ORTHOKERATOLOGY LENS PRESENTATION ppt.pptx

Ortho - K lens presentation
Orthokeratology lens
RGP lens
Soft contact lens
Myopia

1. ORTHOKERATOLOGY ORTHO – K LENS NAOBA MUTUM M.OPTOM

2. ORTHOKERATOLOGY DEFINITION: The systematic and purposeful designing of contact lens to change corneal curvature as applied to patients for reduction, modification or elimination of refractive anomaly (error) mainly with myopia, hypermetropia (not yet treated routinely) and astigmatism achieved by remodelling the anterior refracting surface of the eye . This is impermanent process and results varies between the individuals. Orthokeratology aims to reduce myopia and improve unaided VA. This is achieved by using an RGP lens to induce a regular change in corneal shape so that the prolate (usually) elliptical cornea becomes flatter centrally.

3. ORTHO KERAT OLOGY Straight Cornea Knowledge Aim is to ‘ reshape ’ the cornea. A non-surgical, topographical approach to effecting a correction. Effective and relatively safe way of reducing or eliminating manifest refractive error. Mainly for myopia (hyperopia not yet treated routinely)= impermanent. Subject to significant variability=within an individual/between individuals.

4. ORTHOKERATOLOGY ALTERNATIVE TERMINOLOGY •Corneal Reshaping Therapy(CRT) •Vision Shaping Treatment(VST) •Corneal Refractive Therapy •Accelerated Orthokeratology •Corneal Corrective Contacts •Eccentricity Zero Moulding •Gentle Vision Shaping System •Overnight Corneal Reshaping(OCR) •Reversible Corneal Therapy •Compression Ortho-K •Controlled Kerato-Reformation (CKR) •Corneal Moulding System (CMS) •CL Corneal Reshaping •Overnight Orthokeratology (OOK)

5. Orthokeratology is the logical extension of the early (in the late 1950s/early 1960s) observation by contact lens practitioners that rigid contact lenses (PMMA originally) can modify the shape of the cornea and/or alter the eye’s refractive state . In its original form, orthokeratology sought to flatten the cornea progressively using a series of contact lenses to effect a reduction in myopia and an improvement in unaided visio n . Once the desired level of vision was achieved, or the maximum effect possible was reached, a schedule of so-called ‘retainer’ lens wear was instigated.

6. Such a schedule aimed to maintain the gains achieved. Subsequently, retainer-lens usage was reduced by decreasing the duration and/or frequency of lens wear. Ultimately, the goal was to minimize the use of any lenses, particularly during the day, while maintaining good vision at all other times. Retainer or Treatment Lens: Before settling on a retainer lens, the practitioner, with the patient’s help, must determine that the stage has been reached by which no further myopia reduction is occurring, i.e. the ‘end point’ has been reached. Soni and Horner (1997) stated, “ The final contact lens that allows adequate tear exchange and stable uncorrected vision is considered to be the Retainer lens.”

7. ORTHOKERATOLOGY DESIRABLE PATIENT FEATURES Rx = –0.50Dsph to –4.00DSph. Higher Rxs are possible but outcome is less predictable = avoid a “Cowboy Approach” to how much Change is possible. < 1.50 Dcyl of Corneal Astigmatism. Consider Lenticular Astigmatism when predicting vision = purely lenticular Dcyl is problematic. Central KFlat readings ≥42.00D. 6. Corneas that flatten in the periphery. = i.e. non-spherical, especially prolate elliptical corneas.

8. The amount of ametropia that can be corrected using orthokeratology is approximately 4.0 D of myopia and 1.0 D of astigmatism. ( Koffler et al. [2004] gives a range of –1 to –6 D myopia with 1.5 D of astigmatism, while Mika et al. [2005] gives –1 to –5 D myopia, 1.50 D of WTR astigmatism and 0.75 D of ATR astigmatism), though considerable individual variation exists . A small amount of uncorrected astigmatism is generally acceptable to the patient. Higher degrees of ametropia can be reduced. **In these cases the patient must be aware that their unaided vision will not reach 6/6. Many high myopes are happy to achieve a level of vision that makes them functional and with which they can resort to a low-powered prescription for optimal vision.**

9. ORTHOKERATOLOGY INDUCED ASTIGMATISM • ↑irregular astigmatism • Trend towards ↑with-the-rule astigmatism =↑against-the-rule astigmatism also possible • Even in successful orthokeratology, =↑irregular astigmatism to be found.

10. HOW ORTHO WORKS !!! Overnight Wear : Ortho-k lenses are worn overnight. While you sleep, they gently reshape the cornea temporarily correcting myopia. 2 . Day-time vision : After removing the lenses in the morning, you can see clearly throughout the day without needing glasses or contact lenses. 3. Temporary correction : The effects of Ortho-K typically last for 24 – 72 hours, depending on the individual. For best results, nightly wear is often recommended. Temporary Effects : Ortho-K lenses reshape the cornea to correct myopia, but this reshaping is not permanent. When you stop wearing the lenses, the cornea gradually returns to its original shape.

11. Rebound Effect : After discontinuing Ortho-K treatment, myopia can return to its previous level or even progress further. This is often referred to as a “ Rebound effect .” Maintenance: To maintain the myopia reduction, continuous or regular use of Ortho- K lenses is necessary. 4. It provides clear vision during the day without the need for glasses or daytime contact lenses. Ortho-K has been shown to slow the progression of myopia in children and teenagers by about 50%.

12. **RGP lens wearers progressed less than SCL wearers.** The statement that RGP lens wearers progressed less than SCL wearers suggests that RGP lens might have some effect in slowing myopia progression compared to SCLs. However despite this observation, RGP lenses are generally not prescribed primarily for myopia control. Here’s why : Limited Effectiveness : While RGP lenses may slow myopia progression to some extent, their effect is not as significant as other specialized myopia control methods, such as Ortho-K lenses or certain types of soft contact lens designed for myopia control. Alternative methods : Ortho-K lenses and specially designed SCL have shown greater effectiveness in controlling myopia progression. Clinical progression : Due to their limited effectiveness, and the availability of more effective options, RGP lenses are not typically recommended as the primary method for myopia control.

13. Conclusion : Even though RGP lenses might slow myopia progression more than SCLs, they are not the most effective option available. Therefore, they are not primarily prescribed for myopia control.

14. ** Concluded: RGPs not to be prescribed primarily for myopia control . Long-term wear of RGP lenses can indeed lead to PTOSIS drooping of the upper eyelid and lid oedema(swelling of the eyeball). Here are some key points: PTOSIS : Prolonged use of RGP lenses can exert constant pressure on the levator muscle and tendon responsible for lifting the eyelid. Overtime, this pressure can cause the tendon to loosen, leading to ptosis.

15. PREVALENCE : Studies suggest that prolonged RGP lens wear is a significant cause of ptosis in up to 47% of patients under the age of 50. LID OEDEMA : Mechanism : RGP lens can cause mechanical irritation and reduced oxygen permeability, leading to inflammation and swelling of the eyelids. Management: 1.Regular checkup: regular eye examination can help detect early signs of ptosis and lid oedema. 2.Lens hygiene: proper lens hygiene and fitting can minimize the risk of these complications. 3.Alternative options: considering alternative types of contact lenses or reducing wear time can also help.

16. Advantages of Orthokeratology versus Refractive Surgery The major advantage of orthokeratology compared to current refractive surgical techniques is its reversibility. • Not age-dependent. • Lower cost. The orthokeratology technique maintains binocular vision and also corrects the vision to 6/6 during lens wear. • Less (or no) pain compared with PRK •Therapy can be halted if untoward effects are experienced •Option for children = may slow myopia progression Effect can be modified to incorporate monovision as and when needed. There is some early evidence to support the claim that orthokeratology controls or limits myopia progression in children (Lowe, 2001).

17. Walline (2004) concluded that axial length would be the best measure of myopia control in well-controlled orthokeratology studies. Since SCLs have been shown to have no effect on myopia progression (Horner et al., 1999), he proposed that SCLs rather than spectacles should be used in the control groups for such studies. Axial elongation the main ‘vehicle’ of myopia progression Cho et al found that orthokeratology reduced the growth of eyeball axial length significantly compared with a spectacle-wearing control group. Since then, Cheung et al. (Cho was a co-author) reported a case of unilateral overnight orthokeratology whose results suggested that orthokeratology had slowed the rate of axial length increase in the treated eye only.

18. Wlodyga (1992) also reported on the successful treatment of less-than-successful post-RK patients using orthokeratology. At the time, he predicted that contact lens practitioners would be seeing more of these cases. Arguably, the rise of PRK, and then LASIK and derivatives as the preferred refractive surgery techniques, has reduced the need for orthokeratology post-surgically. A study of orthokeratology in adolescents by Reim et al. (2003) concluded that the DreamLens ® orthokeratology lenses used had a similar effect on myopia progression as RGP DW lenses, i.e. the rate of progress was reduced but not eliminated. However, the authors stopped short of claiming that orthokeratology slowed myopia progression and advised practitioners against making such an assertion.

19. Polse et al. (1983C) reported that any reduction of myopia seen in orthokeratology did not persist once orthokeratology treatment ceased. Saw et al. (2002) reviewed the literature on arresting myopia progression and concluded that no conclusive evidence existed that any of the extensive array of methods employed previously or currently were effective. The conclusion by Saw et al. (2002) means that, reviewing the existing research and literature on various methods to stop or slow down myopia progression, they found no definitive proof that any of the methods used up to that point were consistently effective. KEY POINTS: Extensive array of methods : many different approaches had been tried to control myopia progression, including glasses, contact lenses, medications, and lifestyle changes.

20. No conclusive evidence : despite the variety of methods, none had shown strong, consistent evidence of being effective in reliably controlling myopia progression.

21. SUMMARY OF ORTHOKERATOLOGY Orthokeratology is a proven technique for managing the mild to moderate myope. The development of advanced high Dk RGP lens designs and materials for the procedure has resulted in a better understanding of the orthokeratology process and has enabled the practitioner to employ a relatively predictable procedure based on corneal topography measurements and other clinical observations and measurements. Although there is only limited evidence that orthokeratology can retard myopia development in children, it is a technique that can be used to provide an alternative correction to spectacles, contact lenses, and refractive surgery in its various forms.

22. In the future, in addition to the myopia targeted currently, hyperopia (Reeder, 2005; Mitsui et al., 2005), astigmatism in selected cases ( Berke and Starfinger , 2005), high astigmatism (Baertschi, 2005), and presbyopia ( Calossi , 2005) may be the targets of successful future orthokeratology treatments. •Myopia control in children ??? For more details do visit my SlideShare “ MANAGEMENT OF MYOPIA ”.

23. THANK YOU