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The short-term influence of exercise on axial length and intraocular pressure.

ABSTRACT: PURPOSE: The aim of this study is to investigate the short-term influence of a period of dynamic exercise on axial length (AXL) and intraocular pressure (IOP) in young adult subjects. PATIENTS AND METHODS: In all, 20 young adult subjects (10 myopes and 10 emmetropes) participated. Baseline measures of ocular biometrics, IOP and ocular pulse amplitude (OPA) were taken following a 20-min rest period. Subjects then performed 10 min of moderate intensity, low impact dynamic exercise (bicycle ergometry). Measures of ocular biometrics, IOP and OPA were repeated immediately after, and then 5 and 10 min after this exercise task. Systemic blood pressure and pulse rate were also monitored. A repeated measures analysis of variance was used to investigate the changes in the measured parameters. RESULTS: Exercise resulted in significant changes in a range of ocular parameters. A small but significant decrease in AXL was observed following exercise (P<0.0001). The largest change in AXL was noted immediately following exercise (mean decrease -17±10 μm). IOP and OPA also decreased significantly following exercise (P<0.0001). A moderate but significant positive association was found between the changes in AXL and the changes in IOP (r(2)=0.36, P<0.0001). There were no significant differences found between the myopic and emmetropic subjects in the magnitude of changes observed in ocular parameters following exercise. CONCLUSION: The physiological effects of dynamic exercise lead to changes in a range of ocular parameters, including significant reductions in IOP, OPA and decreases in AXL.

SUBMITTER: Read SA

PROVIDER: S-EPMC3178122 | biostudies-other | 2011 Jun

REPOSITORIES: biostudies-other

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Project description:The purpose of this study was to develop a method of estimating pulsatile ocular blood volume (POBV) from measurements taken during an ophthalmic exam, including axial length and using a tonometer capable of measuring intraocular pressure (IOP) and ocular pulse amplitude (OPA). Unpublished OPA data from a previous invasive study was used in the derivation, along with central corneal thickness (CCT) and axial length (AL), as well as IOP from the PASCAL dynamic contour tonometer (DCT) and intracameral (ICM) measurements of IOP for 60 cataract patients. Intracameral mean pressure was set to 15, 20, and 35 mmHg (randomized sequence) in the supine position, using a fluid-filled manometer. IOP and OPA measurements were acquired at each manometric setpoint (DCT and ICM simultaneously). In the current study, ocular rigidity (OR) was estimated using a published significant relationship of OR to the natural log of AL in which OR was invasively measured through fluid injection. Friedenwald's original pressure volume relationship was then used to derive the estimated POBV, delivered to the choroid with each heartbeat as a function of OR, systolic IOP (IOPsys), diastolic IOP (IOPdia), and OPA, according to the derived equation POBV = log (IOPsys/IOPdia) / OR. Linear regression analyses were performed comparing OPA to OR and calculated POBV at each of the three manometric setpoints. POBV was also compared to OPA/IOPdia with all data points combined. Significance threshold was p < 0.05. OR estimated from AL showed a significant positive relationship to OPA for both DCT (p < 0.011) and ICM (p < 0.006) at all three manometric pressure setpoints, with a greater slope for lower IOP. Calculated POBV also showed a significant positive relationship to OPA (p < 0.001) at all three setpoints with greater slope at lower IOP, and a significant negative relationship with IOPdia. In the combined analysis, POBV showed a significant positive relationship to OPA/ IOPdia (p < 0.001) in both ICM and DCT measurements with R2 = 0.9685, and R2 = 0.9589, respectively. POBV provides a straight-forward, clinically applicable method to estimate ocular blood supply noninvasively. Higher IOP in combination with lower OPA results in the lowest values of POBV. The simplified ratio, OPA/ IOPdia, may also provide a useful clinical tool for evaluating changes in ocular blood supply in diseases with a vascular component, such as diabetic retinopathy and normal tension glaucoma. Future studies are warranted.

Project description:PurposeTo test the hypothesis that pterygium presents with both refractive and anatomical changes, especially short axial length.MethodsA retrospective, hospital-based cross-sectional study included 521 eyes from 521 patients who were enrolled through a community survey by Shanghai Heping Eye Hospital was conducted. Patients with primary pterygium in at least 1 eye were considered the pterygium group, and those with normal eyes were considered the nonpterygium group. The prevalence and length of pterygium, refractive characteristics including spherical power, astigmatism, corneal curvature, and anatomical parameters including axial length, anterior chamber depth, endothelial cell density, and corneal thickness were compared between groups.ResultsFive hundred twenty-one eyes of 521 patients (214 men and 307 women) with a mean age of 70.5 ± 7.6 years were included in the study. The prevalence of hyperopia (81.6%, 65.1%, P = 0.001), axial length (23.1 ± 1.2 mm, 24.2 ± 2.4 mm, P < 0.001), anterior chamber depth (2.9 ± 0.3 cm, 3.1 ± 0.4 cm, P = 0.001), flat K value (42.94 ± 2.16 diopters, 43.73 ± 1.48 diopters, P = 0.002), Kmax (51.13 ± 7.74 diopters, 47.49 ± 5.62 diopters, P < 0.001), and spherical power (0.97 ± 2.40 diopters, -0.82 ± 4.40 diopters, P < 0.001) were statistically different between the pterygium and nonpterygium groups. Age (r = -0.21, P = 0.025), corneal astigmatism (r = -0.41, P < 0.001), flat K value (r = -0.39, P < 0.001), and endothelial cell density (r = -0.33, P = 0.001) were all negatively correlated with the length of pterygium. The prevalence of pterygium and severe pterygium over 3 mm were statistically different according to the severity of hyperopia (P < 0.001) and axial length (P < 0.001). Stratified ? analysis showed that axial length, rather than hyperopia, was a related factor to pterygium (odds ratio = 5.23, 95% confidence interval: 2.50-10.93).ConclusionsWe conclude from our study that the prevalence of pterygium is related to small eye size. SDF-1/CXCR4 signaling may play a vital role in pterygium and shorter axial length. Further study focused on SDF-1/CXCR4 signaling will be needed.

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The short-term influence of exercise on axial length and intraocular pressure.

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