Presbyopia – What can we offer our phakic patients?

In our attempts to develop a satisfactory surgical treatment for presbyopia, we still are debating accommodative mechanisms more than 300 years after Descartes first postulated that accommodation is associated with a change in the shape of the crystalline lens.

Presbyopia—the progressive loss of accommodative amplitudes—functionally disables more than half of the American population. More than half of presbyopes correct their visual dysfunction with glasses or contact lenses. No surgical device is approved yet by the United States Food and Drug administration for the correction of presbyopia.

Improvements in imaging technologies –such as high resolution magnetic resonance imaging, ultrasound biomicroscopy, Scheimpflug photography and optical coherence tomography – are enabling us to analyse anatomic variability with and without accommodative stimuli in all age groups. Advances in optical techniques—such as automated dynamic retinoscopy, infrared optometry, photorefraction and dynamic aberrometry-are allowing us to measure the dynamics of accommodation.

In patients undergoing laser refractive surgery, the most commonly used approach to obviate or delay the need for reading glasses is binocular pseudoaccommodation. Previous monovision contact lens wearers are the best candidates but should understand and willingly accept the fact that they will lose the ability to alter the prescription in the near vision cornea on a yearly basis.

If a patient is undergoing conductive keratoplasty for hyperopia and desires monovision, it should be explained that the yearly moving target might be even greater because of wound healing in addition to the progressive loss of accommodation. We still do not know the corneal endothelial safety of multiple conductive keratoplasty retreatments.
The majority of motivated presbyopes in their 40s and 50s who require up to about 1.25 D of add tolerate monovision with PRK, LASEK or LASIK with minimal compromise of stereoacuity. The dominant eye should be corrected for distance unless the patient has been using it for near with contact lens monovision.

Monocular pseudoaccommodation is another approach that can satisfy some patients. Corneal multifocality has long been noted to provide some presbyopic refractive and corneal graft patients with better than expected near vision. Although multifocal laser vision correction has been performed for many years after the initial treatments by Till Anschutz MD, loss of contrast sensitivity and poor visual outcome precluded its use by many surgeons.

The current use of ablation profiles with negative asphericity is improving the quality of vision after multifocal LVC or presbyLASIK, but the procedure decreases the add requirements by only about 1 D and is successful primarily in hyperopes. Patients with pupils smaller than 2 mm do not achieve good near vision. Patients with large pupils can develop monocular diplopia.

Insertion of an intracorneal inlay under a flap to achieve corneal multifocality is under clinical investigation but unresolved issues related to corneal metabolism, wound healing, inlay opacification, and inaccurate or unstable positioning need to be resolved.
Both the mechanism theories and the results associated with scleral surgery for the correction of presbyopia remain controversial. Most clinical and experimental data reinforce Helmholtz’s lenticular theory describing ciliary muscle contraction releasing zonular tension during accommodation.

Accordingly, scleral procedures may temporarily but unpredictably facilitate ciliary muscle activity—only if lens elasticity is adequate. Both ciliary muscle tension change and lenticular pseudoaccommodation have been suggested to account for the variable results and lack of longterm stability and efficacy with scleral expansion surgery.

Although more precise depth placement has been proposed to improve initial results, scleral procedures have generally been abandoned, even by early proponents. In the 2002 survey of French ophthalmologists described in last month’s EuroTimes, Dr Richard Gold reported that scleral expansion techniques, which were used by about 2 % of respondents in 1999, were no longer practised by any of the respondents in 2002.

The risk of serious complications, such as anterior segment ischaemia reported by Hamilton, Davidorf and Maloney, as well as the loss of effect from wound healing responses, remain problematic in any consideration of mechanical or laser anterior ciliary sclerotomy.

We still face a great challenge in simultaneously correcting ametropia and presbyopia in phakic refractive surgical patients. We need to develop new surgical approaches for correcting presbyopia before replacing glasses and contact lenses in the majority of our patients.


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