Chronic Kidney Disease (CKD) is a growing global health problem, affecting nearly 10–15% of the world’s adult population, with an increasing incidence due to diabetes mellitus, hypertension, and aging (1). A significant proportion of these patients progress to end-stage renal disease (ESRD), requiring renal replacement therapies such as hemodialysis (HD) for survival. Haemodialysis is the most commonly used modality, which removes excess fluid, solutes, and metabolic waste through diffusion and ultrafiltration across a semipermeable membrane (2).

During haemodialysis, rapid osmotic and fluid shifts occur between the intravascular and extravascular compartments, leading to systemic hemodynamic changes that can also affect ocular physiology—particularly intraocular pressure (IOP) (3). The IOP is maintained by a delicate balance between aqueous humour formation and outflow. Changes in plasma osmolarity or blood pressure during HD can disturb this equilibrium, resulting in either transient increases or decreases in IOP. Globally, several studies have reported variable effects of hemodialysis on IOP. Some have observed a reduction in IOP following dialysis, attributed to decreased plasma osmolarity and improved aqueous outflow, while others reported a transient rise in IOP during ultrafiltration due to osmotic disequilibrium and changes in episcleral venous pressure (4,5). These fluctuations are clinically significant, especially in patients with glaucoma or ocular hypertension, as repeated IOP variation may accelerate optic nerve damage and visual field loss (6). In the Indian context, CKD is emerging as a major public health issue. Recent estimates suggest that one in every ten Indian adults suffers from some form of kidney dysfunction, and the number of patients requiring long-term dialysis is increasing rapidly (7). Despite this, there is limited literature from India evaluating the ocular effects of hemodialysis, particularly on IOP changes. Indian patients often present late in the course of renal disease, with comorbidities like diabetes and hypertension, which can independently affect ocular circulation and pressure regulation. Thus, studying IOP changes during hemodialysis in Indian patients can provide valuable insights into disease-specific and population-specific variations.

Understanding the pattern of IOP fluctuation during HD is crucial for early detection and management of ocular complications in this vulnerable population. The present study aims to evaluate intraocular pressure changes before and after hemodialysis and analyse their clinical significance in patients undergoing regular maintenance dialysis.

 Aim and Objectives

Aim

To evaluate the changes in intraocular pressure (IOP) before and after hemodialysis in patients with chronic kidney disease.

Objectives

1. To measure intraocular pressure in patients immediately before and after each hemodialysis session.
2. To assess the pattern and significance of intraocular pressure variation in relation to hemodialysis.
3. To analyse whether ultrafiltration volume and duration of dialysis influence intraocular pressure changes.

Study Design and Setting

This study was a prospective observational study conducted jointly by the Departments of Ophthalmology and Nephrology.

Study Population

A total of 100 patients with end-stage renal disease (ESRD) receiving regular hemodialysis were enrolled. All participants underwent dialysis 2–3 times per week, with each session lasting approximately 4 hours.

The mean duration of dialysis treatment prior to study entry was noted for each patient. Both eyes were examined, and an average of the two readings was used for analysis.

Inclusion Criteria

• Patients aged 18 years and above.
• Diagnosed cases of chronic kidney disease (CKD) on regular maintenance hemodialysis for at least 3 months.
• Willingness to participate and provide written informed consent.

Exclusion Criteria

• Known cases of primary or secondary glaucoma.
• History of ocular surgery, ocular trauma, or uveitis.
• Use of systemic or topical corticosteroids or drugs affecting IOP.
• Patients with active ocular infection or corneal abnormalities interfering with tonometry.
• Hemodynamically unstable or uncooperative patients.

Study Procedure

1. General and Ocular Evaluation

All patients underwent a detailed systemic and ophthalmic examination on the day of hemodialysis. Data on age, sex, cause of CKD, duration of dialysis, and associated systemic diseases such as diabetes or hypertension were recorded.

Ocular evaluation included:

• Best-corrected visual acuity (BCVA) using Snellen’s chart.
• Slit-lamp examination of the anterior segment.
• Intraocular pressure (IOP) measurement using a Goldmann Applanation Tonometer (GAT).

IOP was recorded for each patient twice during the same session:

• Pre-dialysis IOP: Measured within 30 minutes before initiation of HD.
• Post-dialysis IOP: Measured within 30 minutes after completion of HD.

Each IOP reading was taken three times, and the mean value was used for analysis.

2. Hemodialysis Parameters

Hemodialysis was performed using a standard Fresenius hemodialysis machine with bicarbonate dialysate. Parameters recorded from the dialysis unit included:

• Duration of dialysis (hours)
• Ultrafiltration volume (mL/kg)
• Blood flow rate (mL/min)
• Dialysate flow rate (mL/min)
• Body weight before and after dialysis
• Systolic and diastolic blood pressure before and after dialysis

These parameters were correlated with the degree of IOP change observed.

Data Collection and Grouping

For analysis, patients were grouped based on:

• Gender (male/female)
• Duration of hemodialysis (<1 year, 1–3 years, >3 years)
• Presence or absence of systemic comorbidities (diabetes mellitus, hypertension)

The difference in IOP (ΔIOP = post-dialysis IOP – pre-dialysis IOP) was calculated for each eye. A positive value indicated a rise, while a negative value indicated a fall in IOP following HD.

Statistical Analysis

Data were entered into Microsoft Excel and analyzed using IBM SPSS Statistics.

• Descriptive statistics (mean, standard deviation, frequency, and percentage) were used to summarize patient demographics, dialysis characteristics, and IOP readings.
• The paired t-test was used to compare mean pre- and post-dialysis IOP values.
• The Pearson correlation coefficient was used to assess the relationship between IOP change and dialysis parameters such as ultrafiltration volume and duration.
• Independent t-test and ANOVA were used to compare mean IOP changes among different subgroups (gender, duration, and comorbidities).
  A p-value ≤ 0.05 was considered statistically significant.

A total of 100 patients undergoing maintenance hemodialysis were included in the study. All patients completed the pre- and post-dialysis ocular examinations successfully.

The mean age of the study population was 52.4 ± 11.2 years (range 28–78 years), and 66% were males. The mean duration of hemodialysis was 2.4 ± 1.1 years.

Table 1. Demographic Distribution of the Study Population

Observation: Most patients were middle-aged males between 41–60 years.

Table 2. Systemic Comorbidities among Study Subjects

Observation: Hypertension was the most common comorbidity, followed by diabetes mellitus.

Table 3. Hemodialysis Parameters

Observation: The average ultrafiltration volume was approximately 2.1 liters per session with a significant reduction in blood pressure post-dialysis.

Table 4. Mean Intraocular Pressure (IOP) Before and After Hemodialysis

Observation: A statistically significant decrease in mean IOP was observed in both eyes after hemodialysis.

Table 5. Correlation between IOP Change and Ultrafiltration Volume

Interpretation: A mild positive correlation was found between IOP reduction and the amount of ultrafiltration — greater fluid removal was associated with greater IOP decrease.

Table 6. Mean IOP Change According to Duration of Dialysis

Observation: Patients on long-term hemodialysis (>3 years) showed a greater fall in IOP post-dialysis, which was statistically significant.

Summary of Findings

• Mean IOP before dialysis was 15.6 mmHg, which significantly decreased to 14.8 mmHg post-dialysis (p < 0.001).
• Greater ultrafiltration volume and longer dialysis duration were associated with a more pronounced reduction in IOP.
• The IOP reduction correlated mildly with weight loss and blood pressure decrease after dialysis.
• No patient experienced a clinically dangerous rise in IOP during or after dialysis.

The present study was conducted to evaluate the changes in intraocular pressure (IOP) before and after hemodialysis (HD) in patients with chronic kidney disease (CKD). A statistically significant reduction in mean IOP was observed following HD in both eyes (p < 0.001). The magnitude of IOP decrease correlated positively with ultrafiltration volume and duration of dialysis, indicating that systemic fluid and osmotic shifts during dialysis influence ocular pressure dynamics.

Physiological Basis of IOP Changes During Hemodialysis

IOP is primarily maintained by the balance between aqueous humor production and outflow. During HD, plasma osmolarity and oncotic pressure undergo marked alterations due to solute removal and ultrafiltration (8). A decrease in plasma osmolarity can create an osmotic gradient that facilitates water movement from the eye to the plasma, leading to a reduction in IOP (9). Conversely, rapid ultrafiltration or osmotic disequilibrium may transiently increase IOP if the aqueous humor cannot equilibrate quickly enough (10).

The present study supports the hypothesis that in most patients, the osmotic reduction during HD favors aqueous fluid egress from the eye, resulting in a net decrease in IOP post-dialysis. Similar findings have been reported in studies by Tokuyama et al. (1998) and Hu et al. (2018), where mean IOP dropped significantly after HD (11,12).

Comparison with Global Studies

In the current study, the mean pre-dialysis IOP was 15.6 mmHg, which decreased to 14.8 mmHg post-HD, consistent with previous international data. Jung et al. (2010) observed a reduction of approximately 1 mmHg after HD in both glaucomatous and non-glaucomatous eyes (13). Seymenoglu et al. (2015) reported a similar pattern, attributing it to the osmotic disequilibrium between plasma and aqueous humor following solute removal (14).

While most studies agree on a fall in IOP after HD, some have documented transient rises in certain patients, particularly those with compromised aqueous outflow or glaucoma. These transient spikes are thought to occur due to an osmotic imbalance where the aqueous humor lags behind plasma osmolarity changes, temporarily increasing fluid influx into the eye (9). However, in the present study, no such paradoxical rise was noted, possibly because glaucoma patients were excluded from the sample.

Indian Context

In India, where CKD prevalence is rapidly increasing due to diabetes and hypertension, regular HD is now a routine therapy for thousands of patients. However, ophthalmic monitoring is often neglected in this group. Few Indian studies have investigated the impact of HD on IOP. Rao et al. (2014) and Banerjee et al. (2019) observed a significant IOP reduction following dialysis, similar to the present study’s results, reinforcing the consistency of ocular responses in Indian patients (10).

The higher fall in IOP noted among patients undergoing long-term dialysis (>3 years) may reflect adaptation in ocular fluid regulation or changes in vascular permeability associated with chronic uraemia. The mild correlation between ultrafiltration volume and IOP change indicates that systemic dehydration and osmotic balance are major determinants of post-dialysis IOP variation.

Clinical Implications

The findings of this study have important clinical implications, particularly for patients with coexisting ocular conditions such as glaucoma or diabetic retinopathy. Significant fluid shifts during HD can alter ocular perfusion and optic nerve head physiology. Continuous monitoring of IOP in these patients is recommended, especially in those with high ultrafiltration volumes or large osmotic fluctuations.

Furthermore, knowledge of these IOP dynamics can help ophthalmologists and nephrologists coordinate care more effectively. Timing of ophthalmic evaluation, glaucoma monitoring, and use of IOP-lowering medications should ideally consider the dialysis schedule to avoid misinterpretation of readings influenced by transient dialysis-related changes.

This study demonstrated a significant reduction in intraocular pressure (IOP) following hemodialysis in patients with chronic kidney disease. The fall in IOP was correlated with the amount of ultrafiltration and duration of dialysis, indicating that fluid and osmotic changes during hemodialysis influence ocular pressure dynamics. These findings suggest that hemodialysis generally exerts a beneficial lowering effect on IOP. However, patients with glaucoma or compromised aqueous outflow should be closely monitored for possible fluctuations. Regular ophthalmic evaluation should be incorporated into the care of individuals on long-term hemodialysis to prevent potential ocular complications.

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