Haidinger’s brushes elicited at varying degrees of polarization rapidly and easily assesses total macular pigmentation

Macular pigments (MPs), by absorbing potentially toxic short-wavelength (400–500 nm) visible light, provide protection against photo-chemical damage thought to be relevant in the pathogenesis of age-related macular degeneration (AMD). A method of screening for low levels of MPs could be part of a prevention strategy for helping people to delay the onset of AMD. We introduce a new method for assessing MP density that takes advantage of the polarization-dependent absorption of blue light by MPs, which results in the entoptic phenomenon called Haidinger’s brushes (HB). Subjects were asked to identify the direction of rotation of HB when presented with a circular stimulus illuminated with an even intensity of polarized white light in which the electric field vector was rotating either clockwise or anti-clockwise. By reducing the degree of polarization of the stimulus light, a threshold for perceiving HB (degree of polarization threshold) was determined and correlated (r2=0.66) to macular pigment optical density assessed using dual-wavelength fundus autofluoresence. The speed and ease of measurement of degree of polarization threshold makes it well suited for large-scale screening of macular pigmentation

The relationship between long-term contact lens wear and corneal thickness

The purpose of this study is to assess the effects of long-term contact lens wear on corneal thickness and to compare differences based on rigid versus soft lens material. This analysis included scanning slit topographic imaging (Orbscan, Bausch & Lomb, Rochester, NY) performed on 124 consecutive patients (248 eyes), who underwent comprehensive evaluations in consideration of refractive surgery by one surgeon. Sixty-two 62 patients (124 eyes) who had not previously worn contact lenses had a least-squares mean pachymetry of 546.4 microm +/-3.5 SE. Thirty-nine patients (78 eyes) who had previously worn soft contact lenses for an average of 16 years had a least-squares mean pachymetry of 543.2 microm +/-3.8 SE. Twenty-three patients (46 eyes) who had worn rigid contact lenses for an average of 19 years had a least-squares mean pachymetry of 509.4 microm +/-6.9 SE. Mean pachymetry differed significantly between eyes wearing rigid lenses versus no lenses (P<0.0001) and between eyes wearing rigid lenses versus soft lenses (P=0.0002). Long-term rigid contact lens wear is associated with a decrease in the average central-corneal thickness (CCT) by an average of 37 microm, in this group of otherwise healthy eyes, compared to no contact lens wear. Long-term soft contact lens wear did not appear to significantly change corneal thickness compared to no contact lens wear. Caution should be exercised when screening patients with a history of long-term rigid contact lens wear for possible excimer-laser photoablative correction

High interocular corneal symmetry in average simulated keratometry, central corneal thickness, and posterior elevation

The purpose of this study was to assess interocular corneal symmetry in average simulated keratometry, corneal thickness, and posterior corneal elevation. This retrospective analysis included data from scanning slit topography (Orbscan II; Bausch and Lomb, Rochester, NY) on 242 eyes from 121 consecutive patients undergoing standard evaluation for consideration of elective laser vision correction. The symmetry between the right and left eye in average simulated keratometry, minimum central corneal thickness, and posterior corneal elevation was assessed by comparative data analysis. Simulated keratometry ranged from 39.9 to 48.6 D. The interocular difference in average simulated keratometry was 0.47 D (standard deviation [SD] 0.43). The interocular Pearson correlation coefficient for average simulated keratometry was 0.90 (p < 0.001). The range of minimum corneal thickness was 432 to 628 microm. The interocular Pearson correlation coefficient for minimum central corneal thickness was 0.95 (p < 0.001). Right and left eye minimum corneal thickness differed by an average 8 microm (SD 7). The range of posterior elevation was -4 to 54 microm. The average difference in posterior corneal elevation between the right and left eye was 6 microm (SD 5). The interocular Pearson correlation coefficient for posterior corneal elevation was 0.72 (p < 0.001). The average posterior elevation was 19 microm (SD 11). Although a wide range of values exists in simulated keratometry, minimum corneal thickness, and posterior corneal elevation, interocular symmetry in all these parameters was very high in this group of consecutive patients. Asymmetry of these interocular parameters may warrant repeat clinical testing for accuracy and may predict corneal abnormalities. Normative data on posterior cornea elevation is presented. This study points out potentially clinically important high interocular corneal symmetry data in simulated keratometry, corneal thickness, and posterior corneal elevation

Outcome of second surgery in LASIK cases aborted due to flap complications

Purpose: To describe the technique and timing of second refractive surgery after aborted laser in situ keratomileusis (LASIK) due to intraoperative flap complication and determine the final visual outcome. Setting: Outpatient ambulatory laser vision correction centers. Methods: This retrospective noncomparative case series included 16 patients (16 eyes) who had a second refractive surgery after initial LASIK surgery was aborted because of a flap complication. Charts were reviewed with attention to initial preoperative data, intraoperative details of the aborted LASIK, postoperative examination, possible causes of the flap complication, timing and technique of second refractive surgery, and final visual outcome. Results: Causes of the aborted LASIK were identified in 13 of 16 eyes (81.2%) and included eye squeezing (5 eyes), loss of suction or machine failure (5 eyes), steep corneas (2 eyes), and learning curve of the surgeon (1 eye). The mean time until the second surgery was 135 days (range 49 to 372 days). Repeat flaps were created deeper and larger than the initially attempted flaps when possible. No patient had a final uncorrected visual acuity (UCVA) worse than 20/30 after the second surgery. Two eyes (12.5%) lost 1 line of best spectacle-corrected visual acuity. Conclusion: A planned delayed reoperation after sufficient corneal healing following an intraoperative flap complication can result in satisfactory recovery of UCVA

Short-Term Visual Outcomes of Boston Type 1 Keratoprosthesis Implantation

Purpose: To report the short-term visual outcomes after keratoprosthesis implantation