Renal Failure, 12(2), 109-112 (1990)
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
Intraocular Pressures During High-Flux Hernodialysis J. N. Austin, M. Klein, J. Mishell, S. R. Contiguglia, J. Levy, L. Chan, and J. I . Shapiro Division of Renal Diseases, Department of Medicine University of Colorado School of Medicine, and The Rocky Mountain Kidney Center Denver, Colorado
ABSTRACT
The intraocularpressures of I6 patients with end stage renal failure treated with high-flux dialysis were measured before and during a high-Prn dialysis treatment. The patients were selected so as not to have glaucoma or history of glaucoma. Zntraocular pressures did not change signijkantly in any patients &ring or following a high-jlux hemodialysis treatment. These data suggest that high-flux hemodialysis does not result in increases in intraocular pressure nor does it precipitate acute glaucoma in well-dialyzed patients undergoing intermittent in-center hemodialysis.
INTRODUCTION
This list of complicationswould, of course, include acute elevations in intraocular pressure (1). No studies to date have examined intraocular pressure during high-flux hemodialysis. This study was designed to evaluate intraocular pressure changes in a group of chronic stable uremic patients who were receiving highflux hemodialysis, comparing pre- and intradialytic pressures.
Sitprija and Holmes in 1962 were the first group to report the occurrence of an increase in intraocular pressure in patients during hemodialysis (1). In subsequent studies in dogs, intraocular pressures were noted to increase during hemodialysis, with these increases well correlated to changes in extracellular osmolality (2). More recent studies in welldialyzed chronic renal failure patients, however, using “modern” approaches to dialytic therapy, have shown that significant elevations of intraocular pressure are infrequent during hemodialysis (3-5). With the development of efficient hemodialysis (i.e., “high-flux” hemodialysis), concerns have been raised about potential consequences of the rapid changes in extracellular osmolality which can occur with such treatments.
METHODS Sixteen patients with end stage renal disease were selected for the study. All of the patients were on chronic high-flux hemodialysisat Rocky MountainKidney Center, an outpatient chronic hemodialysis center affiliated with the University of Colorado. 109
Copyright 0 1990 by Marcel Dekker, Im.
Austin et al.
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
110
There were 8 men and 8 women >whoseages ranged from 20 to 67 (mean 39). Etiology of end stage renal disease included glomerulonephritis (8 patients), diabetes mellitus (4 patients), hypotension (2 patients), and reflux nephropathy (2 patients). No patients were known to have glaucoma. All patients were dialyzed using a Cobe Centry 111 machine and a Fresenius-60 dialyzer. Dialysate was bicarbonate with a sodium concentration of 140 mmol/L and no added glucose. Blood flows were 400 mL/min with an estimated urea clearance ( K ) of 250 mL/min. Dialyses were performed 3 daydweek. The: duration of each dialysis was 2.5 to 3.5 h depending on the patient's estimated urea space (V), aiming for a total time (2') yielding a KTIV greater than 1.2. Intraocular pressures (IOP) were obtained with a Schiatz tonometer using the 5.5-g plunger. Inmediately prior the measurement of intraocular pressure, 1 to 2 drops of proparocaine (0.5 %) was administered to' each eye for topical anesthesia. Measurements of IOP were performed predialysis and 2 h into dialysis with the patient in the supine position. Pressure readings were obtained from the calibration scale provided with the instrument. Calculations of serum osmolality (So,,J were performed based on the formula So,, = 2[Na+ (mmol/L) K+ (mmolL)] + Glucose (mig/dL)/18 BUN (mg/dL)/2.8. Data are expressed as the mean f standard deviation. Statistical analyses were performed on data employing either the paired or unpaired Student's t test where appropriate. P values greater than .05 are considered nonsignificant.
+
+
RESULTS Pre- and intradialyticintraocularpressure measurements were obtained in each of 16 patients. Values obtained were compared with the reported mean intraocular pressure per Schiotz tonometer of 16.1 f 2.5 nun Hg (7). Intraocular pressure before dialysis was 15.7 f 5.2 mm Hg in the right eye and 14.1 f 4.:! mm Hg in the left eye. The majority of the difference in the mean intraocular pressure between eyes is accounted for by a single patient (NB). If he is excluded, mean intraocular pressure was 15.0 f 4.5 mm Hg in the right eye and 14.6 f 4.0 mm Hg in the left eye.0nly two patients in the study had an intraocular pressure measurement > 21 mm Hg. In both of these patients, this reading occurred prior to dialysis. No patients had a significant increase in intraocular pressure during high-flux hemodialysis despite the marked change in calculated So, (7.7 f 2.2! mOsm/kg/h). Only two patients had intradialysis pressure readings 4 mm Hg
greater than the predialysis reading. Both of these patients were young (25 and 33 years old) with end stage renal disease due to glomerulonephritis. Two patients had greater than 4 mm Hg decreases in intraocular pressure during hemodialysis. Both of these patients were young (25, 30 years old) with end stage renal disease due to diabetes mellitus. Both had significant proliferation retinopathy which had previously required therapy. Comparing predialysis and intradialysis intraocular pressure readings (15.7 f 5.2 vs 15.0 f 4.0 mm Hg right eye and14.1 f 4.2vs13.9 f3.5mmHglefieye),nosignificant differences were noted. One patient who had tolerated standard hemodialysis without difficulty developed headaches on a regular basis during high-flux hemodialysis. Her intraocular pressure was normal predialysis and there was no significant change in intraocular pressure during dialysis. The etiology of her headaches was not determined.
DISCUSSION Sitprija and Holmes were the first group to publish the observation that elevations in intraocular pressure may occur during hemodialysis. In their patients the rise in intraocular pressure correlated best with decline in plasma osmolality during dialysis (1). Watson and Greenwood in 1966 showed an average increase in intraocular pressure of 8.1 mm Hg in 11 patients during chronic hemodialysis (8). They suggested on the basis of their studies in dogs that the increase in intraocular pressure was due to an increase in the relative concentration of urea in aqueous humor compared with plasma during dialysis with water diffusing into the aqueous from blood because of the difference in osmolality. Ramsell, Ellis, and Paterson in 1971 showed no significant change in mean intraocular pressure during 5- and 6-h dialysis, although half of the patients did have increases in intraocular pressure during dialysis (3). None of the patients, however, had clinically significant increases in intraocular pressure. They demonstrated that hourly changes in intraocular pressure did not correlate with changes in serum osmolality. Rever and his colleagues in 1981 showed in a small group of patients that hemodialysis with acetate or bicarbonate was not associated with changes in intraocular pressure (4).Gafter and his associates in 1985 showed no significant change in intraocular pressure in 27 of 30 chronic hemodialysis patients. Predialysis intraocular pressure was lower than intraocular pressure in normal patients (5).
IOP During High-Flux Hemdialysis
111
Table 1 Pre- and Intradialytic Intraocular Pressure in High-Flux Hemdialysis
IOP predialysis (mm Hg)
PT.
Sex
Age
Etiology of ESRD
SS
F F F F M M M F F M M F M
38 67 23 54 37 33 25 30 25 21 20 48
GN HTN
18.9 12.2 SW Reflux 14.6 HM GN 20.6 HM GN 10.2 MP GN 13.4 JN GN 12.2 DW DM 20.6 CC DM 17.3 RG Reflux 17.3 JN GN 22.4 PI GN 11.2 60 DM CG 14.6 NB M 49 26.6 DM 58 5.9 M CW HTN AW F 39 GN 13.4 Key. GN-glomerulonephritis, Reflux-reflux nephropathy, DM-diabetes
RJ
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
Right eye
osrnolality.
A recent study by B a d e and his colleagues addressed the safety of (“high-flux”) hypertonic hemodiafiltration (6). A group of chronic stable uremic patients were chosen for a randomized crossover trial with each patient receiving 4 months of standard hemodialysis and 4 months of hypertonic hemodiafiltration. There was no change in prevs postdialysis cerebral density or ventriclar size by CT scan, and there was no change in pre- versus postdialysis EEG in either type of dialysis. It has been suggested that intradialyticincreases in intraocular pressure are now rarely seen because of earlier, more frequent dialysis, with one important factor being a decreased rate of change of serum osmolality with each dialysis. Sitprija and Holmes showed in dogs that a change of serum osmolality (post- vs predialysis) of 11 mOsm/kg/hr was associated with a 42 % increase in intraocular pressure; a change of 8.5 mOsm/kg/hr was associated with minimal or no increase in intraocular pressure (1,2), Gafter showed a change in osmolality of 5 rnOsm/lcg/hr was not associatedwith a rise in intraocular pressure (5). In the current study we found no increase in mean intraocular pressure in chronic stable uremic
IOP intradialysis (mm Hg)
ASOsrn
Left eye
Right eye
Left eye
(mOsm/kg/hr)
14.6 12.2 17.3 17.3 10.2 10.2 13.4 20.6 18.9 14.6 20.6 12.2 13.4 7.1 7.1 15.9
17.3 10.2 15.9 18.9 12.2 17.3 17.3 15.9 13.4 15.9 20.6 12.2 12.2 20.6 5.3 14.6
15.9 12.2 14.6 14.6 10.2 14.6 17.3 17.3 13.4 14.6 20.6 13.4 11.2 5.9 10.2 15.9
7.4 5.3 9.6 10.1 14.0 6.3 7.4 8.7 7.0 8.9 6.9 7.4 6.0 6.8 6.2 5.9
mellitus, HTN-hypertension. ASosm = calculated change in serum
patients in high-flux hemodialysis, achieving a mean change in calculated osmolality of 7.7 mOsm/kg/hr. Previously it has been noted that intraocular pressure may be decreased in uremic patients on chronic hemodialysis. In Gafter’s study, mean intraocular pressure was 11.5 mm Hg in the right eye and 11.4 mm Hg in the left eye with reported normal controls of 16.3 ( f 3) mm Hg (5). Watson and Greenwood showed similar results (8). Mean intraocular pressure in uremic patients was 14.5 mm Hg, with mean intraocular pressure in controls of 17.8 mm Hg. In Rever’s study there was no significant difference between intraocular pressure in uremic patients and control patients (4). In the current study there is no significant difference between intraocular pressure in uremic patients (15.7 f 5.2 mm Hg in the right eye and 14.1 f 4.2 mm Hg in the left eye) and in reported controls (16.1 f 2.8 mm Hg). In summary, intraocular pressure measurements were obtained before and during dialysis in 16 chronic stable uremic patients on high-flux hemodialysis. There was no increase in intraocular pressure during dialysis. The risk of marked increases in intraocular pressure during
Austin et al.
112
high-flux hemodialysis appears to be low, although we cannot generalize this finding to include patients with glaucoma, as no patients with glaucoma were in the population from which we selected our patients.
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
ACKNOWLEDGMENTS
The authors would like to thank the staff and participating patients of the Rocky Mountain Kidney Center as well as Rita Taylor for her secretarial assistance.
Address correspondence to Joseph I. Shapiro, MD, Director, Chronic Dialysis, (2-281, University of ColoradoHealth Sciences Center, Denver, Colorado 80262.
REFERENCES 1. Sitprija V, Holms JH: Preliminary observationson the change in intracranial pressure and intraocular pressure during hemodialysis. Trans Am Soc Art$lntern Organs 8:300-308, 1962. 2. Sitprija V, Holmes JH, Ellis PD: Changes in intraocular pressure during hemodialysis. Invest Ophthal3:273-284, 1964. 3. Ramsell JT, Ellis PD, Paterson CA: Intraocular pressure changes during hemodialysis. Am J Ophthal72:926-930, 1971. 4. Rever B, Fox L. Bar-Khayim Y,Nissenson A Adverse ocular effects of acetate hemodialysis. Kidney Int 19157, 1981. 5 . Gafter U, Pinkas M, Hirsch 5, Levi J, Savir H Intraocularpressure in uremic patients on chronic hemodialysis. Nephron 40:74-75. 1985. 6. Bade C, Miller JDR, Ellis PD: The effects of dialysis on brain water and EEG in stable chronic uremia. Am J Kidney Dis 9~462-469, 1987. 7. Sugar HS: The glaucomas. In Sorsby A (ed): Modern Ophthalmology, 2nd ed. London, Butterworth, 1972. 8. Watson AG,Greenwood WR: Studies on the intraocular pressure during hemodialysis. Canad J Opthal 1:301-307, 1966.
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
Intraocular Pressures During High-Flux Hernodialysis J. N. Austin, M. Klein, J. Mishell, S. R. Contiguglia, J. Levy, L. Chan, and J. I . Shapiro Division of Renal Diseases, Department of Medicine University of Colorado School of Medicine, and The Rocky Mountain Kidney Center Denver, Colorado
ABSTRACT
The intraocularpressures of I6 patients with end stage renal failure treated with high-flux dialysis were measured before and during a high-Prn dialysis treatment. The patients were selected so as not to have glaucoma or history of glaucoma. Zntraocular pressures did not change signijkantly in any patients &ring or following a high-jlux hemodialysis treatment. These data suggest that high-flux hemodialysis does not result in increases in intraocular pressure nor does it precipitate acute glaucoma in well-dialyzed patients undergoing intermittent in-center hemodialysis.
INTRODUCTION
This list of complicationswould, of course, include acute elevations in intraocular pressure (1). No studies to date have examined intraocular pressure during high-flux hemodialysis. This study was designed to evaluate intraocular pressure changes in a group of chronic stable uremic patients who were receiving highflux hemodialysis, comparing pre- and intradialytic pressures.
Sitprija and Holmes in 1962 were the first group to report the occurrence of an increase in intraocular pressure in patients during hemodialysis (1). In subsequent studies in dogs, intraocular pressures were noted to increase during hemodialysis, with these increases well correlated to changes in extracellular osmolality (2). More recent studies in welldialyzed chronic renal failure patients, however, using “modern” approaches to dialytic therapy, have shown that significant elevations of intraocular pressure are infrequent during hemodialysis (3-5). With the development of efficient hemodialysis (i.e., “high-flux” hemodialysis), concerns have been raised about potential consequences of the rapid changes in extracellular osmolality which can occur with such treatments.
METHODS Sixteen patients with end stage renal disease were selected for the study. All of the patients were on chronic high-flux hemodialysisat Rocky MountainKidney Center, an outpatient chronic hemodialysis center affiliated with the University of Colorado. 109
Copyright 0 1990 by Marcel Dekker, Im.
Austin et al.
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
110
There were 8 men and 8 women >whoseages ranged from 20 to 67 (mean 39). Etiology of end stage renal disease included glomerulonephritis (8 patients), diabetes mellitus (4 patients), hypotension (2 patients), and reflux nephropathy (2 patients). No patients were known to have glaucoma. All patients were dialyzed using a Cobe Centry 111 machine and a Fresenius-60 dialyzer. Dialysate was bicarbonate with a sodium concentration of 140 mmol/L and no added glucose. Blood flows were 400 mL/min with an estimated urea clearance ( K ) of 250 mL/min. Dialyses were performed 3 daydweek. The: duration of each dialysis was 2.5 to 3.5 h depending on the patient's estimated urea space (V), aiming for a total time (2') yielding a KTIV greater than 1.2. Intraocular pressures (IOP) were obtained with a Schiatz tonometer using the 5.5-g plunger. Inmediately prior the measurement of intraocular pressure, 1 to 2 drops of proparocaine (0.5 %) was administered to' each eye for topical anesthesia. Measurements of IOP were performed predialysis and 2 h into dialysis with the patient in the supine position. Pressure readings were obtained from the calibration scale provided with the instrument. Calculations of serum osmolality (So,,J were performed based on the formula So,, = 2[Na+ (mmol/L) K+ (mmolL)] + Glucose (mig/dL)/18 BUN (mg/dL)/2.8. Data are expressed as the mean f standard deviation. Statistical analyses were performed on data employing either the paired or unpaired Student's t test where appropriate. P values greater than .05 are considered nonsignificant.
+
+
RESULTS Pre- and intradialyticintraocularpressure measurements were obtained in each of 16 patients. Values obtained were compared with the reported mean intraocular pressure per Schiotz tonometer of 16.1 f 2.5 nun Hg (7). Intraocular pressure before dialysis was 15.7 f 5.2 mm Hg in the right eye and 14.1 f 4.:! mm Hg in the left eye. The majority of the difference in the mean intraocular pressure between eyes is accounted for by a single patient (NB). If he is excluded, mean intraocular pressure was 15.0 f 4.5 mm Hg in the right eye and 14.6 f 4.0 mm Hg in the left eye.0nly two patients in the study had an intraocular pressure measurement > 21 mm Hg. In both of these patients, this reading occurred prior to dialysis. No patients had a significant increase in intraocular pressure during high-flux hemodialysis despite the marked change in calculated So, (7.7 f 2.2! mOsm/kg/h). Only two patients had intradialysis pressure readings 4 mm Hg
greater than the predialysis reading. Both of these patients were young (25 and 33 years old) with end stage renal disease due to glomerulonephritis. Two patients had greater than 4 mm Hg decreases in intraocular pressure during hemodialysis. Both of these patients were young (25, 30 years old) with end stage renal disease due to diabetes mellitus. Both had significant proliferation retinopathy which had previously required therapy. Comparing predialysis and intradialysis intraocular pressure readings (15.7 f 5.2 vs 15.0 f 4.0 mm Hg right eye and14.1 f 4.2vs13.9 f3.5mmHglefieye),nosignificant differences were noted. One patient who had tolerated standard hemodialysis without difficulty developed headaches on a regular basis during high-flux hemodialysis. Her intraocular pressure was normal predialysis and there was no significant change in intraocular pressure during dialysis. The etiology of her headaches was not determined.
DISCUSSION Sitprija and Holmes were the first group to publish the observation that elevations in intraocular pressure may occur during hemodialysis. In their patients the rise in intraocular pressure correlated best with decline in plasma osmolality during dialysis (1). Watson and Greenwood in 1966 showed an average increase in intraocular pressure of 8.1 mm Hg in 11 patients during chronic hemodialysis (8). They suggested on the basis of their studies in dogs that the increase in intraocular pressure was due to an increase in the relative concentration of urea in aqueous humor compared with plasma during dialysis with water diffusing into the aqueous from blood because of the difference in osmolality. Ramsell, Ellis, and Paterson in 1971 showed no significant change in mean intraocular pressure during 5- and 6-h dialysis, although half of the patients did have increases in intraocular pressure during dialysis (3). None of the patients, however, had clinically significant increases in intraocular pressure. They demonstrated that hourly changes in intraocular pressure did not correlate with changes in serum osmolality. Rever and his colleagues in 1981 showed in a small group of patients that hemodialysis with acetate or bicarbonate was not associated with changes in intraocular pressure (4).Gafter and his associates in 1985 showed no significant change in intraocular pressure in 27 of 30 chronic hemodialysis patients. Predialysis intraocular pressure was lower than intraocular pressure in normal patients (5).
IOP During High-Flux Hemdialysis
111
Table 1 Pre- and Intradialytic Intraocular Pressure in High-Flux Hemdialysis
IOP predialysis (mm Hg)
PT.
Sex
Age
Etiology of ESRD
SS
F F F F M M M F F M M F M
38 67 23 54 37 33 25 30 25 21 20 48
GN HTN
18.9 12.2 SW Reflux 14.6 HM GN 20.6 HM GN 10.2 MP GN 13.4 JN GN 12.2 DW DM 20.6 CC DM 17.3 RG Reflux 17.3 JN GN 22.4 PI GN 11.2 60 DM CG 14.6 NB M 49 26.6 DM 58 5.9 M CW HTN AW F 39 GN 13.4 Key. GN-glomerulonephritis, Reflux-reflux nephropathy, DM-diabetes
RJ
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
Right eye
osrnolality.
A recent study by B a d e and his colleagues addressed the safety of (“high-flux”) hypertonic hemodiafiltration (6). A group of chronic stable uremic patients were chosen for a randomized crossover trial with each patient receiving 4 months of standard hemodialysis and 4 months of hypertonic hemodiafiltration. There was no change in prevs postdialysis cerebral density or ventriclar size by CT scan, and there was no change in pre- versus postdialysis EEG in either type of dialysis. It has been suggested that intradialyticincreases in intraocular pressure are now rarely seen because of earlier, more frequent dialysis, with one important factor being a decreased rate of change of serum osmolality with each dialysis. Sitprija and Holmes showed in dogs that a change of serum osmolality (post- vs predialysis) of 11 mOsm/kg/hr was associated with a 42 % increase in intraocular pressure; a change of 8.5 mOsm/kg/hr was associated with minimal or no increase in intraocular pressure (1,2), Gafter showed a change in osmolality of 5 rnOsm/lcg/hr was not associatedwith a rise in intraocular pressure (5). In the current study we found no increase in mean intraocular pressure in chronic stable uremic
IOP intradialysis (mm Hg)
ASOsrn
Left eye
Right eye
Left eye
(mOsm/kg/hr)
14.6 12.2 17.3 17.3 10.2 10.2 13.4 20.6 18.9 14.6 20.6 12.2 13.4 7.1 7.1 15.9
17.3 10.2 15.9 18.9 12.2 17.3 17.3 15.9 13.4 15.9 20.6 12.2 12.2 20.6 5.3 14.6
15.9 12.2 14.6 14.6 10.2 14.6 17.3 17.3 13.4 14.6 20.6 13.4 11.2 5.9 10.2 15.9
7.4 5.3 9.6 10.1 14.0 6.3 7.4 8.7 7.0 8.9 6.9 7.4 6.0 6.8 6.2 5.9
mellitus, HTN-hypertension. ASosm = calculated change in serum
patients in high-flux hemodialysis, achieving a mean change in calculated osmolality of 7.7 mOsm/kg/hr. Previously it has been noted that intraocular pressure may be decreased in uremic patients on chronic hemodialysis. In Gafter’s study, mean intraocular pressure was 11.5 mm Hg in the right eye and 11.4 mm Hg in the left eye with reported normal controls of 16.3 ( f 3) mm Hg (5). Watson and Greenwood showed similar results (8). Mean intraocular pressure in uremic patients was 14.5 mm Hg, with mean intraocular pressure in controls of 17.8 mm Hg. In Rever’s study there was no significant difference between intraocular pressure in uremic patients and control patients (4). In the current study there is no significant difference between intraocular pressure in uremic patients (15.7 f 5.2 mm Hg in the right eye and 14.1 f 4.2 mm Hg in the left eye) and in reported controls (16.1 f 2.8 mm Hg). In summary, intraocular pressure measurements were obtained before and during dialysis in 16 chronic stable uremic patients on high-flux hemodialysis. There was no increase in intraocular pressure during dialysis. The risk of marked increases in intraocular pressure during
Austin et al.
112
high-flux hemodialysis appears to be low, although we cannot generalize this finding to include patients with glaucoma, as no patients with glaucoma were in the population from which we selected our patients.
Ren Fail Downloaded from informahealthcare.com by University of British Columbia on 10/29/14 For personal use only.
ACKNOWLEDGMENTS
The authors would like to thank the staff and participating patients of the Rocky Mountain Kidney Center as well as Rita Taylor for her secretarial assistance.
Address correspondence to Joseph I. Shapiro, MD, Director, Chronic Dialysis, (2-281, University of ColoradoHealth Sciences Center, Denver, Colorado 80262.
REFERENCES 1. Sitprija V, Holms JH: Preliminary observationson the change in intracranial pressure and intraocular pressure during hemodialysis. Trans Am Soc Art$lntern Organs 8:300-308, 1962. 2. Sitprija V, Holmes JH, Ellis PD: Changes in intraocular pressure during hemodialysis. Invest Ophthal3:273-284, 1964. 3. Ramsell JT, Ellis PD, Paterson CA: Intraocular pressure changes during hemodialysis. Am J Ophthal72:926-930, 1971. 4. Rever B, Fox L. Bar-Khayim Y,Nissenson A Adverse ocular effects of acetate hemodialysis. Kidney Int 19157, 1981. 5 . Gafter U, Pinkas M, Hirsch 5, Levi J, Savir H Intraocularpressure in uremic patients on chronic hemodialysis. Nephron 40:74-75. 1985. 6. Bade C, Miller JDR, Ellis PD: The effects of dialysis on brain water and EEG in stable chronic uremia. Am J Kidney Dis 9~462-469, 1987. 7. Sugar HS: The glaucomas. In Sorsby A (ed): Modern Ophthalmology, 2nd ed. London, Butterworth, 1972. 8. Watson AG,Greenwood WR: Studies on the intraocular pressure during hemodialysis. Canad J Opthal 1:301-307, 1966.
