Monofocal IOLs are standard lenses used in cataract surgery. One of the major disadvantages of these conventional IOLs is that they can only be focused for one particular distance – either optical infinity (rendering the eye emmetropic) or a fixed finite distance (rendering the eye myopic). Patients who undergo a standard IOL implantation no longer experience clouding from cataracts, but they are unable to accommodate (change focus from near to far, far to near, and to distances in between). This is not a concern for most cataract surgeries, as they are primarily performed on elderly people that are already completely presbyopic. However, it can be a problem for patients that are not yet presbyopic (or are in the early stages of presbyopia) undergoing refractive lens exchange for the sake of correcting refractive errors.
Multifocal IOLs attempt to provide simultaneous viewing of distance vision and near vision. Trifocal IOLs can provide intermediate vision.Many multifocal IOL designs attempt to achieve this simultaneous viewing focus using a concentric ring design, which alternates distance and near focal points. However, many concentric ring multifocal lenses used today are prone to glare and mildly compromised focus at all ranges of vision.
A toric IOL is a type of toric lens used to correct preexisting corneal astigmatism at the time of cataract surgery.
Standard toric IOLs are monofocal, permanently focused on distant objects. Multifocal toric IOLs are also available. These lenses provide the patient not only with correction of preexisting astigmatism, but also with multiple-focused vision at far and reading distance.
Phakic IOLs (PIOLs) are intraocular lenses which are placed in an eye that still contains a natural human crystalline lens. PIOLs are sometimes referred to as an ‘implantable contact lenses’ (ICLs). As with other IOLs, PIOLs can be either spheric or toric. Toric PIOLs have to be aligned with the meridian of astigmatism; toric IOL misalignment or rotation can lead to residual or even greater astigmatism postoperatively.
Laser vision correction is by far the best option to eliminate the dependency on glasses and contact lenses. The shape of your cornea attributes to your eye power. You could have myopia (short-sight), hypermetropia (long-sight) or astigmatism (blurry vision) depending on the point where the light from an object you see gets focussed inside your eyes. During a laser vision correction surgery, the shape of your cornea is altered in such a way that light entering into the eye is focused at the right spot on the retina. This is a simple procedure and takes less than half an hour from start to finish. Also, you’ll be able to resume your normal life in just a few days.
Laser vision correction has evolved rapidly over the last twenty years. LASIK is the most popular refractive error correction surgery and can rectify a power of -1D to -9D in myopia patients and up to +4D in hypermetropia patients. In LASIK, a motorized blade is used to create a flap of the first two layers of the cornea, and a computer-controlled laser is used to reshape the inner layers. Intralase is a blade-free approach where a specialized laser is used to create this flap and then reshape it. ReLEx SMILE has come in as the next advancement and is bladeless and flapless with much faster recovery.
Laser vision correction is performed as a day-care surgery, and the patient can resume to normalcy in very little time. There’s an expert team of doctors that undergo special training to perform the procedure in the most skilful way. Patients that want to undergo laser vision correction are counselled pre and post-operation so that they can anticipate and appreciate the outcome of the procedure opted for.
Glaucoma drainage devices are designed to divert aqueous humor from the anterior chamber to an external reservoir, where a fibrous capsule forms about 4-6 weeks after surgery and regulates flow. These devices have shown success in controlling intraocular pressure (IOP) in eyes with previously failed trabeculectomy and in eyes with insufficient conjunctiva because of scarring from prior surgical procedures or injuries. They also have demonstrated success in complicated glaucomas, such as uveitic glaucoma, neovascular glaucoma, and pediatric and developmental glaucomas, among others.
Photorefractive keratectomy (PRK) is a type of refractive laser surgery that reshapes the cornea to correct myopia (short-sightedness), hyperopia (farsightedness and astigmatism (unevenly curved cornea). It helps in decreasing or eliminating the dependency on glasses or contact lenses. The goal of refractive surgery is to allow less dependency on glasses and contact lenses rather than achieve the complete absence of refractive error.
Pre Descemet’s Endothelial Keratoplasty is a partial thickness corneal transplant. The diseased endothelial cells are removed from the patient’s eye and selectively replaced with a new layer of endothelial cells which are taken from the donated eye. The endothelial cells are the healthy cells lining the back of the cornea which pump fluid from the cornea to prevent the cornea swelling. The normal endothelial count is 2000 – 3000 cells/mm2. When the cells decrease in number < 500 cells/mm2, corneal decompensation occurs, clarity of the cornea reduces and eventually the vision becomes cloudy.