Refractive Surgery

Refractive Surgery Publications

Zhang C, Ding H, He M, Liu L, Liu L, Li G, Niu B, Zhong X. Comparison of Early Changes in Ocular Surface and Inflammatory Mediators between Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction. PLoS One 2016;11(3):e0149503.Abstract

PURPOSE: To evaluate the short-term changes in ocular surface measures and tear inflammatory mediators after femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) procedures. METHODS: Eighteen subjects (18 eyes) underwent FLEx and 23 subjects (23 eyes) underwent SMILE in this single-center and prospective study. Central corneal sensitivity, Schirmer I test (SIT), noninvasive tear breakup time (NI-TBUT), tear meniscus height, corneal fluorescein (FL) staining, and ocular surface disease index (OSDI) were assessed in all patients. Concentrations of interleukin-1α (IL-1α), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) in collected tears were measured by multiplex antibody microarray. RESULTS: Central corneal sensitivity was reduced in both groups, but the scores in the SMILE group were higher than those in the FLEx group at all time points postoperatively (P<0.01). Lower FL scores and longer NI-BUT were observed in the SMILE group 1 week after surgery (P<0.05). OSDI scores in both groups increased rapidly at 1 day and 1 week postoperatively, then returned to their preoperative levels within 1 month (P<0.05). There were no significant differences in SIT or tear meniscus height between the two groups. Lower and faster recovery of tear NGF, TGF-β1 and IL-1α concentration were found in the SMILE group compared to the FLEx group postoperatively. No significant difference was found in tear TNF-α, IFN-γ and MMP-9 for either group before or after surgery. Tear NGF, TGF-β1 and IL-1α show a correlation with ocular surface changes after FLEx or SMILE surgery. CONCLUSION: SMILE has superiority over FLEx in early ocular surface changes and NGF, TGF-β1 and IL-1α may contribute to the process of ocular surface recovery. TRIAL REGISTRATION: ClinicalTrials.gov NCT02540785.

Veldman PB, Dye PK, Holiman JD, Mayko ZM, Sáles CS, Straiko MD, Stoeger CG, Terry MA. Stamping an S on DMEK Donor Tissue to Prevent Upside-Down Grafts: Laboratory Validation and Detailed Preparation Technique Description. Cornea 2015;34(9):1175-8.Abstract

PURPOSE: To report endothelial cell loss (ECL) caused by a novel S-stamp preparation technique for Descemet membrane endothelial keratoplasty (DMEK). METHODS: Six cadaveric human corneas were prepared for DMEK transplantation using a single standardized technique, including the application of a dry ink gentian violet S-stamp to the stromal side of Descemet membrane. Endothelial cell death was evaluated and quantified using computerized analysis of vital dye staining. RESULTS: ECL caused by the S-stamp was 0.6% (range 0.1%-1.0%), which comprised less than one-tenth of the total ECL caused by our preparation of the DMEK graft from the start to finish, including recovery, prestripping, S-stamping, and trephination (13.7% total ECL, range 9.9%-17.6%). CONCLUSIONS: Our novel S-stamp donor tissue preparation technique is intuitive to learn and holds the promise of preventing iatrogenic primary graft failure due to upside-down grafts without causing unacceptable increases in ECL.

Theophanous C, Jacobs DS, Hamrah P. Corneal Neuralgia after LASIK. Optom Vis Sci 2015;92(9):e233-40.Abstract

PURPOSE: To illustrate that corneal neuralgia may be the basis for refractory dry eye syndrome after laser-assisted in situ keratomileusis (LASIK). METHODS: The methodology used is that of a retrospective medical record review of a small case series. RESULTS: Three male patients, aged 30 to 48 years, referred in 2012 for dry eye syndrome refractory to treatment within 1 year of LASIK or LASIK enhancement are reported. Each patient gave history of eye pain, light sensitivity, and difficulty with visual activities beginning within 2 months of LASIK or LASIK enhancement. Best-corrected visual acuity was 20/15 or 20/20 in each of the six eyes. Tear-centered models and metrics did not explain persistent symptoms, which was consistent with inadequate response to standard dry eye treatments used before referral and reported here. In vivo confocal microscopy was abnormal at presentation in each case and was followed over time. Treatments undertaken subsequent to referral included autologous serum tears (three cases), PROSE (Prosthetic Replacement of the Ocular Surface Ecosystem) treatment (two cases), and systemic agents for pain, anxiety, or depression (three cases). By the end of 2013, at a mean of 23 months after LASIK or LASIK enhancement, symptoms improved in all three patients. CONCLUSIONS: Patients with persistent dry eye symptoms out of proportion to clinical signs after LASIK have a syndrome that may best be classified as corneal neuralgia. In vivo confocal microscopy can be informative as to the neuropathic basis of this condition. In keeping with current understanding of complex regional pain syndrome, early multimodal treatment directed toward reducing peripheral nociceptive signaling is warranted to avoid subsequent centralization and persistence of pain. Distinguishing this syndrome from typical post-LASIK dry eye remains a challenge.

Robert M-C, Khreim N, Todani A, Melki SA. Anterior chamber gas bubble emergence pattern during femtosecond LASIK-flap creation. Br J Ophthalmol 2015;99(9):1201-5.Abstract

AIM: To characterise the emergence pattern of cavitation bubbles into the anterior chamber (AC) following femtosecond laser-assisted in situ keratomileusis (LASIK)-flap creation METHODS: Retrospective review of patients undergoing femtosecond LASIK surgery at Boston Laser, a private refractive surgery practice in Boston, Massachusetts, between December 2008 and February 2014. Patient charts were reviewed to identify all cases with gas bubble migration into the AC. Surgical videos were examined and the location of bubble entry was recorded separately for right and left eyes. RESULTS: Five thousand one hundred and fifty-eight patients underwent femtosecond LASIK surgery. Air bubble migration into the AC, presumably via the Schlemm's canal and trabecular meshwork, occurred in 1% of cases. Patients with AC bubbles had an average age of 33±8 years with a measured LASIK flap thickness of 96±21 μm. The occurrence of gas bubbles impaired iris registration in 64% of cases. Gas bubbles appeared preferentially in the nasal or inferior quadrants for right (92% of cases) and left (100% of cases) eyes. This bubble emergence pattern is significantly different from that expected with a random distribution (p<0.0001) and did not seem associated with decentration of the femtosecond laser docking system. CONCLUSIONS: The migration of gas bubbles into the AC is a rare occurrence during femtosecond laser flap creation. The preferential emergence of gas bubbles into the nasal and inferior quadrants of the AC may indicate a distinctive anatomy of the nasal Schlemm's canal.