Eye Dictionary: S-T
S
sclera. This is the white part of the eye. The sclera is the firm wall of the eye that gives the eye its shape and structure. Made of collagen fiber, the sclera is relatively tough. It is also continuous with the clear cornea in the front of the eye. The sclera is covered by a thin layer of skin called the conjunctiva. This clear skin covers the eyeball and contains small blood vessels you can see in the mirror. When you are looking at the "white" of your eye, you are looking through this conjunctival skin at the scleral wall of the eye itself.
scleral buckle. This is asurgical procedure used to repair a retinal detachment. With this procedure, a silicone band is inserted around the eye and cinched tight, like abelt around a waistline. This decreases traction forces inside the eye which allows the retina to lay back in its normal position. Scleral buckle surgery is widely performed and used to be the only viable treatment for retinal detachments. Other techniques have arisen such as vitrectomy and pneumatic retinopexy. Every retina specialist has their own surgical preferences and the technique chosen depends upon circumstances and the location of retinal breaks. Some retina surgeons seem to be leaning toward vitrectomy as improvements in retina instrumentation have made vitrectomies fast and less traumatic. There are benefits and risks in all these retinal procedures. One potential problem with a scleral buckle is that the silicone band tends to make the eye physically longer and this can change the overall refractive error of the eye. It's fairly common for the eye to become extremely nearsighted. This can be fixed with a change in glasses prescription, but if the difference between the eyes becomes too great, the glasses won't be comfortable to wear and a contact lens might be required instead. Fortunately, most of these balance issues can be fixed during cataract surgery or with LASIK if they become too bothersome. Less easy to fix is the potential for strabismus, where the buckle makes the eyes slightly out of alignment, causing double vision. Retinal detachments are serious, so these risks are acceptable given the alternative (a blind eye).
second sight. This is the phenomenon where cataract formation seems to make the vision "better" by improving your glasses prescription. A cataract is when the lens inside your eye becomes cloudy. An enlarging cataract usually causes glare problems, but the cataract growth can also change the eye's overall "glasses prescription" as well. For some people, this change is in a bad direction and they require stronger and stronger glasses to see well. For a lucky few, the change is in a "good" direction and actually decreases the reliance on spectacles. The eyes aren't really "improving," it just seems that way. One of the signs that perhaps a cataract is getting worse is when the glasses prescription starts changing rapidly.
shingles. This is a re-outbreak of chicken pox. When people get chickenpox as a child, the viral infection can hit large parts of the body. The body's immune system fights back and eradicates the virus. However, the virus is not completely gone, but usually sits dormant in the base of the nerves in the spine and head. Later in life, as the immune system slows down, the virus can reactivate and run back out the nerve and affect the skin. This outbreak is called "shingles" or "zoster" and it usually affects a single dermatome (strip of skin) in the body. If the fifth cranial nerve of the head (called the trigeminal nerve) is affected, the shingles outbreak can occur on the face. Often the forehead and scalp are involved with painful lesions and swelling of the skin. If the eye is affected this can lead to corneal scaring and long-term vision problems. We usually treat a shingles outbreak with an antiviral medication like Valtrex or acyclovir. If these medications are started within three days of initial symptoms, the medications have been found to limit duration of illness and decrease the chance of long-term sensation/pain problems. It's important to see an eye doctor if there is any eye redness or change in vision as the eye may require treatment as well.
Simbrinza. This is a new combination glaucoma drop combining two separate pressure-lowering medicines - brinzolamide (Azopt) and brimonidine (Alphagan). Combination drugs are useful for decreasing the number of actual drops you must take. The downside, however, is their premium cost is not covered by your prescription drug plan.
Similasan. This is a brand of herbal eye drop therapies. Given the shear number of FDA-approved and scientifically studied eye medicines available, I never bother with this. Someone must be using this, however, since the company is still in business and the product is still on shelves.
sixth nerve palsy. This is a paralysis of the sixth cranial nerve. This nerve controls a single eye muscle, the abducens muscle, which is responsible for making the eye look to the side. If this muscle stops working the eye turns inward (crosseyed) and has a hard time moving outwards. Most people complain of a sideby-side horizontal double vision. Like all cranial nerve palsies, there are many potential causes for an abducens palsy. The most common cause is microvascular injury from diabetes or hypertension. You can think of this like a miniature "stroke" to the nerve. Other potential causes are mass lesions (tumors or aneurysms) and high intracranial pressure such as from pseudotumor cerebri. Most sixth nerve palsies are self-limited and improve after a few months. Ophthalmologists used to watch these palsies for spontaneous improvement, but in this day and age of MRI imaging, we tend to image everyone with a new palsy to rule out the dangerous stuff.
slit lamp microscope. This is a microscope used by an eye doctor to look at the eye. The eye microscope is unique when compared to a traditional microscopes. For one thing, the microscope has been turned on its side so that people can be examined without having to lie down flat. Also, the light-source used can be narrowed to a very narrow beam of light. This light can be angled into the eye to form an illuminated cross-section of the eye ... just like how a CAT scan takes cross-section x-ray slices. The eye is the only place in the body that blood vessels and nerves can be seen without opaque skin blocking the view. With a dilated eye exam, the optic nerve (a direct extension off the brain) can be viewed in great detail. Certain systemic conditions can be observed and diagnosed using the slit lamp microscope. For example, diabetes can cause micro-bleeding in the retina (diabetic retinopathy) and inflammatory conditions like rheumatoid arthritis can cause internal ocular inflammation (uveitis). With the slitlamp microscope and careful technique, individual white blood cells floating in the eye can be detected.
SLT. This is the abbreviation for Selective Laser Trabeculoplasty - it is a glaucoma laser procedure designed to lower eye pressure in a nondestructive way. Most cases of glaucoma involve microscopic blockage of the trabecular meshwork drain inside the eye. If the internal ocular fluid doesn't drain properly, aqueous fluid pressure builds up and causes gradual damage over time. There are many ways to lower eye pressure. Glaucoma eye drops work to open the drain chemically and you can think of them like "Drano" for the eye. Glaucoma surgery is very effective, but it is also a big production and associated with some morbidity. Fortunately, glaucoma laser therapies have come a long way. ALT was the original laser procedure. With ALT, a "hot" laser was directed at the eye's drain and used to create scars in the trabecular meshwork. These scars helped open drainage tissue to manually get things flowing. This worked really well to lower pressure, but unfortunately the effect is short-lived and tended to wear off after a couple of years. ALT can't be repeated as there is only so much scar tissue the eye can suffer. SLT is a newer laser technology that some people have dubbed as a "cold laser." SLT doesn't create scaring inside the eye, but instead is used to irritate and stimulate the trabecular drainage cells to flow better. The benefit to SLT is that no permanent scars are created and the procedure can be repeated if it wears off. The downside to SLT is that is doesn't work for everyone. We like to think of SLT as an adjunctive therapy to eye drops ... if you are taking a single glaucoma drop, SLT therapy may be able to get you off it. If you are already on glaucoma drops and your eye pressure is creeping up, an SLT treatment may keep you from needing an additional drop or surgery. The procedure takes about 5 minutes and is painless with little recovery time.
Snellen chart. This is the eye chart used by American eye doctors for measuring vision. The letters on this eye chart are calibrated based on distance measurements, comparing your vision to someone with "perfect" eyes. For example, if you have a vision of 20/60 ... this means that the letters you can barely see when standing 20 feet from the chart can be easily seen by a "perfect-eyed person" standing a full 60 feet away from the same chart! In the USA and many European countries, legal driving vision is 20/50 and you are considered legally blind if your corrected vision is 20/200 or worse. The Snellen chart is calibrated to be 20 feet from the exam chair you are sitting in ... but few eye doctors have exam rooms this long. To offset this, mirrors are used to obtain the full 20-foot distance.
Soothe. This is a brand name rewetting drops from Bausch & Lomb. Competing brands are Systane, Blink, GenTeal, and Refresh.
squinting. Squinting of the eyes is common, and is commonly done in an attempt to see better. If the eye has refractive error (like nearsightedness or farsightedness) the images entering the eye do not focus well on the retina and look blurry. By squinting and looking through the eyelashes, you can actually see a little clearer. The eyelashes turn the eye into a pinhole camera, which improves depth of focus and improves vision. Squinting is not a good long-term vision solution (obviously), so glasses or contacts are prescribed to improve vision and decrease eye strain. See the entry on pinholes to understand this concept better.
steroid. Steroids are useful in ophthalmology for treating ocular inflammation. This is particularly useful after cataract surgery and with internal ocular inflammation such as uveitis. Steroids can also be useful for decreasing corneal scarring, such as after a trauma or infection. Care must be used with steroids, however, as they can exacerbate infections - viruses and bacteria love steroids as it "makes them strong." While short term topical steroids are relatively safe, long-term use may cause some problems. Some people are "steroid responders" and their eye pressure ends to go up while on topical eye drops. This pressure change usually takes a few weeks to kick in and goes away after a couple of weeks off the drops. Steroids are also associated with premature cataract formation, though this is more of an issue with oral steroids. Common steroids used by eye doctors are prednisolone acetate (Pred-Forte or Econopred), loteprednol (Lotemax and Alrex) and dexamethasone (usually found in combination drops like Tobradex).
strabismus. This is a descriptive term used by eye doctors to describe eyes that are in poor alignment with each other. For example, someone with strabismus may be cross-eyed, wall-eyed, or have an eye that drifts upwards. Some people have strabismus that occurs only when tired and others have a problems with double vision only with reading. There are many causes for strabismus, from congenital motor problems to cranial nerve palsies. Strabismus needs to be evaluated by an eye doctor for an appropriate workup. If the alignment problem persists, strabismus surgery is sometimes recommended. Prism glasses are another option, especially for long-standing strabismus in adults.
strabismus surgery. This is surgery to correct ocular misalignment (strabismus). Most strabismus surgery is performed on toddlers to correct alignment problems such as crossed-eyes. This surgery involves the weakening or strengthening of eye muscles by shortening them or changing their insertion points on the edge of the eye. While most ophthalmologists have trained in performing strabismus surgery, these days the procedure is mostly carried out by pediatric ophthalmologists who have more practice with this type of surgery. Many pediatric ophthalmologists perform adult strabismus surgery as well.
stye. A stye is an infection of one of the oil or sweat glands running along the eyelid. Styes are tender to the touch and may form an abscess or pus layer that is visible through the skin as a "white head." The treatment for a stye typically begins with warm compresses and gentle massage. While a "pimple" elsewhere on the body can usually be "popped" or "lanced" with little ill effect, I strongly discourage being too aggressive with the eyelid as the eyeball underneath is a sensitive structure and easily injured. Also, some doctors think that aggressive eyelid squeezing may actually spread infection to adjacent skin and make the stye worse. If warm compresses and gentle massage aren't working, the stye may require topical or oral antibiotics, and even lancing. A stye is a bit different than a chalazion, which is a blockage of the deeper meibomian glands that tends to be painless.
subconjunctival hemorrhage. This is an extremely red eye that occurs when a blood vessel on the surface of the eye ruptures. The white part of the eye (the sclera) is covered by a very thin layer of skin called the conjunctiva. You can see this skin when looking in a mirror, as red blood vessels course through it and look like "lines" on the eye. If one of these blood vessels bursts for some reason, such as after a cough or sneeze, blood will track underneath the conjunctiva and make the eye look extremely red. It only takes a few drops of blood to make the eye look bright red and this can look quite alarming in the mirror. A subconjunctival hemorrhage is almost always harmless, but warrants a check to make sure there is no bleeding inside the eye (a hyphema or vitreous hemorrhage) and to make sure the cornea isn't drying out.
sulfa allergy. Several medicines are sulfa based and can cause problems for people allergic to sulfa drugs. The main culprits are the carbonic anhydrase inhibitors used for glaucoma. Examples of these glaucoma drops include dorzolamide, Trusopt, Azopt, and Cosopt. Also, the water pill Diamox (acetazolamide) is sometimes used for treating advanced glaucoma, but is sulfa-based as well. Sulfacetamide is an antibiotic eye drop (also called Bleph-10) that can also cause sulfa problems, but I rarely prescribe this, given the plethora of good antibiotic alternatives.
sulfacetamide sodium 10%. Also known by the trade name Bleph-10, this is an antibiotic eye drop that has gone generic and can be found on the Walmart $4 list. This drug is sulfa-based and not good for those people with sulfa allergy.
Systane. This is a brand name rewetting drop made by Alcon. Competing brands include Soothe, Blink, GenTeal, and Refresh.
scleral buckle. This is asurgical procedure used to repair a retinal detachment. With this procedure, a silicone band is inserted around the eye and cinched tight, like abelt around a waistline. This decreases traction forces inside the eye which allows the retina to lay back in its normal position. Scleral buckle surgery is widely performed and used to be the only viable treatment for retinal detachments. Other techniques have arisen such as vitrectomy and pneumatic retinopexy. Every retina specialist has their own surgical preferences and the technique chosen depends upon circumstances and the location of retinal breaks. Some retina surgeons seem to be leaning toward vitrectomy as improvements in retina instrumentation have made vitrectomies fast and less traumatic. There are benefits and risks in all these retinal procedures. One potential problem with a scleral buckle is that the silicone band tends to make the eye physically longer and this can change the overall refractive error of the eye. It's fairly common for the eye to become extremely nearsighted. This can be fixed with a change in glasses prescription, but if the difference between the eyes becomes too great, the glasses won't be comfortable to wear and a contact lens might be required instead. Fortunately, most of these balance issues can be fixed during cataract surgery or with LASIK if they become too bothersome. Less easy to fix is the potential for strabismus, where the buckle makes the eyes slightly out of alignment, causing double vision. Retinal detachments are serious, so these risks are acceptable given the alternative (a blind eye).
second sight. This is the phenomenon where cataract formation seems to make the vision "better" by improving your glasses prescription. A cataract is when the lens inside your eye becomes cloudy. An enlarging cataract usually causes glare problems, but the cataract growth can also change the eye's overall "glasses prescription" as well. For some people, this change is in a bad direction and they require stronger and stronger glasses to see well. For a lucky few, the change is in a "good" direction and actually decreases the reliance on spectacles. The eyes aren't really "improving," it just seems that way. One of the signs that perhaps a cataract is getting worse is when the glasses prescription starts changing rapidly.
shingles. This is a re-outbreak of chicken pox. When people get chickenpox as a child, the viral infection can hit large parts of the body. The body's immune system fights back and eradicates the virus. However, the virus is not completely gone, but usually sits dormant in the base of the nerves in the spine and head. Later in life, as the immune system slows down, the virus can reactivate and run back out the nerve and affect the skin. This outbreak is called "shingles" or "zoster" and it usually affects a single dermatome (strip of skin) in the body. If the fifth cranial nerve of the head (called the trigeminal nerve) is affected, the shingles outbreak can occur on the face. Often the forehead and scalp are involved with painful lesions and swelling of the skin. If the eye is affected this can lead to corneal scaring and long-term vision problems. We usually treat a shingles outbreak with an antiviral medication like Valtrex or acyclovir. If these medications are started within three days of initial symptoms, the medications have been found to limit duration of illness and decrease the chance of long-term sensation/pain problems. It's important to see an eye doctor if there is any eye redness or change in vision as the eye may require treatment as well.
Simbrinza. This is a new combination glaucoma drop combining two separate pressure-lowering medicines - brinzolamide (Azopt) and brimonidine (Alphagan). Combination drugs are useful for decreasing the number of actual drops you must take. The downside, however, is their premium cost is not covered by your prescription drug plan.
Similasan. This is a brand of herbal eye drop therapies. Given the shear number of FDA-approved and scientifically studied eye medicines available, I never bother with this. Someone must be using this, however, since the company is still in business and the product is still on shelves.
sixth nerve palsy. This is a paralysis of the sixth cranial nerve. This nerve controls a single eye muscle, the abducens muscle, which is responsible for making the eye look to the side. If this muscle stops working the eye turns inward (crosseyed) and has a hard time moving outwards. Most people complain of a sideby-side horizontal double vision. Like all cranial nerve palsies, there are many potential causes for an abducens palsy. The most common cause is microvascular injury from diabetes or hypertension. You can think of this like a miniature "stroke" to the nerve. Other potential causes are mass lesions (tumors or aneurysms) and high intracranial pressure such as from pseudotumor cerebri. Most sixth nerve palsies are self-limited and improve after a few months. Ophthalmologists used to watch these palsies for spontaneous improvement, but in this day and age of MRI imaging, we tend to image everyone with a new palsy to rule out the dangerous stuff.
slit lamp microscope. This is a microscope used by an eye doctor to look at the eye. The eye microscope is unique when compared to a traditional microscopes. For one thing, the microscope has been turned on its side so that people can be examined without having to lie down flat. Also, the light-source used can be narrowed to a very narrow beam of light. This light can be angled into the eye to form an illuminated cross-section of the eye ... just like how a CAT scan takes cross-section x-ray slices. The eye is the only place in the body that blood vessels and nerves can be seen without opaque skin blocking the view. With a dilated eye exam, the optic nerve (a direct extension off the brain) can be viewed in great detail. Certain systemic conditions can be observed and diagnosed using the slit lamp microscope. For example, diabetes can cause micro-bleeding in the retina (diabetic retinopathy) and inflammatory conditions like rheumatoid arthritis can cause internal ocular inflammation (uveitis). With the slitlamp microscope and careful technique, individual white blood cells floating in the eye can be detected.
SLT. This is the abbreviation for Selective Laser Trabeculoplasty - it is a glaucoma laser procedure designed to lower eye pressure in a nondestructive way. Most cases of glaucoma involve microscopic blockage of the trabecular meshwork drain inside the eye. If the internal ocular fluid doesn't drain properly, aqueous fluid pressure builds up and causes gradual damage over time. There are many ways to lower eye pressure. Glaucoma eye drops work to open the drain chemically and you can think of them like "Drano" for the eye. Glaucoma surgery is very effective, but it is also a big production and associated with some morbidity. Fortunately, glaucoma laser therapies have come a long way. ALT was the original laser procedure. With ALT, a "hot" laser was directed at the eye's drain and used to create scars in the trabecular meshwork. These scars helped open drainage tissue to manually get things flowing. This worked really well to lower pressure, but unfortunately the effect is short-lived and tended to wear off after a couple of years. ALT can't be repeated as there is only so much scar tissue the eye can suffer. SLT is a newer laser technology that some people have dubbed as a "cold laser." SLT doesn't create scaring inside the eye, but instead is used to irritate and stimulate the trabecular drainage cells to flow better. The benefit to SLT is that no permanent scars are created and the procedure can be repeated if it wears off. The downside to SLT is that is doesn't work for everyone. We like to think of SLT as an adjunctive therapy to eye drops ... if you are taking a single glaucoma drop, SLT therapy may be able to get you off it. If you are already on glaucoma drops and your eye pressure is creeping up, an SLT treatment may keep you from needing an additional drop or surgery. The procedure takes about 5 minutes and is painless with little recovery time.
Snellen chart. This is the eye chart used by American eye doctors for measuring vision. The letters on this eye chart are calibrated based on distance measurements, comparing your vision to someone with "perfect" eyes. For example, if you have a vision of 20/60 ... this means that the letters you can barely see when standing 20 feet from the chart can be easily seen by a "perfect-eyed person" standing a full 60 feet away from the same chart! In the USA and many European countries, legal driving vision is 20/50 and you are considered legally blind if your corrected vision is 20/200 or worse. The Snellen chart is calibrated to be 20 feet from the exam chair you are sitting in ... but few eye doctors have exam rooms this long. To offset this, mirrors are used to obtain the full 20-foot distance.
Soothe. This is a brand name rewetting drops from Bausch & Lomb. Competing brands are Systane, Blink, GenTeal, and Refresh.
squinting. Squinting of the eyes is common, and is commonly done in an attempt to see better. If the eye has refractive error (like nearsightedness or farsightedness) the images entering the eye do not focus well on the retina and look blurry. By squinting and looking through the eyelashes, you can actually see a little clearer. The eyelashes turn the eye into a pinhole camera, which improves depth of focus and improves vision. Squinting is not a good long-term vision solution (obviously), so glasses or contacts are prescribed to improve vision and decrease eye strain. See the entry on pinholes to understand this concept better.
steroid. Steroids are useful in ophthalmology for treating ocular inflammation. This is particularly useful after cataract surgery and with internal ocular inflammation such as uveitis. Steroids can also be useful for decreasing corneal scarring, such as after a trauma or infection. Care must be used with steroids, however, as they can exacerbate infections - viruses and bacteria love steroids as it "makes them strong." While short term topical steroids are relatively safe, long-term use may cause some problems. Some people are "steroid responders" and their eye pressure ends to go up while on topical eye drops. This pressure change usually takes a few weeks to kick in and goes away after a couple of weeks off the drops. Steroids are also associated with premature cataract formation, though this is more of an issue with oral steroids. Common steroids used by eye doctors are prednisolone acetate (Pred-Forte or Econopred), loteprednol (Lotemax and Alrex) and dexamethasone (usually found in combination drops like Tobradex).
strabismus. This is a descriptive term used by eye doctors to describe eyes that are in poor alignment with each other. For example, someone with strabismus may be cross-eyed, wall-eyed, or have an eye that drifts upwards. Some people have strabismus that occurs only when tired and others have a problems with double vision only with reading. There are many causes for strabismus, from congenital motor problems to cranial nerve palsies. Strabismus needs to be evaluated by an eye doctor for an appropriate workup. If the alignment problem persists, strabismus surgery is sometimes recommended. Prism glasses are another option, especially for long-standing strabismus in adults.
strabismus surgery. This is surgery to correct ocular misalignment (strabismus). Most strabismus surgery is performed on toddlers to correct alignment problems such as crossed-eyes. This surgery involves the weakening or strengthening of eye muscles by shortening them or changing their insertion points on the edge of the eye. While most ophthalmologists have trained in performing strabismus surgery, these days the procedure is mostly carried out by pediatric ophthalmologists who have more practice with this type of surgery. Many pediatric ophthalmologists perform adult strabismus surgery as well.
stye. A stye is an infection of one of the oil or sweat glands running along the eyelid. Styes are tender to the touch and may form an abscess or pus layer that is visible through the skin as a "white head." The treatment for a stye typically begins with warm compresses and gentle massage. While a "pimple" elsewhere on the body can usually be "popped" or "lanced" with little ill effect, I strongly discourage being too aggressive with the eyelid as the eyeball underneath is a sensitive structure and easily injured. Also, some doctors think that aggressive eyelid squeezing may actually spread infection to adjacent skin and make the stye worse. If warm compresses and gentle massage aren't working, the stye may require topical or oral antibiotics, and even lancing. A stye is a bit different than a chalazion, which is a blockage of the deeper meibomian glands that tends to be painless.
subconjunctival hemorrhage. This is an extremely red eye that occurs when a blood vessel on the surface of the eye ruptures. The white part of the eye (the sclera) is covered by a very thin layer of skin called the conjunctiva. You can see this skin when looking in a mirror, as red blood vessels course through it and look like "lines" on the eye. If one of these blood vessels bursts for some reason, such as after a cough or sneeze, blood will track underneath the conjunctiva and make the eye look extremely red. It only takes a few drops of blood to make the eye look bright red and this can look quite alarming in the mirror. A subconjunctival hemorrhage is almost always harmless, but warrants a check to make sure there is no bleeding inside the eye (a hyphema or vitreous hemorrhage) and to make sure the cornea isn't drying out.
sulfa allergy. Several medicines are sulfa based and can cause problems for people allergic to sulfa drugs. The main culprits are the carbonic anhydrase inhibitors used for glaucoma. Examples of these glaucoma drops include dorzolamide, Trusopt, Azopt, and Cosopt. Also, the water pill Diamox (acetazolamide) is sometimes used for treating advanced glaucoma, but is sulfa-based as well. Sulfacetamide is an antibiotic eye drop (also called Bleph-10) that can also cause sulfa problems, but I rarely prescribe this, given the plethora of good antibiotic alternatives.
sulfacetamide sodium 10%. Also known by the trade name Bleph-10, this is an antibiotic eye drop that has gone generic and can be found on the Walmart $4 list. This drug is sulfa-based and not good for those people with sulfa allergy.
Systane. This is a brand name rewetting drop made by Alcon. Competing brands include Soothe, Blink, GenTeal, and Refresh.