Visual Jargon

This information will help you to put complex visual jargon and measurements into more manageable terms.

A regular eye examination is very important, however getting bogged down with technical terms can make understanding your child’s visual abilities some what difficult. Below are examples of some terminology you may have come across.  

If your child is attending the eye department at the hospital they will encounter different health care professionals at different times.  All departments work together so that your child receives the best care possible.

Vision & Learning

Having a regular eye test and an updated pair of well fitting glasses allows the child to use what vision they have to the best of their ability (See ‘Well fitting frame’).

Vision plays an important part in our lives.  This is especially true when it comes to learning.  If a child has a visual impairment this can hinder the learning process, as teaching and learning is mainly based on visual tasks.  Small steps can help make visual dependant learning easier. Optometrists, healthcare professionals, parents, and teachers must make learning as enjoyable and as easy as possible.  

Any excess effort to see will cause the child to tire more easily and will reduce the thinking power for understanding visual information. Some children’s eyes can’t work together due to different reasons such as amblyopia (lazy eye) or a strabismus (squint) so therefore their depth perception (3D vision) is reduced. 

Another common feature is nystagmus (eyes wobble), this can make fixation difficult, and reduces reading speed.   This extra effort can put increased pressure on the visual system, and subsequently on the child can tire more easily.  This is noticeable towards the end of the day; a nap during school if possible helps.  Quite often this isn’t practical and older children will need a break or a lie down in the evening before starting homework.

You may notice a head tilt or turn when a child is looking at something of interest or trying to concentrate on something visually.  This head position called ‘the null point’ which is unique to them, is adapted subconsciously and shouldn’t be corrected.  It allows the nystagmus movement to lessen and become more controlled in that particular position, thus improving their focus and vision.  Small adjustments can make reading and fixation a little easier such as

  • Placing finger on page of good / high contrast reading material,
  • Clean school black/white board free from glare and dust,
  • Closing blinds on sunny days,
  • Slanted boards for reading.
  • Preference seating (toward front of the classroom)
  • Providing a classroom assistant to help out, flag up problems, or photocopy material into larger print (ask your optometrist / GP/ Ophthalmologist or Social Services about ‘Statementing’).

Importance of a regular eye examination

Lots of useful information can be gathered during an eye test.  The optometrist will make the eye examination as fun and as interesting as possible.  Different letter and picture charts are used, and quite often little lights are shone into the eyes for an eye health and prescription check.

As discussed previously (see accommodation) from time to time drops are required to get a gold standard base line measurement of your child visual function.  The eye drops (cycloplegic drops) can sting for a few seconds, and temporarily remove the eye muscles ability to accommodate (focus) thus as parents you will notice the large pupil, and the child may report some blurred vision.  But these are only temporary and the benefits from an eye test of this kind are vast. This type of refractive eye test is necessary as children’s eyes change a lot as they are developing; but as the child grows they will need the drops instilled less and less.

It is very helpful to bring some dark sunglasses for the way home as this will make things much more comfortable until the effects wear off (12-24 hours later).


  • Accommodation

    Accommodation is the process by which the optical power to maintain a clear image on an object as it draws near the eye. In other words the eye changes the shape of the lens in order to bend the light rays from a near object to focus on the retina (see figure 5 below). The more long sighted a person is, the more the eye has to work. This continued strain can result in headaches and tired eyes. The eyes ability to accommodate gradually reduces over time. An adult in their early to mid forties will begin to notice that near print is no longer clear, and that they now need reading glasses (a positive lens will bend the light onto the retina- this person is experiencing Presbyopia (age related loss of accommodation) which is perfectly normal). The young human eye can change focus from distance to near (7 cm from the eye) in 350 milliseconds!.2 This can make measuring a child’s refractive error (strength of glasses) very difficult. The young eyes ability to change focus so quickly combined with a child’s behavior (i.e. looking around room from distance to near) means that the eyes power fluctuates dramatically. In order to ascertain an accurate baseline measurement of a young child’s refractive error the optometrist will use cycloplegic eye drops (note: these may sting for a few seconds). Parents will notice a large pupil as the eye drops temporally prevent the eye muscles ability to accommodate (change focus); this is a gold standard optometric procedure and its importance is paramount. As a child gets older they will need the drops less and less, as co-operation increases.

  • Amblyopia

    Is the term used for a ‘lazy eye’. It is an eye that has more reduced or poorer vision than the other. Usually an amblyopic eye is a healthy eye that cannot be corrected with glasses (to achieve a ‘normal level’ of vision) due to poor development. Quite often a child with amblyopia or a lazy eye has or can develop a ‘strabismus’ or squint. The brain will begin to ignore the blurred image coming from the affected eye. Optometrists and orthoptists work together to try to prevent amblyopia occurring; using glasses (giving the poor eye as clear an image as possible) and also sometimes with patching (patch good eye to force poor eye to see). This can be done whilst the eye is developing, but once the child is approximately 8 year old, the visual system is fully formed and cannot be manipulated. Amblyopia therefore cannot be reversed after this age.

  • Astigmatism

    Astigmatism usually means that the front surface of the eye is shaped of like a rugby ball. It is very common in both visually normal and visually impaired individuals. Two main curves are found: one flatter and the other steeper. This shape causes light to focus in two different positions where the more curved area focuses further forward and the less curved focuses further back. The effect on vision is to distort objects, so similar shaped characters become confused. For example, the letter 'G' may be confused with a 'C' and the number '2' may be mistaken for the letter 'Z'. This can be easily corrected with a combination of lenses (so that your prescription is written a little longer as discussed below).