EyeWorld India March 2018 Issue

Dr. Gupta said the most com- mon tests to screen for dry eye in her practice are osmolarity testing, MMP-9 (an inflammatory marker) testing, and meibomian gland imaging. “These tests give me a great understanding of how the ocular surface is functioning at the time of my evaluation,” Dr. Gupta said. “Hyperosmolarity is a core mecha- nism in dry eye disease and with prolonged hyperosmolarity inflam- mation is triggered; this is where the MMP-9 test is helpful as it iden- tifies critical levels of inflammation on the ocular surface. Last but not least, MGD is a big part of DED. Often clinical exam is insufficient to allow us to see how advanced MGD is. On many occasions, I have examined a patient clinically and found mild to moderate MGD, only to find severe gland atrophy on MG imaging. Understanding the degree of gland atrophy helps to understand disease severity and allows the physician to set realistic expectations with the patient.” Dr. Gupta will perform tear os- molarity testing and meibography on all patients. If either of those tests are positive for disease she will advance to MMP-9, Sjögren’s disease, and/or allergy testing. Most patients, after their dry eye is managed, can go on to have successful refractive surgery, Dr. Loh said. While there has been increased awareness efforts on the importance of treating the ocular surface prior to refractive surgery, including for refractive cataract sur- gery, Dr. Loh said taking the time to really treat these patients can be a hurdle. EWAP References 1. Zhao J, et al. Effect of higher-order aberra- tions and intraocular scatter on contrast sen- sitivity measured with a single instrument . Biomed Opt Express. 2017;8:2138–2147. 2. Sarkar S, et al. Image quality analysis of eyes undergoing LASER refractive surgery. PLoS One . 2016;11:e0148085. 3. Ambrósio R Jr, et al. Integration of Scheimpflug-based corneal tomography and biomechanical assessments for enhanc- ing ectasia detection. J Refract Surg. 2017;33(7):434–43. 4. Haddad J, Barnwell E, Rocha KM, Waring G IV, Ambrósio R Jr. First clinical im pres- sions on the integrated corneal tomography and corneal deformation parameters with a dynamic ultra-high-speed Scheimpflug camera. IJKECD. At press. 5. Silverman RH, et al. Epithelial remodeling as basis for machine-based identification of keratoconus. Invest Ophthalmol Vis Sci. 2014;55:1580–7. 6. Reinstein DZ, et al. Comparison of corneal epithelial thickness measurement between Fourier-domain OCT and very high- frequency digital ultrasound . J Refract Surg. 2015;31:438–45. 7. Urs R, et al. Comparison of very-high- frequency ultrasound and spectral-domain optical coherence tomography corneal and epithelial thickness maps. J Cataract Refract Surg. 2016;42:95–101. Editors’ note: Dr. Gupta has finan- cial interests with Johnson & John- son Vision (Santa Ana, California), TearLab (San Diego), and TearScience (Morrisville, North Carolina). Dr. Loh has financial interests with Allergan (Dublin, Ireland) and Shire (Lexington, Massachusetts). Dr. Reinstein and Dr. Rocha have no financial interests related to their comments. Contact information Gupta: preeyakgupta@gmail.com Loh: jenniferlohmd@gmail.com Reinstein: dzr@londonvisionclinic.com Rocha: karolinnemaia@gmail.com Views from Asia-Paci c Sheetal BRAR, MD Senior Consultant, Phaco & Refractive Department Nethradhama Super Specialty Eye Hospital No. 256/14 Kanakapura Main Road, 7th Block, Jayanagar, Bengaluru, Karnataka 560082, India Tel. no. +9591002092 brar_sheetal@yahoo.co.in T he article “Is it the age of allogenics?” is an interesting read, as it highlighted the resurgence of the concept of “tissue addition” in corneal and refractive surgery. The innovative procedures discussed such as presbyopic allogenic refractive lenticule (PEARL) and corneal allogenic intracorneal ring segments (CAIRS) for presbyopia and keratoconus are particularly fascinating, as both the fields offer a huge potential for surgical advancement. Our personal experience with the femtosecond intrastromal lenticule implantation (FILI) technique for hyperopia and keratoconus showed good safety and efficacy of use of allogenic SMILE lenticules. 1,2 However, there may be some concerns related to these procedures. First and foremost, any such procedure would amount to a sort of “mini corneal transplant”, and therefore carries a potential of allogenic rejection. Using a SMILE lenticule in this regard may be relatively safer, due to its predominant composition of stromal collagen tissue. Nevertheless, the presence of keratocytes in this tissue may potentially excite a rejection episode. In our series of 32 eyes treated with FILI for moderate to high hyperopia, 4 eyes of 2 patients showed diffuse haze of the implanted lenticule with drop in CDVA at 6 months postop, requiring their explantation. Hence, it would be desirable to use cultured collagen tissue devoid of keratocytes to eliminate the risk of future graft rejection for this purpose. Research in this direction is already underway. For presbyopia management in particular, there may be specific concerns of availability of precisely sized lenticules of proper thickness, intraoperative handling, and centration. Since a minimum of 30 microns tissue trephined to 1 mm would be required to obtain the desired depth of focus, the technique appears to be technically challenging. The implanted lenticule disc will have an abrupt, vertical, and relatively thick edge at its periphery with a potential space around it, which may over time show fibrous proliferation. This may potentially cause edge glare and other optical phenomena. Moreover, the hyperprolate shape of the cornea achieved postop may lead to induction of higher- order aberrations potentially degrading the quality of vision in the nondominant eye. Also, the nomograms may need futher refinement to achieve satisfactory near vision in presbyopic patients who are generally very demanding. In conclusion, allogenic corneal tissue transplantation for treatment of various conditions appears to be feasible and beneficial to potential candidates. However, since it is an evolving field, more data and further refinements are required to establish their long-term safety and efficacy. References 1. Ganesh S, et al. Cryopreservation of Extracted Corneal Lenticules after Small Incision Lenticule Extraction for Potential Use in Human Subjects. Cornea. 2014;33(12):1355-1362. 2. Ganesh S and Brar S. Femtosecond Intrastromal Lenticular Implantation Combined with Accelerated Collagen Cross-Linking for the Treatment of Keratoconus—Initial Clinical Result in 6 Eyes . Cornea. 2015 Oct;34(10):1331-9. Editors’ note: Dr. Brar declared no relevant nancial interests. Advances - from page 43 44 EWAP REFRACTIVE March 2018