Retinal nerve changes in patients with tremor dominant and akinetic rigid Parkinson's disease.

Parkinson disease is a multisystem neurodegenerative disease which involves not only basal ganglia and extrapyramidal system but also many other neurologic systems such as retinal ganglion cells. Optical coherence tomography (OCT) is a non-invasive method for assessment of retinal nerve fiber layer (RNFL) thickness and its changes in different diseases. To evaluate the RNFL thickness in patients with Parkinson disease (PD), we performed OCT in patients with PD and compared it with a control group. From October 2010 to July 2011, 27 PD patients (54 eyes) and 25 healthy persons (50 eyes) were entered to this analytical cross-sectional study according to the defined criteria. PD patients were categorized into two groups "akinetic rigid (AR) and tremor dominant (TD)". RNFL was divided into four quadrants and was assessed by OCT. Afterwards; the data were analyzed by bivariate and multivariate models. The RNFL thickness in PD was significantly lower than the control group. Also, the thicknesses of inferior and nasal quadrants of RNFL in TD group were significantly more than AR group. According to these findings, OCT can be used as a sensitive and objective marker for assessment of early neurodegenerative changes of PD and early initiation of neuroprotective treatments. Future studies with adequate sample sizes are recommended to investigate interactions between age, distribution of the disease and type of PD as well as the effects of individual factors.

Intraocular pressure after exposure to moderate altitude.

BACKGROUND: To study intraocular pressure (IOP) alteration in healthy individuals following a rapid effortless increase in altitude from 1900 m above sea level (ASL) to 3740 m ASL. METHODS: Intraocular pressure, blood pressure, pulse rate, and arterial oxygen tension were determined in both eyes of healthy volunteers at the lower altitude. Participants were taken to a higher altitude of 3740 m ASL (1840-m altitude gain) via gondola lift, which took 30 minutes. All measurements were repeated at the higher altitude. Pearson and Spearman correlation analysis was conducted to assess the correlations among the variables. A paired t-test and linear regression were also used to compare IOP before and after ascending. The accepted level of significance for all tests was p <0.05. RESULTS: Fifty-four healthy volunteers participated in the study. Four eyes of three subjects with IOP higher than 21 mmHg were excluded. Intraocular pressure ± SD (range) decreased from 14.9 ± 2.6 mmHg (9-21 mmHg) to 14.3 ± 2.4 mmHg (11-20 mmHg) (p = 0.02) after the ascent. Arterial oxygen saturation decreased from 95.4 % to 91.5 % (p < 0.001). Neither of the participants complained of any ocular or systemic symptoms during or after ascending to the higher altitude. Mean IOP, before and after ascending, was positively correlated with systolic blood pressure before and after the increase in altitude (Pearson correlation coefficient, 0.41, p = 0.002 and Pearson correlation coefficient, 0.37, p = 0.006, respectively). Intraocular pressure changes did not correlate with age, pulse rate, or arterial oxygen saturation. CONCLUSION: A rapid, effortless increase in altitude (over a moderate range in altitude) decreases IOP in healthy individuals. The observed decrease may not be clinically significant; however, it shows the versatility of IOP control mechanisms in response to alteration in altitude and temperature.

Effect of Photorefractive Keratectomy on Optic Nerve Head Topography and Retinal Nerve Fiber Layer Thickness Measured by Heidelberg Retina Tomograph 3.

PURPOSE: To determine whether photorefractive keratectomy (PRK) has a significant effect on optic nerve head (ONH) parameters and peripapillary retinal nerve fiber layer (RNFL) thickness measured by the Heidelberg Retina Tomograph 3 (Heidelberg Engineering GmbH, Heidelberg, Germany) in eyes with low to moderate myopia. METHODS: This prospective, interventional case series, includes 43 consecutive myopic eyes which were assessed on the day of PRK and 3 months postoperatively using the HRT3. Among the stereometric parameters, we compared disc area, linear cup disc ratio, cup shape measure, global rim area, global rim volume, RNFL height variation contour and mean RNFL thickness; out of the Glaucoma Probability Score (GPS) we assessed changes in global value, rim steepness temporal/superior, and temporal/inferior, as well as cup size and cup depth before and after PRK. RESULTS: Mean refractive error before and after PRK were -3.24 ± 1.31 and -0.20 ± 0.42 diopters, respectively. No significant change occurred in disc area, linear cup disc ratio, cup shape measure, rim area and rim volume among the stereometric parameters; and in rim steepness temporal/superior and rim steepness temporal/inferior in the GPS before and after PRK using the default average keratometry. However, RNFL height variation contour, mean RNFL thickness, and cup size and depth were significantly altered after PRK (P < 0.05). CONCLUSION: PRK can affect some HRT3 parameters. Although the most important stereometric parameters for differentiating normal, suspect or glaucomatous patients such as rim and cup measurements in stereometric parameters were not changed.