Volume 5, Number 48
Monday, December 5, 2005



In this issue: (click heading to view article)
Corneal Higher-Order Aberrations in Myopic vs. Hyperopic LASIK
Proteins Secreted in Tears and LPS Response of Corneal Epithelial Cells
Ocular Complications After Organ and Bone Marrow Transplantation in Children
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Corneal Higher-Order Aberrations in Myopic vs. Hyperopic LASIK

A retrospective, comparative case series study by Germany’s Johann Wolfgang Goethe University compared the change in anterior corneal higher-order (third- to fifth-order) aberrations (HOAs) induced by myopic and hyperopic LASIK.

The study included 100 eyes (50 myopes and 50 hyperopes) of 59 patients. The mean preoperative spherical equivalent (SE) was -4.22 +/- 1.78D (range, -1.25 to -8.00D) in the myopic group (Group A) and +2.72 +/- 1.25D (range, +0.25 to +5.00D) in the hyperopic group (Group B).

Surgeons performed LASIK using a conventional spherocylindrical laser algorithm (Planoscan V2.9992, Bausch & Lomb/Technolas). Optical zone diameter was 6.70 +/- 0.32 mm (range, 6 mm to 7 mm) in Group A and 6.59 +/- 0.19 mm (range, 6.5 mm to 7 mm) in Group B. Third- to fifth-order corneal HOA were computed for a pupil diameter of 6 mm from corneal topographic examinations, before and one month after surgery.

The total HOA root mean square (RMS) changed in Group A by 0.167 +/- 0.180 microns and in Group B by 0.341 +/- 0.341 microns. The mean induction of coma RMS was significantly different in both groups (myopes, 0.092 +/- 0.195 microns; hyperopes, 0.252 +/- 0.305 microns). For spherical aberration (Z 4,0), Group A showed a significant increase (0.130 +/- 0.120 microns), whereas Group B showed a significant decrease (-0.317 +/- 0.158 microns). Fifth-order aberrations showed an increase in both groups, which was higher in Group B (0.069 +/- 0.120 microns) than in Group A (0.005 +/- 0.065 microns).

The authors concluded that myopic and hyperopic LASIK had different patterns of HOA induction: while myopic LASIK induced positive spherical aberrations and positive secondary astigmatism, hyperopic LASIK induced negative spherical aberrations and negative secondary astigmatism. Hyperopic LASIK also induced more third- and fifth-order comalike aberrations than myopic LASIK.

SOURCE: Kohnen T, Mahmoud K, Buhren J. Comparison of corneal higher-order aberrations induced by myopic and hyperopic LASIK. Ophthalmol. 2005;112(10):1692.
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Proteins Secreted in Tears and LPS Response of Corneal Epithelial Cells

Lipopolysaccharide (LPS) is one of the most powerful bacterial virulence factors in terms of proinflammatory properties, and it is believed to contribute to corneal bacterial keratitis. This study by the University of Ottawa, Ontario, Canada, aimed to develop a better understanding of the spacial expression of the LPS receptor components at the tear-corneal interface, which the researchers believed might facilitate enhanced functions of the LPS receptor complex in ocular defense against Gram-negative infections.

Investigators used ELISA, RT-PCR, Western blot analysis and immunofluorescence to examine the expression of LPS-binding protein (LBP), CD14, toll-like receptor (TLR)-4 and MD-2 in human lacrimal glands, reflex tears and corneal epithelia. They used ELISA to measure the release of proinflammatory cytokines after the activation of primary and immortalized corneal epithelial cells with LPS and human tears.

LBP and CD14 proteins were detected in reflex human tears. Human lacrimal glands and corneal epithelia expressed LBP, CD14, TLR4 and MD-2 mRNAs and proteins. In the corneal epithelium, LBP was mainly expressed by superficial and basal epithelial cells, whereas CD14, TLR4 and MD-2 expression were limited to the wing and basal epithelial cells. In a dose-dependent manner, tear CD14 and LBP mediated the secretion of interleukin (IL)-6 and IL-8 by corneal epithelia cells when challenged with LPS.

Tear CD14 and LBP complemented the LPS receptor complex expressed by the corneal epithelia to trigger an immune response in the presence of LPS. The authors maintain that the complementation of these tear and corneal immune proteins could play an important role in LPS recognition and signaling and could therefore modulate ocular innate immunity.

SOURCE: Blais DR, Vascotto SG, Griffith M, Altosaar I. LBP and CD14 secreted in tears by the lacrimal glands modulate the LPS response of corneal epithelial cells. Invest Ophthalmol Vis Sci. 2005;46(11):4235-44.
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Ocular Complications After Organ and Bone Marrow Transplantation in Children

Organ and bone marrow transplantation are commonly performed in children. Ocular complications usually are described as secondary to post-transplantation medications, but the complication rate is unknown. Researchers at the University of Wisconsin conducted a retrospective chart review of 93 children younger than 18 years who had transplantation surgery between 1989 and 2004. They analyzed the rate and type of ocular complications, including those requiring ocular surgery. They also studied medications and visual loss associated with adverse effects.

Of the 93 patients, 74 patients met the entry criteria. Sixty-one patients had at least one year of follow-up; the longest follow-up duration was 14 years. The one-year post-transplantation complication rate was 16.0 percent (95 percent confidence interval 6.8 percent to 24.4 percent). Adverse effects included cytomegalovirus (CMV) retinitis, cataract, graft-versus-host disease, lymphoproliferative disorder, persistent strabismus and transient visual loss. Four patients underwent eye surgery, including lensectomy for cataract, tarsorrhaphy for corneal ulcer, and iris biopsy. They had surgery 0.9 to 4.7 years after transplantation. Most patients were taking prednisone and cyclosporine when their complication was diagnosed. One patient"s visual acuity deteriorated to no light perception in one eye and 20/250 in the other eye secondary to CMV retinitis. Most patients had a final visual acuity of 20/40 or greater.

The authors concluded that the one-year complication rate for ocular impairment with transplantation surgery in children was 16.0 percent, showing that eye surgery may be required within the first few years after transplantation.

SOURCE: Bradfield YS, Kushner BJ, Gangnon RE. Ocular complications after organ and bone marrow transplantation in children. J AAPOS 2005;9(5):426-32.
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BRIEFLY
  • TWELVE-MONTH FOLLOW-UP VISITS COMPLETED IN OCCULOGIX TRIAL FOR DRY AMD. OccuLogix Inc. recently announced that it has completed all final study visits for its Phase III Multicenter Investigation of Rheopheresis for AMD (MIRA-1) trial. A total of 169 subjects completed their 12-month follow-up exams after having been enrolled for participation In December 2004. MIRA-1 is a multicenter, randomized, double-masked and placebo-controlled trial designed to evaluate the safety and efficacy of RHEO Therapy in patients with Category 3 and Category 4 dry AMD. If successful, the treatment is expected to support OccuLogix"s application to the FDA for approval to market its RHEO System in the United States. Occulogix expects to have trial results by the second quarter of 2006.
  • PFIZER SELECTS DEVELOPMENT CANDIDATE FOR COLLABORATION ON EYE TREATMENT COMPOUND. Pfizer Inc. has selected a development candidate in its collaboration with NicOx, a French organization focused on novel nitric oxide-donating ophthalmic compounds. Pfizer exercised its option to acquire an exclusive worldwide license to the proprietary NicOx compounds covered by the agreement; NicOx will receive payment of 2 million euro from Pfizer. Pfizer and NicOx were jointly responsible for the research project, in which a number of nitric oxide-donating compounds were synthesized and submitted for an extensive series of preclinical tests. Several compounds successfully fulfilled a number of key criteria and demonstrated superior activity, compared to reference compounds, in established in vivo eye disease models. Pfizer has selected a candidate for development and will fund and be responsible for all future work on the compound. The research, option, development and licensing agreement between Pfizer and NicOx was signed in August 2004.
  • STUDY OF LENS ELASTICITY MAY AID IN DEVELOPMENT OF NEW PROSTHETIC LENS. Researchers at the University of Missouri, Rolla, are working with eyecare practitioners at the Veterans Affairs Medical Center at Barnes Jewish Hospital, St. Louis, to study the elasticity of the human lens. The investigators hope to develop a new prosthetic hydrogel that simulates the optical and mechanical properties of a natural lens. Currently, artificial lenses used in cataract surgery are relatively inflexible and limit a post-surgical patient’s range of focus. Using lenses from pigs and human cadavers, the researchers hope to characterize the force needed to stretch lenses and allow for the maximum range of focus--the same technique used to characterize prosthetic lenses. Based on this data, they hope to develop a new hydrogel lens that can simulate the natural lens. They believe that the study of the mechanical behavior of human lenses may also aid in treating other eye problems, including presbyopia.


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