World First: A/Prof. Chandra Bala Laser-Lens Removal
Ophthalmologist and Clinical A/Professor Chandra Bala (M.Sc. Hons, MBBS Hons/PhD) has become the first ophthalmologist to use a cataract surgery laser to remove an artificial lens arising from cataract surgery complications.
Intraocular lens (IOL) explantations are performed to address issues such as IOL opacification, dysphotopsia, and refractive surprise. Often a challenging procedure, ideally, the IOL is removed through a small clear corneal incision (CCI) without inducing astigmatism or damaging the capsular bag, zonular fibres, or corneal endothelium.
The procedure is particularly challenging in cases with large hydrophilic plate-haptic IOLs.
A variety of techniques, including the use of scissors, are used to make small incisions to remove IOLs, which, being synthetic, are much harder than natural lenses. Femtosecond laser has also been used, however A/Professor Bala reports this generates gases, which at high laser energy are toxic and could be carcinogenic. At lower energy levels, toxic gases were not detectable, however he reported it was possible that during the in vitro testing, gasses escaped before collection.
A/Professor Bala and colleagues investigated the appropriate laser settings for IOL fragmentation in an artificial chamber with a human donor cornea. The gasses generated were trapped in the artificial anterior chamber and analysed for safety. He then performed the procedure to transect hydrophilic acrylic intraocular lenses (IOLs) in two difficult cases; a 59-year-old patient who suffered from a retinal detachment a few years after a successful cataract operation, and an 89-year-old patient who had a traumatised lens.
A/Professor Bala reported, “at 8 μJ with 3mm spot separation and 6mm line separation, no charring occurred and there was no increase in total organic carbon. In vivo, the IOLs were successfully transected in the capsular bag (Case one, opaque IOL) and the sulcus (Case two, subluxated IOL post-pneumatic displacement of submacular hemorrhage) and explanted through a clear corneal incision (w3.0 mm). At three months, in Case one, the corrected distance visual acuity (CDVA) improved from 6/24 to 6/5, astigmatism improved by 0.23 diopters, and endothelial cell density (ECD) remained unchanged (1935 to 2210 cells/mm2); in Case two, the CDVA was hand motion, astigmatism remained unchanged, and ECD decreased (1960 to 1600 cells/mm2), possibly as a result of complex surgery. Femtosecond IOL transection and explantation may be a clinically safe and feasible option for surgeons.”
A/Professor Bala said this new breakthrough may renders scissors unnecessary, reduce patient trauma and cut recovery time down to just one day.
Despite being a preliminary study he said it raises the possibility of applying this technique to IOLs of both hydrophobic and hydrophilic material, however he did not recommend it for all IOLS that need to be explanted.
“The technique has been applied in vitro to hydrophobic acrylic IOLs. However, energy settings are likely to vary, particularly for polymethyl methacrylate (PMMA) IOLs, which are harder (personal in vitro experience). The by-products of such lasers should be determined prior to applying the laser to new IOLs… Several techniques for explanting IOLs can provide equally good results. However, large IOLs and more complicated IOL designs may benefit from improving this technology.”
Dr. Bala concluded, “we found that low-energy femtosecond laser transection of IOLs is possible in the clinical setting. It can be performed safely in difficult cases and achieve quick healing.”
A/Professor Chandra Bala’s work recently featured on the cover of a leading global medical journal, the Journal of Cataract & Refractive Surgery. Additionally, in June he was a runner up in the Cataract Complications/ Challenging Cases category at the Asia Pacific Association of Cataract & Refractive Surgeons (APACRS) for this world-first laser lens removal surgery discovery.
Source: mivision | 28 July 2017