Eyeworld

In the journal: August 2019 Phacoemulsification with the big bubble DALK technique: a variant of the triple procedure Roberto Pinto Coelho, MD, André Messias, MD When patients have ectasia and cataracts together, this can create surgical hurdles. In most cases, surgeons take a two-step approach, first performing the corneal graft, then coming back to undertake cataract surgery. Sometimes a triple procedure in which the cataract surgery complete with intraocular lens implantation is done in conjunction with graft surgery. The visual disability period with this approach is shorter than for the two-step technique, and costs are lower for the patient. In some cases a triple procedure involving the big bubble DALK technique followed by phacoemulsification is performed. However, rupture of Descemet's membrane is the danger here, requiring extreme caution. Investigators instead performed the triple procedure with phacoemulsi- fication first then employed the big bubble DALK technique for placing a corneal graft. Decentration measurements using the tangential curvature topography and Scheimpflug tomography pachymetry difference maps after small-incision lenticule extraction procedure Byunghoon Chung, MD, Hun Lee, MD, Cynthia Roberts, PhD, David Sung Yong Kang, MD, Dan Reinstein, MD, Seung Ki Jean, MR, Eung Kweon Kim, MD, PhD, Kyoung Yul Seo, MD, Tae-im Kim, MD In this retrospective case series involving 155 eyes, investigators considered what happened after the small-incision lenticule extraction (SMILE) procedure to the agreement between tangential curvature topography generated by a Keratron Scout (Optikon) and pachymetry difference maps made for each eye via the Pentacam system (Oculus). Investigators found that with the tangential curvature difference maps, there was a 0.27 mm magnitude of decentration versus a 0.26 mm magnitude with the pachymetry difference maps, which was not significantly different. The vector difference in pupillary offset between pre- and postoperative measurements from the pachymetry difference map significantly correlated with the magnitude of vector differences of decentration between the two maps. The vector difference plot showed a wide distribution spread to all four quadrants, demonstrating a lack of agreement. Investigators concluded that while there was no significant difference between the scalar magnitude of decentration with the tangential topogra- phy difference maps and pachymetry difference maps, the vector differences were apparent, with increasing pupillary offset resulting in increasing error present in the pachymetry maps, indicating a lack of agreement. Optical behavior of the eye implanted with extreme intraocular lens powers Renan Oliveira, MD, Liberdade Salerno, MD, Michael Mimouni, MD, Ana Belén Plaza-Puche, MSc, Jorge Alió, MD The aim in this prospective comparative study was to examine how very low- and high-powered spherical monofocal lenses placed after cataract surgery impacted ocular aberrations from the surgery. In the study, 88 eyes in which a spherical monofocal IOL was implanted following cataract surgery were put in 1 of 3 groups based on the power of their IOL. Group 1 included lenses rang- ing from +20 D to +23 D, while group 2 included those with less than +10 D of power. Those in group 3 had lenses with +29 D of power or more. At the 3-month mark investigators found that in terms of refractive error, corneal aberrometry, or total ocular higher-order aberrations, there were no differences among the groups at any of the pupil diameters considered. When it came to spherical aberration, they likewise found that with a 4-mm pupil there was no significant differenc- es among the groups. However, with either a 4.5-mm or 5.0-mm pupil, group 2 had significantly lower spherical aberration compared to group 1 or group 3. When group 1 and 3 were compared, spherical aberration was not significantly different no matter the pupil diameter. Contrast sensi- tivity was not lowered as a result of higher spherical aberration. The conclusion reached was that high-powered positive IOLs only induce a negligible, clinically insignificant amount of aberrations, despite theoretical evidence to the contrary. compare baseline refractive error, axial eye length, and central corneal thickness in the keratoconus and healthy group, to see how comparable these two groups are. The main limitation of this study is the fact that measurements were done in a group that already displayed signs of keratoconus. The findings may therefore not reflect cor- neal biomechanics that may lead to kerato- conus but instead only those present once disease is manifest. An additional limitation is the baseline variability in anterior chamber volume and IOPG in both the healthy and the keratoconus groups, as well as posterior corneal astigmatism in the keratoconus group. This variability may be masking significant differences between time points for the variables emphasized in this study. The table in the study reveals a wider range for several variables in the keratoconus group, including anterior astigmatism, suggesting additional variables may be identified in a sufficiently powered study. Future studies, if adequately powered, would also allow for additional stratification based on patient characteristics, including severity of astigmatism, refractive error, base- line IOPG, and even the presence of genetic mutations. These analyses could identify factors that increase the risk of keratoconus progression in the setting of eye rubbing in specific keratoconus populations. It was noted in the study that 2 of the 5 keratoconus eyes that had follow-up Scheimpflug analysis demonstrated disease progression. However, further description of parameters of those two eyes that progressed were not provided. It would be interesting to monitor more subjects over time to help identify factors that predict progression of keratoconus and, in particular, whether response to eye rubbing in keratoconus eyes could provide any additional barometer of likelihood of progression in these patients. The study results show that eye rub- bing affects keratoconus eyes in a different way than healthy eyes and further postulate that specifically the changes in the posteri- or cornea may explain why eye rubbing is considered a risk factor for development of keratoconus.

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