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Biomedical subjects

A C Crichton

Publications and source records attributed to A C Crichton.

9 recordsLinked to original sources
PubMed2001

Intraocular pressure and medication control after clear corneal phacoemulsification and AcrySof posterior chamber intraocular lens implantation in patients with filtering blebs.

PURPOSE: To determine whether clear corneal phacoemulsification and the implantation of a copolymer acrylic (AcrySof, Alcon, Fort Worth, TX) intraocular lens will maintain the intraocular pressure (IOP) and number of medications in patients with a previous filtering bleb. PATIENTS AND METHODS: This retrospective analysis included 69 consecutive patients with previous trabeculectomy who had a copolymer acrylic intraocular lens implanted during cataract surgery between 1995 and 1999 by a single surgeon (A.C.S.C.). RESULTS: Mean IOP significantly decreased from 26.03 mm Hg (range, 14.5-70 mm Hg; n = 69) before trabeculectomy to 13.58 +/- 3.98 mm Hg (range, 5-24 mm Hg; n = 69) before the cataract extraction. After cataract extraction, the mean IOP increased significantly by 1.49 mm Hg (n = 67; P = 0.0013), by 1.85 mm Hg (n = 57; P = 0.0005), and by 1.01 mm Hg (n = 67; P = 0.042) after 6 months, after 1 year, and at the patient's last appointment, respectively. When patients whose pressures were purposely increased during cataract surgery were not included (n = 5), the mean increase at the last appointment was not significantly increased (0.54 mm Hg; n = 62; P = 0.25). The average number of antiglaucoma medications decreased from 2.93 (range, 1-5; n = 69) before trabeculectomy to 0.36 (range, 0-2; n = 69) before cataract surgery. This mean decreased to 0.34 (range, 0-2; n = 67; P = 0.8366) 6 months after cataract surgery and increased to 0.49 (range, 0-3; n = 57; P = 0.1029) and 0.62 (range, 0-3; n = 67; P = 0.0006) after 1 year and at the last appointment, respectively. Of the total study population, two (2.9%) patients required additional glaucoma surgery and 14 (20.3%) patients required additional antiglaucoma medications as compared with their precataract levels. CONCLUSIONS: Clear corneal phacoemulsification and the implantation of a copolymer acrylic (AcrySof, Alcon) posterior chamber intraocular lens statistically increased the number of medications and IOP of patients in our study. These increases, although statistically significant, did not cause a clinically significant deterioration in IOP control.

Acrylates↗
PubMed1997

Reduced intraocular pressure and increased ocular perfusion pressure in normal tension glaucoma: a review of short-term studies with three dose regimens of latanoprost treatment.

Currently used ocular hypotensive agents do not effectively lower intraocular pressure (IOP) in some normal-tension glaucoma (NTG) patients. The prostaglandin F2 alpha analogue, latanoprost, has been shown to reduce IOP in normal subjects and ocular hypertensive glaucoma patients by increasing uveoscleral outflow. This mechanism is expected to be particularly effective in the lower IOP range that is typical of NTG. To date, three dose regimens of latanoprost have been shown to reduce IOP significantly in NTG. The IOP reductions of 14.2% and 15% obtained with twice-daily application of 0.0015% and 0.006% latanoprost, respectively, were comparable to the modest IOP reduction that has been reported for other glaucoma drugs in NTG. In contrast, once-daily application of 0.005% latanoprost resulted in a 21.4% IOP reduction. In another study that included 24-hour monitoring of systemic blood pressure and heart rate in NTG patients, the ocular perfusion pressure was found to improve more on once-daily 0.005% latanoprost than on twice-daily treatment with 0.5% timolol. Thus, once-daily 0.005% latanoprost appears to be a more effective and more convenient ocular hypotensive agent for treating NTG than currently used glaucoma drugs. However, long-term studies will ultimately be needed to establish the efficacy of this new drug to delay or prevent the progression of visual field loss in normal tension glaucoma.

Administration, Topical↗
PubMed1996

The role of small-incision cataract surgery in combined cataract and glaucoma surgery.

Small-incision cataract surgery widens the scope of combined cataract and glaucoma surgery. Phacoemulsification is gaining in importance, although extracapsular extraction techniques are still commonly used. Trabeculectomy remains the standard filtration operation combined with cataract surgery. There are currently a number of areas of contention in combined trabeculectomy surgery, including-the use of shared or separate incisions, the use of antimetabolities, and the type of intraocular implant. Other adjunctive procedures such as trabeculotomy and endocyclophotocoagulation are also discussed in the context of combined surgery.

Cataract↗
PubMed1996

The use of ultrasound biomicroscopy following trabeculectomy.

OBJECTIVE: To determine whether ultrasound biomicroscopic (UBM) appearance can predict successful lowering of the intraocular pressure following trabeculectomy. DESIGN: Blinded prospective study. SETTING: Glaucoma clinic at a tertiary care hospital in Calgary. PATIENTS: Forty-six patients who had undergone trabeculectomy 1 week to 22 years earlier were recruited. In three cases UBM scanning was stopped because of discomfort, and five studies were excluded because the clinical information became known to the ultrasonographer. A total of 44 studies from 46 patients were analysed. OUTCOME MEASURES: Intraocular pressure and need for medication, UBM appearance. RESULTS: In 38 (86%) of the 44 studies there was a positive association between the UBM grade and the clinical findings. UBM had a sensitivity of 91% in predicting a functioning bleb and a specificity of 70% in predicting a nonfunctioning bleb. CONCLUSIONS: UBM is a useful adjunct to the glaucoma surgeon in the management of certain patients following trabeculectomy.

Aged↗
PubMed1993

Ultrasonography to assess patency of the tube in Molteno seton implantation.

It is occasionally difficult to ascertain postoperatively whether a Molteno implant is functioning or not. We have found that ultrasonography (B-scan) is a useful diagnostic tool in assessing tube patency. Polaroid images of 29 ultrasound pictures, 8 with occluded tubes, were taken postoperatively and presented independently to a radiologist and a retinal specialist, who were asked to determine the functioning state of the Molteno implant. In all cases the observers were able to correctly identify whether the tube was patent or not.

Adult↗
PubMedDate not supplied

Gold implant treatment for discomfort induced by a filtering bleb.

We present a post-trabeculectomy patient suffering from blurred vision and foreign body sensation that was not alleviated by conventional treatments. Our treatment involved placing a gold weight implant onto the anterior surface of the tarsal plate to gravity-assist closure and increase coverage of the filtering bleb.

Eyelids↗
PubMedDate not supplied

Ultrasound biomicroscopy for the assessment of Molteno tube position.

Due to anatomic distortion or surgical complications, it may be difficult to determine the precise position of an implanted Molteno tube. We performed ultrasound biomicroscopy (high-resolution ultrasound) to test the usefulness of this modality in localizing implanted Molteno tubes in 10 patients with Molteno tubes. A 50-megahertz transducer with a penetration of approximately 4 mm was used to produce a magnified image of the anterior segment. The Molteno tube was visualized without complication in all of these cases.

Anterior Eye Segment↗