Causes of Vision Loss Flashcards
What are some common complaints pts used to say they are having loss of central vision?
Blurred Vision”
“Foggy Vision”
“Spot in My Vision”
“My Eyes are Weak”
Loss of vision can mean either loss of central vision or loss of part of the visual field. Patients may use many different ways of describing their visual complaints. Unfortunately, different patients will mean different things by the terms they use. In general, when a patient has blurred, out of focus vision, they will use the term “blurred,” “foggy,” or “smoky” vision. When they talk about a “spot in my vision” they may be describing a scotoma (blind spot) in their vision or a “floater.”
How can you differentiate between scotoma and a floater?
Scotomas will move exactly as the eye moves, while floaters will continue to float around after movement of the eye stops.
Loss of vision, either central or in the visual field, occurs when there is pathology somewhere along the visual pathway. While systemic diseases may affect the vision, they do so by impacting the visual system in some way.
It is helpful to remember this diagram when you are evaluating a patient with visual loss. The type of visual loss (central, peripheral, unilateral, or bilateral) is determined by the location of the pathologic process and its severity. The diseases may be intrinsic such as demyelinating diseases or extrinsic such as expanding masses pressing on visual pathway structures. Ischemia or toxins may also affect discrete or expansive areas along the visual pathway.
Obtaining the history of lateralization, rapidity of onset, past ocular problems, and visual distances affected by the visual loss is essential in arriving at a reasonable diagnosis.
If the vision is affected only at near or distance, the cause is usually a refractive error. Damage to the visual pathways will most often cause a corresponding loss of vision at all distances.
Other important facts to explore are whether the visual loss is transient, intermittent and recurrent, or constant. If the visual loss is transient, determining the duration of the visual loss is essential. Transient ischemic attacks (TIAs) affecting the vision in one eye usually last how long? What causes them?
5 to 10 minutes and are usually the result of platelet thrombin emboli from atheromatous plaques in the carotid artery on the same side.
These episodes are know as “amaurosis fugax” which means fleeting loss of vision.
Transient loss of vision in both eyes SIMULTANEOUSLY should lead the physician to suspect what?
basilar artery insufficiency.
Short-lived loss of vision in one eye (a few seconds) is usually associated with what?
papilledema.
Recurrent episodes of vision loss with “sparkling lights” that begin in a small area on one side then enlarge over 25 to 45 minutes (scintillating scotoma) followed by headache, nausea, vomiting are typical of:
migraine attacks.
There is a sizable subset of these patients who have only the visual symptoms without the headache etc.
Constant visual loss implies what?
that there is an ongoing process that is in the process of damaging structures utilized for vision or has permanently interfered with the function of the visual pathways.
The presence or absence of pain associated with loss of vision is also an important fact to elucidate. Some examples of painless loss of vision would be:
cataract, central retinal artery or vein occlusion, or retinal detachment.
Compression of the visual pathway by tumors may or may not cause pain depending on the tumor’s relationship to sensory nerves.
Pain on eye movement accompanied with loss of central vision and a relative afferent pupillary defect are common findings in patients with what disease?
optic neuritis.
Pain associated with loss of vision may occur during attacks of:
acute narrow angle glaucoma, anterior uveitis (iritis), endophthalmitis (infection in the interior of the eye), or neovascular glaucoma.
A gradual progressive loss of vision should always be investigated. Why?
While it may indicate local ocular pathology such as cataract or macular degeneration, it should always be remembered that it could also be an expanding intracranial mass compressing part of the visual pathway.
Sudden loss of vision in one eye in older adults (over 50 years of age) is usually the result of:
arterial or venous occlusion, while unilateral visual loss in a younger patient is more likely caused by optic neuritis.
____________ must be ruled out in younger patients with optic neuritis.
A demyelinating disease
What are the most common causes of blurred vision due to?
ocular problems:
need for glasses
cataract and macular degeneration as pts age
amblyopia (lazy eye)
trauma
Visual acuity is measured by the ability of the patient to read standard sized letters or symbols at a specified distance. The Snellen eye chart viewed at what disease?
20 feet (6 meters) is today’s standard, although other charts are available that are acceptable. The visual acuity fraction has the testing distance in the numerator and the size of the test letter/symbol in the denominator.
The letter/symbol size is such that the letter/symbol subtends the same visual angle at that distance as does the letter/symbol on the 20/20 line does at 20 feet. Thus a 20/50 letter is 2.5 times the size of a 20/20 letter and could be read at a distance of 50 feet by a person with 20/20 vision.
Rules on testing visual acuity
- measure each eye seperately
- The patient should wear corrective eyewear if they have such (Be careful not to have them read the distance chart when they have glasses for reading only, as the reading glasses will blur their distance vision)
- If they wear bifocals they should be looking through the top portion of their glasses to read the distance chart and the lower bifocal segment if you are checking the vision with a near card.
- If the patient is unable to read the largest letter have them move closer to the chart. Measure the distance; this becomes the numerator of the visual acuity fraction. The size of the largest letter/symbol becomes the denominator. The letter/symbol size is printed on the eye chart. For example if the patient is 8 feet from the chart and the largest letter on the chart is 20/200, the vision is recorded as 8/200
If the patient still is unable to read the largest letter, then what should you do?
Determine at what distance the patient can count your fingers and record that.
If they cannot count your fingers, then move your hand back and forth and up and down about one foot in front of their eye. If they are able to tell you when the motion starts and/or stops or which direction your hand is moving, then the vision is recorded as Hand Motion (HM).
If they are unable to see you hand moving, then determine if they can tell when your light goes on and off. If they can tell when the light goes on or off, then the vision is recorded as Light Perception (LP). Failure to perceive that the light is on is noted as No Light Perception (NLP).
On the left of this slide we see a representation of a distance Snellen Eye Chart. This chart should be viewed in good illumination at a distance of 20 feet (6 M).
On the right side we see a near card. While this particular card is viewed at 14 inches, there are some cards that are viewed at 16 inches. Be sure you know the proper distance at which your card is to be used. The proper distance is usually printed on the card.
Record the visual acuity on the medical record in the form you see here. It is essential that you document whether the visual acuity was measured with or without corrective lenses.
If you measure the visual acuity at near be sure to document in the medical record that this was a “near” vision measurement.
The examination of the pupil is important in evaluating a patient with visual loss. You should evaluate the size of each pupil, the symmetry of the sizes of the two pupils, and their shape and regularity. You should evaluate the direct, consensual (in most cases) responses of the pupils, and test for a the presence or absence of a Relative Afferent Pupillary Defect. If bilateral nonreactive pupils are discovered, the near reflex (miosis, convergence, accommodation) should also be tested.
T or F. Visual loss caused by a lesion posterior to the exit of the pupillary fibers will not be associated with abnormalities of the pupillary reflex.
T.
The presence of a non-reactive pupil in one eye that does not respond to consensual stimulation indicates what?
the presence of a defect in the efferent arc of the pupillary reflex as a cause for the non-reactive pupil.
If the non-reactive pupil reacts to consensual stimulation then the abnormal pupil is non-reactive due to defect in the afferent defect of the pupillary reflex.
The Relative Afferent Pupillary Defect (RAPD) is also an important observation in patients with visual loss. The presence of a RAPD usually is associated with diseases of what?ent.
the optic nerve, chiasm, or optic tract anterior to the exit of the pupillary fibers.
Widespread retinal diseases, especially arterial or venous occlusive disease, are often associated with a positive RAPD. Even patients with good direct pupillary reflexes in each eye may still have a positive RAPD.
Patients with retrobulbar optic neuritis have a normal appearance of their optic disc even though a positive (abnormal) RAPD is present
On the left is a photographic attempt to demonstrate how a central scotoma would appear to the patient. This is not totally accurate as the spot moves everywhere the patient moves the eye and the peripheral vision is not as clear.
On the right is a computerized visual field chart showing the central scotoma visual field defect. The dark area indicates that the patient is unable to see the test light in those areas. This scotoma connects with the physiologic blind spot and is known as a centrocecal scotoma.
Here are fundus photographs showing a normal disc on the left as you would find in patients with retrobulbar optic neuritis and a swollen disc in the right photograph as you would find in patients with papillitis.
This slide gives you some details about a bitemporal hemianopsia.
On these slides depicting visual field defects, the area enclosed by the solid lines is that area where the patient CAN SEE. The small dark circle on the right visual field chart is the physiologic blind spot.
When studying visual fields, the physician should view the field charts as if they were your visual fields, i.e. hold the right (OD) visual field in front of your right eye and the left (OS) visual field in front of your left.
The dotted line shows what would be the expected normal visual field size.
This slide gives you more details about an incongruous left homonymous hemianopsia. The more anterior the lesion is located in the post-chiasmal pathway the more incongruous the visual field defect generally is.
This slide gives you more details about a congruous left homonymous hemianopsia. The more posterior in the post-chiasmal pathway the lesion is the more congruous the visual field defect generally is.
The physician should be aware that one of the most common presenting complaints of a patient with a total hemianopsia as we see here is “I can’t see out of my left eye.” This complaint coupled with good central visual acuity and normal pupillary reaction should alert the physician to the good possibility of a dense homonymous hemianopsia. In older patients this finding is almost always associated with a loss of perfusion to the occipital cortex on the opposite side of the field defect.
This is an attempt to show you what the patient with a left homonymous hemianopsia experiences.
Any patient with loss of vision should have an ophthalmoscopic examination of the interior of the eye. Listed on this slide are some of the characteristics of the optic disc that the physician should evaluate.
This slide shows a normal optic disc with medium sized optic cup. Along the right side of the slide are the four C’s of the optic cup along with other areas of the ocular fundus to be examined
What are the fundoscopic findings of papilledema?
- Both Discs Elevated and Hyperemic
- Disc Margins Blurred, Indistinct
- Small Vessels at Margin Obscured
- Retinal Vessels Tortuous, Dilated
- Hemorrhages and Exudates
- Spontaneous Venous Pulsations Absent
This photograph shows the pale swollen optic disc of a patient with ischemic optic neuropathy.
Sudden loss of vision may indicate the presence of a central retinal artery or vein occlusion. Describe the findings of central retinal artery occluson.
The retina in the patient’s eye with a central retinal artery occlusion will be pale due to swelling secondary to the ischemia. The optic disc will be pale and the arteries narrowed. The macula will have the typical “cherry-red spot” appearance. These findings are the result of an ischemic infarct of the retina. As with ischemic optic neuropathy, temporal arteritis must be ruled out. Emergency treatment may result in visual recovery, but this is rarely effective.
What are the findings of central retinal vein occlusion?
A central retinal vein occlusion causes a hemorrhagic infarct of the retina. The disc is swollen and hyperemic with prominent venous distention and flame-shaped and other hemorrhages. No emergency treatment has been found effective for this process.
Notice the pallor of the optic disc in the left photograph when compared to the photograph on the right. It is imperative that you look at both eyes to see if a difference exist in the appearance of the optic discs.
This slide shows the typical early visual field defects in chronic open angle glaucoma. The cross hatched sections are areas which the patient DOES NOT SEE (scotomata). The scotomata have the arcuate pattern because of the anatomical orientation of the axons in the retina.
Like the vascular supply, the axonal distribution is oriented along the horizontal meridian.
Notice that the physician will NOT discover these visual defects with confrontation visual field testing nor will the patient be aware of them.
As the disease progresses the peripheral field is gradually lost. The central few degrees are the last portion of the visual field to be lost.
The photographs on the left show a normal optic disc and optic cup. The lower left photograph show the location of the optic cup in this optic nerve.
The photograph on the right shows advanced cupping of the optic nerve head indicating severe damage to the optic nerve. This patient probably has extensive loss of the peripheral visual field and, in spite of good central vision, will have difficulty in moving about.
