Designed and manufactured in Japan for people with mild-to-moderate myopia, Menicon Alpha Ortho-k is a highly oxygen-permeable hard contact lens. It is specially designed to effectively and safely correct myopia by flattening the anterior surface of the cornea when the lens is worn during sleep. This innovative method of myopia correction allows an individual to be free of lenses during the day.
Consisting of four zone-five curves, Alpha Ortho-k offers flexibility for practitioners to adjust the lens parameters, including the back optic zone diameter, to enhance myopia correction effects. This is especially useful for patients who suffer from glare and halo.
Lens Design
ALPHA ORTHO-K / ALPHA ORTHO-K AC-TORIC is a specialty lens composed of four or five curves. ALPHA ORTHO-K AC-TORIC is a design that allows a good fitting to be obtained even for wearers with corneal astigmatism.
Base Curve (BC)
This is the area where the anterior corneal surface is pressed in and flattened in accordance with the patient’s target power (target correction value). The fluorescein pattern in this area appears as a darker shade, indicating minimal clearance of the tear fluid layer.
Reverse Curve (RC)
This area connects the base curve (BC) to the alignment curves (AC) to redistribute the corneal epithelial cells. The fluorescein pattern appears as a yellowish-green ring due to the pooling of tear fluid.
Alignment Curves (AC1, AC2)
The role of these curves is to maintain the centering of the lens and to ensuring adequate refractive error correction. ALPHA ORTHO-K is designed to provide stable centering with two-step alignment curves (AC) when the lens diameter exceeds a certain size. Because these curves support the lens on the cornea, the fluorescein pattern appears as a darker shade.
Peripheral Curve (PC)
This area facilitates tear fluid exchange and makes it easier to remove the lens. The moderate edge lift produces a yellowish-green fluorescein pattern.
Fluorescein Pattern
The figure at right shows the fluorescein pattern produced when a well-fitted ALPHA ORTHO-K lens is worn. When lenses are prescribed, we check the patient’s fluorescein pattern to determine if the fitting is good. The yellowish-green ring shape is a distinctive characteristic.
Lens technology (AC-TORIC design)
The feature of “AC-Toric Design” is that only the alignment curve (AC) has an aspheric shape.
By making the alignment curve aspherical, the stability on the cornea has been improved, and it has become easier to prescribe for patients with severe corneal astigmatism, which was difficult to prescribe in the past.
Fluorescein pattern of AC-TORIC design
The fluorescein pattern of AC-TORIC design is characterized by slight thickening in the vertical direction in a doughnut shape.
Although the thickness of the pattern is not uniform, appropriate fitting will be achieved if the lens is located in the center.
Corneal astigmatism
AC-TORIC design may be prescribed to a patient with corneal astigmatism. We strongly suggest that the lens is tested on a patient who has previously experienced difficulty receiving a prescription for a contact lens owing to corneal astigmatism, although there are differences among individuals.
Case study: Improvements by centering
In this case, lateral de-centering was confirmed while using the STANDARD design. When the patient changed to AC-TORIC design because a de-centering was found by the topography (left figure). poor centering was improved (right figure).
* AC-TORIC design is for myopia correction. It is not intended for the correction of astigmatism.
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