CORNEA EWAP DECEMBER 2022 29 John Chang, MD Hong Kong Sanatorium & Hospital 8/F, Phase II, Li Shu Pui Block, Hong Kong john.sm.chang@hksh.com ASIA-PACIFIC PERSPECTIVES For all my cataract patients’ monofocal and multifocal intraocular lenses (MFIOLs), I measure with both IOLMaster 700 and Pentacam AXL, which measure the anterior and posterior cornea. Pentacam detects irregular and post-refractive surgery cornea, and also tells me if the cornea is thick enough in case LASIK fine-tuning is necessary. If there are corneal abnormalities (e.g., asymmetric astigmatism) detected, I would use Topolyzer Vario (Alcon) which gives me a more detailed and sensitive assessment of the anterior cornea using Placido topography. If the cornea is irregular or asymmetric, I will not implant an MFIOL and sometimes not even a toric monofocal lens. Dr. Miller’s comment of “garbage in, garbage out” is very important. To ensure good data reliability, a remeasurement will be necessary if there is significant deviation in axial length and keratometric readings between the biometric devices. I also make sure the standard deviation of all the parameters of the IOLMaster 700 is within acceptable range. Proper head positioning is also very important for astigmatism measurement. In 2014, Fesharaki et al.1 reported that the mean astigmatic axis error was 3.2°±1.5° and 18.4°±4.2° with lateral head tilt angles of 5° and 25° respectively. In Asia, myopia is more prevalent, because we spend more time on computers and cellphones, which also cause more dry eyes. To detect dry eyes preoperatively, I stain the cornea with fluorescein to assess the tear film quality and stability (tear film breakup time). Preoperative care for dry eye is important as tear instability will worsen the quality of preoperative corneal imaging. For significant dry eyes, I prescribe them initially with thick tear supplements (0.5% hyaluronic acid) (daytime) and ointment (night), and subsequently thinner artificial tears (daytime) and gel (night) 2–3 days before measurement. We perform corneal imaging at least 5 minutes after applying thin artificial tears, because immediate application can induce up to 1 D of astigmatism (Röggla et al., 20212). To improve refractive predictability, we calculate the toric IOL power using the Barrett Toric Calculator with mean keratometric value of measurements (integrated mean K) obtained from manual keratometry, IOLMaster 700, and Pentacam AXL. For post-LASIK patients, I pay extra attention to the preoperative topography to rule out any corneal abnormalities such as central island and decentered ablation. I also look at the higher-order aberration value and avoid MFIOL if they are too high. References 1. Fesharaki H, et al. The effects of lateral head tilt on ocular astigmatic axis. Advanced Biomedical Research. 2014;3(1):10. 2. Röggla V, et al. Influence of artificial tears on keratometric measurements in cataract patients. American Journal of Ophthalmology. 2021;221:1–8. Editors’ note: Dr. Chang receives lecture honoraria and research grants from Alcon and Carl Zeiss, and a lecture honorarium from Global Vision HK Ltd. Evaporative - from page 25 for specific patients. She noted that insurance coverage can be a hurdle. Both Dr. Bunya and Dr. Gupta discussed Tyrvaya (varenicline, Oyster Point), a nasal spray that stimulates the trigeminal nerve pathway for tear production. Dr. Gupta described how Tyrvaya not only stimulates the lacrimal gland but also causes contraction of the meibomian gland muscle and degranulation of the goblet cells, which produce mucin. “It’s stimulating the complete tear. We like to think of this product as something that’s trying to restore tear film homeostasis. When that happens, you’re basically independent of the etiology, whether it’s evaporative or aqueous deficient,” she said. Dr. Bunya and Dr. Gupta also mentioned punctal occlusion or cautery. Dr. Gupta noted that plugs in the right person can be helpful, but they won’t aid patients with evaporative dry eye or allergies. Other available treatments for aqueous tear deficient dry eye, Dr. Bunya said, include short courses of topical steroid drops; blood products, such as autologous serum eye drops; and scleral lenses. ‘There is no cure’ In the end, all the physicians interviewed for this article said the treatments for dry eye will need to be lifelong to maintain symptom relief. “There is no cure, and I’m very open with my patients. They need to understand that,” Dr. Matossian said. “It is a chronic condition for which they will need treatment forever. Their symptoms will improve if they stay compliant with their daily regimen.” Dr. Bunya said that while patients will likely be on some sort of treatment for life, once they find an effective regimen, it can greatly improve their quality of life. “In addition, dry eye has received increased interest from pharmaceutical companies in recent years, so I am hopeful that with more research, we will find more effective therapeutic options,” she said. EWAP Editors’ note: Dr. Bunya is William F. Norris and George E. de Schweinitz Associate Professor of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, and declared no relevant financial interests. Dr. Gupta is Managing Director, Triangle Eye Consultants, Cary, North Carolina, and has interests with Allergan, Novartis, and Oyster Point. Dr. Matossian is Founder, Matossian Eye Associates, Doylestown, Pennsylvania, who has interests with Alcon, BlephEx, Johnson & Johnson Vision, Physician Recommended Nutriceuticals, and Sight Sciences.
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