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Biomedical subjects

O Findl

Publications and source records attributed to O Findl.

At least 19 recordsLinked to original sources
PubMed2006

Accommodating intraocular lenses: a critical review of present and future concepts.

BACKGROUND: Significant efforts have been made to develop lens implants or refilling procedures that restore accommodation. Even with monofocal implants, apparent or pseudoaccommodation may provide the patient with substantial though varying spectacle independence. True pseudophakic accommodation with a change of overall refractive power of the eye may be induced either by an anterior shift or a change in curvature of the lens optic. MATERIALS AND METHODS: Passive-shift lenses were designed to move forward under ciliary muscle contraction. This is the only accommodative lens type currently marketed (43E/S by Morcher; 1CU by HumanOptics; AT-45 by Eyeonics). The working principle relies on various hypothetical assumptions regarding the mechanism of natural accommodation. Dual-optic lenses were designed to increase the dioptric impact of optic shift. They consist of a mobile front optic and a stationary rear optic which are interconnected with spring-type haptics. With active-shift lens systems the driving force is provided by repulsing mini-magnets. Lens refilling procedures replace the lens content by an elastic material and provide accommodation by an increase of surface curvature. RESULTS: Findings with passive-shift lenses have been contradictory. While uncorrected reading vision results were initially reported to be favorable with the 1CU, and excellent with the AT-45 lens, distant-corrected near vision did not exceed that with standard monofocal lenses in later studies. Mean axial shift from laser interferometric measurements under stimulation with pilocarpine showed a moderate anterior shift with the 1CU, while the AT-45 paradoxically exhibited a small posterior shift. With the 1CU, the shift-induced accommodative effect was calculated to be less than +0.5 D in most cases, while +1 D was achieved in a single case only. Ranges and standard deviations were very large in relation to the mean values. Under physiological near-point stimulation, however, no shift was seen at all. Prevention of capsule fibrosis by extensive capsule polishing did not enhance the functional performance. Dual optic lenses are under clinical investigation and are reported to provide a significant amount of accommodation. However, possible long-term formation of interlenticular opacifications remains to be excluded. Regarding magnet-driven active-shift lens systems, initial clinical experience has been promising. Prevention of fibrotic capsular contraction is crucial, and it has been effectively counteracted with a special capsular tension ring, or lens fixation technique, together with capsule polishing. Lens refilling has been extensively studied in the laboratory and in primates. Though it offers great potential for fully restoring accommodation, a variety of problems must be solved, such as achieving emmetropia in the relaxed state, adequate response to ciliary muscle contraction, satisfying image quality over the entire range of accommodation and sustained functioning. The key problem, however, is again after-cataract prevention. CONCLUSIONS: As opposed to psychophysical evaluation techniques, laser interferometry measures what shift lenses are designed to provide: axial shift on accommodative effort. While under pilocarpine some movement was recorded, no movement at all was found under near-point stimulation with any of the lenses currently marketed. In contrast, magnetic-driven active-shift lens systems carry the potential of sufficiently topping up apparent accommodation to provide for clinically useful accommodation while using conventional lens designs with proven after-cataract performance. Dual optic implants significantly increase the impact of axial optic shift. The main potential problem, however, is delayed formation of interlenticular regenerates. Lens refilling procedures offer the potential of fully restoring accommodation due to the great impact of increase in surface curvature on refractive lens power. However, various problems remain to be solved before clinical use can be envisaged, above all, again, after-cataract prevention. The concept of passive single-optic shift lenses has failed. Concomitant poor capsular bag performance makes these lenses an unacceptable trade-off. Magnet-assisted systems potentially combine clinically useful accommodation with satisfactory after-cataract performance. Dual optic lenses theoretically offer substantial accommodative potential but may allow for interlenticular after-cataract formation. Lens refilling procedures have the greatest potential for fully restoring natural accommodation, but will again require years of extensive laboratory and animal investigations before they may function in the human eye.

Accommodation, Ocular↗
PubMed2005

Stimulus-driven versus pilocarpine-induced biometric changes in pseudophakic eyes.

PURPOSE: Most trials that study the lens movement of accommodative intraocular lens (IOLs) use pilocarpine to stimulate ciliary muscle contraction. The aim of this study is to assess in vivo whether a more physiologic, stimulus-driven accommodation is comparable to pilocarpine-induced IOL movement. DESIGN: Controlled patient- and examiner-masked clinical trial. PARTICIPANTS: The study population included 38 eyes with accommodative IOL implants (1CU) and a control group of 28 eyes with conventional open-loop IOLs. METHODS: A high-precision biometry technique, partial coherence interferometry, was used to measure IOL position. Anterior chamber depth was measured during physiologic (near point) and pharmacological (pilocarpine 2%) stimulation. In a subgroup of 14 1CU eyes, IOL position was determined repeatedly within 90 minutes after pilocarpine administration. A different subgroup was investigated as to the effect of cyclopentolate on IOL position. Best-corrected distance visual acuity (VA), best-corrected near VA, and distance-corrected near VA (DCNVA) were assessed using logarithm of the minimum angle of resolution charts. MAIN OUTCOME MEASURES: Anterior chamber depth change under pilocarpine and near-point-driven accommodation. RESULTS: Near-point accommodation did not induce movement of either the accommodating 1CU or the control IOLs. Pilocarpine induced a 201+/-0.137-mm anterior movement of the 1CU IOL (P<0.001), compared with no movement within the control IOL groups (P>0.05). There was no significant (P>0.05) difference in DCNVA between the accommodative and open-loop IOLs. No correlation between near point- or pilocarpine-stimulated IOL movement and DCNVA was found. Concerning the time course of movement after pilocarpine administration, most of the 1CU IOLs showed some movement 30 minutes after application. Cyclopentolate-induced ciliary muscle relaxation caused a posterior IOL movement, as compared with the relaxed state, when focusing on a distant target. CONCLUSION: Pilocarpine-induced ciliary muscle contraction seems to overestimate IOL movement relative to a monocular near-driven stimulus. Therefore, concerning IOL movement, pilocarpine may act as a superstimulus and may not adequately simulate daily life performance of accommodative IOLs. However, it may be helpful to evaluate the maximum potential of an accommodating IOL.

Accommodation, Ocular↗
PubMed2005

Effect of trabeculectomy on ocular blood flow.

BACKGROUND/AIM: Current evidence suggests that vascular insufficiencies in the optic nerve head play an important part in the pathogenesis of glaucomatous optic neuropathy. Trabeculectomy is the most common operative procedure for the treatment of medically uncontrolled glaucoma. This study was conducted to investigate whether trabeculectomy may improve ocular haemodynamics. METHODS: 30 patients with primary open angle glaucoma about to undergo trabeculectomy were included in the study. Patients were evaluated before surgery and at 2 and 10 weeks after trabeculectomy. Optic nerve head blood flow (OnhBF) was assessed with scanning laser Doppler flowmetry. Fundus pulsation amplitude (FPA) measurements were obtained with laser interferometry. RESULTS: Because of the decrease in intraocular pressure there was a significant increase in ocular perfusion pressure (OPP) following trabeculectomy (18.5% (SD 12.0%) and 19.0% (17.1%) at 2 and 10 weeks postoperatively; p <0.001). A significant increase in OnhBF was observed after trabeculectomy (11.6% (16.4%) and 16.2% (20.2%) for each postoperative visit, respectively; p <0.001). FPA was also significantly higher compared with baseline values (17.2% (17.3%) and 17.4% (16.3%), respectively; p <0.001). A significant association between the increase in OPP and the increase in OnhBF and FPA was observed 10 weeks after surgery (r = 0.47; p = 0.009, and r = 0.50; p = 0.005, respectively). CONCLUSION: The results of this study suggest that trabeculectomy improves ocular blood flow in patients with chronic open angle glaucoma.

Aged↗
PubMed2005

Advantage of three dimensional animated teaching over traditional surgical videos for teaching ophthalmic surgery: a randomised study.

BACKGROUND/AIM: Owing to the complex topographical aspects of ophthalmic surgery, teaching with conventional surgical videos has led to a poor understanding among medical students. A novel multimedia three dimensional (3D) computer animated program, called "Ophthalmic Operation Vienna" has been developed, where surgical videos are accompanied by 3D animated sequences of all surgical steps for five operations. The aim of the study was to assess the effect of 3D animations on the understanding of cataract and glaucoma surgery among medical students. METHOD: Set in the Medical University of Vienna, Department of Ophthalmology, 172 students were randomised into two groups: a 3D group (n=90), that saw the 3D animations and video sequences, and a control group (n=82), that saw only the surgical videos. The narrated text was identical for both groups. After the presentation, students were questioned and tested using multiple choice questions. RESULTS: Students in the 3D group found the interactive multimedia teaching methods to be a valuable supplement to the conventional surgical videos. The 3D group outperformed the control group not only in topographical understanding by 16% (p<0.0001), but also in theoretical understanding by 7% (p<0.003). Women in the 3D group gained most by 19% over the control group (p<0.0001). CONCLUSIONS: The use of 3D animations lead to a better understanding of difficult surgical topics among medical students, especially for female users. Gender related benefits of using multimedia should be further explored.

Cataract Extraction↗
PubMed2004

Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects.

AIMS/BACKGROUND: To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. METHODS: The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. RESULTS: None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. CONCLUSIONS: These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency.

Adult↗
PubMed2003

Interventions for normal tension glaucoma.

BACKGROUND: Normal tension glaucoma is a clinical condition in which the optic nerve is pathologically excavated and the visual field is disturbed. Nevertheless it has been assumed that intraocular pressure plays a role in the progression of visual field defects in this disease, but other, mainly vascular factors, have been discussed as well. OBJECTIVES: The objective of this review is to assess the effects of medical and surgical treatments for normal tension glaucoma. SEARCH STRATEGY: Trials were identified from the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group trials register), MEDLINE, EMBASE and BIOSIS Previews. Bibliographies of identified trials were searched to find additional trials. In addition, investigators and pharmaceutical companies were contacted. Date of last search: January 2001. SELECTION CRITERIA: This review includes randomised controlled trials in which medical or surgical interventions were compared to no treatment, placebo or other treatment in people with normal tension glaucoma. Two reviewers independently assessed the full text copies of the possibly relevant trials. Trial quality was assessed according to the methods set out in Section 6 of the Cochrane Reviewers' Handbook (Clarke 2000). DATA COLLECTION AND ANALYSIS: Data were extracted by two reviewers and results were compared for differences. Discrepancies were resolved by discussion. The heterogeneity of interventions, follow-up periods and outcomes did not allow for statistical combinations of the study results. MAIN RESULTS: According to the selection criteria on visual field loss, eight studies were included in this review. Only three studies focussed on patient relevant outcomes. In one trial a beneficial effect of lowering intraocular pressure was found, but only if data were corrected for cataract development. In two small studies a beneficial effect on visual field loss of brovincamine, a calcium antagonist was reported. REVIEWER'S CONCLUSIONS: In one study the effect of intraocular pressure lowering on visual field outcome was only significant when data were corrected for cataract development. The results for calcium antagonists are promising, but larger trials have to be performed. Studies that focussed on reduction of intraocular pressure or haemodynamic variables are not necessarily relevant for the outcome in people with normal tension glaucoma.

Antihypertensive Agents↗
PubMed2003

Choroidal blood flow and arterial blood pressure.

PURPOSE: Untreated hypertension is associated with ocular complications and is a risk factor for the development and progression of vascular ocular pathologies. We set out to investigate the association between systemic blood pressure and choroidal blood flow. METHODS: All subjects were male non-smokers, who did not receive any medication and had normal or slightly elevated blood pressure (systolic blood pressure < or = 160 mmHg; diastolic blood pressure < or = 100 mmHg). The association between systemic blood pressure and fundus pulsation amplitude, a measure of pulsatile choroidal blood flow, was investigated in 318 volunteers. In addition, the association between systemic blood pressure and blood flow velocities in the posterior ciliary arteries supplying the choroid was investigated in these subjects. RESULTS: Ocular fundus pulsation amplitude (r = 0.252; P < 0.001) and mean flow velocity in the posterior ciliary arteries (r = 0.346, P < 0.001) were significantly associated with mean arterial pressure. The correlation of ocular haemodynamic variables with systolic and diastolic blood pressure was in the same range. CONCLUSIONS: Our data indicate a small, but significant increase in choroidal blood flow with increasing blood pressure.

Adult↗
PubMed2001

Ocular hemodynamics during isometric exercise.

The autoregulatory capacity of the human retina is well documented, but the pressure-flow relationship of the human choroid is still a matter of controversy. Recent data, using laser Doppler flowmetry to measure choroidal blood flow, indicate that the choroid has some autoregulatory potential, whereas most data using other techniques for the assessment of choroidal hemodynamics indicate that the choroidal pressure-flow curve is linear. We used a new laser interferometric technique to characterize choroidal blood flow during isometric exercise. Twenty healthy subjects performed squatting for 6 min during normocapnia and during inhalation of 5% CO2 and 95% air. Ocular fundus pulsation amplitude, flow velocities in the ophthalmic artery, intraocular pressure, and systemic hemodynamics were measured in 2-min intervals. To gain information on choroidal blood flow fundus pulsation amplitude was corrected for changes in flow pulsatility using data from the ophthalmic artery and for changes in pulse rate. Ocular perfusion pressure was calculated from mean arterial pressure and intraocular pressure. The ocular pressure-flow relationship was calculated by sorting data according to ascending ocular perfusion pressure values. In a pilot study in 6 healthy subjects comparable ocular pressure flow relationships were obtained when choroidal blood flow was assessed with the method described above and with laser Doppler flowmetry. In the main study isometric exercise caused a significant increase in mean arterial pressure (56%, P < 0.001), pulse rate (84%, P < 0.001), and intraocular pressure (37%, P 0.004), but decreased fundus pulsation amplitude (-36%, P < 0.001). Significant deviations from baseline choroidal blood flow were observed only at ocular perfusion pressures >69% during normocapnia and 70% during hypercapnia. Our data indicate that during isometric exercise the choroid has a high capacity to keep blood flow constant despite changes in perfusion pressure and that this pressure-flow relationship is not altered by moderate changes in arterial carbon dioxide levels.

Adult↗
PubMed2001

Morphological appearance and size of contact zones of piggyback intraocular lenses.

PURPOSE: To characterize the morphology, size, and change in size of the contact zone of piggyback intraocular lenses (IOLs) of different materials and optic designs. SETTING: Department of Ophthalmology, Vienna General Hospital, Vienna, Austria. METHODS: In a prospective study, 9 eyes of 7 patients received piggyback IOLs of the following materials: poly(methyl methacrylate) (PMMA), acrylic, hydrogel, and silicone. The contact zone between the anterior and posterior IOLs was photodocumented from 1 day to 1 year after surgery using specular microscopy. The contact zone area was measured. RESULTS: A contact zone was present with all IOL materials studied. The area of contact, however, differed significantly. With PMMA IOLs, the contact zone was small and surrounded by Newton rings, indicating the tiny gap between the IOLs. With IOLs of soft material, such as silicone and hydrogel, it was larger than with PMMA IOLs and had a slightly irregular shape. With foldable acrylic IOLs, it was regular, round, and slightly larger than with the soft materials. The contact area enlarged primarily during the first 3 months after surgery. After 1 year, 2 eyes with acrylic piggyback IOLs had a membrane formation around the contact zone and 2 eyes developed Elschnig pearls between the IOLs. CONCLUSION: In piggyback IOL eyes, the shape and size of the contact zone were strongly dependent on the IOL material and optic design. Contact area enlargement seemed to be induced by capsule shrinkage. Fibrous membrane formation around the contact zone and Elschnig pearl formation between the piggyback IOLs were long-term complications of this technique.

Acrylates↗
PubMed2001

Improved prediction of intraocular lens power using partial coherence interferometry.

PURPOSE: To evaluate the feasibility of using a new optical biometry technique, dual-beam partial coherence interferometry (PCI), to improve intraocular lens (IOL) power prediction in cataract surgery. SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Vienna, Austria. METHODS: Preoperative axial length (AL) data obtained with PCI biometry and applanation ultrasound (US) biometry in 77 eyes of 51 patients was applied to 4 commonly used IOL power formulas. The refractive outcome and the mean absolute error (MAE) were calculated for each formula using both biometry methods. A linear multiple-regression model based on preoperative PCI biometry data was derived to predict the postoperative anterior chamber depth (ACD). The predictive power of this regression model was assessed by adding the predicted ACD to the SRK/T formula. Predicted residuals were calculated to evaluate the feasibility and stability of this modified IOL power formula. RESULTS: Using PCI instead of US biometry significantly improved the refractive outcome with all 4 IOL power formulas. The Holladay I and SRK/T formulas yielded an MAE of 0.44 diopter (D) using PCI AL data and 0.56 D and 0.57 D, respectively, using US biometry data. The SRK/T formula combined with the PCI regression model for postoperative ACD prediction performed slightly better (MAE 0.42 D) than the conventional SRK/T formula alone. Predicted residuals revealed an MAE of 0.46 D, proving the predictive performance of the new formula. CONCLUSIONS: Partial coherence interferometry biometry applied to several widely used IOL power formulas yielded significantly better IOL power prediction and therefore refractive outcome in cataract surgery than US biometry. Further improvement can be achieved by applying PCI to a modified SRK/T formula that predicts the postoperative ACD using PCI biometry data.

Biometry↗
PubMed2001

Intraindividual comparison of the effects of a fixed dorzolamide-timolol combination and latanoprost on intraocular pressure after small incision cataract surgery.

To compare the effect of a fixed dorzolamide-timolol combination with that of latanoprost on intraocular pressure (IOP) after small incision cataract surgery. Department of Ophthalmology, University of Vienna, Vienna, Austria. This prospective randomized study comprised 60 eyes of 30 patients scheduled for small incision cataract surgery in both eyes. The patients were randomly assigned to receive 1 drop of a fixed dorzolamide-timolol combination or latanoprost immediately after cataract surgery in the first eye. The second eye received the other antiglaucomatous agent. Cataract surgery was performed under sodium hyaluronate 1% with a temporal 3.5 mm sutureless posterior limbal incision, phacoemulsification, and implantation of a foldable intraocular lens. The IOP was measured preoperatively as well as 6 and 20 to 24 hours and 1 week postoperatively. Six hours after surgery, the mean IOP decreased by -0.8 mm Hg +/- 3.2 (SD) (P =.184) in the dorzolamide-timolol group and increased by 3.6 mm Hg +/- 3.5 (P <.001) in the latanoprost group. Twenty to 24 hours after surgery, the mean IOP decreased by -2.8 +/- 2.4 mm Hg (P <.001) in the dorzolamide-timolol group and increased by 0.6 +/- 3.5 mm Hg (P =.353) in the latanoprost group. The differences between groups were significant at 6 hours (P <.001) and 20 to 24 hours (P <.001). The fixed dorzolamide-timolol combination was more effective than latanoprost in reducing IOP after small incision cataract surgery. Only the fixed dorzolamide-timolol combination prevented a postoperative IOP increase and occasional IOP spikes of 30 mm Hg or higher.

Antihypertensive Agents↗
PubMed2001

Posterior continuous curvilinear capsulorhexis with hydrogel and silicone intraocular lens implantation: development of capsulorhexis size and capsule opacification.

PURPOSE: To evaluate the influence of primary posterior continuous curvilinear capsulorhexis (PCCC) on capsule opacification development and capsular bag changes within the first year after cataract surgery with 2 intraocular lenses (IOLs) of comparable design but different material. SETTING: Department of Ophthalmology, University of Vienna, Medical School, Vienna, Austria. METHODS: Thirty-seven patients with age-related cataract had bilateral small incision cataract surgery with a PCCC performed after capsular tension ring insertion. One eye was randomly assigned to receive a hydrogel IOL and the other eye, a silicone IOL. Standardized digital retroillumination photographs were taken 1 day, 1 week, and 1, 3, 6, and 12 months after surgery to evaluate changes in the dimensions of the anterior and posterior capsulorhexis opening area and the presence of anterior and posterior capsule opacification. RESULTS: The area of the anterior continuous curvilinear capsulorhexis (ACCC) opening was significantly reduced during the first 6 postoperative months. The shrinkage was more pronounced (-25%) in the silicone IOL group than in the hydrogel IOL group. Ten percent of eyes with a silicone IOL had marked shrinkage of the ACCC. The area of the PCCC did not change in eyes with a hydrogel IOL but was larger (+20%) in eyes with a silicone IOL. Anterior ongrowth was observed in 60% in the hydrogel group and in no eye in the silicone group. Anterior capsule fibrosis was observed in 90% in the silicone group and in 20% in the hydrogel group. Total closure of the PCCC was not observed within the first year, but posterior ongrowth was observed in 40% in the hydrogel group and 10% in the silicone group. CONCLUSIONS: Anterior capsulorhexis shrinkage with concomitant posterior capsulorhexis enlargement was observed in eyes with a silicone IOL. The hydrogel IOL induced more ongrowth on the anterior and posterior IOL surfaces, whereas the silicone IOL induced more anterior capsule fibrosis. Total closure of the PCCC was not observed within the first year after surgery.

Aged↗
PubMed2001

Effect of topical brimonidine on intraocular pressure after small incision cataract surgery.

PURPOSE: To evaluate the effect of brimonidine 0.2% on intraocular pressure (IOP) after small incision cataract surgery. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: This prospective randomized study comprised 80 eyes of 40 patients scheduled for small incision cataract surgery in both eyes. In each patient, 1 eye was randomly assigned to receive 1 drop of brimonidine 0.2% or no treatment (control) immediately after surgery. The fellow eye received the other assigned treatment. All patients had standardized surgery by the same surgeon with sodium hyaluronate 1%, a temporal 3.5 mm sutureless posterior limbal incision, phacoemulsification, and implantation of a foldable intraocular lens. The IOP was measured preoperatively as well as 6 and 20 to 24 hours and 1 week postoperatively. RESULTS: Six hours after surgery, the mean increase in IOP was 4.7 mm Hg +/- 6.1 (SD) in the brimonidine group and 4.6 +/- 5.3 mm Hg in the control group. In each group, 17 eyes (43%) had an IOP increase of 5 mm Hg or more. Twenty to 24 hours after surgery, the mean increase in IOP was 1.5 +/- 4.2 mm Hg in the brimonidine group and 1.6 +/- 4.4 mm Hg in the control group. There were no statistically significant between-group differences at any measurement. CONCLUSIONS: In both groups, IOP significantly increased 6 hours and 20 to 24 hours after small incision cataract surgery. Brimonidine 0.2% failed to reduce the IOP increase observed after small incision cataract surgery.

Administration, Topical↗
PubMed2001

A double masked placebo controlled study on the effect of nifedipine on optic nerve blood flow and visual field function in patients with open angle glaucoma.

AIMS: To investigate whether nifedipine affects ocular perfusion or visual fields in open angle glaucoma patients. METHODS: In a parallel group study nifedipine or placebo was administered for 3 months (n = 30). Ocular fundus pulsation amplitude (FPA), cup blood flow (Flowcup) and visual field mean deviation (MD) were measured. RESULTS: Five patients receiving nifedipine discontinued due to adverse events. Nifedipine did not affect FPA [difference: 0.3 microm (95% CI -0.3,0.9); P = 0.70], Flowcup: [difference: -9 rel.units (95% CI -133,114); P = 0.99], or MD [difference: 0.2dB (95% CI -2.2,2.7); P = 0.51] vs placebo. CONCLUSIONS: Systemic nifedipine is not well tolerated in glaucoma patients and exerts no effect on visual fields or ocular perfusion.

Administration, Oral↗
PubMed2001

Intraocular pressure rise after small incision cataract surgery: a randomised intraindividual comparison of two dispersive viscoelastic agents.

AIM: To evaluate the effects of the dispersive viscoelastic agents Ocucoat (hydroxypropyl methylcellulose 2%) and Viscoat (sodium chondroitin sulphate 4%-sodium hyaluronate 3%) on postoperative intraocular pressure (IOP) after bilateral small incision cataract surgery. METHODS: This prospective, randomised study comprised 80 eyes of 40 consecutive patients with age related cataract in both eyes scheduled for bilateral small incision cataract surgery. The patients were randomly assigned to receive Ocucoat or Viscoat during cataract surgery of the first eye. The second eye was operated later and received the other viscoelastic agent. Cataract surgery was performed with a temporal 3.2 mm sutureless posterior limbal incision, phacoemulsification, and implantation of a foldable silicone intraocular lens. The IOP was measured preoperatively as well as 6 hours, 20-24 hours, and 1 week postoperatively. RESULTS: At 6 hours after surgery the mean IOP increased by 4.6 (SD 5.1) mm Hg in the Ocucoat group (p<0.001) and by 8.6 (8.1) mm Hg in the Viscoat group (p<0.001). The increase was significantly higher in the Viscoat group than in the Ocucoat group (p=0.004). Intraocular pressure spikes of 30 mm Hg or more occurred in two eyes in the Ocucoat and in nine eyes in the Viscoat group (p=0.023); 20-24 hours and 1 week postoperatively the mean IOP was not statistically different. CONCLUSION: These findings indicate that Viscoat causes a significantly higher IOP increase and significantly more IOP spikes than Ocucoat in the early period after small incision cataract surgery.

Aged↗
PubMed2001

Effect of endothelin and BQ123 on ocular blood flow parameters in healthy subjects.

PURPOSE: To characterize the role of the endothelin system in the blood flow control of the optic nerve head and of the choroid in humans. METHODS: Two studies were performed in healthy subjects. Study 1 was a randomized, placebo-controlled, double-masked, balanced, two-way crossover design and study 2 a three way-way crossover design. In study 1 twelve healthy male subjects received endothelin (ET)-1 in stepwise increasing doses of 1.25, 2.5, and 5 ng/kg x min (each infusion step occurred over 20 minutes) coinfused with BQ123 (60 microg/kg x min) or placebo on two different study days. In study 2 twelve healthy male subjects received two doses of BQ123 (60 or 120 microg/kg x min over 60 minutes) or placebo on three different study days. Measurements of optic nerve head blood flow (ONHBF) and choroidal blood flow (ChBF) were performed with laser Doppler flowmetry in both studies. In study 2 mean flow velocity (MFV) of the ophthalmic artery was assessed with Doppler sonography. RESULTS: In study 1, ET-1 significantly decreased ONHBF (-22.8% +/- 4.3% at 5 ng/kg x min, P = 0.003 versus baseline) and ChBF (-21.7% +/- 3.2% at 5 ng/kg x min, P = 0.0001 versus baseline). The effect of the highest administered dose of exogenous ET-1 on ONHBF was significantly attenuated (P = 0.04, ANOVA) by coinfusion of BQ123. Effects of exogenous ET-1 on blood flow (2.5 ng/kg x min ET-1 or higher) also were attenuated in the choroid by coinfusion of BQ123 (ChBF: P = 0.03, ANOVA). In study 2, both dosages of BQ123 significantly increased MFV in the ophthalmic artery (60 microg/kg x min, 12.5% +/- 7.3%; 120 microg/kg x min, 17.2% +/- 9.2%, versus baseline; P = 0.001), but did not change blood flow in the ONH or the choroid. CONCLUSIONS: BQ123 antagonizes the effects of exogenously administered ET-1 on blood flow in the ONH and the choroid. The data indicate, however, that ET-1 does not substantially contribute to the regulation of basal vascular tone in these tissues.

Adult↗
PubMed2000

Effects of insulin on retinal and pulsatile choroidal blood flow in humans.

BACKGROUND: Insulin induces vasodilation in several tissues, including skeletal muscle and kidneys. OBJECTIVE: To investigate whether insulin may contribute to ocular blood flow regulation. METHODS: The study was performed in a balanced, randomized, placebo-controlled, single-masked, 3-way, crossover design in 9 healthy male subjects. Each subject received 2 doses of insulin (1.5 or 3 mU/kg per minute) or placebo on 3 different study days. Measurements of fundus pulsation amplitude with laser interferometry to assess pulsatile choroidal blood flow, of retinal blood flow with the blue-field entoptic technique, and of mean blood flow velocity in the ophthalmic artery with Doppler sonography were performed under euglycemic clamp conditions over 120 minutes. RESULTS: Hyperinsulinemia significantly increased fundus pulsation amplitude (1.5 mU/kg per minute: 8.7% +/- 1.1% vs baseline; 3 mU/kg per minute: 13.2% +/- 2.3% vs baseline; P<.001 vs placebo [analysis of variance]) and mean blood flow velocity (1.5 mU/kg per minute: 10.0% +/- 4.3% vs baseline; 3 mU/kg per minute: 6.6% +/- 3.5% vs baseline; P = .03 vs placebo). Retinal blood flow did not increase during administration of insulin (1.5 mU/kg per minute: 6.4% +/- 8.0% vs baseline; 3 mU/kg per minute: 8.0% +/- 5.1% vs baseline; P = .99 vs placebo). Neither the effect in the choroid nor that in the ophthalmic artery was dose-dependent. CONCLUSION: Hyperinsulinemia significantly increases choroidal blood flow and mean blood flow velocity in the ophthalmic artery. By contrast, retinal blood flow was not influenced by hyperinsulinemia. The maximum effective dose of insulin for ocular hemodynamics is likely to be within the physiological range.

Adult↗