Cataract Clinical Trials, Diagnosis, and Treatment

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Cataract

A Cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Early on in the development of age-related cataract the power of the crystalline lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. Moreover, with time the cataract cortex liquefies to form a milky white fluid in a Morgagnian Cataract, and can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause phacomorphic glaucoma. Very advanced cataracts with weak zonules are liable to dislocation anteriorly or posteriorly. Such spontaneous posterior dislocations (akin to the historical surgical procedure of couching) in ancient times were regarded as a blessing from the heavens, because it restored some perception of light in the bilaterally affected patients.

Cataract derives from the Latin cataracta meaning "waterfall" and the Greek kataraktes and katarrhaktes, from katarassein meaning "to dash down" (kata-, "down"; arassein, "to strike, dash"). As rapidly running water turns white, the term may later have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternate meaning, "portcullis," so it is also possible that the name came about through the sense of "obstruction". Early Persian physicians called the term nazul-i-ah, or 'descent of the water' - vulgarised into waterfall disease or cataract - believing such blindness to be caused by a pouring-out of corrupt humour into the eye.

Current Research

For current research articles click - here

Causes

Cataracts develop from a variety of reasons, including long-term ultraviolet exposure, exposure to radiation, secondary effects of diseases such as diabetes, hypertension and advanced age; they are usually a result of denaturation of lens proteins. Genetic factors are often a cause of congenital cataracts and positive family history may also play a role in predisposing someone to cataracts at an earlier age, a phenomenon of "anticipation" in pre-senile cataracts. Cataracts may also be produced by eye injury or physical trauma. A study among Icelandair pilots showed commercial airline pilots as three times more likely to develop cataracts than people with non-flying jobs. This is thought to be caused by excessive exposure to radiation coming from outer space.[4] Cataracts are also unusually common in persons exposed to infrared radiation, such as glassblowers who suffer from "exfoliation syndrome". Exposure to microwave radiation can cause cataracts.

Cataracts may be partial or complete, stationary or progressive, hard or soft.

Some drugs can induce cataract development, such as Corticosteroids and Ezetimibe.

There are various types of cataract, e.g. nuclear, cortical, mature, hypermature. Cataracts are also classified by their location, e.g. posterior (classically due to steroid use[5][6]) and anterior (common (senile) cataract related to aging).

Epidemiology

Cataracts are the leading cause of blindness in the world.

In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 to 64, 60% of those between the ages 65 and 74, and 91% of those between the ages of 75 and 85.

Cataract Surgery

The most effective and common treatment is to surgically remove the cloudy lens. There are two types of surgery that can be used to remove cataracts: extra-capsular (extracapsular cataract extraction, or ECCE) and intra-capsular (intracapsular cataract extraction, or ICCE).

Extra-capsular (ECCE) surgery consists of removing the lens but leaving the majority of the lens capsule intact. High frequency sound waves (phacoemulsification) are sometimes used to break up the lens before extraction.

Intra-capsular (ICCE) surgery involves removing the entire lens of the eye, including the lens capsule, but it is rarely performed in modern practice. In either extra-capsular surgery or intra-capsular surgery, the cataractous lens is removed and replaced with a plastic lens (an intraocular lens implant) which stays in the eye permanently.

Cataract operations are usually performed using a local anaesthetic and the patient is allowed to go home the same day. Recent improvements in intraocular technology now allow cataract patients to choose a multifocal lens to create a visual environment in which they are less dependent on glasses. Under some medical systems multifocal lenses cost extra. Traditional intraocular lenses are monofocal.

Complications after cataract surgery, including endophthalmitis, posterior capsular opacification and retinal detachment, are possible.

In ICCE there is the issue of the Jack in the box phenomenon where the patient has to wear aphakic glasses - alternatives include contact lenses but these can prove to be high maintenance, particularly in dusty areas.

Prevention

Although cataracts have no scientifically proven prevention, it is sometimes said that wearing ultraviolet-protecting sunglasses may slow the development of cataracts. Regular intake of antioxidants (such as vitamin A, C and E) is theoretically helpful, but taking them as a supplement has been shown to have no benefit.

Recent Research

Although statins are known for their ability to lower lipids, they are also believed to have antioxidant qualities. It is believed that oxidative stress plays a role in the development of nuclear cataracts, which are the most common type of age-related cataract. To explore the relationship between nuclear cataracts and statin use, a group of researchers took a group of 1299 patients who were at risk of developing nuclear cataracts and gave some of them statins. Their results suggest that statin use in a general population may be associated with a lower risk of developing nuclear cataract disease.

Research is scant and mixed but weakly positive for the nutrients lutein and zeaxanthin. Bilberry extract shows promise in rat models and in clinical studies.

Types of Cataracts

The following is a classification of the various types of cataracts. This is not comprehensive and other unusual types may be noted.

Classified by etiology
- Age-related cataract
  - Immature Senile Cataract (IMSC) - partially opaque lens, disc view hazy
  - Mature Senile Cataract (MSC) - Completely opaque lens, no disc view
  - Hypermature Senile Cataract (HMSC) - Liquefied cortical matter: Morgagnian Cataract
- Congenital cataract
  - Sutural cataract
  - Lamellar cataract
  - Zonular cataract
  - Total cataract
- Secondary cataract
  - Drug-induced cataract (e.g. Corticosteroids)
- Traumatic cataract
  - Blunt trauma (capsule usually intact)
  - Penetrating trauma (capsular rupture & leakage of lens material - calls for an emergency surgery for extraction of lens and leaked material to minimize further damage)
Classified by location of opacity within lens structure (However, mixed morphology is quite commonly seen, e.g. PSC with nuclear changes & cortical spokes of cataract)
- Anterior cortical cataract
- Anterior polar cataract
- Anterior subcapsular cataract
- Nuclear cataract - Grading correlates with hardness & difficulty of surgical removal
  - 1 - Grey
  - 2 - Yellow
  - 3 - Amber
  - 4 - Brown/Black (Note: "Black cataract" translated in some languages (like Hindi) refers to Glaucoma, not the color of the lens nucleus)
- Posterior cortical cataract
- Posterior polar cataract (importance lies in higher risk of complication - posterior capsular tears during surgery)
- Posterior subcapsular cataract (PSC) (clinically common)
  - After-cataract - posterior capsular opacification subsequent to a successful extracapsular cataract surgery (usually within 3 months - 2 years) with or without IOL implantation. Requires a quick & painless office procedure with Nd:YAG laser capsulotomy to restore optical clarity.

Associations with Systemic Conditions

Chromosomal disorders
- Alport's syndrome
- Cri-du-chat syndrome
- Conradi's syndrome
- Myotonia dystrophica
- Patau's syndrome
- Schmid-Fraccaro syndrome
- Trisomy 18 (Edward's syndrome)
- Turner's syndrome
Disease of the skin and mucous membranes
- Atopic dermatitis
- Basal-cell nevus syndrome
- Ichthyosis
- Pemphigus
Metabolic and nutrition diseases
- Aminoaciduria (Lowe's syndrome)
- Diabetes mellitus
- Fabry's disease
- Galactosemia
- Homocystinuria
- Hypervitaminosis D
- Hyperparathyroidism
- Hypothyroidism
- Mucopolysaccharidoses
- Wilson's disease
Infectious diseases
- Congenital
  - Congential herpes simplex
  - Congenital syphilis
  - Cytomegalic inclusion disease
  - Rubella
- Others
  - Cysticercosis
  - Leprosy
  - Onchocerciasis
  - Toxoplasmosis
Toxic substances introduced systemically
- Corticosteroids
- Haloperidol
- Miotics
- Triparanol

(adapted from Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Cateract)

Findings From Current Research

Variability of Axial Length, Anterior Chamber Depth, and Lens Thickness in the Cataractous Eye

Authors: Jivrajka R, Shammas MC, Boenzi T, Swearingen M, Shammas HJ.

Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, USA.

PURPOSE: To review and evaluate the biometry measurements in 750 eyes (first eye developing cataract) of 750 consecutive patients with no retinal pathology. SETTING: Private practice, Lynwood, California, USA. METHODS: All measurements were performed with the I3 system A-scan (Innovative Imaging, Inc.) using an immersion technique. The axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) measurements were evaluated in relation to each other and in relation to age, sex, and keratometric readings. RESULTS: The mean AL was 23.46 mm +/- 1.03 (SD), the mean ACD was 2.96 +/- 0.45 mm, and the mean LT was 4.93 +/- 0.56 mm. Men presented for surgery at an earlier age than women (mean 73 +/- 9.41 years versus 75 +/- 8.55 years) with a longer AL (23.76 +/- 1.00 mm versus 23.27 +/- 1.01 mm). The AL tended to be longer in younger patients (r = -0.127; P<.001); the ACD tended to be deeper in younger patients (r = -0.250; P<.001) and in longer eyes (r = 0.423; P<.001). The LT tended to be thicker in older patients (r = 0.385; P<.001) and in shorter eyes (r = -0.179; P<.001), with large scatter in the distribution. CONCLUSIONS: There was a positive correlation between AL and ACD and an inverse correlation between AL and LT. Also, AL was inversely correlated with age and corneal power.

Journal: J Cataract Refract Surg. 2008 Feb;34(2):289-94.
Adapted from PubMed; click here to access full journal article.

Self-Reported Age-Related Eye Diseases and Visual Impairment in the United States: Results of the 2002 National Health Interview Survey

Authors: Ryskulova A, Turczyn K, Makuc DM, Cotch MF, Klein RJ, Janiszewski R.

Office of Analysis and Epidemiology, National Center for Health Statistics, CDC, 3311 Toledo Rd, Room 6309, Hyattsville, MD 20782, USA. aryskulova@cdc.gov

OBJECTIVES: We sought to establish national data on the prevalence of visual impairment, blindness, and selected eye conditions (cataract, diabetic retinopathy, glaucoma, and macular degeneration) and to characterize these conditions within sociodemographic subgroups. METHODS: Information on self-reported visual impairment and diagnosed eye diseases was collected from 31,044 adults. We calculated weighted prevalence estimates and odds ratios with logistic regression using SUDAAN. RESULTS: Among noninstitutionalized US adults 18 years and older, the estimated prevalence for visual impairment was 9.3% (19.1 million Americans), including 0.3% (0.7 million) with blindness. Lifetime prevalence of diagnosed diseases was as follows: cataract, 8.6% (17 million); glaucoma, 2.0% (4 million); macular degeneration, 1.1% (2 million); and diabetic retinopathy, 0.7% (1.3 million). The prevalence of diabetic retinopathy among persons with diagnosed diabetes was 9.9%. CONCLUSIONS: We present the most recently available national data on self-reported visual impairment and selected eye diseases in the United States. The results of this study provide a baseline for future public health initiatives relating to visual impairment.

Journal: Am J Public Health. 2008 Mar;98(3):454-61. Epub 2008 Jan 30.
Adapted from PubMed; click here to access full journal article.

Cataract Extraction After Implantation of a Type I Boston Keratoprosthesis

Authors: Harissi-Dagher M, Colby KA.

Cornea and External Disease, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA.

PURPOSE: To describe cataract extraction and intraocular lens placement in a patient with an existing Type I Boston keratoprosthesis. METHODS: Case report to describe the surgical technique used to remove a cataract that developed after Boston keratoprosthesis placement. RESULTS: Extracapsular cataract extraction by using an open-sky technique can be used to remove a cataractous lens in the setting of an existing Boston keratoprosthesis. CONCLUSIONS: Although this case shows that it is possible to perform cataract surgery after Boston keratoprosthesis placement, it is prudent to remove the crystalline lens during the initial surgery, even in the absence of a visually significant cataract, because several factors work together to almost guarantee eventual cataract development if the patient is left phakic.

Journal: Cornea. 2008 Feb;27(2):220-2.
Adapted from PubMed; click here to access full journal article.

Cataract Classification Using Serial Examinations in the Age-Related Eye Disease Study: Age-Related Eye Disease Study Report no. 24

Authors: Sperduto RD, Clemons TE, Lindblad AS, Ferris FL 3rd; Age-Related Eye Disease Study Research Group.

National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA.

PURPOSE: To describe use of serial lens examinations to assign cataract phenotype in the Age-Related Eye Disease Study (AREDS). DESIGN: Cohort study. METHODS: Lens photographs were graded annually using the AREDS system for classifying cataracts. Nuclear grades (0.9 to 6.1) were assigned using standard photographs. Percentage of pupillary involvement was used to assign cortical and posterior subcapsular grades. Cutpoints were established for the presence or absence of each type of opacity (absent<4.0 for nuclear, <10% for cortical, and <5% of central 5 mm for posterior subcapsular). An algorithm weighted for grades at the last three examinations was used to assign cataract phenotype. Separately, cataract phenotype was assigned as grade predicted at final visit by linear regression of serial grades. Results from the two approaches were compared and final person phenotypes were established. These person cataract phenotype assignments were compared with phenotype assignments based on the last serial grade alone. RESULTS: Four thousand six hundred and twenty-eight AREDS participants aged 55 to 80 years at baseline had median follow-up of 10.6 years. Person phenotype assignments agreed for the two approaches in 4,557 (98.5%) participants after some algorithmic adjudication. Phenotypes were no cataract (n=1,418), nuclear (n=1,287), cortical (n=1,396), posterior subcapsular (n=541), cataract surgery and no specific opacity type (n=335), and questionable (n=426). Phenotype assignments based on serial grades and on last examination alone were in good agreement. CONCLUSIONS: Serial lens photographs obtained over a 10-year period were used to provide a robust assignment of cataract phenotype. Well-characterized cataract phenotypes are of importance as genetic studies of the AREDS cohort are considered.

Journal: Am J Ophthalmol. 2008 Mar;145(3):504-8. Epub 2008 Jan 16.
Adapted from PubMed; click here to access full journal article.

Dietary Carotenoids, Vitamins C and E, and Risk of Cataract in Women: A Prospective Study

Authors: Christen WG, Liu S, Glynn RJ, Gaziano JM, Buring JE.

Divisions of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215-1204, USA. wchristen@rics.bwh.harvard.edu

OBJECTIVE: To examine in prospective data the relation between dietary intake of carotenoids and vitamins C and E and the risk of cataract in women. DESIGN: Dietary intake was assessed at baseline in 39,876 female health professionals by using a detailed food frequency questionnaire. A total of 35,551 women provided detailed information on antioxidant nutrient intake from food and supplements and were free of a diagnosis of cataract. The main outcome measure was cataract, defined as an incident, age-related lens opacity responsible for a reduction in best-corrected visual acuity in the worse eye to 20/30 or worse based on self-report confirmed by medical record review. RESULTS: A total of 2031 cases of incident cataract were confirmed during a mean of 10 years of follow-up. Comparing women in the extreme quintiles, the multivariate relative risk of cataract was 0.82 (95% confidence interval, 0.71-0.95; test for trend, P = .04) for lutein/zeaxanthin and 0.86 (95% confidence interval, 0.74-1.00; test for trend, P = .03) for vitamin E from food and supplements. CONCLUSION: In these prospective observational data from a large cohort of female health professionals, higher dietary intakes of lutein/zeaxanthin and vitamin E from food and supplements were associated with significantly decreased risks of cataract.

Journal: Arch Ophthalmol. 2008 Jan;126(1):102-9.
Adapted from PubMed; click here to access full journal article.

Keratometry in Pediatric Eyes with Cataract

Authors: Trivedi RH, Wilson ME.

Miles Center for Pediatric Ophthalmology, Storm Eye Institute, Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425-5536, USA. trivedi@musc.edu

OBJECTIVES: To report the keratometry data of pediatric cataractous eyes (randomly selected single eye of bilateral cases; cataractous eye of unilateral cases) and to compare the keratometry data of the unilateral cataractous eye with the corresponding noncataractous fellow eye. METHODS: Retrospective review of preoperative data of patients who had undergone cataract surgery before 18 years of age. Eyes with traumatic cataract or lens subluxation were excluded. RESULTS: Of the 299 eyes analyzed in our study, the average (SD) keratometry value was 45.39 (3.08) diopters (D) (range, 39.25-63.5 D). Age and axial length (AL) demonstrated a significant linear relationship with values (P < .001, R(2): logarithm of age, 0.31; axial length, 0.32). Keratometry values of younger children (aged 0-6 months) were significantly different from those of older children (P < .001). Girls had steeper corneas when compared with boys (P = .03). The values of eyes with cataract in monocular cases were steeper than that of bilateral cases (P = .07). For unilateral cataract, the eye with the cataract had a significantly steeper cornea than the fellow eye (P = .02). CONCLUSION: The keratometry values of younger children were steeper than that of older children. In eyes with unilateral cataract, values of cataractous eyes were steeper compared with their noncataractous fellow eye.

Journal: Arch Ophthalmol. 2008 Jan;126(1):38-42.
Adapted from PubMed; click here to access full journal article.

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