in all diseased eyes investigated compared to the normal pattern of fundus autofluorescence. Each disorder showed a specific fundus autofluorescence appearance. Conclusions: The advanced technique of imaging fundus autofluorescence allows detailed studies of the lipofuscin distribution. In vivo analysis of the dynamics of accumulation and degradation of lipofuscin in eyes with tapeto-retinal dystrophies and age-related macular disease may contribute to elucidation of the pathogenesis of these disorders.ZusammenfassungHintergrund: Die Technik zur in vivo-Darstellung der Lipofuszinverteilung im retinalen Pigmentepithel (RPE) wurde so modifiziert, daß eine detailliertere Bildauflösung (768 × 572 Pixel) erreicht wurde. Erste Ergebnisse werden vorgestellt. Patienten und Methoden: Das Verteilungsmuster von Lipofuszin im RPE wurde mit einem konfokalen Scanning Laser Ophthalmoskop-Prototyp (Zeiss, Oberkochen; Exzitationswellenlänge: 488 nm, Leistung: 250 μW, Filter ab 521 nm) an 286 Augen von 143 Patienten mit Retinitis pigmentosa, vererbten Makuladystrophien und altersbedingter Makuladegeneration untersucht. Ergebnisse: Die Fundus-Autofluoreszenz war bei allen untersuchten Augen mit Netzhauterkrankungen im Vergleich zu den Normwerten verändert, jeder untersuchten Netzhauterkrankung konnte ein spezifisches Autofluoreszenzverteilungsmuster zugeordnet werden. Schlußfolgerungen: Die modifizierte Technik zur Bilderfassung der Fundus-Autofluoreszenz ermöglicht Untersuchungen des Lipofuszinverteilungsmusters im RPE in vivo mit bisher unerreichter Bildauflösung. Studien zur Einlagerung und des Abbaus von Lipofuszin in seiner Dynamik bei Patienten mit tapetoretinalen Dystrophien und altersbedingter Makuladegeneration könnten zur Klärung der Pathogenese dieser Erkrankungen beitragen.

A new method for direct detection of heparin on surface-modified intraocular lenses : A modification of Jaques' toluidine blue staining method

BACKGROUND Examination of surface-bound heparin on synthetic polymers can only be performed by few staining methods. These methods are limited by an only approximate detection of heparin visible at high magnification. Other methods only measure heparin quantitatively (per square dimension) and are rather sensitive to artifacts. Due to its homogeneous staining pattern, the modified toluidine blue staining technique, using a non-protein-based substance, allows examination and analysis of the homogeneity of the monomolecular heparin layer even under critical conditions like scanning electron microscopy. MATERIALS AND METHODS For critical examination of the heparin layer, this method was used for 5 sterile heparin surface-modified (HSM) monofocal (Pharmacia, 809C, 5 mm optical zone), 2 multifocal PMMA (Pharmacia, 811E, 6 mm optical zone) and 1 standard PMMA intraocular lenses (IOLs; Pharmacia, 809P, 5 mm optical zone). A special mixture containing a sodium borate buffer was used to avoid cross-reactions of toluidine with phenylimines, which permit a covalent surface linkage of heparin to synthetic polymeric materials via reductive amination. This resulted in less coarse-grained complex agglutination. After light and spectral microscopy of the surface of stained IOLs, scanning electron microscopy was performed to investigated the reliability and validity of this modified staining method. RESULTS All HSM IOLs showed a homogeneous heparin structure and coating, which could be demonstrated even under critical photographic circumstances. CONCLUSIONS The modification of the original toluidine blue staining method introduced by Jaques in 1943 is a reliable and reproducible technique for the detailed in vitro analysis of surface-bound heparin with a low artifact rate. Because of the detailed detection of heparin on polymeric surfaces, this staining method is recommended for special problems, e.g. in cataract surgery.

The incidence of retinal haemorrhages and their implications

We read with interest the paper by Li et al 1 recently published in the British Journal of Ophthalmology . The authors state that “it is an unsupported assumption that disorders of the neonatal fundus, particularly retinal haemorrhages (RH) due to birth trauma, are at best very rare….” It is well known that RHs occur frequently in newborns. Watts et al reviewed recently the literature concerning RH and found 45 studies about …

Pulsgipfelblutvolumen bei gezielter Beeinflussung lokaler Perfusionsparameter

Background Choroidal autoregulation is discussed controversially. The present study was designed to investigate for the effect of standardized manipulation of local perfusion parameters on choroidal hemodynamics in cynomolgus monkey eyes with lasersurgically induced glaucoma (CMG; German abreviation: RA-LHDG). Methods CMG unilaterally received 2-3 laser treatments so as to develop the lasered-eye glaucoma model. Intraocular pressure (IOP; German abreviation: IOD) and Ocular Pulse Amplitude (OPA) were measured and Peak Pulse Blood Volume (PPBV; German abreviation: PGBV) was determined. Results In CMG PPBV was not significantly (sig., p> 0.05) altered in laser-treated eyes - despite a sig. (p 5 mm Hg in laser-treated eyes showed a sig. (p < 0.05) increase in PPBV. Conclusion Unchanged PPBV in laser-treated eyes of CMG and an increase in PPBV in control eyes point at a bilateral autoregulatory compensatory mechanism, which is more manifest in eyes with IOPs in the normal range.