The Eye Examination
Common Eye Conditions
EYE-CARE FOR ALL
Many of us think to have our teeth checked and those of our children, yet we forget to have regular checks on our eyesight and the health of our eyes.
There is far more to an eye examination than simply checking whether spectacles are needed. The eye can be an indicator of general health issues. For example, diabetes, high blood pressure and many other health problems can be detected in an eye examination.
For children, optometrists recommend a routine examination every 12 months unless otherwise advised. During adulthood the normal interval is 2 years but once over the age of 60 or with certain medical conditions or family eye problems,there may be a need for more frequent examinations. Your optometrist will advise you.
THE EYE EXAMINATION
During an eye examination you can expect to have some or all of the following procedures carried out. The actual procedures carried out for each individual person will be determined by your Optometrist, taking into account your age, any symptoms you may be experiencing, your occupation, hobbies and any special visual requirements, also any medical or family history that could be relevant.
History and Symptoms
This is a very important part of the eye examination.
Your optometrist will need to find out why you have come for an eye examination.
Are you experiencing any symptoms or having any problems with your vision?
What are your visual requirements? ie occupation, hobbies, do you drive?
Have you had any problems in the past (ocular history)?
Are there any ocular problems in the family which may be hereditary?
Do you have any medical problems which could affect the eyes?
Vision and Visual Acuity
When you view the sight test chart the lowest line of letters you can read is noted.
VISION is the lowest line read without spectacles
VISUAL ACUITY is the lowest line read with spectacles or correcting lenses
The line read is recorded as a fraction eg 6/12, 6/9, 6/6 this is known as Snellen acuity
The largest letter on the Snellen Chart is usually 6/60
The smallest letters are usually 6/5
The top number, usually 6, means the distance at which the test was carried out ie 6 metres. The bottom number is the smallest size of letters that you were able to see.
NORMAL VISION is 6/6 and is usually the next to bottom line (or on some charts two lines up from the bottom). In the USA, normal vision is termed 20/20.
This determines whether the eyes coordinate and work together properly as a pair, e.g to see if there is a squint present. This may be assessed with you looking into the distance and also looking close-up
This checks whether each eye is able to look in every different direction. It is used to detect a defect in one or more of the eye muscles
This examines the reactions of the pupils to light
If the pupils do not react to light correctly it could indicate neurological problems
The external eye can be examined with a light, or in more detail with the magnification of the SLIT LAMP.
The eyelids, conjunctiva, cornea, iris (ie coloured surround to the pupil) and lens are examined
The internal eye is usually examined with the OPHTHALMOSCOPE. Sometimes drops are used to enlarge the pupils and enable a better view of the back of the with a VOLK LENS, which is always used in conjunction with a slit lamp.
By examining the various parts of the eye an overall picture can be obtained of the condition of the eyes and also your general health in some cases.
Digital Fundus Photography
Digital fundus photography is nowadays available at most high street opticians practices. A digital camera takes photographs of the back of the eye and accompanying software allows for further enhancements to the photos. Digital fundus photography can be used to keep a precise record of the health of the eye for future reference. If a deterioration in eye health is suspected, new photos can be taken and compared with the old, so allowing detection of subtle changes.
This determines whether you are long-sighted, short-sighted, astigmatic, presbyopic, or have no optical error at all (emmetropic)
If you have a refractive error then a prescription for lenses needed to correct this will be determined by the optometrist.
This is where the Optometrist observes the results of the test to determine roughly what lenses are required for you. It gives a starting point before asking you questions but can also be used to determine a prescription in patients who are unable to read the chart eg very young children, or people with communication or learning difficulties
Either a RETINOSCOPE or an AUTOREFRACTOR could be used
These are used after the objective tests have provided a starting point. The optometrist asks the patient to choose between various lenses as to which gives the clearer vision.
Intraocular Pressure (IOP)
This measures the pressure of the fluid within the eye using a TONOMETER.
This can indicate the possible presence of GLAUCOMA.
A NON-CONTACT tonometer is often used which blows a puff of air at the eye. Four readings are normally taken before calculating an average measurement.
Alternatively a GOLDMANN or PERKINS tonometer is used which actually touches the eye and so requires the use of an anaesthetic drop first. This is sometimes referred to as the 'blue light' test because the instrument shines a blue light. The contact tonometry methods used by community optometrists give very accurate estimates of pressure and are the same as those used in hospital eye departments.
Visual Field Screening
This can indicate neurological problems and also detect the presence of GLAUCOMA. The patient's 'all round' vision is assessed and the optometrist is looking for any areas where the patient cannot see or where the eye is not as sensitive as it should be. These areas are called FIELD DEFECTS.
Colour Vision Test
This can determine if you have problems with colour vision. Colour 'blindness' is normally a hereditary condition where certain shades of colours are more difficult, or impossible, to tell apart. It is almost invariably only found in men.
Rarely colour vision problems can be acquired later in life as a side effect of certain illnesses, eye disease or medication. These types of colour vision problems can affect both men and women.
Certain careers can be difficult or impossible if you have a problem with your colour vision.
This test is used to check and measure how well a person can judge distances. It also gives a good indication of how well the two eyes to work together. The test is used mainly in children and is valuable in the assessment of squints and amblyopia (so-called "lazy eye"). Both eyes must work well independently and in addition work well together to allow good depth perception.
COMMON EYE CONDITIONS
What is amblyopia?
Amblyopia (lazy eye) is defined as “reduction of vision in one or both eyes that cannot be improved by spectacles alone”. It usually occurs before the age of eight. Infants born prematurely, or with low birth weight, are at a greater risk for the development of this condition. It is estimated that two to four percent of children have amblyopia. Amblyopia is usually due to conditions such as crossed eyes (strabismus) or a large difference in the refractive error between the two eyes. Vision in the amblyopic eye may continue to decrease if left untreated. The brain simply pays less and less attention to the images sent by the amblyopic eye. Eventually, the condition stabilizes and the eye becomes virtually unused. It is quite difficult to effectively treat amblyopia at this point. A comprehensive optometric examination can determine the presence of amblyopia. The earlier it is diagnosed the greater the chance for a successful treatment. In young children, patching the good eye may help the amblyopic eye to improve. In addition, to help improve vision function, vision therapy techniques may be used. Eyeglasses or contact lenses may be prescribed to correct any refractive errors. Early detection and treatment of amblyopia and correcting refractive errors is the key to ocular health. In most cases your optician will arrange a referral to an orthoptist who specialises in the detection and management of amblyopia and strabismus (squint).
What is Strabismus (squint)?
A squint occurs when the eyes are not lining up properly and do not work as a pair. One eye may turn inwards, outwards or even up or down. When this happens in young children, the brain often learns to ignore the picture from the squinting eye to prevent the child seeing “double vision”. This can cause amblyopia (lazy eye) as the vision in that eye fails to develop properly. Squints may occur in children for a number of reasons, e.g. a need for glasses or a family history of squints. Treatments vary and may include spectacles, or sometimes an operation to correct the squint. The orthoptist is specially trained to decide the best treatment for the squint.
If a squint develops in an adult or older child their brain is unable to ignore the picture from the squinting eye and this causes “double vision”. Reasons for the onset of squint in an adult are many, but possible causes include diabetes, thyroid disease and injury (trauma). Double vision can often be corrected with prisms. The orthoptist can advise the best course of action depending on the symptoms and cause of the squint.
What is Glaucoma?
Glaucoma is a degenerative disease of the optic nerve in which damage occurs to the optic nerve. One cause of this is when the fluid pressure in the eyeball is too high. This damage can cause severe vision loss and even blindness, if untreated. Glaucoma can generally be effectively controlled with prescription eye drops or other medicines which reduce the pressure in the eye. In some cases, surgery or laser treatment may be needed. All optometrists are trained to diagnose this condition. Is it considered normal to test for it routinely in the over 40s but also in younger persons sometimes.
What are Cataracts?
If the normally clear lens in your eye becomes cloudy, it is called a cataract. As the lens becomes cloudy, vision becomes blurred and/or distorted. Spectacles or contact lenses can be prescribed to provide clearer vision until cataracts develop to the point that they impair vision. Then they need to be removed surgically. Nowadays this is most commonly done using a technique called phaco-emulsification and takes about 20 minutes. An intra-ocular lens (an implant) is usually used to replace the lens removed from your eye.
What are flashes and floaters?
Floaters are small, semi-transparent or cloudy specks or particles within the fluid inside the eye that become noticeable when they move within the line of sight. They may also appear with flashes of light. The inner part of your eye is filled with a clear, jelly-like fluid known as the vitreous. Occasionally, small flecks of protein and other matter become trapped during the formation of the eye before birth and remain in the vitreous body. Floaters may also be caused by the age related deterioration of the eye fluid or its surrounding parts or by certain injuries or diseases. Almost everyone sees a few floaters at one time or another. They can occur more frequently and become more noticeable as you grow older. If you notice a sudden change in the number or size of the floaters, you should contact your optometrist right away for an examination to be sure they are not the result of a more serious problem.
What is “Dry Eye”?
The tears your eyes normally produce are necessary for overall eye health and clear vision. Dry eye occurs when your eyes do not produce enough tears or produce tears which do not have the proper chemical composition. Dry eye symptoms can result from the normal ageing process, exposure to environmental conditions, problems with normal blinking, or from medications such as antihistamines, oral contraceptives or antidepressants. Dry eye can also be symptomatic of general health problems, or other diseases. If dry eye is untreated it can harm your vision. Common treatments include the use of lubricating eye drops but there are other ways to help which may be more useful in particular cases.
Effects of diabetes on the eye
Diabetes and its complications can affect many parts of the eye. Diabetes can cause changes resulting in short-sight, long-sight, and premature presbyopia (the inability to focus on close objects). It can result in cataracts, glaucoma, a breakdown of eye muscle co-ordination (strabismus) and in decreased corneal sensitivity.
Visual symptoms of diabetes include fluctuating or blurred vision, occasional double vision, loss of visual field and flashes and floaters within the eyes. Sometimes these early signs of diabetes are first detected in a routine eye examination. The most serious eye problem associated with diabetes is diabetic retinopathy. This occurs when there is a weakening or swelling of the tiny blood vessels in the retina of your eye, resulting in blood leakage, the growth of new blood vessels and other changes. Early detection is critical because if untreated, blindness can result.
During your visit to your optometrist, we can diagnose potential vision threatening changes in your eye that can be treated to prevent blindness. It is important to monitor and control your diabetes as much as possible to minimise your risk of developing retinopathy. Several factors that increase the risk of developing retinopathy include smoking, high blood pressure, drinking alcohol and pregnancy.
Diabetic Retinopathy Screening
All diabetics should have their eyes examined at least annually. In Staffordshire there is a central register of diabetic patients held by the Health Authority. This register is used to write to diabetics to remind them when they are due for an eye screening appointment.
Diabetic Retinopathy Screening is carried out by accredited optometrists within Staffordshire and will involve drops being put in your eyes to make the pupils bigger and photographs being taken to record the health of your eyes. These photographs are stored centrally within the county to allow for audit checks to confirm the accuracy of the screening process.
Because not all optometrists are accredited, you may be asked to attend a different optometrist to the one you normally use for your eye examinations. This is OK because all that is happening is your Diabetic Retinopathy Screening and you can still go to your normal Optometrist when your eye examination is due.