EyeWorld India March 2019 Issue

3 EWAP EDITORIAL March 2019 I t gives me immense pleasure to present to you the latest issue of the scientifically enriched EyeWorld Asia-Pacific . Our cover feature focuses on revisiting astigmatism, from its accurate measurement to its correction by corneal and lenticular approaches. The importance of a smooth ocular surface for cataract and refractive surgeries cannot be overemphasised. The most common challenges faced are severe dry eye, ocular surface issues caused by long-term anti-glaucoma medications, and neurotrophic keratitis. We have our experts opining on each of the above issues. Our next section on cataract and IOLs starts with the all- important differentiation between TASS and endophthalmitis in the clinic. Our specialist gives his method of implanting a capsular tension ring in a case of zonular weakness. The next article describes the impact of different cataract incisions on wound integrity. Most of us may be implanting toric IOLs, but what do we do if we notice that it has been rotated postop? Read our article to see what the experts have to say. And did u know there is a surgical correction for negative dysphotopsia? According to our specialists, a secondary (reverse) anterior optic capture can remedy the situation. We end this section with an article on the importance of MSICS in the current era of phacoemulsfication. Our refractive section starts with an article on the latest enhanced depth of focus (EDOF) lenses that provide nanovision at all distances. The next article describes the guidelines on using toric IOLs in keratoconus. This is followed by articles on the importance of macular OCT in a refractive surgery patient and thin LASIK. Are you confused about using Xiidra for your dry eye patient? Our experts provide their clinical experiences. Meanwhile, one may occasionally come across a corneal ulcer patient unresponsive to fluoroquinolones. Our next article provides solutions. In our section on devices describes Triggerfish, which is among the latest 24-hour IOP measurement devices. We conclude this issue with an article on the use of biologicals in dry eye nonresponsive to the traditional therapies. As always I would like to end with a quote from Tirukkural: T he focus of this month’s edition of EyeWorld Asia-Pacific is a reevaluation of the management of preexisting astigmatism in patients undergoing cataract surgery. Personally, there are few innovations that have had as significant an impact as the introduction of toric intraocular lenses. When I first began using toric intraocular lenses in 2006, the threshold for considering a toric intraocular lens (IOL) was considerably higher than today. The ability to accurately predict astigmatic outcomes has improved but the most dramatic change when I look back is the increased usage of toric IOLs. In my own practice these lenses are used in approximately 80% of cases and I target less than a 0.5 D of residual astigmatism in all patients. It is a myth that residual astigmatism is of optical benefit and it has been clearly demonstrated that astigmatism affects contrast and reading speed. Any benefit in terms of depth of focus depends on a myopic spherical outcome and the latter without residual astigmatism is more effective than the equivalent amount of myopic defocus associated with astigmatism. There is nothing special about astigmatic defocus and indeed the impact on quality of vision is greater than the equivalent spherical myopic defocus. The error in predicting residual astigmatism is similar to that of predicting spherical errors. The absolute error is approximately 0.3 D with a standard deviation of 0.19 D. Achieving an astigmatic outcome less than 0.5 D therefore demands a target close to zero, as we are accustomed to in targeting spherical defocus. It seems to me that there is little sense in focusing on perfect spherical outcomes if similar attention is not applied to astigmatism. A target of less than 0.5 D residual astigmatism in all patients requires accurate alignment and an understanding of the impact of surgically induced astigmatism. One of the unique features of the Barrett toric calculator on the APACRS website is the integrated K calculator. This simplifies the interpretation of utilizing multiple instruments. Up to three different devices can be entered and the K calculator will provide a median vector considering both the axis and meridian of the astigmatism measured by different devices. Data analysis shows this offers significant improvement and I utilize this method in all my cases. Accurate alignment is facilitated by image-guided systems but similar accuracy can be achieved with the inexpensive toric cam app and dual axis marker. Surgical incisions in the cornea have an unpredictable impact on astigmatism. Even the impact of a relatively small corneal limbal incision is unpredictable. Although the mean or median magnitude of the induced astigmatism may be in the order of 0.3 to 0.4 D, the direction or meridian is quite variable. The centroid value which encompasses both the magnitude and direction of the vector of surgically induced astigmatism is typically in the range of 0.1 D and should be utilized in toric calculators for optimum prediction. I would recommend a toric calculator be used in all patients undergoing cataract surgery. If one is not accustomed to using this protocol the number of patients requiring a toric lens will be significantly underestimated. The most frequently used toric lens in my practice is a low-diopter T2 with a 1-D cylinder power. These low powers are not available in all regions, particularly the U.S. Although astigmatic keratotomy is used as an alternative, several studies have shown this is less predictable and effective than using low toric cylinder powers. The use of toric lenses in the U.S. is significantly lower than in countries such as Australia and I suspect there will be an exponential growth when low dioptric implants become available. Leaving a patient with significant astigmatism may have been acceptable in an era when extracapsular cataract surgery was widely practiced but today with small incision cataract surgery and phacoemulsification I would suggest that an attempt to achieve a target of less than 0.5 D in all patients is preferable and may become a standard of care. EWAP Eliminating astigmatism Graham Barrett Chief Medical Editor EyeWorld Asia-Pacific S. Natarajan, MD Regional Managing Director EyeWorld Asia-Pacific u££££ ££ £££ The fertile world which endows us with breathing air illustrates that there is no sorrow for the compassionate. ( Tirukkural, Chapter 25, Quote 245) EWAP