The examination protocol changes when it comes to chemical injury as it is a time-sensitive injury.
Eye irrigation is the first and foremost step if a chemical injury is reported. (irrigate for at least half an hour or 3 liters of fluid (Use tap water if sterile water is not available) sweep the fornices to be sure.
The pH should be assessed five minutes after completion of irrigation, and irrigation is continued till neutrality of pH is attained. Litmus paper may be used in a clinical setting. Always check the pH of both eyes.
The examination is focused on assessing the extent and depth of injury. The degree of corneal, conjunctival, and limbal involvement must be especially documented, as this determines the ultimate visual outcome.
VISUAL ACUITY
It depends on the extent of injury but does not have a linear correlation.
FACE AND FACIAL SYMMETRY
The face may show signs of burn, and damage to lashes, brows, face, mouth, etc, may be seen.
EYELIDS AND ADNEXA
Early – -lid lag (lagophthalmos)-may lead to exposure, desquamation, erythema, loss of lashes
Late - entropion, ectropion, ptosis
CONJUNCTIVA
Check for conjunctival ischemia (blanching) and edema and document separately.
Sweep the fornices – may need Desmarre retractor to double evert upper eyelid – for retained particulate matter.
Stain with fluorescein –
Late Cases – symblepharon, ankyloblepharon, Forniceal shortening, scarring over the opening of ducts of lacrimal glands.
CORENA
Check for limbal ischemia – blanched or pale areas of the litmus, limbal edema and necrotic tissue, hemorrhage, and stagnant columns of blood in vessels that terminate abruptly or are unconnected at both ends of dark columns of blood. The latter changes can mask pallor and mislead one into thinking that there is a lesser degree of ischemia than it actually is
Status OF Epithelium – partial loss, complete loss – document in clock hours – reepithelization is slow.
Status of Clarity – the corneal stromal haze or transparency is measured as the iris's and lens's visibility through the cornea. Corneal changes to be recorded include haze, opacification, edema, striae, and sensations.
Late – corneal vascularization and conjunctivalization of the cornea.
SCLERA
The greater the depth of corneal eye injury, the paler the tissue appears, exposing the ischemic sclera as white marble (marbleized appearance of the limbus and adjacent sclera)
IRIS AND PUPIL
The iris may be stunned and non-reactive due to cationic insult and anterior segment ischemia.
Examine the iris for color change, hypermedia/engorged vessels, hemorrhage, atrophy or necrosis, and pigment dispersion.
Posterior and anterior synechiae may develop rapidly when the iris is affected. The pupil may be dilated or constricted with limited or absent pupil response; show sector changes when partly affected in one sector, usually inferiorly.
Anterior Chamber
In cases of extensive damage, there may be an AC reaction due to inflammation or anterior segment ischemia.
LENS
Due to ocular penetration of alkalis with a resultant increase in pH, there are chances of cataract development.
IOP
High IOP – due to trabecular meshwork distortion, conjunctival and episcleral fibrosis leading to outflow obstruction of the aqueous
Low IOP – ciliary body shut down – damage to anterior ciliary vessels and Cationic insult to ciliary processes.
FELLOW EYE
Check both eyes.
SYSTEMIC CONDITIONS
Esophageal burns and fumes inhalation
PREVENTION
Use of protective goggles when handling chemicals.
QUESTIONS:
How do you check for limbal ischemia?
Currently, there are no standard criteria to diagnose limbal ischemia. Clinicians rely on the subjective appearance of the vascularity and color of the limbus and peri-limbal region and compare that with a mental image of a healthy eye.
For once, red eye is a good eye 😊
Which type of burns are more dangerous?
Acids cause coagulative necrosis, while alkalis cause liquefactive necrosis. The coagulated proteins act as a barrier to further deeper penetration of acids, whereas alkalis, layer by layer, liquefy the protective coats of the globe and thus penetrate more readily. Hence, alkali burns are more dangerous for the same fluid strength and duration of injury.
Alkali substances can pass into the anterior chamber rapidly due to the inability to buffer alkali (within approximately 5-15 min), exposing the iris, ciliary body, lens, and trabecular network to further damage. Irreversible damage occurs at a pH value above 11.5.
Hydrofluoric acid is an exception to the rule, as it is an acid (also sulfurous acid, that can penetrate the eye due to its small size and low molecular weight.
H2SO4 may cause thermal injury.
What is the effect of damage to the limbus?
The limbus contains stem cells in the palisades of Vogt. The corneal epithelial cell replacement is a process that continues throughout life. New cells arise from the palisades and then move centripetally in a whorl-like pattern.
What is the effect of damage to the conjunctiva & Episclera?
The conjunctival vessels – The conjunctival vessels receive drainage of aqueous; therefore, sclerosis to these vessels leads to reduced egress of aqueous from the eye, resulting in raised IOP.
The episcleral vessels – The episcleral vessels contain anterior ciliary vessels that not only supply the limbus but give a significant contribution to the Major arterial circle of the ciliary body, with a resultant effect on the production of aqueous due to the ciliary body's reduced function/shutdown.
Bulbar Conjunctiva – The bulbar conjunctiva contains mucin glands; damage to these results in the loss of the mucin layer of the tear film and, consequently, dry eye.
Forniceal vessels- the fibrosis that occurs in fornices has two-fold effects.
1. Symblepharon formation – loss of capillary action between the bulbar and palpebral conjunctiva, therefore poor wetting of the corneal surface, and secondly reduced ocular motility.
2. Loss of ducts of main and accessory lacrimal glands, resulting in loss of the aqueous layer of the tear film.
Why does opacification of cornea occur in cases of chemical injury?
1. De-epithelization leads to stromal hydration.
2. Alkalis – the cation component of the alkali agent reacts with the carboy group of stromal collagen and GAGs, which leads to opacification of the corneal stroma (and also distortion of the trabecular meshwork)
3. Acids – denatured proteins opacity the epithelium and stroma.
What are the classification systems of Chemical injury?
All the classification systems share the common feature of correlating prognosis with clinical findings that reflect the severity of limbal stem cell injury.
Roper Hall's modification of the Hughes classification
Grade | Prognosis | Cornea | Conjunctiva/Limbus |
I | Good | Corneal epithelial damage | No limbal ischemia |
II | Good | Corneal haze, iris details visible | <1/3 limbal ischemia |
III | Guarded | Total epithelial loss, stromal haze, and iris details obscured | 1/3-1/2 limbal ischemia |
IV | Poor | Cornea opaque, iris and pupil obscured | >1/2 limbal ischemia |
Dua classification scheme for ocular surface burn.
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Grade | Prognosis | Degrees of limbal involvement (clock hours) | Degree of conjunctival involvement | Analogue scale (clock hours / %) |
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I | Very good | 0 | 0% | 0/0 |
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II | Good | ≤3 | ≤30% | 0.3 to 3/1 to 29.9 |
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III | Good | >3 to 6 | >30-50% | 3.1 to 6/31 to 50 |
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IV | Good/Guarded | >6 to 9 | >50-75% | 6.1 to 9/51 to 75 |
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V | Guarded/Poor | >9 to <12 | >75-<100% | 9.1 to 11.9/75.1 to 99.9 |
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VI | Very poor | Total limbal involvement | 100% | 12/100 |
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