- Author: Vicente Victor D Ocampo, Jr, MD; Chief Editor: John D Sheppard, Jr, MD, MMSc more...
Senile cataract is an age-related, vision-impairing disease characterized by gradual progressive thickening of the lens of the eye. It is the world’s leading cause of treatable blindness.
See What the Eyes Tell You: 16 Abnormalities of the Lens, a Critical Images slideshow, to help recognize lens abnormalities that are clues to various conditions and diseases.
Signs and symptoms
A patient with senile cataract often presents with a history of gradual progressive visual deterioration and disturbance in night and near vision. Characteristics of senile cataract include the following:
Decreased visual acuity - The most common complaint of patients with senile cataract
Glare - Can range from a decrease in contrast sensitivity in brightly lit environments or disabling glare during the day to glare with oncoming headlights at night
Myopic shift - The progression of cataracts frequently increases the anteroposterior (AP) axis and therefore the diopteric power of the lens, resulting in a mild to moderate degree of increased myopia or myopic shift
Monocular diplopia - - At times, the nuclear changes are concentrated in the inner layers of the lens, resulting in a refractile area in the center of the lens, the so called “lens within a lens” phenomenon, which may lead to monocular diplopia that is not correctable with spectacles, prisms, or contact lenses
See Clinical Presentation for more detail.
A complete ocular examination must be performed, beginning with visual acuity for near and far distances. When the patient complains of glare, visual acuity should be tested in a brightly lit room. Contrast sensitivity may also be checked, especially if the history points to a possible problem.
Diagnosis can also include the following:
Examination of the ocular adnexa and intraocular structures - May provide clues to the patient's cataract etiology, concomitant disease, and eventual visual prognosis
Swinging flashlight test - Detects a Marcus Gunn pupil or a relative afferent pupillary defect (RAPD) indicative of optic nerve lesions or diffuse macular involvement
Slit lamp examination - Should concentrate on the evaluation of not only lens opacity but also other ocular structures (eg, conjunctiva, cornea, iris, anterior chamber)
Examination of nuclear size and brunescence - After dilation, nuclear size and brunescence as indicators of cataract density can be determined prior to phacoemulsification surgery
Direct and indirect ophthalmoscopy - To evaluate the integrity of the posterior pole
Ocular imaging studies such as ultrasonography, computed tomography (CT) scanning, or magnetic resonance imaging (MRI) are requested when a significant posterior pole pathology is suspected and an adequate view of the back of the eye is obscured by a dense cataract.
Clinical staging of senile cataract is based largely on the visual acuity of the patient, as follows:
Hypermature cataract - Patient generally sees worse than count fingers (CF) or hand motion (HM) owing to a dense white, deeply dark opaque brunescent, or Morgagnian cataract
Mature cataract - Patient cannot read better than 20/200 on the visual acuity chart
Immature cataract - Patient can distinguish letters at lines better than 20/200
Incipient cataract or dysfunctional lens syndrome - Patient reports visual complaints but can still read at 20/20 despite lens opacity confirmed via slit lamp examination
See Workup for more detail.
Lens extraction is the definitive treatment for senile cataract. It can be accomplished via the following procedures:
Intracapsular cataract extraction (ICCE) - Involves extraction of the entire lens, including the posterior capsule and zonules; the many postoperative complications associated with this procedure has led to a significant decline in its use
Extracapsular cataract extraction (ECCE) - Involves the removal of the lens nucleus through an opening in the anterior capsule and a relatively large limbal incision, with retention of the integrity of the posterior capsule
Phacoemulsification - Also involves extraction of the lens nucleus through an opening in the anterior capsule; an ultrasonically driven needle is used to fragment the nucleus of the cataract; the lens substrate is then aspirated through a needle port via a small limbal or scleral incision in a process termed phacoemulsification
Intraocular lens (IOL) implantation is used in combination with each of these techniques, although ECCE and phacoemulsification allow for better anatomical placement of the IOL than does ICCE.
Senile cataract is a vision-impairing disease characterized by gradual, progressive thickening of the lens. It is the leading cause of blindness in the world today. This is unfortunate, considering that the visual morbidity brought about by age-related cataract is reversible. As such, early detection, close monitoring, and timely surgical intervention must be observed in the management of senile cataracts. Even greater challenges abound in economically disadvantaged and geographically isolated regions where limited healthcare access precludes early intervention. The subsequent section is a general overview of senile cataract and its management.
The pathophysiology behind senile cataracts is complex and yet to be fully understood. In all probability, its pathogenesis is multifactorial involving complex interactions between various physiologic processes modulated by environmental, genetic, nutritional, and systemic factors. As the lens ages, its weight and thickness increases while its accommodative power decreases. As the new cortical layers are added in a concentric pattern, the central nucleus is compressed and hardened in a process called nuclear sclerosis.
Multiple mechanisms contribute to the progressive loss of transparency of the lens. The lens epithelium is believed to undergo age-related changes, particularly a decrease in lens epithelial cell density and an aberrant differentiation of lens fiber cells. Although the epithelium of cataractous lenses experiences a low rate of apoptotic death, which is unlikely to cause a significant decrease in cell density, the accumulation of small scale epithelial losses may consequently result in an alteration of lens fiber formation and homeostasis, ultimately leading to loss of lens transparency. Furthermore, as the lens ages, a reduction in the rate at which water and, perhaps, water-soluble low-molecular weight metabolites can enter the cells of the lens nucleus via the epithelium and cortex occurs with a subsequent decrease in the rate of transport of water, nutrients, and antioxidants.
Consequently, progressive oxidative damage to the lens with aging takes place, leading to senile cataract development. Various studies showing an increase in products of oxidation (eg, oxidized glutathione) and a decrease in antioxidant vitamins and the enzyme superoxide dismutase underscore the important role of oxidative processes in cataractogenesis.
Another mechanism involved is the conversion of soluble low-molecular weight cytoplasmic lens proteins to soluble high molecular weight aggregates, insoluble phases, and insoluble membrane-protein matrices. The resulting protein changes cause abrupt fluctuations in the refractive index of the lens, scatter light rays, and reduce transparency. Other areas being investigated include the role of nutrition in cataract development, particularly the involvement of glucose and trace minerals and vitamins.
Senile cataract can be classified into 3 main types: nuclear cataract, cortical cataract, and posterior subcapsular cataract. Nuclear cataracts result from excessive nuclear sclerosis and yellowing, with consequent formation of a central lenticular opacity. In some instances, the nucleus can become very opaque and brown, termed a brunescent nuclear cataract. Changes in the ionic composition of the lens cortex and the eventual change in hydration of the lens fibers produce a cortical cataract. Formation of granular and plaquelike opacities in the posterior subcapsular cortex often heralds the formation of posterior subcapsular cataracts.
In the Framingham Eye Study from 1973-1975, senile cataract was seen in 15.5% of the 2477 patients examined. The overall rates of senile cataract in general, and of its 3 main types (ie, nuclear, cortical, posterior subcapsular), rapidly increased with age; for the oldest age group (≥75 y), nuclear, cortical, and posterior subcapsular cataracts were found in 65.5%, 27.7%, and 19.7% of the study population, respectively. Nuclear opacities were the most commonly seen lens change.
An updated study by the Wilmer Eye Institute in 2004 noted that approximately 20.5 million (17.2%) Americans older than 40 years had a cataract in either eye and 6.1 million (5.1%) were pseudophakic/aphakic. These numbers are expected to rise to 30.1 million cataracts and 9.5 million cases with pseudophakia/aphakia by 2020.
Prevent Blindness America currently estimates that more than 22 million Americans aged 40 years and older have a cataract. An average of 3 million Americans undergo cataract surgery every year, with a 95% success rate of obtaining a best corrected vision of 20/20-20/40.
Senile cataract continues to be the main cause of visual impairment and blindness in the world. In recent studies performed in China,[2, 3] Canada, Japan, Denmark, Argentina, and India, cataract was identified as the leading cause of visual impairment and blindness, with statistics ranging from 33.3% (Denmark) to as high as 82.6% (India). Published data estimate that 1.2% of the entire population of Africa is blind, with cataract causing 36% of this blindness. In a survey conducted in 3 districts in the Punjab plains, the overall rates of occurrence of senile cataract was 15.3% among 1269 persons examined who were aged 30 years and older and 4.3% for all ages. This increased markedly to 67% for ages 70 years and older. An analysis of blind registration forms in the west of Scotland showed senile cataract as 1 of the 4 leading causes of blindness.
Most morbidity associated with senile cataracts occurs postoperatively and is discussed in further detail later. Failure to treat a developing cataract surgically may lead to devastating consequences, such as lens swelling and intumescence, secondary glaucoma, and, eventually, blindness.
While the risk of dying as a result of cataract extraction is almost negligible, studies have shown an increased risk of mortality in patients who underwent surgery. In a comparison of 167 patients aged 50 years or older who underwent cataract extraction at the New England Medical Center in a period of 1 year to 824 patients who elected 1 of 6 other surgical procedures, it was found that the former had almost twice the mortality of the latter. Further analysis showed no significant correlation between diabetes and increased mortality. In a similar 5-year mortality analysis, patients with cataracts who were younger than 75 years had significantly higher age-specific rates of mortality than would be expected from US life tables.
These data imply an association between senile cataracts and increased mortality. Meddings et al suggest that senile cataract may be a marker of generalized tissue aging, which may be independent of cumulative ultraviolet exposure. Hirsch and Schwartz who proposed the concept that senile cataracts reflect systemic phenomena rather than only a localized ocular disease share this view.
Although race has been suggested as a possible risk factor for senile cataract, scarce literature exists to prove this theory. However, it has been observed that unoperated cataracts account for a higher percentage of blindness among blacks compared to whites. Instead, various other correlates may explain racial disparities, including medical comorbidities such as diabetes mellitus or lifetime ultraviolet (UV) exposure due to occupation, altitude, or latitude.
Studies on the prevalence of senile cataract between males and females have yielded contrasting results.
In the Framingham Eye Study from 1973-75, females had a higher prevalence than males in both lens changes (63% vs 54.1%) and senile cataract (17.1% vs 13.2%).
Sperduto and Hiller noted that each of the 3 types of senile lens opacities was found more often in women than in men. In a separate investigation by Nishikori and Yamomoto, the male-to-female ratio was 1:8 with a female predominance in patients older than 65 years who were operated on for senile cataract.
In a hospital-based, case-control study of senile cataract conducted in Japan, it was observed that an increased risk of cataract was found in males who were presently spending 7 hours or more outdoors and in females with 4 or fewer remaining teeth. However, in another analysis by Martinez et al, no sexual difference was noted in the prevalence of senile cataract.
Age is an important risk factor for senile cataract. As a person ages, the chance of developing a senile cataract increases. In the Framingham Eye Study from 1973-1975, the number of total and new cases of senile cataract rose dramatically from 23.0 cases per 100,000 and 3.5 cases per 100,000, respectively, in persons aged 45-64 years to 492.2 cases per 100,000 and 40.8 cases per 100,000 in persons aged 85 years and older.
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