Cataract Surgery-Indications, Techniques, and Intraocular Lens Selection

Abstract

Background: Opacification of the lens of the eye (cataract) is usually due to aging. It is a painless, progressive condition that affects contrast and color perception and alters refraction, leading to visual loss that may be total. In cataract surgery, the turbid lens is replaced by an artificial lens. An estimated 600 000 to 800 000 such procedures are performed in Germany each year.

Methods: This review is based on pertinent publications retrieved by a selective search in PubMed, including meta-analyses, Cochrane reviews, and randomized controlled clinical trials (RCTs).

Results: Cataract is the most common reversible cause of blindness around the world (approximately 95 million people). The surgical replacement of a turbid lens with an artificial lens is usually carried out under local anesthesia. The standard technique for fragmentation of the nucleus of the lens is ultrasonic phacoemulsification. RCTs have not shown the superiority of the femtosecond laser over phacoemulsification for this purpose so far. The spectrum of artificial intraocular lenses, aside from the conventional type with a single focus, include lenses with multiple foci, extended-depth-of-focus (EDOF) lenses, and astigmatism-correcting lenses.

Conclusion: In Germany, cataract surgery is usually performed on an outpatient basis under local anesthesia. Artificial lenses with various additional functions are available nowadays; the choice of lens depends on the needs of the individual patient. Patients must be adequately informed about the advantages and disadvantages of the different lens systems.

Figure 1

Lens findings on slit-lamp examination a) Advanced opacification of the left lens; b) incipient opacification of the right lens.

Figure 2

Simplified imaging principle of various types of intraocular lenses. Monofocal lenses (a) have a single focal point; the target refraction of these lenses can be selected either for distant vision (emmetropic target refraction) or for near vision (myopic target refraction). Bifocal lenses (b) have one focus for distant and one for near vision; trifocal lenses (c) have a third focus in the intermediate range. Trifocal lenses generally use 50% of the incipient light for vision at a distance, 20% for the intermediate range, and 30% for the near range. In extended-depth-of-focus (EDOF) lenses (d), the focus is dispersed over an extended range. IOL, intraocular lens

Figure 3

Different types of lens as seen using the slit lamp In a monofocal lens (a), the body (IOL optic) of the lens has no markings or special grinding patterns; the retaining haptics may be made of a different material than the body of the lens, depending on the lens type and manufacturer. Toric lenses that compensate for faulty corneal curvature (astigmatism) (b) bear a mark (yellow arrows) indicating the axial position of the torus that is needed for correct intraocular rotation and lens position within the capsular bag. Trifocal lenses (c) and extended-depth-of-focus (EDOF) lenses (d) have a very similar arrangement of the rings in the lens body; a lens of either type may contain a torus (line in [c] and dotted line in [d]).