Diagnosis and Conventional Treatment
Cataracts are diagnosed by an ophthalmologist using the Snellen visual acuity test. In this test, the patient is asked to read letters that become smaller on every line, and the ability to recognize them is measured (Levy 2005; Medline 2012). Once suspected, cataracts are assessed using a specialized microscope that focuses light into a slit to examine the lens structure. It measures not only the visual acuity, but also the degree of light scattering, which is the transmission of the light in random directions when the environment that it crosses presents irregularities (van der Mooren 2011; Medline 2012). Cataracts are also detected using a device known as a funduscope or ophthalmoscope, which is used to examine the retinal blood vessels and other structures of the eye by inspection (Schneiderman 1990; Merck 2012). The inability to see the retinal blood vessels usually occurs because of an opacity that interferes with the ability of the light to pass through the eye, and this is usually caused by cataracts or bleeding inside the eye (Schneiderman 1990).
Once diagnosed, and after the stage and severity of the cataracts are assessed, a patient may elect to undergo surgical removal of the lens containing the cataract(s) and replacement with a synthetic intraocular lens (IOL). In these procedures, which usually last for less than an hour and are normally performed on an outpatient basis, surgeons make a small incision on the lens, disrupt the lens either ultrasonically or by using lasers, and insert the IOL into the capsule bag where the natural lens used to be located (Medline 2012).
If a cataract is so advanced that this procedure is unable to break up the lens, then a larger incision is made, and the lens nucleus is removed through the exposed lens capsule. The soft portions of the lens near the edges are removed using a vacuum, leaving a shell for IOL implantation. Referred to as extracapsular extraction, this surgical process can result in higher rates of secondary infection and other complications (eg, secondary cataracts) (Smith 1982; Ruit 1991; Apple 1992; Gyldenkerne 1998; Clark 2000; Haripriya 2012; Medline 2012; Merck 2012).
Other complications that may occur include swelling of the cornea, retinal detachment, internal eye infections, secondary glaucoma, excessive post-operative inflammation, capsular opacification, and other conditions that may result in permanent partial or complete loss of eyesight (Morikubo 2004; Franzco 2010; Speeg-Schatz 2011; Haug 2012; Taravati 2012).
Even without suffering from a serious complication, a significant number of people who have cataract surgery go on to develop clouding of the lens capsule (Pandey 2004; Eichenbaum 2012; Lichtinger 2012). This complication may occur at various times after surgery, usually three months to four years later (Pandey 2004). In these cases, the lens capsule, which was originally part of the lens previously removed, will require additional laser surgery. This complication has medical and financial implications, including additional medical care costs, time off from work, and patient suffering (Pandey 2004; Eichenbaum 2012). Younger patients are at higher risk for this complication (Pandey 2004).
If surgical removal of a lens with a cataract is inadvisable, or if significant loss of visual acuity has not occurred, ophthalmologists may suggest delaying surgery (National Eye Institute 2009; Medline 2012). Cataract surgery may also be inadvisable if the patient suffers from other forms of ocular disease, such as age-related macular degeneration, which was reported by some clinicians to worsen after cataract surgery (Casparis 2012). In the interim, patients are advised to use soft contact lenses or eyeglasses with stronger prescriptions and to adopt alternative treatment strategies (National Eye Institute 2009).
Secondary cataracts arise when, after surgery, lens epithelial cells divide and move to the back side of the lens where they transform into another cell type; the light-scattering changes they cause result in the secondary loss of vision (Coombes 1999; Marcantonio 1999; Wormstone 2009). This complication can also be thought of as a wound healing response that occurs after surgery (Bertelmann 2001). The rates of secondary cataract formation vary; some sources indicate that they may occur in up to 50% of patients, and while advances in surgical techniques helped lower their frequency in recent years, they were still reported to occur in 14-18% of patients, and remain a major complication (Coombes 1999; Spalton 1999; West-Mays 2010). They occur even more frequently and have a quicker onset in children (Awashti 2009). Secondary cataracts are easy to treat using laser treatment, and the risk of complications is small (Emery 1998; Spalton 1999). Immunological and gene therapy approaches to prevent this complication are under development and appear promising (Bertelmann 2001; Saika 2008).