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Simon K Law

Publications and source records attributed to Simon K Law.

9 recordsLinked to original sources
PubMed2006

Pointwise linear regression analysis for detection of visual field progression with absolute versus corrected threshold sensitivities.

PURPOSE: To compare the performance of point-wise linear regression analysis (PLR) with total deviation (TD) versus corrected or pattern deviation (PD) threshold sensitivities for detection of visual field progression. METHODS: Four hundred two eyes (402 patients) enrolled in the Advanced Glaucoma Intervention Study (AGIS) were selected. Criteria for progression according to PLR were a slope or=2 worsening points within the same Glaucoma Hemifield Test cluster. PLR was performed on TD and PD threshold sensitivities and compared to clinical evaluation. Eyes were classified into three groups based on mean deviation (MD): mild (MD>or=-6 dB), moderately advanced (-6 dB>MD>or=-12 dB), and advanced (MD<-12 dB) glaucoma. RESULTS: Visual field progression was observed in 154 (38%), 85 (21%), and 175 (44%) eyes, according to PLR(TD) and PLR(PD), and clinical evaluation. The pair-wise agreement between clinicians and PLR(TD) was significantly greater than that of clinicians and PLR(PD) (kappa=0.48, 95% CI: 0.44-0.52 vs. kappa=0.31, 95% CI: 0.27-0.35). Agreement between PLR(TD) and PLR(PD) decreased with increasing glaucoma severity: kappa (95% CI)=0.60 (0.52-0.67), 0.41 (0.35-0.47), and 0.33 (0.27-0.40) for mild, moderately advanced, and advanced glaucoma, respectively. CONCLUSIONS: Point-wise linear regression analysis on TD threshold sensitivities performed better than the same analysis on PD when clinical evaluation was used as a reference. Agreement between the two methods was less in moderately advanced and advanced glaucoma.

Adult↗
PubMed2005

Feasibility and efficacy of a mass switch from latanoprost to bimatoprost in glaucoma patients in a prepaid Health Maintenance Organization.

OBJECTIVE: To assess the feasibility of an automatic switch of a large number of patients with glaucoma or suspicion of glaucoma from latanoprost to bimatoprost, and to compare the efficacy of the 2 prostaglandin analogs before and after the switch. DESIGN: Retrospective nonrandomized comparison. PARTICIPANTS: Forty-three thousand four hundred forty-one California patients and 538 patients at one Southern California clinical facility of a nationwide prepaid health maintenance organization (HMO) who were on either prostaglandin between March 2002 and December 2003 (21 months). METHODS: Beginning in April 2002, patients on latanoprost were systemically switched to bimatoprost by the HMO pharmacy service after obtaining approval from the entire ophthalmology staff. PART 1: computerized dispensing records of California patients were retrieved. PART 2: medical records of patients at one clinical facility were reviewed. MAIN OUTCOME MEASURES: Rates of switching or switching back from one prostaglandin to another, intraocular pressure (IOP) control, and intolerability. RESULTS: PART 1: 17847 patients initially received latanoprost. Of them, 84.8% were switched from latanoprost to bimatoprost, and 13.0% were switched back to latanoprost. Twenty-five thousand five hundred ninety-four patients were started on bimatoprost without previous experience with latanoprost. Of them, 8.6% were later switched to latanoprost use instead. Patients who had previous experience with latanoprost had a statistically significantly higher rate of switching back to latanoprost after a period of bimatoprost use when compared with those who had no prior experience with latanoprost (13.0% vs. 8.6%, respectively; P<0.0001). PART 2: 309 patients were switched from latanoprost to bimatoprost. The mean IOP reduction of 0.51+/-2.77 mmHg (95% confidence interval, 0.20-0.82) after the switch was statistically significant (P = 0.001). Forty-one patients (13.3%) had a decrease of >3 mmHg of IOP. The statistical significance of the IOP reduction after the switch remains in the monotherapy group (P = 0.005) but not in the multitherapy group (P = 0.058). Thirty-three patients (10.7%) who were switched from latanoprost to bimatoprost discontinued bimatoprost and resumed latanoprost. CONCLUSION: A systematic pharmacy-level switch from latanoprost to bimatoprost in a nationwide HMO achieved a high switch rate, with little switching back. There was a small but statistically significant reduction in mean IOP after the switch. An appreciable proportion of patients switched had a clinically significant reduction of IOP.

Adolescent↗
PubMed2005

Comparison of safety and efficacy between silicone and polypropylene Ahmed glaucoma valves in refractory glaucoma.

OBJECTIVE: To compare the safety and efficacy of polypropylene and silicone Ahmed glaucoma valves (AGVs) over 1 year of follow-up. DESIGN: Retrospective comparative study. PARTICIPANTS: Fifty consecutive patients with polypropylene and 49 consecutive patients with silicone AGV implantation. METHODS: Our hospital instituted a formulary conversion of the glaucoma aqueous drainage device from polypropylene to silicone AGVs in January 2003. We reviewed the polypropylene AGVs within 7 months before and the silicone AGVs within 7 months after the date of conversion performed on patients with glaucoma refractory to medical treatment and filtering procedures, without previous drainage devices or cyclodestructive procedures, and with a minimum of 12 months' follow-up. Surgical success was defined as an intraocular pressure (IOP) reduction of > or =20% and a final IOP of >5 and <22 mmHg, without additional surgical intervention for IOP control, loss of light perception, or serious complications. MAIN OUTCOME MEASURES: The 2 groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. RESULTS: Significant IOP reductions occurred after polypropylene AGV implantation (from 32.4+/-11.3 mmHg to 16.5+/-6.9 mmHg, P<0.0001) and silicone AGV implantation (from 32.6+/-12.6 mmHg to 14.7+/-6.9 mmHg, P<0.0001). The silicone group had a lower mean IOP than the polypropylene group at all postoperative visits, but the differences were significant only at 3 months postoperatively (P = 0.014). In addition, the silicone group was associated with a rate of insufficient IOP control as the reason of failure (IOP of > or =22 mmHg or IOP reduction of <20%) lower (4.1%) than that of the polypropylene group (20.0%, P = 0.015), but a rate of non-tube related serious complications (16.3%) higher than that of the polypropylene AGV (4.0%, P = 0.042). CONCLUSION: After 1 year of follow-up, the silicone AGV is at least as effective as the polypropylene AGV in IOP reduction but may be associated with a higher rate of complications. These differences are important for surgeons converting to use of the silicone AGV in patients with glaucoma refractory to other forms of treatment.

Aged↗
PubMed2004

Identifying early glaucoma with optical coherence tomography.

PURPOSE: To evaluate performance of optical coherence tomography (OCT) for detection of early glaucoma. DESIGN: Observational case-control study. METHODS SETTING: University-based tertiary care center. STUDY POPULATION: One eye from 50 normals, 42 glaucoma suspects, and 59 early glaucoma patients meeting the following criteria: visual field (VF) mean deviation > or =-6.00 dB, age > or =40 years, spherical refractive error < or =5 diopters, astigmatism < or =3 diopters, and visual acuity > or =20/30. OBSERVATION PROCEDURE: Early glaucoma by VF (EGVF) was described as repeatable abnormal achromatic VFs based on predefined criteria. Glaucoma suspects (GS) were defined as presence of glaucomatous disk appearance with normal achromatic VFs. OUTCOME MEASURES: Average nerve fiber layer thickness (NFLT) and NFLT in each of four quadrants and 12 clock-hour sectors. Receiver operating characteristic curves and sensitivity and specificity were used to assess the performance of OCT. RESULTS: Average NFLT was 128.4 +/- 15.4, 102.0 +/- 25.4, and 86.5 +/- 31.5 microm in normal, GS, and EGVF eyes, respectively. Normal eyes were different from both glaucoma groups (P <.001); NFLT in the superior quadrant and at the 11 o'clock position had the highest area under the receiver operating characteristic curve (.840 and.933) in the GS and EGVF groups (P =.03). The sensitivity of the OCT for detection of glaucoma was 71% and 85% for the GS and EGVF groups with specificity fixed at 90%. CONCLUSION: The OCT discriminates well between eyes with early perimetric glaucoma and normal eyes. However, its performance is less adequate in eyes with suspicious disk and normal VFs.

Adult↗
PubMed2004

Optic disk appearance in advanced age-related macular degeneration.

PURPOSE: To describe and quantify the appearance of the optic disk in patients with advanced age-related macular degeneration (ARMD). DESIGN: Retrospective comparative study. METHODS: A total of 316 charts were reviewed. From these, 45 subjects with advanced ARMD (defined as geographic atrophy or disciform scar) in at least one eye were enrolled. Patients with glaucoma or glaucoma visual field defects were excluded. The probability of glaucomatous optic nerve damage was scored by evaluation of stereoscopic optic disk photographs in a masked fashion, according to a predefined evaluation scale and measured with confocal ophthalmoscopy (Heidelberg Retinal Tomograph; HRT). The area of macular involvement was measured in units of disk area. The optic disk evaluation scores and HRT measurements of a group of eyes with a large area of ARMD were compared with their fellow eyes with smaller areas of ARMD. The correlations between the area of macular involvement with the optic disk evaluation scores and HRT measurements were analyzed. MAIN OUTCOME MEASURES: The optic disk evaluation scores and the HRT measurements between study groups. RESULTS: Eyes with larger areas of ARMD had optic disks that were more likely to be classified as glaucomatous by clinical evaluation (3.45 +/- 0.23 vs 3.05 +/- 0.18, P =.015) and by HRT imaging analysis (-0.995 +/- 0.423 vs -0.376 +/- 0.249, P =.030) than the fellow eyes with smaller areas of ARMD. For eyes with six or more disk areas of ARMD, larger areas of ARMD correlated with a higher cup/disk ratio (P =.022), smaller neuroretinal rim area (P =.022), and glaucomatous classification (P =.040) with HRT discriminant function analysis. CONCLUSIONS: Eyes with large areas of geographic or diskiform ARMD have optic disk structural alterations that resemble glaucomatous optic neuropathy. This should be taken into consideration when evaluating patients with ARMD for glaucomatous damage.

Aged↗
PubMed2004

Baerveldt-350 implant versus Ahmed valve for refractory glaucoma: a case-controlled comparison.

PURPOSE: To compare the efficacy of intraocular pressure (IOP) control of the Baerveldt-350 implant with tube ligature and the Ahmed valve in patients with refractory glaucoma. PATIENTS AND METHODS: Four hundred seventy glaucoma drainage device procedures from July 1995 to July 2001 (6 years) were reviewed retrospectively. Thirty-two cases of Baerveldt-350 implantation performed in patients with glaucoma refractory to medical treatment and filtering procedures, without previous drainage device or cyclodestructive procedures, and with a minimum of 1-year follow-up were identified. Thirty-two cases of Ahmed valve implantation were matched case by case with 32 Baerveldt-350 cases for age, race, gender, glaucoma subtype, previous ocular history, preoperative IOP, and surgeon who performed the implantation. The two groups were compared for IOP control, visual outcome, complication rate, and surgical success rate. Surgical success rate was defined as an IOP reduction greater than or equal to 30% and final IOP more than 5 mm Hg and less than 22 mm Hg, without devastating complications. RESULTS: Over a follow-up period of 1 year, no statistically significant differences were detected between the Baerveldt-350 implant versus Ahmed valve for IOP control (12.1 +/- 5.3 mm Hg vs. 13.6 +/- 5.6 mm Hg respectively, at a power of 90% to detect a difference of 3.2 mm Hg between the two groups and P = 0.05), surgical success rate (65.6% vs. 65.6% respectively, complete and qualified combined), postoperative hypotony rate (37.5% vs. 34.4% respectively), and visual acuity changes of more than 1 line in Snellen visual acuity (43.3% vs. 29.0% respectively). CONCLUSION: In a case-controlled comparison, the Baerveldt-350 implant and the Ahmed valve had similar IOP control and surgical outcomes in patients with refractory glaucoma at 1-year follow-up.

Adult↗