What is acute primary angle closure?
Acute primary angle closure is a rare condition caused by changes to structures at the front of the eye. The drainage angle becomes very narrow, which blocks fluid drainage and causes raised eye pressure (intraocular pressure). People with acute primary angle closure may experience severe eye pain, blurred vision, redness, and clouding of the cornea (the clear front window of the eye) very suddenly. If left untreated, the condition can lead to blindness due to irreversible damage to the nerve at the back of the eye.
How is acute primary angle closure treated?
Acute primary angle closure is treated by reducing pressure inside the eye and opening the drainage angle. The pressure is initially lowered using topical and oral medications, which provide protection for the nerve at the back of the eye. Once the initial episode settles and the cornea becomes clearer, a more permanent treatment is required. Laser peripheral iridotomy is an established treatment that uses a laser to create a small hole in the iris (the colored part of the eye), which redirects the flow of fluid at the front of the eye, allowing the drainage blockage to open. Removal of the lens (also called cataract when it becomes cloudy) has recently been proposed as a more effective permanent treatment for acute primary angle closure. This is because it also reduces crowding of the structures at the front of the eye and opens the drainage angle.
What did we want to find out?
Acute primary angle closure is one of the few eye emergencies and can cause permanent sight loss if left untreated. Laser peripheral iridotomy is a useful and well-established treatment, but despite it seeming to work well initially, some people are still at risk of developing chronic glaucoma (eye conditions that damage the optic nerve) after the acute attack is treated. There has been increasing interest in lens extraction for the treatment for other types of primary angle closure disease (e.g. chronic angle closure glaucoma). We wanted to find out whether it provides better outcomes than the standard treatment of laser peripheral iridotomy for acute primary angle closure, both in the short and longer term.
What did we do?
We searched for studies that examined lens extraction compared with laser peripheral iridotomy for acute primary angle closure. We compared and summarized the results of the studies and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found two studies that involved 99 participants with acute primary angle closure. Both studies followed participants for up to 24 months.
When compared against laser therapy, the evidence suggests that lens extraction:
1. may increase the proportion of participants with intraocular pressure control at 18 to 24 months;
2. may result in a reduction in intraocular pressure at 12 months;
3. may result in a slight reduction in the number of intraocular pressure-lowering medications required at 18 months, but the difference may not be clinically relevant;
4. may be safe (evidence is from phacoemulsification performed by experienced surgeons).
When compared against laser therapy, it is unclear whether lens extraction:
1. reduces the proportion of participants with one or more recurrent acute primary angle closure episodes within 24 months;
2. reduces the need for further intraocular pressure-lowering surgery within 24 months;
3. improves drainage angle examination findings at six months.
What are the limitations of the evidence?
We have little confidence in the evidence for lens extraction in acute primary angle closure because not all of the studies provided data for all of their prespecified outcomes, or they reported data on outcomes that they did not prespecify. Also, the included studies were very small, and there were insufficient studies to be certain about the results. Certain study design characteristics might also have interfered with the effects of treatment with lens extraction or laser peripheral iridotomy.
How up-to-date is the evidence?
The evidence is current to 10 January 2022.
Low certainty evidence suggests that early lens extraction may produce more favorable outcomes compared to initial LPI in terms of IOP control. Evidence for other outcomes is less clear. Future high-quality and longer-term studies evaluating the effects of either intervention on the development of glaucomatous damage and visual field changes as well as health-related quality of life measures would be helpful.
Acute primary angle closure (APAC) is a potentially blinding condition. It is one of the few ophthalmic emergencies and carries high rates of visual morbidity in the absence of timely intervention. Laser peripheral iridotomy (LPI) has been the standard of care thus far. However, LPI does not eliminate the long-term risk of chronic angle closure glaucoma and other associated sequelae. There has been increasing interest in lens extraction as the primary treatment for the spectrum of primary angle closure disease, and it is as yet unclear whether these results can be extrapolated to APAC, and whether lens extraction provides better long-term outcomes. We therefore sought to evaluate the effectiveness of lens extraction in APAC to help inform the decision-making process.
To assess the effect of lens extraction compared to LPI in the treatment of APAC.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2022, Issue 1), Ovid MEDLINE, Ovid MEDLINE E-pub Ahead of Print, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily (January 1946 to 10 January 2022), Embase (January 1947 to 10 January 2022), PubMed (1946 to 10 January 2022), Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to 10 January 2022), ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search. We last searched the electronic databases on 10 January 2022.
We included randomized controlled clinical trials comparing lens extraction against LPI in adult participants ( ≥ 35 years) with APAC in one or both eyes.
We used standard Cochrane methodology and assessed the certainty of the body of evidence for prespecified outcomes using the GRADE approach.
We included two studies conducted in Hong Kong and Singapore, comprising 99 eyes (99 participants) of predominantly Chinese origin. The two studies compared LPI with phacoemulsification performed by experienced surgeons. We assessed that both studies were at high risk of bias. There were no studies evaluating other types of lens extraction procedures.
Phacoemulsification may result in an increased proportion of participants with intraocular pressure (IOP) control compared with LPI at 18 to 24 months (risk ratio (RR) 1.66, 95% confidence interval (CI) 1.28 to 2.15; 2 studies, n = 97; low certainty evidence) and may reduce the need for further IOP-lowering surgery within 24 months (RR 0.07, 96% CI 0.01 to 0.51; 2 studies, n = 99; very low certainty evidence). Phacoemulsification may result in a lower mean IOP at 12 months compared to LPI (mean difference (MD) −3.20, 95% CI −4.79 to −1.61; 1 study, n = 62; low certainty evidence) and a slightly lower mean number of IOP-lowering medications at 18 months (MD −0.87, 95% CI −1.28 to −0.46; 1 study, n = 60; low certainty evidence), but this may not be clinically significant. Phacoemulsification may have little to no effect on the proportion of participants with one or more recurrent APAC episodes in the same eye (RR 0.32, 95% CI 0.01 to 7.30; 1 study, n = 37; very low certainty evidence). Phacoemulsification may result in a wider iridocorneal angle assessed by Shaffer grading at six months (MD 1.15, 95% CI 0.83 to 1.47; 1 study, n = 62; very low certainty evidence).
Phacoemulsification may have little to no effect on logMAR best-corrected visual acuity (BCVA) at six months (MD −0.09, 95% CI −0.20 to 0.02; 2 studies, n = 94; very low certainty evidence). There was no evidence of a difference in the extent of peripheral anterior synechiae (PAS) (clock hours) between intervention arms at 6 months (MD −1.86, 95% CI −7.03 to 3.32; 2 studies, n = 94; very low certainty evidence), although the phacoemulsification group may have less PAS (degrees) at 12 months (MD −94.20, 95% CI −140.37 to −48.03; 1 study, n = 62) and 18 months (MD −127.30, 95% CI −168.91 to −85.69; 1 study, n = 60).
In one study, there were 26 adverse events in the phacoemulsification group: intraoperative corneal edema (n = 12), posterior capsular rupture (n = 1), intraoperative bleeding from iris root (n = 1), postoperative fibrinous anterior chamber reaction (n = 7), and visually significant posterior capsular opacification (n = 5), and no cases of suprachoroidal hemorrhage or endophthalmitis. There were four adverse events in the LPI group: closed iridotomy (n = 1) and small iridotomies that required supplementary laser (n = 3). In the other study, there was one adverse event in the phacoemulsification group (IOP > 30 mmHg on day 1 postoperatively (n = 1)), and no intraoperative complications. There were five adverse events in the LPI group: transient hemorrhage (n = 1), corneal burn (n = 1), and repeated LPI because of non-patency (n = 3).
Neither study reported health- or vision-related quality of life measures.