Refractive lens exchange may be an option in highly myopic presbyopes
Daith' î hAnluain
in Chester, UK

REFRACTIVE Lens Exchange for high myopia appears to be safe and effective in the longer term, suggests a new study presented at the annual UKISCRS conference. The study followed 28 eyes of fifteen patients with high myopia who were treated at the Sunderland Eye Infirmary between 1998 and 2001. All underwent refractive lens exchange with for correction of high myopia.

Mean preoperative spherical equivalent refraction was -11.83D (range -6.25D to -24D). Mean patient age was 58 (range 44 to 83) years. Some 64% (18 eyes) had early lens changes and 43 % (12 eyes) had myopic retinal changes but prophylactic retinal laser treatment was not necessary. The axial lengths of the eyes were greater than 26 mm in all cases. "Because all patients were in the presbyopic age range and most of them were already developing early lens opacity, the most appropriate procedure was refractive lens exchange," said Dimitris Pimenides, Specialist Registrar at Sunderland Eye Infirmary.

After a mean follow-up of 23.3 months (range 12 to 42 months), BCVA improved by a mean of 1.4 Snellen lines, no eyes lost any lines of BCVA and UCVA was greater than 6/12 in 81.48% of cases. Postoperative mean spherical equivalent was -0.09D (range +2D to -2.5D). Postoperative refraction was within ±1.0D of target in 82% of cases with one eye requiring an IOL exchange and one eye requiring a piggyback IOL.

There were no cases of cystoid macular oedema. Subsequent retinal detachment occurred in one eye of a 50-year-old patient who had an accident, and underwent successful surgical repair, while the fellow eye had prophylactic laser treatment. Six eyes (17.9%) required YAG capsulotomy. All eyes underwent a straightforward phacoemulsification with clear corneal incision in most eyes. In nine astigmatic eyes the phaco incisions were made on the steepest meridian while three eyes underwent limbal relaxing incisions. A posterior capsule tear occurred in one eye and the patient underwent anterior vitrectomy. No other complications occurred.

"Our current data suggests that the refractive lensectomy using small incision phaco, in the presence of early lens changes in highly myopic presbyopes, is effective and safe in the medium term." This research project is ongoing, so patients are invited to re-attend the clinic every year or two, co-author, Jean-Pierre Danjoux FRCOphth, also at Sunderland, told Eurotimes. "Refractive lens exchange and IOL insertion is an effective way of correcting high myopia in presbyopic patients seeking refractive surgery who may be outside the limits treatable by LASIK, or who have early cataracts. One of the biggest concerns with this type of procedure in high myopes is the risk of retinal detachment following surgery.

"We know that high myopes already have a higher incidence of retinal detachment than patients with minimal refractive error (even without surgery). Unfortunately, it is difficult to get good demographic data regarding the true rate of retinal detachment in high myopes in general. There have been several studies published looking at the results of refractive lens exchange in high myopes with variable follow up time," Said Mr Danjoux. Mr. Danjoux says that the studies show retinal detachment ranging from zero to over 8%, with greater incidence occurring the longer patients are followed and in those earlier studies that feature larger surgical incisions.

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We would expect a slight increase in retinal detachment rate with time as this is a group of patients already at risk of this. We want to know however if this incidence rate is significantly increased above what we might expect had these patients not undergone surgery." The larger incisions of earlier studies may play a role, says Mr Danjoux, adding that modern small incision phacoemulsification is much safer.

We hope to show that there is no significant increase in risk of retinal detachment developing following refractive lens exchange and IOL insertion in this group of high myopes over time." Mr Danjoux noted that another risk factor for retinal detachment is YAG capsulotomy. "So it is important that we look at the PCO rate and YAG rate in these patients as well as subset analysis of retinal detachment in these patients. To date we have had no cases of retinal detachment following YAG capsulotomy." In questions from the floor, Dr. Pimenides was asked about the state of the vitreous before surgery. He replied that posterior vitreous detachment was present in approximately 60 % of cases preoperatively.

r. Pimenides said he would be very reluctant to recommend clear lens extraction in younger patients because the complication rate is significantly higher. While the team used a variety of lenses, the majority of them were Acrysof. "I would not entirely agree with Dr Pimenides comments that the complication rate is significantly higher," said Mr. Danjoux. "Refractive lens exchange in young patients will result in a loss of accommodation which they don't like. If unsuitable for laser surgery, I would favour a phakic implant in a young patient as this allows them to maintain accommodation." Dr Pimenides did not agree with the suggestion that it might be better to aim for -1.0 D rather than emmetropia.

"Our achieved post op refraction was from -2.5 D to +2.0 D (Mean -0.09 D, SD 0.95). It was suggested that if our target refraction were low minus, instead of emmetropia, we would have avoided leaving a high myope with +2.0 D postoperative refraction. Emmetropia is the ultimate goal of the operation. The fact that is not achieved suggests that our pre-op calculations are not yet perfect in high myopes. We can try to improve our calculations, surgical technique and formulae but deliberately aiming at something that is undesirable by the patient may not be good practice. It is true that high myopes prefer to be left low minus rather than low plus. If we had aimed for -2.0 D, the +2.0 D patient would be emmetropic but the -2.5 D (at the other end of the spectrum) would be -4.5 D, requiring an additional refractive procedure."Dr Pimenides said that he hopes that if the safety of this procedure can be improved, it will be used more widely.

Dimitris Pimenides SpR
Sunderland Eye Infirmary
dpimenides@doctors.org.uk

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