The use of dyes by opticians and optometrists is an essential method for assessing the ocular surface. The dyes can make damaged or irritated areas easily visible to your eye care specialist. It is especially important when it comes to the check-up of contact lenses. With the dyes, the flow of a tear-film under the contact lens can be checked. The dye usually shows the following on an eye:
- Infections
- Dry eyes
- Irritations due to contact lens wear
- Irritation due to chemicals
- Irritations due to heat
- Scratches
- Mechanical irritation due to foreign particles
- Tear film break up time
Depending on the part of your eye the optician wants to check different dyes are used or a mixture of them. Typical dyes are:
- Sodium fluorescein
- Fluorexon
- Lissamine green
- Rose bengal
Due to the toxicity of rose bengal, it got slowly replaced in recent years by lissamine green which causes much less discomfort. Sodium fluorescein is being used for check-ups of the cornea of the eyes. When it is applied to your eye you might see slightly yellow for a moment. With this dye damaged parts of your cornea shine green when blue light shines on your tear film.
In addition to this, the amount of tear-film becomes visible, and especially with rigid gas permeable lenses, the eye care specialist knows where the lens has too much contact or where more bearing would lead to an optimized fit. Here in the picture below the dye gets applied and you can see what the eye care specialist sees when using the microscope.
As mentioned above the sodium fluorescein is best used for the check-up of the cornea. In a lot of cases, it can also be used to make ocular surface irritations visible in the conjunctiva (the white part of your eyes) which stems from soft contact lenses. In the picture below you can see the imprints of a soft contact lens made visible by sodium fluorescein in our optical shop.
To further enhance the check-up in the area around your cornea lissamine green will be used to make check the ocular surface. This is especially important when it comes to big contact lenses like scleral lenses that cover this area too. You can find further information to the mixture of dyes in the tfowsDEFS report 2 which you can read more about here.
The test with the dyes should not be mixed up with the pupils dilating eye drops. The dye here has nothing to do with those eye drops. After the dyes got applied to your eye you can see normal and after a few minutes, your vision is not even influenced anymore by the orange color.
When Should My Eyes Get Checked Without Dye?
Your eyes should get checked without the dye when it is key to have performed the examination of your eyes with an untouched tear-film. For example, when the eye care specialist wants to know how the wetting of the contact lens works on your eye and if the results are great the dye should not be applied.
However, those tests can be stilled packed into one visit the eye care specialist will go through the routine to get the most information out of the visit.
Can the Dye Permanently Stain My Eyes?
The dye can not permanently stain your eyes. It will be flushed away by your tear film in approximately 10 minutes. With your tear film, the dye will be transported to the tear ducts where it will runoff. Depending on the amount of fluid that runs off through your tear ducts this process can take up to an hour. But in most cases, it takes less than that.
Can Fluorescence Dye Permanently Stain My Contact Lens?
Yes, soft contact lenses can be permanently stained with fluorescein. Therefore eye care specialists have two sorts of fluoresceines. One can be applied to soft and rigid contact lenses and the other should only be used for rigid contact lenses.
How Often Should Your Eyes Get Checked With Dyes?
The period from check up to check up is highly dependent on the condition of your eyes and the reason for the test. For example, most contact lens wearers should be tested with the day every six months. The tear film can always change in its quantity and quality. This is why it should be regularly checked how the cells on your eyes do.
When the trauma of your eye is observed it might be just a single event. When wearing specialty contact lenses the eyes might get checked every three months.
Conclusion
The eye care specialist has various dyes at his disposal which enable him to color different changes in the eye. Many changes that occur when wearing soft contact lenses only become visible or can be differentiated from other changes through the dyeing process.
I wish you a great day.