Glossary of Terms

  1. Anterior Eye Imaging
  2. Automated Keratometr
  3. Binocular Function and Ocular Balance Assessment
  4. Colour Vision Assessment
  5. Contact Lens Assessment
  6. Contact Tonometry
  7. Crystalline Lens Imaging
  8. Gonioscopy
  9. History And Symptoms
  10. Internal and External Ocular Health
  11. Macular Disease Predictive Testing
  12. Macular Pigment Density Assessment
  13. Non-contact Tonometry
  14. Optical Coherence Tomography
  15. Orthoptic And Eye Dominance Assessment
  16. Pachymetry
  17. Reading Speed Assessment
  18. Retinal Imaging
  19. Supra Threshold Visual Field Testing
  20. Tear Film Analysis and Dry Eye Treatment Advice
  21. Threshold Field Visual Field Testing
  22. Retinoscopy
  23. Auto-Refractor
  24. Refraction

1. Anterior Eye Imaging

Anterior eye imaging involves the use of a special camera built into the optometrists’ slit-lamp microscope allowing detailed, high resolution videos and photographs of the front of the eye (eyelids, eye lashes, cornea etc.) to be collected. This is useful in monitoring conditions such as blepharitis, styes, dry eye and conjunctivitis, and is particularly useful in monitoring more serious eyelid and corneal disorders.

Anterior eye imaging is a quick and painless procedure. It involves the optometrist inspecting the eye with a microscope which produces a beam of bright light. The process of image capturing involves no flash, unlike conventional cameras.


2. Automated Keratometry

Keratometry involves measuring the anterior curvature of the cornea using a keratometer (sometimes known as an ophthalmometer). This can be done manually by the optometrist or using a computerised, automated keratometer. At Peter Ivins Eye Care we use the latest automated keratometer, which will not only measure the corneal curvature but is also an auto-refractor allowing for quick and accurate estimation of refractive error (spectacleprescription).

Keratometry is used primarily for contact lens fitting. The optometrist measures the curves of the cornea to ensure the correct size and shape of contact lenses is selected for fitting. This is particularly important in rigid gas permeable lenses and complex soft lenses fitting. It can also be useful in monitoring diseases of the cornea such as keratoconus.

Automated Keratometry is a quick a painless procedure which requires the patient to look at a picture of a road with a hot air balloon in the distance whilst the machine takes accurate measurements. This process takes a matter of seconds to perform and does not affect vision, meaning driving afterwards is safe.


3. Binocular Function and Ocular Balance Assessment

Binocular function and ocular balance assessment involves a variety of tests conducted by the optometrist to investigate how well the eyes work together. Balanced, co-ordinated eyes are crucial for comfortable and sharp binocular vision. During this group of tests the optometrist will be looking for abnormalities such as strabismus (commonly known as a squint or turn in the eye), accommodation and convergence issues (focussing problems), eye muscle problems which may cause diplopia (double vision), all which may affect quality of vision. The optometrist may also investigate stereopsis (ability to see in 3D), using a variety of 3D tests.

Adjustments to spectacle prescription power may be made to improve co-ordination and balance between the eyes. Prism may also be added to spectacle lenses to help alleviate muscle imbalances which can cause double vision. Eye exercises are occasionally prescribed in attempt to alleviate muscle imbalances. Significant problems with binocular function and oculo-motor balance may be referred to an orthoptist (a specialist in eye muscles and their effect on vision).


4. Colour Vision Assessment

Colour vision assessment involves the use of various tests conducted by the optometrist to investigate the eyes ability to perceive and differentiate colours. The most common test used is the Ishihara Colour Test. This test involves viewing patterns of coloured dots which form numbers visible to individuals with normal colour vision, but are difficult or impossible for people with colour vision defects to identify.

Colour vision defects can be inherited genetically or acquired at any stage of life as a result of problems in the visual system. Inherited colour vision defects are carried by mothers and passed on to their sons. Inherited red/green colour defects are the most common colour vision problem and are found in around 8% of the male population (1 in every 12 males). Around 1 in 200 women are mildly affected by colour vision defects. Blue/yellow defects are very rarely inherited and are much more commonly acquired as a result of eye diseases such as glaucoma, cataracts and optic nerve disease.


5. Contact Lens Assessment

Initial assessment

During the initial contact lens assessment the optometrist will discuss in detail exactly what is required from a contact lens; when they will be worn, the intended duration of wear, previous experience with contact lenses, past and present general health, past and present ocular health etc. The eye will then be examined meticulously using the slit lamp microscope; anterior eye imaging may be utilized to document baseline eye appearance and abnormalities using photographs or videos before contact lens wear.

The optometrist will inspect, grade and record the health of the eyelids, eyelashes, conjunctiva, episclera, sclera and cornea etc. Various dyes may be instilled in the eye including fluorescein and lissamine green (this process is completely painless and does not affect vision, so driving afterwards is safe) allowing a better view of the front of the eye. The volume and quality of the tear film will be assessed and graded using a variety of techniques to ensure conditions such as dry eye will not cause discomfort whilst wearing contact lenses. The curvature of the cornea will be measured using automated keratometry; this will enable the correct size and shape of contact lens to be selected, which is particularly important in rigid gas permeable lens or complex soft lens fitting.

The optometrist will discuss the results from the aforementioned examinations and make a recommendation based on the clinical information gathered and your individuals’ needs on which type of lens is most appropriate. Diagnostic lenses (trial lenses) will then be selected (such lenses may need to be ordered in complex cases) and placed on the eye by the optometrist. After a brief adaptation period (a few minutes) vision is checked wearing the lenses and adjustment made to the prescription if required. The fit of the contact lens is assessed using the slit lamp microscope.

Contact Lens Handling Session

If the lenses are deemed successful a contact lens handling lesson will be arranged (this is usually conducted on the same day or occasionally this may need to be re-booked as a separate appointment), where an experienced member of the clinical staff will offer a detailed guide through the following:

  • Lens application and removal technique
  • Wearing instructions suitable for the lens selected
  • Contact lens care and cleaning regime
  • Use of contact lens solutions and hygiene advice
  • Contact lens 'do's and don'ts'

Once the contact lens handling session has been completed trial lenses and any required cleaning/storing/rinsing solutions will be issued, allowing you to try contact lenses within your own environment e.g. at home, in work etc.

Follow-up appointment

After a trial period (which may vary from a few days to a few weeks depending on the type of contact lens prescribed) a follow-up appointment (contact lens check-up) will be arranged. Contact lenses should be worn to this appointment, having ideally been in the eye for a few hours before the appointment. The optometrist will review how successful the lenses have been in terms of ease of use, clarity of vision and comfort. Vision will be checked and any necessary adjustments to the prescription made. The fit of the contact lenses will be checked using the slit lamp microscope and adjustments may be made to the shape, size and overall fit of the contact lens if required. The lenses will then be made and a meticulous inspection of the health of the front of the eye will be conducted to look for any changes caused by use of contact lenses.

At the end of this consultation the optometrist will discuss and make a recommendation based on the clinical results from the various consultations and feedback from you on how best to continue with contact lenses, e.g. part-time wear, full-time wear, extended wear etc.


6. Contact Tonometry

Tonometry is the measurement of tension or pressure within the eye. It is advisable for adults, particularly individuals over 40 to have their intraocular pressure (IOP) measured routinely as elevated IOP’s can lead to optic nerve damage. The optic nerve is a crucial part of the visual system; it collects all the visual information gathered by the photoreceptors of the retina and transmits this information to the brain where the signals are interpreted as vision. Optic nerve damage can lead to decreased peripheral vision (tunnel vision) and loss of nerve tissues. Elevated IOP’s can commonly occur without symptoms, meaning like many other eye conditions the individual may be unaware there is a problem. Elevated IOP’s is associated with glaucoma; as a result tonometry is important in diagnosing and monitoring glaucoma.

Applanation tonometry involves the use of an eye drop containing a local anesthetic and a yellow dye called fluorescein which the optometrist will instill prior to measuring IOP’s. A Goldmann tonometer (gold standard for IOP measurement) is then attached to the optometrists slit lamp microscope and using a special cobalt blue light the optometrist is able to accurately measure IOP’s in millimeters of mercury (mmHG). In normal individuals the pressure is commonly between 10-21mmHg. In individuals with elevated IOP’s the measurements will be repeated on a separate day at a different time of day to account for fluctuations in IOP. The procedure is completely painless, takes only a few seconds to perform and shouldn’t affect your vision meaning driving afterwards is safe.


7. Crystalline Lens Imaging

Crystalline lens imaging involves the use of a special camera built into the optometrists’ slit-lamp microscope allowing detailed, high resolution videos and photographs of the crystalline lens (the lens inside the eye) to be collected. This is useful in monitoring and diagnosing cataracts. Crystalline lens imaging is a quick and painless procedure. It involves the optometrist inspecting your eye with a microscope which produces a beam of bright light. The process of image taking involves no flash unlike conventional cameras.

Cataract is an extremely common condition, affecting most commonly the over 60 population as result of the normal ageing process of the eye. Cataracts can be congenital (from birth) or acquired as a result of trauma to the eye (traumatic cataract), systemic health issues such as diabetes or associated with long-term use of specific drugs such as steroids (secondary cataract). There are many forms of cataracts, but they all involve changes to normally transparent crystalline lens, varying in degree from slight clouding of the lens to complete opacity. As cataracts become more opaque visual symptoms such as reduced clarity of vision, reduced contrast sensitivity, decreased colour sensitivity and increased glare become more prominent. Most cataracts progress slowly over a number of years and affect both eyes; potentially at different rates. Modern surgical techniques mean cataracts can be very effectively treated in the vast majority of individuals as a day case under a local anesthetic.


8. Gonioscopy

Gonioscopy is a procedure during which the optometrist uses a special lens (goniolens) in conjunction with the slit lamp microscope to visualize the iridocorneal angle (anatomical angle formed between the iris and the cornea within the eye). Viewing the anatomic structure of this region of the eye is particularly important in diagnosing and monitoring eye conditions which may lead to or be associated with glaucoma. The procedure is quick and painless and involves the use of a topical anaesthetic via an eye drop. The goniolens is then placed gently onto the anaesthetised eye and the optometrist uses the slit lamp microscope to view the anterior chamber angle, looking for any abnormalities. This process can be videoed or photographed using anterior imaging to document the results.


9. History And Symptoms

During history and symptoms the optometrist will listen to any general health issues, eye health problems and any problems or questions related to vision, spectacles or contact lenses you may have. Our optometrists will ask you a series of questions relating to past and present general health, past and present eye health, family history of conditions such as glaucoma or macular degeneration etc. Current symptoms such as headaches, gritty eyes etc will be explored. During this process our optometrists is able to learn about your lifestyle, general health, ocular health and visual requirements.

Studies have indicated that over 80% of diagnoses in medical clinics are based on the medical history. The information gathered during history and symptoms will enable our optometrists to tailor the eye examination to your needs, make a more accurate diagnosis and recommend additional examinations such as optical coherence tomography, retinal photography, macular pigment analysis etc, if required.


10. Internal and External Ocular Health

External ocular health is checked and monitored using a slit lamp microscope. The slit lamp is an illuminated microscope which allows a detailed, binocular and magnified view of the outer surface of your eye. The optometrist will inspect the eyelids, eyelashes, conjunctiva, episclera, sclera (white of the eye), cornea, anterior chamber, iris and crystalline lens looking for abnormalities or disease. If problems are detected they can be documented using anterior eye imaging, allowing detailed photographs or videos to be stored.

Internal ocular health can be checked using a hand held microscope known as a direct ophthalmoscope. More commonly a technique known as indirect ophthalmoscopy is used which involves the use of the slit lamp microscope in conjunction with a condensing lens held in the hand of the optometrist and placed a few millimetres from your eye. This allows very detailed, binocular and magnified views of the back of the eye. The optometrist will inspect the optic nerve, macula, blood vessels etc looking for problems such as glaucoma and macular degeneration.

Both procedures are relatively quick and completely painless. Internal ocular health checks may involve the use of an eye drop known as a mydriatic which is used to dilate your pupils. Dilated pupils offer a clearer, wider view of the back of the eye which may be necessary if you have small pupils or conditions such as diabetes meaning a detailed view of the eye is advisable.


11. Macular Disease Predictive Testing

Macular disease predictive testing involves the use of the Sight Risk AMD Calculator in conjunction with macular pigment density measurements obtained using the Zeiss Visucam 200 and expert advice based on the results of such tests. The Sightrisk AMD Calculator calculates your predicted risk of developing macular degeneration based on your known risk factors for the condition. The system immediately generates a predicted percentage risk from age 55 to 100 as a graph as well as a list of recommendations on how to reduce this risk. Using this percentage as a guide the optometrist will be able to recommend appropriate actions that may reduce your risk of developing macular degeneration later in life.


12. Macular Pigment Density Assessment

Macular pigment density assessment involves the use of the Zeiss Visucam 200, a technique which enables the optometrist to measure the amount of Macular Pigment within the retina. This technique takes a few seconds and is exactly the same process as having a retinal photograph taken. It will not affect vision, so driving afterwards is safe.

Macular pigment is comprised of carotenoids known as Lutein and Zeaxanthin which are absorbed by the body from our diet; specifically from green leafy vegetables such as spinach, kale, broccoli and yellow foods such as sweet corn, peppers and egg yolk. A third macular pigment has been identified which is known as Meso-Zeaxanthin which is formed by the body from Lutein. The carotenoids are stored within the retina acting as a protective shield to the delicate macular tissues and protect the eye from conditions such macular degeneration.

Individuals with low levels of macular pigment are more at risk of macular degeneration; individuals with high levels of macular pigment are less at risk. Macular pigment can now be accurately and quickly measured, meaning we are able screen our patients for low macular pigment levels. Crucially, macular pigment levels can be improved by changes to diet and lifestyle; introducing more macular pigment rich foods or via the introduction of macular supplements containing high levels of vitamins, minerals and macular pigments.


13. Non-contact Tonometry

Non-contact tonometry, more commonly known to patients as the ‘puff of air test’ allows the optometrist to quickly measure IOP’s in millimeters of mercury (mmHG). The non-contact tonometer works on the principle of a time interval; measuring the time it takes from the initial generation of the puff of air, to were the cornea is flatten by the air, to the point where the timing device stops as the cornea returns to its normal shape. It takes less time for the puff of air to flatten an eye with low IOP’s than it does in eye with high pressures.

In normal individuals the pressure is commonly between 10-21mmHg. In individuals with elevated IOP’s the measurements will be repeated on a separate day at a different time of day to account for fluctuations in IOP at different times of day. The procedure is completely painless, takes only a few seconds to perform and will not affect vision meaning driving afterwards is safe.


14. Optical Coherence Tomography

Optical Coherence Tomography (or OCT), is a highly sophisticated echo technique similar in principle to an ultrasound or MRI scan; it however utilises reflections of light instead of sound or radio waves. OCT produces highly detailed, three-dimensional, cross sectional views of structures within the eye. It provides tissue morphology imagery with a resolution of 1µm, meaning the optometrist is able to view individual layers of the eyes anatomy fractions of a millimeter in size. This is hugely beneficial in screening, diagnosing and monitoring various eye conditions such as macular degeneration and glaucoma.


15. Orthoptic And Eye Dominance Assessment

During this group of tests the optometrist will be looking for abnormalities such as strabismus (commonly known as a squint or turn in the eye), accommodation and convergence issues (focussing problems), eye muscle problems which may cause diplopia (double vision), all which may affect quality of vision. The optometrist may also investigate stereopsis (ability to see in 3D), using a variety of 3D tests. Adjustments to spectacle prescription power may be made to improve co-ordination and balance between the eyes.Prism may also be added to spectacle lenses to help alleviate muscle imbalances which can cause double vision. Eye exercises are occasionally prescribed in attempt to alleviate muscle imbalances. Significant problems with binocular function and oculo-motor balance may be referred to an orthoptist (a specialist in eye muscles and their effect on vision).


16. Pachymetry

Pachymetry is a technique that allows the optometrist to accurately measure the thickness of the cornea. At Peter Ivins Eye Care we do so using the latest 3D HD-OCT from Carl Zeiss, allowing very accurate corneal thickness measurements in a quick, painless and non-contact manner (previous methods involved touching the eye). It does not involve eye drops and does not affect vision, meaning driving afterwards is safe.

Corneal pachymetry is important in the early detection and diagnosis of glaucoma and ocular hypertension. It is also potentially important in monitoring corneal disease, diagnosing corneal foreign bodies, and in patients considering LASIK eye surgery as it ensures sufficient corneal thickness prior to surgery to prevent ectasia (abnormal bulging of the cornea).


17. Reading Speed Assessment

The Wilkins Rate of Reading Test involves reading text that looks like a passage of prose, but consists of random words. It is designed to measure the effects on reading of visuo-perceptual distortions of text, such as apparent movement of words and letters, blurring or text and coloured haloes; symptoms commonly reported in patients with visual dyslexia, Mears-Irlen Syndrome or other types of visual stress.

The test is not a conventional reading test in which the words become progressively more difficult. Such tests usually compare an individual’s performance with that of other individuals of a similar age and therefore express the performance in terms of a ‘reading age’. Using the Wilkins Rate of Reading test allows reading ability to be assessed in terms of rate and errors rather than the difficulty of the words to read. The words used are very high frequency in the English language and should be familiar and within the reading vocabulary of children aged 7 and above.

The individual is required to read the text aloud as rapidly as possible. The optometrist times this process and notes any errors. This process allows a comparison of an individual’s reading performance under different visual circumstances, for example with and without coloured overlays, or with and without specially tinted spectacle lenses.


18. Retinal Imaging

Retinal imaging (also known as fundus photography) is a sophisticated process allowing detailed, high resolution images of the back of the eye to be captured and permanently stored using the very latest digital imaging technologies from Carl Zeiss. Retinal photography is used to document retinal health at a particular point in time in a quick, objective and highly detailed manner. This enables accurate comparisons of eye health over time and meticulous monitoring of various eye conditions such as glaucoma, age-related macular degeneration and diabetic retinopathy.


19. Supra Threshold Visual Field Testing

Visual field testing (also known as perimetry) is used to evaluate peripheral vision or field of view. Visual field testing is particularly important in screening, diagnosing and monitoring retinal conditions such retinal detachments; optic nerve conditions such as glaucoma and optic neuritis; and brain disorders such as strokes and tumours. It is also commonly requested by the DVLA in individuals with the aforementioned conditions, whereby loss of peripheral vision may impair ability to drive safely. In such cases a special binocular visual field assessment known as an Estermann test is conducted.

Visual field testing involves looking at a small orange target within a white bowl. You are asked to maintain a constant and steady gaze on this target. The machine then presents a small white dot of light at random intervals and locations around the bowl and you are asked to press a button in response to having seen the light.

In supra threshold visual field testing the brightness of the white light presented is adjusted by age and is of an intensity which should be easily visible. This test is used to screen for scotomas (holes in the visual field) caused by conditions such as glaucoma and strokes. Visual field analysis is conducted on every patient as part of the routine NHS eye examination. It is a quick, straightforward and painless procedure and normally takes a few minutes per eye. It does not affect vision meaning driving afterwards is safe.


20. Tear Film Analysis and Dry Eye Treatment Advice

During tear film analysis the optometrist uses a variety of techniques to investigate the volume and quality of the tear film and the health of the front of the eye. This will enable the optometrist to diagnose the cause of the dry eye, the type of dry eye and therefore advise you on the best treatment. This process will potentially involve the use of diagnostic stains and dyes such as fluorescein and lissamine green to enable a more detailed inspection of the anterior eye. The optometrist will use the slit lamp microscope in conjunction with anterior eye imaging to meticulously inspect, photograph and document the health and function of the eyelids, eye lashes, sclera, episclera, palpebral conjunctiva, bulbar conjunctiva, cornea, tear ducts and tear glands, as abnormalities to these areas can contribute to dry eye syndrome. This process does not affect vision, therefore driving afterwards is safe.


21. Threshold Field Visual Field Testing

A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, brain tumours or other neurological deficits.

The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine. Machine based tests aid diagnostics by allowing a detailed printout of the patient's visual field.

Other names for this test may include Perimetry, Tangent screen exam, Automated perimetry exam, Goldmann visual field exam, or Humphrey field exam.


22. Retinoscopy

The optometrists assess whether or not visual correction in the form of spectacles or contact lenses is required. The first part of this process is the use of a retinoscope, a handheld device used by the optometrist allowing an accurate approximation of the level of myopia (short sightedness), hyperopia (long sightedness and astigmatism (rugby ball shaped cornea) and therefore an approximation of the required spectacle prescription. This process takes only a few seconds to perform, and involves the optometrist shining a light into the eye.


23. Auto-Refractor

An auto-refractor or automated refractor is a computer controlled device used for a quick and accurate estimation of refractive error (spectacle prescription). This is achieved by measuring how light is changed as it enters the eye and requires no input or feedback from the patient.

Automated refraction is a quick a painless procedure which requires the patient to look at a picture of a road with a hot air balloon in the distance whilst the machine takes accurate measurements. This process takes a matter of seconds to perform and does not affect vision, meaning driving afterwards is safe.


24. Refraction

Automated refraction is a quick a painless procedure which requires the patient to look at a picture of a road with a hot air balloon in the distance whilst the machine takes accurate measurements. This process takes a matter of seconds to perform and does not affect vision, meaning driving afterwards is safe.

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