Elmer Tu

Acanthamoeba keratitis: The Persistence of Cases Following a Multistate Outbreak

Purpose: To describe the trend of Acanthamoeba keratitis case reports following an outbreak and the recall of a multipurpose contact lens disinfection solution. Acanthamoeba keratitis is a serious eye infection caused by the free-living amoeba Acanthamoeba that primarily affects contact lens users. Methods: A convenience sample of 13 ophthalmology centers and laboratories in the USA, provided annual numbers of Acanthamoeba keratitis cases diagnosed between 1999–2009 and monthly numbers of cases diagnosed between 2007–2009. Data on ophthalmic preparations of anti-Acanthamoeba therapies were collected from a national compounding pharmacy. Results: Data from sentinel site ophthalmology centers and laboratories revealed that the yearly number of cases gradually increased from 22 in 1999 to 43 in 2003, with a marked increase beginning in 2004 (93 cases) that continued through 2007 (170 cases; p < 0.0001). The outbreak identified from these sentinel sites resulted in the recall of a contact lens disinfecting solution. There was a statistically significant (p ≤ 0.0001) decrease in monthly cases reported from 28 cases in June 2007 (following the recall) to seven cases in June 2008, followed by an increase (p = 0.0004) in reported cases thereafter; cases have remained higher than pre-outbreak levels. A similar trend was seen in prescriptions for Acanthamoeba keratitis chemotherapy. Cases were significantly more likely to be reported during summer than during other seasons. Conclusion: The persistently elevated number of reported cases supports the need to understand the risk factors and environmental exposures associated with Acanthamoeba keratitis. Further prevention efforts are needed to reduce the number of cases occurring among contact lens wearers.

A multicenter study to map genes for Fuchs endothelial corneal dystrophy: Baseline characteristics and heritability

Purpose: To describe the methods for family and case–control recruitment for a multicenter genetic and associated heritability analyses of Fuchs endothelial corneal dystrophy (FECD). Methods: Twenty-nine enrolling sites with 62 trained investigators and coordinators gathered individual and family information, graded the phenotype, and collected blood and/or saliva for genetic analysis on all individuals with and without FECD. The degree of FECD was assessed in a 0 to 6 semiquantitative scale using standardized clinical methods with pathological verification of FECD on at least 1 member of each family. Central corneal thickness was measured by ultrasonic pachymetry. Results: Three hundred twenty-two families with 330 affected sibling pairs with FECD were enrolled and included a total of 650 sibling pairs of all disease grades. Using the entire 7-step FECD grading scale or a dichotomous definition of severe disease, heritability was assessed in families via sib–sib correlations. Both binary indicators of severe disease and semiquantitative measures of disease severity were significantly heritable, with heritability estimates of 30% for severe disease, 37% to 39% for FECD score, and 47% for central corneal thickness. Conclusions: Genetic risk factors have a strong role in the severity of the FECD phenotype and corneal thickness. Genotyping this cohort with high-density genetic markers followed by appropriate statistical analyses should lead to novel loci for disease susceptibility.

Outcome of descemet stripping automated endothelial keratoplasty in patients with an anterior chamber intraocular lens.

Purpose: To evaluate the outcome of Descemet stripping automated endothelial keratoplasty (DSAEK) in patients with a retained anterior chamber intraocular lens (ACIOL). Methods: A retrospective review of 11 patients with corneal decompensation and ACIOL who underwent DSAEK was performed. All patients except 1 had open-loop style ACIOLs, and in all cases, there was adequate anterior chamber depth. At the time of surgery, 6 patients had a temporary suture to secure their graft, 2 of which were retained from the insertion method, and the other 4 were placed additionally. Postoperatively, the rate of donor detachment, graft clarity, corneal pachymetry, and visual acuity were noted. Results: There was only 1 graft dislocation postoperatively, which was reattached successfully by air injection. There was 1 primary graft failure (without dislocation) among the 11 patients during the mean follow-up of 12 months (range: 6-25 months); at last follow-up, the visual acuity had improved in all the other 10 patients. Conclusions: This series demonstrates that DSAEK can be performed successfully in patients with existing ACIOLs. These early outcomes suggest that DSAEK alone may be considered as an alternative to a lens exchange with DSAEK in patients with adequate anterior chamber depth.

Sequential corneal infection with two genotypically distinct Acanthamoebae associated with renewed contact lens wear

Sequential corneal infection with two genotypically distinct Acanthamoebae associated with renewed contact lens wear

Defects of the Cornea

Defects of the cornea play an important role in clinical genetics, because abnormalities are often easily detected on clinical ophthalmic examination. This allows for efficient screening, phenotypic categorization, and correlation with molecular genetic findings. Corneal dystrophies tend to be autosomal dominant, bilateral, not usually associated with other ocular or systemic abnormalities, are often limited to a single corneal layer, commonly involve the central cornea, and progress with time. Many dystrophies display genetic heterogeneity and/or phenotypic variability. Recent discoveries of genetic defects have enhanced our understanding of several dystrophies and allowed for more accurate classification. Keratoconus displays a conical protrusion of the cornea associated with central stromal thinning and irregularity of the corneal surface. Its pathogenesis is unknown and no candidate gene has been identified. Newer treatment options have shown promise. Metabolic disorders are generally associated with accumulation of an abnormal substance in the cornea. If the substance is produced by the cornea, it can appear throughout it. If it is elevated in the blood, it tends to accumulate in the corneal periphery. Inherited corneal defects can occur as isolated findings and in association with systemic disease. Awareness of corneal disorders is important to general physicians, geneticists and ophthalmologists.