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Biomedical subjects

P A Netland

Publications and source records attributed to P A Netland.

At least 37 records · Page 2Linked to original sources
PubMed1997

Magnetic resonance imaging of cyclodialysis clefts.

BACKGROUND: Our purpose was to determine whether cyclodialysis clefts can be imaged with magnetic resonance imaging (MRI). METHODS: Surgical cyclodialysis clefts extending approximately 3 clock hours were created in four New Zealand white rabbits. Eyes were scanned with an ocular MRI coil. Images obtained after intravenous gadolinium, topical godalinium, and gadolinium injected into the cleft were compared to images obtained without contrast. Two human eyes were also scanned for cyclodialysis clefts with MRI. RESULTS: Direct injection of gadolinium into the suprachoroid space yielded definitive localization and delineation of the cyclodialysis cleft. Cyclodialysis clefts could also be imaged following enhancement with topical or intravenous gadolinium. Without contrast medium, the clefts could not be clearly identified in rabbits. In a patient with hypotony and choroidal effusion following cataract surgery, a cyclodialysis cleft and enhancement of the suprachoroidal space were found with intravenous administration of gadolinium. MRI from a patient with a trabeculo-suprachoroidal shunt also demonstrated gadolinium enhancement of the suprachoroidal space. CONCLUSION: Cyclodialysis clefts can be imaged using gadolinium-enhanced MRI in rabbits and humans.

Aged↗
PubMed1997

Cardiovascular effects of topical carteolol hydrochloride and timolol maleate in patients with ocular hypertension and primary open-angle glaucoma. Night Study Group.

PURPOSE: To compare the effects of topical timolol maleate 0.5% and carteolol hydrochloride 1% on pulse rate and blood pressure. METHODS: In a randomized, double-masked, parallel-design, multicenter clinical trial, we compared the effects of timolol and carteolol on pulse rate and blood pressure measured by 24-hour ambulatory blood pressure monitoring in 169 adult patients with either ocular hypertension or primary open-angle glaucoma. RESULTS: From noon to 8 PM, baseline mean pulse rate of 82 to 83 beats per minute (bpm) had decreased by 4 to 6 bpm in both groups after 4 weeks of therapy with timolol or carteolol. From midnight to 4 AM, the pulse rate in the carteolol group was significantly above baseline (P = .005), while the timolol group was significantly below baseline (P < .001). Four times as many patients became bradycardic (heart rate, < 60 bpm) on timolol (18.4%) as did patients on carteolol (4.5%) from midnight to 4 AM. More than twice as many patients exhibited a resolution of their bradycardia with carteolol (46.7%) as did patients treated with timolol (18.2%) from midnight to 4 AM. Overall cardiovascular adverse effects were reported significantly more frequently in the timolol than the carteolol group (P = .002). CONCLUSIONS: Timolol causes significantly lower mean heart rate during the nighttime and more nocturnal bradycardia than carteolol does in patients with ocular hypertension and primary open-angle glaucoma. These differences may be because of the intrinsic sympathomimetic activity of carteolol.

Administration, Topical↗
PubMed1997

Efficacy of carteolol hydrochloride 1% vs timolol maleate 0.5% in patients with increased intraocular pressure. Nocturnal Investigation of Glaucoma Hemodynamics Trial Study Group.

PURPOSE: To evaluate the ocular hypotensive effect and safety of carteolol hydrochloride 1% vs timolol maleate 0.5%. METHODS: One hundred seventy-six patients with ocular hypertension or primary open-angle glaucoma were randomly assigned to receive either carteolol 1% twice a day or timolol maleate 0.5% solution twice a day in a randomized, double-masked, multicenter, parallel-group, active-control comparison trial during a 3-month period. RESULTS: After 12 weeks, carteolol 1% reduced the mean +/- SE intraocular pressure from 25.0 +/- 0.3 to 19.5 +/- 0.3 mm Hg; timolol maleate 0.5% reduced the mean intraocular pressure from 25.2 +/- 0.3 to 19.6 +/- 0.3 mm Hg. The mean difference in trough intraocular pressure between carteolol and timolol maleate of -0.14 mm Hg was not significantly (P = .745) different (95% confidence limits, -0.97 to 0.70 mm Hg). Trough pulse and blood pressure also showed no consistent statistically significant differences between groups. The 2-hour postdose pulse, however, demonstrated a greater decrease in the timolol maleate than in the carteolol group (P < .001). Systemic and ocular signs and symptoms were similar between the groups except that the number of treatment-emergent reports of bradycardia was greater in the timolol maleate group (P = .039), and the carteolol group reported fewer ocular symptoms than the timolol maleate group did (P < .01). CONCLUSIONS: Both carteolol 1% and timolol maleate 0.5% are highly effective in lowering intraocular pressure when measured at the end of the dosing interval. Carteolol 1% demonstrates an ocular hypotensive effect and safety profile similar to those of timolol maleate 0.5% solution.

Adolescent↗
PubMed1997

Diode laser-pumped, frequency-doubled neodymium: YAG laser peripheral iridotomy.

BACKGROUND AND OBJECTIVE: The solid-state, continuous-wave, frequency-doubled neodymium: yttrrium-aluminum-garnet (Nd:YAG) laser pumped by a diode laser has several advantages, including air cooling, higher electrical to optical efficiency ratios, portability, and the use of standard 110-V AC electrical service. The authors wanted to evaluate the use of the frequency-doubled Nd:YAG laser for peripheral iridotomy and to compare the tissue interactions of this laser with those of the argon laser. MATERIAL AND METHODS: The authors developed a diode laser-pumped, solid-state, and portable frequency-doubled Nd:YAG laser with a wavelength of 532 nm. The effects of peripheral iridotomy with the frequency-doubled Nd:YAG laser and the argon laser were evaluated in pig eyes in vitro and in rabbit eyes in vivo. Specimens were prepared for light microscopy and scanning electron microscopy. RESULTS: The frequency-doubled Nd:YAG laser successfully created patent iridotomies in all animal eyes treated. The following parameters were used to create penetrating burns: duration of 0.1 second, spot size of 100 microns, and power of 500 mW. In rabbit eyes, the mean number of pulses (P = .16) and the total energy required (P = .21) for iridotomy were not significantly different for the argon laser compared with the frequency-doubled Nd:YAG laser. Gross and histologic evaluation showed similar thermal effects in iris tissues for both the frequency-doubled Nd:YAG laser and the argon laser. The mean zone of thermal damage was 178 +/- 19 microns for the frequency-doubled Nd:YAG laser and 163 +/- 24 microns for the argon laser (P = .14). Scanning electron microscopy showed less disruption of the surface of the lesion for the frequency-doubled Nd:YAG laser compared with the argon laser. CONCLUSIONS: Successful peripheral iridotomy can be performed with the frequency-doubled Nd:YAG laser. Coagulative effects with the frequency-doubled Nd:YAG were similar to those with the argon laser, and the thermal damage zones were comparable in size.

Animals↗
PubMed1997

Color Doppler ultrasound measurements after topical and retrobulbar epinephrine in primate eyes.

PURPOSE: To determine the effects of topical epinephrine and retrobulbar anesthesia containing lidocaine with epinephrine on retrobulbar hemodynamic measurements in the primate eye, using color Doppler ultrasound. METHODS: Color Doppler ultrasound measurements were performed at baseline and 90 minutes after masked administration of topical 2% epinephrine or balanced salt solution to six cynomolgus monkeys. Measurements were also performed at baseline and 30 minutes after retrobulbar injection of 2% lidocaine, with or without 1:200,000 epinephrine. RESULTS: After topical epinephrine, color Doppler ultrasound measurements were not significantly different compared with baseline measurements in the central retinal artery, posterior ciliary arteries, and superior ophthalmic vein. There were decreased systolic and diastolic velocities in the ophthalmic artery (P < 0.03 and P < 0.02, respectively) after topical epinephrine; however, Pourcelot's ratio (resistive index) was not significantly different compared with that at baseline. In contrast, there were marked changes in the retrobulbar arterial circulation after retrobulbar injection of lidocaine with epinephrine. The systolic and diastolic velocities were decreased significantly in the central retinal artery (P < 0.02 and P < 0.01, respectively), temporal posterior ciliary artery (P < 0.05 and P < 0.03, respectively), and nasal posterior ciliary artery (P < 0.03 and P < 0.02, respectively). Pourcelot's ratio was significantly increased in the central retinal artery (P < 0.01), temporal posterior ciliary artery (P < 0.02), and nasal posterior ciliary artery (P < 0.02) after retrobulbar injection of lidocaine with epinephrine. CONCLUSIONS: These results indicate that one drop of topical epinephrine has little or no effect on the retrobulbar circulation, whereas retrobulbar injection of anesthetic solution containing lidocaine with epinephrine significantly alters retrobulbar hemodynamics in the monkey eye.

Administration, Topical↗
PubMed1996

Optic disc hemorrhages and progression of glaucoma.

PURPOSE: To assess progressive changes of the optic nerve head and visual fields in patients with glaucoma and ocular hypertension after optic disc hemorrhage. METHODS: The authors reviewed the charts of 91 patients with 121 disc hemorrhages who had a mean follow-up of 41.9 +/- 3.6 months. The frequency of visual field and optic nerve head changes in these patients was studied. RESULTS: The mean intraocular pressure at the examination when the disc hemorrhage was noted was 18.9 +/- 0.5 mmHg. Overall, 64 (63%) of 101 eyes showed progressive changes of visual fields after disc hemorrhage, compared with 24 (24%) of 101 control eyes (P < 0.0005). Similarly, 56 (79%) of 71 eyes showed progressive changes of optic nerve head contour by masked evaluation of stereophotographs, compared with 16 (22%) of 71 control eyes (P < 0.0005). Eyes with disc hemorrhage showed significantly greater progression of visual field defects in patients with open-angle glaucoma (P < 0.001), low-tension glaucoma (P < 0.05), and ocular hypertension (P = 0.0067) compared with control eyes matched by age, follow-up time, and diagnosis. Similarly, progressive changes of optic nerve head contour were observed more often in eyes after disc hemorrhage in patients with open-angle glaucoma (P < 0.0005), low-tension glaucoma (P < 0.025), and ocular hypertension (P < 0.005), compared with controls. The mean time interval to progression after disc hemorrhage was observed was 16.8 +/- 2.0 months for visual field changes and 23.8 +/- 2.9 months for optic nerve head changes. In eyes with disc hemorrhage, 27 (22%) of 121 had recurrent hemorrhages at a mean interval of 21.5 +/- 2.9 months after previous hemorrhage. The most common site of disc hemorrhage was the inferotemporal quadrant. Eyes with disc hemorrhage that occurred on the temporal side of the optic nerve head had a significantly lower intraocular pressure (P < 0.02) and greater progressive changes of the optic discs (P < 0.001) compared with eyes with hemorrhage on the nasal side. CONCLUSION: The authors' results indicate that disc hemorrhages in eyes with glaucoma or ocular hypertension often are associated with progressive changes of the optic nerve head and visual fields.

Adult↗
PubMed1996

Optic nerve head circulation after topical calcium channel blocker.

PURPOSE: Our purpose was to investigate the effects of the calcium channel blocker verapamil on intraocular pressure and blood circulation in the human optic nerve head. METHODS: The effects of three different concentrations of topical verapamil (0.063%, 0.125%, and 0.25%) on intraocular pressure and optic nerve head capillary blood speed were measured in 12 healthy normal subjects. In a randomized, double-masked design, each subject received one drop of either verapamil or placebo in one eye and the opposite treatment in the fellow eye. Anterior optic nerve circulation was assessed at baseline and 90 min after instillation of the drops using the laser Doppler technique. RESULTS: The intraocular pressure was significantly reduced compared with baseline in both verapamil- and placebo-treated eyes at each concentration. The reductions of intraocular pressure were greater in verapamil-treated eyes (12-17%) than in placebo-treated eyes (9-12%). No systemic effect on heart rate or blood pressure was detected after administration of topical verapamil. The capillary blood speed in the optic nerve head was increased in both verapamil- and placebo-treated eyes at each concentration, although the only statistically significant increases were with the 0.25% concentration. The mean +/- SEM increase compared with baseline at the 0.25% concentration was 10.4 +/- 3.6% in verapamil-treated eyes (p = 0.017), and 11.6 +/- 4.4% in placebo-treated eyes (p = 0.026). CONCLUSIONS: These results indicate that topical administration of verapamil lowers the intraocular pressure and increases the capillary blood speed in the optic nerve head in normal subjects. Changes measured in verapamil-treated eyes were also observed in placebo-treated eyes, indicating a crossover effect.

Administration, Topical↗
PubMed1995

Assessment of intraocular pressure by palpation.

PURPOSE/METHODS: Corneal specialists may assess the intraocular pressure by palpation although this technique has never been validated. We explored the reliability of a tactile assessment of the intraocular pressure in comparison to Goldmann tonometry. RESULTS/CONCLUSION: There was little correlation between tactile assessment of the intraocular pressure and tonometry. However, palpation was moderately successful in identifying most eyes (five of seven eyes) with an intraocular pressure greater than 30 mm Hg. Although palpation was generally inaccurate, it may serve as a warning for marked increases in intraocular pressure exceeding 30 mm Hg.

Humans↗
PubMed1995

Color Doppler ultrasound analysis of ocular circulation after topical calcium channel blocker.

PURPOSE: To investigate the effect of topical administration of the calcium channel blocker verapamil on intraocular pressure and retrobulbar hemodynamics. METHODS: In this randomized, prospective, double-masked study, we examined the effects of single-dose topical administration of verapamil in ten normal human volunteers by using color Doppler ultrasound imaging to measure hemodynamic parameters. Limitations of this study include single-dose application of verapamil and relatively small sample size. RESULTS: No systemic effect on heart rate or blood pressure was detected after administration of topical verapamil. The intraocular pressure significantly decreased compared with baseline two hours after topical 0.125% and 0.25% verapamil (P = .015 and .040, respectively). Pourcelot's ratio, an index of vascular resistance, measured in the central retinal artery was significantly reduced after topical application of 0.125% verapamil (P = .008). The change in Pourcelot's ratio primarily resulted from an increased end diastolic velocity in the central retinal artery. No significant differences compared with baseline values were detected in the color Doppler ultrasound measurements of the posterior ciliary arteries and the central retinal vein two hours after topically administered verapamil. CONCLUSIONS: Topical administration of verapamil decreases intraocular pressure and alters ocular hemodynamics, reducing the vascular resistance index in the central retinal artery.

Administration, Topical↗
PubMed1995

Verapamil increases outflow facility in the human eye.

Verapamil, a calcium channel antagonist, causes a reduction of intraocular pressure in humans. This study investigated whether verapamil's effect on intraocular pressure was related to increased outflow facility. Six pairs of human eyes were dissected and anterior segments were perfused under constant pressure with concentrations of verapamil HCl ranging from 10(-10)-10(-3) M. The maximal increase of outflow facility over baseline was 64% at 10(-9) M. These results indicate that verapamil causes a dose related increase in outflow facility in human eyes, which may account for the reduced intraocular pressure following topical administration of verapamil.

Aged↗
PubMed1995

Clinical experience with the Baerveldt glaucoma drainage implant.

PURPOSE: To assess clinical outcomes in patients who were treated with the Baerveldt glaucoma drainage implant. METHODS: The authors performed a retrospective multicenter study of 100 patients (103 eyes) with medically uncontrollable glaucomas who underwent a one-stage implantation with either the 200-, 250-, 350-, or 500-mm2 Baerveldt implant. The authors defined surgical success as 5 mmHg less than intraocular pressure less than 22 mmHg without additional glaucoma surgery and without loss of light perception. RESULTS: With a mean follow-up of 13.6 +/- 0.9 months (range, 4-37 months), 74 eyes (71.8%) had successful outcomes. Cumulative life-table success rates were 90.3% at 3 months (n = 103), 72.6% at 6 months (n = 84), and 60.3% at 24 months (n = 34). Intraocular pressure (IOP) was reduced from a mean of 38.5 +/- 1.4 mmHg with 2.2 +/- 0.1 antiglaucoma medications to 15.1 +/- 0.8 mmHg (P < 0.0005) with 0.5 +/- 0.1 antiglaucoma medications (P < 0.0005). Visual acuity was improved or remained within one line of the preoperative visual acuity in 90 eyes (87.4%). Complications occurred in 74 eyes (71.8%). A significant portion of these complications (45%) was transient, resolving without any intervention. Only 8% were serious sight-threatening complications. The most common complications included shallow anterior chamber or hypotony (32%), choroidal effusion or hemorrhage (20.4%), corneal decompensation or edema (17.5%), hyphema (14.1%), and tube obstruction (12.6%). CONCLUSION: The Baerveldt implant is effective in lowering the IOP in patients with intractable glaucomas. Hypotony and other complications are common, which also have been reported in other nonvalved glaucoma drainage implants. However, the majority of these complications did not affect surgical outcome.

Adolescent↗
PubMed1995

Elastosis of the lamina cribrosa in pseudoexfoliation syndrome with glaucoma.

BACKGROUND: Pseudoexfoliation syndrome is characterized by the presence of glycoprotein fibers in ocular and extraocular tissues, and often is associated with glaucoma. Pseudoexfoliation material may be associated closely with elastic microfibrillar-associated glycoprotein as well as elastin. METHODS: Four optic nerve heads of two patients with pseudoexfoliation syndrome and glaucoma were examined using electron microscopy and immunogold detection of elastin. Optic nerve heads from healthy age-matched individuals and patients with primary open-angle glaucoma were used for comparisons. RESULTS: In all eyes with pseudoexfoliation and glaucoma, there was marked and widespread elastosis in the connective tissue of the lamina cribrosa. Elastotic fibers appeared as large and irregular aggregates of electron-dense material labeled with anti-elastin antibody. Abundant microfibrils were interspersed in the elastotic aggregates, whereas no typical pseudoexfoliation fibers were observed. In contrast, there were less elastotic fibers in the lamina cribrosa from patients with primary open-angle glaucoma compared with pseudoexfoliation glaucoma. Other changes of extracellular matrix were similar to those observed in primary open-angle glaucoma: decreases in collagen fiber density, presence of basement membranes not associated with cell surfaces, and abundant bundles of microfibrils not labeled with elastin antibody. The elastic fibers appeared normal in other locations within the optic nerves of patients with pseudoexfoliation glaucoma, including in the pial septa and blood vessels of the retrolaminar myelinated optic nerve. CONCLUSION: The authors' findings demonstrate marked and site-specific elastosis in the lamina cribrosa of patients with pseudoexfoliation syndrome with glaucoma, suggesting an abnormal regulation of elastin synthesis and/or degradation in the optic nerve of patients with this disease.

Aged↗
PubMed1994

Histopathologic features of the floppy eyelid syndrome. Involvement of tarsal elastin.

PURPOSE: Patients with the floppy eyelid syndrome have chronic papillary conjunctivitis with easily everted upper eyelids and a soft, pliant upper tarsus. The purpose of this study is to describe the clinical features and the histopathologic correlate in a group of patients with floppy eyelid syndrome. METHODS: The authors examined eight patients with floppy eyelid syndrome, four of whom underwent surgical management with horizontal eyelid shortening. Eyelid tissue from these patients was examined using light microscopy, electron microscopy, and immunohistochemistry and compared with controls with unrelated eyelid or orbital disorders. RESULTS: Clinical findings included obesity or eye rubbing, lash ptosis, and, less commonly, blepharoptosis. Two patients had documented sleep apnea with abnormal sleep electroencephalogram. Light microscopy of the surgical specimens showed chronic conjunctival inflammation, papillary conjunctivitis, and meibomian gland abnormalities, including granuloma formation. Verhoeff's modified elastin stain demonstrated a marked decrease in the amount of elastin fibers in tarsus from patients with floppy eyelid syndrome compared with controls. Immunohistochemical staining for elastin also showed a marked decrease of tarsal elastin in floppy eyelid patients compared with controls. In contrast, immunohistochemical stains showed that the distribution of collagen types I and III was similar between patients with floppy eyelid syndrome and controls. Electron microscopy demonstrated that tarsal collagen was comparable in patients and controls, and that there was a reduced amount of tarsal elastin in floppy eyelid syndrome compared with controls. CONCLUSIONS: These findings demonstrate that tarsal elastin is decreased in the floppy eyelid syndrome, which may contribute to the laxity of the tarsus in this disorder.

Adult↗