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Optometry & Vision Science:
doi: 10.1097/OPX.0000000000000311
OVS Announces

OVS Announces

Free Access
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IN THIS ISSUE:

Increasing Accessibility for Low-Vision Patients
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Low vision is any chronic form of vision impairment, not correctable by glasses or contact lenses, adversely affecting daily living. Visual accessibility makes an environment, device, or display usable by those with low vision. Our Prentice medalist describes the challenges of visual accessibility to these people. Our author is a world research leader in low vision, and he gives us clear insight into the ways vision science plays an important role in enhancing visual accessibility for people with low vision. In particular, he is now emphasizing and conducting collaborative research in real-world contexts related to architectural accessibility and reading accessibility. (p. 696)

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Editor’s Choice open access

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High Myopia: Candidate Gene Not Implicated
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The association between LUM promoter regions rs3759223 polymorphism and high myopia remains controversial and ambiguous. In an attempt to clarify, our authors performed a meta-analysis of six articles with 1238 cases and 1059 healthy controls. Although their analysis suggests a lack of association with myopia risk, they call for larger well-designed studies to confirm this. (p. 707)

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Project Gullstrand Revisits Refractive Biometry Distribution
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A large biometric data set from autorefraction and optical biometry data (Scheimpflug and partial coherence interferometry) of 1136 right eyes of healthy white subjects was fitted with linear combinations of multivariate Gaussian to create Monte Carlo simulations of the ocular components. The authors found that, although axial length follows a bi-Gaussian distribution, corneal curvature, anterior chamber depth, and lens power do not. This model provides a more accurate description of the refractive distribution and suggests that the general population may be composed of two separate subgroups with different biometric properties. (p. 713)

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What Is Treatment of Myopia Worth to a Patient?
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Because direct utility (value) is hard to measure, utility values are often described in terms of trade-offs (see OVS August 2013 Feature Issue, “Measuring the Patient's Perspective”). Our authors determined two different utility values for 442 Chinese myopic patients (aged 17 to 44 years) scheduled for refractive surgery. The first was TTO (time trade-off in terms of years of life willing to sacrifice for treatment of myopia) and the second was SG (standard gamble) for blindness, that is, the highest risk of blindness, in percentage, they were willing to take for the successful treatment of myopia. The TTO and SG produce similar mean utility values across age, sex, occupation, education, reasons for refractive surgery, and severity and duration of myopia, but there is poor agreement between results for individuals from the two methods. (p. 723)

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Ciliary Muscle and Myopia Development
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Human clinical evidence suggests that the ciliary muscle may be involved in myopia development. To pursue this line of research in a well-established animal model of myopia, the authors studied normal development of guinea pig ciliary muscle dimensions. Ciliary muscle volume increased 2.5-fold during the 90 days required to reach both adult refractive error and axial length. The ciliary muscle appears to undergo active development after birth, as opposed to passively occupying the space between its attachments. Future studies will investigate the processes that lead to the observed increase in muscle volume during normal growth. (p. 730)

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Does Correcting Off-Axis Refractive Error Improve Vision?
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Our authors have a clear answer for us: it is YES. The majority of their 10 emmetropic patients had simple myopic astigmatism 20 degrees off axis in the nasal field. Most astigmatism was between –1 diopter (D) and –2 D. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism with about one Snellen line of improvement with correction of -1.5 D of astigmatism. For those relying on peripheral vision function, for example, those with central visual field loss, the authors feel that peripheral refractive error assessment with an open-field aberrometer, and then correction, may be useful. (p. 740)

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Pterygium Surgery Decisions Based on Residual Astigmatism
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Surgeons know that one of the better strategies to reduce recurrences in pterygium excision is to combine limbo-conjunctival autograft with mitomycin C. However, there are still unanswered questions. What about postoperative astigmatism in these cases?What is the optimal time to reduce it with surgery?Our authors’ study objectively analyzed these issues, and they propose a threshold for surgery benefit in terms of astigmatism reduction that will help make treatment decisions with rational criteria. (p. 747)

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The Consensual Accommodative Response in Unilateral Vision-Impaired Eyes
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Our authors found that simulated (long-wavelength filter-induced) profoundly vision impaired (PVI) eyes displayed similar accommodative response to their fellow sighted eyes when accommodation was elicited by a near target as close as 33 cm to the fellow eye. But above this moderate 3-diopter accommodation demand, the difference between eyes increased. For the evaluation of devices and surgical methods for restoration of accommodation, the potential bias caused by a greater consensual accommodation in the vision-impaired eye of binocularly sighted participants might be significant. (p. 752)

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Macular Function after Ozurdex for Retinal Vein Occlusion
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The authors noted the changes in macular function (central macular thickness, VA, microperimetry, multifocal ERG) after an intravitreal dexamethasone implant (Ozurdex) in 19 patients with macular edema caused by retinal vein occlusion. Although all functions improved at 1 month after treatment, the improvement was lost at 4 months.  The authors suggest that the optimal retreatment interval is less than 6 months from the first injection. (p. 760)

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Counseling Tobacco Use in Optometric Practices
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In a first census survey of Canadian optometrists, the authors found that optometrists are well aware of the impact of smoking on ocular health; however, most do not systematically engage in tobacco use prevention and cessation practices with their patients. They suggest that providing optometrists with tools, including continuing education, may help support patient conversations about the risks of tobacco use and improve public health. (p. 769)

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Improving Gaze Position Measures
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According to our authors, the Hirschberg ratio (HR), calculated theoretically from the individual’s corneal curvature and anterior chamber depth, should be used instead of the population-average HR. The calculated ratio improves accuracy of gaze position estimated using first Purkinje image-based eye trackers. Intersubject variability in corneal curvature and anterior chamber depth can explain most of the intersubject variance in HR. (p. 778)

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Clinical Methods for Distance Heterophoria Compared
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The authors examined the repeatability of the modified Thorington test for distance heterophoria, comparing it with the Von Graefe, Maddox rod, and cover test methods. The authors found it quick and simple to perform and showed the best repeatability and the best agreement with the cover test. The authors recommend the Thorington test for the clinical measurement of distance heterophoria. (p. 786)

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Novel Approach to Assist with Scleral Contact Lens Curvature and Lasik Surgery
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Using anterior segment optical coherence tomography (AS-OCT) images, easily available software, and simple mathematical concepts, the authors have devised a method for analyzing anterior scleral curvature with “considerable reliability and accuracy.”  The sclera is not spherical (i.e., not rotationally symmetric), and AS-OCT provides information for designing scleral lenses or selecting the suction ring during LASIK surgery. (p. 793)

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A Marker for Preclinical and Severity of Keratoconus
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Our authors' results suggest that corneal thickness is an important marker for detecting both subclinical keratoconus and different levels of disease severity. They propose that the results provide clinicians with guidance in terms of which parameters to assess when detecting subclinical keratoconus and potentially limit the occurrence of postoperative ectasia. (p. 803)

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Soft Contact Lens Fits Benefit from a New Model
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Despite their long history, soft contact lenses and the factors governing their fit are still poorly understood. Computer modeling allows the systematic analysis of the effect of varying ocular and lens design parameters. Our author used a spreadsheet-based computer model incorporating a novel ellipto-conical corneal model to calculate soft contact lens edge strain as a predictor of lens tightness. The model provides some interesting insights about soft lens fit. (p. e167)

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Fundus Lesion Masquerades as Optic Disc
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The authors report a fundus lesion resembling pseudoduplication of the optic disc in eyes with pathologic myopia. This presentation has not been reported previously in the literature. Their three patients, discovered in a sample of 128 highly myopic eyes, showed an acquired pseudoduplication of the optic disc. Enhanced depth imaging optical coherence tomography and indocyanine green angiography revealed characteristic scleral excavation and a short ciliary artery in the pseudodisc, indicating that the vessel may play a role in changing scleral contour in pathologic myopia. (p. e177)

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Somatic DNA Alterations of Genes in Uveal Melanoma
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Somatic DNA alterations are now recognized to drive tumorigenesis. Using exome sequencing, our authors were able to identify the spectrum of somatic mutations in an Asian Indian patient with uveal melanoma (UM) without metastasis. Statistical and bioinformatic analyses identified somatic mutations and their putative associations with UM. Thirty-one somatic mutations (25 amino acid altering) in protein-coding (exonic) regions were detected in the UM patient. Of the amino acid–altering somatic mutations, 16 mutations were predicted to be candidate mutations relevant to UM. Somatic mutations in GNAQ and SF3B1 genes were probable drivers of UM in the patient, as earlier reported in some white patients. (p. e185)

Copyright © 2014 American Academy of Optometry

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