Biomedical subjects

W C Stewart

Publications and source records attributed to W C Stewart.

At least 73 records · Page 4Linked to original sources

PubMed1996

A 90-day study of the efficacy and side effects of 0.25% and 0.5% apraclonidine vs 0.5% timolol. Apraclonidine Primary Therapy Study Group.

OBJECTIVE: To compare long-term intraocular pressure (IOP)-lowering efficacy of 0.25% and 0.5% apraclonidine hydrochloride with 0.5% timolol maleate. DESIGN: Multicenter, randomized, double-masked trial. Adult patients of either sex diagnosed as having open-angle glaucoma or ocular hypertension were enrolled following appropriate washout from all ocular hypotensive medications. Morning IOPs of 22 to 35 mm Hg were required for entry. Patients received 0.25% or 0.5% apraclonidine 3 times a day or 0.5% timolol twice a day for 90 days. Intraocular pressure was measured at 8 AM (before morning dosing) and at 4 PM (8 hours after dosing) on days 1, 30, and 90, and only at 8 AM on day 14. RESULTS: All 3 medications significantly reduced IOP from baseline at all observation times (P < .001): 0.5% apraclonidine reduced IOP more than 0.25% apraclonidine; no significant difference was observed between 0.5% apraclonidine and 0.5% timolol 8 hours after dosing on days 1, 30, and 90; and a significant difference (P < .05) in favour of 0.5% timolol over 0.25% apraclonidine was observed 8 hours after dosing on day 30. At all morning visits following evening dosing, 0.5% timolol significantly reduced IOP more than both concentrations of apraclonidine. CONCLUSIONS: Both 0.25% and 0.5% apraclonidine significantly reduce IOP when used as primary ocular hypotensive medication. Although 0.25% and 0.5% apraclonidine reduce IOP to a similar degree as 0.5% timolol 8 hours after morning dosing, neither concentration is as effective for reducing morning IOP after evening dosing.

Administration, Topical↗

PubMed1996

Systemic side effects of topical beta-adrenergic blockers.

Glaucoma, a disease that affects between 1 and 3% of the population above the age of 60, is most commonly treated by topical beta-adrenergic blockers. Although effective in lowering intraocular pressure and helping to preserve sight, beta blockers also may have adverse influences on the cardiac, pulmonary, and central nervous systems, and on endocrine functions. Clinicians' awareness that their patients may be treated with topical beta blockers will help them to elicit this information and the history, prescribe the medicine correctly, and be cognizant of a possible role this medicine may have in any deterioration of a patient's systemic clinical status.

Adrenergic beta-Antagonists↗

PubMed1996

Surgical vs medical management of chronic open-angle glaucoma.

PURPOSE: We studied patients with chronic open-angle glaucoma who had similar intraocular pressures to determine whether surgical or medical therapy is more effective in preventing progressive, long-term, glaucomatous damage. METHODS: Included in this study were patients with chronic open-angle glaucoma who were followed for 3 years or longer and were treated, through either medical or surgical therapy, by adjusting intraocular pressure to 18 mm Hg or less as a therapeutic end point. We studied 31 matched pairs of patients in which one member was treated by surgery and one member had medical treatment. In every pair, we matched each patient individually by age, race, and intraocular pressure. RESULTS: For the matched pairs of patients in this study, the mean intraocular pressure following initiation of treatment was 13.5 and 13.1 mm Hg for the surgically and medically treated groups, respectively (P = .475). This study found no difference between groups in the incidence of glaucomatous progression following surgical (n = 3) or medical (n = 3) therapy (P > .99, McNemar's test) for an average follow-up of 40.0 +/- 10.0 and 43.4 +/- 8.4 months in the medical and surgical groups respectively. The glaucoma of three patients progressed on the basis of reduced visual acuity, two by visual field, and one by disk hemorrhage. Although the types of complications from therapy differed between groups, no vision loss or life-threatening events occurred directly from these treatments. CONCLUSIONS: When intraocular pressure is used as a therapeutic end point, both filtration surgery and medical therapy appear to be equally effective in maintaining long-term visual function and a stable optic disk in chronic open-angle glaucoma.

Adrenergic alpha-Agonists↗

PubMed1996

Total cholesterol and high-density lipoprotein levels as risk factors for increased intraocular pressure.

PURPOSE: To determine whether high-density lipoprotein and total cholesterol levels were risk factors for increased intraocular pressure in patients with chronic open-angle glaucoma or ocular hypertension. METHODS: We measured total cholesterol, high-density lipoprotein, and total cholesterol/high-density lipoprotein ratio in 25 patients with open-angle glaucoma or ocular hypertension who had taken no glaucoma medications for four weeks. We individually matched these patients to 25 control subjects who had no history of open-angle glaucoma or ocular hypertension, on the basis of age, race, gender, and history of vascular disease or diabetes mellitus. RESULTS: We found no statistical difference in the high-density lipoprotein (P = .702) or total cholesterol (P = .177) levels or total cholesterol/high-density lipoprotein ratio between groups (P = .178, paired t test). CONCLUSION: This study indicates that increased high-density lipoprotein and total cholesterol levels are not risk factors for increased intraocular pressure.

Cholesterol↗

PubMed1996

Timolol hemihydrate vs timolol maleate to treat ocular hypertension and open-angle glaucoma.

PURPOSE: We compared the therapeutic efficacy and safety of timolol hemihydrate to timolol maleate in patients with ocular hypertension and chronic open-angle glaucoma. METHODS: We conducted this three-month study as a multicentered, masked, parallel group comparison. Both the 0.25% and 0.5% concentrations were evaluated against similar concentrations of timolol maleate. Dosing was twice daily. An open-label, nine-month study followed the masked portion of the protocol, in which all patients received either 0.25% or 0.5% timolol hemihydrate. A total of 371 patients were included in both the 0.25% and 0.5% studies. RESULTS: We found statistically similar intraocular pressures with both the 0.25% (18.3 and 18.6 mm Hg for the hemihydrate and maleate groups, respectively) and 0.5% (19.9 and 19.5 mm Hg for the hemihydrate and maleate groups, respectively) concentrations of timolol hemihydrate and timolol maleate after three months of masked treatment. Likewise, peak intraocular effect at two hours after taking the medication was statistically similar between medicines at both concentrations. Likewise, both ocular and systemic safety were similar between the maleate and hemihydrate preparations at both concentrations. In the nine-month open-label protocol, therapeutic efficacy (19.9 and 19.1 mm Hg for the 0.25% and 0.5% concentrations, respectively) and safety of timolol hemihydrate were similar to effect and safety of the three-month protocol. CONCLUSIONS: This study suggests that timolol hemihydrate had an ocular hypotensive efficacy and safety profile statistically equivalent to that of timolol maleate for up to three months of therapy. Timolol hemihydrate showed efficacy and safety similar to that observed within the first three months, for up to one year of therapy.

Adolescent↗

PubMed1996

Magnetic resonance imaging in patients with unexplained optic neuropathy.

PURPOSE: To investigate the anatomic relation between the optic nerve and the adjacent intracranial internal carotid artery (ICA) in patients with unexplained optic neuropathy. METHODS: Coronal magnetic resonance images (MRIs) of 20 patients with unexplained optic neuropathy and 20 age-matched controls were evaluated with digitizing software. RESULTS: The distance between the optic nerve and ICA was significantly less on the side ipsilateral to the atrophic optic nerve than either the study group's contralateral optic nerve-ICA distance (P<0.001) or the control group's optic nerve-ICA distance (P<0.001). The diameter of the atrophic optic nerves was significantly less than either the diameter of the study group's contralateral normal nerves (P=0.008) or the control group's nerves (P<0.001). There was no significant difference between the diameters of the ICA flow voids adjacent to the atrophic optic nerves versus either the study group's contralateral ICA flow voids (P=0.91) or the control group's ICA flow voids (P=0.74). CONCLUSIONS: The authors speculate that the intimate relation between the optic nerve and adjacent ICA may be important in the development of unexplained optic neuropathy. The ICA need not appear abnormal in MRIs.

Aged↗

PubMed1996

Timolol hemihydrate: a new formulation of timolol for the treatment of glaucoma.

Timolol maleate, a non-selective beta-adrenergic blocker, has been used to treat glaucoma and ocular hypertension for almost two decades. Recently a new preparation, timolol hemihydrate, has been described which eliminates the maleate buffer and simplifies the purification step for the R-enantiomer. The ocular pharmacology of the two medicines is expected to be similar. Ocular bioavailability as well as toxicity for timolol hemihydrate is similar to that which has been shown previously for timolol maleate. In a multicenter trial in the United States, timolol hemihydrate was shown to reduce the intraocular pressure to a similar extent as timolol maleate. At the week 12 visit intraocular pressure was 19.5 and 19.5 mm Hg for the hemihydrate and maleate groups respectively for the 0.25% concentration and 18.3 and 18.6 mm Hg respectively for the 0.5% concentration. Following a nine month open-label portion where patients were treated with timolol hemihydrate only intraocular pressure was 19.9 and 19.1 mm Hg for the 0.25% and 0.5% concentrations respectively. Ocular and systemic adverse events, as well as vital signs, were similar between timolol hemihydrate and maleate. In conclusion, timolol hemihydrate appears to be a safe and effective medicine in the treatment of ocular hypertension and chronic open-angle glaucoma.

Adrenergic beta-Antagonists↗

PubMed1996

Prognostic factors in long-term intraocular pressure control following combined phacoemulsification and trabeculectomy.

We studied 36 consecutive patients who underwent combined phacoemulsification and trabeculectomy to determine prognostic factors associated with intraocular pressure control one year postoperatively. In patients who were either easier (intraocular pressure < 16 mmHg, n = 19) or more difficult (> or = 16 mmHg, n = 17) to control, the mean intraocular pressure increased up to the fourth week postoperatively. In the more difficult to control group, however, the intraocular pressure continued to increase and a statistical difference between groups was noted by the second month postoperatively (P < 0.05). The peak intraocular pressure within the first month postoperatively was lower in patients easier to control long-term (P < 0.005). No statistical difference between groups in the filtering bleb or anterior chamber appearance, or postoperative complications, was noted (P > 0.05). This study suggests combined trabeculectomy and phacoemulsification is safe and effective in controlling intraocular pressure postoperatively. Determining from the early postoperative examination the long-term pressure control, however, is difficult.

Aged↗

PubMed1996

Differences in optic discs in low-tension glaucoma patients with relatively low or high pressures.

We evaluated the differences in the optic nerve head in patients with chronic open-angle glaucoma (HTG) and those with low-tension glaucoma with either relatively high (between 16 and 21 mmHg [LTGH]) or low (< or = 15 mmHg [LTGL]) intraocular pressures. We included 36 patients in this study. We found that LTGL patients had a significantly greater mean area of peripapillary atrophy inferior to the optic disc (0.65 +/- 0.38 mm2) than LTGH (0.40 +/- 0.38 mm2) or HTG (0.34 +/- 0.25 mm2) patients (p < 0.005). No significant difference was found between groups for the area of the neural rim, optic disc, cup/pallor discrepancy, or peripapillary halo, or in the diameter of the largest artery or vein in the inferior and superior peripapillary area. This study raises the question of whether a separate mechanism of damage could exist at the optic disc in patients whose intraocular pressure is < or = 15 mmHg because of a greater extent of peripapillary atrophy than in patients with higher intraocular pressures.

Aged↗

PubMed1996

Contact versus noncontact diode laser transscleral cyclophotocoagulation in cadaver eyes.

BACKGROUND AND OBJECTIVE: The optimal placement and laser energy levels of a new contact probe with a variable focus used for transscleral diode cyclophotocoagulation were compared with the diode laser noncontact technique. MATERIALS AND METHODS: Fresh cadaver eyes were evaluated by a modified posterior Miyake view using videotape, light microscopy, and scanning electron microscopy. RESULTS: The noncontact diode technique at maximum energy (1.2 J) and contact diode applications at similar energy levels failed to produce obvious gross tissue ciliary body change and mild alterations by histology. Consistent gross, histologic, and scanning electron microscopic damage was noted at 3.0 J or more with the contact probe placed at the surgical limbus and defocused 0.5 to 1.5 mm posteriorly. CONCLUSIONS: This study indicates that the Multilase contact diode laser causes transscleral ciliary body destruction in a cadaver eye model and may have potential clinical usefulness.

Cadaver↗

PubMed1996

Ultrastructural features of filtration blebs with different clinical appearances.

The authors studied two functioning filtration blebs to evaluate a possible transconjunctival route of aqueous humor flow and describe potential differences between thin cystic and thick opaque functioning filtration blebs. The specimens were prepared for light and electron microscopy immediately after surgical excision because of filtration bleb discomfort. Both blebs had normal collagen in the substantia propria. The collagen, however, was widely spaced and subepithelial connective tissue loosely arranged. Clear spaces were seen in the superficial substantia propria. Epithelial cells were focally acantholytic, separated by clear spaces. Consequently, clinically distinct blebs demonstrated similar histologic and ultrastructural features. The epithelial intercellular spaces observed in this study provide anatomic evidence that aqueous could move transconjunctivally as a mechanism for filtration bleb function.

Aged↗

PubMed1996

Three-millimeter versus 6-mm incisions in combined phacoemulsification and trabeculectomy.

BACKGROUND AND OBJECTIVE: To determine the results of phacoemulsification and combined trabeculectomy in subjects receiving either a 3- or a 6-mm scleral incision. PATIENTS AND METHODS: The authors evaluated consecutive patients who underwent combined phacoemulsification and trabeculectomy with a 3-mm incision. These patients were individually matched by age, diagnosis, previous surgery, and race to those having a 6-mm incision. RESULTS: The study found that 1 year following surgery, results were similar between the 3- and 6-mm incision groups for intraocular pressure (IOP), bleb height, bleb vascularity, number of glaucoma medicines, anterior chamber depth, visual acuity, spherical equivalent, cylinder, and axis (P > .05). No difference was observed between groups with the highest IOP within the first postoperative month (P > .05). Also, no marked differences in number of complications were noted between groups. CONCLUSION: This study suggests that 3- and 6-mm incision phacoemulsification combined with trabeculectomy provide similar postoperative IOP control and visual acuity results.

Aged↗

PubMed1996

[Effect and side effects of apraclonidine].

Apraclonidine is a alpha 2 adrenergic agonic which is a para-amino derivative of clonidine. This molecular alteration helps prevent apraclonidine from crossing the blood-brain barrier so it minimally influences the heart rate and blood pressure. Apraclonidine reduces the intraocular pressure primarily by an aqueous suppressant mechanism. Its ocular hypotensive efficacy as monotherapy is similar to timolol maleate 0.5% up to eight hours post dosing, but is less than timolol maleate by 12 hours following instillation. As an adjunctive agent apraclonidine decreases the intraocular pressure approximately 16% over that of timolol maleate done. These clinical effects are stable out of three months after the initiation of therapy. Apraclonidine is also additive to maximally tolerated medical therapy. As many as 60% of these patients do not require additional therapy after adding apraclonidine for as long as five months. Apraclonidine also is useful to prevent transiently increased intraocular pressure following anterior segment laser procedures and intraocular surgery. Apraclonidine is well tolerated systemically with no serious adverse event attributed previously to this medicine. The most common ocular side effect is anterior segment intolerance in between 8-36% of patients. Symptoms of itching, as well as burning, and signs of conjunctival inflammation may appear. The intolerance quickly resolves upon discontinuation of the medicine. In summary, apraclonidine is useful in chronic therapy for chronic open-angle glaucoma and helping to prevent acute increased intraocular pressure following anterior segment laser procedures.

Adrenergic alpha-Agonists↗

PubMed1995

Magnetic resonance imaging in patients with low-tension glaucoma.

OBJECTIVE: To study diagnoses and anatomic findings found on magnetic resonance imaging in patients with low-tension glaucoma. PATIENTS: We included in this study magnetic resonance images of 20 consecutive patients with low-tension glaucoma. We individually matched each patient with low-tension glaucoma to a control with normal ocular findings who had magnetic resonance imaging for reasons unrelated to the visual pathway. DESIGN: We studied axial and coronal images of the orbit and optic nerve with digitizing software (Image-Pro Plus, Media Cybernetics, Silver Spring, Md). Statistical evaluation was with a Wilcoxon Signed Rank Test for anatomic findings and a McNemar Test for diagnosis. RESULTS: We found no difference between groups in the optic nerve diameter or length, the carotid artery area, or the distance from the optic nerve to the carotid artery (P > .05). Left optic nerve area was greater in the control patients than patients with low-tension glaucoma (P = .026). The prevalence of intracranial abnormalities, including meningioma, aneurysm, and arteriovenous abnormality, was similar between groups (P > .05). However, diffuse cerebral small-vessel ischemic changes were found more in patients with low-tension glaucoma (n = 8) than control patients (n = 1) (P = .0196). CONCLUSIONS: This study proposes a hypothesis that cerebral small-vessel ischemia is more common in patients with low-tension glaucoma and potentially reflects indirectly a vascular cause of the optic nerve head damage at least in a subgroup of patients. Importantly, further research still is required to provide direct evidence for a vascular cause involved in low-tension glaucoma.

Aged↗

PubMed1995

The efficacy of apraclonidine as an adjunct to timolol therapy. Apraclonidine Adjunctive Therapy Study Group.

OBJECTIVE: To compare the intraocular pressure (IOP) lowering efficacy of 0.5% and 1.0% apraclonidine hydrochloride when used adjunctively with 0.5% timolol maleate in 129 patients. DESIGN: A multicenter, randomized, double-masked clinical trial. Adult patients of either sex diagnosed as having either open-angle glaucoma or ocular hypertension were enrolled in the study. Patients using only 0.5% timolol maleate twice daily for at least 4 weeks and who had 8 AM IOPs of at least 22 mm Hg and no greater than 30 mm Hg 12 hours after dosing were eligible for the study. After 8 AM baseline IOPs were obtained while patients were taking timolol only, they were then randomized to receive either 0.5% or 1.0% apraclonidine twice daily in addition to their timolol. Intraocular pressures were measured at 8 AM (before morning dosing) and at 11 AM (3 hours after dosing) on days 14 and 90 and at 8 AM only on day 45. RESULTS: Both concentrations of apraclonidine produced significant IOP reductions from baseline at all visits (P < .001). At 8 AM, after the nighttime dose, the additional mean IOP reduction from the timolol baseline ranged from 2.5 to 3.3 mm Hg (10.3% to 13.6% reduction, respectively). At 11 AM, 3 hours after the morning dose, the additional IOP reduction from the timolol baseline ranged from 4.7 to 5.2 mm Hg (20.0% to 21.7%, respectively). No difference in IOP reduction was observed between the 0.5% and 1.0% apraclonidine concentrations and no loss of IOP efficacy was observed for either concentration for the duration of the study. Sensitivity to 0.5% and 1.0% apraclonidine was observed in nine (13.8%) and 13 (20.3%) patients, respectively. Overall, therapy was discontinued owing to ocular or nonocular side effects with 0.5% and 1.0% apraclonidine in 14 (21.5%) and 16 (25%) patients, respectively. CONCLUSIONS: We believe that 0.5% apraclonidine is equally effective as 1.0% apraclonidine when used twice daily as the first adjunctive drug to timolol. The drug effect is maintained for at least 90 days.

Adrenergic alpha-Agonists↗

PubMed1995

Effect of cataract extraction on automated fields in chronic open-angle glaucoma.

OBJECTIVE: To evaluate the influence of cataract extraction on the results of visual field testing in chronic open-angle glaucoma. DESIGN: We performed automated perimetry within 6 months before and after phacoemulsification and combined trabeculectomy in 24 consecutive patients with chronic open-angle glaucoma. Eyes were pharmacologically dilated and were tested with their best corrected refraction for each visual field performed. RESULTS: After surgery, the average mean defect, pattern SD, and total decibel loss within any visual field cluster (as determined by the Glaucoma Hemifield Test, Humphrey Field Analyzer, Humphrey Instruments, San Leandro, Calif) did not change significantly (P > .05, paired t test). These findings did not vary on the basis of the amount of preoperative damage in the visual field. The power of this study to exclude a 4-dB change in the mean defect after surgery was 86.5%. CONCLUSION: This study suggests that cataract extraction in patients with chronic open-angle glaucoma has minimal effect on the visual field test results after surgery.

Aged↗

PubMed1995

Correlation of pattern discrimination perimetry to the optic disc and visual field in ocular hypertensive and chronic open-angle glaucoma patients.

We evaluated 19 ocular hypertensive and 32 chronic open-angle glaucoma patients to determine the correlation of pattern discrimination field loss to known markers of glaucomatous damage on the visual field and the optic nerve head. This study found no statistical association of the findings on the pattern discrimination perimeter to the areas of the optic disc, peripapillary halo, peripapillary atrophy, neural rim, or cup/pallor discrepancy (P > 0.05). In addition, no statistical relationship was observed to the diameters of the largest vein or artery in the inferior- or superior-temporal quadrant adjacent to the optic disc (P > 0.05). Between pattern discrimination and automated perimetry no agreement was observed in any visual field cluster (Glaucoma Hemifield Test) greater than that expected by chance alone (P > 0.05). When both visual function tests disagreed, the proportion of abnormal diagnoses in any cluster did not differ statistically between tests in chronic open-angle glaucoma patients (P > 0.05). However, in ocular hypertensive patients a greater proportion of abnormal diagnoses was observed with pattern discrimination perimetry (P < 0.03). This study suggests that pattern discrimination perimetry appears to measure a different physiologic property of the retina than does automated perimetry.

Adult↗

PubMed1995

The effect of lifestyle on the relative risk to develop open-angle glaucoma.

Patients may inquire how lifestyle or emotions may influence their intraocular pressure or risk for developing chronic open-angle glaucoma. Currently, little modification of lifestyle (including diet, drugs, emotion, activity, or risk factors for cardiovascular disease or diabetes) can be advised to reduce the risk of developing chronic open-angle glaucoma. In appropriate patients, however, suggesting limiting total-body inversion or isotonic exercise may help prevent a transient intraocular pressure increase. In patients who are in good general health, and are motivated, an aerobic exercise program might provide a small decrease in the intraocular pressure. Also, limiting cigarette smoking or alcohol consumption several hours before an ocular examination may help prevent a falsely altered intraocular pressure measurement. In the future, modifiable risk factors for chronic open-angle glaucoma may become known. This may give the patient more control over the disease by altering their lifestyle.

Blinking↗