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Indian Journal of Ophthalmology
Water drinking test and angle closure glaucoma Dear Editor, Kumar et al.[1] in their article titled “severe visual loss following water load for transabdominal ultrasound” have described a patient, who is a known ocular hypertensive, developing raised intraocular pressure (IOP) following waterloading. Authors have mentioned the possibility of visual loss in such patients and highlighted the importance of slow ingestion of 500 ml of water, mandatory 90 min postprocedural observation period and prompt referral to ophthalmologist if patient develops visual complaints. We appreciate the author’s effort and research work.
Vol. 63 No. 2 Access this article online
Quick Response Code:
Website: www.ijo.in DOI: 10.4103/0301-4738.154410 PMID: ***
Comment on: Central corneal thickness and intraocular pressure in premature and full-term newborns
By stressing outflow facility, the water drinking test (WDT)[2] might reveal elevations in IOP that are ordinarily experienced during 24‑h period. Recent work on WDT points to its potential as a predictor of peak IOP, and thus IOP fluctuations. Physiology of WDT is not fully understood. Autonomic nervous stimulation and/or increased episcleral venous pressure (EVP) remain possible mechanisms. Systemic hypertension occurs following water drinking in autonomic failure, in quadriplegia, after cardiac transplantation and to a lesser extent in older healthy individuals. Sympathetic stimulation is thought to produce this response and may also modify IOP via yet‑to‑be‑determined mechanisms. Alternatively WDT elevates EVP and causes a transient period of negative aqueous outflow. This is likely the result of reduced outflow facility from a decreased pressure gradient across the trabecular meshwork, but other mechanism have been suggested. EVP may be implicated in both IOP instability and glaucoma progression as it is elevated in both open angle glaucoma and normal tension glaucoma patients. The WDT might unmask pathologic EVP effects.
Dear Sir, We have read the article entitled “assessment of the central corneal thickness (CCT) and intraocular pressure (IOP) in premature and full‑term newborns” with great interest.[1] Thanks to the authors for the contribution to the literature with a well‑designed study. The authors concluded that premature infants‑almost significantly (P = 0.07) have slightly thicker corneas than full‑term infants, however, have no high IOP measurements.
Arora et al.,[3] observed a significant increase in choroidal thickness (CT)[3] and a decrease in anterior chamber depth after WDT in angle closure eyes but not in open angle eyes. Even though, IOP increase, after WDT was not fully explained by CT increase, based on their observation they have suggested the dynamic behavior of the choroid, may play a role in angle closure process. In conclusion, WDT may cause raised IOP by angle closure mechanism in susceptible eyes.
In the literature, gestational age in the studies evaluating the CCT and IOP in premature and full‑term newborns ranges between 29.8 and 32 weeks.[3‑5] However in the Muslubas’s study, it was 36.3 ± 0.9 weeks, almost 5 weeks later than similar studies. It is known that corneal hydration decreases day by day until birth. The authors reported no significant differences in CCT and IOP between premature newborns and full‑term infants. Kirwan et al. reported that babies born at near 31 weeks have very thick corneas and shows statistically significant decrease to term.[3] Ng et al. measured the IOP at mean 26.1 and 46.4 weeks of postconceptional age and reported IOP is significantly and negatively associated with postconceptional age.[4] Ricci also reported that IOP in premature infants shows a significant reduction in the first month of life.[5] Therefore, their finding could be estimated because of the high gestational age. They stated this for CCT in discussion, but it is also applicable for IOP measurement.
N Venugopal Neuro‑ophthalmology Clinic, AG Eye Hospital, Trichy, Tamil Nadu, India Correspondence to: Dr. N Venugopal, Flat No.: 19, Mathuram Apartment, Officer’s Colony, Puthur, Trichy, Tamil Nadu, India. E‑mail: [email protected]
References 1. Kumar H, Dewan T, Vashisht S, Prasad A. Severe visual loss following waterload for transabdominal ultrasound. Indian J Ophthalmol 2013;61:612. 2. Goldberg I, Clement CI. The water drinking test. Am J Ophthalmol 2010;150:447‑9. 3. Arora KS, Jefferys JL, Maul EA, Quigley HA. Choroidal thickness change after water drinking is greater in angle closure than in open angle eyes. Invest Ophthalmol Vis Sci 2012;53:6393‑402.
Corneal thickness has gained clinical interest since Ocular Hypertension Treatment Study that identified CCT as an important risk factor in glaucoma. It is known that large corneal thickness is present at birth in premature newborns, which leads to loss of corneal transparency and it appears to be related to increased corneal hydration.[2] It is shown that the reduction of hydration after birth is related to a fast development of endothelium and Na/K ATPase‑dependent pump, and this leads decrease in corneal thickness.[2]
Broman et al. assessed the influence of axial length, corneal astigmatism, hysteresis and refractive error on IOP measurement with different tonometers.[6] The authors concluded that some of those characteristics such as hysteresis, corneal astigmatism and corneal curvature influenced the tonometers significantly, and all should be taken consideration among the variables that affect IOP assessment and susceptibility to glaucoma damage. This study covers adult’s eye, and it can be speculated that effect of these parameters on IOP probably is much more in an immature eye such as premature newborn. Hereby does the
Copyright of Indian Journal of Ophthalmology is the property of Medknow Publications & Media Pvt. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Indian Journal of Ophthalmology
Water drinking test and angle closure glaucoma Dear Editor, Kumar et al.[1] in their article titled “severe visual loss following water load for transabdominal ultrasound” have described a patient, who is a known ocular hypertensive, developing raised intraocular pressure (IOP) following waterloading. Authors have mentioned the possibility of visual loss in such patients and highlighted the importance of slow ingestion of 500 ml of water, mandatory 90 min postprocedural observation period and prompt referral to ophthalmologist if patient develops visual complaints. We appreciate the author’s effort and research work.
Vol. 63 No. 2 Access this article online
Quick Response Code:
Website: www.ijo.in DOI: 10.4103/0301-4738.154410 PMID: ***
Comment on: Central corneal thickness and intraocular pressure in premature and full-term newborns
By stressing outflow facility, the water drinking test (WDT)[2] might reveal elevations in IOP that are ordinarily experienced during 24‑h period. Recent work on WDT points to its potential as a predictor of peak IOP, and thus IOP fluctuations. Physiology of WDT is not fully understood. Autonomic nervous stimulation and/or increased episcleral venous pressure (EVP) remain possible mechanisms. Systemic hypertension occurs following water drinking in autonomic failure, in quadriplegia, after cardiac transplantation and to a lesser extent in older healthy individuals. Sympathetic stimulation is thought to produce this response and may also modify IOP via yet‑to‑be‑determined mechanisms. Alternatively WDT elevates EVP and causes a transient period of negative aqueous outflow. This is likely the result of reduced outflow facility from a decreased pressure gradient across the trabecular meshwork, but other mechanism have been suggested. EVP may be implicated in both IOP instability and glaucoma progression as it is elevated in both open angle glaucoma and normal tension glaucoma patients. The WDT might unmask pathologic EVP effects.
Dear Sir, We have read the article entitled “assessment of the central corneal thickness (CCT) and intraocular pressure (IOP) in premature and full‑term newborns” with great interest.[1] Thanks to the authors for the contribution to the literature with a well‑designed study. The authors concluded that premature infants‑almost significantly (P = 0.07) have slightly thicker corneas than full‑term infants, however, have no high IOP measurements.
Arora et al.,[3] observed a significant increase in choroidal thickness (CT)[3] and a decrease in anterior chamber depth after WDT in angle closure eyes but not in open angle eyes. Even though, IOP increase, after WDT was not fully explained by CT increase, based on their observation they have suggested the dynamic behavior of the choroid, may play a role in angle closure process. In conclusion, WDT may cause raised IOP by angle closure mechanism in susceptible eyes.
In the literature, gestational age in the studies evaluating the CCT and IOP in premature and full‑term newborns ranges between 29.8 and 32 weeks.[3‑5] However in the Muslubas’s study, it was 36.3 ± 0.9 weeks, almost 5 weeks later than similar studies. It is known that corneal hydration decreases day by day until birth. The authors reported no significant differences in CCT and IOP between premature newborns and full‑term infants. Kirwan et al. reported that babies born at near 31 weeks have very thick corneas and shows statistically significant decrease to term.[3] Ng et al. measured the IOP at mean 26.1 and 46.4 weeks of postconceptional age and reported IOP is significantly and negatively associated with postconceptional age.[4] Ricci also reported that IOP in premature infants shows a significant reduction in the first month of life.[5] Therefore, their finding could be estimated because of the high gestational age. They stated this for CCT in discussion, but it is also applicable for IOP measurement.
N Venugopal Neuro‑ophthalmology Clinic, AG Eye Hospital, Trichy, Tamil Nadu, India Correspondence to: Dr. N Venugopal, Flat No.: 19, Mathuram Apartment, Officer’s Colony, Puthur, Trichy, Tamil Nadu, India. E‑mail: [email protected]
References 1. Kumar H, Dewan T, Vashisht S, Prasad A. Severe visual loss following waterload for transabdominal ultrasound. Indian J Ophthalmol 2013;61:612. 2. Goldberg I, Clement CI. The water drinking test. Am J Ophthalmol 2010;150:447‑9. 3. Arora KS, Jefferys JL, Maul EA, Quigley HA. Choroidal thickness change after water drinking is greater in angle closure than in open angle eyes. Invest Ophthalmol Vis Sci 2012;53:6393‑402.
Corneal thickness has gained clinical interest since Ocular Hypertension Treatment Study that identified CCT as an important risk factor in glaucoma. It is known that large corneal thickness is present at birth in premature newborns, which leads to loss of corneal transparency and it appears to be related to increased corneal hydration.[2] It is shown that the reduction of hydration after birth is related to a fast development of endothelium and Na/K ATPase‑dependent pump, and this leads decrease in corneal thickness.[2]
Broman et al. assessed the influence of axial length, corneal astigmatism, hysteresis and refractive error on IOP measurement with different tonometers.[6] The authors concluded that some of those characteristics such as hysteresis, corneal astigmatism and corneal curvature influenced the tonometers significantly, and all should be taken consideration among the variables that affect IOP assessment and susceptibility to glaucoma damage. This study covers adult’s eye, and it can be speculated that effect of these parameters on IOP probably is much more in an immature eye such as premature newborn. Hereby does the
Copyright of Indian Journal of Ophthalmology is the property of Medknow Publications & Media Pvt. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
