Corneal conditions

The cornea is the avascular, transparent, richly innervated anterior-most snrface of the globe, which is the eye s primary refracting snrface. As a result of these characteristics, diseases and disorders of the cornea can result in symptomatology, snch as loss of vision, pain, and photophobia, that generally prompts the patient to seek care. Both the prevalence and potential severity of corneal conditions obligates the eye care provider to be hilly versed in the diagnosis, treatment, and management of corneal diseases and disorders. 

This chapter provides practical imormation regarding common corneal conditions that may require treatment. By nature of its anatomic proximity to and integration with other ocular and adnexal strnctnres, corneal abnormalities may result from diseases primary to the eyelids, conjunctiva, lacrimal system, episclera, and other tissues. The details of these conditions are not emphasized in this chapter thus the reader should refer to other appropriate chapters for this imormation. 

Treatment of HSK is primarily based on whether the corneal condition is caused solely by active virus, as is foimd in epithelial dendritic keratitis, or has an immime component, as is typical of disciform keratitis. No treatment has been proven to remove the virus from the ganglia, so treatment is designed to stop the replication of the virus, eradicate live virus, reduce the rate of recurrence, and maintain visual acuity. 

In humans, vitamin A deficiency manifests itself in the following ways night blindness, xerophthalmia, Bitot s spots, and corneal involvement and ulceration. Changes in the skin have also been observed. Although vitamin A deficiency is seen in adults, the condition is particularly harmful in the very young. Often, this results from malnutrition (56). 

These drugp possess anti-inflammatory activity and are used for inflammatory conditions, such as allergic conjunctivitis, keratitis, herpes zoster keratitis, and inflammation of the iris. Corticosteroids also may be used after injury to the cornea or after corneal transplants to prevent rejection. 

Treat acute bacterial conjunctivitis with broad-spectrum antibiotics. Although the condition is usually self-limiting, antibiotic treatment decreases the spread of disease to other people and prevents extraocular infection. Additionally, treatment may help decrease the risk of corneal ulceration or other complications that affect sight. Finally, treatment speeds recovery.14... 

Previous ocular or eyelid surgery Loose sutures Previous corneal surgery Ocular Surface Disease Misdirection of eyelashes Abnormal lid anatomy or function Tear film deficiencies Ocular infection such as conjunctivitis or blepharitis Systemic Conditions Diabetes mellitus... 

Diagnostic drugs, such as sodium fluorescein, are administered topically or intravenously to aid in the diagnosis of such conditions as corneal abrasions or ulceration and various retinopathies. This agent has become the most widely used diagnostic agent in the... 

Eyes are especially susceptible to vesicants. In addition to the immediate corrosive effects, the cornea of the eye can become inflamed (keratitis) after a latency of 6-10 years. This condition can progress to blindness. Corneal lesions may reoccur even after receiving a corneal transplantation. 

The conditions that may predispose a patient to the development of skin and soft-tissue infections (SSTIs) include (1) a high concentration of bacteria, (2) excessive moisture of the skin, (3) inadequate blood supply, (4) availability of bacterial nutrients, and (5) damage to the corneal layer allowing for bacterial penetration. 

Another 3-D cornea model, comprising rabbit primary cultures of epithelial and stromal cells as well as mouse immortalized endothelial cells, was described in 1994 by Zieske and coworkers [70], They showed the influence of endothelial cells on the formation of a tightly packed, multilayered epithelium as well as the expression of laminin, type VII collagen, a6 integrin, keratin K3, and a-enolase. Furthermore, their findings suggested that the formation of an in vivo-like epithelium requires the cultivation of the 3-D corneal construct under AIC conditions. By contrast, LCC methods of cultivating corneal equivalents in the absence of endothelial cells failed to promote the expression of differentiation markers and basement membrane components. 

A concentrated solution of chromic acid in the eye causes severe corneal injury chronic exposure to the mist causes conjunctivitis. Prolonged exposure to chromic acid mist causes dermatitis, which varies from a dry, erythematous eruption to a weeping, eczematous condition. 

Owens and Punte3 tested CS solutions in rabbits and monkeys by dropping 0.2 ml of 1% CS in dipropylene glycol into one eye of each rabbit or monkey, the other eye serving as a control. Six animals were used in each test. Conjunctival redness and swelling lasted for 1-3 d. The experiment was repeated, but with applications of 0.2 and 0.05 ml on 5 successive days. The 0.2-ml applications produced conjunctivitis, iritis, severe chemosis, and corneal ulceration. The 0.05-ml applications resulted in conjunctivitis, moderate chemosis, and iritis. These conditions had all cleared 7-10 d after the last dose. Rabbits and monkeys had qualitatively similar symptoms, but they were less severe in the monkeys. 

In normal state, the cornea has no vascularity. After lesions, scarring and the modification of the physiological conditions cause a vascularization with diminution of the corneal transparency. 

The deep lamellar keratoplasty (DLK) consists in transplanting the stroma and the epithelium of the graft while preserving the Descemet membrane and the endothelium of the recipient. It is used to treat corneal bums in which the Descemet membrane and the endothelium have been spared. The graft is sampled and preserved in the same conditions as the graft used for a TK. The operation begins with an 8 mm... 

Transcorneal and transscleral iontophoresis, at the same conditions, can produce different toxicity levels due to the significant differences between cornea tissue and sclera. Any damage to the corneal surface immediately affects the vision and comfort of the patient, which is less pronounced when applied to the sclera. The clarity of the cornea is essential for interaction with light whereas the sclera is not relevant for light interaction. The cornea is an avascular and highly innervated tissue, unlike the sclera, and thus very sensitive to pain and hypoxia. On one hand, transcorneal iontophoresis endangers the front window of the eye, but on the other hand transscleral iontophoresis threatens the retina underneath the application site, which is essential for visual image formation. 

Ethylmorphine hydrochloride (Dionine ) resembles codeine more closely in its action than it does morphine. It is used primarily as a chemotic to produce vasodilatation and edema of the conjunctiva in corneal ulcer and other inflammatory conditions of the eye. For this purpose, it is instilled topically as a 1 to 5% solution in the eye. It has also been used as an antitussive in doses of 15 mg. 

Indomethacin enjoys the usual indications for use in rheumatic conditions and is particularly popular for gout and ankylosing spondylitis. In addition, it has been used to treat patent ductus arteriosus. Indomethacin has been tried in numerous small or uncontrolled trials for many conditions, including Sweet s syndrome, juvenile rheumatoid arthritis, pleurisy, nephrotic syndrome, diabetes insipidus, urticarial vasculitis, postepisiotomy pain, and prophylaxis of heterotopic ossification in arthroplasty, and many others. An ophthalmic preparation seems to be efficacious for conjunctival inflammation (alone and in combination with gentamicin) to reduce pain after traumatic corneal abrasion. Gingival inflammation is reduced after administration of indomethacin oral rinse. Epidural injections produce a degree of pain relief similar to that achieved with methylprednisolone in postlaminectomy syndrome. 

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