Abstract
Introduction
Cataract accounts for over 47% of blindness worldwide, causing blindness in about 17.3 million people in 1990. Surgery for cataract in people with glaucoma may affect glaucoma control.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of surgery for age-related cataract without other ocular comorbidity? What are the effects of treatment for age-related cataract in people with glaucoma? What are the effects of surgical treatments for age-related cataract in people with diabetic retinopathy? What are the effects of surgical treatments for age-related cataract in people with chronic uveitis? We searched: Medline, Embase, The Cochrane Library, and other important databases up to May 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 20 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: for people with cataract without other ocular co-morbidity: cataract surgery alone, cataract surgery with non-concomitant glaucoma surgery, concomitant cataract and glaucoma surgery, intracapsular extraction, manual (large or small) incision extracapsular extraction, and phaco extracapsular extraction; for people with cataract with co-morbid diabetic retinopathy: cataract surgery alone, and adding diabetic retinopathy treatment to cataract surgery; for people with cataract and co-morbid chronic uveitis: cataract surgery, and medical control of uveitis at the time of cataract surgery.
Key Points
Cataracts are cloudy or opaque areas in the lens of the eye that can impair vision. Age-related cataracts are defined as those occurring in people >50 years of age, in the absence of known mechanical, chemical, or radiation trauma.
Cataract accounts for over 47% of blindness worldwide, causing blindness in about 17.3 million people in 1990.
Surgery for cataract in people with glaucoma may affect glaucoma control.
There is contradictory evidence about the effect of cataract surgery on the development or progression of age-related macular degeneration (ARMD).
Expedited phaco extracapsular extraction may be more effective at improving visual acuity compared with waiting list control in people with cataract without ocular comorbidities.
When combined with foldable posterior chamber intraocular lens implant (IOL), phaco extracapsular extraction seems more effective than manual large-incision extracapsular extraction at improving vision, and has fewer complications.
This procedure has largely superseded manual large-incision extracapsular cataract extraction in developed countries.
Manual large-incision extracapsular extraction has also been shown to be successful in treating cataracts.
Combined with IOL, manual large-incision extracapsular extraction is significantly better at improving vision compared with intracapsular extraction plus aphakic glasses.
Small-incision manual extracapsular extraction (manual SICS) techniques and phaco extracapsular extraction techniques are similarly beneficial at improving visual acuity for advanced cataracts at 6 months, with few complications.
This finding may be particularly relevant to treatment in developing countries.
Intracapsular extraction is likely to be better at improving vision compared with no extraction, although it is not as beneficial as manual (large or small) incision extracapsular extraction.
The rate of complications is also higher with this technique compared with extracapsular extraction.
In people with glaucoma and cataract, concomitant cataract surgery (phaco or manual large-incision extracapsular extraction) and glaucoma surgery seems more beneficial than cataract surgery alone, in that they both improve vision to a similar extent, but the glaucoma surgery additionally improves intraocular pressure.
We found no trials comparing different types of cataract surgery in people with glaucoma.
In people with diabetic retinopathy and cataract, phaco extracapsular extraction may improve visual acuity and reduce postoperative inflammation compared with manual large-incision extraction.
Performing procedures in the order of cataract surgery first followed by pan retinal photocoagulation may be more effective than the opposite order at improving visual acuity and reducing the progression of diabetic macular oedema in people with cataract and diabetic retinopathy secondary to type 2 diabetes. However, these results come from one small RCT.
One of the possible harms of cataract surgery is cystoid macular oedema, which people with uveitis also frequently suffer from.
We found no trials comparing different types of cataract surgery in people with chronic uveitis.
We don't know whether intravitreal triamcinolone acetonide is more effective than orbital floor injection of triamcinolone acetonide in improving outcomes after cataract surgery in people with chronic uveitis as we found few trials.
Clinical context
About this condition
Definition
Cataracts are cloudy or opaque areas in the lens of the eye (which should usually be completely clear). This results in changes that can impair vision. Age-related (or senile) cataract is defined as cataract occurring in people >50 years of age, in the absence of known mechanical, chemical, or radiation trauma. This review covers treatment for age-related cataract in 4 different populations: people without ocular comorbidity, people with glaucoma, people with diabetic retinopathy, and people with chronic uveitis. Surgery for cataracts in people with glaucoma may affect glaucoma control and, in people with diabetic retinopathy, visual acuity after surgery for cataracts may be lower; the optimal strategy for treating these conditions when they co-exist is not clear. See also reviews on glaucoma, diabetic retinopathy, and uveitis.
Incidence/ Prevalence
Cataract accounts for over 47% of blindness worldwide, causing blindness in about 17.3 million people in 1990.[1] A cross-sectional study in a representative sample of an urban population in New South Wales, Australia, in 1997 (3654 people aged 49–96 years) found that the prevalence of late cataract (of all types) in people aged 65 to 74 years was 21.6%, and in people aged 85 years and older it was 67.3%.[2] This rate excluded those people who had already had cataract surgery. The incidence of non age-related cataract within this population is so small that this can be taken as the effective incidence of age-related cataract. Glaucoma has an overall prevalence of about 2.0% rising to about 4.5% in people aged 70 years and older (the peak age for cataract surgery). In 2006, the 5-year incidence of nuclear cataract with open-angle glaucoma in people aged >50 years was estimated to be 25%.[3]
Aetiology/ Risk factors
Diet, smoking,[4] and exposure to ultraviolet light[5] are thought to be risk factors in the development of age-related cataract. In addition, some people may have a genetic predisposition to development of age-related cataract.[6] [7] Oxidative stress is also thought to be a factor in cataract development,[8] although the impact of dietary anti-oxidants on cataract development remains uncertain.
Prognosis
Age-related cataract progresses with age, but at an unpredictable rate. Cataract surgery is indicated when the chances of significant visual improvement outweigh the risks of a poor surgical outcome. It is not dependent on reaching a specific visual-acuity standard. Cataract surgery may also be indicated where the presence of cataract makes it hard to treat or monitor concurrent retinal disease, such as diabetic retinopathy.
Aims of intervention
To restore vision and to improve quality of life with minimal adverse effects of treatment. Surgery in people with comorbid glaucoma aims to treat the cataract without adversely affecting glaucoma control.
Outcomes
Uncorrected visual acuity; corrected visual acuity; speed and stability of visual rehabilitation; quality of life (including frequency and severity of accidents); adverse effects of treatment, such as endophthalmitis, vitreous loss, cystoid macular oedema, induced astigmatism, and retinal detachment. In people with glaucoma, intraocular pressure is used as a surrogate measure for glaucoma control (with increasing pressure implying increased risk of glaucoma progression). We have reported intraocular pressure in the absence of data on clinical outcomes. In people with cataract and concomitant diabetic retinopathy, final visual-acuity outcomes after cataract surgery may be compromised because of the retinopathy, and the cataract surgery may affect the progression of the retinopathy.
Methods
Clinical Evidence search and appraisal May 2010. The following databases were used to identify studies for this systematic review: Medline 1966 to May 2010, Embase 1980 to May 2010, and The Cochrane Database of Systematic Reviews May 2010 (online) (1966 to date of issue). When editing this review we used The Cochrane Database of Systematic Reviews 2010, issue 3. An additional search within The Cochrane Library was carried out for the Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA). We also searched for retractions of studies included in the review. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the contributor for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews of RCTs and RCTs in any language, single blind unless blinding is impossible, and containing >20 individuals of whom >80% were followed up. The minimum length of follow-up required to include studies was 6 months. We included systematic reviews of RCTs and RCTs where harms of an included intervention were studied applying the same study design criteria for inclusion as we did for benefits. In addition we did an observational harms search for specific harms as highlighted by the contributor, peer reviewer, and editor. We searched for prospective cohort studies with or without a control group. In addition we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the MHRA, which are added to the reviews as required. To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as relative risks (RRs) and odds ratios (ORs). We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).
Table.
GRADE Evaluation of interventions for Cataract.
| Important outcomes | Intraocular pressure, Progression of diabetic retinopathy , Quality of life, Visual acuity | ||||||||
| Studies (Participants) | Outcome | Comparison | Type of evidence | Quality | Consistency | Directness | Effect size | GRADE | Comment |
| What are the effects of surgery for age-related cataract without other ocular comorbidity? | |||||||||
| 1, reported in 4 papers (3400) | Visual acuity | Manual large-incision extracapsular extraction versus intracapsular extraction | 4 | 0 | 0 | –2 | 0 | Low | Directness points deducted for specialist setting and multiple interventions |
| 3 (737) | Visual acuity | Expedited versus delayed phaco extracapsular extraction | 4 | –1 | –1 | 0 | 0 | Low | Quality point deducted for incomplete reporting of results. Consistency point deducted for statistical heterogeneity |
| 2 (545) | Quality of life | Expedited versus delayed phaco extracapsular extraction | 4 | –1 | 0 | –1 | 0 | Low | Quality point deducted for not adequately controlling confounding variables in RCTs. Directness point deducted for reducing generalisability of results by limiting population to women aged >70 years |
| 2 (515) | Visual acuity | Phaco extracapsular extraction versus manual large-incision extracapsular extraction | 4 | 0 | 0 | –1 | 0 | Moderate | Directness point deducted for use of different intraocular lens implants in the 2 intervention arms of the systematic review |
| 1 (108) | Visual acuity | Phaco extracapsular extraction versus manual small-incision extracapsular extraction (SICS) | 4 | –3 | –1 | 0 | 0 | Very low | Quality points deducted for sparse data, incomplete reporting of results, and unstated allocation concealment. Consistency point deducted for no consistent evidence of benefit across different measures of visual acuity |
| What are the effects of treatment for age-related cataract in people with glaucoma? | |||||||||
| 3 (138) | Visual acuity | Concomitant cataract plus glaucoma surgery versus cataract surgery alone | 4 | –2 | 0 | 0 | 0 | Low | Quality points deducted for sparse data and incomplete reporting of results |
| 4 (244) | Intraocular pressure | Concomitant cataract plus glaucoma surgery versus cataract surgery alone | 4 | –1 | 0 | 0 | 0 | Moderate | Quality point deducted for incomplete reporting of results |
| What are the effects of surgical treatments for age-related cataract in people with diabetic retinopathy? | |||||||||
| 1 (46) | Visual acuity | Phaco extracapsular extraction versus manual large-incision extracapsular extraction | 4 | –1 | 0 | 0 | 0 | Moderate | Quality point deducted for sparse data |
| 1 (46) | Progression of diabetic retinopathy | Phaco extracapsular extraction versus manual large-incision extracapsular extraction | 4 | –1 | 0 | 0 | 0 | Moderate | Quality point deducted for sparse data |
| 1 (29, 58 eyes) | Visual acuity | Pan retinal photocoagulation (PRP) followed by cataract surgery versus cataract surgery followed by PRP | 4 | –1 | 0 | –1 | 0 | Low | Quality point deducted for sparse data. Directness point deducted for limiting population to people with type 2 diabetes |
| 1 (29, 58 eyes) | Progression of diabetic retinopathy | Pan retinal photocoagulation (PRP) followed by cataract surgery versus cataract surgery followed by PRP | 4 | –1 | 0 | –1 | 0 | Low | Quality point deducted for sparse data. Directness point deducted for limiting population to people with type 2 diabetes |
| What are the effects of surgical treatments for age-related cataract in people with chronic uveitis? | |||||||||
| 1 (40) | Visual acuity | Injection of triamcinolone acetonide directly into the vitreous compared with orbital floor injection at the end of cataract surgery | 4 | –3 | 0 | 0 | 0 | Very low | Quality points deducted for sparse data, pseudo-randomisation, and incomplete reporting of results |
We initially allocate 4 points to evidence from RCTs, and 2 points to evidence from observational studies. To attain the final GRADE score for a given comparison, points are deducted or added from this initial score based on preset criteria relating to the categories of quality, directness, consistency, and effect size. Quality: based on issues affecting methodological rigour (e.g., incomplete reporting of results, quasi-randomisation, sparse data [<200 people in the analysis]). Consistency: based on similarity of results across studies. Directness: based on generalisability of population or outcomes. Effect size: based on magnitude of effect as measured by statistics such as relative risk, odds ratio, or hazard ratio.
Glossary
- Cystoid macular oedema
A condition in which fluid accumulates in cyst-like spaces in the outer plexiform layer of the retina. It is usually self-limiting, but can result in permanent reduction in visual acuity. It is thought to be associated with breakdown of the blood–retina barrier and is more common after complicated surgery. It is also more common in patients with diabetes or uveitis.
- Endophthalmitis
Inflammation of some or all parts of the eye. It is normally, if not qualified as such in this review, taken to be caused by postoperative intra-ocular infection.
- Induced astigmatism
Change in refractive power of the cornea along different meridians as a result of the change in shape caused by surgical incisions.
- Intracapsular extraction
is removal of the entire lens and capsule with local anaesthesia (injection around the eye, or drops).
- Intraocular lens implant
The most common material used for the optic of intraocular lenses worldwide is poly(methylmethacrylate), which is rigid at room or body temperature and requires an incision of at least 5 mm to 6 mm for insertion. In resource-rich countries, other materials, such as silicone or different types of acrylic, are increasingly being used for intraocular lenses. These materials are plastic at room temperature and can be rolled or folded in half, allowing insertion through incisions of 3.5 mm or less; a small number of intraocular lenses can now be inserted through incisions of 2 mm or less.
- Low-quality evidence
Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
- Manual extracapsular extraction
Removal of the anterior capsule and lens contents (nucleus and cortex) en bloc without using ultrasound or other methods of breaking up the nucleus before removal with local anaesthesia (injection around the eye, or drops). The posterior capsule is left behind. This technique has in the past required a large incision (chord length 9–10 mm, arc length 11–13 mm) and is commonly referred to simply as 'extracapsular extraction'. For clarity, we will refer to this procedure as manual large-incision extracapsular extraction in this review. Recent years have seen the development of smaller-incision sutureless techniques to achieve the same aim. This is referred to as manual small-incision extracapsular extraction or, more commonly, just 'manual SICS'.
- Moderate-quality evidence
Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
- Phaco extracapsular extraction (phacoemulsification)
Use of ultrasound to break up the lens nucleus for less invasive extraction through a smaller incision with local anaesthesia (injection around the eye, or drops). The posterior capsule is left behind as in manual extracapsular extraction. This technique is commonly referred to as "phacoemulsification".
- Posterior capsule opacification
is opacification of the posterior capsule (which is left behind at the end of an extracapsular or phaco cataract extraction). When it occurs it is usually progressive and can result in reduced visual function. Grading: I = minor peripheral opacity only; II = present in central zone with mild obscuration of fundus detail; III = as II but with marked obscuration of fundus detail.
- Snellen visual acuity
The Snellen chart usually includes letters, numbers, or pictures printed in lines of decreasing size, which are read or identified from a fixed distance; distance visual acuity is usually measured from a distance of 6 m (20 feet). The Snellen visual acuity is written as a fraction: 6/18 means that from 6 m away the best line that can be read is a line that could normally be read from a distance of 18 m away.
- Very low-quality evidence
Any estimate of effect is very uncertain.
- Vitreous loss
Loss of the vitreous gel that normally fills the posterior segment (behind the lens) of the eye. Its loss during intracapsular cataract surgery, or in the presence of rupture of the posterior capsule in extracapsular surgery, can give rise to potentially sight-threatening complications.
Age-related macular degeneration
Glaucoma
Uveitis (acute anterior)
Disclaimer
The information contained in this publication is intended for medical professionals. Categories presented in Clinical Evidence indicate a judgement about the strength of the evidence available to our contributors prior to publication and the relevant importance of benefit and harms. We rely on our contributors to confirm the accuracy of the information presented and to adhere to describe accepted practices. Readers should be aware that professionals in the field may have different opinions. Because of this and regular advances in medical research we strongly recommend that readers' independently verify specified treatments and drugs including manufacturers' guidance. Also, the categories do not indicate whether a particular treatment is generally appropriate or whether it is suitable for a particular individual. Ultimately it is the readers' responsibility to make their own professional judgements, so to appropriately advise and treat their patients. To the fullest extent permitted by law, BMJ Publishing Group Limited and its editors are not responsible for any losses, injury or damage caused to any person or property (including under contract, by negligence, products liability or otherwise) whether they be direct or indirect, special, incidental or consequential, resulting from the application of the information in this publication.
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