Multifocal lenses for presbyopia in eyes with previous corneal surgery

The use of scleral contact lenses has grown significantly in the past year, with an associated exponential increase in research.¹ This type of lens can be classified as corneo-scleral or fully scleral depending on the presence or absence of corneal bearing.²

One of the main advantages of this option for refractive correction is that the tear reservoir between the posterior surface of the contact lens and the anterior corneal surface allows a significant neutralisation of anterior corneal aberrations, which are relevant considering the contribution of this optical surface to the total power of the eye.²

As these lenses are fitted with minimal or no corneal bear, the fitting process can be simplified in patients with highly irregular anterior corneal profiles.³ For this reason, the use of these contact lenses has been intensively investigated for the correction of irregular astigmatism in post-corneal refractive surgery^4,5 and post-keratoplasty corneas⁶ as well as in ectatic corneal disorders.^7,8

Although there is a consensus among practitioners with more than 5 years of scleral lens experience about most of the aspects of contact lens management,⁹ there are some factors that require more research, such as the management of multifocality for presbyopia correction. To date, only the outcomes of conventional soft or rigid gas-permeable corneal contact lenses have been evaluated,^10,11 despite the availability of some multifocal scleral lens designs.

Recently, a new model of multifocal corneo-scleral contact lens has been commercially released by Laboratorios Lenticon S.A., Presbycustom, providing the option of customising not only the fitting parameters to adjust the lens over the cornea and sclera, but also the type of multifocality induced. We report here the results obtained with this new modality of multifocal scleral contact lens in eyes with previous refractive surgery and significant high-order corneal aberrations.

Contact lens design

The Presbycustom contact lens (paflufocon D, Dk 100 Fatt units) is the result of a proof-of-concept research project developed by Laboratorios Lenticon SA in collaboration with the Group of Optics and Visual Perception of the University of Alicante.¹² It is a corneo-scleral contact lens made of highly gas-permeable material.

The lens is customised according to the anterior corneal geometry, the level of ocular high-order aberrations and the peculiarities of pupil dynamics. It comprises three different areas: corneal, limbar and scleral (Figure 1).

The corneal area has a variable diameter with fixed back surface asphericity and central anterior surface asphericity that is modified according to the aberrometric induction required. Specifically, the depth of focus achieved with the contact lens is set by customising the induction of primary and secondary spherical aberration. It has been demonstrated that combining primary and secondary spherical aberrations of opposite sign is significantly more effective for expanding the depth of focus than other aberrometric options.^13,14

The scleral area of the contact lens allows a smooth bearing over the sclero-conjunctival surface, facilitating comfortable wearing (Figure 2). The distribution of the tear film below the different areas of the contact lens generates a characteristic fluorogram consisting of central tear pooling with paracentral alignment and significant edge clearing (Figure 3).

(Figure 2) Optical coherence tomography image of an eye fitted with the Presbycustom scleral lens, showing how the lens rests over the conjunctival surface.

(Figure 3) Characteristic fluorogram of the scleral multifocal contact lens, consisting of a central tear pooling, with a paracentral alignment and significant edge clearing.

Preliminary clinical experience

We recently conducted a prospective pilot study in the Department of Ophthalmology of the Vithas Medimar International Hospital (Alicante, Spain) and the Optometry Clinic of the University of Alicante including eight eyes of eight patients (aged 45 to 56 years) with previous LASIK surgery requiring presbyopia correction. All cases had reduced corrected distance visual acuity (CDVA) and significant corneal irregularity.

A complete ocular examination was performed before and 1 month after fitting the customised multifocal scleral contract lens, including visual and refractive analysis, corneal topography, pachymetry and evaluation of corneal and ocular aberrations with the VX120 multidiagnostic system (Luneau Technologies). The contact lens was customised according to the anterior corneal geometry, the level of ocular high order aberrations and the pupil diameter.

The mean corneal radius of the lens fitted was 8.06 ± 0.47 mm; the mean scleral radius was 7.68 ± 0.20 mm. The mean central eccentricity used for the lenses was 0.44 ± 0.33, whereas a fixed posterior eccentricity of 0.63 was used in all contact lenses fitted.

Mean monocular logMAR CDVA changed from 0.21 ± 0.08 with spectacles before fitting to 0.08 ± 0.08 with contact lens fitted (P = 0.04). Mean logMAR binocular distance and near visual acuity values with the contact lens were 0.02 ± 0.03 and 0.14 ± 0.11. Mean logMAR-corrected visual acuities for defocus levels of –0.50, –1.00, –1.50, –2.00 and –2.50 D were 0.03 ± 0.06, 0.08 ± 0.08, 0.19 ± 0.17, 0.24 ± 0.10 and 0.31 ± 0.12, respectively (Figure 4).

All patients reported spectacle independence for reading and high levels of contact lens tolerance and satisfaction. No complications were reported during the first year of follow-up.

Conclusions

The selection of an appropriate combination of primary and secondary spherical aberration of opposite sign according to the aberrometric status of the eye can be useful to optimise the depth of focus required for presbyopia correction. This approach can be used to correct presbyopia in irregular corneas with a scleral contact lens.

This pilot study shows that complete visual rehabilitation can be achieved with a customised multifocal scleral lens in presbyopic eyes with previous unsuccessful corneal refractive surgery. These preliminary results should be corroborated in the long term as well as in a larger population.

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David P. Piñero, PhD
E: david.pinyero@ua.es

Dr Piñero is based in the Department of Optics, Pharmacology and Anatomy, University of Alicante, Spain. He has no proprietary or commercial interest in the device described. This research was co-funded by Laboratorios Lenticon S.A. and the University of Alicante within the proof of concept project PC15-02 “Diseño de lente de contacto escleral multifocal personalizada (Presbycustom).” Dr Piñero is also supported by the Ministry of Economy, Industry and Competitiveness of Spain within the programme Ramón y Cajal, RYC-2016-20471.

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