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.

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.

Having multifocal intraocular lenses (IOLs) implanted in both eyes for the treatment of cataracts produces better visual outcomes than a single multifocal IOL implanted in one eye, according to a study published in the June 2009 issue of Journal of Cataract & Refractive Surgery.

In the study, an AcrySof ReSTOR multifocal IOL was implanted 1) in one eye of patients with a natural (non-cataractous) lens in the other eye; 2) in one eye of patients who had a conventional monofocal IOL implanted in the other eye; and 3) in both eyes of patients with a cataract in one or both eyes.

Visual acuity, contrast sensitivity and stereopsis (depth perception) of all eyes was measured six months after cataract surgery. Patients also were surveyed about the quality of their vision and their overall satisfaction.

Patients receiving bilateral multifocal IOLs had the highest satisfaction score (92 percent), and 77 percent of these patients achieved spectacle independence after surgery.

Among patients with the multifocal IOL implanted in one eye only, 75 percent reported being satisfied with their vision, and spectacle independence was achieved by 56 percent of patients with a natural lens in their other eye and 65 percent of those who had a monofocal IOL implanted in their other eye.

Patients with bilateral multifocal IOLs also had better uncorrected near visual acuity, stereopsis, best-corrected near vision and best-corrected intermediate vision.

More patients with bilateral multifocal IOLs (77 percent) experienced halos at night compared with patients who received a multifocal IOL in one eye only (57 percent), but in most cases halos were minot and did not significantly affect patients’ overall satisfaction with their visual outcome.

German researchers have found that visual performance — specifically reading speed — with multifocal intraocular lenses after cataract surgery improves with time, suggesting the brain adapts to multifocal IOLs as time goes by.

“When analyzing multifocal lens performance, it is important to follow patients over time and to remember that there is a brain behind the eyes,” said Manfred R. Tetz, MD, of the University of Berlin at the 2009 annual meeting of the American Society of Cataract and Refractive Surgery held recently in San Francisco.

Dr. Tetz and colleagues evaluated the visual performance of 25 patients who had one of two brands of multifocal IOLs (Tecnis Multifocal IOL, Abbott Medical Optics; AcrySof ReSTOR, Alcon Laboratories) implanted bilaterally after cataract removal. All patients were examined for a period of six to 18 months after surgery.

Both multifocal IOLs provided good uncorrected visual acuity (UCVA) at all distances. Mean UCVA at intermediate (arm’s length) was approximately 20/40 for both groups. 

When evaluating reading speed as a measure of visual performance, the researchers found that the patients were capable of significantly faster reading speeds than patients who received bilateral multifocal IOL implants and were followed for only three months.

“This indicates there is a neural adaptation by the patient over time,” said Dr. Tetz.

Although reading speed for both groups slowed with smaller font sizes, patients in the AcrySof ReSTOR multifocal IOL group could read small fonts faster than those in the Tecnis Multifocal IOL group.

Source:  Faster reading speeds over time indicates brain adapts to multifocal IOLs. Ophthalmology Times. Meeting E-News, April 4, 2009.