Ocular surface

To remain safe and efficacious on the eye, contact lenses must maintain clear and wetted surfaces, provide an adequate supply of atmospheric oxygen to and adequate expulsion of carbon dioxide from the cornea, allow adequate flow of the eye s tear fluid, and avoid excessive abrasion of the ocular surface or eyeflds, all under a variety of environmental conditions. The clinical performance of a contact lens is controlled by the nature of the lens material the lens design the method and quaUty of manufacture the lens parameters or specifications prescribed by the practitioner and the cleaning, disinfection, and wearing procedures used by the patient. 

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... 

The ocular surface and the tear-secreting glands of the eye are now known to function as an integrated unit. This unit refreshes the tear supply and clears used tears. An autonomic neural reflex loop stimulates secretion of tear fluid and proteins by the lacrimal glands. The sensitivity of the ocular surface decreases as aqueous tear production and tear clearance decreases. This results in a decrease in sensory-stimulated reflex tearing which exacerbates dry eye.29,30 Over time, wearing contact lenses also desensitizes the cornea by constant stimulation.12... 

Dysfunction may be caused by aging, systemic inflammatory diseases, a decrease in androgen hormones, surgery, ocular surface diseases (such as herpes zoster), systemic diseases, or medications that affect the efferent cholinergic nerves. Decreased tear secretion produces an inflammatory response on the ocular surface called keratoconjunctivitis sicca. This inflammation is now a target for new medications that treat dry eye.29,30... 

Ocular surface dye staining assesses the ocular surface and will show blotchy or exposure-zone punctate areas in the dry eye. 

D Aitken, J Friend, RA Thoft, WR Lee. (1988). An ultrastructural study of rabbit ocular surface transdifferentiation. Invest Ophthalmol Vis Sci 29 224-231. 

Han B, Schwab IR, Madsen TK, Isseroff RR. A fibrin-based bioengineered ocular surface with human corneal epithelial stem cells. Cornea 21 505-510... 

Kinoshita S, Koizumi N, Nakamura T. Transplantable cultivated mucosal epithelial sheet for ocular surface reconstruction. Exp Eye Res 78 483 191 (2004). 

Introduction to the Ocular Surface and the Relative Contribution of the Conjunctiva... 

Figure 13.1 A cross-sectional representation of the ocular surface, highlighting the conjunctival tissue as a thick black contour. Three distinct areas of the conjunctiva are labeled along with adjacent ocular tissues.

A number of ocular surface disorders collectively termed as Dry Eye Syndromes have also been associated with the conjunctiva. For example, a deficiency and/or imbalance in compositions of the tear film is often found on the ocular surface during keratoconjunctivitis sicca. Since the conjunctiva plays a direct role in the maintenance of the tear fluid stability via secretion of mucin [1] by its resident goblet cells [4] and basal fluid secretion driven by electro-osmotic gradients across the tissue [3], the conjunctiva is a well deserved, but not intensively studied, target of interest in research efforts aimed against combating Dry Eye Syndromes. 

V f/T enfs - The primary purpose for an ophthalmic ointment vehicle is to prolong drug contact time with the external ocular surface. This is particularly useful for treating children, who may cry out topically applied solutions, and for medicating ocular injuries, such as corneal abrasions, when the eye is to be patched. Administer solutions before ointments. Ointments preclude entry of subseguent drops. 

Levin MH, Verkman AS (2004) Aquaporin-dependent water permeation at the mouse ocular surface in vivo microfluorimetric measurements in cornea and conjunctiva. Invest Ophthalmol Vis Sci 45 4423-4432 Li 1, Verkman AS (2001) Impaired hearing in mice lacking aquaporin-4 water channels. 1 Biol Chem 276 31233-31237... 

The expressions of eye irritation and eye bums define a variety of interactions of chemical fluids, powders, and foreign bodies when they interfere with the ocular surface [7]. In this chapter, we shall focus on the mechanistic understanding of the known facts in this field. 

If powders or soluble substances are delivered onto the ocular surface they will dissolve. By this dissolving, a huge amount of ions is delivered and osmolarity of tears will result in localized osmolar stress. Ocular bum is related to the contact of highly concentrated substances of more or less dissociation onto the eye. Even a crystal of NaCl is known to be of high corrosivity and irritation due to the locally caused severe osmolar changes [39]. 

After eye bums by exposure of the cornea to 1 mol NaOH for 30 s, osmolarity was 1,380 mOsmol/kg. This reflects the huge changes of osmolarity during eye bums and possibly during treatment. The rinsing with tap water results in an extreme lowering of the osmolarity into the region of 0 mOsmol/kg on the ocular surface. 

Ischemia may be major with absence of blood flux over the entire ocular surface, making it look like dead eye (Fig. 7.5). 

There might be other complications on the ocular surface like ... 

The transplant of nasal mucosa was first prescribed by Naumann for the treatment of severe and bilateral conjunctival mucous shortages. In a study of 24 patients including 16 victims of a severe eye bum with symblepharons, Naumann has observed an improvement of the condition of the ocular surface in all of the cases. He has then concluded that the transplantation of nasal mucosa is better than the transplant of buccal mucosa. When the ocular damage is bilateral, the transplant of nasal mucosa would be perfectly recommended [11]. The nasal cavities are examined with an endoscope in order to find the zone to be sampled. The graft of nasal mucosa is taken from the septum, from the lower or medium turbinates. Under endoscopy and after local anesthesia, the anterior part of the turbinates is usually sampled. A hemostasis is cautiously operated and a gauze plugging of the cavity is set up. This... 

Shimazaki, J., Shimmura, S., Tsubota, K. Donor source affects the outcome of ocular surface reconstruction in chemical or thermal burns of the cornea. Ophthalmology 111, 38-44 (2004)... 

Kenyon, K.R., Tseng, S.C.G. Limbal autograft transplantation for ocular surface disorders. Ophthalmology 96, 709-... 

Holland, J.H., Schwartz, G.S. The evolution of epithelial transplantation for severe ocular surface disease and a proposed classification system. Cornea 15, 549-556 (1996)... 

Erucht-Pery, J., Siganos, C.S., Solomon, A., Scheman, L., Brautbar, C., Zauberman, H. Limbal cell autograft transplantation for severe ocular surface disorders. Graefes Arch Clin Exp Ophthalmol 236, 582-587 (1998)... 

Rao, S.K., Rajagopal, R., Sitalakshmi, G., Padmanabhan, R Limbal autografting Comparison of results in the acute and chronic phases of ocular surface burns. Cornea 18, 164-171 (1999)... 

Tseng, S.C., Di Pascuale, M.A., Liu, D.T, Gao, Y.Y., Baradaran-Raffi, A. Intraoperative mitomycin C and amniotic membrane transplantation for fornix reconstruction in severe cicatricial ocular surface diseases. Ophthalmology 112, 896-903 (2005)... 

Shimazaki, J., Yang, H.Y., Tsubota, K. Amniotic membrane transplantation for ocular surface reconstruction in patients with chemical and thermal burns. Ophthalmology 104, 2068-2076 (1997)... 

Tsubota, K., Toda, I., Saito, H., Shinozaki, N., Shimazaki, J. Reconstruction of the corneal epithelium by limbal allograft transplantation for severe ocular surface disorders. Ophthalmology 102, 1486-1496 (1995)... 

Nakamura, T., Inatomi, T., Sotozono, C., Koizumi, N., Kinoshita, S. Successful primary culture and autologous transplantation of comeal limbal epithelial cells from minimal biopsy for unilateral severe ocular surface disease. Acta Ophthalmol Scand 82, 468-471 (2004)... 

When latanoprost was applied for 4 months to the eyes in 14 patients, there was an increase in HLA-DR expression (17). Since HLA-DR is a marker of ocular surface... 

Pflugfelder, S.C., et al. 2000. Detection of sialomucin complex (MUC4) in human ocular surface epithelium and tear fluid. Invest Ophthalmol Vis Sci 41 1316. 

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