Global-Ok Vision

Ortho-K

GOV® Series Ortho-K Lenses

Chief designer and Ophthalmologist, Dr Arthur Tung, has dedicated his time to the ever growing problem of myopia worldwide with specific reference to Orthokeratology and visual training.    He holds a number of world patents for orthokeratology designs including the Excessive myopia (XM)-, Hyperopic (H)-, Hyperopic multifocal (HP2)-, Myopic multifocal (MP2)-, Post Lasik (PL)- and Keratoconic (KC) Orthokeratology lens designs.

GOV® MP lenses

More Details

The GOV® MP lens, incorporating couple of US patented designs, namely XM design (US #:6,543,897), Dual geometric (DG) design (US#: 6,652,095, US#: 7,070,275) and the concept of conformation skills (US#: 6,997,553), is designed to shape out a multifocal corneal zone and achieve concentric simultaneous vision, for myopic presbyopia correction. The lens is good up to -10.00 myopia with an Add of +1.00~+3.00. For myopia up to –5.12 D, the lens is designed for reshaping the corneas central for near. For myopia over –5.13, reshaping the peripheral ADD is the target to help achieving better far vision. The aspheric back optical zone radius, or BOZR of a GOV® MP lens can be steeper, same to or flatter than the measured central cornea curvature, with a combination for myopia reduction (flatter) and central ADD (steeper), as well as over target of myopia for +1.25, to ensure sufficient reduction of myopia and presbyopia.

The central-near myopic progressive molding is accomplished by forming a protrusion center in an ablation-like base. The reshaping would not be available if based upon the central outward theory already known for myopia Ortho-K. The ‘peripheral inward’ theory as proposed for molding high myopia can explain how it is possible to create a protrusion button in an ablation-like base for central-near myopic progressive molding. An aspheric alignment curve and precisely determined lens size ensure proper centration of the lens and is critical for myopic multifocal molding.

  • The front surface of an MP lens is figured to enhance the ADD effect of the aspheric BOZR for better near vision with the lens on. That is to say, MP lens, with full ADD on peripheral portion of the lens, can be functioning as multi-focal RGP.
  • Like reverse geometric lenses for myopia Ortho-K, dual geometric MP lenses are likely to seal off if wearing it during awakening hours.
  • The MP lens will reshape the central cornea steepest for a reading button. Just like the central-near multi-focal soft contact lenses, the wearers may experience more or less interference with the far vision especially in nighttime, which should be properly warned for all drivers.

GOV® H & HP lenses

More Details

The GOV® H & HP lenses, incorporating the US patented Dual geometric (DG) design (US#:6,652,095 & #7,070,275) to enhance the peripheral flattening and highlight the central steepening, is fabulous for hyperopia & presbyopia correction. The H lens is good up to +6.00 hyperopia. Higher hyperopia could be tried up to +10. The back optical zone radius, or BOZR of a GOV® H lens is designed steeper than the central cornea curvature, by +0.25 to +6.00 D (or hyperopia target power), plus an over target of -0.75 D to ensure sufficient reduction. The optical zone is set aspheric for faster molding. An aspheric alignment curve ensures proper centration of the lens.

The HP lens is good from plano to +6.00 (or hyperopia target power) with an Add of +0.50~+3.00. Higher hyperopia & presbyopia could be tried up to +10 with and ADD up to +5.00. The back optical zone radius, or BOZR of a GOV® HP lens is designed steeper than the central corneal curvature for the targeted far power as well as the ADD but not any over target. The optical zone is set aspheric for molding faster with precision control for achieving central-near simultaneous vision.

The dual geometric H & HP lenses may exert a positive force on mid-peripheral portion of the cornea to form a flat mid-peripheral ring for highlighting the central steepening, which is much more effective than exerting negative force over the corneal apex for traditional molding. The DG design ensures a wide & precisely formed far zone to be a base for progressive presbyopia molding. The fluorescein pattern for DG lens is similar to a bull’s eye for Myopic Ortho-K except the obvious central pooling. The force exerted by the flat (secondary) plateau zone is the key for precision control of the hyperopia molding, which ensures a wide far zone for protrusion of the reading button by HP design.

An aspheric alignment curve and precisely determined lens size ensure proper centration of the lens, which is critical for HP progressive molding.

  • Both H and HP lens, the back surfaces of optical zone (BOZR) are aspheric.
    Whereas the front surfaces are created differently:
    a. The front surface of an H lens is figured to neutralize the ADD effect of the aspheric BOZR for better far vision with the lens.
    b. The front surface of an HP lens is figured to enhance the ADD effect of the aspheric BOZR for better near vision with the lens. That is to say, HP lens, with full ADD on peripheral portion of the lens, can be used as multi-focal RGP for far and near.
  • Unlike reverse geometric lenses for myopia Ortho-K, dual geometric H and HP lenses are less likely to seal off wearing it during awakening hours. It would be safer, when better vision is required, to wear the H or HP lenses for awakening hours such as driving at night. Practitioners still have to monitor the lens movement for the initial 6-8 hours to determine whether daywear schedule is allowable.
  • The HP lens will reshape the central cornea steeper for a reading button. Just like the central-near multi-focal soft contact lenses, the wearers may experience more or less interference with the far vision especially in nighttime, which should be properly warned for all drivers.

GOV® XMJ lens

More Details

The GOV® XMJ lens, incorporating the US patented design (US #6,543,897 &#: 6,652,095) to enhance the peripheral steepening, and an aspheric alignment zone to ensure better centration, is your best choice for managing myopia up to –5.00. The back optical zone radius, or BOZR of a GOV® XMJ lens is designed flatter than the central cornea curvature, by 1.50 to 5.00 D, plus an over target of +1.25 D to ensure sufficient reduction. It is required to lower down the over target for very low myopia of less than -1.00 to prevent from over-treated hyperopia.

GOV® XM lens

More Details

The GOV® XM lens, incorporating the US patented design (US #6,543,897 &#: 6,652,095) to enhance the peripheral molding, and an aspheric alignment zone to ensure better centration, is your best choice for managing myopia –5.25 ~ -10.00. Higher myopia could be tried up to –15.00 but should monitor the cornea response more closely. The back optical zone radius, or BOZR of a GOV® XM lens is designed flatter than the central cornea curvature, by the target amount, plus an over target of +1.75 ~ +2.00 D to ensure sufficient reduction.

GOV® M4

The double reverse geometric GOV® M4 lens, inforporating an aspheric alignment zone to ensure better centration, is your best choice to start fitting myopia Ortho-K up to -5.00. The back optical zone radius, or BOZR of a GOV® M4 lens is designed flatter than the central cornea curvature, by 1.50 to 5.00 D, plus an over target of +1.25 D to ensure sufficient reduction. M4 lenses are configured precisely to match cornea sagittal depth and also systemized for simple use. The inventory system makes it so simple to fit Ortho-K lenses just like regular RGP fitting. Even fitted empirically, by KM and refraction, it satisfies 80-90% of the regular cases. A compact 50 lenses inventory further makes dispensing same day possible.