Eye Dictionary: N
N
naphazoline. This is a vasoconstrictor found in many over-the counter eye drops such as Naphcon-A and Opcon-A. By constricting the blood vessels on the conjunctiva surface, this makes the eyes look whiter. Unfortunately, many people develop a rebound redness and their eyes actually look more red and swollen when the drop wears off. We see a similar response with Visine ... which is why most eye doctors don't recommend using vasoconstrictors.
Naphcon-A. This is an over-the-counter allergy drop, useful for itching and swelling of the eyelids. This drop actually contains two separate drugs. The first is called pheniramine - this is an antihistamine to decrease inflammation. While effective, it is not as powerful as stronger antihistamines found in newer drops. The other drug is called naphazoline. This is a vasoconstrictor that makes the eyes less red, but can cause a rebound redness when the drop wears off (an effect similar to Visine). Overall, Naphcon-A and the other generic equivalents are effective but I never prescribe them as they are not as powerful as newer allergy drops like Alaway/Zaditor or the prescription drops Bepreve and Pataday.
narrow angles. This is when the "angle" inside the eye is naturally tight, putting you at risk for having an acute glaucoma attack. The front part of the eye is filled with a fluid called the aqueous humor. This fluid is continuously produced and drained from the eye, with the balance of fluid input and output controlling the overall pressure of the eye. The drain inside the eye is called the trabecular meshwork and it is located where the white of the eye (the sclera) meets the colored iris. The anatomy of this intersection forms an angle. Some people's ocular anatomy is such that their angle is very narrow. If the angle narrows too much, it can shut down entirely. With no aqueous drainage, the pressure inside the eye shoots up suddenly, causing an acute glaucoma with extreme pain and vision loss. Narrow angles can be evaluated using gonioscopy. If the angles are narrow enough, a prophylactic LPI procedure can be considered to avoid angle closure.
nasolacrimal duct obstruction. This is a blockage of the tear drainage pathway that connects the eye to the nose. Tears are produced in the eyelids and cover the eye like a waterfall. Because of gravity, tears eventually form a small "lake" running along the edge of the lower eyelid. This lake drains through little holes in the eyelid called puncta, through some "underground tubing" in the skin and eventually into the nose. This drainage pathway is called the nasolacrimal system, and is the reason when we have runny eyes, we tend to have a runny nose as well. If this pathway becomes blocked, the tears have nowhere to drain, instead welling up in the eye and even running down the cheek. In adults, nasolacrimal duct (NLD) obstruction can be temporary if from allergic soft tissue swelling or permanent if caused by scarring from a prior infection. Many children are born with a temporary NLD obstruction at birth that eventually resolves during the first year (but may also require probing to manually force open). In adults, NLD obstruction often requires a surgical procedure called a dacryocystorhinostomy (DCR for short). This surgery involves making a small incision on the skin and creating a new drainage pathway for the tears to enter the nose. This type of procedure is usually performed by an oculoplastic surgeon, though occasionally ENT doctors will perform the same procedure.
Natamycin. Also known as pimaricin, this is the only commercially prepared eye drop available for fungal eye infection. While effective, it can sometimes be hard to obtain and can be expensive. The main alternative we use is amphotericin B ... but this drug isn't easy to obtain either as it has to be especially prepared by a compounding pharmacy.
nearsightedness. This is a refractive error where the eyes see well at near distance, but have a hard time seeing far away. Normally, the eye works like a camera with light entering the eye being focused perfectly on the retina. The retina is analogous to the film in a camera and located at the back of the eye. When a person is nearsighted, however, light wants to focus in front of the retina and visual images look blurry. By weakening the eye's overall focusing power with glasses (using negative diopter power lenses) light can focus properly on the retina. Extremely nearsighted eyes tend to be longer or larger than average, which puts them at slightly increased risk for retinal detachment. The prevalence of nearsightedness seems to be increasing in our society ... the reason for this is not entirely clear, but it may have something to do with the increase in near activities (i.e., iPads and Game Boys).
Neomycin/Polymyxin/Dexamethasone - An inexpensive combination drop containing two antibiotics to treat infection combined with a mild steroid for inflammation. This drug is available as an eye drop or an ointment. While most tolerate this medicine, some people have a sensitivity to the neomycin component. For these people, Tobradex or Zylet may be a better option. The trade name for this medicine is Maxitrol, which is still used to describe this medicine as it is easier to pronounce. This drug is on the $4 generic list at Walmart.
Neosporin. This is a combination antibiotic ointment containing neomycin, bacitracin, and polymyxin. While relatively effective as a broad pectrum antibiotic, some people have an allergy or sensitivity to neomycin. In these cases, Polysporin (which only contains bacitracin and polymyxin) can be used to good effect. I rarely prescribe this medicine given the plethora of good antibiotic drops and ointments available that have less side effects.
neovascularization. This is when abnormal blood vessels grow inside the eye. The eye is a very metabolically active organ. It continuously works and detects light, even while sleeping. In some ways the eye works like the heart ... in the sense that it is "always on." As such, the eye, especially the retina, requires a rich blood supply to function properly. The retina doesn't have a collateral blood supply. It only gets its blood and oxygen nourishment from a couple of sources. If there is a disruption to this blood supply, the retina quickly becomes starved for oxygen and can die. Many things can disrupt the blood flow to the eye. Diabetic retinopathy, blood clots, and macular degeneration can interfere with the blood supply to the retina. In all of these cases, the retina becomes "hungry" for oxygen and responds by pumping out "vascular endothelial growth factors" or VEGFs. These are natural hormonal stimulants for the growth of new blood vessels inside the eye. Normally, this would be great as new blood vessels could bring in fresh blood and keep the retina well-nourished, but it doesn't work this way. The new blood vessels grow quickly and are abnormal, with a tendency to leak, bleed, and contract causing vitreous hemorrhages, macular edema, and even retinal detachments. It is the VEGFs that cause neovascularization. To combat neovascularization, eye doctors try to decrease VEGF production. PRP laser can be performed to destroy these tissues. For more localized neovascularization at the macula, anti-VEGF injection medicines like Avastin are now being used extensively in the eye and this has drastically improved the treatment for "wet" macular degeneration.
neovascular glaucoma. With neovascularization, abnormal blood vessels grow inside the eye, causing significant retinal damage. These blood vessels can also grow into the front of the eye, covering the surface of the iris, and into the trabecular meshwork drain. If this drain becomes blocked with abnormal vessels, aqueous fluid can't exit back into the blood stream. This causes extremely high pressure inside, leading to acute glaucoma. Neovascular glaucoma is very difficult to treat as the pressure is recalcitrant to normal glaucoma drops. In these cases, a tube-shunt procedure is often required to create a new drainage pathway out of the eye. There are several causes for neovascular glaucoma but the most common is after a central retinal vein occlusion.
nepafenac. Known by the trade name Nevanac, this is an anti-inflammatory NSAID eye drop that is commonly used after cataract surgery to cool the eye down and decrease the chance of macular edema.
Neptazane. Also called methazolamide, this is a water pill used in the treatment of glaucoma. It is a carbonic anhydrase inhibitor that works by decreasing the production of aqueous fluid inside the eye. This medicine has the same mechanism of action as Diamox (acetazolamide).
Nevanac. Also known as nepafenac, this is an NSAID anti-inflammatory eye drop. It is commonly used after cataract surgery to cool the eye down and decrease the risk of post-operative macular edema.
NSAID. This stands for Non-Steroidal Anti-Inflammatory Drug. NSAIDs are very common. In fact, most over the counter pain relievers such as aspirin, Motrin (ibuprofen), and Tylenol are NSAIDs. In the eye, NSAID eye drops are used for pain control, but are most often used after cataract surgery to decrease the possibility of macular edema. Common NSAID eye drops include Acular, Nevanac, diclofenac, and Bromday.
numbing drops. These are eye drops used to anesthetize the surface of the eye. They are commonly used during an eye exam to help check the eye pressure (see applanation tonometry) and to numb the eye prior to eye surgery. See anesthetic drops for more information on this topic.
nystagmus. This is an involuntary, rhythmic "to and fro" movement of the eyes. Most nystagmus are in the horizontal axis, such that the eyes are constantly moving to the left and right. There are many causes for this abnormal eye movement, though most nystagmus occur secondary to congenital motor deficits that begin in childhood. Sensory nystagmus can occur in a child who is born with poor vision and is associated with many other congenital visual defects such as albinism. Nystagmus that develop later in life are rare and can be caused by vestibular (inner ear) abnormalities, drug toxicities (including alcohol), or more serious neurologic problems like a tumor or stroke. Police officers sometimes look for nystagmus with their field sobriety tests, looking for horizontal nystagmus while asking people to look to their right and left.
Naphcon-A. This is an over-the-counter allergy drop, useful for itching and swelling of the eyelids. This drop actually contains two separate drugs. The first is called pheniramine - this is an antihistamine to decrease inflammation. While effective, it is not as powerful as stronger antihistamines found in newer drops. The other drug is called naphazoline. This is a vasoconstrictor that makes the eyes less red, but can cause a rebound redness when the drop wears off (an effect similar to Visine). Overall, Naphcon-A and the other generic equivalents are effective but I never prescribe them as they are not as powerful as newer allergy drops like Alaway/Zaditor or the prescription drops Bepreve and Pataday.
narrow angles. This is when the "angle" inside the eye is naturally tight, putting you at risk for having an acute glaucoma attack. The front part of the eye is filled with a fluid called the aqueous humor. This fluid is continuously produced and drained from the eye, with the balance of fluid input and output controlling the overall pressure of the eye. The drain inside the eye is called the trabecular meshwork and it is located where the white of the eye (the sclera) meets the colored iris. The anatomy of this intersection forms an angle. Some people's ocular anatomy is such that their angle is very narrow. If the angle narrows too much, it can shut down entirely. With no aqueous drainage, the pressure inside the eye shoots up suddenly, causing an acute glaucoma with extreme pain and vision loss. Narrow angles can be evaluated using gonioscopy. If the angles are narrow enough, a prophylactic LPI procedure can be considered to avoid angle closure.
nasolacrimal duct obstruction. This is a blockage of the tear drainage pathway that connects the eye to the nose. Tears are produced in the eyelids and cover the eye like a waterfall. Because of gravity, tears eventually form a small "lake" running along the edge of the lower eyelid. This lake drains through little holes in the eyelid called puncta, through some "underground tubing" in the skin and eventually into the nose. This drainage pathway is called the nasolacrimal system, and is the reason when we have runny eyes, we tend to have a runny nose as well. If this pathway becomes blocked, the tears have nowhere to drain, instead welling up in the eye and even running down the cheek. In adults, nasolacrimal duct (NLD) obstruction can be temporary if from allergic soft tissue swelling or permanent if caused by scarring from a prior infection. Many children are born with a temporary NLD obstruction at birth that eventually resolves during the first year (but may also require probing to manually force open). In adults, NLD obstruction often requires a surgical procedure called a dacryocystorhinostomy (DCR for short). This surgery involves making a small incision on the skin and creating a new drainage pathway for the tears to enter the nose. This type of procedure is usually performed by an oculoplastic surgeon, though occasionally ENT doctors will perform the same procedure.
Natamycin. Also known as pimaricin, this is the only commercially prepared eye drop available for fungal eye infection. While effective, it can sometimes be hard to obtain and can be expensive. The main alternative we use is amphotericin B ... but this drug isn't easy to obtain either as it has to be especially prepared by a compounding pharmacy.
nearsightedness. This is a refractive error where the eyes see well at near distance, but have a hard time seeing far away. Normally, the eye works like a camera with light entering the eye being focused perfectly on the retina. The retina is analogous to the film in a camera and located at the back of the eye. When a person is nearsighted, however, light wants to focus in front of the retina and visual images look blurry. By weakening the eye's overall focusing power with glasses (using negative diopter power lenses) light can focus properly on the retina. Extremely nearsighted eyes tend to be longer or larger than average, which puts them at slightly increased risk for retinal detachment. The prevalence of nearsightedness seems to be increasing in our society ... the reason for this is not entirely clear, but it may have something to do with the increase in near activities (i.e., iPads and Game Boys).
Neomycin/Polymyxin/Dexamethasone - An inexpensive combination drop containing two antibiotics to treat infection combined with a mild steroid for inflammation. This drug is available as an eye drop or an ointment. While most tolerate this medicine, some people have a sensitivity to the neomycin component. For these people, Tobradex or Zylet may be a better option. The trade name for this medicine is Maxitrol, which is still used to describe this medicine as it is easier to pronounce. This drug is on the $4 generic list at Walmart.
Neosporin. This is a combination antibiotic ointment containing neomycin, bacitracin, and polymyxin. While relatively effective as a broad pectrum antibiotic, some people have an allergy or sensitivity to neomycin. In these cases, Polysporin (which only contains bacitracin and polymyxin) can be used to good effect. I rarely prescribe this medicine given the plethora of good antibiotic drops and ointments available that have less side effects.
neovascularization. This is when abnormal blood vessels grow inside the eye. The eye is a very metabolically active organ. It continuously works and detects light, even while sleeping. In some ways the eye works like the heart ... in the sense that it is "always on." As such, the eye, especially the retina, requires a rich blood supply to function properly. The retina doesn't have a collateral blood supply. It only gets its blood and oxygen nourishment from a couple of sources. If there is a disruption to this blood supply, the retina quickly becomes starved for oxygen and can die. Many things can disrupt the blood flow to the eye. Diabetic retinopathy, blood clots, and macular degeneration can interfere with the blood supply to the retina. In all of these cases, the retina becomes "hungry" for oxygen and responds by pumping out "vascular endothelial growth factors" or VEGFs. These are natural hormonal stimulants for the growth of new blood vessels inside the eye. Normally, this would be great as new blood vessels could bring in fresh blood and keep the retina well-nourished, but it doesn't work this way. The new blood vessels grow quickly and are abnormal, with a tendency to leak, bleed, and contract causing vitreous hemorrhages, macular edema, and even retinal detachments. It is the VEGFs that cause neovascularization. To combat neovascularization, eye doctors try to decrease VEGF production. PRP laser can be performed to destroy these tissues. For more localized neovascularization at the macula, anti-VEGF injection medicines like Avastin are now being used extensively in the eye and this has drastically improved the treatment for "wet" macular degeneration.
neovascular glaucoma. With neovascularization, abnormal blood vessels grow inside the eye, causing significant retinal damage. These blood vessels can also grow into the front of the eye, covering the surface of the iris, and into the trabecular meshwork drain. If this drain becomes blocked with abnormal vessels, aqueous fluid can't exit back into the blood stream. This causes extremely high pressure inside, leading to acute glaucoma. Neovascular glaucoma is very difficult to treat as the pressure is recalcitrant to normal glaucoma drops. In these cases, a tube-shunt procedure is often required to create a new drainage pathway out of the eye. There are several causes for neovascular glaucoma but the most common is after a central retinal vein occlusion.
nepafenac. Known by the trade name Nevanac, this is an anti-inflammatory NSAID eye drop that is commonly used after cataract surgery to cool the eye down and decrease the chance of macular edema.
Neptazane. Also called methazolamide, this is a water pill used in the treatment of glaucoma. It is a carbonic anhydrase inhibitor that works by decreasing the production of aqueous fluid inside the eye. This medicine has the same mechanism of action as Diamox (acetazolamide).
Nevanac. Also known as nepafenac, this is an NSAID anti-inflammatory eye drop. It is commonly used after cataract surgery to cool the eye down and decrease the risk of post-operative macular edema.
NSAID. This stands for Non-Steroidal Anti-Inflammatory Drug. NSAIDs are very common. In fact, most over the counter pain relievers such as aspirin, Motrin (ibuprofen), and Tylenol are NSAIDs. In the eye, NSAID eye drops are used for pain control, but are most often used after cataract surgery to decrease the possibility of macular edema. Common NSAID eye drops include Acular, Nevanac, diclofenac, and Bromday.
numbing drops. These are eye drops used to anesthetize the surface of the eye. They are commonly used during an eye exam to help check the eye pressure (see applanation tonometry) and to numb the eye prior to eye surgery. See anesthetic drops for more information on this topic.
nystagmus. This is an involuntary, rhythmic "to and fro" movement of the eyes. Most nystagmus are in the horizontal axis, such that the eyes are constantly moving to the left and right. There are many causes for this abnormal eye movement, though most nystagmus occur secondary to congenital motor deficits that begin in childhood. Sensory nystagmus can occur in a child who is born with poor vision and is associated with many other congenital visual defects such as albinism. Nystagmus that develop later in life are rare and can be caused by vestibular (inner ear) abnormalities, drug toxicities (including alcohol), or more serious neurologic problems like a tumor or stroke. Police officers sometimes look for nystagmus with their field sobriety tests, looking for horizontal nystagmus while asking people to look to their right and left.