SMILE, FS-LASIK and the EOZ
How do small-incision lenticule extraction (SMILE®) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) compare in terms of postoperative effective optical zone (EOZ)? A retrospective study compared the effects of both surgeries on the EOZ, that is, the area of corneal surface with a high level of optical quality and the portion of the ablation that achieves full correction. The study of 76 eyes of 76 patients found that both SMILE and FS-LASIK resulted in EOZ reduction during correction of myopia. However, SMILE resulted in less reduction than FS-LASIK and was associated with corneal asphericity changes and epithelial thickening. This was the first study to look at this question. The researchers call for further studies to look at the effect of EOZ on visual quality.
J Hou et al., JCRS, “Comparison of effective optical zone after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis for myopia”, Vol 44, #10, 1179-1185.
Best iris-claw IOL implantation
Iris-claw IOL implantation carries lower risk for endothelial damage and glaucoma than angle-supported lens implantation, but is considered a more difficult surgery. A single surgeon evaluated the outcomes of 76 iris-claw IOL implantations, comparing different surgical techniques. The results were analysed by the incision type (corneal versus scleral tunnel) and lens position (peripapillary versus retropupillary). All patients had significant improvements in distance visual acuity.
Mean uncorrected distance acuity was significantly better in the scleral tunnel incision group, with significantly less surgically induced astigmatism seen in that group. Although endothelial cell loss was lower in the retropupillary position, the difference was not significant.
A Hernández Martínez et al. JCRS, “Iris-claw intraocular lens implantation: Efficiency and safety according to technique”, Vol 44, #10, 1186-1191.
Residual astigmatism and UDVA
Residual astigmatism after multifocal IOL implantation has been shown to reduce the effectiveness of that IOL type. Astigmatism has also been shown to worsen visual acuity. However, residual astigmatism following implantation of both monofocal and multifocal IOLs has an impact on uncorrected distance visual acuity (UDVA), a large database analysis suggests. A review of 1,919 records collected at a website designed to assist with postoperative analysis of residual astigmatism after toric IOL implantation indicated that residual refractive astigmatism had a similar effect on worsening UDVA in eyes with monofocal or multifocal toric IOLs, regardless of whether the latter were diffractive or extended depth-of-focus IOLs. The axis of the residual refractive astigmatism (grouped into WTR, ATR and oblique astigmatism) did not make a clinical or statistical difference in visual acuity in patients with a monofocal toric IOL.
JP Berdahl et al., JCRS, “Effect of astigmatism on visual acuity after multifocal versus monofocal intraocular lens implantation”, Vol 44, #10, 1192-1197.
