Dry eye symptoms, causes, tears, treatments

Basic anatomy of the eye

I become aware of dry eye issues and the importance of tears.  I copy a substantial part of the article “Facts About Dry Eye” from this web page https://nei.nih.gov/health/dryeye/dryeye.


Dry eye can be associated with:

. inflammation of the surface of the eye, the lacrimal gland, or the conjunctiva;
. any disease process that alters the components of the tears;
. an increase in the surface of the eye, as in thyroid disease when the eye protrudes forward;
. cosmetic surgery, if the eyelids are opened too widely.

What is the cornea?
The cornea is the clear, dome-shaped outer surface that covers the eye in front of the iris, the colored part of the eye. The cornea helps protect the rest of the eye from germs, dust, and other harmful matter. The cornea bends, or refracts, light entering the eye, and accounts for most of the eye’s total focusing power. It also serves as a filter to screen out most of the damaging ultraviolet (UV) wavelengths in sunlight.

[Cornea]  it has no blood vessels to nourish or protect it against infection. Instead, it receives its nourishment from the tears and the watery fluid (aqueous humor) that fills the chamber behind it.

. What are tears, and how do they relate to dry eye?
Tears, made by the lacrimal gland, are necessary for overall eye health and clear vision. Tears bathe the surface of the eye, keeping it moist, and wash away dust and debris. They also help protect the eye from bacterial and other types of infections.

Tears are composed of three major components: a) outer, oily, lipid layer produced by the meibomian glands; b) middle, watery, lacrimal layer produced by the lacrimal glands; and c) inner, mucous or mucin layer produced by goblet cells located within a thin transparent layer over the white part of the eye and covering the inner surface of the eyelids. Tears are made of proteins (including growth factors), electrolytes, and vitamins that are critical to maintain the health of the eye surface and to prevent infection.

Tears are constantly produced to bathe, nourish, and protect the eye surface. They are also produced in response to emergencies, such as a particle of dust in the eye, an infection or irritation of the eye, or an onset of strong emotions. When the lacrimal glands fail to produce sufficient tears, dry eye can result.

Any disease process that alters the components of tears can make them unhealthy and result in dry eye.

. What are the symptoms of dry eye?
Dry eye symptoms may include any of the following:

. stinging or burning of the eye;
. a sandy or gritty feeling as if something is in the eye;
. episodes of excess tears following very dry eye periods;
. a stringy discharge from the eye;
. pain and redness of the eye;
. episodes of blurred vision;
. heavy eyelids;
. inability to cry when emotionally stressed;
. uncomfortable contact lenses;
. decreased tolerance of reading, working on the computer, or any activity that requires sustained visual attention;
. eye fatigue.

. Causes and Risk Factors
What are the causes of dry eye?

Dry eye can be a temporary or chronic condition:

. Dry eye can be a side effect of some medications, including antihistamines, nasal decongestants, tranquilizers, certain blood pressure medicines, Parkinson’s medications, birth control pills and anti-depressants.
. Skin disease on or around the eyelids can result in dry eye.
. Diseases of the glands in the eyelids, such as meibomian gland dysfunction, can cause dry eye.
. Dry eye can occur in women who are pregnant.
. Women who are on hormone replacement therapy may experience dry eye symptoms. Women taking only estrogen are 70 percent more likely to experience dry eye, whereas those taking estrogen and progesterone have a 30 percent increased risk of developing dry eye.
. Dry eye can also develop after the refractive surgery known as LASIK. These symptoms generally last three to six months, but may last longer in some cases.
. Dry eye can result from chemical and thermal burns that scar the membrane lining the eyelids and covering the eye.
. Allergies can be associated with dry eye.
. Infrequent blinking, associated with staring at computer or video screens, may also lead to dry eye symptoms.
. Both excessive and insufficient dosages of vitamins can contribute to dry eye.
. Homeopathic remedies may have an adverse impact on a dry eye condition.
. Loss of sensation in the cornea from long-term contact lens wear can lead to dry eye.
. Dry eye can be associated with immune system disorders such as Sjögren’s syndrome, lupus, and rheumatoid arthritis. Sjögren’s leads to inflammation and dryness of the mouth, eyes, and other mucous membranes. It can also affect other organs, including the kidneys, lungs and blood vessels.
. Dry eye can be a symptom of chronic inflammation of the conjunctiva, the membrane lining the eyelid and covering the front part of the eye, or the lacrimal gland. Chronic conjunctivitis can be caused by certain eye diseases, infection, exposure to irritants such as chemical fumes and tobacco smoke, or drafts from air conditioning or heating.
. If the surface area of the eye is increased, as in thyroid disease when the eye protrudes forward or after cosmetic surgery if the eyelids are opened too widely, dry eye can result.
. Dry eye may occur from exposure keratitis, in which the eyelids do not close completely during sleep.

How is dry eye treated?
Depending on the causes of dry eye, your doctor may use various approaches to relieve the symptoms.

Dry eye can be managed as an ongoing condition. The first priority is to determine if a disease is the underlying cause of the dry eye (such as Sjögren’s syndrome or lacrimal and meibomian gland dysfunction). If it is, then the underlying disease needs to be treated.

. What can I do to help myself?
. Use artificial tears, gels, gel inserts, and ointments – available over the counter – as the first line of therapy. They offer temporary relief and provide an important replacement of naturally produced tears in patients with aqueous tear deficiency. Avoid artificial tears with preservatives if you need to apply them more than four times a day or preparations with chemicals that cause blood vessels to constrict.

. Wearing glasses or sunglasses that fit close to the face (wrap around shades) or that have side shields can help slow tear evaporation from the eye surfaces. Indoors, an air cleaner to filter dust and other particles helps prevent dry eyes. A humidifier also may help by adding moisture to the air.

. Avoid dry conditions and allow your eyes to rest when performing activities that require you to use your eyes for long periods of time. Instill lubricating eye drops while performing these tasks.



6 Ways To Fight Loneliness, I quote

And listen to “Patty Loveless – Lonely Too Long” on YouTube.com here, wouldn’t we?  https://www.youtube.com/watch?v=3E3ulC4swyE.

(Note: One needs to  click web browser’s “Open Link in New Tab” function” to play the the song directly from YouTube site and still keep this post open.)

Lonely Too Long – Patty Loveless – Awards performance – live vocal: https://www.youtube.com/watch?v=EkNApJs0DvU&list=RDEkNApJs0DvU#t=0

Also this: 50+ videos Play all Play now Mix – Patty Loveless – Lonely Too Longby YouTube


(Image source: http://www.bustle.com/articles/126162-loneliness-can-make-you-physically-sick-so-here-are-6-ways-to-fight-it)

I find this article “Loneliness Can Make You Physically Sick, So Here Are 6 Ways To Fight It” by Julie Sprvankless quite informative to me.  I thus quote her suggestions here.  The entire article is on this web page http://www.bustle.com/articles/126162-loneliness-can-make-you-physically-sick-so-here-are-6-ways-to-fight-it.


. Of course, it’s important to point out there is a distinction between being lonely and simply being alone. Loneliness isn’t merely the state of being alone. Rather, it is the perception of being alone. In other words, when you feel completely disconnected from everyone, even if you are surround[ed] by friends and family — or, you know, have 5,000 Facebook connections. Loneliness is a state of mind.

1. Take The Initiative

Sometimes, saying hello can be daunting. Especially for people who are lonely, reaching out of the sphere of isolation to make contact with another human being might seem pointless. But while withdrawing into yourself is tempting, the healthiest thing you can do when you are sad or feeling alone is to cultivate connections with other people.

2. Find A Commonality — Or Create One


Judging from a recent Reddit thread picking the brains of therapists, even our deepest feelings are likely shared by others. It makes sense, right? We’re all in this together, just trying not to lose our grip as this great big world keeps spinning faster. So the very act of reaching out may lead you to a connection or commonality that will make you feel less alone. Or, you could create a shared experience. Take a vested interest in what someone else is doing, and enjoy doing it with them.

3. Shift Your Focus To Someone Else

There’s a reason they say it is better to give than to receive — few things in life feel more rewarding than doing something good for someone else. If you find yourself dwelling on how alone you are and how hopeless you feel, turn your attention to the needs and feelings of someone else. Even small gestures such as smiling at people passing you on the street or wrapping someone in a bear hug can make you feel a sense of solidarity with others.

4. Find A Hobby

It’s easy to fall into the wormhole of despair when you have nothing else to do. It kind of falls under that whole “idle hands are the devil’s tools” idiom — a full agenda can keep you out of trouble in more ways than one. So take the leap if you’ve been toying with taking Zumba classes or learning another language. After all, studies show that people are happy when they are busy.

5. Don’t Bail

Trust me; I’ve done this a time or ten. When other people invite you to a party or beg you to join them for drinks after work, go. When your cousin insists you keep your standing Sunday brunch date, make an effort to show up. You might be surprised by how much you enjoy it, and you might make connections in the process who’ll understand what you’re going through.

6. Buy a Journal (And Write In It)

I may be partial, but I’m a firm believer that writing is a powerful tool of catharsis. When I was younger and lacked the faculties to eloquently express my feelings, I constantly scribbled my emotions into my diary. Today, writing still serves as an outlet for me. Give it a try! The great thing about chronicling your thoughts is that it helps you prioritize what’s important and pinpoint the different emotions you are feeling — including loneliness.

Dry eye can develop after various types of ophthalmic surgeries including cataract surgery.

I find this research paper “Incidence and Pattern of Dry Eye after Cataract Surgery” by Ngamjit Kasetsuwan, Vannarut Satitpitakul, Theerapa Changul, Supharat Jariyakosol informative.  I quote parts of the article below; the article is on this web page http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0078657.


What This Paper Adds

* The incidence of dry eye after phacoemulsification [including cataract surgery] was 9.8%.

* Dry eye symptoms can develop immediately after phacoemulsification and the severity can peak on day 7. Both symptoms and signs can improve over time. The dry eye pattern was similar between all three clinical tests (TBUT, Schirmer I without anesthesia, Oxford ocular surface staining system) and the OSDI questionnaire.

Longer quote:


Dry eye is a multifactorial disease of tears and ocular surface that can be result from aqueous deficiency or be evaporative in nature. This syndrome affects individuals worldwide. Long-term population-based studies have shown the incidence rates of dry eye among the population between ages 43 and 86 years at 5 and 10 years of follow-up to be 13.3% and 21.6% respectively. [4], [5] In Thailand, the incidence of dry eye in a hospital-based population was 34%. [10].

. Dry eye can develop often after various types of ophthalmic surgeries such as photorefractive keratectomy and laser-assisted in situ keratomileusis (LASIK). The incidence rates of dry eye, assessed by corneal fluorescein staining 1 week postoperatively for either nasal- or superior-hinge LASIK, were 47.06% and 52.94%, respectively. [6] In addition, after LASIK, dry eye can persist for up to 6 months or more with an incidence of 20%, [7] whereas in patients who have undergone blepharoplasty, dry eye can last up to 2 weeks or more with an incidence of 10.9%. [12] Even though many previous studies have compared the preoperative and postoperative changes in dry eye symptoms and/or the dry eye test values that worsened significantly after cataract surgery, [9], [11], [13] the current study was the first to report the incidence and pattern of dry eye after phacoemulsification using various combinations of tests over a 90-day period.

Like other studies, we also have reported that dry eye can develop after cataract surgery… Barabino et al. reported that phacoemulsification induced dry eye-like symptoms and signs on days 1 and 7 (unpublished data presented at the 6th International Conference on the Tear Film and Ocular Surface, Florence, Italy, September_2010).

. Regarding the pattern of postoperative dry eye, our findings were consistent with the results of Barabino et al. (unpublished data) who detected dry eye on the seventh day after surgery and rapid improvement within 30 days postoperatively. We did not found any late reaction of dryness such as filamentary keratopathy, superior limbic keratoconjunctivitis or persistent epithelial defect. However, one study reported that dry eye symptoms and a lower tear meniscus developed at 1 month and continued for another 2 months. [14] A possible explanation for this difference may be due to the different topical ocular drops and duration of regimens used: Tarivid Ophthalmic Solution (ofloxacin, Daiichi Sankyo, Tokyo, Japan) 4 times daily for 2 weeks, Pred Forte (prednisolone acetate ophthalmic suspension, USP 1%, Allergan, Irvine, CA) 4 times daily for 1 week, and Pranopulin Eye Drops (Senju Pharmaceutical, Chuo-Ku, Osaka, Japan) 4 times daily for 1 month. The surgical techniques may have affected their results, in which neither the size nor location of the wound was reported.

. Another explanation for the dry eye pattern observed in the current study was the recovery process of the corneal nerves. Since the cornea is one of the most highly innervated organs, with about 44 corneal nerve bundles entering the cornea around the limbus centripetally [18] and larger nerve fibers that run from the 9 o’clock to the 3 o’clock position and bifurcate to achieve a homogenous distribution over the entire cornea, [19] it is vulnerable to any damage within that region. Temporal corneal incisions created during phacoemulsification can reduce the corneal sensitivity in the surgical area and other areas far from the incision site… Disruption of the normal corneal innervation or lacrimal functional unit feedback can reduce the tear flow and blink rate and cause instability of the tear hyperosmolarity and tear film.

. In addition to transection of the corneal nerves and damage to the corneal epithelial cells, exposure to microscopic light, vigorous intraoperative irrigation of the tear film, elevation of inflammatory factors in the tear film due to ocular surface irritation, use of topical anesthesia intraoperatively, and topical eye drops administered postoperatively and its preservatives can cause dry eye after phacoemulsification.

Excessive instillation and incorrect use of preserved eye drops are important factors that contribute to the development of dry eye after phacoemulsification and corneal toxicity. However, the abnormal ocular surface staining in the current study showed typical interpalpebral staining pattern caused by dryness rather than inferior staining from drug toxicity or medicamentosa.


I  become interested in eyes, and also a believer of that “Life is a miracle.”, so I begin to read something about the pupil.  I quote some information from this web page https://en.wikipedia.org/wiki/Pupil.


(Top: A cat with vertical slit pupils, Right-top: A cuttlefish with W-shaped pupils, Right-2nd from top: A gecko with ‘string of pearls’ pupils, Bottom: A goat with horizontal rectangular pupils)


The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.
In humans the pupil is round, but other species, such as some cats, have vertical slit pupils, goats have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye’s aperture and the iris is the aperture stop. The image of the pupil as seen from outside the eye is the entrance pupil, which does not exactly correspond to the location and size of the physical pupil because it is magnified by the cornea. On the inner edge lies a prominent structure, the collarette, marking the junction of the embryonic pupillary membrane covering the embryonic pupil.


The iris is a contractile structure, consisting mainly of smooth muscle, surrounding the pupil. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae, and a radial group called the dilator pupillae. When the sphincter pupillae contract, the iris decreases or constricts the size of the pupil. The dilator pupillae, innervated by sympathetic nerves from the superior cervical ganglion, cause the pupil to dilate when they contract. These muscles are sometimes referred to as intrinsic eye muscles. The sensory pathway (rod or cone, bipolar, ganglion) is linked with its counterpart in the other eye by a partial crossover of each eye’s fibers. This causes the effect in one eye to carry over to the other. If the drug pilocarpine is administered, the pupils will constrict and accommodation is increased due to the parasympathetic action on the circular muscle fibers, conversely, atropine will cause paralysis of accommodation (cycloplegia) and dilation of the pupil.

Optic effects

When bright light is shone on the eye, light sensitive cells in the retina, including rod and cone photoreceptors and melanopsin ganglion cells, will send signals to the oculomotor nerve, specifically the parasympathetic part coming from the Edinger-Westphal nucleus, which terminates on the circular iris sphincter muscle. When this muscle contracts, it reduces the size of the pupil. This is the pupillary light reflex, which is an important test of brainstem function. Furthermore, the pupil will dilate if a person sees an object of interest.
The pupil gets wider in the dark but narrower in light. When narrow, the diameter is 2 to 4 millimeters. In the dark it will be the same at first, but will approach the maximum distance for a wide pupil 3 to 8 mm. In any human age group there is however considerable variation in maximal pupil size. For example, at the peak age of 15, the dark-adapted pupil can vary from 4 mm to 9 mm with different individuals. After 25 years of age the average pupil size decreases, though not at a steady rate.[3][4] At this stage the pupils do not remain completely still, therefore may lead to oscillation, which may intensify and become known as hippus. The constriction of the pupil and near vision are closely tied. In bright light, the pupils constrict to prevent aberrations of light rays and thus attain their expected acuity; in the dark this is not necessary, so it is chiefly concerned with admitting sufficient light into the eye.
A condition called bene dilitatism occurs when the optic nerves are partially damaged. This condition is typified by chronically widened pupils due to the decreased ability of the optic nerves to respond to light. In normal lighting, people afflicted with this condition normally have dilated pupils, and bright lighting can cause pain. At the other end of the spectrum, people with this condition have trouble seeing in darkness. It is necessary for these people to be especially careful when driving at night due to their inability to see objects in their full perspective. This condition is not otherwise dangerous.



Microsoft Windows 10 Pro OS mostly maintains itself

I read a question “Why does Windows require so much “hands-on” maintenance?” asked by a user on Cnet.com, and I have also read all 86 user comments, left as of November 14, 2015 10:51 a.m. Pacific Time. Though there are many informative comments offered on the internet, I am also careful about the merit of each comment with the thought that an emergency room medical doctor once expressed to me in a conversation at our gym; He said: Though the medical information on the internet is abundant, we don’t know where the information is really coming from. Going back to the question of “Why does Windows require so much “hands-on” maintenance?”, I actually feel that it is no longer a question for Windows 10 on most brand name computers (like Microsoft Surface Pro 3, Dell, HP that I have experience with). Microsoft Windows 10 takes care of its own maintenance from my experience of using Windows 10 from the Public beta version to the most current formal Windows 10 release.

My main computer is Apple MacBook Pro (early 2011 model) with operating systems from OS X 10.3 to current OS X 10.11. I have been installing my own computer operating systems on desktop and laptop computers since MS-DOS 5.0 as soon as the operating system is released. Microsoft Windows 10 has reached the intelligent level similar to Mac OS X that they could automatically troubleshoot issues and fix problems by themselves quickly with very little user’s interventions.

I quote a user’s comment with this subject line “I think one would find that Redmond has studied Linux….” by JCitizen dated November 13, 2015 7:33 PM PT for its being quite informative and similar to my thoughts.  However, the following quoted JCitizen’s itemized suggestions sound overwhelming to a non-computer enthusiast, and seem justifying the question of ” … require so much “hands-on” maintenance?”; I believe that his suggestion #1 shall be sufficient for most Windows 10 users – thus Windows 10 remains to be a low-maintenance operating system (OS).  The entire discussion could be found on this web page  http://www.cnet.com/forums/discussions/why-does-windows-require-so-much-hands-on-maintenance/.

Quote from “I think one would find that Redmond has studied Linux….” by JCitizen:

I think one would find that Redmond has studied Linux and studied it closely. Many of the lessons learned were incorporated with Windows code on the new operating systems. Even the NT drive geometry for magnetic spinning type drives has changed for the 64 bit Windows, and improved security even more. Cross platform applications are becoming more of a reality because of this, which has improved the reliability and usefulness of Windows as things progress.

Let’s face it, Guys like Joe Sixpack and I just want things to work. More people can do more things with a Windows computer than any other platform. Are there problems – yes – anytime you can run such an operating system with such a wide variety of applications and hardware it is going to have an underlying complexity that will raise its ugly head occasionally. Folks are discovering things like this with Android on smart phones, so there is some similarity in the two this way.

Unfortunately because of the popularity of the Windows platform and the ubiquitous use of Adobe Reader, Flash, and Java on the PC, there can be many vulnerabilities that make Windows a target. I have this basic advice for keeping Windows running relatively trouble free, but it will take some minor leg work.

1. At least turn on Windows Defender – I mean the one that has anti-virius as well as anti-malware.

2. Create a limited user account and stick to it for daily operation. Only go to the Administrative account when installing updates and applications.

3. Keep all applications up to date. 3rd Party Browsers are pretty good at doing this automatically now. and also their extensions.

4. Install File Hippo Application Manager to watch your applications for updates.

5. Install Secunia PSI as soon as it is listed to work on the new operating systems, if not already. Secunia will pop up and let you know you are behind on updates, even on the limited account. I haven’t seen how well this works on Win8.1 or Win10 yet., but it will prevent drive by take overs by malware looking for vulnerabilities.

6. Set up schedules for auto scanning by your AV and AM solutions, or at least do it manually, once a week from a 3rd party scanner (see CNET user reviews)

7. Use NoScript, AdBlock Plus, or ScriptSafe for 3rd Party Browsers to block infections from happening in the 1st place – a good free host file can help block malicious servers as well. See CNET user reviews for SpywareBlaster or equivalent.

8. Run the system file cleaner at least once a day or try something like CCleaner which can get rid of LSOs and Zombie files that can slow down your computer by robbing you of band width.

9. Normally I’d recommend a good free HIPs like Commodo Firewall, or Online Armor – but for beginners the messages the HIPs tells you may be confusing – generally as long as it doesn’t pop up while you are on the limited account, and you are not installing anything you will rarely see anything – if you do, it is time to question whether the web site you are on, or the game you are playing online is safe. Close all programs but CCleaner and run it to make sure no resident Trojans or other malware are left in the app-data files.

If you can do without Adobe or Java products installed on the PC, this will reduce your maintenance worries quite a bit – but at least you will get automatic reminders if you do all the above, or sign up for email update reminders from CNET on your favorite applications.

Windows has done its own defragging since Vista, and I’ve never noticed an improvement from 3rd Party defrag utilities, or doing it manually the Windows way. Be sure and leave at least 14% free space on your drive to do this efficiently. If you check “Computer” and see a red area on the drive, you know there are too many files on the system.If you don’t use a solid state drive, it wouldn’t hurt to run a check disc once a year, as bare minimum – although I never have had to at all myself, and still have very good run times. Though anytime you have to do a recovery from backup, or other major disaster, it is time to do this also .

If all you do is watch YouTube videos, surf the web, and email on a computer, perhaps it is time to look at Apple or Linux – but I’ve not seen either of them to be totally maintenance free. My brother is a Mac head and I see him working with that on his machines regularly.

Cataract surgery could cause a retinal hole or tearing

There are potential complications from a cataract surgery including:  [The cataract surgery could cause that] “… the vitreous movement can place traction on the retina and lead to a hole or tear which can be the start of a detachment”.  I quote the entire paragraph of the section titled “How does cataract surgery lead to a retinal detachment?” from this web page http://www.medicinenet.com/retinal_detachment/page5.htm.

Being in the group of people, who do the work, because of less competition there

I read a quote and feel the suggested practice will bring more peace to me.  I quote:

“My grandfather once told me that there are two kinds of people; Those who do the work and those who take the credit.  He told me to try to be in the first group; there was much less competition there.”

The practice shall fit me well too because I have reached the stage of avoiding competitions the best I can.

“What Are REM and Non-REM Sleep?” from WebMD.com

A typical hypnogram showing sleep stages and cycles in adult sleep (image by Luke Mastin). Source: http://www.howsleepworks.com/types_cycles.html
A typical hypnogram showing sleep stages and cycles in adult sleep (image by Luke Mastin). Source: http://www.howsleepworks.com/types_cycles.html
Duration of Sleep Stages. Source:  http://www.howsleepworks.com/types_cycles.html
Duration of Sleep Stages. Source: http://www.howsleepworks.com/types_cycles.html


I begin to learn about sleep cycle and sleep issues to improve my sleep quality.  I quote the article “What Are REM and Non-REM Sleep?” from WebMD.com.  The article is on this web page http://www.webmd.com/sleep-disorders/guide/sleep-101.  Some more information can also be found here: http://sleepapnea.org/learn/healthy-sleep.html.


When you get your ZZZs, you cycle between REM and non-REM sleep.

REM stands for rapid eye movement. During REM sleep, your eyes move quickly in different directions. That doesn’t happen during non-REM sleep.

First comes non-REM sleep, followed by a shorter period of REM sleep, and then the cycle starts over again. Dreams typically happen during REM sleep.

What Happens During Non-REM Sleep?

There are three phases of non-REM sleep. Each stage can last from 5 to 15 minutes. You go through all three phases before reaching REM sleep.

Stage 1: Your eyes are closed, but it’s easy to wake you up. This phase may last for 5 to 10 minutes.

Stage 2: You are in light sleep. Your heart rate slows and your body temperature drops. Your body is getting ready for deep sleep.

Stages 3: This is the deep sleep stage. It’s harder to rouse you during this stage, and if someone woke you up, you would feel disoriented for a few minutes.

During the deep stages of NREM sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.

As you get older, you sleep more lightly and get less deep sleep. Aging is also linked to shorter time spans of sleep, although studies show you still need as much sleep as when you were younger.

What Is REM Sleep?

Usually, REM sleep happens 90 minutes after you fall asleep. The first period of REM typically lasts 10 minutes. Each of your later REM stages gets longer, and the final one may last up to an hour. Your heart rate and breathing quickens.

You can have intense dreams during REM sleep, since your brain is more active.

Babies can spend up to 50% of their sleep in the REM stage, compared to only about 20% for adults.