Eyeworld

16 | EYEWORLD | AUGUST 2019 ASCRS NEWS might help us to understand the effect of eye rubbing in keratoconus progression. After a standardized session of eye rub- bing, keratoconus eyes were found to have a significant, but transient, increase in posterior corneal astigmatism and decrease in anterior chamber volume, which was not present in healthy eyes after eye rubbing. In addition, keratoconus eyes had a significant decrease in IOPG after standardized eye rubbing, which persisted at least 7 minutes after eye rubbing had been completed. These findings are inter- esting because they provide further physiologic evidence that keratoconus corneas might be weaker than healthy corneas. In addition, it may provide further insight into the pathogenesis of this disease. One major strength of this study is the inclusion of a control group that was similar in age and sex distribution. A lack of change in the posterior corneal astigmatism and AC volume in healthy eyes lends further credence to the changes observed in those with kera- toconus. However, inclusion of information on baseline characteristics would have been extremely helpful to further put these findings into context. It would have been interesting to positive correlation (i.e., if any met- rics could predict changes due to eye rubbing). The only positive correla- tion was between pre-eye rubbing maximum keratom- etry and change in posterior astig- matism (r=0.37, p=0.043). Discussion Eye rubbing is thought to be a significant factor in the development of keratoconus and has also been shown to increase the progression of ker- atoconus once it develops. 5 However, no study to date has investigated the effect of eye rub- bing on mechanical parameters of the cornea in eyes with a prior diagnosis of keratoconus. The present study is the first to evaluate the effect of eye rubbing on biomechanical parameters of the anterior segment in patients with kerato- conus. Further understanding of these factors Comparison of effect of eye rubbing in keratoconus and healthy eyes using Scheimpflug analysis and a dynamic bidirectional applanation device María Henriquez, MD, PhD, Michelle Cerrate, MD, Martha Hadid, MD, Laura Cañola-Ramirez, MD, Farhad Hafezi, MD, PhD, Luis Izquierdo Jr., MD, PhD J Cataract Refract Surg. 2019;45(8):1156–1162. n Results: In the healthy group, the immediate mean change in steeper anterior keratometry, posterior astigmatism, anterior chamber volume, flattest posterior keratometry, and Goldman correlated intraocular pressure (IOPG) after eye rubbing was 0.07±0.15 diopters (D), –0.01±0.08 D, 0.03±7.06 mm 3 , –0.001±0.04 mm, and –1.21±1.99 mm Hg, whereas the mean change in the KC group was –0.03±0.32 D, 0.14±0.50 D, –5.09±8.45 mm 3 , 0.03±0.06 mm, and –1.61±1.41 mm Hg, respectively. There were statistically significant differences between pre- and post-eye rubbing values of posterior astigmatism, anterior chamber volume, and IOPG in the KC group (p=0.03, p=0.0003, and p=0.001, respectively) and not in the healthy group (p=0.65, p=0.85, and p=0.23, respectively). n Conclusions: Unlike the healthy eyes group, the keratoconus group experienced significant changes in anterior chamber volume, IOP, and corneal posterior astigmatism after eye rubbing. n Purpose: To compare the effect of eye rubbing on Scheimpflug imaging parameters and corneal biomechanics in keratoconus (KC) and healthy eyes. n Setting: Oftalmosalud Instituto de Ojos, Lima, Peru. n Design: Prospective cohort study. n Methods: The study included 30 healthy eyes and 31 KC eyes that attended the Institution between January 2017 and July 2017. Eye rubbing was performed for 1 minute followed by a 5-second break, followed by further rubbing for 1 minute. Baseline tests were performed before rubbing; post-rubbing tests were performed immediately after (0 minutes), and then again at 7 and 14 minutes. Parameters related to anterior and posterior curvature and elevation, pachymetry, and corneal biomechanics obtained from tomography with a rotating Scheimpflug camera (Oculus Instruments) and the Ocular Response Analyzer were measured and compared between healthy and KC eyes. References 1. Gordon-Shaag A, et al. The genetic and environmental factors for keratoconus. BioMed Res Int. 2015;2015:795738. 2. Sugar J, Macsai MS. What causes keratoconus? Cornea. 2012;31:716–9. 3. Davidson AE, et al. The pathogenesis of keratoconus. Eye. 2014;28:189–95. 4. McMonnies CW. Mechanisms of rubbing-related corneal trauma in keratoconus. Cornea. 2009;28:607–15. 5. McMonnies CW. Abnormal rubbing and keratectasia. Eye Contact Lens. 2007;33:265–71. continued from page 15 Wilmer Eye Institute residents, from left: Pujan Dave, MD, Meleha Ahmad, MD, Ishrat Ahmed, MD, and Inas Aboobakar, MD Source: Wilmer Eye Institute

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