Even minimal uncorrected astigmatism can significantly decrease vision and could significantly affect patients’ independence, quality of life and well-being, suggests a new study. Researchers evaluated healthy adult presbyopes who had astigmatism of 0 to -4 D cylinder × 90 degrees and -3 DC × 90, × 180 and × 45 degrees, induced with spectacle lenses, with the mean spherical equivalent compensated to plano, in random order. Visual acuity was assessed binocularly using a computerized test chart at 95-, 50- and 10- percent contrast. Near acuity and reading speed were measured using standardized reading texts. Light scatter was quantified with a C-Quant straylight meter and driving reaction times with a computer simulator. Visual clarity of a mobile phone and computer screen was subjectively rated. Subjective ratings of clarity were compared using the Fisher nonparametric related-sample comparisons with Wilcoxon signed-rank tests for post hoc testing (F).
Distance visual acuity in the 21 volunteers decreased with increasing uncorrected astigmatic power (F=174.50, p<0.001) and at lower contrasts (F=170.77, p<0.001). Near visual acuity and reading speed also decreased with increasing uncorrected astigmatism power (p<0.001). Light scatter was not significantly affected by uncorrected astigmatism (p>0.05); however, the reliability and variability of measurements decreased with increasing uncorrected astigmatic power (p>0.05). Driving simulator performance was largely unaffected by uncorrected astigmatism (p>0.05), although subjective rating of clarity decreased with increasing uncorrected astigmatic power (p<0.001). Uncorrected astigmatism at the 45-degree or 180-degree orientation resulted in worse distance and near visual acuity and subjective-rated clarity than at the 90-degree orientation (p>0.05).
J Cataract Refract Surg 2011;37:454-60
Wolffsohn JS, Bhogal G, Shah S.
Omega-3s Don’t Affect Lipid Composition, Evaporation
Dietary supplementation with omega-3 fatty acids in dry eye has shown no significant effect in meibum lipid composition or aqueous tear evaporation rate. Researchers at the University of Texas Southwestern Medical Center in Dallas investigated the potential effect of dietary supplementation with omega-3 fatty acid on lipid composition of meibum, aqueous tear evaporation and tear volume in patients presenting with dry eye by conducting a pilot, prospective, randomized, double-masked study. Patients with dry eye received a daily dose of fish oil, containing 450 mg of eicosapentaenoic acid, 300 mg of docosahexaenoic acid and 1,000 mg of flaxseed oil (TheraTears Nutrition; Advanced Vision Research, who partially financed the study) for 90 days. At a baseline and a final visit, patients completed the Ocular Surface Disease Index to score subjective symptoms. Slit-lamp examinations, breakup time, corneal staining, Schirmer type I, fluorophotometry, evaporometry and collection of meibomian gland secretion samples for lipid composition analysis were also performed.
A total of 36 patients with dry eye completed the study. At the end of the study, 70 percent of the patients became asymptomatic, whereas for the placebo group 7 percent of the symptomatic patients became asymptomatic. Schirmer testing and fluorophotometry suggested that the omega-3 supplement increased tear secretion. The lipid composition of the samples collected from the omega-3 group was found to be very similar to that from the placebo group. No trends between groups were seen for other objective parameters.
Wojtowicz JC, Butovich I, Uchiyama E, et al.
ICare Safe for Home Use
New research has shown the ICare rebound tonometer to be accurate and reliable in the hands of inexperienced patients using it for home monitoring of intraocular pressure. To assess the feasibility of patients self-administering the device, a trained technician used the ICare rebound tonometer to measure the IOP of the right eye of 100 glaucoma patients. The technician then instructed each patient on use of the ICare tonometer. Each patient then measured his own pressure using the ICare tonometer. Finally, a different technician, who was masked to both of the earlier readings, measured IOP by Goldmann applanation tonometry. Thirty patients repeated the ICare measurement three times (once every five minutes) 20 minutes after the initial IOP measurement.
Of those 100 patients, 82 of the patient ICare and the technician ICare readings were within 3 mmHg of each other, and 75 of the patient ICare and Goldmann applanation tonometry measurements were within 3 mmHg of each other.
J Glaucoma 2011;20:74-9
Asrani S, Chatterjee A, Wallace DK, et al.
AG Valve Yields Fewer Complications Than BG Implant
The Ahmed glaucoma valve (AGV) has shown fewer early and serious postoperative complications associated with its use than the Baerveldt glaucoma implant (BGI). In a study to determine the relative efficacy and complications of the AGV model FP7 (New World Medical) and the BGI model 101-350 (Abbott Medical Optics) in refractory glaucoma, researchers conducted a multicenter, randomized, controlled clinical trial focusing on 276 patients (143 in the AGV group and 133 in the BGI group). Patients 18 to 85 years of age with refractory glaucoma having intraocular pressure of 18 mmHg or more in whom an aqueous shunt was planned were randomized to undergo implantation of either an AGV or a BGI. The primary outcome measure was failure, defined as: IOP >21 mmHg or an IOP not reduced by 20 percent from baseline; IOP ≤5 mmHg; reoperation for glaucoma or removal of implant; or loss of light perception vision. Secondary measures included mean IOP, visual acuity, use of supplemental medical therapy and complications.
Mean preoperative IOP was 31.2 ±11.2 mmHg in the AGV group and 31.8 ±12.5 mmHg in the BGI group (p=0.71). At one year, mean IOP was 15.4 ±5.5 mmHg in the AGV group and 13.2 ±6.8 mmHg in the BGI group (p=0.007). The mean number of glaucoma medications was 1.8 ±1.3 in the AGV group and 1.5 ±1.4 in the BGI group (p=0.071). The cumulative probability of failure was 16.4 percent (standard error, 3.1 percent) in the AGV group and 14 percent (SE, 3.1 percent) in the BGI group at one year (p=0.52). More patients experienced early postoperative complications in the BGI group (n=77; 58 percent) compared with the AGV group (n=61; 43 percent; p=0.016). Serious postoperative complications associated with reoperation, vision loss of ≥two Snellen lines, or both, occurred in 29 patients (20 percent) in the AGV group and in 45 patients (34 percent) in the BGI group (p=0.014).
Budenz DL, Barton K, Feuer WJ, et al.
YAG Shows No Effect Against Pigment Dispersion Syndrome
New research shows that there is no benefit to Nd:YAG laser peripheral iridotomy in preventing progression from pigment dispersion syndrome with ocular hypertension to pigmentary glaucoma within three years of follow-up. In a prospective, randomized, controlled three-year trial, researchers evaluated 116 eyes of 116 patients with PDS and OHT; patients were assigned randomly either to Nd:YAG LPI or to a control group (no laser). The primary outcome measure was conversion to pigmentary glaucoma within three years, based on full-threshold visual field analysis using the Ocular Hypertension Treatment Study criteria. Secondary outcome measures were whether eyes required topical anti-glaucoma medications during the study period, and the time to conversion or medication.
Fifty-seven patients were randomized to undergo laser treatment and 59 were randomized to no laser (controls). Age, gender, spherical equivalent refraction and intraocular pressure at baseline were similar between groups. Outcome data were available for 105 (90 percent) of recruited subjects, 52 in the laser treatment group and 53 in the no-laser treatment group. Patients were followed up for a median of 35.9 months in the laser arm (range, 10 to 36 months) and 35.9 months in the control arm (range, one to 36 months). Eight eyes (15 percent) in the laser group and three eyes (6 percent) in the control group converted to glaucoma in the study period. The proportion of eyes started on medical treatment was similar in the two groups: eight eyes (15 percent) in the laser group and nine eyes (17 percent) in the control group. Survival analyses showed no evidence of any difference in time to VF progression or commencement of topical therapy between the two groups. Cataract extraction was performed on one patient in the laser group and on one patient in the control group during the study period (laser eye at 18 months; control eye at 34 months).
Scott A, Kotecha A, Bunce C, et al