Optometry and Vision Sciences - Research Publications
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ItemA Comparison of Perimetric Results from a Tablet Perimeter and Humphrey Field Analyzer in Glaucoma Patients(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2016-11)PURPOSE: To determine the correlation between the perimetric outcomes from perimetry software Melbourne Rapid Fields (MRF) run on an Apple iPad tablet and those from the Humphrey Field Analyzer (HFA). METHODS: The MRF software was designed with features including variable fixation and fast thresholding using Bayes logic. Here, we report a cross-sectional study on 90 eyes from 90 participants: 12 had normal optic nerves and 78 had glaucoma with various degrees of visual field loss (41 mild and 37 moderate-severe). Exclusion criteria were patients with worse than 20/40 vision or recent intraocular surgery. The visual field outcomes of MRF were compared against those returned from the HFA 24-2 SITA standard. Participants were tested twice on the MRF to establish test-retest repeatability. RESULTS: The test durations were shorter on MRF than HFA (5.7 ± 0.1 vs. 6.3 ± 0.1 minutes, P < 0.001). MRF showed a high level of concordance in its outcomes with HFA (intraclass coefficient [ICC] = 0.93 for mean defect [MD] and 0.86 for pattern deviation [PD]) although the MRF tended to give a less negative MD (1.4 dB bias) compared with the HFA. MRF also showed levels of test-retest reliability comparable to HFA (ICC = 0.93 for MD and 0.89 for PD, 95% limits of agreement -4.5 to 4.3 dB). CONCLUSION: The perimetry results from the MRF have a strong correlation to the HFA outcomes. MRF also has test-retest reliability comparable to HFA. TRANSLATIONAL RELEVANCE: Portable tablet perimetry may allow accurate assessment of visual field when standard perimetry machines are unavailable or unsuitable.
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ItemIncrease in mitochondrial DNA mutations impairs retinal function and renders the retina vulnerable to injury(WILEY, 2011-08)Mouse models that accumulate high levels of mitochondrial DNA (mtDNA) mutations owing to impairments in mitochondrial polymerase γ (PolG) proofreading function have been shown to develop phenotypes consistent with accelerated aging. As increase in mtDNA mutations and aging are risk factors for neurodegenerative diseases, we sought to determine whether increase in mtDNA mutations renders neurons more vulnerable to injury. We therefore examined the in vivo functional activity of retinal neurons and their ability to cope with stress in transgenic mice harboring a neural-targeted mutant PolG gene with an impaired proofreading capability (Kasahara, et al. (2006) Mol Psychiatry11(6):577-93, 523). We confirmed that the retina of these transgenic mice have increased mtDNA deletions and point mutations and decreased expression of mitochondrial oxidative phosphorylation enzymes. Associated with these changes, the PolG transgenic mice demonstrated accelerated age-related loss in retinal function as measured by dark-adapted electroretinogram, particularly in the inner and middle retina. Furthermore, the retinal ganglion cell-dominant inner retinal function in PolG transgenic mice showed greater vulnerability to injury induced by raised intraocular pressure, an insult known to produce mechanical, metabolic, and oxidative stress in the retina. These findings indicate that an accumulation of mtDNA mutations is associated with impairment in neural function and reduced capacity of neurons to resist external stress in vivo, suggesting a potential mechanism whereby aging central nervous system can become more vulnerable to neurodegeneration.
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ItemFunctional Changes in the Retina during and after Acute Intraocular Pressure Elevation in Mice(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2009-12)PURPOSE: To examine retinal function using the full-field electroretinogram (ERG) during and after acute intraocular pressure (IOP) elevation in wild-type mice. METHODS: IOP was elevated by anterior chamber cannulation in wild-type C57/BL6 mice. The pressure-function relationship was determined by IOP elevation in steps from baseline to 80 mm Hg. The rate of functional recovery was assessed for 60 minutes after an IOP spike of 50 mm Hg for 30 minutes. During and immediately after IOP elevation, scotopic ERG signals were recorded in response to dim and bright flashes (-4.54, -2.23, and 0.34 log cd x s x m(-2)) and analyzed for photoreceptoral (a-wave), ON-bipolar (b-wave), oscillatory potentials (OPs), and scotopic threshold responses (positive [p]STR/negative [n] STR). A full ERG protocol was collected 2 days before and 7 days after the single 50-mm Hg IOP spike. RESULTS: The pSTR was most sensitive to IOP elevation with 50% amplitude loss (mu) at 41 mm Hg (mu, 95% confidence limits (CL): 37.7, 45.6) followed by nSTR at 45 mm Hg (95% CL: 41.0, 49.1). pSTR was significantly more sensitive than the b-wave (95% CL: 41.4, 49.1), a-wave (95% CL: 47.6, 55.3), and OPs (95% CL: 49.6, 59.2). pSTR showed slower recovery immediately after the 50 mm Hg spike compared with the b-wave (P = 0.02). One week after the 50-mm Hg spike, pSTR (-30% +/- 6%, P < 0.001) and OP (-27% +/- 2%, P < 0.001) amplitudes were reduced, whereas other components were unaffected. CONCLUSIONS: The STR in mice is more sensitive to acute IOP elevation and recovers slower than other ERG components. Reduction in pSTR and OP amplitude at 1 week suggests persistent impairment of inner retinal function can occur after a single IOP spike.