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Eye examination

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An eye examination is a specialized series of clinical tests. These tests assess visual acuity and the ability to focus on near and far objects. They also evaluate the overall health of the ocular structures. Professionals such as optometrists, ophthalmologists, or orthoptists typically perform these evaluations. Regular examinations are vital because many eye diseases are asymptomatic. This means a person may have a disease without feeling any symptoms.

Recruitment and Enlistment in Britain, 1914-1918 Q30063
Recruitment and Enlistment in Britain, 1914-1918 Q30063

For a healthy individual, routine exams might occur once in their 20s and twice in their 30s.

A comprehensive eye exam begins with a detailed medical history. This is an essential first step for identifying systemic health connections. Many eye conditions are linked to diseases in other parts of the body. For example, diabetes mellitus can lead to diabetic retinopathy or early cataracts. Longstanding hypertension can cause microvascular damage in the retina, known as hypertensive retinopathy. Severe malignant hypertension can cause papilledema, which is swelling of the optic nerve. This condition is a medical emergency that can lead to blindness.

Retina photo of a left eye, patient with severe Idiopathic Cranial Hypertension (aka Psuedotumor Cerebri)
Retina photo of a left eye, patient with severe Idiopathic Cranial Hypertension (aka Psuedotumor Cerebri)

Providers also ask about personal history, such as eye trauma or previous surgeries like cataract or glaucoma procedures.

After the history, the examiner moves through specific clinical steps. The first step is measuring visual acuity, which is the ability to see fine details. This is often done using a Snellen or LogMAR chart.

Leasamples
Leasamples

If a patient cannot read the chart, clinicians use alternative methods. They might use "count fingers" (CF) or "hand motion" (HM) tests. In severe cases, they check for "light perception" (LP) or "no light perception" (NLP). Visual acuity is recorded as a fraction, such as 20/20. This means the person sees at 20 feet what a normal person sees at 20 feet.

Man at Phoropter
Man at Phoropter

The next step involves checking pupil function and eye movement. Doctors use the mnemonic PERRLA to check if pupils are equal, round, and reactive to light and accommodation. A swinging-flashlight test can help detect an afferent pupil defect, also called a Marcus Gunn pupil.

CCMDonation11
CCMDonation11

This test is useful for assessing optic nerve anomalies. The examiner also tests extraocular motility, which is how the eye muscles move. They check the nine cardinal directions of gaze to test muscles like the rectus and oblique muscles. They may also check saccades, which are the quick "jumps" the eyes make between targets. This helps ensure the eyes can move smoothly for tasks like reading.

Pressure within the eye must also be measured. The eye is an enclosed compartment with circulating fluid that maintains internal pressure. This is measured using tonometry. A common method is Goldmann applanation tonometry (GAT).

Goldmann mires
Goldmann mires

During this process, the clinician uses a prism to gently flatten the central cornea. The tear film is often stained with fluorescein dye to help the view. The normal range for intraocular pressure is between 10 and 21 mmHg. High pressure is a concern because certain medications, like corticosteroids, can increase it and lead to glaucoma.

Slit-lamp Examination
Slit-lamp Examination

Examiners also check the visual field and the external structures of the eye. Confrontational visual field testing assesses the peripheral vision.

Approximately view field of a right normal eye
Approximately view field of a right normal eye

The patient covers one eye and counts fingers flashed in different quadrants. This helps detect issues like scotoma, which is an area of reduced vision, or hemianopia, where half the field is lost. Finally, an external examination inspects the eyelids and surrounding tissues. The doctor looks for things like ptosis, which is an asymmetry in eyelid position. They may also perform a slit-lamp examination or a fundoscopic examination through a dilated pupil to see the internal structures clearly.

Fully dilated eye during eye exam
Fully dilated eye during eye exam

Understanding eye health requires looking at genetics and medication use. Certain diseases, such as glaucoma or age-related macular degeneration, often run in families.

Intermediate age related macular degeneration
Intermediate age related macular degeneration

Medications also play a significant role in eye health. For instance, patients taking hydroxychloroquine for lupus or rheumatoid arthritis need annual exams after five years of use. This is because the drug can cause ocular side effects. By combining medical history, muscle testing, and pressure measurements, eye exams provide a complete picture of ocular and systemic health.

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🖼️ Images & Media (10)
File:Intermediate age related macular degeneration.jpg
Intermediate age related macular degeneration.jpg
File:Recruitment and Enlistment in Britain, 1914-1918 Q30063.jpg
Recruitment and Enlistment in Britain,...
File:CCMDonation11.JPG
CCMDonation11.JPG
File:Goldmann mires.jpg
Goldmann mires.jpg
File:Approximately view field of a right normal eye.jpg
Approximately view field of a right normal eye.jpg
File:Slit-lamp Examination.jpg
Slit-lamp Examination.jpg
File:Fully dilated eye during eye exam.jpg
Fully dilated eye during eye exam.jpg
File:Retina photo of a left eye, patient with severe Idiopathic Cranial Hypertension (aka Psuedotumor Cerebri).jpg
Retina photo of a left eye, patient with...
File:Man at Phoropter.jpg
Man at Phoropter.jpg
File:Leasamples.jpg
Leasamples.jpg
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