Why Is IOP Higher in the Morning?

The morning is a time of awakening and rejuvenation for many individuals, but it can also bring about certain physiological changes within the body. One such change is the increase in intraocular pressure (IOP), which refers to the pressure inside the eye. Research has shown that IOP tends to be higher in the morning, and this phenomenon has intrigued scientists for many years. One proposed explanation for the higher IOP in the morning is the natural fluctuation of blood pressure during sleep hours. It’s well known that blood pressure tends to downregulate during the night, reaching it’s lowest point in the early morning hours. However, this decrease in blood pressure can have a reciprocal effect on IOP, causing it to rise. This simultaneous decline in blood pressure and increase in IOP can have potentially harmful effects on the eye. They can lead to a reduction in ocular perfusion pressure (OPP), which is the pressure needed to maintain blood flow within the eye. A decrease in OPP can compromise the delivery of vital nutrients and oxygen to the ocular nerve head, potentially causing damage over time. Additionally, stress has been found to play a role in the morning increase in IOP. Stress triggers various physiological responses in the body, including the release of hormones such as cortisol. Understanding why IOP is higher in the morning is of great importance in the field of ophthalmology. It can help clinicians develop better strategies for managing conditions such as glaucoma, a disease characterized by increased IOP that can lead to optic nerve damage and vision loss. By comprehending the complex interplay between sleep, blood pressure, stress, and IOP, researchers may uncover novel approaches to protecting the eye and preserving visual health.

Why Is IOP High at Night?

Recent studies have shed light on the intriguing phenomenon of elevated intraocular pressure (IOP) at night in healthy individuals. It’s been consistently observed that IOP tends to peak during the nocturnal hours and subsequently decrease during the daytime. The underlying reasons for this intriguing circadian variation in IOP have been a subject of scientific investigation.

One of the leading hypotheses to explain the elevated IOP at night is the decrease in aqueous production during sleep. It’s well-established that the production of aqueous humor, the liquid that fills the anterior chamber of the eye, decreases during the night. This reduction in aqueous production leads to a buildup of fluid within the eye, resulting in increased pressure.

Furthermore, it’s been proposed that choroidal congestion plays a role in the nighttime increase in IOP. The choroid, a vascular layer in the eye, experiences alterations in vascular flow distribution during sleep. In the supine position, there’s redistribution of blood flow towards the posterior pole of the eye, resulting in an accumulation of blood in the choroid.

However, individuals with certain ocular conditions, such as glaucoma, may experience more exaggerated fluctuations in IOP during the day and night. These variations may have more severe consequences for these individuals, as sustained elevated IOP can damage the optic nerve and lead to vision loss.

The normal diurnal variation of intraocular pressure (IOP) was studied, revealing that the maximum IOP was 16.8 +/- 2.0 mmHg, the minimum IOP was 12.8 +/- 1.7 mmHg, and the range of diurnal variation was 4.0 +/- 1.3 mmHg. The occurrence of maximum IOP was most frequent at noon (24.3%), followed by 9:00 am (21.4%) and 6:00 am (17.4%). These findings provide valuable insights into the fluctuation of IOP throughout the day.

What Is the Normal Diurnal Variation of IOP?

The normal diurnal variation of intraocular pressure (IOP) refers to the natural fluctuation in pressure within the eye over a 24-hour period. Numerous studies have been conducted to determine the typical pattern of IOP variation throughout the day.

Conversely, the minimum IOP is typically observed during the night, particularly in the early morning hours.

Maximum IOP levels occur most frequently at noon (24.3% of cases), followed by 9:00 am (21.4%) and 6:00 am (17.4%). These time points represent the periods when the majority of individuals experience peak intraocular pressure.

This information guides the diagnosis, management, and treatment of ocular conditions such as glaucoma, where IOP plays a crucial role in disease progression. By recognizing the typical fluctuations in intraocular pressure throughout the day, healthcare professionals can implement appropriate interventions to maintain optimal ocular health.

One potential explanation for high eye pressure in the morning is the natural regulation of blood pressure during sleep. This downregulation of blood pressure coincides with the time of day when intraocular pressure (IOP) is typically at it’s highest. This double impact on ocular perfusion pressure (OPP) during the night may potentially lead to increased damage to the optic nerve head.

Why Is My Eye Pressure High in the Morning?

There are several reasons why your eye pressure may be high in the morning. One possible explanation is the natural fluctuation of blood pressure during sleep. Blood pressure tends to downregulate during sleep hours in the early morning, which is also the time of day where intraocular pressure (IOP) tends to be the highest. This combination of factors can have a duplicative effect in reducing ocular perfusion pressure (OPP) during nocturnal hours.

When blood pressure decreases and IOP remains elevated, OPP, which represents the pressure gradient across the ocular vasculature, is compromised. This reduction in perfusion pressure can lead to inadequate blood flow to the optic nerve head, potentially causing damage over time.

The supine position during sleep can increase fluid accumulation in the eye, further elevating IOP. Additionally, certain individuals may have a higher susceptibility to morning IOP spikes due to age, genetics, or pre-existing eye conditions such as glaucoma.

It’s crucial to monitor and manage high morning eye pressure as it can lead to long-term damage to the optic nerve and vision loss. Regular eye examinations, including tonometry to measure IOP, are essential for early detection and appropriate management of elevated eye pressure.

During sleep, a number of studies have observed a noteworthy increase in intraocular pressure (IOP) among individuals without glaucoma. This phenomenon specifically occurs when these individuals assume recumbent sleeping positions.

Does IOP Increase While Sleeping?

A number of studies have shown that a normal, nonglaucoma patients IOP can significantly increase in recumbent sleeping positions. While asleep, the bodys position changes, leading to altered fluid dynamics within the eye. The nocturnal rise in IOP has been observed in both healthy individuals and those with glaucoma, indicating that sleep itself can influence intraocular pressure.

One particular study conducted on healthy subjects found that IOP can increase by as much as 6 to 7 mmHg when lying down compared to the IOP measurements taken while sitting or standing.

Various mechanisms have been proposed to explain this increase in IOP during sleep. One theory suggests that the recumbent sleeping position causes increased pressure on the eye due to the weight of the head. Additionally, the angle at which the eye is positioned in relation to the rest of the body while lying down may also play a role in facilitating increased fluid accumulation within the eye.

This shift in blood pressure and it’s impact on ocular structures is believed to be influenced by the autonomic nervous system, which regulates various bodily functions during sleep.

While some studies suggest it may contribute to the progression of glaucoma, others argue that it doesn’t have a long-term impact on optic nerve damage.


This suggests that there may be a correlation between the timing of elevated IOP and potential ocular nerve damage. However, further research is needed to fully understand the complexities of this phenomenon and it’s implications for ocular health.