Examination of The Eye

Examination of the eye

Childhood vision screening
From birth through the teenage years, children's eyes are growing and changing quickly.
A newborn’s vision is mostly blurry, but the visual system develops over time and is fully formed in the teen years.
Newborn
a “red reflex” (like seeing red eyes in a flash photograph). If the bright light shone in each eye does not return a red reflex, more testing may be needed.
blink and pupil response

An ophthalmologist should do a comprehensive exam if the baby is:

born prematurely
has signs of eye disease
or a family history of childhood eye disease
6 to 12 months
do the tests mentioned above
visually inspect the eyes
check for healthy eye alignment and movement

3 to 5 years

Visual acuity (sharpness of vision, like 20/20 for example) should be tested as soon as the child is old enough to read an eye chart. Many children are somewhat farsighted (hyperopic), but can also see clearly even at distance.
5 years and older
At 5, children should be screened for visual acuity and alignment. Nearsightedness (myopia) is the most common problem in this age group. It is corrected with eyeglasses.
Eye drops are used to dilate (widen) the pupil during the exam. This gives your ophthalmologist a fuller view inside the eyes.


What Will Your Ophthalmologist Check During an Eye Exam?
visual acuity
Read an eye chart to determine how well you see at various distances. You cover one eye while the other is being tested. This exam will determine whether you have 20/20 vision or not.
Snellen test type for distance:
Normal visual acuity 6/6
Other test type:
Landolt ’s chart
E-Chart
Simple picture chart

Pupils

check how your pupils respond to light by shining a bright beam of light into your eye. Pupils usually respond by getting smaller. If your pupils widen or don't respond, this may reveal an underlying problem.
Eye movement
A test called ocular motility evaluates the movement of your eyes. Your ophthalmologist looks to see if your eyes are aligned. They also check that your eye muscles are working properly.
The term ocular motility refers to the study of the twelve extraocular muscles and their impact on eye movement. Each eye has six muscles, four rectus and two oblique, which, when functioning properly, allow the eyes to work together in a wide range of gaze
Eye pressure
Eye pressure testing, called tonometry, measures the pressure within your eye (intraocular eye pressure, or IOP). Elevated IOP is one sign of glaucoma. The test may involve a quick puff of air onto the eye or gently applying a pressure-sensitive tip near or against your eye.
Eye pressure is measured in millimeters of mercury (mm Hg). Normal eye pressure ranges from 10- 21 mm Hg.
Tonometry
is a test that measures the intraocular pressure (IOP) insides the patient's eyes with the aim of determining whether or not they are at risk for glaucoma
Types of tonometry
Goldmann and Perkins applanation tonometry. The Goldmann applanation tonometer measures the force necessary to flatten an area of the cornea of 3.06mm diameter.
Non-Contact Tonometry.
Ocular Response Analyzer.
Schiotz Tonometer.
Pneumotonometer.
Tono-Pen.
Examination of anterior segment of the eye
uses a slit-lamp microscope to light up the front part of the eye. This includes the eyelids, cornea, iris and lens. This test checks for cataracts or any scars or scratches on the cornea.
The sclera. The white part of the eye. The sclera is made up of tough, fibrous tissues and forms a protective outer layer of the eye. Inflammation and discoloration of the sclera can be detected during a slit lamp exam.
The cornea. The cornea is the clear, dome-shaped window of the front of your eye. Dry eye, a problem with the eyes’ tears and tear film, can be found looking through the slit lamp.
The lens. This is the clear part of the eye behind the pupil that focuses light on the retina so we can see. Cataract (when the eye's lens becomes cloudy) can be diagnosed during the exam.
The slit lamp also gives a detailed view of the back of the eye as well by using Volk lens and 3-mirror lens.
The retina. The retina is the layer of nerve cells lining the back wall inside the eye.
Optic nerve. A nerve at the back of the eye that connects to the brain. Glaucoma is a disease that slowly damages the optic nerve and causes vision loss if not diagnosed and treated early. A slit lamp exam is a key part of making the diagnosis
Visual Field:
Normal field of vision:
Upward 60֯ / inward 60 ֯
Downward 70 ֯
Outward more than 90֯
Techniques employed to evaluated both central and peripheral visual field is
Perimetry:
Kinatic perimetry b. Static perimetry.
1. Kinetic perimetry, which involves moving a stimulus of known luminance ( intensity of light) from the periphery towards the center to outline an isopter
2. Static perimetry, which present the patient with a fixed grid of points covering the important areas of the field.
GONIOSCOPY
It is the technique of examining the angle of the AC. Normally the angle is not seen on external examination. In this technique a contact lens (goniolens ) is placed on the cornea and the angle is examined with the slit lamp.
Ultrasonography
Ultrasonography a non- invasive diagnostic tool that allows examination of the ocular structures in the presence of media opacities such as opaque cornea, cataract or vitreous hemorrhage.


Examination of fundus oculi:
Ophthalmoscopy, also called funduscopy, is a test that allows to see inside the fundus of the eye
It is of two major types:
Direct ophthalmoscopy one that produces an upright, or un reversed, image of approximately 15 times magnification.
Indirect ophthalmoscopy one that produces an inverted, or reversed, image of 2 to 5 times magnification.
Features Direct ophthalmoscopy Indirect ophthalmoscopy
Condensing lens Not Required Required
Examination distance As close to patient's eye as possible At an arm's length
Image Virtual, erect Real, inverted
Illumination not useful in hazy media Bright; useful for hazy media
Area of field in focus About 2-8 disc diameters About 8 disc diameters
Stereopsis Absent Present
fundus view Slightly beyond equator Up to Ora serrata i.e. peripheral retina
Examination through hazy media Difficult to not possible Possible
Fundus photography
The fundus is the inside, back surface of the eye. It is made up of the retina, macula, optic disc, fovea and blood vessels. With fundus photography, a special fundus camera points through the pupil to the back of the eye and takes picture
Optical coherence tomography (OCT)
is a non-invasive imaging test. OCT uses light waves to take cross-section pictures of your retina. It is useful in studying the thickness of the retinal nerve fiber layer in glaucoma and in the study of macular diseases
They also provide treatment guidance for glaucoma and diseases of the retina. These retinal diseases include age-related macular degeneration (AMD) and diabetic eye disease.

ELECTROPHYSIOLOGIC TESTS

The electroretinogram (ERG)
ERG is an important tool in diagnosing and managing hereditary retinal disease as night blindness and retinal degeneration such as retinitis pigmentsa ( RP)
Electrooculogram (EOG)
EOG is an electrical recording based on the standing potential of the eye were the cornea is negative in relation to the retina. It records ionic and metabolic changes in the retinal pigment epithlium (RPE) as well as in the neuroretina
Visual evoked potential (VEP)
Light stimulation of the retina produces waves recorded over the occipital lobe. It is use in :
Measuring visual acuity in children
Diagnosis of optic neuritis.
Diagnosis of unilateral disease of the visual pathway