Corneal biomechanics in iatrogenic ectasia and keratoconus: a review of the literature

The Ocular Response Analyzer [ORA] [Reichert Ophthalmic Instruments, Buffalo, NY] allows direct measurement of corneal biomechanical properties. Since its introduction, many studies have sought to elucidate the clinical applications of corneal hysteresis [CH] and corneal resistance factor [CRF]. More recently, detailed corneal deformation signal waveform analysis [WA] has potentially expanded the diagnostic capabilities of the ORA. In this review, the role of CH, CRF, and WA are examined in keratoconus [KC] and iatrogenic ectasia [IE]. The PubMed database was searched electronically for peer-reviewed literature in July 2012 and August 2012 without date restrictions. The search strategy included medical subject heading [MeSH] and natural language terms to retrieve references on corneal biomechanics, CH, CRF, corneal deformation signal WA, IE, and KC. The evidence suggests that while CH and CRF are poor screening tools when used alone, increased sensitivity and specificity of KC and IE screening result when these parameters are combined with tomography and topography. Recent advances in WA are promising, but little is currently understood about its biomechanical and clinical relevance. Future studies should seek to refine the screening protocols for KC and IE as well as define the clinical applicability of WA parameters

Angle Kappa and its importance in refractive surgery

Angle kappa is the difference between the pupillary and visual axis. This measurement is of paramount consideration in refractive surgery, as proper centration is required for optimal results. Angle kappa may contribute to MFIOL decentration and its resultant photic phenomena. Adjusting placement of MFIOLs for angle kappa is not supported by the literature but is likely to help reduce glare and haloes. Centering LASIK in angle kappa patients over the corneal light reflex is safe, efficacious, and recommended. Centering in-between the corneal reflex and the entrance pupil is also safe and efficacious. The literature regarding PRK in patients with an angle kappa is sparse but centering on the corneal reflex is assumed to be similar to centering LASIK on the corneal reflex. Thus, centration of MFIOLs, LASIK, and PRK should be focused on the corneal reflex for patients with a large angle kappa. More research is needed to guide surgeons' approach to angle kappa

Diplopia as the primary presentation of foodborne botulism

Foodborne botulism is a serious condition caused by Clostridium botulinum neurotoxin. Clinically, botulism presents as bilateral cranial nerve neuropathy and descending paralysis. We report a unique presentation of botulism to remind clinicians of this potentially fatal condition. In this observational case report initial evaluation showed only esodeviation. This progressed to unilateral cranial nerve six [CN VI] paresis along with systemic signs. Clinical diagnosis was made based on in-depth history and concurrent symptoms in three other patients. Foodborne botulism presenting as diplopia and unilateral motility deficits is rare and can represent a diagnostic and therapeutic challenge to the ophthalmologist

Comparing the rate of regression after conductive keratoplasty with or without prior laser-assisted in situ keratomileusis or photorefractive keratectomy

To assess the regression rate of conductive keratoplasty [CK] in patients with or without previous laser-assisted in situ keratomileusis [LASIK] or photorefractive keratectomy [PRK]. University of Utah, Medical School, John A. Moran Eye Center, Salt Lake City, Utah. A retrospective, age-matched chart review identified records of 6 patients who underwent CK after refractive surgery and 12 patients who underwent CK without prior refractive surgery. The main outcome measures were postoperative uncorrected and corrected visual acuities and refraction changes over time. Preoperatively, the mean manifest refraction spherical equivalent [MRSE] of the 15 eyes [12 patients] that underwent CK without refractive surgery was 0.83 diopters [D] and the 7 eyes [6 patients] that underwent CK after refractive surgery had an average MRSE of 0.27 D. Postoperatively, the mean MRSE of the refractive surgery patients was -0.86 D at 6 months, regressing to -0.67 D at 12 months. The postoperative MRSE in the eyes without refractive surgery was -0.58 D. at 6 months, regressing to -0.38 D at 12 months. The rate of regression was linear in both groups, calculated at 0.033 D per month in all patients. Patients with previous LASIK or PRK showed a greater treatment response to CK but regressed at a similar rate as those eyes without prior LASIK or PRK. Overall CK is a safe procedure that inevitably regresses

Ocular surface squamous neoplasia masquerading as superior limbic keratoconjunctivitis

To report a case of ocular surface squamous neoplasia [OSSN] masquerading as superior limbic keratoconjunctivitis [SLK]. A 62-year-old woman was referred with foreign body sensation, irritation, photophobia and decreased vision in the left eye. She was initially treated for 10 months with intermittent topical corticosteroids for a presumed diagnosis of SLK. She underwent excisional biopsy of the superior conjunctiva and was found, on histopathologic evaluation, to have OSSN with moderate to marked dysplasia. This is the first reported case of OSSN masquerading with signs and symptoms of SLK. Any ocular surface lesion refractory to standard medical treatment should raise suspicion for a malignant process and warrant further cytologic or histopathologic evaluation

Femtosecond laser-assisted cataract surgery: a current review

To evaluate the safety, efficacy, advantages, and limitations of femtosecond laser-assisted cataract surgery through a review of the literature. A PubMed search was conducted using topic-appropriate keywords to screen and select articles. Initial research has shown appropriate safety and efficacy of femtosecond laser-assisted cataract surgery, with improvements in anterior capsulotomy, phacofragmentation, and corneal incision. Limitations of these studies include small sample size and short-term follow-up. Cost-benefit analysis has not yet been addressed. Preliminary data for femtosecond laser-assisted cataract surgery shows appropriate safety and efficacy, and possible advantage over conventional cataract surgery. Questions to eventually be answered include comparisons of long-term postoperative complication rates-including infection and visual outcomes-and analysis of contraindications and financial feasibility