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Soft lens orthokeratology

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Lawrence Kao
BOptom
Speciality lens practitioner and ArtMost Technical Consultant

 

It is not very common for a soft lens to be applied in today’s speciality contact lens clinic. A soft lens traditionally will transmit all the corneal astigmatism to its front surface, so it is generally believed that the applications of soft lenses in a practice are limited, and the practitioner will be likely to apply a toric soft lens fitting on a regular basis.

As Douthwaite has pointed out,1 most practitioners ordinarily consider the rigid gas permeable (RGP) as the lens of choice when fitting patients with special needs such as orthokeratology for myopia control or vision restoration for keratoconus. Ordinarily in these cases, the advantages of soft lenses, such as immediate comfort and shorter adaptation time, would be compromised due to the corneal astigmatism or irregularity.2

Flexure of the lens

The team at ArtMost Oceania has proven that it can make a soft lens function like a rigid lens with a tear reservoir layer underneath the contact lens, which still retains the comfort of a soft lens. Some small corneal irregularity, such as early keratoconus or corneal astigmatism can also be corrected by this new soft lens design.

The map

The next task was to simulate the rigid lens design or the treatment zone of orthokeratology with a soft lens. Traditionally defined, orthokeratology is a technology that reshapes the cornea by applying a designed reverse geometry RGP overnight.2

The efficacy of orthokeratology in the treatment of myopia control is well known.3,4 The key for myopia control by orthokeratology could be the combination of the peripheral inward focus effect from the treated cornea on the retina,5 time course of the effects of orthokeratology on peripheral refraction, and corneal topography. Other research has also shown that there is less effect of myopia control on the single vision soft lens.6

Nevertheless, not all myopic patients are suitable for orthokeratology treatment due to rigid lens adaptation problems.2 It is then valuable to be able to ‘simulate’ the orthokeratology treated corneal contour with a soft lens for the purpose of myopia control.

CASE REPORT

A 50-year-old patient visited our practice. She had been diagnosed recently with borderline keratoconus by her ophthalmologist and was referred for a speciality contact lens fitting (Figure 1), a small corneal ectasia can be seen at the six o’clock location in both OD and OS.

069 Figure 1

Figure 1. Corneal topography result without contact lens fitting. Topography courtesy Dr Arthur Tung

Subjective refraction OD: -18.00/-1.25 x 85 20/25, OS: -18.75/-0.75 x 100 20/25

After fitting the ArtMost Flexlens SEC, the new refractive surface became more spherical (Figure 2). Note the lenses also provide steeper reading power as the multifocal soft lens or ortho-K multifocal visual effect. Final corrected distance visual acuity can reach 6/6 for both OD and OS, while Near VA with the contact lens can read J3~J5 binocularly.

069 Figure 2

Figure 2. Corneal topography result with contact lens fitting. Topography courtesy Dr Arthur Tung

Conclusion

Through special lens-flexure-controlled technology, the ArtMost Flexlens can simulate RGP optical properties for the eye. There are various applications for the ArtMost Flexlens, including simulating rigid lens for managing early or small corneal irregularity conditions, or simulating ortho-K treatment for myopia control.

  1. Douthwaite W. Contact Lens Optics and Lens Design. Bradford: Elsevier Butterworth Heinemann; 2006.
  2. Hom M, Bruce A. Manual of Contact Lens Prescribing and Fitting. Missouri: Elsevier Butterworth Heinemann, 2006.
  3. Cho P, Cheung S-W. Retardation of Myopia in Orthokeratology (ROMIO) Study: a 2-year randomized clinical trial. Invest Oph Vis Sci 2012; 53: 11: 7077-7085.
  4. Kang P, Swarbrick H. Time course of the effects of orthokeratology on peripheral refraction and corneal topography. Oph Physiol Optics 2013; 33: 277-282.
  5. Kang P, Fan Y, Oh K, Trac K, Zhang F, Swarbrick H. Effect of single vision soft contact lenses on peripheral refraction. Optom Vis Sci 2012; 89: 7: 1014-1021.


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