Eyeworld

AUGUST 2019 | EYEWORLD | 15 EYEWORLD JOURNAL CLUB Contact information Boland: boland@jhu.edu disease on clinical exam as well as on corne- al topography and a history of eye rubbing. Subjects with Vogt striae, a non-clear cornea, contact lens use within 3 months, and topical medication use were excluded. Eye rubbing was performed by a research- er masked to the underlying study group. The researcher used the right index finger to apply 5–6 Newtons (about 1.25 pounds) of force while moving their finger in a clockwise, circular motion over a closed eyelid with the subject in primary gaze. This was performed twice, 1 minute at a time, with a 5-second break in between. Tomography and corneal biomechan- ics were measured using a Scheimpflug camera and the ORA. These tests were performed less than 1 minute apart before, immediately after, 7 minutes after, and 14 minutes after standardized eye rubbing. Corneal imaging was used to measure a variety of parameters and found three that were statistically different in eyes with keratoconus but not in healthy eyes. Immediately after eye rubbing, there was an increase in posterior cor- neal astigmatism (p=0.007, +0.14 D), decrease in anterior chamber volume (p<0.001, –5.1 microL), and a decrease in Goldmann-correlat- ed IOP (p<0.001, –1.61 mm Hg). The decrease in IOP was the only change that persisted at 7 minutes (p=0.004, –1.33 mm Hg). Healthy eyes showed an increase in the anterior steepest keratometry (p=0.01, 0.07 D) immediately after eye rubbing, while keratoconus eyes did not. Five keratoconus eyes had Scheimpflug anal- ysis performed at a mean of 8.8 months after eye rubbing, at which time 2 eyes had signs of progression. Finally, the group also correlated pre-eye rubbing metrics to these variables that exhibited statistically significant changes to eye rubbing to determine whether there was any K eratoconus is the most common corneal ectasia and one of the leading indications for corneal transplan- tation in developed countries. 1 It is characterized by thinning of the central cornea, which leads to myopia, irregular astigmatism, and potentially significant visual impairment. 2 In addition to genetic predisposition, environmental factors are thought to contribute to disease develop- ment, with eye rubbing being the strongest known environmental risk factor. 3 The precise mechanism whereby eye rubbing contributes to keratoconus development remains unknown, though possible explanations include progres- sive epithelial thinning, increasing concentration of inflammatory mediators, increased corneal temperature, and changes to keratocytes in response to mechanical trauma. 4 In this article, the authors seek to further investigate the role of eye rubbing in keratoconus by assessing cor- neal biomechanical changes in keratoconus eyes compared to healthy eyes using the Ocular Re- sponse Analyzer (ORA, Reichert Technologies). They also assess changes in corneal tomography as measured by Scheimpflug imaging in re- sponse to eye rubbing in keratoconus patients and controls. Study summary Henriquez et al. undertook a comparative study to compare the effect of a specific eye rub- bing procedure on various corneal and ante- rior segment metrics in eyes with and without keratoconus. The study consisted of 30 healthy eyes (mean age 27.2 years) and 31 eyes with keratoconus (mean age 27.8 years), with one eye per subject randomly selected. The healthy eyes had best corrected visual acuity of at least 20/20 without significant refractive error (<1.5 D), and the eyes with keratoconus had signs of by Meleha Ahmad, MD, Pujan Dave, MD, Inas Aboobakar, MD, Ishrat Ahmed, MD, and Michael Boland, MD A review of "Comparison of effect of eye rubbing in keratoconus and healthy eyes using Scheimpflug analysis and a dynamic bidirectional applanation device" I invited the Wilmer residents to review this August JCRS study that seeks to compare and quantify corneal biomechan- ical changes caused by eye rubbing in patients with and without keratoconus. —David F. Chang, MD EyeWorld Journal Club Editor Michael Boland, MD Associate residency program director Wilmer Eye Institute Johns Hopkins University School of Medicine Baltimore continued on page 16

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