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LASIK in pediatric eyes: reply
LETTERS
6. The corneal topography may become very unsuitable for future contact lens use. In view of the fallacies of pediatric LASIK, these children are likely to have long-term regression, increase in the refractive error with age, significant glare, and decrease in contrast sensitivity, and persistance of the amblyogenic stimulus for which the surgery was performed in the first place. We do not think these children will have a long-term favorable outcome after LASIK.
We think LASIK is a safe and effective procedure in treating unilateral pediatric high myopia to prevent anisometropic amblyopia. Further large studies and longer follow-ups are required.—Amar Agarwal, MS, FRCS, FRCOphth
TANUJ DADA, MD RASIK B. VAJPAYEE, MBBS, MS New Delhi, India
he recent paper by Lesiewska-Junk and Kałuz˙ny1 was both interesting and intriguing. In 45 young pseudophakic patients, the authors found a small but significant mean decrease of 0.42 mm in the anterior chamber depth (ACD) associated with a mean pseudoaccommodation amplitude of 4.5 diopters (D). Furthermore, they found a significant relationship between the magnitude of the pseudoaccommodation and the anteriorly directed shift in the intraocular lens (IOL) position. It appears that the authors did not take into account the residual refractive error in each individual eye when making this comparson. Correcting for this and resubmitting their data to linear regression assuming pseudoaccommodation (Y) is dependent on shift in IOL position (X). The new least square line has the form:
References 1. Agarwal A, Agarwal A, Agarwal T, et al. Results of pediatric laser in situ keratomileusis. J Cataract Refract Surg 2000; 26:684 – 689 2. Pe´rez-Santonja JJ, Bellot J, Claramonte P, et al. Laser in situ keratomileusis to correct high myopia. J Cataract Refract Surg 1997; 23:372–285 3. Gu¨ell JL, Muller A. Laser in situ keratomileusis (LASIK) for myopia from –7 to –18 diopters. J Refract Surg 1996; 12:222–228 4. Knorz MC, Wiesinger B, Liermann A, et al. Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism. Ophthalmology 1998; 105:932–940 5. Chayet AS, Assil KK, Montes M, et al. Regression and its mechanisms after laser in situ keratomileusis in moderate and high myopia. Ophthalmology 1998; 105:1194 –1199
Reply: The comments by Drs. Dada and Vajpayee give us the opportunity to clarify some points. We agree with them that refractive errors in children are not stable and not all pediatric eyes are candidates for refractive surgery. In our study, LASIK was performed selectively in children with uniocular high myopia to prevent anisometropic amblyopia. The preferred mode of treatment with contact lenses is not appropriate in our country because of the socioeconomic conditions. The basic aim of preventing amblyopia is not achieved in these cases, since most cases discontinue contact lens wear. Eyes with refractive errors of more than –15.0 D were included in this study so that post-LASIK spectacles, if required, would produce minimal anisokonia and hence aid in binocular single vision. In our study, the operative zone was reduced to 4.0 mm to obtain maximum correction in only 2 eyes. We agree with Drs. Dada and Vajpayee that a reduced ablative zone diameter is likely to produce significant glare and problems with night vision, which are secondary to obtaining maximum correction. In these eyes, a marked regression is likely to occur beyond 12 months. We can tackle these cases by regular cycloplegic and manifest refraction and with another LASIK treatment if there is sufficient corneal thickness available. This is an accepted method of treating myopic regression. We agree with the authors that we should avoid eyes with keratometer values less than 40.0 D to prevent free caps.
Potential Source of Pseudoaccommodation in Young Pseudophakic Patients
T
Y ⫽ 2.8X ⫹ 3.1
(1)
共r ⫽ 0.362, P ⫽ .015兲
Equation 1 is peculiar because it predicts 3.1 D of pseudoaccommodation for no change in IOL position. The investigators offered no mathematical hypothesis of their own to account for the observations. However, they did mention Holladay’s assertion that a 1.0 mm shift in the position of a posterior chamber IOL along the optic axis toward the cornea will increase myopia and hence produce a pseudoaccommodative effect of 1.9 D.2 According to equation 1, ignoring the abscissa value of 3.1, a 1.0 mm shift is associated with a pseudoaccommodative effect of 2.8 D, ie, double the effect predicted by Holladay. Why is this? The authors rightfully point out the near pupil response could increase the depth of focus of the eye, thus contributing to the pseudoaccommodative effect. However, they did not offer values for this depth of focus effect nor did they report the probable error in the decision-making process when their patients were asked to indicate when the target letters became blurred during
J CATARACT REFRACT SURG—VOL 27, JANUARY 2001
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6. The corneal topography may become very unsuitable for future contact lens use. In view of the fallacies of pediatric LASIK, these children are likely to have long-term regression, increase in the refractive error with age, significant glare, and decrease in contrast sensitivity, and persistance of the amblyogenic stimulus for which the surgery was performed in the first place. We do not think these children will have a long-term favorable outcome after LASIK.
We think LASIK is a safe and effective procedure in treating unilateral pediatric high myopia to prevent anisometropic amblyopia. Further large studies and longer follow-ups are required.—Amar Agarwal, MS, FRCS, FRCOphth
TANUJ DADA, MD RASIK B. VAJPAYEE, MBBS, MS New Delhi, India
he recent paper by Lesiewska-Junk and Kałuz˙ny1 was both interesting and intriguing. In 45 young pseudophakic patients, the authors found a small but significant mean decrease of 0.42 mm in the anterior chamber depth (ACD) associated with a mean pseudoaccommodation amplitude of 4.5 diopters (D). Furthermore, they found a significant relationship between the magnitude of the pseudoaccommodation and the anteriorly directed shift in the intraocular lens (IOL) position. It appears that the authors did not take into account the residual refractive error in each individual eye when making this comparson. Correcting for this and resubmitting their data to linear regression assuming pseudoaccommodation (Y) is dependent on shift in IOL position (X). The new least square line has the form:
References 1. Agarwal A, Agarwal A, Agarwal T, et al. Results of pediatric laser in situ keratomileusis. J Cataract Refract Surg 2000; 26:684 – 689 2. Pe´rez-Santonja JJ, Bellot J, Claramonte P, et al. Laser in situ keratomileusis to correct high myopia. J Cataract Refract Surg 1997; 23:372–285 3. Gu¨ell JL, Muller A. Laser in situ keratomileusis (LASIK) for myopia from –7 to –18 diopters. J Refract Surg 1996; 12:222–228 4. Knorz MC, Wiesinger B, Liermann A, et al. Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism. Ophthalmology 1998; 105:932–940 5. Chayet AS, Assil KK, Montes M, et al. Regression and its mechanisms after laser in situ keratomileusis in moderate and high myopia. Ophthalmology 1998; 105:1194 –1199
Reply: The comments by Drs. Dada and Vajpayee give us the opportunity to clarify some points. We agree with them that refractive errors in children are not stable and not all pediatric eyes are candidates for refractive surgery. In our study, LASIK was performed selectively in children with uniocular high myopia to prevent anisometropic amblyopia. The preferred mode of treatment with contact lenses is not appropriate in our country because of the socioeconomic conditions. The basic aim of preventing amblyopia is not achieved in these cases, since most cases discontinue contact lens wear. Eyes with refractive errors of more than –15.0 D were included in this study so that post-LASIK spectacles, if required, would produce minimal anisokonia and hence aid in binocular single vision. In our study, the operative zone was reduced to 4.0 mm to obtain maximum correction in only 2 eyes. We agree with Drs. Dada and Vajpayee that a reduced ablative zone diameter is likely to produce significant glare and problems with night vision, which are secondary to obtaining maximum correction. In these eyes, a marked regression is likely to occur beyond 12 months. We can tackle these cases by regular cycloplegic and manifest refraction and with another LASIK treatment if there is sufficient corneal thickness available. This is an accepted method of treating myopic regression. We agree with the authors that we should avoid eyes with keratometer values less than 40.0 D to prevent free caps.
Potential Source of Pseudoaccommodation in Young Pseudophakic Patients
T
Y ⫽ 2.8X ⫹ 3.1
(1)
共r ⫽ 0.362, P ⫽ .015兲
Equation 1 is peculiar because it predicts 3.1 D of pseudoaccommodation for no change in IOL position. The investigators offered no mathematical hypothesis of their own to account for the observations. However, they did mention Holladay’s assertion that a 1.0 mm shift in the position of a posterior chamber IOL along the optic axis toward the cornea will increase myopia and hence produce a pseudoaccommodative effect of 1.9 D.2 According to equation 1, ignoring the abscissa value of 3.1, a 1.0 mm shift is associated with a pseudoaccommodative effect of 2.8 D, ie, double the effect predicted by Holladay. Why is this? The authors rightfully point out the near pupil response could increase the depth of focus of the eye, thus contributing to the pseudoaccommodative effect. However, they did not offer values for this depth of focus effect nor did they report the probable error in the decision-making process when their patients were asked to indicate when the target letters became blurred during
J CATARACT REFRACT SURG—VOL 27, JANUARY 2001
9