Biomedical subjects

Shan C Lin

Publications and source records attributed to Shan C Lin.

4 recordsLinked to original sources

PubMed2007

Primary trabeculectomy surgery performed by residents at a county hospital.

PURPOSE: To evaluate the safety and efficacy of trabeculectomies performed by ophthalmology residents at a metropolitan county hospital, under the supervision of attending physicians. METHODS: A retrospective analysis of resident-performed trabeculectomies at the San Francisco General Hospital from the period of 1994 to 2004 was performed. The preoperative and postoperative ocular data of 50 eyes in 35 patients were evaluated. Of the 50 cases, 47 procedures were performed as primary trabeculectomies and 3 were revisions of trabeculectomies. RESULTS: The average follow-up period was 28.9+/-17.6 months with an intraocular pressure (IOP) decrease from 23.2+/-9.4 mm Hg preoperatively to 11.3+/-4.4 mm Hg at last follow-up, for a mean reduction of 11.9+/-10.5 mm Hg (51.6%) (P<0.0001). Follow-up periods ranged from 3 months to over 6 years. The number of medications required decreased from 3.2+/-1.1 to 0.6+/-0.1 (P<0.0001). Success, defined by a postoperative IOP < or =21 mm Hg or a decreased postoperative IOP of at least 25% from preoperative pressure if the preoperative IOP was already < or =21 mm Hg, was observed in 42 eyes (84%) at last follow-up. Best-corrected visual acuity was stable or improved in 22 eyes (44%) and was noted to decrease 2 or more Snellen lines in 28 eyes (56%). Notable complications included 3 cases (6%) of persistent hypotony (IOP<5), 1 case (2%) of late endophthalmitis, and 1 case (2%) of phthisis. Seven eyes (14%) required subsequent penetrating glaucoma procedures due to bleb failure. CONCLUSIONS: Results of this study suggest that the outcomes of trabeculectomies performed by residents at a county hospital can have a high success rate, comparable with previous studies in the literature. Rates of complications are overall similar to those found in the published literature.

Adult↗

PubMed2006

Intraocular pressure and ocular pulse amplitude comparisons in different types of glaucoma using dynamic contour tonometry.

PURPOSE: To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPA) in patients with different types of glaucoma, ocular hypertension (OHT), and normal controls (NC) using dynamic contour tonometry (DCT) and the goldmann applanation tonometry (GAT). METHODS: 906 eyes of 501 adult patients in the following five groups were included in this cross-sectional study: primary open angle glaucoma (POAG), normal tension glaucoma (NTG), Pseudoexfoliative Glaucoma (PXG), OHT, and NC. The following tests were performed simultaneously during a single visit: IOP using DCT and GAT; OPA using DCT and central corneal thickness (CCT) using ultrasound pachymetry. Mixed effects regression models were used to compare the DCT and GAT IOP measurements in the five groups; the effect of CCT on IOP and the relationship between OPA and IOP within each group. RESULTS: DCT consistently had higher IOP values than GAT in POAG, PXG, NTG, and controls (p < 0.001) but not in OHT (p = 0.84). DCT IOP did not change while GAT IOP showed a non-significant increase (p = 0.09) with increased corneal thickness in each group. OPA was found to be highest in OHT (3.61 mmHg) and lowest in the control group (2.86 mmHg) and significantly increased with IOP in all groups. CONCLUSIONS: DCT measures an IOP that is significantly higher than GAT IOP in glaucoma and control subjects but not in ocular hypertensives. Furthermore, the DCT may measure an IOP that is independent of the CCT, which may not be true for the GAT, which increases with the CCT. OPA was highest in OHT and may be affected by the IOP.

Blood Pressure↗

PubMed2006

Dynamic contour tonometry: principle and use.

Interindividual variability of central corneal thickness has been found to be a source of error for conventional Goldmann applanation tonometry. The dynamic contour tonometer represents a potentially new technology for non-invasive and direct intraocular pressure (IOP) measurement, and has been proposed to accurately measure the true IOP irrespective of the corneal thickness. It is based on the principle that when the tip of the device exactly matches the contour of the cornea, the pressure measured by a transducer placed on its tip is an accurate indicator of the true IOP. This device is also capable of measuring the ocular pulse amplitude, a variable that has controversial significance in the diagnosis and management of glaucoma. Even though this technique seems to be very promising, further studies are required to conclusively determine the effectiveness of the dynamic contour tonometer in patients having an abnormal or irregular corneal contour.

Equipment Design↗

PubMed2002

Automated perimetry: a report by the American Academy of Ophthalmology.

OBJECTIVE: The purpose of this document is to summarize and evaluate the effectiveness of new automated perimetry tests and algorithms in diagnosing glaucoma and detecting disease progression. METHODS: A literature search on automated perimetry retrieved over 300 citations from 1994 to 2001, of which 71 were selected as relevant to this assessment. The quality of the evidence obtained from these studies was assessed by the methodologist. RESULTS: The four automated perimetry techniques described in this assessment are short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), high-pass resolution perimetry (HPRP), and motion automated perimetry (MAP). The algorithms described are Swedish interactive threshold algorithm (SITA) and SITA fast. With the exception of SWAP, these techniques and algorithms reduce testing time and inconsistent patient performance when compared with conventional full threshold testing. CONCLUSIONS: Short wavelength automated perimetry detected visual field loss earlier than standard threshold automated perimetry, with a sensitivity and specificity of about 88% and 92% respectively. However, it is a lengthy, demanding test, is sensitive to media opacities, and has a greater magnitude of long-term fluctuation compared with standard threshold automated perimetry, which make it difficult to assess disease progression accurately. When compared to standard threshold automated perimetry, FDT perimetry showed sensitivity and specificity greater than 97% for detecting moderate and advanced glaucoma, and sensitivity of 85% and specificity of 90% for early glaucoma. As FDT perimetry has a short testing time and is resistant to blur and pupil size, it may be a useful screening tool. In a longitudinal study, high-pass resolution perimetry was more effective than standard threshold automated perimetry in monitoring progressive glaucomatous loss, detecting progression at a median of 12 months earlier in 54% of patients studied. Motion automated perimetry demonstrated usefulness in detecting early glaucomatous visual loss in a longitudinal study. Studies on SITA demonstrated greater sensitivity and reproducibility and less intertest variability when compared to standard full threshold testing and a 50% reduction in testing times. A study comparing standard full threshold, SITA, and SITA fast found a sensitivity of 95% for the first two techniques and 93% for SITA fast. Long-term follow-up studies are needed to assess the ability of these techniques to detect progression of glaucoma over time.

Algorithms↗