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Product Introduction
Optical Convergence: The Reliability and Stability of Flat Top 28 Bifocals
Despite the rise of progressive technology, the Flat Top 28 Bifocal remains one of the most trusted and functional solutions for presbyopia correction. Its enduring popularity stems from its absolute visual stability and clearly defined fields of view. The lens features a 28mm-wide semi-circular segment (often called a "D-segment") for near-vision tasks, while the rest of the lens is dedicated to distance correction. The "Flat Top" design is engineered to minimize "Image Jump"—the sudden displacement of an object as the gaze moves from the distance zone into the reading segment. By placing the optical center of the reading segment close to its top edge, we ensure a smoother transition for the wearer's eye. The 28mm width is widely considered the "gold standard" because it provides a sufficiently wide reading area to scan a line of text without moving the head, unlike many entry-level progressives. Our Flat Top 28s are manufactured using high-precision liquid casting, ensuring the segment line is crisp and the power transition is accurate. This lens is particularly favored by elderly patients, craftsmen, and users who find the peripheral blur of progressive lenses intolerable. With a high Abbe value and excellent contrast, the Flat Top 28 offers a straightforward, "no-nonsense" approach to multifocal vision that delivers consistent, reliable performance in all lighting conditions.
Specification
| Segment Type | Flat Top (D-Shape) 28mm Wide |
| Construction | Casted / Fused Segment |
| Refractive Index | 1.499, 1.56, 1.61 |
| Add Power Range | +1.00 to +3.50 Diopters |
Technological Highlights: Premium Monomers and Coating Integrity
- High-Purity Monomer Selection: We exclusively use high-performance monomers (e.g., MR-series) to achieve superior tensile strength and optical purity, resulting in excellent clarity and minimal risk of yellowing over time.
- Precision Liquid Casting Process: The lenses are produced via a controlled liquid casting method that ensures uniform material density and refractive index consistency across the entire blank, which is critical for accurate therapeutic power zones.
- Advanced Vacuum Multi-Coating (SHMC): Coatings are applied in a high-vacuum chamber, using multiple layers of metallic oxides to create a durable, anti-reflective stack. This process guarantees maximum light transmission and minimal glare.
- Thermal Curing Optimization: A slow and precise thermal curing cycle is employed to maximize the material’s resistance to internal stress, ensuring the finished lens remains stable and optically perfect under varying temperature conditions.
- Integrated Peripheral Defocus Geometry: The therapeutic design is engineered into the mold itself for cast lenses, or applied via digital surfacing for semi-finished blanks, guaranteeing the accuracy and consistency of the myopia control zone geometry.
Application
- Users requiring a wide, stable reading field
- Patients who cannot adapt to progressive lenses
- Occupations requiring precise, static near vision (e.g. watchmaking)
- Cost-conscious patients seeking durable multifocal optics
Advantage
- Zero peripheral distortion compared to progressives
- Large, stable reading zone for effortless text scanning
- Low image jump during vertical gaze transitions
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Customization
Customized For Your
Business
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Complete Customization Capability
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Professional Lens Architecture
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Functional Coating Customization
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Digital Rx Customization
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Branding & Packaging
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Delivery & Support
Frequently Asked Questions (FAQ)
- Q: Why choose Flat Top over Progressive?
- A: For a wider, distortion-free reading area and better stability.
- Q: Is the line visible?
- A: Yes, the segment line is visible to others and the wearer.
- Q: Does it have a "jump" when I look down?
- A: The Flat Top design significantly reduces this jump compared to Round Top bifocals.
- Q: Are they available in 1.61 High Index?
- A: Yes, we offer them in 1.61 for a thinner, lighter profile.
- Q: Can I add an Anti-Reflective coating?
- A: Yes, SHMC is highly recommended to improve light transmission.
- Q: Are they suitable for computers?
- A: They work for reading, but the "intermediate" computer distance may be a challenge.
- Q: Is there an adaptation period?
- A: It is usually very quick, as there is no peripheral distortion.
- Q: Can these be made as sunglasses?
- A: Yes, they are available in tinted or photochromic versions.
- Q: What is the most popular segment size?
- A: 28mm is the industry standard for the best balance of vision.
- Q: Are they durable?
- A: Very; our resin material is highly scratch-resistant with proper coating.
Payment and Shipping Policy
- Payment: T/T, L/C, or Credit Line for established distributors.
- Shipping: Standard Air Express (UPS/DHL) for RX orders; Sea Freight for bulk.
- Packaging: Premium individual envelopes with detailed digital maps.
- Lead Time: 15-20 days for precise digital surfacing and coating.
Comprehensive Business Information
| MOQ | 100 Pairs (Stock Blanks) |
| Lead Time | 15-20 Days |
| Packaging | Reinforced moisture-proof export cartons. |
| Certifications | FDA, CE, ISO9001. |
| Raw Materials | Optical Grade Resin. |
| Customization | Available in clear, photochromic, and blue-cut. |
