Why doesn’t my optician check my phorias?
Opticians in the UK do usually check phorias. it is the test where you are asked to look at the line and the light. Generally if the phoria is small, the optician will just note it down but won’t suggest treating it.
Is phoria sensitivity the same as binocular vision dysfunction?
Phoria sensitivity is the same as binocular vision dysfunction but it can be more complex to treat than some people realise. People who have straight-forward binocular vision dysfunction might benefit from vision therapy. However, some highly sensitive people receive constant data from both of their eyes independently as well as from their eyes as a pair. This overloads the visual system and nervous system, making it harder to achieve perfect binocular vision. What is required is to find the exact eye gaze and treat that with small amounts of prism to bring your eyes back into alignment. Whereas with strabismus you usually have prism going in one direction or one direction in one eye and the opposing direction in the other eye, with phorias you need to treat each eye individually. For instance one eye may need to come DOWN and and IN and the other eye may need to go OUT. The aim of helping yourself with your phoria sensitivity is to find maximum comfort by regaining your binocular vision.
Is a phoria the same as a squint (strabismus?)
Phorias and strabismus are both eye turns. They give you the feeling of having misdirected gaze. However strabismus can usually be detected by the human eye and although it might be intermittent, it will likely recur in the same direction to the same strength. A person will be said to have a right eye turn or a an up eye turn. The treatment is to align the eyes to attain binocular vision. This can be achieved with prism, or helped through vision therapy or behavioural optometry.
Phorias are more complex. A phoria is an eye turn or misdirected eye in any of the 8 compass points. And both eyes could have the same pattern, a different pattern or only one eye could be affected. When you add 8 to the possibility of having 0 phoria in one eye you get what is officially called the 9 cardinal points of gaze. This means that when you consider phoria can affect either eye, both eyes symmetricaly or both eyes asymmetrically, there are 81 permutations of phoria.
Is having a dominant eye significant with phoria sensitivity?
You have probably heard people talking of a ‘dominant eye’ in the context of sport or photography or an activity where you are looking for your best visual acuity. Contrary to popular belief, though, your dominant eye doesn’t always have better vision than your non-dominant eye. Essentially, it just means that this particular eye relays information more accurately to your brain’s visual cortex than the other eye.
With phoria sensitivity, it is important to remember that the dominant eye has more processing power to accommodate for discrepancies and the less dominant one has less processing power. This may affect the choice of solution when it comes to combining prism. The aim is always to keep both eyes happy in order to maintain binocular vision.
Can phorias affect my colour perception?
To answer this I will need to talk about the fovea. The fovea centralis, or fovea, is a small depression within the neurosensory retina where visual acuity is the highest. The fovea itself is the central portion of the macula, which is responsible for central vision. This is where the image needs to fall in order to experience good acuity and colour perception.
When we have phorias, the image can fall slightly off the centre of the fovea. This causes us to lose acuity and it can also affect our colour perception. This is due to the fact that the green and red cones are concentrated in the fovea centralis and the blue cones (having the highest sensitivity) are mostly found outside the fovea centralis. As a result, when the image falls slightly off centre of the fovea, we can lose perception of ‘red and green’ and perceive the world as a little more ‘blue’.
So if you have wondered why sometimes colours appear a bit lack lustre, to lack warmth or be too bright, you may be disturbed by your phorias.
What causes phoria sensitivity?
Some people are more affected by their phorias when they are tired or stressed. Some people are more affected by their phorias as the spectral light changes across the day and seasons. Only some of these people are sensitive to their phorias, meaning that they cause them visual disturbance.
Do tints help phoria sensitivity?
Tints can help phoria sensitivity if the cause is spectral sensitivity. However people with spectral sensitivity usually can’t find one colour tint that would work for them continuously. The changing weather and light levels constantly change the person’s perception of the spectrum, thus changing the colour of the tint required. When gaze is successfully directed with prism, a person won’t need tints. In fact you will find it hard to believe that you are not wearing sunglasses when you go outside for the first time wearing the correct amount and direction of prism if you have had problematic phorias.
Do you test for phoria sensitivity?
I am not qualified to test you but you can test yourself. You can use 4 tests to help you detect the direction and strength of your gaze. The first is a variation of the standard test used by opticians (the maddox rod test) called the Light Gaze Test. This shows clearly the direction and strength of your phorias in both of your eyes. The other tests I recommend all measure how much your phorias are affecting you and further help you assess the correct prism for your phoria. These tests include a Spot Test, Reading Test and Prism Test. The tests you choose will depend on the level of your sensitivity. It is not necessary to look at bright lights, read black on white or look through the small aperture of the trial frames if this causes you disturbance.
My optician gave me prism for strabismus (a squint) but it is not comfortable. Do you think I could find myself a better solution?
An eye test only captures the state of your vision in one moment of time. Squints can alternate between eyes and be intermittent. Stimuli that could change the direction and strength of a squint include tiredness, stress and also changes in the atmospheric light. It is not comfortable to have misdirected eye gaze but it is also not comfortable to wear prism when the eye isn’t asking for prism. I can teach you how to fine tune your use of prism so that you can find a way to maximise your comfort levels in different lights and different situations.
What is a Micro-Prism?
A microprism is simply as small power of prism. Often this is all we need to treat our phoria and redirect our gaze. Sometimes a phoria will require a higher strength prism but this may just be at a particular time of year or in a particular light.
I have glasses for long sight / short sight / astigmatism but they don’t always feel strong enough or sometimes they feel too strong. Do you know why?
Yes, When eyes have a misdirected gaze they are in distress. Your brain may not accept a prescription that would be only be right for you if the gaze of both your eyes was correct and working well together. The more we try refractive corrections the more the brain will resist the correction if your gaze is not in line. This is why sometimes we feel our prescription is wrong. Our eye gaze was not correct at the time of our vision test.
I have had vision therapy but it didn’t work. Why do you think this might be?
If you have undiagnosed phorias then vision therapy for conditions such as convergence insufficiency won’t work for the same reason as I explained in the point above. Misdirected gaze makes it impossible for the brain to accept any other type of visual correction. Correction of the phorias naturally improves convergence.
Are you a qualified optometrist?
No, I am a qualified teacher, visionary and mum! I had no idea my journey would lead me here but I have dug very deep to try to understand my extreme sensitivities and this is where I ended up! Working with my phorias has given my life back and I just want to help other people experience the same.
How Do I Buy My New Glasses?
There are many online shops that sell glasses to a person’s prescription and some of these are able to add prism. I am happy to recommend ones that I have found work well for me.
Will I Only Need One Extra Pair of Glasses?
How many extra pairs of glasses you need will depend on the type of phorias you have. Some people only have one simple phoria to correct. Other people’s needs are more complex. People with extreme light sensitivity may need to be test themselves in different lights / weathers / seasons to find all the glasses they need to keep them comfortable through the year.