Therapeutic Contact lenses

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Transcript of Therapeutic Contact lenses

  • 1.Manoj Aryal B . Optometry Institute Of Medicine, Maharajgunj Medical campus

2. Introduction Classification of TCL types Essentials of fitting a TCL The aims of therapeutic contact lens wear Complications associated with therapeutic contact lenses wear Aftercare Conclusions Therapeutic contact lens (TLC) 3. Definition: The term therapeutic is derived from the Greek word therapeuein meaning to take care of, or to heal. Mainly fitted with the aim of attempting to maintain or restore the integrity of ocular tissues. 4. The five main aims of therapeutic contact lenses are: 1. Relief of ocular pain; 2. Promotion of corneal healing; 3. Mechanical protection and support; 4. Maintenance of corneal epithelial hydration; 5. Drug delivery 5. Silicone rubber and silicone hydrogels (38%); Hard (PMMA) and gas permeable scleral lenses; Hard scleral rings; Hydrogel soft lenses Low water content ( 38%-45%); Mid-water content (45%-55%); High water content (67%-80%); Collagen shields 6. Silicon Hydrogel They offer theoretical advantage of oxygen transmissibility and is more suitable for overnight wear The disadvantage includes the increased rigidity, poor surface wettability, and limited parameters 7. For painful eyes with irregular corneas, the more soft or flexible the lens the more likely an acceptable and comfortable fit will be achieved Lens deposition may be a problem especially mucin balls The increased rigidity may also be expected to increase the risk of CL related papillary reaction, conjunctivitis and SEAL 8. Applications: Main application is for wound healing (persistent epithelial defect, corneal ulceration etc.). They are used for the apposition of wound edges and pain relief. Corneal ulceration Persistent epithelial defect 9. However, the applications may be constrained by the limited range of total diameters and limited choice of BOZR Some lenses are not available in Plano power, some patients with good visual acuity may not tolerate the change in induced ametropia, such as RCE patients with a VA of 6/5 10. Silicon rubber Silicone rubber lenses are difficult to fit. The total diameter must closely correspond to the corneal diameter Some movement and tear exchange is essential and uniform edge clearance and central corneal alignment is desirable but rarely achieved. 11. The lenses often steepen unpredictably and can bind to the cornea. Thus the fit should be checked immediately following insertion, then again after a few minutes, and after one to two hours and also the following day. Lens removal can be difficult, especially on a dry eye 12. Properties and application: Has a high oxygen transmissibility (Dk 200- 400), and absorbs no water so lens parameters are independent of hydration, tear quality or exposure. The lenses are also robust and flexible but they must be coated to improve surface wetting. Until recently they were the first choice for the maintenance of corneal hydration, e.g. Sjgrens syndrome, exposure and 13. They also offered protection of the ocular surface from eyelashes, keratin, exposure, and glue. In the presence of a severe dry eye silicone rubber lenses improved the ocular environment to assist wound healing of a corneal perforation and to promote re-epithelialization of a persistent epithelial defect. The lens was also used to provide pain 14. With a typical diameter of 23mm,RGP scleral lenses offer protection of both the cornea and the bulbar conjunctiva. If the lens is fitted to give corneal and limbal clearance the lens will maintain a tear reservoir while protecting the cornea from the shearing forces of the eyelids. Thus Sjgrens, cicatrizing conjunctivitis and corneal exposure are typical indications. 15. Irregular or abnormal corneal topography High astigmatism Keratoconus or other primary corneal ectasia Corneal transplant Traumatized eye Post-refractive surgery 16. High refractive errors Centration difficulties with high-power corneal lenses. Intolerance to corneal or hydrogel lens wear in myopia or hypermetropia Iris encapsulation Intractable diplopia. Cosmetic shells. Unsightly blind eyes. Aniridia. Microphthalmos. 17. Therapeutic or protective applications Corneal hydration in serious dry eye conditions such as Stevens Johnson syndrome and cicatricising conjunctivitis, ocular pemphigoid Prevention of tear film evaporation with poor lid closure or lid absence Corneal protection against trichiasis or lid margin keratinisation Preventing mucus filaments adhering to the cornea 18. Other indications include: Maintenance of fornices Ptosis prop Promotion of epithelial healing in the presence of a severe dry eye, and Rarely pain relief, neurotropic keratitis and persistent epithelial defects 19. Excessive Protrusion in keratoconus & Scleral Lens Wear 20. Entropion Ptosis Correction 21. RGP lens that covers the cornea has the advantage of: Offering complete corneal protection Maintaining a corneal tear reservoir and Can be used with topical medication. 22. Also lenses with a high oxygen transmissibility are available Which flex less than silicone rubber, so are less likely to bind. The lenses can be used in severe dry eye, corneal exposure, trichiasis, and; in these cases they assist with wound healing and may even offer pain relief 23. May be used to promote re-epithelialization. They mould to the shape of the cornea and dissolve over time so they have been advocated for managing epithelial defects. However, they are uncomfortable, give poor vision, the cornea cannot be examined through the shield, the dissolution rate is variable and unpredictable, and finally they are difficult to remove. 24. Lens type Primary indications 1)Hydrogels Pain relief a) Thin mid water content with high bound water First choice incl.- irregular corneas, mild to moderate dry eyes b)Steep hydrogel lenses For step corneas c) Large hydrogel lenses For limbal and scleral defects and buphthalmos 2) Silicon hydrogels For wound healing, apposition of wound edges, short term mechanical protection 3) Rigid gas permeable Corneal protection, maintenance of corneal hydration, promotion of epithelial healing 4) Scleral Mechanical protection of ocular 25. Slit lamp The presence of an anterior segment disorder commonly renders the patient photophobic so the ability to diffuse light and/or reduce the intensity of the slit lamp beam is of particular value in minimizing patient discomfort 26. Keratometry Generally not necessary for adequate fitting of soft bandage lenses. However, it may have a value in monitoring the progression of some conditions, for example, keratoconus and progressive corneal dystrophies In the presence of gross corneal distortion and the absence of any corneal graft, measuring K-readings of the fellow non- diseased eye can provide a useful guide. 27. Lens selection A thicker lens may be more desirable when the function is to act as a splint (as in descemetocele) or to cover an irregular corneal surface Thicker lenses may also be desirable in some cases of tear film instability to support a more stable tear structure. A thinner lens is more appropriate in cases of epithelial disruption (for example, recurrent erosion) 28. Ideally, a well fitting bandage lens should provide full corneal coverage, be centered, with adequate movement (>0.25mm with each blink) to allow clearance of debris. It is important for the lens fit to be stable, avoiding excessive movement, as this can cause discomfort or further epithelial disruption. Stability can be enhanced by increasing 29. Parameter range The majority of bandage lenses used are Plano or near Plano prescription. In most circumstances, soft lenses of standard total diameters 14.0mm to 14.5mm will suffice. Larger diameter lenses (15mm to 20mm) may be required where the specific function is to protect the limbus or prevent wound leakage at suture or incision sites Larger diameter lenses require flatter back optic zone radii to achieve the desired fit. 30. Lens stability Both a stable fit and minimal dehydration are desirable. In cases of irregular corneas, such as advanced cases of keratoconus or post surgery, a stable fit may not be achievable with a single lens material. Piggyback or hybrid lenses can offer success in cases when acceptable centration cannot be achieved with a an RGP alone. 31. Helpful when RGP lens is intolerable due to staining and patient reluctant to surgery where a rigid corneal lens is worn over a soft lens Soft lens Extra limbal negative or Plano soft lens (mod. To high Dk) RGP lens (TD 9.0 & 10.0 mm) Disadvantages RGP rides low with little or no movement Localized hypoxia & neovascularization Difficult to handle/maintain two types of lenses 32. Avoid the use of topical anesthetics as this may mask the pain associated with a poor fitting lens. The lens fit should be assessed after approximately 20 minutes and ideally again after approximately 60 minutes (owing to lens dehydration effects). Peripheral lens fit is also very important as e.g. flared lens edges may gives rise to discomfort etc. A well fitting TCL should have good corneal 33. First Last Poor corneal coverage Increase total diameter Steepen BOZR Excess lens movement Reduce thickness Steepen radius Increase diameter Lens too tight Reduce thickness Flatten radius Decrease diameter Irregular ocular surface Low modulus of elasticity Thin lens Dry eye/ exposure High bound water Reduce water content Non-ionic Increase thickness Restricted Fornices Reduced diameter, typically 13.00mm 34. The cause of ocular pain includes: Exposed or compressed nerve endings in recurrent corneal erosion, Thygeson's disease, and bullous keratopathy Tension from the eyelid on mucous- epithelial tags in filamentary keratitis and superior limbic keratitis. Mechanism: lens protects the cornea from the shearing force of the eyelid during blink. Aim 1: Relief of pain 35. This condition of chronic edema of th