Volume 4, Number 44

Monday, November 1, 2004

In this issue: (click heading to view article)
		Ascorbic Acid Reversibly Inhibits Proliferation of RPE Cells
		Diagnosis of Vestibular Imbalance in the Blink of an Eye
		Clinical Correlations of Posterior Vitreous Detachment
		OCT Findings in Myopic Traction Maculopathy
		Foveal Sensitivity and Fixation Stability Before and After Macular Translocation with 360-Degree Retinotomy
		Briefly

Ascorbic Acid Reversibly Inhibits Proliferation of RPE Cells Proliferation control in adult retinal pigment epithelial (ARPE) cells is an essential factor in the clinical management of proliferative vitreoretinopathy (PVR). Factors that inhibit PVR and that are without toxic potential are therefore of interest in controlling proliferation. A recent German study investigated whether high intraocular ascorbic acid levels are a physiological modulator of ARPE proliferation. Researchers incubated ARPE cells in vitro with increasing concentrations of ascorbic acid (0.5 to 4 mmol, pH 7.4). They assayed cell proliferation by the bromide-deoxy-uridine (BrdU) assay, and replaced the culture medium containing ascorbic acid with normal culture medium; they then measured the recovery of proliferation after 24 hours. TUNEL assays and fluorescence analysis cell-counter (FAC) enabled researchers to distinguish among proliferation inhibition, apoptosis, necrosis and recovery of proliferation. Results showed that ascorbic acid significantly inhibits ARPE cell proliferation when present in concentrations above 2 mmol. Proliferation resumed in all ARPE cell cultures after pre-incubation with ascorbic acid, indicating that direct toxicity of ascorbic acid is a negligible factor. The time-point and extent of recovery in proliferation depended on the initial ascorbic acid concentration. FAC on apoptosis markers showed some induction of apoptosis and necrosis after incubation with 4 mmol ascorbic acid. The authors determined that ascorbic acid has a dose-dependent influence on the proliferation of vital ARPE cells, which possibly reflects the role of ascorbic acid at a physiological level within the vitreous cavity in preventing PVR. They believe that their findings may encourage the development of new strategies for clinical treatment of PVR.

SOURCE: Heckelen A, Hermel M, Kondring B, Schrage NF. Ascorbic acid reversibly inhibits proliferation of retinal pigment epithelial cells. Acta Ophthalmol Scand 2004;82(5):564-8.

Diagnosis of Vestibular Imbalance in the Blink of an Eye The authors of this study found, in a previous study, that blinks in healthy volunteers always triggered ocular torsion quick phases during dynamic roll movements of the head. Based on this observation, they hypothesized that blinks in patients with a vestibular tone imbalance would also trigger torsional quick phases. Using video-oculography with a fixation target, investigators recorded the ocular torsion position of the left eye of 37 participants while they made voluntary blinks once every six to 10 seconds. The participants were recruited from four groups: two age groups of healthy volunteers with a mean +/- SD age of 32 +/- 4 (nine subjects) and 65 +/- 11 years (nine subjects); patients with a unilateral vestibular disorder in an acute state (12 subjects aged 53 +/- 17 years); and those in a persisting state in which spontaneous nystagmus had already faded (nine subjects aged 65 +/- 13 years). In the control groups of healthy volunteers, blinks triggered no or only small quick phases on the order of 0.1 degrees. In both patient groups blinks always triggered quick phases with significantly higher amplitudes of 1.85 +/- 1.02 degrees and were followed by exponentially decaying slow-phases with time constants on the order of one to two seconds. Patients in the persisting state clearly differed from patients in the acute state in that their torsional spontaneous nystagmus had already vanished because of vestibular compensation. These two groups, however, did not show a great difference in terms of the effect of blinks on ocular torsion. The investigators always observed torsional quick phases with the upper pole of the eye beating away from the side of the lesion. Based on this data, authors of the study concluded that ocular torsion recordings during blinks can be used as a simple clinical test for a vestibular tone imbalance, particularly during a persisting failure in which spontaneous nystagmus has resolved and can therefore no longer be used for diagnosis.

SOURCE: Schneider E, Glasauer S, Dieterich M, et al. Diagnosis of vestibular imbalance in the blink of an eye. Neurol 2004;63(7):1209-16.

Clinical Correlations of Posterior Vitreous Detachment Investigators at the University of Iowa evaluated the frequency of and the factors primarily and secondarily associated with posterior vitreous detachment (PVD). They aimed to correlate the presence of PVD with various demographic and ophthalmic entities. In a clinical prospective observational cohort study, 1,481 subjects (740 women, 741 men) with a mean age of 63.45 +/- 14.97 years (mean +/- SD; range, 10.3 to 94.9 years) and a mean spherical equivalent refractive error of +0.68 +/- 2.13 dpt (range, -14.25 to +13.50 dpt) were examined. Investigators assessed the presence of PVD by indirect and direct ophthalmoscopy, by fundus biomicroscopy and by using a Hruby lens upon pharmacologically dilated pupils. Main outcome measures were frequency of PVD, association with age, refractive error, cataract surgery, diabetes mellitus, arterial hypertension, history of ocular trauma, vitreous hemorrhage, various retinal disorders, nonarteritic anterior ischemic optic neuropathy (AION) and open-angle glaucoma. Results showed that the occurrence of PVD was significantly correlated with increasing age, myopic refractive error, female gender and surgical aphakia. PVD occurred significantly more often bilaterally than unilaterally, and patients with unilateral PVD were significantly younger than the patients with bilateral PVD. PVD was seen significantly less frequently in AION than in the remaining study population. The frequency of PVD was lower in eyes with than without diabetic retinopathy, optic disc neovascularization and retinal neovascularization. Researchers found no significant association between the presence of PVD and macular hole, macular edema, retinal vascular occlusive disorders, age-related macular degeneration and open-angle glaucoma. These data confirm some of the findings of previous smaller and retrospective studies of PVD. They also provide new information that the authors believe may be helpful in understanding of the pathophysiology of PVD and its role in the pathogenesis of various retinal and optic disc lesions.

SOURCE: Hayreh SS, Jonas JB. Posterior vitreous detachment: clinical correlations. Ophthalmologica 2004;218(5):333-43.

OCT Findings in Myopic Traction Maculopathy A consecutive observational case series by the Vitreoretinal Service of Verona, Italy, described the features and incidence of epiretinal traction and related retinal damage in degenerative myopia. Researchers retrospectively reviewed medical records and optical coherence tomography (OCT) findings of 218 eyes with high myopia of 121 consecutive patients to detect the incidence and features of epiretinal traction-related macular damage. Degree of myopia ranged from -8 to -26 spherical equivalent (mean +/- SD, -16.93 +/- 5.74). Mean +/- SD axial length was 29.75 +/- 2.12 mm. Excluding eyes with possibly confounding features, 125 eyes were analyzed. Of the 125 eyes, 58 (46.4 percent) had epiretinal traction and 43 (34.4 percent) had retinal damage. Macular retinoschisis was the most frequent form of macular damage and occurred in 25 eyes (58 percent), followed by retinal thickening, lamellar hole and shallow retinal detachment. Investigators believe that epiretinal traction is a frequent finding in degenerative myopia and, particularly if it is associated with the presence of staphyloma, can generate a form of macular damage unique to eyes with high myopia. They believe that this damage can affect up to one-third of these eyes, and that it should be considered as a separate cause of visual loss easily detected in its early stages by OCT.

SOURCE: Panozzo G, Mercanti A. Optical coherence tomography findings in myopic traction maculopathy. Arch Ophthalmol 2004;122(10):1455-60.

Foveal Sensitivity and Fixation Stability Before and After Macular Translocation with 360-Degree Retinotomy Microperimetry using scanning laser ophthalmoscopy (SLO) can be used to investigate foveal function before and after macular translocation with 360-degree retinotomy and to predict postoperative visual acuity, according to a study by Japan’s Osaka Rosai Hospital, and Osaka University Medical School. Macular translocation with 360-degree retinotomy and simultaneous torsional muscle surgery were performed on 25 eyes of 25 patients with choroidal neovascularization. Researchers calculated the index of foveal sensitivity and the index of fixation stability before and after surgery from the microperimetric data. They compared the preoperative index of foveal sensitivity and index of fixation stability with postoperative index of foveal sensitivity and index of fixation stability, respectively. They calculated correlations of preoperative index of foveal sensitivity and index of fixation stability with the visual acuity after the translocation surgery (VApost). Index of foveal sensitivity increased in 14 (56 percent) of 25 eyes. index of fixation stability improved in 10 (40 percent) of 25 eyes. The preoperative index of foveal sensitivity and VApost were moderately correlated, while the preoperative index of fixation stability and VApost were highly correlated.

SOURCE: Oyagi T, Fujikado T, Hosohata J, et al. Foveal sensitivity and fixation stability before and after macular translocation with 360-degree retinotomy. Retina 2004;24(4):548-55.

BRIEFLY ANNUAL SURVEY OF COMPLICATIONS OF FOLDABLE IOLS RELEASED. Members of the American Society of Cataract and Refractive Surgery and the European Society of Cataract and Refractive Surgeons recently received the sixth annual survey of complications associated with foldable intraocular lenses (IOLs) requiring explantation or secondary intervention. The survey evaluated pre-operative data on visual acuity, patient signs and symptoms and complications requiring IOL removal; complications were then tabulated for each of the following major foldable IOL groups: three-piece monofocal silicone, three-piece hydrophobic acrylic, one-piece hydrophobic acrylic with haptics, three-piece hydrophilic acrylic (hydrogel), one-piece hydrophilic acrylic (hydrogel), one-piece plate-type silicone, three-piece multifocal silicone and Collamer. Investigators received 273 completed surveys for evaluation. Responses showed that dislocation/decentration, incorrect lens power, IOL calcification and glare/optical aberrations were the most common reasons for removing foldable IOLs. Good surgical technique, accurate IOL power measurements and high manufacturing standards for foldable IOL materials and designs were the most important factors in avoiding complications with foldable IOLs. B&L LAUNCHES NEW PHACO SOFTWARE. Bausch & Lomb has launched its Millennium Custom Control Software (CCS), a new software program for its Millennium microsurgical phacoemulsification platform. The phaco platform combines the benefits of a lower frequency phaco tip with hyperpulse power modulation for "hyper-cool" phaco energy delivery and more desirable surgical outcomes. The new software will provide a broader range of programmable settings, which support a variety of surgical techniques from standard phaco to bimanual cataract surgery. Its hyperpulse technology (0 to 120 pps) has an adjustable duty cycle ranging from 10 percent to 90 percent, and its waveform phaco modulation technology provides improved balance and coordination with irrigation, aspiration and ultrasound pulses, further reducing ultrasonic energy delivered to the eye. For more information on the new software, go to www.bausch.com or call 1-800-338-2020. CRYSTALENS NOW AVAILABLE IN QUARTER-DIOPTER STEPS. Eyeonics, Inc., has received FDA approval to market its crystalens accommodating IOL in quarter-diopter steps. The crystalens is the only FDA-approved accommodating IOL in the United States. The company believes that the expanded choice of powers will assist surgeons in providing the best possible visual outcomes for their patients who are seeking a continuous range of vision with more freedom from spectacles. The 0.25D lenses will be available to credentialed crystalens surgeons on November 1, 2004. HEIDELBERG RECEIVES FDA CLEARANCE FOR FIRST CORNEA LASER MICROSCOPE. Heidelberg Engineering recently announced that it has received FDA clearance for the Rostock Cornea Module, the key component for its confocal laser microscope. The new product can image and measure corneal structures and diseases that were previously difficult, or even impossible, to see. The Rostock Cornea Module is the first FDA-cleared microscope using laser scanning technology for directly imaging a patient"s cornea. It displays magnified images of the internal structures of the cornea, enabling the clinician to directly view the cell layers and individual cells in real-time. This may prove especially important for recognizing parasitic infections which are affecting long term contact lens wearers in increasing numbers. The cornea module connects directly with the HRT II, Heidelberg’s laser imaging instrument for glaucoma. For more information, go to www.heidelbergengineering.de.

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