When to visit an ophthalmologist

Regular eye tests become more and more important as you get older. But it is sometimes confusing to realise that there are numerous different professions associated with eye health, and the names of each starts with an ‘o’! ophthalmologists, optometrists, opticians, and orthoptists!  Of course, general practitioners will also see patients for eye problems. So, who should you see?  Which one deals with what problems?  Who should do your eye examination?  As you will discover, an ophthalmologist is a medical doctor – an eye surgeon or specialist in eye problems and diseases.

Let’s start by defining each of these professions

Ophthalmologist

An ophthalmologist is a medical doctor who, after graduating from medical school, undertook additional specialist training in the diagnosis and management of eye disorders.  It typically takes 13-16 years for an ophthalmologist to complete all of the required training. Ophthalmologists provide eye treatment in the form of medications, laser surgery, and incisional surgery. The ophthalmologist will first perform a number of different eye tests, including for pressure in the eye and signs of cataract wear and tear.

Optometrists

Optometrists are not medical doctors but they are trained to examine eyes, screen for eye disease, give advice on visual problems, and prescribe and fit glasses and contact lenses. They also perform eye tests, but of a more superficial nature, using different instruments often.  If significant eye disease is detected, optometrists will refer patients to an ophthalmologist for further assessment and treatment. If you have eye surgery (performed by an ophthalmologist) your optometrist may also participate in your pre- and post-operative care, although this is not very common. Optometrists have studied optometry at university, which is typically 5 years of training.

Opticians

Opticians are optical dispensers, technicians trained to fit eyeglass frames. They use prescriptions supplied by ophthalmologists or optometrists, but do not test vision or write prescriptions for visual correction. Opticians are not permitted to diagnose or treat eye diseases.

Orthoptists

Orthoptists are trained to diagnose and manage disorders of eye movements. Orthoptists are also trained to perform eyetests to assess eye diseases. They typically work with ophthalmologists to support them in assessing patients.

General practitioners

Like ophthalmologists, general practitioners are also medical doctors but they have not done specialist training in eye disease. They may treat minor eye problems such as eyelid infections and conjunctivitis, but they will typically refer all other eye patients onto an ophthalmologist.

More information about ophthalmologists

As mentioned above, an ophthalmologist is a medical doctor, somebody who has completed six years of comprehensive medical training, combined with practical experience in a variety of health settings, including different hospital departments (paediatrics, psychiatry, oncology and so forth).

After this, they study the ophthalmology specialisation for five years (in Australia).  Many ‘subspecialise’, which means they complete an additional period of training working closely with an expert in a particular subfield of eye disease. This is because there is so much to know about the different forms of eye disease and that it is impossible for any single ophthalmologist to be a true expert in all areas. Most ophthalmologists in Australia will be comfortable treating most eye disorders but will have their unique subspecialty interests.

Many ophthalmologists are also involved in scientific research on eye diseases and vision disorders, searching for better ways to treat them.  This knowledge prepares an ophthalmologist take care of more complex or specific conditions of the eye.  It is this ultra-specialisation of ophthalmologists that you should keep in mind when you have been diagnosed with an eye condition.  It would make sense to see an ophthalmologist who has specific expertise in the area of your complaint if you wish to get the best possible care. Ideally, your ophthalmologist would be both an experienced expert in your disorder as well as actively involved in research in that area. They would also have advanced technology to perform eye tests necessary for their subspecialisation.

Visual acuity

The first eye test your ophthalmologist will do is to measure how well you can see in each eye, using an eye chart. You will notice that the chart only includes a small number of letters from the alphabet – these letter are specifically chosen because they are equally difficult to read. Vision can be tested with and without glasses, at both distance and near.

A ‘pinhole’ occluder is a mask with small holes (1.2mm diameter) punched in it. If your visual acuity dramatically improves when you peer through a pinhole then it means that your eye is defocussed (ie you need glasses).

Pupil Examination

The pupil is the round hole in the centre of the iris. Light passes through the pupil to reach the retina, which is the camera at the back of the eye. Your iris contracts and dilates according to the ambient lighting, which makes the pupil appear smaller and larger – the pupillary reflex.

This is tested by your ophthalmologist by shining a light into your eye.

Extraocular muscles

Six large muscles attach to the eyeball and work together to precisely control eye movement. Think of the muscles like the reigns on a horses head – as one contracts it’s partner relaxes, which turns the eyeball. They are called the ‘extraocular’ muscles because they are outside your eye, in contrast to your ‘intraocular muscles’ (which control pupil size and the zooming power of your lens). If one of the six muscles stops working correctly the eye will no longer point at what you are looking at, and you will have double vision as a result (diplopia). The extraocular muscles can be tested in many ways, the simplest is by having you follow a light.

Eyelid and conjunctival examination

The eyelids and conjunctiva are examined carefully with a microscope and good lighting.  The tear ducts are also examined, usually by touch, and any abnormalities such as inflammation, foreign bodies, and unusual swelling are noted.

Corneal examination

The cornea is the transparent window at the front of the eye that overlies the iris. Think of it like a ship’s hull – it is made of tough collagen (analogous to the steel of the hull) and is covered in a thin layer of epithelial cells (analogous to a coat of paint). Yellow dye is placed on your eyeball to highlight subtle defects in the corneal epithelial layer, such as can be caused by dry eye. The cornea is also checked for its transparency and curvature.

Ophthalmoscopy

Ophthalmoscopy refers to the examination of the back of the eye, which is done using specialised equipment.  It may be preceded by the addition of drops to dilate the pupil. Ophthalmoscopy allows your ophthalmologist to see your optic nerve and retina. The retina is like a thin layer of film that lines the inside of the eyeball that captures the image. The optic nerve is the cable that transmits this image to the brain. Important eye diseases are diagnosed with ophthalmoscopy include glaucoma, macular degeneration, retinal detachment, and diabetic eye disease.

Slit lamp examination

A slit lamp is a table-mounted instrument specifically designed for examining all parts of the eye. It comprises a microscope and an adjustable light source that illuminates the eye with a thin, bright beam of light. It gives the ophthalmologist a stereoscopic (3-dimensional) magnified view all eye structures, including the retina and optic nerve. The slit lamp is especially useful for the following:

• Identifying corneal foreign bodies and abrasions
• Detecting cells (red blood cells or white blood cells) floating in the fluid of the eye
• Detecting cataract
• Identifying diseases such as macular degeneration, diabetic eye disease, epiretinal membranes (a thin sheet of fibrous tissue on the retina), macular oedema and retinal holes.

Visual field test

Your visual field, or field of vision, is a measure of how far each eye can see in the periphery. The visual fields can be impaired by any disease of the neural visual pathway, from the retina to optic nerves to the visual centres of your brain.  Glaucoma is the most common disorder affecting the visual field. It is characterised by progressive damage of the optic nerve due to uncontrolled eye pressure, and this results in gradual loss peripheral vision.

Visual fields can be assessed grossly by direct confrontation testing. During this test, you will be asked to stare at the examiner’s eye or nose, while a small object, such as finger, is brought into the far periphery of your vision.  You will be asked to indicate when you first see the object.  Each eye is tested separately.

Visual fields can also be tested much more precisely using machines called perimeters. Your chin rests on a chin rest and you hold a button in your hand. Small dim lights are projected onto a screen in front of you and your job is to push the button every time you see one of these lights. For each point of your peripheral vision the machine records how bright the light needs to be for you to see it.

Colour vision testing

Colour vision is most commonly measured using a series of pictures that comprise a a pattern of coloured dots. Within each picture is a hidden number or symbol that is only visible to you if your eyes are able to distinguish a subtle difference in the colour of the dots. Congenital colour blindness refers to a disorder of colour vision present at birth. People with congenital colour blindness are usually male and struggle to distinguish red from green. In contrast, colour blindness that develops later in life due to disease of the eye usually impairs the ability to distinguish blue from yellow.

Tonometry

Tonometry is a test to measure the pressure inside the eye (the intraocular pressure, or IOP). The eye is inflated by a watery fluid, and the pressure of this fluid ensures that the eye maintains its specific shape. However, if the eye pressure becomes elevated then this causes damage to the optic nerve (a disease that we call glaucoma).

There are two main ways in which intraocular pressure can be measured. One way is to measure the force required to flatten the front window of the eye (the cornea). The surface of the eye is anaesthetized and the tonometer lightly presses against the cornea. If an eye has high eye pressure, more force will be required to deform the cornea.

The second common way of measuring eye pressure is with an ‘air puff’. This is a fast-moving jet of air that strikes the cornea. The instrument measures how the cornea deforms in response to this jet of air. From this information the intraocular pressure can be calculated. Note tonometry is not the only way in which glaucoma is identified: examination of the optic nerve is also required.

Angiography

This is also sometimes called ‘fluorescein angiography’. In this procedure, a fluorescent orange dye is injected into your vein. Within a matter of seconds this dye travels through your blood vessels and reaches the eye. Photographs are then taken of the retina as the dye passes through the blood vessels. With each flash of the camera the dye ‘fluoresces’ bright green. This green light is captured by the camera. The result is a spectacular image of the shape and branching pattern of the retinal blood vessels. The angiogram also reveals if any blood vessels are blocked, or if any are leaking, as can occur in diabetic retinopathy and wet macular degeneration.

Optical coherence tomography (OCT)

Optical coherence tomography (OCT) provides high-resolution images of the back of the eye (retina, retinal pigment epithelium, choroid and posterior vitreous).  It works similarly to ultrasonography but uses light instead of sound.  It is useful to help diagnose age-related macular degeneration, diabetic retinopathy, macular holes and epiretinal membranes and the progression of glaucoma.

Ultrasonography

Similar to an ultrasound to determine the growth of a foetus, this procedure provides two dimensional structural information and is used to assess retinal tumours, detachments, vitreous haemorrhages, location of foreign bodies, detection of posterior scleral oedema characteristic of posterior scleritis; and distinction of choroidal melanoma from metastatic carcinoma and subretinal haemorrhage.

One version of this can determine the axial length of the eye which is used to calculate the power of an intraocular lens which is needed for cataract surgery.

Ultrasonic pachymetry involves measurement the thickness of the cornea before refractive surgery, such as ‘laser in situ keratomileusis’, known as LASIK.

Electroretinography

Electrodes are placed on each cornea and on the surrounding skin, and electrical activity in the retina is recorded. ERG is used to diagnose subtle electrical disorders of the retina.

CT and MRI

These imaging techniques are commonly used when the eye has suffered physical injury, such as foreign bodies.  They are also useful to evaluate orbital tumours, optic neuritis and optic nerve tumours.

HealthDirect.  2018.  What does an ophthalmologist do?  https://www.healthdirect.gov.au/what-does-an-ophthalmologist-do

Heitling, Gary. 2018.  How to choose an eye doctor.  https://www.allaboutvision.com/eye-doctor/choose.htm

Khazaeni, Leila M.  2019.  Evaluation of the ophthalmologic patient.  https://www.merckmanuals.com/professional/eye-disorders/approach-to-the-ophthalmologic-patient/evaluation-of-the-ophthalmologic-patient

Medical Eye Center.  2017.  What is the difference between optometry and ophthalmology?  

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