EXTENDED DEPTH OF FOCUS OPTICAL DEVICES
The ability to provide good vision at all distances, while minimising ghosting and haloes, is a defining characteristic of extended depth of focus (EDOF) optical devices, which presently includes contact lenses and intraocular lenses.
- Contact lenses to correct presbyopia
- Contact lenses for myopia management
- Intraocular lenses (IOLs)
- And is exploring other applications of this approach, including spectacles.
VISUAL PERFORMANCE COMPARISON
*The representation here of bifocal lens performance will hold true for tri- or multifocal contact lenses, except that the power of the lens will be concentrated at near, intermediate and distance. Disclaimer – the images and graphs above are for illustrative purposes only and are designed to represent the general characteristics of different lenses, not the exact nature of them.
CONTACT LENSES FOR PRESBYOPIA
Several factors can lead to variability in visual performance, which can occur at one or more distances including:
- Type of lens design (centre-near, centre-distance multifocal or concentric bifocal),
- amount of near add power
- pupil size
- rate of power change across the optical zone
- inherent spherical aberrations of the corrected eye
- contact lens centration on eye
Our extended depth-of-focus (EDOF) contact lenses, based on patented technology developed by Brien Holden Vision Institute, are designed to provide optimal visual performance from distance to near. The lenses:
- Use multiple higher order aberrations to optimise retinal image quality over a wide range of distances from far to near while minimising ghosting and haloes;
- Perform relatively independently of patients’ natural aberrations and variation in pupil size; and
- Are designed to meet the vision needs of emerging, moderate and advanced presbyopes.
- In published clinical studies these EDOF designs have compared very favourably over a range of measures with currently available multifocal lenses.1-5
CONTACT LENSES FOR MYOPIA
Our EDOF myopia management contact lenses are designed to result in a global retinal image quality (across both central and peripheral retina) that remains invariant for points on and in front of the retina and are degraded for points behind the retina to prevent further axial elongation.6
A shortcoming of current contact lenses and spectacles designed to slow the progression of myopia, is that they can result in compromised visual performance, leading to limited uptake of these lenses and compliance issues.
Subjective variables that may be affected include:
- Clarity of vision
- Ghosting for distance, intermediate, and near distances under day- and night-time conditions.
- Vision stability under day- and night-time conditions
- Driving vision under day- and night-time conditions
- Night-time haloes
- Ocular comfort
- Overall vision satisfaction
They provide good vision at all customary viewing distances, minimizing unwelcomed visual compromises like ghosting and haloes commonly associated with conventional simultaneous-image multifocal optical designs.
Visual performance with the EDOF myopia management contact lenses is designed to be relatively pupil neutral and relatively independent of the individual’s inherent ocular aberrations.
Our EDOF lenses have demonstrated improved visual performance over a range of the subjective variables listed above, compared to the traditional bifocal and multifocal alternatives.7 (Click images to enlarge)
These products are designed to provide an extended depth of focus (EDOF) range of clear vision, rather than discrete foci at prescribed intermediate and/or near points, as delivered by current bifocal and trifocal lenses. To achieve this EDOF effect, we have developed proprietary technologies, which allow the design of lenses with varying configurations of EDOF to suit differing patient needs.
Our EDOF patent portfolio covers two distinct design approaches to achieve the desired EDOF performance, collectively identified as:
- Higher order aberration (HOA) Manipulation – which involves deliberate and selective manipulation of HOAs to optimize the retinal image quality over a range of viewing distances.
- Phase-step – which uses phase modulation to create a stable through focus distribution of light by means of light interference.
We have generated optical designs which provide an EDOF effect over a
2.00D range with little variation in contrast throughout, and image quality equal to or better than the currently available multifocal IOLs’ in that correction range.
Brien Holden Model Eye System - a custom-designed research instrument
which replicates the parameters of a typical human eye
Optical prototypes have been made and tested them in the Model Eye System, demonstrating a through-focus vision performance which is truly extended depth of focus in nature, a feature that is not observed in commercially available IOLs.
FUTURE EDOF APPLICATIONS
2. Bakaraju RC, Tilia D, Sha J, Diec J, Chung J, Kho D, Delaney S, Munro A, Thomas V, Extended depth of focus contact lenses vs. two commercial multifocals: Part 2. Visual performance after 1 week of lens wear, In Journal of Optometry, 2017, ISSN 1888-4296, https://doi.org/10.1016/j.optom.2017.04.0
3. Sha J; Tilia D; Kho D; Diec J; Thomas V; Bakaraju RC. Comparison of Extended Depth-of-Focus Prototype Contact Lenses with the 1-Day ACUVUE MOIST MULTIFOCAL After One Week of Wear. Eye & Contact Lens: Science & Clinical Practice. Publish Ahead of Print: OCT 2017. DOI: 10.1097/ICL.0000000000000430
4. Tilia D, Bakaraju RC, Chung J, Sha J, Delaney S, Munro A, Thomas V, Ehrmann K and Holden BA, Short-Term Visual Performance of Novel Extended Depth-of-Focus Contact Lenses, Optometry and Vision Science. 93(6):656, June 2016.
6. Sankaridurg P, Bakaraju RC, Morgan J, et al. Novel contact lenses designed to slow progress of myopia: 12 month results. Poster presented at: Association for Research in Vision and Ophthalmology (ARVO); May 7–11, 2017; Baltimore, USA. Abstract 2391.
7. Sha J, Tilia D, Diec J, Fedtke C, Yeotikar N, Jong M, Thomas V and Bakaraju RC. Visual Performance of myopia control soft contact lenses in non-presbyopic myopes. Clinical Optometry, 2018:10, 75-86.