Today’s PracTice refracTive fundamenTals

T he eye’s ability to accommodate is progressively lost with age, which is why this phenomenon is called presbyopia (from the Greek words présbys, meaning old, and ōps, meaning eyes). The condition can be treated with corrective lenses, a method that has been widely used for a long time; however, this approach may not be the most comfortable treatment option for the patient. Today, patients have increasing expectations regarding ophthalmic treatments, often hoping to achieve good uncorrected near, intermediate, and distance visual acuity and therefore be made completely independent from glasses. In recent years, a major challenge for ophthalmology has been the restoration of near vision in patients with presbyopia. Presbyopia correction methods can be divided into accommodative and nonaccommodative; reversible and irreversible; and corneal, scleral, and lens-based surgical corrections. When presbyopia is accompanied by an early cataract, patients who desire presbyopic correction are often referred for cataract rather than corneal surgery. When the lens is clear (ie, without sign of cataract formation), the surgery performed in this situation is called refractive lens exchange. Current surgical techniques for presbyopia correction are based on three principal approaches. The first is to achieve monovision, meaning to create acquired anisometropia, with one eye corrected for distance vision and the other for near. The second approach is to increase functional ocular depth of focus by creating simultaneous multifocality, thus achieving satisfactory distance and near vision. The third approach is to surgically achieve real changes in accommodation, or changes in ocular lens power. Surgical methods of monovision and multifocality can be achieved with corneal or intraocular procedures. Corneal methods are more suitable for young presbyopes, aged 40 to 50 years, and those without cataracts. For patients with cataracts or for refractive lens exchange in older patients, monovision can be achieved with binocular implantation of monofocal lenses. In these cases, proper patient selection is crucial. Satisfactory results with multifocality can be achieved via the implantation of a range of IOLs, including multifocal, bifocal, and trifocal lenses. Accommodating IOLs offer partial restoration of accommodation through the forward movement of the lens during accommodative effort. Recently, implants with accommodative qualities have been combined with a multifocal design. The efficacy of all these methods to restore near vision depends on characteristics of the individual patient, including biometric parameters, age, and nearvision needs in everyday life. We must remember to explain to patients that, even if the operation is properly performed, the results for a given individual may be unsatisfactory. It is also important to note that not every method is designed for all patients, and not all patients are candidates for every approach.