The Ultimate Guide to Different Bifocal Lenses
INTRODUCTION
Bifocal lenses as the name implies have two parts with optical powers to focus with, one for distance and the other for near work - is a design that has been a revolutionary solution for people with presbyopia, a condition that commonly arises with age and affects the eye's ability to focus on near objects.
This blog delves into the Nigerian perspective of bifocal lenses - the different types, their benefits, and reasons for issuing or choosing the type needed.
TYPES OF BIFOCALS
Traditional Bifocal Lenses : Traditional bifocal lenses are characterized by their distinct line that separates the near and distance vision zones. This line is visible and marks the boundary between the two prescriptions.
ADVANTAGES:
- Simplicity: Easy to use as they offer clear distinction between near and far vision.
- Cost-effective: Generally more affordable than other types of bifocal lenses.
- Wide availability: Widely available and can be made quickly by most opticians.
PITFALLS:
- Visible line: The visible line can be aesthetically displeasing and can be a source of distraction.
- Image jump: When the eye moves in between the two zones, there can be a noticeable "image jump," which some users find uncomfortable.
- Limited intermediate vision: Traditional bifocals do not address intermediate vision, which can be an issue for activities like computer work.
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Flat-Top Bifocal Lenses (D-Top)
Flat-top bifocals, also known as D-segment bifocals, have a D-shaped segment for near vision at the bottom of the lens. This segment is typically 28mm or 35mm wide. Optically considered the best fit for minus addition lenses that is where distant prescription is a minus power and the reading portion is a plus power.
ADVANTAGES:
- Less image jump: The flat top design reduces the image jump compared to traditional bifocals.
- Better aesthetics: The D-segment is less noticeable than a full-segment bifocal, providing a more subtle appearance.
- Functional for reading: Provides a wide field of view for reading or close-up tasks.
PITFALLS:
- Segment size limitation: The width of the D-segment can limit the reading area.
- Adjustment period: Some users may need time to adjust to the distinct transition between segments.
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Fused Bifocal Lenses (Round Top)
Round-segment bifocal lenses feature a round segment for near vision at the bottom of the lens. These segments are generally smaller, about 22mm in diameter.
ADVANTAGES
- Cosmetically appealing: The round segment is less noticeable and blends better with the rest of the lens.
- Less noticeable line: The curved line is less conspicuous than the line in traditional bifocals.
- Smooth transition: Provides a smoother visual transition between near and distance vision compared to flat-top bifocals.
PITFALLS:
- Smaller reading area: The small round segment provides a limited area for near vision tasks.
- Intermediate vision gap: Like other bifocals, they do not provide a solution for intermediate distances. -
Executive Bifocal Lenses
Executive bifocals, also known as Franklin bifocals, feature a full-width segment for near vision that extends across the entire bottom half of the lens.
ADVANTAGES:
- Wide near vision area: Provides a broad field of view for reading and close-up tasks.
- No image jump: The full-width segment eliminates the issue of image jump.
PITFALLS:
- Pronounced line: The line between the two segments is very visible and can be aesthetically unpleasing.
- Heavier lenses: These lenses can be heavier and thicker than other types of bifocals.
- Limited intermediate vision: Does not address intermediate vision needs.
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Blended Bifocal Lenses (INVISIBLE)
Blended bifocals, also known as seamless bifocals, have a blended transition between the near and distance vision zones, without a visible line.
ADVANTAGES:
- Aesthetically appealing: The lack of a visible line makes these lenses more cosmetically appealing.
- Comfort: The smooth transition can be more comfortable for the eyes.
- Reduced image jump: Blending reduces the abrupt change between segments.
PITFALLS:
- Blurriness: The blending can cause slight blurriness in the transition zone.
- Cost: Generally more expensive than traditional bifocals.
- Complex fitting: Requires precise fitting by an experienced optician like the team of specsmart optician. -
Degressive Lenses
This is not bifocal in the traditional sense but a derivative from progressive or freeform lenses which deserve mentioning as they provide a gradual transition between multiple focal points (larger intermediate, and near excluding or a reduced distance area).
Degressive lenses as known to be occupational bifocals are designed for specific tasks or professions. They are customized to meet the visual demands of particular activities, such as computer work, kitchen - culinary duties or crafting.
ADVANTAGES:
- Task-specific: Tailored to enhance vision for specific tasks, improving efficiency and comfort.
- Improved ergonomics: Can help reduce eye strain and improve posture by optimizing vision for work-related tasks.
- No lines: The seamless design is cosmetically appealing and eliminates the visible lines of bifocals.
- Versatility: Offers clear vision at all distances, including intermediate, making them ideal for near work and other tasks - tasks within arm length.
- Natural vision: Provides a more natural vision experience without abrupt changes.
PITFALLS:
- Adaptation period: Users often require time to adapt to the digressive change in prescription.
- Cost: Typically more expensive than bifocal lenses.
- Distortion: Peripheral distortion can occur, especially in the lower segments of the lens.
- Limited versatility: Not advised for general use as they are designed for specific tasks.
- Customization cost: The customization process can make them more expensive than standard bifocals.
UNIQUENESS OF BIFOCALS
From the above description of the various bifocal type, What do specsmart doctors or/and opticians consider before selecting the right bifocal lenses:
1. Lifestyle Needs: We evaluate your daily activities and specific visual needs. For instance, if you expend a significant amount of time on the computer, degressive or occupational bifocals might be more suitable.
2. Aesthetic Preference: For this purpose, the lenses to consider is blended bifocals or degressive lenses for their seamless design.
3. Comfort and Adaptation: Considering comfortability with change and whether you are willing to go through the adaptive phase, Degressive lenses is advised though versatile, require more adjustment time.
4. Budget: Bifocals are more affordable with varing prices, while degressive or occupational lenses can be more costly due to their advanced design and customization.
5. Optometrist’s Recommendation: Consult with optometrist at Specsmart Eye clinic to get professional advice based on your prescription and visual requirements. "They can assist you in exploring your choices and selecting the best lenses for your needs.
ACCOMPLISHMENT
Bifocal lenses over the years offer a practical solution for those dealing with presbyopia, enabling clear vision at multiple distances. The variety of bifocal lenses available today means that there is a suitable option for almost everyone, whether you prioritize aesthetics, functionality, or comfort.
By understanding the differences between traditional bifocals i.e flat-top, round-segment, executive, blended, and degressive lenses, as well as considering factors like lifestyle, budget, and professional advice which will help to make an informed decision enhancing your vision and quality of life. With advancement in technology, properties like photochromic ( Sun adaptive material) and anti glare (anti blue / blue ray/ blue blocker etc) have been factored into your lenses - bifocals alike.