Corneal scarring

Acute oral LD q data for nitro alcohols in mice are given in Table 1. Because of their low volatiHty, the nitro alcohols present no vapor inhalation ha2ard. They are nonirritating to the skin and, except for 2-nitro-1-butanol, are nonirritating when introduced as a 1 wt % aqueous solution in the eye of a rabbit. When 0.1 mL of 1 wt % commercial-grade 2-nitro-1-butanol in water is introduced into the eyes of rabbits, severe and permanent corneal scarring results. This anomalous behavior may be caused by the presence of a nitro-olefin impurity in the unpurifted commercial product. 

Another widespread application of cold storage of tissue for transplantation is that of preservation of the cornea. Inj uries leading to corneal scarring, various kinds of diseases, and the production of comeal opacity are leading causes of blindness. Cornea transplantation is a commonly used and highly successful procedure. It... 

Untreated bacterial keratitis is associated with corneal scarring and potential loss of vision. Corneal perforation may cause the loss of the eye. 

Untreated bacterial keratitis is associated with corneal scarring and potential loss of vision. Corneal perforation may occur and the patient may lose the eye. In virulent organisms, this destruction may occur within 24 hours. Central corneal scarring may result in vision loss even after successful eradication of the organism. 

Topical corticosteroids are employed in some cases of bacterial keratitis. The suppression of inflammation may reduce corneal scarring. However, local immunosuppression, increased ocular pressure, and reappearance of the infection are disadvantages to their use. There is no conclusive evidence that they alter clinical outcomes. If the patient is already on topical corticosteroids when the keratitis occurs, discontinue use until the infection is eliminated.19... 

Eyes Severe damage. Instant pain, conjunctivitis and blepharospasm leading to closure of eyelids, followed by corneal scarring and iritis. Mild exposure produces reversible eye damage if decontaminated instantly. More permanent injury or blindness is possible within one minute of exposure. 

Paraquat is commonly combined in commercial herbicides with diquat, a related compound in several instances, the commercial preparations splashed in the eyes have caused serious injury. " Effects have been loss of corneal and conjunctival epithelium, mild iritis, and residual corneal scarring. In contrast, in the eye of a rabbit, one drop of a 50% aqueous solution of pure paraquat caused slow development of mild conjunctival inflammation and pure diquat proved even less irritating. Presumably, the surfactants present in the commercial preparations are responsible for the severe eye injuries to humans. ... 

Ocular Effects. Ocular effects can occur as a result of direct contact of eyes with chromium compounds. These include corneal vesication in a man who got a drop or a crystal of potassium dichromate in his eye (Thomson 1903) and congestion of the conjunctiva, discharge, corneal scar, and burns in chromate production workers as a result of accidental splashes (PHS 1953). Higher incidences of subjective complaints of eye irritation were reported by housewives who lived near a chromium slag construction site than by controls (Greater Tokyo Bureau of Hygiene 1989). 

Figure 29-2. Residual corneal scarring following administration of vitamin A therapy to a 3-year-old who had experienced vitamin A deficiency (case study 2).

Trachoma can be effectively treated with a 4- to 6-week course of topical tetracycline ointment. Additionally, oral tetracycline 250 mg four times a day or doxycycline 100 mg orally twice a day for 14 days is an effective option if not contraindicated. Alternatively, azithromycin in a single oral dose (20 mg/kg) was found to be equally effective in resolving active trachoma and offers the advantage of increased compliance. Reinfection rates are high, especially in endemic areas. In patients with severe conjunctival cicatrization, surgical intervention may be required to correct trichiasis and entropion and to prevent corneal scarring. 

It is common for corneal scarring to remain once the edema related to acute hydrops resolves. Topical ophthalmic steroid drops may be used in an effort to minimize resultant scar formation. 

Figure 26-26 During routine examination, a small full-thickness corneal scar was noted from prior corneal injury arrouf).The patient also exhibited an iris sphincter tear and small rosette cataract but denied a prior traumatic ocular event.

Penetrating keratoplasty may restore functional vision when posttraumatic corneal scars are dense and... 

A wide range of substances that are toxic to the cornea may produce epithelial insult known as toxic keratitis. This terminology is generally reserved for mild superficial corneal irritation after contact with a harmful substance. Solutions foreign to the eye that commonly cause toxic keratitis include shampoos, lotions, and chlorinated pool water. Toxic corneal reactions have been reported from tonometer tips contaminated with 70% isopropyl alcohol or hydrogen peroxide that was not fully removed after disinfection of the probe. Irreversible corneal scarring has resulted from inadvertent ocular contamination with chlorhexidine gluconate, a skin cleanser used preop-eratively. The mistaken use of nonophthalmic products for eyedrops may result in various forms of corneal trauma. 

The vessels associated with the phlyctenule also migrate toward the center of the cornea and produce focal neovascularization. Triangular corneal scars with their base at the limbus often form as phlyctenules heal. These scars can be vascularized. Scarring in the central cornea can decrease visual acuity if the phlyctenulosis is long-standing. Corneal perforation in phlyctenulosis is rare but has been reported. 

Figure 26-48 Disciform corneal scar secondary to HSK disciform (stromal) keratitis. (Courtesy of Pat Caroline.)...

Deep corneal edema with folds in Descemet s membrane, in the presence of an intact epithelium, can develop from 3 to 4 months after acute HZO. This disciform keratitis may involve the full thickness of the cornea and may be surrounded by a ring-like cellular infiltrate called a Wessley ring. It is considered to be an immune response to viral antigens and responds quickly to topical steroids, especially when initiated early. Unfortunately, it is common to have recurrences when steroids are tapered or discontinued and can lead to corneal scarring or, more seriously, corneal melt.There is often an associated anterior uveitis with keratic precipitates as well as diffuse corneal edema, endothelial cell loss, and increased lOP secondary to trabeculitis. 

Corneal scarring that affects vision is best treated with penetrating keratoplasty. Penetrating keratoplasty generally is considered to have a poor outcome after HZO because of recurrent or chronic inflammation, vascularization, glaucoma, and poor tear film quality. The chances of success seem to improve, however, if the corneal surfece is protected after surgery by lubricants, therapeutic lenses, or tarsorrhaphy or if there has been a long interval since the previous occurrence. 

Penetrating keratoplasty may be needed after pharmacotherapy if a visually debilitating corneal scar remains. The use of keratoplasty as a therapy for Acanthamoeba keratitis that is not responding to medical therapy is a subject of debate. It is preferable to perform the surgery when active inflammation is not present, and recurrence appears to be common if it is... 

VKC may present as a palpebral disease, limbal disease, or mixed disease that has both limbal and palpebral manifestations. Palpebral or mixed disease has the most serious sequelae, which include corneal scarring and vision loss. 

Patients with AD can also present with eyelid dermatitis, nipple dermatitis, and cheilitis of the lips. Eyelid dermatitis and chronic blepharitis are commonly associated with AD, and can result in visual impairment from corneal scarring. Other ocular complications include atopic keratoconjunctivitis, vernal conjunctivitis, and keratoconus. ... 

During World War I, mild conjunctivitis accounted for 75% of the eye injuries complete recovery took 1 to 2 weeks. Severe conjunctivitis with minimal corneal involvement, blepharospasm, edema of the lids and conjunctivae, and orange-peel roughening of the cornea accounted for 15% of the cases recovery occurred in 2 to 5 weeks. Mild corneal involvement with areas of corneal erosion, superficial corneal scarring, vascularization, and iritis accounted for 10% of the cases convalescence took 2 to 3 months. Lastly, severe corneal involvement with ischemic necrosis of the conjunctivae, dense corneal opacification with deep ulceration, and vascularization accounted for about 0.1% of the injuries convalescence lasted more than 3 months. Of 1,016 mustard casualties surveyed after World War I, only 1 received disability payments for defective vision.10... 

Fig. 27-6. Ocular vaccinia following inadvertent autoinoculation with vaccine. This complication can cause corneal scarring and hence visual impairment. Ocular vaccinia should be treated aggressively with a topical antiviral drug under close ophthalmological supervision. Reprinted with permission from Fenner F, Henderson DA, Arlta I, Jezek Z, Ladnyi ID. Smallpox and Its Eradication. Geneva, Switzerland World Health Organization 1988 298. Photograph by C. H. Kempe.

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