الفهرس 
Cover EnglishOnly 14 pages are availabe for public view
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Abstract
The conjunctiva is a vascularized mucous membrane that covers the anterior surface of the globe. Its superficial layer, the conjunctival epithelium, is continuous with the epidermis of the lids and the outer most layer of the cornea, the corneal epithelium. Poor tear film quality, stability, oxygen deprivation, lens deposits all contribute to dry eye lid disease and allergies. The conjunctiva also has enormous potential for combating infection for four reasons: 1-It is highly vascular. 2-The different cell types contained in it can initiate and participate in a defensive inflammatory reaction. 3-There are many immunocompetent cells which contribute a rich supply of immunoglobulins, secretory IgA is a critical local defense mechanism of mucosal immunity. 4-The surface anatomy (microvilli) and biochemistry (enzymatic activity) of the conjunctival cells enable that tissue to engulf and neutralize foreign particles such as viruses. The conjunctiva is a nonkeratinized stratified epithelium. The conjunctival epithelium contains goblet cells which produce mucin, the most layer of the tear film, the epithelial characteristics and mucin production are crucial for ocular surface integrity. The pathologic transition of nonkeratinized stratified epithelium, either secretory or nonsecretory, to a non-secretory keratinized epithelium is called squamous metaplasia, a process involving abnormal epithelial differentiation and the incidence of dry eye increased dramatically. Squamous metaplasia has been described in a variety of ocular surface disorders as in cases of allergy, chronic conjunctivitis, trachoma, vitamin A deficiency also in cases of contact lens wearers and after cataract surgery and account for most if not all clinical symptoms and morbidity LASIK may cause some patients to experience dry eyes after their surgery. This is especially true if there was tendency toward dry eyes before the LASIK procedure. During the LASIK procedure, a thin layer of tissue is created, called a flap, under which the actual laser energy is applied to reshape the cornea to correct near sightedness, far sightedness and astigmatism. Anatomically, when the flap is created, the very fine cornea nerves may be severed as part of the LASIK procedure. This is a normal part of the procedure. However, these nerves are required in order (signal) the Lacrimal Gland to produce tears. So sometimes, the temporary interruption of the corneal nerve impulses can actually cause a lesser amount of tears to be produced, resulting in Dry Eyes after LASIK.. Sometimes if the Dry Eyes after LASIK are moderate or severe, your vision may actually be blurry due to tear film instability. The LASIK surgeon may elect to treat patient for Dry Eyes before LASIK procedure in order to fortify his tear film so that he will have a comfortable and asymptomatic post operative period. All LASIK patients will need to use artificial tears or lubricating drops as it helps the tear film reestablish itself after the LASIK procedure. During consultation it is important to disclose any symptoms the patient may have of dry eyes and to disclose any medications he is taking that might predispose him to dry eyes after his LASIK procedure. For this purpose impression cytology technique has been developed. Impressional procedures provide superior information about anatomic location of the specimens, cell-cell relationship, and interaction between epithelial cells and other cellular components. Impression cytology using a piece of cellulose acetate filter paper as a simple procedure for conjunctiva biopsy. Recently, have widely utilized impression cytology to measure goblet cell densities in many ocular surface disorders. In this way, the LASIK surgeon can take the necessary steps to prescribe whatever is necessary to obtain the best possible results for his patient.