Important dyes used in Ophthalmology – Med Dose
The transcript of the episode “Important dyes used in ophthalmology” has been edited to make it easy for reading.
Important dyes used in ophthalmology
Hello! Hello! Hello! Welcome to another episode of the med dose podcast by sciencetidings.com Today I am going to talk about various dyes used in ophthalmology. This podcast can help you in the 3rd year of MBBS as well as in your competitive exams. Just like every time, the transcript is available on sciencetidings.com to follow along with the audio. Link can be found in the description of the episode on your favorite podcast app. So without any delay, let’s jump straight into it.
In this episode we are going to talk about 6 stains or dyes used in ophthalmology:
- Fluorescein dye
- Rose bengal
- lissamine green
- Indocyanide green
- Trypan Blue
- Triamcinalone acetonide.
We will discuss in detail each dye and its main uses. Let’s start with:
It is an orange color dye. Under cobalt blue light the stained part appears as green fluorescent color.
Uses of Topical fluorescein can be understood by knowing that fluorescein stains areas of denuded epithelium, that is, areas where the epithelium is abraded. So it stains the base of an ulcer.
- Corneal abrasions
- corneal ulcers
- herpetic corneal infections
Other uses of fluorescein dye are as follows:
In applanation tonometry, the intraocular pressure is inferred from the force required to flatten a constant area of the cornea, as per Imbert-Fick law.
- Anesthetic and fluorescein dye are instilled in the conjunctival sac.
- With a cobalt blue filter and brightest illumination, a prism is advanced until it touches the apex of the cornea.
- A pattern of 2 semicircles, one above the other, is adjusted so that the inner margins of semicircles touch each other.
- Reading on the dial is multiplied by 10 to get the intraocular pressure.
Test for dry eye by tear break up time:
In this test, fluorescein dye is added to the eye and the eye is observed under a slit lamp while the patient avoids blinking until breaks (dry spots) develop in the tear film. Generally,>10 seconds is normal, 5-10 sec is marginal, <5 seconds is low, and it indicates abnormal tear film.
Seidel’s test for wound leak
The suspected site of wound leak is stained with fluorescein and the fluorescein pattern is observed for dilution. If aqueous is leaking from the anterior chamber, it dilutes the dye, and the dilution can be appreciated on slit-lamp examination.
Tests for lacrimal drainage by Jone’s dye tests
It is a test to distinguish between anatomical and functional outflow problems. They are done in cases of suspected partial obstruction of lacrimal passage. Jones test I differentiates partial obstruction from hyperlacrimation. Jones test II differentiates partial obstruction from lacrimal pump failure.
- In Jones test 1, we instill one drop of fluorescein in the conjunctival sac, and a cotton bud soaked in anesthetic is placed at the inferior meatus.
- If the fluorescein is detected on cotton bud after 5 minutes, the system is patent, and the cause of watering is hyperlacrimation. It is said to be a positive primary Jones test. If there is no fluorescein dye on the cotton bud, it is a negative primary jones test and it indicates partial obstruction of lacrimal passage or lacrimal pump failure
- Jones test 2: If the first test is negative, the next step is to wash the excess fluorescein from the conjunctival sac and do syringing.
- Cotton bud stained with dye after syringing indicates partial obstruction of lacrimal passage. This is positive jone’s test 2.
- A negative jone’s test 2 indicates lacrimal pump failure.
Fluorescein angiography is used to diagnose and categorize
- Macular degeneration
- diabetic retinopathy
- inflammatory intraocular conditions
- intraocular tumors
Rose Bengal Stain
It is a red or pink color dye. Ocular surface is divided into three zones: cornea, nasal bulbar conjunctiva, and temporal bulbar conjunctiva. Each zone is evaluated for the density of stain, and a score is given from 0 (no stain) to 3 (severe staining).
- Devitalized corneal tissue. Royal Bengal stains devitalized or necrotic tissue. So it stains the margins of the ulcer
- Dry eye: A total score of more than 3.5 is taken positive for dry eye.
- OSSN: Ocular surface squamous neoplasia
Like, rose bengal dye, this also stains the devitalized and necrotic tissue. It can also be used to diagnose dry eye by conjunctival staining. It gives a stippled appearance.
Lesser ocular toxicity as compared to Rose Bengal Stain. It is not compatible with contact lens use. So the eye has to be irrigated after using lissamine green.
Indocyanine green (ICG)
- ICG is used for indocyanine green angiography. When injected intravenously, most of the dye remains plasma protein bound. The dye can not diffuse out of the intravascular compartment and hence is used in imaging the choroidal vasculature in ICGA.
- For staining the anterior capsule during cataract surgery.
- The dye has a high affinity for collagen type IV (which is found in basement membrane) and laminin. Both of these are found in a high concentration in the internal limiting membrane of the retina. Hence, the dye is the used for staining the ILM during vitreoretinal procedures. But because of a property called decomposition, it can cause retinal toxicity.
It is used to stain anterior capsule for performing capsulorhexis in cataract surgery.
It is a synthetic non-soluble corticosteroid.
- It is used for vitrectomy: During vitrectomy, the dye facilitates complete detachment and removal of the posterior hyaloid.
- If a posterior capsular rent occurs during cataract surgery, triamcinolone can be used to know if any vitreous strands are left in the Anterior chamber after anterior vitrectomy.
- Other than as a dye, intravitreal triamcinolone is used for the treatment of macular edema and uveitis.
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