Strabismus is when the eyes do not line up in the same direction. It often starts in infancy or childhood, but adults can develop it after injury, illness, or vision problems. People with strabismus may notice double vision, eye strain, headaches, or depth-perception trouble, and doctors see an eye turning in, out, up, or down. Treatment can include glasses, eye exercises, prism lenses, botulinum toxin, or surgery, and many people improve with care. Most people with strabismus have a normal life span, but early treatment helps protect vision and prevent amblyopia.
Overview
StrabismusSymptoms
Strabismus causes eyes that don’t line up, leading to double vision, eyestrain, headaches, or trouble focusing. You may notice one eye drifting inward, outward, up, or down, especially when tired. Children may squint, close one eye, or tilt their head.
Outlook and prognosis
Most people with strabismus do well, especially when it’s found and treated early. Vision therapy, glasses, prisms, or surgery can straighten the eyes, protect depth perception, and ease eye strain. Adults benefit too, though treatment goals may differ.
Causes and risk factors
Strabismus can be present at birth or develop later from muscle or nerve problems, uncorrected farsightedness, cataract, or eye/brain injury. Risk rises with family history, prematurity/low birth weight, neurological or genetic syndromes. Diabetes, thyroid eye disease, and stroke also contribute.
Genetic influences
Genetics play a meaningful role in strabismus, especially when it starts in childhood. Having a close relative with strabismus raises your risk, though many cases occur without family history. Multiple genes and small variations likely interact with vision development and muscle control.
Diagnosis
Diagnosis of strabismus starts with a comprehensive eye exam. The eye doctor checks alignment and movement, uses cover and light tests, and measures vision in each eye; children may need dilating drops. Imaging or neurologic tests are for unusual findings.
Treatment and drugs
Strabismus treatment focuses on straightening the eyes, improving depth perception, and preventing lazy eye. Options may include glasses, prism lenses, patching or eye drops to strengthen vision, vision therapy, and muscle surgery when needed. Care plans are tailored by age and cause.
Symptoms
Strabismus can affect how your eyes work together, and day to day it often shows up during reading, driving, or using screens. You might notice early symptoms of strabismus like double vision, eye strain, or a habit of closing one eye to clear things up. Symptoms vary from person to person and can change over time. In children, the signs may be subtle because they may not describe what they see.
One eye may turn in, out, up, or down, either constantly or off and on. Loved ones often notice the changes first. It may be more obvious when you are tired or unwell.
Seeing two images side by side or on top of each other can make reading or driving difficult. Clinicians call this diplopia, which means seeing a double image because the eyes aren’t aligned. It may ease if you close one eye.
Achy, tired eyes and brow headaches often follow long stretches of close work or screen use. These symptoms can come with strabismus when your eyes work extra hard to stay aligned. Short breaks and good lighting may help.
Judging distance can be harder, making steps, pouring drinks, or catching a ball less steady. With strabismus, the brain may rely more on one eye, reducing 3D vision. You might bump into door frames or misjudge where objects start and end.
How people usually first notice Strabismus?
Many families first notice strabismus when one eye doesn’t seem to line up with the other, especially in photos with flash where the reflection appears centered in one eye but off-center in the other. In babies, brief eye wandering can be normal in the first 2–3 months, but consistent turning in or out, a head tilt, or one eye seeming to “shut off” when tired are common first signs of strabismus. Pediatricians or vision screeners often confirm it during early check-ups when a child does not track objects evenly or fails a red-reflex or cover test, which is how strabismus is first noticed for many families.
Types of Strabismus
Strabismus has several well-recognized types, and each can look a little different in day-to-day life. You might see one eye drift inward, outward, up, or down, and it may be constant or show up only when tired or focusing on near work. Symptoms don’t always look the same for everyone. Understanding the main types of strabismus can help you describe what you notice and discuss types of strabismus with your eye specialist.
Esotropia (in-turning)
One or both eyes turn inward, sometimes more noticeable when looking at close objects. It can be constant or come and go, and may start in early childhood. Some children tilt their head to keep vision single.
Exotropia (out-turning)
One or both eyes drift outward, often showing up with distance viewing or when daydreaming or tired. People may notice intermittent double vision or eye strain. Bright light can trigger squinting or closing one eye outdoors.
Hypertropia (eye upward)
One eye sits higher than the other, making alignment look vertically off. This can cause double vision or a head tilt to line things up. Reading or going down stairs may feel awkward.
Hypotropia (eye downward)
One eye sits lower than the other, creating vertical misalignment. Some experience double vision or see images “stacked.” Tilting or turning the head can help reduce the mismatch.
Accommodative esotropia
The eyes turn inward when focusing hard to see clearly, usually in farsighted children. Glasses that correct focus often reduce or eliminate the crossing. Without correction, the in-turning tends to increase with near tasks.
Intermittent exotropia
The outward drift appears only at times, especially with fatigue, illness, or distance viewing. Between episodes, alignment may look straight. Not everyone will experience every type.
Paralytic strabismus
Eye misalignment results from a weakened or paralyzed eye muscle, often causing sudden double vision. Looking in the affected direction is hardest. Adults may need prisms or surgery once the pattern is stable.
Restrictive strabismus
Scar tissue or tight muscles limit eye movement, so the eye cannot move freely. People may notice pulling sensations or double vision in certain directions. Thyroid eye changes are a common cause.
A-pattern/B-pattern
Eye misalignment shifts depending on looking up or down, forming an A- or V-like pattern of alignment. Symptoms can worsen in specific gaze positions. Surgeons use this pattern to plan targeted muscle adjustments.
Sensory strabismus
Poor vision in one eye leads to drifting because the brain cannot keep both eyes aligned. The turning is often constant. Treating the underlying vision loss is key, along with alignment options.
Pseudoesotropia
Eyes appear crossed due to facial features like a broad nasal bridge, but alignment is actually normal. It’s common in infants and usually improves as facial features mature. An eye exam confirms true alignment.
What genetics can tell you about symptoms
Certain gene changes, like in PHOX2A, TUBB3, or KIF21A, can disrupt how eye muscles and their nerves develop, leading to misaligned eyes. These variants often shape the pattern—one eye turning inward or outward, limited eye movement, or double vision.
Causes and risk factors
Strabismus can happen when the eye muscles or the brain’s control of eye alignment do not work together. In children, risks include family history, premature birth or low birth weight, and strong farsightedness that is not corrected.
In adults, common causes of strabismus include stroke, head or eye injury, thyroid eye disease, nerve problems, or vision loss from cataract. Doctors distinguish between risk factors you can change and those you can’t. Correcting vision problems early, treating medical conditions, and protecting your eyes from injury may reduce risk, but some risks like genetics or birth history cannot be changed.
Environmental and biological risk factors
Strabismus can make one eye point in a different direction, which may affect depth perception and steady focus at school, work, or while driving. Knowing the risks can make it easier to spot early symptoms of strabismus and seek care early. Doctors often group risks into internal (biological) and external (environmental). Here are biological and environmental factors that can raise the chance of strabismus at different ages.
Being born too early or with low birth weight raises the chance of eye misalignment. Eye muscles and the visual system may be immature and develop unevenly. Complications linked to prematurity can add to the risk.
When the eyes must over-focus to see clearly, one eye may turn inward to help. Uncorrected farsightedness can trigger or worsen strabismus in children.
When one eye needs a much stronger lens than the other, the brain may favor the clearer eye. Over time the less-used eye can drift or turn.
A cloudy lens, droopy eyelid, or corneal scar can block clear sight in one eye. The brain receives an uneven picture, and the covered eye may begin to turn. The misalignment often becomes noticeable once the blockage is treated.
Genetic risk factors
Many cases of strabismus trace back, at least in part, to inherited influences that affect eye muscle control and visual development. Carrying a genetic change doesn’t guarantee the condition will appear. Researchers have identified both broad, polygenic patterns and rare chromosomal or single‑gene conditions among the genetic risk factors for strabismus. Understanding these patterns can help families discuss testing and early eye checks.
Family history: Strabismus often runs in families due to shared genes. If a parent or sibling has strabismus, your risk is higher than average.
Polygenic inheritance: Many small genetic changes can add up to shift eye alignment. This helps explain why severity and age at onset differ among relatives.
Inherited refractive traits: Genes linked to farsightedness or strong prescriptions can lead the eyes to cross inward when focusing in childhood. This is a common route for early symptoms of strabismus.
Chromosomal conditions: Extra or missing chromosome material, such as in Down syndrome or 22q11.2 deletion, can include eye misalignment as a feature. The type and degree of misalignment can vary.
Albinism genes: Genetic forms of albinism alter how visual signals route from the eye to the brain, increasing the chance of an eye turn. People may also have reduced depth perception or nystagmus.
Nerve wiring disorders: Rare inherited conditions that affect how eye-movement nerves connect can cause early, persistent strabismus. Duane spectrum and congenital fibrosis syndromes are examples.
Craniosynostosis syndromes: Changes in genes that shape the skull and eye sockets, such as Apert or Crouzon syndromes, can shift eye muscle paths and lead to eye misalignment. Alignment issues may continue even after skull surgery.
Lifestyle risk factors
Strabismus is typically congenital or neurologic in origin; lifestyle habits do not cause it. However, how lifestyle affects strabismus is through day-to-day choices that influence eye alignment control, symptoms like double vision, and risks such as amblyopia in children. Consistency with prescribed treatments and managing visual load can meaningfully change comfort and function. The points below focus on lifestyle risk factors for strabismus control and outcomes.
Wearing prescribed glasses consistently helps control accommodative esotropia and reduces eye crossing. Skipping or inconsistent wear often increases misalignment and eyestrain.
Following the prescribed patching schedule lowers amblyopia risk and supports better binocular function. Irregular patching reduces visual development gains and can compromise long-term alignment goals.
Prolonged, intense close-up work raises accommodative and convergence demand, which can worsen esotropia or trigger diplopia. Using regular breaks and the right working distance can improve alignment control during tasks.
Holding screens or books very close increases focusing effort and convergence, aggravating some types of strabismus. Keeping material at arm’s length (about 40 cm) reduces strain and symptoms.
Risk prevention
Strabismus can’t always be prevented, especially when it starts in infancy, but you can lower risks for some types and protect long-term vision. Prevention works best when combined with regular check-ups. Early detection and timely treatment often make alignment easier to correct and help avoid vision loss.
Routine eye checks in infancy, preschool, and school years help spot misalignment early. Early referral to an eye specialist can keep depth perception developing well.
Wearing the right glasses can reduce eyes crossing inward from uncorrected farsightedness. Updating prescriptions on schedule helps keep alignment as stable as possible.
If one eye is being ignored by the brain, early patching or drops can protect vision while alignment is addressed. This lowers the chance of lasting vision loss even if strabismus is present.
Sports goggles and eye-safe home habits reduce the chance of trauma that can damage eye muscles or nerves. Preventing eye injuries lowers the risk of acquired strabismus and double vision.
Transmission
Strabismus isn’t contagious—you can’t catch it from someone else. When people ask how strabismus is inherited, the short answer is that it often runs in families because of a mix of genes and early vision-development factors, rather than a single gene. Having a parent or sibling with strabismus raises a child’s chance, but many develop it with no family history. Sometimes strabismus occurs along with a genetic syndrome or after eye problems that blur one eye, and other times it arises on its own.
When to test your genes
Strabismus is usually diagnosed by exam, but consider genetic testing if it starts very early (infancy), runs in your family, is severe or unusual in one eye, or comes with developmental, neurologic, or other eye issues. Testing helps confirm cause, guide treatment, and refine recurrence risks. Ask your eye specialist or genetic counselor.
Diagnosis
Strabismus is usually diagnosed during a focused eye exam that looks at how the eyes line up and work together in daily life. You might notice small changes in daily routines, like one eye drifting in photos or squinting to focus, which often prompts an eye check. Doctors usually begin with a careful review of symptoms and simple alignment tests, then move to more detailed assessments as needed. If you’re wondering how strabismus is diagnosed, it typically involves a stepwise set of exams to confirm the pattern and rule out other causes.
Your provider asks when the eye turning started, how often it happens, and what makes it better or worse. They also review birth, developmental, and health history, including any previous eye issues or injuries.
Each eye is checked separately to see how clearly it sees at distance and near. Differences in clarity can suggest lazy eye (amblyopia), which often occurs with strabismus.
A light is shined toward the eyes to see if reflections land in the same spot. Uneven reflections suggest misalignment and guide which eye turns in, out, up, or down.
Covering and uncovering each eye shows whether one eye takes over and how the eyes realign when switching fixation. An alternate cover test helps reveal hidden (intermittent) misalignment.
Stages of Strabismus
Strabismus does not have defined progression stages. Instead, it can be intermittent or constant and may look better or worse with tiredness, illness, or where you focus, rather than following a step-by-step decline. Early symptoms of strabismus—like an eye that turns in photos, frequent squinting, or tilting the head—usually prompt an eye exam; Different tests may be suggested to help confirm the diagnosis and check for reduced vision in either eye. Doctors check how the eyes line up and move together using simple viewing and cover/uncover checks, light reflections on the eye surface, vision tests for each eye, and sometimes a dilated exam to look inside and plan treatment.
Outlook and prognosis
Looking at the long-term picture can be helpful. For many people with strabismus, early alignment with glasses, patching, vision therapy, or surgery improves how the eyes work together and reduces eye strain in school, work, and driving. Early care can make a real difference, especially for children, because the brain is still learning to fuse images into single vision. Adults with new or longstanding strabismus can also benefit; treatment often reduces double vision and improves comfort, even if perfect alignment isn’t always possible.
The outlook is not the same for everyone, but most children treated before age 7 to 8 avoid permanent loss of depth perception and the lazy-eye changes known as amblyopia. When treatment is delayed, the risk of amblyopia and reduced 3D vision rises, and some may need more than one surgery to maintain alignment over time. In medical terms, the long-term outlook is often shaped by both genetics and lifestyle—family history, farsightedness, and conditions like thyroid or nerve problems can influence how strabismus behaves and whether it returns. If strabismus appears suddenly in adulthood with double vision, early evaluation is important because it can signal another health issue that may need separate care.
Strabismus itself does not affect life expectancy; mortality is not increased by the eye misalignment. Quality of life, however, can be impacted by eye fatigue, headaches, reading difficulty, and self-consciousness, and addressing these can markedly improve day-to-day function. Over time, most people with strabismus maintain good vision in each eye and stable alignment with the right plan, though tune-ups—like updated glasses or occasional additional surgery—are sometimes needed. If you’re wondering about early symptoms of strabismus or chances of recurrence after surgery, talk with your doctor about what your personal outlook might look like.
Long-term effects
For many, long-term effects of strabismus show up in how the eyes team together for everyday tasks like reading, sports, and driving. Some notice changes early, while others only realize it over time when activities feel harder or more tiring. Long-term effects vary widely, and they depend on when the eye turn began and whether both eyes can work together. Here’s what doctors and research know about how the condition can play out over the years.
One eye may do less of the “seeing,” leading to reduced clarity that can persist into adulthood. This often develops in childhood when the brain favors the straighter eye.
Judging distances can stay tricky, making tasks like catching a ball or pouring liquids less precise. Some rely more on visual cues from size or motion to compensate.
Some adults with strabismus continue to see two images, especially when tired or focusing at a distance. The brain may suppress one image, but this can fluctuate and cause strain.
Long periods of close work can lead to aching eyes or headaches. For some, effortful focusing becomes a daily drain by late afternoon.
How is it to live with Strabismus?
Living with strabismus can feel like your eyes are trying to team up but sometimes point in different directions, which may lead to double vision, eye strain, headaches, or needing to tilt your head to keep things single. Daily life often involves extra effort for tasks that demand precise depth judgment—like pouring, catching a ball, parking a car, or stepping off a curb—and some may feel self‑conscious in social settings because others notice eye alignment. Many find that glasses, prism lenses, patching, vision therapy, or surgery improve comfort and function, and kids especially benefit when support at school and home is patient and consistent. For family and friends, a little understanding—slowing down during visually busy activities, making steady eye contact without staring, and encouraging regular care—can make a big difference.
Treatment and drugs
Strabismus treatment focuses on aligning the eyes, improving how they work together, and protecting vision, especially in children to prevent lazy eye. Options often include glasses or contact lenses to correct focusing problems, prism lenses to reduce double vision, and vision therapy (eye exercises) to train the eyes to coordinate; patching or blurring drops may be used to strengthen a weaker eye. If misalignment persists or is large, eye muscle surgery can reposition or adjust the muscles; some adults may also receive small doses of botulinum toxin to relax an overactive muscle. Not every treatment works the same way for every person, so plans are tailored by age, type of strabismus, and whether double vision or depth-perception issues are present. Ask your doctor about the best starting point for you, and expect regular follow-up to fine‑tune lenses, therapy, or timing of surgery.
Non-drug treatment
Non-drug care for strabismus focuses on improving eye alignment, easing double vision, and supporting comfortable, reliable sight for daily tasks. Non-drug treatments often lay the foundation for daily function while you and your eye team decide whether surgery is needed later. Your clinician may also watch for early symptoms of strabismus—like frequent eye rubbing, head tilting, or complaints of words “moving” on the page—and adjust care over time. Approaches can differ for children and adults, and they may change as your eyes develop or your needs shift.
Correcting focusing problems can reduce the effort your eyes use to stay aligned. In some types of strabismus, clearer focus helps the eyes straighten, especially at near.
Prisms bend light so each eye sees the same image, reducing or stopping double vision. They can be built into glasses or added as a thin stick‑on film and adjusted as your eyes change.
Covering the stronger eye encourages the weaker eye to work harder and can protect vision in children. Family members often play a role in supporting new routines so patching becomes easier.
Structured, supervised eye exercises train focusing, tracking, and teaming skills. Some non-drug options are delivered by specialists, such as an orthoptist, using lenses, prisms, and guided activities.
Your genes may have an impact on how drugs work for you
For strabismus, genes rarely change how eye-muscle surgeries work, but they can influence how you respond to medications like botulinum toxin. Genetic differences may affect nerve signaling and muscle sensitivity, shaping dose needs, effect duration, and side‑effect risk.
Pharmacological treatments
Medicines play a supporting role in strabismus. They can help in specific situations, but glasses, vision therapy, or surgery are often the mainstays. Not everyone responds to the same medication in the same way. Medicines rarely correct early symptoms of strabismus by themselves, yet they can reduce misalignment or help protect vision while other treatments do their work.
A tiny injection into an overactive eye muscle can relax it and reduce the eye turn. The effect is temporary but may align the eyes enough to improve control or delay surgery. Short-term side effects can include a droopy eyelid or double vision that usually fades.
Used to blur the stronger eye in amblyopia linked with strabismus, encouraging the weaker eye to work harder. This can be an alternative to patching in some children. Light sensitivity and near blur are the most common side effects.
Echothiophate iodide can reduce focusing effort and may lessen inward turning in select cases of accommodative esotropia. Due to side effects and limited availability, it is used rarely today. Careful monitoring by a pediatric eye specialist is important if prescribed.
If strabismus is driven by inflammation (for example, thyroid eye disease), steroids such as prednisone or methylprednisolone may help the underlying problem and improve alignment. These drugs are not used for routine strabismus but for specific causes under specialist care.
Genetic influences
Strabismus can run in families, but the genetics are complex. If you’re wondering whether strabismus is hereditary, the short answer is that it can be, but not always. Family history is one of the strongest clues to a genetic influence. Having a close relative with strabismus raises the chances for a child, yet many families see only one member affected, and the type or severity can differ between relatives. In most people, strabismus comes from a mix of small gene changes and non-genetic factors like differences in vision between the eyes, prematurity, or certain neurologic conditions; when early symptoms of strabismus appear alongside other developmental issues, doctors may look for a broader genetic syndrome. Genetic testing isn’t usually needed for isolated strabismus, but sharing your family history can help your doctor decide whether a genetics referral could be useful.
Is Strabismus genetic?
Genetics play a meaningful role in strabismus, especially when it starts in childhood. Having a close relative with strabismus raises your risk, though many cases occur without family history. Multiple genes and small variations likely interact with vision development and muscle control.
Pharmacogenetics—how genetics influence drug effects
Genetics can affect parts of strabismus care that involve medicines, especially anesthesia for surgery and how pain medicines work afterward. Alongside medical history and anesthesia planning, genetic testing can sometimes flag rare risks like malignant hyperthermia, a dangerous reaction to certain anesthesia drugs, so the team can choose safer options. Inherited low levels of the enzyme that clears the muscle relaxant succinylcholine (often called pseudocholinesterase deficiency) can cause prolonged paralysis after anesthesia and may be picked up by family history or specific pre‑op tests. Genes that influence how the body processes pain medicines also matter: people who break down codeine or tramadol very slowly or very quickly may have side effects or poor pain relief, and alternatives can be used. For botulinum toxin injections used in some strabismus cases and for common eye drops like atropine, reliable pharmacogenetic guidance is limited at this time. If there’s a personal or family history of anesthesia problems, talk with your surgical team about genetic testing before strabismus surgery so they can tailor medicines for safety and comfort.
Interactions with other conditions
People with strabismus often have other eye or health issues that influence how the eyes line up and how well treatments work day to day. Lazy eye (amblyopia) commonly occurs alongside strabismus, because a turned eye may be “ignored” by the brain; clouding of the lens (cataract) or a droopy eyelid can also reduce vision and make the misalignment more noticeable. Children born early, those with cerebral palsy, or those with genetic conditions such as Down syndrome have higher rates of strabismus, and it may be harder to control when development or muscle tone is affected. Thyroid eye disease, stroke, head injury, or nerve problems from diabetes can lead to new misalignment or sudden double vision; a condition may “exacerbate” (make worse) symptoms of another.
Uncorrected strong farsightedness can interact with strabismus by pushing the eyes to cross, and early symptoms of strabismus in children may show up when they’re reading or tired. Infections or general illnesses that cause fatigue can temporarily increase eye turning, then settle as health improves. Interactions can look very different from person to person, so care is often tailored and may include input from an eye specialist, a neurologist, or an endocrinologist when other diseases are involved. With careful care, many people live well despite having both strabismus and another condition.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described eyes that didn’t line up the same way. A child might tilt their head in family photos, or a parent might notice one eye drifting inward while reading. In many communities, elders offered home remedies or advice about patching, long before clinics were common. These early observations centered on how strabismus affected daily life—eye contact, schoolwork, depth perception—well before its causes were understood.
Ancient medical texts from Greece, India, and the Middle East mentioned eye turning and double vision. Early healers tried ointments, exercises, and, later, simple surgical cuts to tighten or loosen eye muscles. Results varied. Some people regained straighter alignment; others had only partial change. Not every early description was complete, yet together they built the foundation of today’s knowledge.
By the 18th and 19th centuries, surgeons began mapping the eye muscles and how they move the eyes together. They learned that eye alignment is like a team effort: muscles, nerves, and the brain must coordinate. The first standardized eye-muscle surgeries were described in the 1800s. Patching the stronger eye to help the weaker one develop vision also became common, especially for children with amblyopia (sometimes called “lazy eye”) linked to strabismus.
In the 20th century, better anesthesia and sterile techniques made surgery safer. Ophthalmologists created tests to measure eye turn in degrees, track double vision, and check depth perception. Adjustable sutures let surgeons fine-tune alignment during or shortly after surgery. At the same time, glasses with prism lenses and targeted vision therapy helped many people manage double vision without surgery.
In recent decades, knowledge has built on a long tradition of observation. Researchers showed that for many children with strabismus, early treatment supports the brain’s visual development, improving binocular vision and preventing long-term vision loss. Pediatric screening programs grew in both the US and Europe, so eye turns could be caught during routine visits. For adults, newer approaches—like botulinum toxin injections in select cases and refined surgical techniques—expanded options to improve alignment, comfort, and confidence at work and in social settings.
Today, the history of strabismus guides practical care. We know alignment can shift over time, so follow-up matters. We also know that causes differ—some are present from birth, others follow eye or nerve problems, and some arise after illness or injury. Looking back helps explain why modern care combines several tools—glasses, patching, prisms, exercises in specific cases, and surgery—chosen to match the person’s age, symptoms, and goals.