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Volume 3, Number 33
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Monday, August 18, 2003
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| Phacoemulsification
Using the Burst Mode Using the burst mode during nuclear fragment emulsification increases ultrasound (US) efficiency, especially when used for hard cataracts, according to a recent Argentinean study. Researchers at the Instituto de la Visión, University of Buenos Aires, compared the amount of US energy required for burst mode and pulse mode during nuclear fragment emulsification. They retrospectively compared the US time (UST) and effective US power (USP) used by two surgeons. Nuclear fragments were emulsified using the pulse mode in 82 cases (Group 1) and the burst mode in 118 cases (Group 2). The two groups were divided according to nuclear hardness: 0 to 2+ (subgroups 1a and 2a) or 3+ to 4+ (subgroups 1b and 2b). The difference in nuclear hardness between Groups 1 and 2 was not statistically significant. The mean UST and USP were, respectively, 1.64 minutes +/- 0.98 (SD) at 10.53 percent +/- 4.46 percent in subgroup 1a, and 0.56 +/- 0.46 minutes at 10.51 percent +/- 5.80 percent in subgroup 1b. The respective mean UST and USP were 2.94 +/- 1.36 minutes at 15.14 percent +/- 4.49 percent in subgroup 2a, and 0.75 +/- 0.52 minutes at 10.04 percent +/- 3.12 percent in subgroup 2b. The differences between subgroups were statistically significant except between subgroups 2a and 2b. |
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SOURCE: Badoza D, Mendy JF, Ganly M. Phacoemulsification using the burst mode. J Cataract Refract Surg 2003;29:1101-5. |
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| Highly Precise
Eye Length Measurements in Children The partial coherence interferometry technique of measuring axial length in young children provides reproducible, extraordinarily precise eye length measurements and should enable novel approaches to study eye growth and refractive development, according to researchers at Philadelphia’s Children’s Hospital, Scheie Eye Institute at the University of Pennsylvania and the Pennsylvania College of Optometry. Authors of the study (who have no proprietary interest in the partial coherence interferometer) measured the right eye of 64 subjects (mean age 8.4 years, age range 3.4 to 12.9 years) with best-corrected visual acuity >/= 20/30. Subjects fixated monocularly on the collimated light pattern from a laser diode (the alignment beam), and the operator used a video monitor to align the corneal reflection in the optical path. Clinicians measured axial length during an 0.8-second scan using interference patterns from a collimated short coherence superluminescence diode aligned coaxially with the laser diode. They obtained five series of 16 readings each, then calculated the average axial length for each of the five series of readings. Within-subject precision of axial length measurements was high, with an overall SE of measurement of 8 µm for individual subjects across the five sessions (95 percent confidence interval, +/-16 µm). Subgroup analysis showed that sex, age, spherical equivalent and refractive error exerted statistically significant effects on precision, but all of the differences among subgroups were 3 µm or less and likely to be insignificant clinically. Axial length measured by partial coherence interferometry varied systematically, with factors known to influence eye length (i.e., age and refractive error), further validating the measurement method. |
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SOURCES: Quinn GE, Francis EL, Nipper KS, et al. Highly precise eye length measurements in children aged three through twelve years. Arch Ophthalmol 2003;121(7):985-90. |
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| Edible Mushroom
Lectin Inhibits Human RPE Cell Proliferation British researchers have discovered that human retinal pigment epithelium (RPE) binds to lectin of an edible mushroom, Agaricus bisporus, inhibiting proliferation in vitro without apparent cytotoxicity. A. bisporus lectin may therefore be a potential antiproliferative agent in the prevention and treatment of proliferative vitreoretinopathy and other nonocular anomalous wound healing processes. The RPE plays a major role in the development of proliferative vitreoretinopathy. Researchers used fluorescein isothiocyanate-labeled A. bisporus lectin to study binding of lectin to cultured human RPE. They measured the effect of a 24-hour exposure of A. bisporus lectin on RPE proliferation using (methyl-3H)-thymidine incorporation into DNA. They assessed toxicity studies using morphologic evaluation, trypan blue exclusion and a cell viability assay. The lectin bound to RPE cells and was inhibited by preincubation of lectin with asialomucin; it caused a dose-dependent inhibition of RPE proliferation (one-way ANOVA, F = 94.470) that was partially reversible on removal of the lectin. Compared with controls, cells remained viable and researchers observed no morphological changes or trypan blue staining in RPE exposed to A. bisporus lectin. |
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SOURCE: Kent D, Sheridan CM, Tomkinson HA, et al. Edible mushroom (Agaricus bisporus) lectin inhibits human retinal pigment epithelial cell proliferation in vitro. Wound Repair Regen 2003;11(4):285-91. |
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| A New Index to
Measure Accuracy of Refractive Operations Using a standardized "index of error" may give clinicians a more accurate means of evaluating refractive surgery outcomes, according to a recent study by the University of Tampere in Finland. Authors of the study suggest that using the index in clinical praxis would help avoid inaccuracies that might otherwise go unnoticed if only the basic values, such as uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and haze, are used in postoperative evaluation. By combining information given by the cross-cylinder form of surgically induced refractive change and basic methods of vector analysis, the researchers constructed a new index as a tool to evaluate postoperatively the changes achieved by refractive surgery. This index gives easily understandable numerical values and takes into account changes in both spherical refraction and astigmatism. The physicians demonstrated the use of this index in two study populations consisting of 20 consecutive eyes operated on using two different excimer lasers, Meditec MEL60 and MEL70, respectively. Although postoperative UCVA and BCVA were better in the MEL70 group, the difference of photorefractive keratectomy (PRK) for combined astigmatism and myopia was not statistically significant. Comparison of the changes in refraction achieved by the two lasers indicated that the MEL60 was more accurate; this was also seen when comparing the total index of error between the two groups. |
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SOURCE: Suominen S, Pietilä J, Mäkinen P, Uusitalo H. A new index to measure the accuracy of refractive operations. Acta Ophthalmol Scand 2003;81(4):336-42. |
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| Association Between
Cataract and Mortality Among Older Adults Older persons with cataract, in particular those who decline surgery, have an increased risk of death, according to researchers at the University of Alabama at Birmingham. Previous research has suggested that persons with cataract have an increased risk of death. Researchers in this cohort study aimed to compare the mortality experience of patients with cataract who elect surgery, patients with cataract who do not elect surgery and patients without cataract independent of potentially confounding risk factors. Of 384 patients of ophthalmology and optometry clinics affiliated with the Callahan Eye Foundation Hospital in Birmingham, 286 had cataract, and 200 of these elected to have cataract surgery. Patients with cataract who elected or did not elect to have surgery had significantly higher mortality (crude mortality rate ratio [MRR] 3.9, 95 percent CI 1.5 to 9.8) compared to those without cataract (MRR 7.3, 95 percent CI 2.8 to 19.1) After adjustment for age, gender, race, education, chronic medical conditions, smoking, drinking, depression and cognitive status, the no-surgery cataract group had an elevated mortality rate (MRR 3.2, 95 percent CI 1.2 to 9.0), compared to the no-cataract group, with a borderline elevation in MR for the surgery group (MRR 2.0, 95 percent CI 0.8 to 5.9). Limiting the study population to non-diabetics or those without concurrent eye conditions (glaucoma, maculopathy, retinopathy) did not materially influence the adjusted MRRs, although the precision of the estimates was reduced. The study’s results support the hypothesis that age-related cataract reflects systemic as well as localized ocular disease. |
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SOURCE: McGwin G, Owsley C, Guathreaux S. The association between cataract and mortality among older adults. Ophthalm Epidemiol 2003;10(2),107-19. |
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BRIEFLY
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