All About Cataracts

Posterior capsule opacification (PCO) is one of the most common cataract surgery complications. It can occur relatively quickly after cataract surgery or months later.

The natural lens inside the eye is surrounded by a clear, membrane-like capsule. The front portion of this capsule is removed during cataract surgery to gain access to the cloudy natural lens and remove it. The posterior portion of the lens capsule is left intact to prevent loss of the gel-like fluid behind it, which would increase the risk of a detached retina from cataract surgery.

Posterior capsule opacification is thought to be caused by lens epithelial cells remaining in the eye after the cloudy lens is removed during cataract surgery. These cells can migrate onto the surface of the posterior capsule, where they undergo cellular changes and form an opaque membrane that decreases vision.

PCO can be successfully treated with a non-invasive outpatient procedure called a neodymium:YAG (Nd:YAG) laser capsulotomy. The procedure uses laser energy to obliterate the opacity, restoring vision.

Researchers at Storm Eye Institute, Medical University of South Carolina (Charleston, SC) recently conducted a retrospective study of 225 eyes that underwent cataract surgery with intraocular lens (IOL) implantation to investigate whether the type of IOL used in the surgery has an effect on the rate of PCO occurrence.

The eyes in the study received one of three IOLs: AcrySof ReSTOR SN60D3 (a spherical multifocal IOL), AcrySof Natural SN60AT (a spherical monofocal IOL), or AcrySof IQ SN60WF (an aspheric monofocal IOL).

All three IOLs are manufactured and marketed by the same company (Alcon, Inc.). Each lens was implanted in 75 study eyes, and mean follow-up time after surgery was 15.9 months.

The researchers found the rate of posterior capsule opacification after surgery was:

• 42.7 percent among eyes receiving the spherical multifocal IOL (ReSTOR)
• 28.0 percent among eyes receiving the spherical monofocal IOL (Natural)
• 14.7 percent among eyes receiving the aspheric monofocal IOL (IQ)

The Nd:YAG laser capsulotomy rate for eyes receiving the IOLs was 25.3 percent, 17.3 percent and 4.0 percent, respectively.

The researchers concluded that IOL design affects the rate of posterior capsule opacification occurring after cataract surgery.

Also, based on the rates of laser capsulotomy procedures performed, PCO appears to be less visually significant in eyes receiving the AcrySof IQ aspheric monofocal IOL, compared with eyes receiving the spherical multifocal IOL (AcrySof ReSTOR) and the spherical monofocal IOL (AcrySof Natural). 

The study was supported in part by Research to Prevent Blindness and the National Institutes of Health.

Source: Comparison of the incidence and visual significance of posterior capsule opacification between multifocal spherical, monofocal spherical, and monofocal aspheric intraocular lenses. Journal of Cataract & Refractive Surgery. July 2009.

Most cataracts are age-related eye problems and affect people age 50 and older. But cataracts also can be present at or near birth. In these instances, the lens opacities are called congenital cataracts.

Early treatment of congenital cataracts is essential for normal vision development and to prevent amblyopia or blindness.

Researchers in England recently investigated the current status of cataract surgery performed in the UK and Ireland for children age two years and younger.

Surveys were sent to 928 ophthalmologists, with a response rate of roughly 75 percent.

Findings of the study included:

• 47 of the respondents (7 percent) performed congenital cataract surgery on children age 2 and younger.
• Among those performing the surgery, 41 (87 percent) performed primary intraocular lens (IOL) implantation in these children.
• One quarter of respondents said they would not implant an IOL in a child under 1 year old. 

Other reasons surgeons provided for not performing primary IOL implantation included the presence of other eye conditions, including microphthalmos (70% of respondents), anterior eye problems (52 percent), posterior eye anomalies (61 percent), and glaucoma (19 percent).

Microphthalmos is a developmental anomaly characterized by one or both eyes being abnormally small.

The researchers concluded that surgery for congenital cataracts with IOL implantation in children age 2 years and younger has been widely adopted in the UK and Ireland by the relatively small number of ophthalmologists who manage these children.

Among these ophthalmologists, there is general agreement concerning surgical technique, choice of IOL design and the formula used for IOL power calculation. But variation exists in eligibility criteria for IOL implantation, and this may reflect a lack of consensus on which children are most likely to benefit from it and the risks involved.

The researchers also said there is a need for systematic studies of the outcomes of primary IOL implantation in younger children.

Source: Cataract surgery and primary intraocular lens implantation in children 2 years old in the United Kingdom and Ireland: findings of national surveys. British Journal of Ophthalmology. Published online June 16, 2009.

Researchers at Emory Eye Center and Emory Vision (Emory University, Atlanta) recently investigated the outcomes of cataract surgery performed with multifocal intraocular lenses (IOLs). The purpose of the study was to determine reasons for patient dissatisfaction with the procedure and the outcomes after remedial actions are taken.

The researchers reviewed the cases of 32 patients who were dissatisfied with the outcomes of their cataract surgery with multifocal IOL implantation. 

Most eyes (65 percent) had received an AcrySof ReSTOR IOL (Alcon) and the others (35 percent) received a ReZoom Multifocal IOL (Abbott Medical Optics). 

Outcomes analyzed included type of visual complaint, the remedial treatment applied to address the complaint, and the degree of improvement after intervention.

Findings of the study included:

1. Thirty patients (94 percent) reported blurred vision.
2. Fifteen patients (47 percent) reported photic phenomena (visual disturbances caused by optical aberrations; also called “negative dysphotopsia”).
3. Thirteen patients (41 percent) reported both blurred vision and photic phenomena. 

Causes of blurred vision included:

• Posterior capsule opacification, or “PCO” (22 eyes, 54 percent)
• Residual nearsightedness, farsightedness or astigmatism (12 eyes, 29 percent)
• Dry eye syndrome (6 eyes, 15 percent)

Causes of photic phenomena included:

• PCO (12 eyes, 66 percent)
• IOL decentration (2 eyes, 12 percent)
• Retained lens fragment from the removed cataractous lens (1 eye, 6 percent)
• Dry eye syndrome (1 eye, 6 percent)

Remedial treatments applied to relieve patient symptoms included artificial tears and other dry eye therapy, laser surgery for PCO and surgery for IOL exchange.

Thirty-five eyes (81 percent) had improvement with conservative treatment. Five eyes (12 percent) did not have improvement despite treatment combinations. Three eyes (7 percent) required IOL exchange.

The researchers concluded complaints of blurred vision and photic phenomena after multifocal IOL implantation can be effectively managed with appropriate treatment, though a few eyes may require IOL exchange.

The study was supported in part by Research to Prevent Blindness and the National Institutes of Health.

Source: Dissatisfaction after multifocal intraocular lens implantation. Journal of Cataract and Refractive Surgery. June 2009.

Bilateral cataract surgery intentionally designed for monovision produces good visual acuity and high patient satisfaction, according to a study published in the Journal of Cataract and Refractive Surgery. 

Researchers in Australia evaluated the outcomes of cataract surgery performed on both eyes of 26 patients. In all cases, a monovision correction was performed with intraocular lenses (IOLs). The target refractive endpoint of the second eye corrected for near vision was mild to moderate myopia ranging from -1.00 D to -1.50 D. 

Visual acuity, contrast sensitivity, stereopsis, and patient satisfaction were measured prior to surgery and 3 to 4 months post-operatively. Patients were also asked how frequently they needed eyeglasses after surgery.

Monovision is a method of vision correction where one eye is fully corrected for distance vision and the other eye is made (or is left) nearsighted so a person with presbyopia can see acceptably well up close without reading glasses. Monovision can be performed with contact lenses or refractive surgery, including refractive cataract surgery.)

Results of the study included:

1. 96 percent of the patients achieved uncorrected binocular distance visual acuity of at least 20/30.
2. 92 percent achieved approximately 20/30 or better uncorrected near visual acuity. 
3. Good depth perception and contrast sensitivity were maintained after surgery. 

Patients were generally satisfied with their vision after surgery. Approximately 25 percent of patients did not need glasses for any reason; one patient was totally dependent on spectacles. No patient required an IOL exchange or other additional refractive surgery.

The authors of the study concluded monovision cataract surgery achieves good visual function and patient satisfaction without the risk of troublesome visual symptoms sometimes associated with multifocal IOLs used in cataract surgery to correct presbyopia.

Source: Patient satisfaction and visual function after pseudophakic monovision. Journal of Cataract and Refractive Surgery. June 2009.