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Comments on corneal astigmatic marking methods
LETTERS
Comments on corneal astigmatic marking methods In their recent paper,1 Popp et al. investigated and compared 4 methods of corneal marking for astigmatism correction when the surgeon intended to correct astigmatism surgically with or without cataract surgery: pendular marker, bubble marker, tonometer marker, and scratching the cornea with an insulin needle at the slitlamp. We propose a different and simple technique for the same purpose: marking the astigmatic axis directly with the patient sitting at the slitlamp. In this technique, the slit light of the slitlamp is turned in the steep astigmatic meridian in the orthograde position using the rotator switch of the slit light. The patient is instructed to look at a distant target at head height with the fellow eye, and the slit is centered on the apex of the cornea. Then, 2 tips of the astigmatic meridian are marked where they cross at the limbus 180 degrees away with a marking pen. As ophthalmologists know, the rotator switch of the slitlamp is ordinarily used at the 90-degree position to see the slit light vertically. When the rotator switch is turned to the right side of the examiner, the axis of the slit light turns from 90 degrees toward 0 degree. When the rotator switch is turned to the left side, the axis of the slit light turns from 90 degrees toward 180 degrees. In this way, the delicate alignment to find the exact meridian can be made. The main advantage of this technique is simplicity. We mark the intended steep astigmatic axis directly and also the surgical entry site, if we desire. We need only a slitlamp and a marking pen so we can perform the task at 1 time instead of 2. H€ useyin Bayramlar, MD Yas¸ar Da g, MD Fariz Sadigov, MD Umraniye, Istanbul, Turkiye REFERENCE 1. Popp N, Hirnschall N, Maedel S, Findl O. Evaluation of 4 corneal astigmatic marking methods. J Cataract Refract Surg 2012; 38:2094–2099
- The study by Popp et al. comparing 4 methods of marking the horizontal meridian provides informative data that can affect the method used when planning procedures to correct corneal astigmatism. The authors could use their existing data to explore 2 further factors. They noted whether rotational misalignment was clockwise or counterclockwise. It is plausible to hypothesize that a method that, for example, 966
Q 2013 ASCRS and ESCRS Published by Elsevier Inc.
predisposes to a clockwise deviation in the left eye would be more likely to produce a counterclockwise deviation in the right eye. This would occur whether the deviation was related to cyclotorsion or to positioning factors resulting from using the right hand for the left eye and the left hand for the right eye. The authors state that there was no significant difference between right and left eyes in each group; this presumably was for the magnitude of the deviation. It would be interesting to check whether there was a difference related to the axis of rotational deviation: Was the proportion of clockwise deviations equivalent for right and left eyes in each group? Such information would be useful as efforts could be made to compensate for the misalignment depending on which eye was being marked. For 3 of the 4 methods, the examiner’s experience was 10 prior applications only, and one may postulate that a learning curve still existed. Thus, it would be interesting to check for a trend over time: Did the extent of rotational or vertical misalignment diminish with time? This may elucidate how many attempts might be needed before additional applications make little difference in accuracy. It may be that the numbers are too small to detect a significant effect in either analysis (effect of laterality on axis of rotational misalignment and effect of learning on accuracy) but should a significant relationship emerge, it would be informative. Alternatively, an exploration of the 2 potential effects could form the basis for a future larger study. Omar A. Mahroo, PhD, FRCOphth Bruno Zuberbuhler, MD, FRCOphth London, United Kingdom - In the comparison of 4 corneal astigmatic marking methods (marking at the slitlamp, a pendular marker, a bubble marker, and a tonometer marker), the least vertical misalignment was observed with the slitlamp marker. Using this method, Popp et al. scratched the cornea at the limbus with 0.4 20.0 mm subcutaneous needle and then stained the microabrasions with a sterile blue marker. We have been using the slitlamp method of axis marking for a long time but with a slight modification. The initial steps of slitlamp marking are carried out in a manner similar to the steps described by Popp et al.; however, instead of using a marker, we scratch the corneoscleral limbal area at the insertion of the conjunctiva with a 30-gauge tuberculin syringe until a tiny red blood mark appears (Figure 1). The advantage is that this blood mark on the cornea is not affected by the peribulbar block, whereas the ink mark can disperse or disappear when the peribulbar block is administered. 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2013.02.001
Comments on corneal astigmatic marking methods In their recent paper,1 Popp et al. investigated and compared 4 methods of corneal marking for astigmatism correction when the surgeon intended to correct astigmatism surgically with or without cataract surgery: pendular marker, bubble marker, tonometer marker, and scratching the cornea with an insulin needle at the slitlamp. We propose a different and simple technique for the same purpose: marking the astigmatic axis directly with the patient sitting at the slitlamp. In this technique, the slit light of the slitlamp is turned in the steep astigmatic meridian in the orthograde position using the rotator switch of the slit light. The patient is instructed to look at a distant target at head height with the fellow eye, and the slit is centered on the apex of the cornea. Then, 2 tips of the astigmatic meridian are marked where they cross at the limbus 180 degrees away with a marking pen. As ophthalmologists know, the rotator switch of the slitlamp is ordinarily used at the 90-degree position to see the slit light vertically. When the rotator switch is turned to the right side of the examiner, the axis of the slit light turns from 90 degrees toward 0 degree. When the rotator switch is turned to the left side, the axis of the slit light turns from 90 degrees toward 180 degrees. In this way, the delicate alignment to find the exact meridian can be made. The main advantage of this technique is simplicity. We mark the intended steep astigmatic axis directly and also the surgical entry site, if we desire. We need only a slitlamp and a marking pen so we can perform the task at 1 time instead of 2. H€ useyin Bayramlar, MD Yas¸ar Da g, MD Fariz Sadigov, MD Umraniye, Istanbul, Turkiye REFERENCE 1. Popp N, Hirnschall N, Maedel S, Findl O. Evaluation of 4 corneal astigmatic marking methods. J Cataract Refract Surg 2012; 38:2094–2099
- The study by Popp et al. comparing 4 methods of marking the horizontal meridian provides informative data that can affect the method used when planning procedures to correct corneal astigmatism. The authors could use their existing data to explore 2 further factors. They noted whether rotational misalignment was clockwise or counterclockwise. It is plausible to hypothesize that a method that, for example, 966
Q 2013 ASCRS and ESCRS Published by Elsevier Inc.
predisposes to a clockwise deviation in the left eye would be more likely to produce a counterclockwise deviation in the right eye. This would occur whether the deviation was related to cyclotorsion or to positioning factors resulting from using the right hand for the left eye and the left hand for the right eye. The authors state that there was no significant difference between right and left eyes in each group; this presumably was for the magnitude of the deviation. It would be interesting to check whether there was a difference related to the axis of rotational deviation: Was the proportion of clockwise deviations equivalent for right and left eyes in each group? Such information would be useful as efforts could be made to compensate for the misalignment depending on which eye was being marked. For 3 of the 4 methods, the examiner’s experience was 10 prior applications only, and one may postulate that a learning curve still existed. Thus, it would be interesting to check for a trend over time: Did the extent of rotational or vertical misalignment diminish with time? This may elucidate how many attempts might be needed before additional applications make little difference in accuracy. It may be that the numbers are too small to detect a significant effect in either analysis (effect of laterality on axis of rotational misalignment and effect of learning on accuracy) but should a significant relationship emerge, it would be informative. Alternatively, an exploration of the 2 potential effects could form the basis for a future larger study. Omar A. Mahroo, PhD, FRCOphth Bruno Zuberbuhler, MD, FRCOphth London, United Kingdom - In the comparison of 4 corneal astigmatic marking methods (marking at the slitlamp, a pendular marker, a bubble marker, and a tonometer marker), the least vertical misalignment was observed with the slitlamp marker. Using this method, Popp et al. scratched the cornea at the limbus with 0.4 20.0 mm subcutaneous needle and then stained the microabrasions with a sterile blue marker. We have been using the slitlamp method of axis marking for a long time but with a slight modification. The initial steps of slitlamp marking are carried out in a manner similar to the steps described by Popp et al.; however, instead of using a marker, we scratch the corneoscleral limbal area at the insertion of the conjunctiva with a 30-gauge tuberculin syringe until a tiny red blood mark appears (Figure 1). The advantage is that this blood mark on the cornea is not affected by the peribulbar block, whereas the ink mark can disperse or disappear when the peribulbar block is administered. 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2013.02.001