Eye examination
An eye examination, commonly known as an eye test, is a series of tests performed to assess vision and ability to focus on both far and near and discern objects. It also includes other tests and examinations of the eyes. Eye examinations are primarily performed by an optometrist, ophthalmologist, or an orthoptist.
Health care professionals often recommend that all people should have periodic and thorough eye examinations as part of routine primary care, especially since many eye diseases are asymptomatic. Typically, a healthy individual who otherwise has no concerns with their eyes receives an eye exam once in their 20s and twice in their 30s.
Eye examinations may detect potentially treatable blinding eye diseases, ocular manifestations of systemic disease, or signs of tumors or other anomalies of the brain.
A full eye examination consists of a comprehensive evaluation of medical history, followed by 8 steps of visual acuity, pupil function, extraocular muscle motility and alignment, intraocular pressure, confrontational visual fields, external examination, slit-lamp examination and fundoscopic examination through a dilated pupil.
A minimal eye examination consists of tests for visual acuity, pupil function, and extraocular muscle motility, as well as direct ophthalmoscopy through an undilated pupil.
Medical history
Collecting medical history is the first and an essential step in eye examination. Many eye conditions are associated with systemic health, and many diseases can have manifestations in the eye. Certain systematic medications can cause ocular side effects and warrant routine eye exams. Personal and family history of eye diseases can help providers identify individuals at higher risk, allowing for early interventions.Common chief complaints
Common chief complaints for an eye exam include vision loss, blurry vision, double vision, seeing flashes of light, and seeing floaters.Medical conditions
[Diabetes Mellitus]
Diabetes mellitus, or diabetes, can lead to changes in the eye. Individuals with diabetes can develop early cataract and diabetic retinopathy in the long term.[Hypertension]
Longstanding hypertension can contribute to microvascular damage of the blood vessels in the retina, leading to hypertensive retinopathy.Malignant hypertension can lead to papilledema, which is the swelling of the optic nerve. This is a medical emergency and can lead to blindness.
Autoimmune disorders
Autoimmune disorders can affect the eyes in different ways. Most commonly, Grave's disease can lead to Grave's ophthalmopathy or Thyroid Eye Disease. Sjogren's disease manifest as dry eye.Medication use
[Hydroxychloroquine]
Hydroxychloroquine, also known as Plaquenil, is an antimalaria medication commonly used to treat lupus and rheumatoid arthritis. Individuals who are on long-term hydroxychloroquine for more than 5 years are recommended to have a comprehensive eye exam annually. Patients usually receive a baseline exam before starting the medication to document their baseline eye condition as well.[Corticosteroid]s
Corticoteroids can have ocular side effects. It can increase the intraocular pressure, which can lead to glaucoma.Personal history of eye conditions
Collecting one's personal history of eye conditions provides valuable information for the eye examination. History of trauma to the eye, such as open globe injury, and prior surgeries, such as refractive surgeries, cataract surgeries, and minimally invasive glaucoma surgery procedures are usually gathered during an eye examination.Family history of eye conditions
A family history of glaucoma, age-related macular degeneration, and other inherited eye diseases are often collected, as these diseases have a genetic component.The 8-Point eye exam
Visual acuity
Visual acuity is the eyes ability to detect fine details and is the quantitative measure of the eye's ability to see an in-focus image at a certain distance. The standard definition of normal visual acuity is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc. The terms 20/20 and 6/6 are derived from standardized sized objects that can be seen by a "person of normal vision" at the specified distance. For example, if one can see at a distance of 20 ft an object that can normally be seen at 20 ft, then one has 20/20 vision. Likewise, if one can see at 20 ft what a normal person can see at 40 ft, then one has 20/40 vision. The 6/6 terminology is used in countries using the metric system, and that represents the distance in meters since 6 meters are roughly equal to 20 feet.This is often measured with a Snellen chart or LogMAR chart.Measuring visual acuity
Visual acuity is usually measured with a Snellen or LogMAR chart with a lit background to give the reader the best chance of detecting the optotypes. Distance visual acuity and near visual acuity are often measured separated. Usually, one eye is measured at a time, first without corrections, then with corrections.Best corrected visual acuity refers to the best visual acuity one can achieve with corrective lenses. When corrective lenses are not available, a pinhole is often used to simulate the effect of glasses. Any improvement from corrective lenses or/and pinholes are often documented to indicate the individual's refractive potential.The visual acuity is assigned in the form of a fraction. Visual acuity is recorded as "20/20" when all optotypes on a specific line of the eye chart are correctly identified. When an individual correctly identifies additional 2 letters in the next 20/30 lines, then they will be assigned 20/40+2. Alternatively, if an individual correctly identifies all optotypes on the 20/40 lines except 2, they will be assigned 20/40-2.
When an individual cannot read the chart, visual acuity is assessed using alternative methods that do not involve the chart. CF is used when an individual can see and count fingers at a certain distance. For example, CF@2 ft' refers to "count fingers at 2 feet". HM is used when an individual can only see the direction of hand movement close to the face. LP is used when an individual can only detect light but not shapes, motions or colors. NLP is assigned when an individual cannot detect any light.
Pupil function
An examination of pupilary function includes inspecting the pupils for equal size, regular shape, reactivity to light, and direct and consensual accommodation. These steps can be easily remembered with the mnemonic PERRLA : Pupils Equal and Round; Reactive to Light and Accommodation.A swinging-flashlight test may also be desirable if neurologic damage is suspected.
The swinging-flashlight test is the most useful clinical test available to a general physician for the assessment of optic nerve anomalies.
This test detects the afferent pupil defect, also referred to as the Marcus Gunn pupil. It is conducted in a semidarkened room.
In a normal reaction to the swinging-flashlight test, both pupils constrict when one is exposed to light.
As the light is being moved from one eye to another, both eyes begin to dilate, but constrict again when light has reached the other eye.
If there is an efferent defect in the left eye, the left pupil will remain dilated regardless of where the light is shining, while the right pupil will respond normally.
If there is an afferent defect in the left eye, both pupils will dilate when the light is shining on the left eye, but both will constrict when it is shining on the right eye. This is because the left eye will not respond to external stimulus, but can still receive neural signals from the brain to constrict.
If there is a unilateral small pupil with normal reactivity to light, it is unlikely that a neuropathy is present.
However, if accompanied by ptosis of the upper eyelid, this may indicate Horner's syndrome.
If there is a small, irregular pupil that constricts poorly to light, but normally to accommodation, this is an Argyll Robertson pupil.
Extraocular motility and alignment
Ocular motility should always be tested, especially when patients complain of double vision or physicians suspect neurologic disease. First, the doctor should visually assess the eyes for deviations that could result from strabismus, extraocular muscle dysfunction, or palsy of the cranial nerves innervating the extraocular muscles. Saccades are assessed by having the patient move his or her eye quickly to a target at the far right, left, top and bottom. This tests for saccadic dysfunction whereupon poor ability of the eyes to "jump" from one place to another may impinge on reading ability and other skills, whereby the eyes are required to fixate and follow a desired object.The patient is asked to follow a target with both eyes as it is moved in each of the nine cardinal directions of gaze. The examiner notes the speed, smoothness, range and symmetry of movements and observes for unsteadiness of fixation. These nine fields of gaze test the extraocular muscles: inferior, superior, lateral and medial rectus muscles, as well as the superior and inferior oblique muscles.
Intraocular pressure
can be measured by tonometry devices. The eye can be thought of as an enclosed compartment through which there is a constant circulation of fluid that maintains its shape and internal pressure. Tonometry is a method of measuring this pressure using various instruments. The normal range is 10-21 mmHg.Confrontational visual fields
Testing the visual fields consists of confrontation field testing in which each eye is tested separately to assess the extent of the peripheral field.To perform the test, the individual occludes one eye while fixated on the examiner's eye with the non-occluded eye. The patient is then asked to count the number of fingers that are briefly flashed in each of the four quadrants. This method is preferred to the wiggly finger test that was historically used because it represents a rapid and efficient way of answering the same question: is the peripheral visual field affected?
Common problems of the visual field include scotoma, hemianopia, homonymous hemianopsia and bitemporal hemianopia.