Cataract surgery in eyes with keratoconus: a review of the current literature.

PURPOSE OF REVIEW: There are an increasing number of keratoconic eyes, requiring cataract surgery. We review the preoperative planning, intraoperative options, and postoperative management that aid in successful outcomes. RECENT FINDINGS: Management of keratoconic eyes requiring cataract surgery requires a multifaceted approach. Preoperatively, corneal crosslinking and intrastromal corneal ring segments can be considered in order to provide stable keratometry values for intraocular lens (IOL) calculations. Deciding between toric and monofocal IOLs requires a thorough evaluation. Intraoperatively, the decision of clear corneal incisions with or without sutures versus scleral incisions is important to mitigate postoperative complications. Postoperatively, irregular astigmatism should be evaluated and updated rigid gas permeable or scleral lenses provided. Patients needing irregular astigmatism correction postoperatively should not have toric IOL implantation; however, in select cases of keratoconus, it is an option. SUMMARY: The use of stabilizing procedures prior to optical biometry can aid in preoperative lens selection and provide predictable surgical outcomes. Decisions on intraoperative wound construction and toric versus monofocal lenses should be based on the severity, regularity, and central nature of the keratoconus. Postoperative use of rigid gas permeable or scleral lenses can help patients achieve their best visual potential.

The locus of heat resistance (LHR) mediates heat resistance in Salmonella enterica, Escherichia coli and Enterobacter cloacae.

Enterobacteriaceae comprise food spoilage organisms as well as food-borne pathogens including Escherichia coli. Heat resistance in E. coli was attributed to a genomic island called the locus of heat resistance (LHR). This genomic island is also present in several other genera of Enterobacteriaceae, but its function in the enteric pathogens Salmonella enterica and Enterobacter cloacae is unknown. This study aimed to determine the frequency of the LHR in food isolates of E. coli, and its influence on heat resistance in S. enterica and Enterobacter spp. Cell counts of LHR-positive strains of E. coli, S. enterica and E. cloacae were reduced by less than 1, 1, and 4 log (cfu/mL), respectively, after exposure to 60 °C for 5 min, while cell counts of LHR-negative strains of the same species were reduced by more than 7 log (cfu/mL). Introducing an exogenous copy of the LHR into heat-sensitive enteropathogenic E. coli and S. enterica increased heat resistance to a level that was comparable to LHR-positive wild type strains. Cell counts of LHR-positive S. enterica were reduced by less than 1 log(cfu/mL) after heating to 60 °C for 5 min. Survival of LHR-positive strains was improved by increasing the NaCl concentration from 0 to 4%. Cell counts of LHR-positive strains of E. coli and S. enterica were reduced by less than 2 log (cfu/g) in ground beef patties cooked to an internal core temperature of 71 °C. This study indicates that LHR-positive Enterobacteriaceae pose a risk to food safety.

Small-aperture corneal inlay repositioning.

We describe a technique used to recenter a small-aperture corneal inlay (Kamra). Repositioning the inlay is performed to achieve the best presbyopic correction while maintaining distance visual acuity.

Mechanisms of Optical Regression Following Corneal Laser Refractive Surgery: Epithelial and Stromal Responses.

Laser vision correction is a safe and effective method of reducing spectacle dependence. Photorefractive Keratectomy (PRK), Laser In Situ Keratomileusis (LASIK), and Small-Incision Lenticule Extraction (SMILE) can accurately correct myopia, hyperopia, and astigmatism. Although these procedures are nearing optimization in terms of their ability to produce a desired refractive target, the long term cellular responses of the cornea to these procedures can cause patients to regress from the their ideal postoperative refraction. In many cases, refractive regression requires follow up enhancement surgeries, presenting additional risks to patients. Although some risk factors underlying refractive regression have been identified, the exact mechanisms have not been elucidated. It is clear that cellular proliferation events are important mediators of optical regression. This review focused specifically on cellular changes to the corneal epithelium and stroma, which may influence postoperative visual regression following LASIK, PRK, and SMILE procedures.

Long-term changes in keratometry and refraction after small aperture corneal inlay implantation.

PURPOSE: To assess longitudinal refractive, keratometric, and topographic changes following KAMRA small-aperture inlay implantation. DESIGN AND SETTING: Prospective study at a single site refractive surgery center. METHODS: Fifty patients underwent KAMRA small-aperture corneal inlay implantation for the correction of presbyopia. Uncorrected near visual acuity (UNVA), uncorrected distance visual acuity, manifest refractive spherical equivalent (MRSE), mean keratometry (Km), corneal topography, and surgically induced astigmatism vector analysis assessments were performed preoperatively and at 1, 3, 6, 12, 24, and 36 months postoperatively. RESULTS: The study comprises 50 eyes. An average shift of 0.15±0.63 D (range -1.63 to 2.00 D) occurred between preoperative baseline and 36 months. At 36 months, 54% of patients had hyperopic MRSE and 40% had myopic MRSE compared with baseline. Km was significantly elevated at all postoperative measurements compared with baseline, with the largest Km measured at 12 months. Eighty-six percent of patients had UNVA of 20/32 or better and 88% uncorrected distance visual acuity of 20/25 or better at 36 months. Longitudinal corneal topography revealed a pattern of corneal steepening over the body of the inlay and flattening over the aperture, correlating with a hyperopic shift. There was no significant surgically induced astigmatism. CONCLUSION: KAMRA inlay may cause an increase in Km compared with baseline. Corneal steepening may occur in a specific pattern with steepening over the inlay and flattening over the aperture. This topographic pattern causes a hyperopic shift, which may be relevant for subsequent procedures, such as cataract extraction.