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Biomedical subjects

C O'Brien

Publications and source records attributed to C O'Brien.

At least 163 records · Page 9Linked to original sources

Adverse effects of topical antiglaucoma medication. I. The conjunctival cell profile.

OBJECTIVE: To determine the effect of various long-term topical antiglaucoma regimens on the cell population profile of the conjunctiva. METHODS: Conjunctival biopsy specimens from 124 patients undergoing filtration surgery were assessed quantitatively by light microscopy. Preoperatively, the patients had used a drug for only a brief period (group A; n = 28), a beta-blocker alone (group B; n = 31), a beta-blocker in combination with a miotic (group C; n = 33), or a combination of beta-blocker, miotic, and sympathomimetic (group D; n = 32). RESULTS: The conjunctiva in groups A and B was similar. Group C conjunctiva differed, but the changes were most marked in biopsy specimens from patients in group D, where there was a significant decrease in goblet cells (P < .05); increase in pale cells, macrophages, and lymphocytes within the epithelium (P < .001); and increase in fibroblasts (P < .001), macrophages (P < .001), mast cells (P < .05), and lymphocytes (P = .01) in the substantia propria. In addition, the effect of duration of therapy was assessed. Administration of topical medication for more than 3 years was found to increase the numbers of pale cells within the epithelium (P < .05); fibroblasts (P < .05), macrophages (P < .001), lymphocytes (P < .01), and mast cells (P = .001) within the superficial substantia propria; and the numbers of fibroblasts (P = .01) and macrophages (P < .05) within the deep substantia propria. CONCLUSIONS: The compared treatment regimens affected the conjunctiva to different degrees, with multiple-drug topical therapy exerting the greatest effect on the degree of subclinical inflammation within the conjunctiva. The results also indicated that administration of topical medication, irrespective of type, for 3 years or more induced a significant degree of subclinical inflammation.

Administration, Topical↗

Adverse effects of topical antiglaucoma medication. II. The outcome of filtration surgery.

OBJECTIVE: To determine the effect of long-term topical antiglaucoma therapy on the results of glaucoma filtration surgery and to relate any differences to the cell population profile of the conjunctiva. METHODS: Filtration surgery was performed in 124 patients (trabeculectomy in 112 and triple procedures [trabeculectomy, cataract extraction, and intraocular lens implantation] in 12), and the outcome of these procedures was assessed after a minimum follow-up of 6 months. A conjunctival biopsy specimen was obtained at the time of surgery. The patients were divided into four groups according to the type of topical therapy administered. The duration of therapy tended to be greater for the patients treated with a greater number of medication types. The outcome of trabeculectomy was assessed in 106 of the patients. RESULTS: In comparison with the briefly treated-primary surgery group, the success rate of trabeculectomy (90% [n = 28]) was similar to that in the group treated with beta-blockers (93% [n = 29]). The trabeculectomy success rate for patients treated with beta-blockers and miotics was significantly lower (72%, P < .01 [n = 29]), and that for the group treated with beta-blockers, miotics, and sympathomimetics was even lower (45%, P < .001, [n = 20]). CONCLUSIONS: Various treatment regimens were associated with differential effects on the success rate of trabeculectomy. Long-term topical combination therapy was identified as a significant risk factor for failure of trabeculectomy. Preoperative conjunctival cell counts from patients whose trabeculectomies were successful were compared with those whose trabeculectomies failed. Failure was associated with significantly more pale cells (P < .01), macrophages (P < .05), and lymphocytes (P < .05) in the epithelium; fibroblasts (P < .05) and macrophages (P < .05) in the superficial substantia propria; and both macrophages and lymphocytes in the deep substantia propria (P < .01). Thus, preoperative subclinical conjunctival inflammation induced by previous topical medication was identified as a risk factor for failure of trabeculectomy.

Administration, Topical↗

Spinal extradural arteriovenous malformation presenting with recurrent hemorrhage and intermittent paraplegia: case report and review of the literature.

Symptomatic spinal extradural arteriovenous malformations (AVMs) are uncommon. They usually present with slowly progressive myelopathy and/or radiculopathy and only rarely with spinal extradural hemorrhage (SEH). Histopathologic features of a true spinal extradural AVM causing an overt SEH have only previously been described in four cases. A further case of a histologically confirmed spinal extradural AVM causing SEH in a 50-year-old otherwise medically normal Caucasian woman is presented. Recurrent hemorrhage resulted in intermittent paraplegia and acute chest/shoulder pain--diagnosed initially as hysteria. Interesting sequential myelographic, computed tomographic, and magnetic resonance imaging studies are presented, and the literature on spinal extradural AVMs presenting with SEH is reviewed.

Arteriovenous Malformations↗

Axial length biometry in infants with retinopathy of prematurity.

Ultrasound axial length measurements were obtained on infants under a birthweight of 1500 g or 32 weeks gestation undergoing screening for retinopathy of prematurity (ROP). A total of 496 readings were obtained on 171 infants between 32 and 41 weeks post-conceptual age. Other details recorded were maximum stage of acute ROP, birthweight, gestational age, sex, and biparietal and occipitofrontal head diameters. The relationship of these variables to axial growth of the eye was examined using analysis of covariance with a repeated measures approach. Mean axial length increased from 15.27 mm to 16.65 mm in the left eye during this period. Following adjustment for repeated readings a growth rate of 0.18 mm/week was obtained for both eyes. Male infants were found to have longer axial lengths despite correction for birthweight, gestation and head size (p < 0.0001 right and left). Higher stages of acute ROP were also associated with shorter axial length (p < 0.05 for all stages of both eyes) but the rate of growth during the study period did not demonstrate significant differences between stages. Stage 3 infants reaching the threshold for cryotherapy had shorter axial length than stage 3 infants not receiving treatment. The effect of prematurity on the growth of the eye and the significance of these findings with respect to the subsequent development of refractive errors in premature infants are discussed.

Analysis of Variance↗

Diurnal intraocular pressure variation in low-tension glaucoma.

A retrospective analysis of diurnal variation in intraocular pressure (IOP) in 101 untreated low-tension glaucoma (LTG) patients was carried out to ascertain the role of IOP as a causative factor in the aetiology of optic nerve damage in LTG. The diagnosis of LTG was made only after IOP monitoring as an inpatient, which involved 2 hourly consecutive measurements by Goldmann applanation tonometry from 08:00 to 22:00 hours inclusive. The highest IOP during the diurnal curve was 17.4 mmHg (SD 3.00) at 10:00 and the lowest value was 15.0 mmHg (SD 2.7) at 22:00. Seventy-seven per cent of patients had a peak IOP value recorded between 08:00 and 12:00 hours inclusive. The mean peak IOP was 18.3 mmHg (SD 2.6) and the mean trough was 13.1 mmHg (SD 2.2). Thus the mean diurnal range in IOP of 5.2 mmHg (SD 2.2) was similar to that reported by other workers in normals. Neither the diurnal pattern nor the range of IOP values seen in this study supports the view that abnormal IOP levels are a significant risk factor in the pathogenesis of optic nerve damage in all patients with LTG.

Adult↗

Ocular biometry in pre-term infants without retinopathy of prematurity.

Serial ocular A-scan ultrasound biometry was performed on 100 pre-term infants (less than 32 weeks gestation and/or less than 1500 g) who did not show features of retinopathy of prematurity (ROP) during a screening programme. Axial length increased from 15.38 +/- 0.25 mm at 33 weeks post-menstrual age to 16.88 +/- 0.59 mm at 41 weeks (rate of growth 0.18 mm/week, r = 0.99). The rate of growth appeared to slow down after 40 weeks (term) to 3 months post-term. Male infants had longer eyes and a greater rate of growth than female infants. Axial length (AL) was significantly correlated with birth weight, biparietal and occipito-frontal diameter in the weeks after birth. Between weeks 33 and 41, the anterior chamber depth (ACD) increased from 1.92 +/- 0.13 mm to 2.43 +/- 0.18 mm, and lens thickness (LT) increased from 3.82 +/- 0.33 mm to 3.90 +/- 0.13 mm. The largest percentage growth between weeks 33 and 41 occurred in ACD (22%), followed by vitreal length (10%), AL (9%) and LT (2%). These data will help in future studies on the role which ROP plays in the development of ocular growth.

Anthropometry↗

Evaluation of the Humphrey FASTPAC threshold program in glaucoma.

The makers of the Humphrey perimeter have developed a rapid thresholding program, FASTPAC, to address the problems of fatigue and poor test performance associated with prolonged perimetry. The performance of FASTPAC was compared with the standard threshold program of the Humphrey visual field analyser (program 24-2) in 44 glaucoma patients. FASTPAC reduced the mean test time by 35% (from 12.6 to 8.2 minutes), owing to a reduction in the number of stimulus presentations. FASTPAC underestimated the mean deviation (MD) (Wilcoxon, p = 0.007) and corrected pattern standard deviation (CPSD) (Wilcoxon, p = 0.005). The sum of the differences between FASTPAC and the standard program was -1.19 (SD 2.37) dB for MD and 0.97 (2.14) dB for CPSD. The measured difference between the two methods was independent of the value of either MD or CPSD, indicating that the measurement error was just as likely to occur with either early or advanced visual field loss. No difference was noted in short term fluctuation or in the reliability indices of test performance. These results indicate that FASTPAC, while considerably faster, is not as accurate as the standard threshold program at measuring retinal sensitivity in glaucoma. This inaccuracy may be offset in practical terms by greater patient acceptability and by increasing the number of patients capable of performing reliable threshold perimetry because of the reduction in duration of the FASTPAC program.

Aged↗

Extradural application of bismuth iodoform paraffin paste causing relapsing bismuth encephalopathy: a case report with CT and MRI studies.

Bismuth iodoform paraffin paste (BIPP) is used in dressings in ear, nose, and throat, dental, and neurosurgical practice. Neurotoxicity due to absorption of bismuth from the BIPP pack is rare. It is preventable and reversible but likely to be fatal if unrecognised. A case of relapsing but reversible toxic encephalopathy due to a large extradural BIPP pack is reported in a 57 year old Caucasian woman, operated on for a huge basal cell carcinoma of the vertex invading the skull and extradural space. Clinical, neuroradiological (CT and MRI), and biochemical studies are presented and discussed in the light of the available literature.

Bandages↗

Responses to moderate and low sodium diets during exercise-heat acclimation.

This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+.d-1) or moderate Na+ (MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n = 8) or MNA (n = 9) during HA (41 degrees C, 21% RH; treadmill walking for 30 min.h-1, 8 h.d-1 at 5.6 km.h-1, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+ for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.

Acclimatization↗

Electrophysiology of type II mesangiocapillary glomerulonephritis with associated fundus abnormalities.

The retinal electrophysiology is reported in four patients with type II mesangiocapillary glomerulonephritis and partial lipodystrophy with associated fundus abnormalities and no visual symptoms. The histological hallmark of the condition is that of widespread electron dense deposits in the renal glomerulus and in the choriocapillaris and Bruch's membrane of the eye. Three of the four patients had the typical fundal appearance of multiple, yellow, drusen-like lesions at the posterior pole of the eye with normal visual acuity. These three patients had abnormally low Arden ratios on electro-oculography with normal electroretinography responses. This is the first clinical model of disease known to be isolated to the choriocapillaris and Bruch's membrane causing an electro-oculographic abnormality without any clinically detectable deficit in visual function.

Adult↗

Neurotoxic damage evokes regenerative responses from adult rat sensory neurones.

When adult rats were pre-treated systemically with the excitotoxin, capsaicin, a subset of their dorsal root ganglion (DRG) sensory neurones responded as if they had been axotomised. Firstly, an increased proportion of capsaicin-sensitive DRG neurones (identified by using a cobalt stain) vigorously extended processes in vitro. Additionally, a subset of small dorsal root ganglion neurones expressed elevated levels of the growth-associated protein-43 (GAP-43) in situ. Both vigorous neuritogenesis and elevated GAP-43 levels are characteristics of neurones that are actively regenerating following mechanical damage. Although capsaicin-treated adult DRG neurones show these regenerative responses, their C-fibers fail to regenerate in vivo.

Animals↗

Hyperhomocysteinaemia: a risk factor for extracranial carotid artery atherosclerosis.

Hyperhomocysteinemia arising from impaired methionine metabolism, and usually due to a deficiency of cystathionine beta-synthase is a significant and independent risk factor for symptomatic vascular disease. It is not known if hyperhomocysteinemia in apparently healthy asymptomatic subjects is associated with atherosclerosis and whether such a relationship is independent of conventional risk factors. The prevalence of asymptomatic extracranial carotid artery atherosclerosis was determined by duplex ultrasound examination in 25 obligate heterozygotes with respect for cystathionine beta-synthase deficiency (whose children were known to be homozygous for this genetic defect) and in 21 controls. Hyperhomocysteinemia was determined by a standard methionine-loading test and conventional risk factors were also recorded. Twelve of 25 obligate heterozygotes and 8 of 21 normal controls had evidence of extracranial carotid artery atherosclerosis. Hyperhomocysteinemia as a genetic trait was not a significant risk marker, but the actual homocysteine level was associated with an increased risk of carotid disease. After adjustment for the effects of other significant risk factors, the odds ratio of hyperhomocysteinemia for carotid disease was 1.038 per unit increase in homocysteine level (P = 0.03). Hyperhomocysteinemia is a weak risk factor for asymptomatic extracranial carotid atherosclerosis and the relative risk associated with this genetic trait is less than that observed in a study of patients presenting with clinical manifestations of vascular disease.

Adult↗