How to perform a Clinical Eye Exam


Examination of the eye in a clinical environment can involve a number of separate tests, but is usually guided by the patient’s presenting complaint or requirements (e.g. vision needs to be assessed for ability to drive).

It is important to note that examination of the eye can also provide clues to diseases and disorders well beyond the eye itself. Ophthalmoscopic examination is a useful skill that is not just limited to neurological and eye examinations. Changes on fundoscopy can also be seen in systemic diseases such as hypertension and diabetes.

Taking a History
When approaching an eye examination, there are three basic things that should be investigated when taking a history. That is, does the eye,
  • See right (e.g. Diplopia, Transient Loss of Vision (Amaurosis Fugax), Flashing Lights, Photophobia)
  • Look right (e.g. yellow sclera: jaundice, red eye: conjunctivitis)
  • Feel right (e.g. pain, dry eyes, etc)
It is also important to specifically consider ocular history (e.g. contact lens or glasses/visual aids, lazy eye’ as a child, etc). These aspects form the foundations of any history taking concerning the eye, and you would proceed with the history (PMHx, FHx, etc) as per any other medical condition.

Common presenting complaints associated with the eye can be remembered as DAMPCHNFFS.
  • Diplopia
  • Amaurosis
  • Mists
  • Pain
  • Colour vision disturbance
  • Haloes
  • Night Blindness
  • Flashes
  • Floaters
  • Scotomata

Basic Eye Anatomy & Physiology
Anatomy of the Eye (Chabacano on Wikipedia)

Internal Eye (Normal Fundus. From the University of Michigan)

Ocular Muscles
Extrinsic Muscles that move the eye are; Lateral Rectus (innervated by CN6), Superior oblique (innervated by CN4), Superior rectus (innervated by CN3), Medial rectus (innervated by CN3), Inferior rectus (innervated by CN3) and Inferior oblique (innervated by CN3). The diagram below highlights the bony orbit and the location of some these muscles. Nerves are also identifiable.

Adapted from Patrick J. Lynch on Wikipedia

Intrinisic eye muscles: Ciliary (innervated by CN3), Sphincter pupillae (innervated by CN3) and Dilator pupillae (innervated by Superior cervical ganglion - T1)

Visual Pathway

Light Reflex: Shining light into one eye causes constriction of iris muscles on both sides

Accommodation Reflex: Directing eyes from a distant object to a near object causes constriction of iris muscles on both sides.

Vestibulo-Ocular Reflex: Moving the head causes movement of the eyes to maintain a stable image during rapid head movement.

The Basic Performa
Ideally, the eye examination consists of a number of elements shown in the diagram below.

Elements of the Eye Exam
External Examination of the Eye
External examination of eyes consists of inspection of the eyelids, surrounding tissues and palpebral fissure.

Remember the four L’s: lymph nodes, lacrimal apparatus, lids and lashes

Visual Acuity
Assessing the subject’s visual acuity is important as it provides a context for other elements of the exam. Visual acuity is typically assessed by a Snellen chart (which can be hand held or mounted) in the clinical environment, but other charts types (e.g. Allen figures, illiterate E charts, Landolt C, etc) are also used. A pinhole test will improve vision with most refractive errors.

Other charts are usually used to accommodate the patient’s unique knowledge (e.g. English maybe a second language) and mental capacity, so as to provide an indication of visual acuity without a requirement to read or verbalise.

Visual acuity is measured by comparing the person’s ability to see objects at standardised distances. The standard definition of normal visual acuity is 20/20 (US) or 6/6 vision (typically used in Europe & Australia as it refers to metres). Often Snellen Charts will have these values (e.g. 6/5, 6/6, 6/12) along the side.

Australian Law requires that drivers have a corrected visual acuity of 6/12 or better in both eyes. This means that they must be able to at least see an object or person at 6 metres, that a normal person could see at 12 metres.

Each eye should be tested separately with a chart while the other is covered.

It is essential to always get the patient’s best corrected visual acuity. That is, allow them to wear their contacts or glasses.

Heirarchy for low vision
Snellen acuity –> count fingers –> hand motion –> light perception –> no light perception

Pupillary Function
Assessment of pupillary function includes examining the pupils for equal size, regular shape, reactivity to light (direct & consensual) and accommodation. It is important to test for relative afferent pupillary defect (RAPD) by swinging your pen torch from pupil to pupil. The video below demonstrates a patient with this defect.

These steps can be easily remembered with the mnemonic PERRLA: Pupils Equal and Round; Reactive to Light & Accommodation.

Ocular motility
The effective movement of the eyes should be tested to ascertain whether a problem exists either within the ocular muscles, or the nerves that supply them. Knowing these muscles and their innervations is obviously crucial to understanding any abnormalities that arise during testing. A useful mnemonic for remembering the muscles and their innervations is LR6SO4R3. Where the numbers refer to the cranial nerves; LR equals Lateral Rectus; SO equals Superior Oblique; and R equals all other ocular muscles.

Slow tracking or "pursuits" are assessed by the 'follow my finger' test, in which the examiner's finger traces an imaginary "double-H", which touches upon the eight fields of gaze.

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.

Intraocular Pressure
Glaucoma, characterized by elevated intraocular pressure, optic disk cupping and atrophy, and loss of vision, is one of the three leading causes of acquired blindness in the Western world. Tonometry is the fundamental screening test for detecting elevated intraocular pressure.

Ophthalmoscopic examination may include visually magnified inspection of the internal eye structures and also assessment of the quality of the eye's red reflex.


Other Tests
Common tests include the HRR pseudoisochromatic plates or the Ishihara plates. The City University Color Vision Test is nearly able to adequately provide an indication of the severity of all colour deficiencies.

Further Resources
Also checkout the 35 Golden Rules of EyeCare.

Other Clinical Exams
Cardiovascular | Respiratory | Gastrointestinal | Neurological | Musculoskeletal

    1 comment:

    1. This is why I'm happy I have an Optometrist to do my eye exam in Edmonton. This was all over my head.