CLINICAL SCIENCE
Impact of Valsalva Maneuver on Corneal Morphology and Anterior Chamber Parameters Gökhan Pekel, MD,* Semra Acer, MD,* Ramazan Yagci, MD,* Hüseyin Kaya, MD,* and Evre Pekel, MD†
Purpose: Our aim was to examine the influence of the Valsalva maneuver (VM) on corneal morphology and anterior chamber parameters.
Methods: This prospective observational study included 35 eyes of 35 healthy volunteers. One of the eyes of each subject was selected randomly. The keratometry (K), pachymetry, corneal volume, iridocorneal angle, anterior chamber depth, anterior chamber volume, and corneal wave front measurements (high-order aberration, low-order aberration, total root mean square) were performed with the Pentacam HR (Oculus, Wetzlar, Germany).
Results: The subjects were aged between 22 and 41 years. There were 24 men (69%) and 11 women (31%). The VM did not have any significant influence on K-flat and K-average values (P . 0.05), but it decreased K-steep values significantly (P = 0.006). The VM did not have any significant impact on low-order aberrations and total root mean square parameters (P . 0.05), but it increased high-order aberrations significantly (P = 0.008). The central corneal thickness and corneal volume decreased significantly during the VM (P , 0.05). The iridocorneal angle, anterior chamber depth, and anterior chamber volume decreased markedly during the VM (P , 0.001).
Conclusions: The VM has some influence on corneal morphology and anterior chamber parameters, so that it should be considered during anterior segment examinations and operations. Key Words: Valsalva maneuver, corneal thickness, corneal wave front, keratometry, anterior chamber depth (Cornea 2014;33:271–273)
T
he Valsalva maneuver (VM) is performed by a forceful exhalation attempt against a closed airway. The VM is frequently performed during daily activities, such as lifting something, doing physical exercise, vomiting, and coughing.1–3 The VM is also a diagnostic technique in cardiology practice.4 During the VM, the intrathoracic pressure increases, Received for publication September 4, 2013; revision received October 23, 2013; accepted October 28, 2013. Published online ahead of print January 21, 2014. From the *Department of Ophthalmology, Pamukkale University, Denizli, Turkey; and †Department of Ophthalmology, Denizli State Hospital, Eye Clinic, Denizli, Turkey. The authors have no funding or conflicts of interest to disclose. Reprints: Gökhan Pekel, Department of Ophthalmology, Pamukkale University, Denizli 20070, Turkey (e-mail: [email protected]). Copyright © 2014 by Lippincott Williams & Wilkins
Cornea Volume 33, Number 3, March 2014
venous blood returning to the heart decreases, left ventricular volume decreases, and pulse pressure decreases.5 These physiological responses also affect vascular ocular structures.5,6 The nonvascular cornea might be affected secondary to the changes in the ocular vascular structures and anterior chamber. The VM has some effects on the anterior chamber. The VM can cause a significant narrowing of the iridocorneal angle and a shallowing of the central anterior chamber.7 During the VM, iris thickness is increased.8 Liu et al9 investigated the effects of breath holding on corneal biomechanical properties, such as corneal hysteresis and corneal resistance factor, and found no significant influence of the VM on these parameters. We wanted to do a further investigation about the impact of the VM on corneal morphology, refraction, and wave front. The VM might affect clinical measurements and applications. During ophthalmological examinations, patients often hold their breath and perform the VM involuntarily. Unfamiliarity with procedures and anxiety are also related to this attitude.9 In this study, we aimed to investigate the influence of the VM on the cornea, either by direct effects on the cornea or by secondary effects of anterior chamber and iridocorneal angle narrowing. It was reported that the VM could affect intraocular pressure (IOP) because of increased intrathoracic pressure and decreased ocular venous return.5 Also, we wanted to examine the effects of possible IOP changes on corneal morphology during the VM. Because exact measurements are necessary in making a diagnosis and performing operations in corneal disorders, all the factors such as the VM that might have an impact on the measurements must be revealed.
METHODS Thirty-five eyes of 35 healthy volunteers were included in this prospective observational study. The study was conducted in accordance with the ethical standards of the Declaration of Helsinki and was approved by the Institutional Ethical Committee. One of the eyes of each subject was selected randomly. All the subjects underwent an ophthalmic examination including autorefractometer measurement, visual acuity assessment, biomicroscopy, air-puff tonometer, indirect retinoscopy, and corneal topography. Exclusion criteria were any ocular surgery, any systemic disease, and any ocular diseases except for mild refractive disorders. The subjects had refractive errors between 21.50 and +1.50 diopters (D) spherical equivalent. Volunteers were excluded if they had any www.corneajrnl.com |
271
Cornea Volume 33, Number 3, March 2014
Pekel et al
physical disorder that would prevent them from performing a VM. The VM was performed with expiratory pressure ranging between 35 and 40 mmHg by blowing through the mouthpiece attached to a manometer during the examination. The examinations were performed in the phase 1 of the VM. The keratometry (K), pachymetry, corneal volume (CV), iridocorneal angle, anterior chamber depth (ACD), anterior chamber volume (ACV), and corneal wave front measurements were performed with the Pentacam HR (Oculus, Wetzlar, Germany). Because the scan time of the Pentacam HR is approximately 2 seconds, it is suitable for doing examinations in the phase 1 of the VM that lasts 5 seconds. The keratometry readings were divided into 3 components as K-steep, K-flat, and K-average. The pachymetry value was accepted as the central (apex) corneal thickness (CCT). The CV represents the CV in a diameter of 10 mm around the apex. The ACD was accepted as the depth from the endothelium of the corneal apex to the anterior lens surface. The corneal wave front analysis included high-order, low-order, and total aberrations that were represented as the root mean square (RMS). For statistical analysis, SPSS 17.0 software for Windows (SPSS Inc, Chicago, IL) was used to analyze outcomes. P values ,0.05 were considered to be statistically significant. The paired samples t test was used for comparison of the parameters studied before and during the VM.
RESULTS Thirty-five eyes of 35 healthy volunteers were examined. The subjects were aged 22 to 41 years. The mean age of the patients was 29.0 6 4.7 years. There were 24 men (69%) and 11 women (31%). Sixteen right eyes (46%) and 19 left eyes (54%) were included for the analysis. The effects of the VM on keratometry readings, corneal aberrations, pachymetry, CV, and anterior chamber parameters are shown in Table 1. The VM did not have any significant influence on keratometry (K)-flat and K-average values, but it decreased K-steep values significantly. The VM did not have any significant impact on root mean square (RMS) low-order aberrations (LOAs) and RMS-total parameters, but it increased RMS high-order aberrations (HOAs) significantly. The iridocorneal angle, anterior chamber depth (ACD), anterior chamber volume (ACV), central corneal thickness (CCT), and corneal volume (CV) parameters were significantly decreased during the VM. We repeated the examinations in most of the patients (n = 24) after 10 seconds from the end of the VM and noticed that all the altered parameters such as the ACD, ACV, iridocorneal angle, CCT, CV, K-steep, and RMS-HOA returned to the baseline values.
DISCUSSION The normal physiological response of the VM consists of 4 phases.10 The first 2 phases last approximately 15 seconds, and most of the ophthalmological studies had examined the effects of the VM on ocular structures in these 2 phases. In the first phase (5 seconds), as the intrathoracic pressure rises, the blood in the pulmonary circulation is forced to move into the left atrium, and this causes a mild increase in stroke
272
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TABLE 1. The Effects of the VM on Keratometry Readings, Corneal Aberrations, Pachymetry, Corneal Volume, and Anterior Chamber Parameters Are Shown Keratometry readings K-steep, D K-flat, D K-average, D Corneal aberrations RMS-HOA, mm RMS-LOA, mm RMS-total, mm Pachymetry, CV CCT, mm CV, mm3 AC parameters ACD, mm ACV, mm3 Angle, degrees
P
Resting Position
VM
43.75 6 1.23 42.73 6 1.24 43.24 6 1.22
43.65 6 1.16 42.79 6 1.22 43.23 6 1.17
0.006 0.08 0.44
0.33 6 0.10 1.22 6 0.42 1.26 6 0.43
0.42 6 0.19 1.23 6 0.54 1.30 6 0.56
0.008 0.79 0.45
549.1 6 30.2 61.00 6 3.46
542.3 6 29.8 59.95 6 3.71
0.01 0.008
3.09 6 0.22 187.3 6 28.6 38.8 6 4.1
3.03 6 0.22 177.1 6 26.9 36.4 6 5.3
,0.001 ,0.001 ,0.001
AC, anterior chamber; angle, iridocorneal angle.
volume.10,11 In the second phase (10 seconds), the return of systemic blood to the heart is decreased because of the increased intrathoracic pressure; therefore, the output of the heart is reduced, stroke volume falls, and reflex tachycardia occurs.10,11 Because the examinations done using modern eye instruments are completed in approximately 5 seconds, it is meaningful to examine the effects of phase 1 VM, if we want to reveal the influence of the VM on ocular measurements. It would be expected that as the anterior chamber and iridocorneal angle become narrower, this might push the cornea anteriorly to some extent, which increases the K values, during the VM. However, in this study, the VM did not have any significant influence on K-flat and K-average values, but it decreased K-steep values statistically significantly. This relatively little change in the mean steep K reading does not seem to have a huge clinical effect, but it has some importance in showing that the VM could make a reversible change in the corneal curvature to some extent. There are only a few studies about the effects of the VM on the cornea in the literature. It was reported that breath holding did not have any significant impact on corneal biomechanical properties.9 In this study, we did a further investigation of the cornea by measuring morphological and refractive parameters. Both CCT and CV decreased significantly during the VM. The possible reasons for this effect might be a thinning of the tear film or mechanical stretching of the cornea during the VM. It would be expected that as the CCT decreases, the CV also decreases, but the CV parameter reflects a larger corneal area (10-mm diameter). The Pentacam HR calculates the corneal wave front in its entirety (both anterior and posterior corneal surfaces). The VM did not have any significant impact on RMS-LOA and RMStotal parameters, but it increased RMS-HOA significantly. Generally, corneal HOAs occur because of laser-assisted in situ keratomileusis (LASIK), laser-assisted subepithelial keratectomy (LASEK), decentered corneal grafts, and keratoconus.12–14 Ó 2014 Lippincott Williams & Wilkins
Cornea Volume 33, Number 3, March 2014
Although it is not so important in daily life, HOAs can have an impact on the quality of vision during the VM. But, it is important to instruct refractive surgery candidates not to perform a VM during corneal wave front measurements. In this study, it was found that the ACD, ACV, and iridocorneal angle parameters were significantly decreased during a VM. Our results confirmed the results of the previous studies.7,8 Wang et al7 thought that the shallowing of the ACD might be caused by the forward movement of the iridolenticular diaphragm by a thickening of the ciliary body and choroid during the VM. Falcão et al15 reported that a VM does not change the choroidal thickness at the posterior pole. But an increase in the volume of the anterior part of the choroid seems to be a better explanation of anterior segment changes during a VM. Although we did not examine IOP changes, some studies reported that the IOP increased during a VM.5,16 Actually, most patients could not reach a 35-mmHg VM pressure that was chosen in this study, during an ophthalmological examination or operation. As an example, during defecation in the squatting position, intrathoracic pressures of $40 mmHg are reached.17 However, we observed that large individual pressure differences might occur when performing a VM in a physical activity such as breath holding during ophthalmological examinations. So, to provide standardization between the participants, we determined a certain VM pressure range. In conclusion, the VM causes some alterations in the K (decreases K-steep), corneal wave front (increases HOAs), and corneal morphology (decreases CCT and CV). Also, the findings of our study confirmed those of previous reports that the VM decreases the ACD, ACV, and iridocorneal angle. If we take into consideration these changes, it may be wise to instruct patients to stay in the resting position and avoid the VM, during corneal topography, corneal wave front, diagnostic glaucoma examinations, and intraocular lens calculations. Particular attention should be given to this topic, especially in performing corneal refractive surgery procedures because a VM decreases the CCT and CV to some extent.
Ó 2014 Lippincott Williams & Wilkins
Effects of Valsalva on Anterior Segment
REFERENCES 1. Ladjimi A, Zaouali S, Messaoud R, et al. Valsalva retinopathy induced by labour. Eur J Ophthalmol. 2002;12:336–338. 2. García Fernández M, Navarro JC, Castaño CG. Long-term evolution of valsalva retinopathy: a case series. J Med Case Rep. 2012;6:346. 3. Zebrowska A, Gasior Z, Jastrzebski D. Cardiovascular effects of the Valsalva maneuver during static arm exercise in elite power lifting athletes. Adv Exp Med Biol. 2013;755:335–342. 4. Lembo NJ, Dell’Italia LJ, Crawford MH, et al. Bedside diagnosis of systolic murmurs. N Engl J Med. 1988;318:1572–1578. 5. Rafuse PE, Mills DW, Hooper PL, et al. Effects of Valsalva’s manoeuvre on intraocular pressure. Can J Ophthalmol. 1994;29:73–76. 6. Aykan U, Erdurmus M, Yilmaz B, et al. Intraocular pressure and ocular pulse amplitude variations during the Valsalva maneuver. Graefes Arch Clin Exp Ophthalmol. 2010;248:1183–1186. 7. Wang BS, Xiao L, Liu J, et al. Dynamic changes in anterior segment morphology during the Valsalva maneuver assessed with ultrasound biomicroscopy. Invest Ophthalmol Vis Sci. 2012;53:7286–7289. 8. Dada T, Gupta V, Deepak KK, et al. Narrowing of the anterior chamber angle during Valsalva maneuver: a possible mechanism of angle closure. Eur J Ophthalmol. 2006;16:81–91. 9. Liu WC, Lee SM, Graham AD, et al. Effects of eye rubbing and breath holding on corneal biomechanical properties and intraocular pressure. Cornea. 2011;30:855–860. 10. Porth CJ, Bamrah VS, Tristani FE, et al. The Valsalva maneuver: mechanisms and clinical implications. Heart Lung. 1984;13:507–518. 11. Luster EA, Baumgartner N, Adams WC, et al. Effects of hypovolemia and posture on responses to the Valsalva maneuver. Aviat Space Environ Med. 1996;67:308–313. 12. Sawides L, de Gracia P, Dorronsoro C, et al. Adapting to blur produced by ocular high-order aberrations. J Vis. 2011;11:21. 13. Oliveira CM, Ferreira A, Franco S. Wavefront analysis and Zernike polynomial decomposition for evaluation of corneal optical quality. J Cataract Refract Surg. 2012;38:343–356. 14. Huang H, Yang J, Bao H, et al. Retrospective analysis of changes in the anterior corneal surface after Q value guided LASIK and LASEK in high myopic astigmatism for 3 years. BMC Ophthalmol. 2012;12:15. 15. Falcão M, Vieira M, Brito P, et al. Spectral-domain optical coherence tomography of the choroid during valsalva maneuver. Am J Ophthalmol. 2012;154:687–692.e1. 16. Brody S, Erb C, Veit R, et al. Intraocular pressure changes: the influence of psychological stress and the Valsalva maneuver. Biol Psychol. 1999; 51:43–57. 17. Fedail SS, Harvey RF, Burns-Cox CJ. Abdominal and thoracic pressures during defaecation. Br Med J. 1979;1:91.
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273
Impact of Valsalva Maneuver on Corneal Morphology and Anterior Chamber Parameters Gökhan Pekel, MD,* Semra Acer, MD,* Ramazan Yagci, MD,* Hüseyin Kaya, MD,* and Evre Pekel, MD†
Purpose: Our aim was to examine the influence of the Valsalva maneuver (VM) on corneal morphology and anterior chamber parameters.
Methods: This prospective observational study included 35 eyes of 35 healthy volunteers. One of the eyes of each subject was selected randomly. The keratometry (K), pachymetry, corneal volume, iridocorneal angle, anterior chamber depth, anterior chamber volume, and corneal wave front measurements (high-order aberration, low-order aberration, total root mean square) were performed with the Pentacam HR (Oculus, Wetzlar, Germany).
Results: The subjects were aged between 22 and 41 years. There were 24 men (69%) and 11 women (31%). The VM did not have any significant influence on K-flat and K-average values (P . 0.05), but it decreased K-steep values significantly (P = 0.006). The VM did not have any significant impact on low-order aberrations and total root mean square parameters (P . 0.05), but it increased high-order aberrations significantly (P = 0.008). The central corneal thickness and corneal volume decreased significantly during the VM (P , 0.05). The iridocorneal angle, anterior chamber depth, and anterior chamber volume decreased markedly during the VM (P , 0.001).
Conclusions: The VM has some influence on corneal morphology and anterior chamber parameters, so that it should be considered during anterior segment examinations and operations. Key Words: Valsalva maneuver, corneal thickness, corneal wave front, keratometry, anterior chamber depth (Cornea 2014;33:271–273)
T
he Valsalva maneuver (VM) is performed by a forceful exhalation attempt against a closed airway. The VM is frequently performed during daily activities, such as lifting something, doing physical exercise, vomiting, and coughing.1–3 The VM is also a diagnostic technique in cardiology practice.4 During the VM, the intrathoracic pressure increases, Received for publication September 4, 2013; revision received October 23, 2013; accepted October 28, 2013. Published online ahead of print January 21, 2014. From the *Department of Ophthalmology, Pamukkale University, Denizli, Turkey; and †Department of Ophthalmology, Denizli State Hospital, Eye Clinic, Denizli, Turkey. The authors have no funding or conflicts of interest to disclose. Reprints: Gökhan Pekel, Department of Ophthalmology, Pamukkale University, Denizli 20070, Turkey (e-mail: [email protected]). Copyright © 2014 by Lippincott Williams & Wilkins
Cornea Volume 33, Number 3, March 2014
venous blood returning to the heart decreases, left ventricular volume decreases, and pulse pressure decreases.5 These physiological responses also affect vascular ocular structures.5,6 The nonvascular cornea might be affected secondary to the changes in the ocular vascular structures and anterior chamber. The VM has some effects on the anterior chamber. The VM can cause a significant narrowing of the iridocorneal angle and a shallowing of the central anterior chamber.7 During the VM, iris thickness is increased.8 Liu et al9 investigated the effects of breath holding on corneal biomechanical properties, such as corneal hysteresis and corneal resistance factor, and found no significant influence of the VM on these parameters. We wanted to do a further investigation about the impact of the VM on corneal morphology, refraction, and wave front. The VM might affect clinical measurements and applications. During ophthalmological examinations, patients often hold their breath and perform the VM involuntarily. Unfamiliarity with procedures and anxiety are also related to this attitude.9 In this study, we aimed to investigate the influence of the VM on the cornea, either by direct effects on the cornea or by secondary effects of anterior chamber and iridocorneal angle narrowing. It was reported that the VM could affect intraocular pressure (IOP) because of increased intrathoracic pressure and decreased ocular venous return.5 Also, we wanted to examine the effects of possible IOP changes on corneal morphology during the VM. Because exact measurements are necessary in making a diagnosis and performing operations in corneal disorders, all the factors such as the VM that might have an impact on the measurements must be revealed.
METHODS Thirty-five eyes of 35 healthy volunteers were included in this prospective observational study. The study was conducted in accordance with the ethical standards of the Declaration of Helsinki and was approved by the Institutional Ethical Committee. One of the eyes of each subject was selected randomly. All the subjects underwent an ophthalmic examination including autorefractometer measurement, visual acuity assessment, biomicroscopy, air-puff tonometer, indirect retinoscopy, and corneal topography. Exclusion criteria were any ocular surgery, any systemic disease, and any ocular diseases except for mild refractive disorders. The subjects had refractive errors between 21.50 and +1.50 diopters (D) spherical equivalent. Volunteers were excluded if they had any www.corneajrnl.com |
271
Cornea Volume 33, Number 3, March 2014
Pekel et al
physical disorder that would prevent them from performing a VM. The VM was performed with expiratory pressure ranging between 35 and 40 mmHg by blowing through the mouthpiece attached to a manometer during the examination. The examinations were performed in the phase 1 of the VM. The keratometry (K), pachymetry, corneal volume (CV), iridocorneal angle, anterior chamber depth (ACD), anterior chamber volume (ACV), and corneal wave front measurements were performed with the Pentacam HR (Oculus, Wetzlar, Germany). Because the scan time of the Pentacam HR is approximately 2 seconds, it is suitable for doing examinations in the phase 1 of the VM that lasts 5 seconds. The keratometry readings were divided into 3 components as K-steep, K-flat, and K-average. The pachymetry value was accepted as the central (apex) corneal thickness (CCT). The CV represents the CV in a diameter of 10 mm around the apex. The ACD was accepted as the depth from the endothelium of the corneal apex to the anterior lens surface. The corneal wave front analysis included high-order, low-order, and total aberrations that were represented as the root mean square (RMS). For statistical analysis, SPSS 17.0 software for Windows (SPSS Inc, Chicago, IL) was used to analyze outcomes. P values ,0.05 were considered to be statistically significant. The paired samples t test was used for comparison of the parameters studied before and during the VM.
RESULTS Thirty-five eyes of 35 healthy volunteers were examined. The subjects were aged 22 to 41 years. The mean age of the patients was 29.0 6 4.7 years. There were 24 men (69%) and 11 women (31%). Sixteen right eyes (46%) and 19 left eyes (54%) were included for the analysis. The effects of the VM on keratometry readings, corneal aberrations, pachymetry, CV, and anterior chamber parameters are shown in Table 1. The VM did not have any significant influence on keratometry (K)-flat and K-average values, but it decreased K-steep values significantly. The VM did not have any significant impact on root mean square (RMS) low-order aberrations (LOAs) and RMS-total parameters, but it increased RMS high-order aberrations (HOAs) significantly. The iridocorneal angle, anterior chamber depth (ACD), anterior chamber volume (ACV), central corneal thickness (CCT), and corneal volume (CV) parameters were significantly decreased during the VM. We repeated the examinations in most of the patients (n = 24) after 10 seconds from the end of the VM and noticed that all the altered parameters such as the ACD, ACV, iridocorneal angle, CCT, CV, K-steep, and RMS-HOA returned to the baseline values.
DISCUSSION The normal physiological response of the VM consists of 4 phases.10 The first 2 phases last approximately 15 seconds, and most of the ophthalmological studies had examined the effects of the VM on ocular structures in these 2 phases. In the first phase (5 seconds), as the intrathoracic pressure rises, the blood in the pulmonary circulation is forced to move into the left atrium, and this causes a mild increase in stroke
272
| www.corneajrnl.com
TABLE 1. The Effects of the VM on Keratometry Readings, Corneal Aberrations, Pachymetry, Corneal Volume, and Anterior Chamber Parameters Are Shown Keratometry readings K-steep, D K-flat, D K-average, D Corneal aberrations RMS-HOA, mm RMS-LOA, mm RMS-total, mm Pachymetry, CV CCT, mm CV, mm3 AC parameters ACD, mm ACV, mm3 Angle, degrees
P
Resting Position
VM
43.75 6 1.23 42.73 6 1.24 43.24 6 1.22
43.65 6 1.16 42.79 6 1.22 43.23 6 1.17
0.006 0.08 0.44
0.33 6 0.10 1.22 6 0.42 1.26 6 0.43
0.42 6 0.19 1.23 6 0.54 1.30 6 0.56
0.008 0.79 0.45
549.1 6 30.2 61.00 6 3.46
542.3 6 29.8 59.95 6 3.71
0.01 0.008
3.09 6 0.22 187.3 6 28.6 38.8 6 4.1
3.03 6 0.22 177.1 6 26.9 36.4 6 5.3
,0.001 ,0.001 ,0.001
AC, anterior chamber; angle, iridocorneal angle.
volume.10,11 In the second phase (10 seconds), the return of systemic blood to the heart is decreased because of the increased intrathoracic pressure; therefore, the output of the heart is reduced, stroke volume falls, and reflex tachycardia occurs.10,11 Because the examinations done using modern eye instruments are completed in approximately 5 seconds, it is meaningful to examine the effects of phase 1 VM, if we want to reveal the influence of the VM on ocular measurements. It would be expected that as the anterior chamber and iridocorneal angle become narrower, this might push the cornea anteriorly to some extent, which increases the K values, during the VM. However, in this study, the VM did not have any significant influence on K-flat and K-average values, but it decreased K-steep values statistically significantly. This relatively little change in the mean steep K reading does not seem to have a huge clinical effect, but it has some importance in showing that the VM could make a reversible change in the corneal curvature to some extent. There are only a few studies about the effects of the VM on the cornea in the literature. It was reported that breath holding did not have any significant impact on corneal biomechanical properties.9 In this study, we did a further investigation of the cornea by measuring morphological and refractive parameters. Both CCT and CV decreased significantly during the VM. The possible reasons for this effect might be a thinning of the tear film or mechanical stretching of the cornea during the VM. It would be expected that as the CCT decreases, the CV also decreases, but the CV parameter reflects a larger corneal area (10-mm diameter). The Pentacam HR calculates the corneal wave front in its entirety (both anterior and posterior corneal surfaces). The VM did not have any significant impact on RMS-LOA and RMStotal parameters, but it increased RMS-HOA significantly. Generally, corneal HOAs occur because of laser-assisted in situ keratomileusis (LASIK), laser-assisted subepithelial keratectomy (LASEK), decentered corneal grafts, and keratoconus.12–14 Ó 2014 Lippincott Williams & Wilkins
Cornea Volume 33, Number 3, March 2014
Although it is not so important in daily life, HOAs can have an impact on the quality of vision during the VM. But, it is important to instruct refractive surgery candidates not to perform a VM during corneal wave front measurements. In this study, it was found that the ACD, ACV, and iridocorneal angle parameters were significantly decreased during a VM. Our results confirmed the results of the previous studies.7,8 Wang et al7 thought that the shallowing of the ACD might be caused by the forward movement of the iridolenticular diaphragm by a thickening of the ciliary body and choroid during the VM. Falcão et al15 reported that a VM does not change the choroidal thickness at the posterior pole. But an increase in the volume of the anterior part of the choroid seems to be a better explanation of anterior segment changes during a VM. Although we did not examine IOP changes, some studies reported that the IOP increased during a VM.5,16 Actually, most patients could not reach a 35-mmHg VM pressure that was chosen in this study, during an ophthalmological examination or operation. As an example, during defecation in the squatting position, intrathoracic pressures of $40 mmHg are reached.17 However, we observed that large individual pressure differences might occur when performing a VM in a physical activity such as breath holding during ophthalmological examinations. So, to provide standardization between the participants, we determined a certain VM pressure range. In conclusion, the VM causes some alterations in the K (decreases K-steep), corneal wave front (increases HOAs), and corneal morphology (decreases CCT and CV). Also, the findings of our study confirmed those of previous reports that the VM decreases the ACD, ACV, and iridocorneal angle. If we take into consideration these changes, it may be wise to instruct patients to stay in the resting position and avoid the VM, during corneal topography, corneal wave front, diagnostic glaucoma examinations, and intraocular lens calculations. Particular attention should be given to this topic, especially in performing corneal refractive surgery procedures because a VM decreases the CCT and CV to some extent.
Ó 2014 Lippincott Williams & Wilkins
Effects of Valsalva on Anterior Segment
REFERENCES 1. Ladjimi A, Zaouali S, Messaoud R, et al. Valsalva retinopathy induced by labour. Eur J Ophthalmol. 2002;12:336–338. 2. García Fernández M, Navarro JC, Castaño CG. Long-term evolution of valsalva retinopathy: a case series. J Med Case Rep. 2012;6:346. 3. Zebrowska A, Gasior Z, Jastrzebski D. Cardiovascular effects of the Valsalva maneuver during static arm exercise in elite power lifting athletes. Adv Exp Med Biol. 2013;755:335–342. 4. Lembo NJ, Dell’Italia LJ, Crawford MH, et al. Bedside diagnosis of systolic murmurs. N Engl J Med. 1988;318:1572–1578. 5. Rafuse PE, Mills DW, Hooper PL, et al. Effects of Valsalva’s manoeuvre on intraocular pressure. Can J Ophthalmol. 1994;29:73–76. 6. Aykan U, Erdurmus M, Yilmaz B, et al. Intraocular pressure and ocular pulse amplitude variations during the Valsalva maneuver. Graefes Arch Clin Exp Ophthalmol. 2010;248:1183–1186. 7. Wang BS, Xiao L, Liu J, et al. Dynamic changes in anterior segment morphology during the Valsalva maneuver assessed with ultrasound biomicroscopy. Invest Ophthalmol Vis Sci. 2012;53:7286–7289. 8. Dada T, Gupta V, Deepak KK, et al. Narrowing of the anterior chamber angle during Valsalva maneuver: a possible mechanism of angle closure. Eur J Ophthalmol. 2006;16:81–91. 9. Liu WC, Lee SM, Graham AD, et al. Effects of eye rubbing and breath holding on corneal biomechanical properties and intraocular pressure. Cornea. 2011;30:855–860. 10. Porth CJ, Bamrah VS, Tristani FE, et al. The Valsalva maneuver: mechanisms and clinical implications. Heart Lung. 1984;13:507–518. 11. Luster EA, Baumgartner N, Adams WC, et al. Effects of hypovolemia and posture on responses to the Valsalva maneuver. Aviat Space Environ Med. 1996;67:308–313. 12. Sawides L, de Gracia P, Dorronsoro C, et al. Adapting to blur produced by ocular high-order aberrations. J Vis. 2011;11:21. 13. Oliveira CM, Ferreira A, Franco S. Wavefront analysis and Zernike polynomial decomposition for evaluation of corneal optical quality. J Cataract Refract Surg. 2012;38:343–356. 14. Huang H, Yang J, Bao H, et al. Retrospective analysis of changes in the anterior corneal surface after Q value guided LASIK and LASEK in high myopic astigmatism for 3 years. BMC Ophthalmol. 2012;12:15. 15. Falcão M, Vieira M, Brito P, et al. Spectral-domain optical coherence tomography of the choroid during valsalva maneuver. Am J Ophthalmol. 2012;154:687–692.e1. 16. Brody S, Erb C, Veit R, et al. Intraocular pressure changes: the influence of psychological stress and the Valsalva maneuver. Biol Psychol. 1999; 51:43–57. 17. Fedail SS, Harvey RF, Burns-Cox CJ. Abdominal and thoracic pressures during defaecation. Br Med J. 1979;1:91.
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273
