Eye Dictionary: H
H
headaches. Headaches are common and their cause is difficult to ascertain. There are a couple of ocular conditions that can exacerbate headaches. If the eyes are out of alignment (a condition called strabismus) the constant eye muscle strain of looking straight ahead can cause a tension headache. Prism glasses or eye exercises may help with this. If the eyes have a refractive error (like nearsightedness or farsightedness) the strain of focusing can also cause a headache. Updating glasses or contacts may help in these cases. There is also a condition called pseudotumor cerebri that causes headaches because the fluid pressure inside the skull is too high. This disorder is hard to diagnose short of doing a spinal tap and measuring the "opening pressure" of fluid coming out. However, IF the intracranial pressure is high, fluid tends to travel up the optic nerve and swelling can be seen at the optic disk inside the eye during a dilated retina exam. Ocular migraines are headaches associated with visual changes or "auras" and are usually secondary to harmless spasms of blood vessels at the eye and brain. Finally, in elderly patients, headaches associated with scalp tenderness or general malaise (not feeling well) can occasionally be associated with a more serious condition called temporal arteritis, which may require oral steroids.
herpetic eye disease. Herpes simplex virus (HSV) can cause cold sores around the mouth and can sometimes affect the eye. When the eye is involved we typically see a dendritic corneal ulcer on the surface of the eye. We call it "dendritic" because the infection forms a classic fernleaf pattern on the cornea. Initial episodes cause eye irritation and a foreign body sensation, though repeat bouts are less painful due to viral deadening of the eye nerves. Deep and repeated infections can cause corneal scarring that may lead to permanent vision loss. The treatment for herpetic eye disease is usually a combination of topical antiviral drops such as Viroptic or Zirgan and an oral antiviral like acyclovir or Valtrex. Whenever we diagnose "herpes virus" in the eye, I like to stress to my patients that this is NOT a sexually transmitted disease that they've caught! These viral infections are almost always an activation of HSV-1 (the non-sexual variety of herpes). The majority of the U.S. population is seropositive for HSV-1 with the virus lying dormant in the base of nerves. Only in some people does the virus activate enough to cause skin and eye manifestations. The triggers for this are unknown, but there aremany theories about emotional stress, hormones, or environmental conditions that might bring it out.
homatropine. This is a long-acting dilating drop with cycloplegia effects. We sometimes use this to treat eye pain (photophobia), especially when the cause is internal ocular inflammation from uveitis.
Horner's syndrome. This is a pupil abnormality where the eye loses its sympathetic nervous system innervation. The sympathetic system helps the body function during stressful situations ... it is our "fight or flight" system. Sympathetic stimulation helps the heart beat faster and routes blood to the musculoskeletal system so we can run faster. In the eye, the sympathetic system makes the pupils dilate and the eyelids widen ... presumably so that we can see better in the dark as we run away from attacking grizzly bears. If the sympathetic connections to the eye are blocked, the pupil doesn't dilate well and the pupil looks small and constricted. Also, the eyelid droops a little (ptosis). The sympathetic nerves involved are very long, with a circuitous route from the brain, running down the neck, over the lung, and back up to the eyeball. Any obstruction in this pathway, such as a lung tumor, carotid artery dissection, or even a congenital malformation, can cause a Horner's pupil. This diagnosis is made in the office by examining the pupils in light and dark conditions. The location of the sympathetic nerve 'blockage' can sometimes be localized using stimulant eye drops. More imaging, like a CAT scan or MRI may be required if the cause for the Horner's is not immediately obvious.
HRT. HRT stands for Heidelberg Retinal Tomograph ... but this is hard to pronounce so we just call it "HRT". This is an imaging test used primarily to photograph the optic disk in people with glaucoma. The HRT uses a scanning laser to create a three-dimensional map of the optic nerve that can be used to track glaucomatous cupping and detect nerve damage from advancing glaucoma. The laser photograph is painless and safe. HRT can also stand for "hormone replacement therapy" or "hostage rescue team."
HSV. This stands for herpes simplex virus and comes in two varieties. HSV-1 is usually considered the non-sexually transmitted herpes that causes cold sores. HSV-2 is the sexually transmitted variety that causes genital lesions. We typically see HSV-1 related infections when the virus activates in the eye. See herpetic eye disease for more information on this topic.
Humphrey visual field (HVF). A machine used to detect problems with peripheral vision. See visual field for more information on this common office test.
hyperopia. A fancy way of saying farsightedness. This means that you see far away better than close-up. See the entry on farsightedness for more details.
hyphema. This is bleeding inside the eye, occurring after trauma or spontaneously from neovascularization (abnormal blood vessels inside the eye). With a hyphema, blood leaks from internal blood vessels and pools in the front part of the eye (the anterior chamber). If there is enough blood, gravity causes the blood to sink into a visible 'layer.' A hyphema is easy to see under a microscope and can sometimes be detected with the naked eye. This is contrast to a vitreous hemorrhage in the back of the eye that can only be detected during a dilated eye exam. Blood cells can clog the aqueous "drain" and cause a temporary glaucoma, so treatment is geared toward lowering the eye pressure with glaucoma eye drops. Steroid drops are also used to decrease inflammation. Occasionally, dilating drops are used for pain control (a process called cycloplegia) and to keep the pupil edge from scarring down and forming iris synechiae. Hyphema bleeding usually occurs from a leaking blood vessel in the iris. A clot will form to stop this bleeding. After three to five days, however, this clot begins to break down and the eye is at risk for a 'rebleed.' For this reason, we will typically check the eye several times during the first week to monitor pressure and hyphema status. Anyone with enough trauma to cause a hyphema is at risk for developing chronic open angle glaucoma secondary to microscopic damage to the trabecular meshwork drain. After the eye has healed, we may look at this drain via gonioscopy to see if there is any obvious damage that can be seen.
herpetic eye disease. Herpes simplex virus (HSV) can cause cold sores around the mouth and can sometimes affect the eye. When the eye is involved we typically see a dendritic corneal ulcer on the surface of the eye. We call it "dendritic" because the infection forms a classic fernleaf pattern on the cornea. Initial episodes cause eye irritation and a foreign body sensation, though repeat bouts are less painful due to viral deadening of the eye nerves. Deep and repeated infections can cause corneal scarring that may lead to permanent vision loss. The treatment for herpetic eye disease is usually a combination of topical antiviral drops such as Viroptic or Zirgan and an oral antiviral like acyclovir or Valtrex. Whenever we diagnose "herpes virus" in the eye, I like to stress to my patients that this is NOT a sexually transmitted disease that they've caught! These viral infections are almost always an activation of HSV-1 (the non-sexual variety of herpes). The majority of the U.S. population is seropositive for HSV-1 with the virus lying dormant in the base of nerves. Only in some people does the virus activate enough to cause skin and eye manifestations. The triggers for this are unknown, but there aremany theories about emotional stress, hormones, or environmental conditions that might bring it out.
homatropine. This is a long-acting dilating drop with cycloplegia effects. We sometimes use this to treat eye pain (photophobia), especially when the cause is internal ocular inflammation from uveitis.
Horner's syndrome. This is a pupil abnormality where the eye loses its sympathetic nervous system innervation. The sympathetic system helps the body function during stressful situations ... it is our "fight or flight" system. Sympathetic stimulation helps the heart beat faster and routes blood to the musculoskeletal system so we can run faster. In the eye, the sympathetic system makes the pupils dilate and the eyelids widen ... presumably so that we can see better in the dark as we run away from attacking grizzly bears. If the sympathetic connections to the eye are blocked, the pupil doesn't dilate well and the pupil looks small and constricted. Also, the eyelid droops a little (ptosis). The sympathetic nerves involved are very long, with a circuitous route from the brain, running down the neck, over the lung, and back up to the eyeball. Any obstruction in this pathway, such as a lung tumor, carotid artery dissection, or even a congenital malformation, can cause a Horner's pupil. This diagnosis is made in the office by examining the pupils in light and dark conditions. The location of the sympathetic nerve 'blockage' can sometimes be localized using stimulant eye drops. More imaging, like a CAT scan or MRI may be required if the cause for the Horner's is not immediately obvious.
HRT. HRT stands for Heidelberg Retinal Tomograph ... but this is hard to pronounce so we just call it "HRT". This is an imaging test used primarily to photograph the optic disk in people with glaucoma. The HRT uses a scanning laser to create a three-dimensional map of the optic nerve that can be used to track glaucomatous cupping and detect nerve damage from advancing glaucoma. The laser photograph is painless and safe. HRT can also stand for "hormone replacement therapy" or "hostage rescue team."
HSV. This stands for herpes simplex virus and comes in two varieties. HSV-1 is usually considered the non-sexually transmitted herpes that causes cold sores. HSV-2 is the sexually transmitted variety that causes genital lesions. We typically see HSV-1 related infections when the virus activates in the eye. See herpetic eye disease for more information on this topic.
Humphrey visual field (HVF). A machine used to detect problems with peripheral vision. See visual field for more information on this common office test.
hyperopia. A fancy way of saying farsightedness. This means that you see far away better than close-up. See the entry on farsightedness for more details.
hyphema. This is bleeding inside the eye, occurring after trauma or spontaneously from neovascularization (abnormal blood vessels inside the eye). With a hyphema, blood leaks from internal blood vessels and pools in the front part of the eye (the anterior chamber). If there is enough blood, gravity causes the blood to sink into a visible 'layer.' A hyphema is easy to see under a microscope and can sometimes be detected with the naked eye. This is contrast to a vitreous hemorrhage in the back of the eye that can only be detected during a dilated eye exam. Blood cells can clog the aqueous "drain" and cause a temporary glaucoma, so treatment is geared toward lowering the eye pressure with glaucoma eye drops. Steroid drops are also used to decrease inflammation. Occasionally, dilating drops are used for pain control (a process called cycloplegia) and to keep the pupil edge from scarring down and forming iris synechiae. Hyphema bleeding usually occurs from a leaking blood vessel in the iris. A clot will form to stop this bleeding. After three to five days, however, this clot begins to break down and the eye is at risk for a 'rebleed.' For this reason, we will typically check the eye several times during the first week to monitor pressure and hyphema status. Anyone with enough trauma to cause a hyphema is at risk for developing chronic open angle glaucoma secondary to microscopic damage to the trabecular meshwork drain. After the eye has healed, we may look at this drain via gonioscopy to see if there is any obvious damage that can be seen.