ArticlesRandomised controlled trial of anterior-chamber intraocular lenses
Introduction
There are estimated to be 16 million people bilaterally blind with cataracts in the world in 1990, most of whom live in rural areas of developing countries where expert surgical resources are scarce.1 Cataracts can be taken out in two ways (see glossary): intracapsular cataract extraction (ICCE) is simple and quick and involves removal of the whole lens; extracapsular extraction (ECCE) removes the lens contents only, leaving the posterior lens capsule intact. To correct for not having a lens in the eye, (aphakia), either an intraocular lens can be implanted during surgery or the patient can use spectacles or contact lenses after surgery.
In industrialised countries, the usual surgical technique is ECCE followed by implantation of a posterior chamber lens (PCIOL) in the remaining lens capsule. Surgery is done with an operating microscope. This technique preserves the structural integrity of the eye, prevents prolapse of the vitreous body into the anterior chamber, and reduces the risk of retinal detachment. The disadvantage is that in some patients the posterior capsule will opacify and further intervention will be needed.
Most eye surgeons in rural Africa and Asia have been trained to do ICCE. In many cases, they do not have access to an operating microscope and use a magnifying loupe to do the operation. Patients receive spectacles after the operation. These spectacles are heavy, distort vision, and are easily broken. Surveys in Africa2 and in Asia3 have shown that uncorrected aphakia is one of the most important causes of blindness.
It is accepted that cataract surgeons in developing countries should use intraocular lenses to overcome the difficulties of aphakic spectacles, but there is no agreement as to whether it is justified to retrain surgeons experienced in ICCE in the ECCE with PCIOL technique, since this procedure is relatively expensive and usually requires an operating microscope.
The simplest method of using a lens implant after ICCE is to place it in front of the iris in the anterior chamber of the eye. Older anterior-chamber intraocular lens (ACIOL) implants had a bad reputation because of faulty design and manufacture.4, 5 Studies in industrialised countries, where ACIOLs are used when the posterior capsule is ruptured at operation, suggest that modern multiflex open-loop ACIOLs are well tolerated.6, 7, 8, 9, 10 There is currently insufficient evidence to justify their widescale use as a primary procedure in the developing world.
After a pilot study,11 we undertook a randomised controlled trial at Lahan Eye Hospital, southern Nepal, comparing ICCE surgery with a multiflex open loop ACIOL with ICCE surgery and spectacles. Our hypothesis was that ACIOLs would give better vision after surgery but might be associated with more complications leading to blindness. Lahan is a rural eye hospital with three ophthalmologists doing approximately 12 000 eye operations each year. This paper describes visual outcome 1 year after surgery; analyses of clinical data, quality of life, and cost effectiveness will be published elsewehere.
Section snippets
Protocol
Patients attending Lahan Eye Hospital were eligible if aged 40–64 years, with bilateral cataract reducing vision to 6/36 or less in both eyes, and living within accessible districts. Exclusion criteria were known pre-existing ocular disease, hypertension, or diabetes. Patients gave informed consent to participate in the trial, which was approved by the Medical Research Council of Nepal.
ICCE with an ACIOL was compared with ICCE with aphakic spectacles. Surgery was done under local anaesthetic by
Participants flow and follow up
Figure 1 shows the trial profile. Of 2908 eligible patients presenting between February, 1992, and March, 1995, 379 were excluded for medical reasons and 529 declined: 2000 were randomised—1002 to ICCE and ACIOL and 998 to ICCE only (controls), all of whom received the assigned procedure. Table 1 shows the age, sex, and preoperative visual acuity in the two groups. The median (range) time taken to do the surgery (mins between placing the superior rectus muscle suture and closing the wound) was
Discussion
This study shows that multiflex open-loop ACIOLs can be implanted safely by experienced ophthalmologists after routine ICCE. Approximately 5% of patients had an acuity of less than 6/60 in the trial eye 1 year after surgery. In both groups the main cause of poor visual outcome was uncorrected refractive error. In only 2% of people was the reduced vision due to surgical complications. By contrast with most surgical trials, this study had a relatively large sample size providing reasonably
GLOSSARY
- ICCE
- =intracapsular cataract extraction
- ECCE
- =extracapsular cataract extraction
- PCIOL
- =posterior chamber intraocular lens
- ACIOL
- =anterior chamber intraocular lens
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