To Infinity and Presbyond: A Revolutionary Approach to Presbyopia Management

When considering treatment options for presbyopia, several key criteria must be met for optimal outcomes. The ideal treatment should:

• Provide clear vision at near, intermediate, and distance ranges,
• Maintain excellent optical quality by preserving contrast sensitivity and nighttime vision,
• Preserve binocularity,
• Demonstrate high patient tolerance,
• Enable quick adaptation and return to normal activities,
• Simultaneously correct any refractive errors, and
• Offer reversibility if needed.

Currently, the most widely performed surgery for presbyopia worldwide is refractive lens exchange with the implantation of a diffractive multifocal intraocular lens (IOL).^2-5 While lens extraction surgery is considered one of the safest operations in medicine,^5,6 it remains an invasive procedure that carries risks of severe intraocular complications, including endophthalmitis, retinal detachments, and potential blindness.^6,7 It’s worth noting that multifocal IOL implantation for presbyopia management is technically performed off-label, as these lenses are registered for cataract surgery rather than presbyopia treatment.²

Moreover, the implantation of a diffractive lens presents its own challenges. The human brain has not evolved to fully adapt to diffractive optics. Glare and haloes associated with these lenses never go away, despite patients being counselled that they will “get used to it”. This limitation often leads to lens exchange surgery when patients cannot adapt to the severe nighttime dysphotopsia of glare and haloes associated with diffractive IOLs.

Introducing Presbyond: A Sophisticated Solution

To differentiate my practice and address these challenges, I introduced Presbyond laser blended vision from ZEISS Meditec to Perth, after spending a significant amount of time training under its inventor, Professor Dan Reinstein. Presbyond represents a highly sophisticated treatment option for presbyopia that avoids the drawbacks of traditional surgical approaches.

Presbyond is a proprietary software developed by ZEISS Meditec for planning a customised binocular laser assisted in situ keratomileusis (LASIK) procedure that simultaneously manages presbyopia and corrects refractive error. The technology works by increasing the depth of field through controlled spherical aberration induction and creating a micro-anisometropia (≤1.5D). The procedure is performed using standard LASIK techniques.

Studies have shown that up to 97% of presbyopic patients can tolerate micro-anisometropia.6,8,9 What sets Presbyond apart is its ability to provide patients with a continuous range of quality vision from near to far, combining the accuracy of laser refractive procedures while avoiding common drawbacks like glare and haloes at nighttime. Importantly, patients treated with Presbyond maintain both stereoacuity and contrast sensitivity post-treatment.

Advanced Diagnostics

The sophistication of Presbyond treatment demands the most advanced diagnostic equipment for keratorefractive surgery. This led me to invest in two key pieces of technology: the CSO MS-39 anterior segment optical coherence tomography (OCT) with topographer, and the Osiris topographer and ocular aberrometer.

The MS-39: Comprehensive Corneal Analysis

The MS-39 combines anterior OCT with Placido disk corneal topography to generate high-resolution, detailed reports (Figures 1, 2).

Its capabilities include:

• Epithelial thickness and point spread function mapping,
• Early detection of corneal abnormalities through epithelial mapping and Gaussian reports,
• Built-in IOL calculations based on ray-tracing,
• LASIK flap thickness mapping,
• Detailed topography of both anterior and posterior cornea, and
• Keratoconus analysis function with Gaussian analysis.

The device’s ability to detect subclinical keratoconus through epithelial mapping is particularly valuable. Areas of epithelial thinning corresponding with increased elevation and tangential steepening are pathognomonic of early keratoconus.6-8 The MS-39 can also assess previous keratorefractive surgery cases where uncertainty exists.

The Osiris: Advanced Aberrometry

The Osiris complements the MS-39 by providing detailed corneal topography and higher-order aberration measurements across both the cornea and the whole eye (Figure 3). Its simulation maps facilitate patient education on complex visual problems. We combine the diagnostic output from both the MS-39 and Osiris T to not only assess the suitability of a patient to undergo Presbyond LASIK but also to give both a corneal and whole aberration profile that will be used by the Presbyond software to work out a bespoke plan for a patient.

Figure 1. Example of the MS-39 topography.

Figure 2. An example of an MS-39 corneal aberration profile.

Figure 3. Example of the Osiris T aberration profile printout with whole eye, corneal, and lenticular aberrations.

Understanding Spherical Aberrations in Presbyond

As Prebyond laser blended vision uses natural spherical aberrations, it is imperative to analyse and know what the corneal and whole eye aberration profile of the eye is. The Osiris T measures both whole eye and corneal Zernike higher order aberration profiles. The most important aberration is the Z(4,0) spherical aberration.

In most individuals, the cornea has positive spherical aberrations, which are counteracted by the negative spherical aberrations in the crystalline lens. To accurately perform Presbyond, the whole aberration profile is input in the software. This includes the aberration profile of the crystalline lens, which can counteract the induced spherical aberrations in myopic ablations or create toxic aberrations in hyperopic corrections. The human brain has evolved to filter spherical aberrations of up to either +0.6 µm or -0.6 µm, without affecting the quality of the image.^8-10

The Presbyond Advantage: How It Works

Presbyond combines two key elements to achieve its results:

1. Enhanced depth of field through controlled spherical aberrations, and
2. Micro-anisometropia in the non-dominant eye.

The software induces spherical aberrations within tolerable ranges (less than ±0.6 µm) to enhance the depth of field by 1.5 diopters. As this alone isn’t sufficient for complete near to distance vision, a mild anisometropia is induced in the non-dominant eye, typically +0.75 to +1.5 diopters depending on the age of the patient and residual accommodative amplitude. In most cases the standard +1.5 diopters anisometropia in the non-dominant eye is sufficient,^11-15 but as a rule we actively measure the residual accommodative amplitude of each patient to ensure a bespoke treatment that will be easy for a patient to adapt to.

Traditional monovision approaches using contact lenses or monofocal IOLs face several challenges including:

• Limited patient tolerance – not everyone can tolerate an anisometropia sufficient to offer reading and distance vision,
• Low patient satisfaction in many cases due to the compromises associated with monovision,
• Difficulty in accepting the near/distance vision discrepancy, summation, and loss of intermediate, especially where intermediate vision is essential for tablet and computer use, and
• Severely compromised depth perception in monovision.^16-21

Presbyond overcomes these limitations by combining a micro-anisometropia with extended depth of focus induced by spherical aberrations to facilitate sharp, binocular vision from near over intermediate to far without compromising quality of vision. This solution achieves a 97% tolerance rate among presbyopic patients.^6-8,19 The induced spherical aberrations remain at non-toxic levels, allowing the brain to filter them without compromising visual performance or contrast sensitivity.

The Blend Zone Advantage

Unlike standard monovision, which can create ‘blur zones’ requiring additional correction for intermediate tasks (Figure 4), Presbyond creates a ‘blend zone’ enabling crisp, continuous vision from near to far (Figure 5). The dominant eye maintains primary distance vision while gaining some near capability through enhanced spherical aberrations. Conversely, the non-dominant eye focusses primarily on near vision while retaining some distance capability.

This blend zone allows the brain to effectively fuse images from both eyes, maintaining binocularity. Non-dominant eyes targeted for -1.5D often achieve 6/7.5 or 6/9 unaided vision due to the enhanced depth of field, while dominant eyes can typically read N6 when aimed at emmetropia.^6-8,19

Figure 4. In monovision there is a ‘blur-zone’ where a patient will still require glasses to see because the depth of field is not enhanced to cover that specific area of vision.

Figure 5. Anisometropia is induced in the non-dominant eye and there is an overlap of vision known as the ‘blend zone’.

References

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