- Email: [email protected]
August Consultation # 4
CONSULTATION SECTION
topography changes during the first 3 to 6 months compared to subsequent topography examinations. Brian S. Boxer Wachler, MD Beverly Hills, California, USA
- Of highest importance in this case is determining the primary cause of the decreased visual acuity in the left eye. Is it corneal ectasia and high cylinder or the nuclear sclerosis? Topography and pachymetry point to ectasia; however, a rigid gas-permeable (RGP) lens overrefraction would help to affirm whether the cataractous changes were enough to cause the patient’s symptoms. Ectasia after hyperopic LASIK is an uncommon complication, with only a few anecdotal reports. A review of the preoperative topography shows a ‘‘kissing fish’’ pattern described by William Trattler, MD, as forme fruste pellucid degeneration. This may be the genesis of an unstable cornea after laser ablation. The progression of corneal ectasia is not well known. Therefore, at present, I recommend treating by removing the cataract and replacing with a toric IOL if possible. I would treat any untolerated residual astigmatism with spectacles or a contact lens, including the new hybrid lens that has an RGP button and a soft hioxifilicon skirt. I would not perform any corneal relaxing incisions or do further surgery on this unstable cornea. Finally, if the ectasia progresses, one could consider Intacs, although most studies show only mild visual improvement; the device increases the ability to tolerate a contact lens. Still, this must be considered before a full-thickness corneal transplant. Debra G. Tennen, MD Agoura Hills, California, USA
- I am at a loss to explain the increase in with-the-rule astigmatism that occurred over the past 3 years in the left eye. The topographic map documents fairly symmetric bow-tie astigmatism with no localized areas of flattening or steepening to suggest an ectatic process or external pressure from something such as a chalazion, although I would look closely to make sure that there is no lesion of the eyelids. Both corneas are thinner inferocentrally than superocentrally, but I do not know what to make of this. The more hyperopic ablation was performed in the left eye and as such I would have expected more paracentral–midperipheral thinning in the left eye, which is not the case. The 2-month postsurgical topography documents significantly steeper simulated keratometry than the 6-year topographic maps of both eyes, which suggests the possibility of
epithelial hypertrophic induced corneal flattening in both eyes. Although there does not seem to be regression of the hyperopic effect in the right eye associated with the apparent corneal flattening, that may very well be explained by concomitant lens-induced myopia. That the SE in the left eye is now no different than it was 3 years ago, despite more prominent nuclear sclerosis than in the right eye, is difficult to interpret because the refraction may be inaccurate as a result of the reduced visual acuity. The patient obviously has a visually significant cataract in the left eye, which I would recommend she have removed. The 2 issues are how to derive the IOL calculations and what to do about the astigmatism. We have complete preoperative and post-LASIK information from before the development of the cataract to allow for the use of the historical method to calculate the IOL power. Various other methods have been recommended for calculating postLASIK IOL powers. I have had good success using Masket and Masket’s regression formula,1 wherein the IOL power calculated from the present keratometry is adjusted by the SE of the amount of laser correction multiplied by ( 0.326) C 0.101. I like to compare the predicted values of the aforementioned 2 methods before deciding on the IOL power to use, if anything wanting to err a little on the myopic side. I would aim for plano, although if the patient preferred she could always try for a monovision outcome as occurred with the original LASIK surgery. Because I do not know what has caused the astigmatism and whether it is a progressive phenomenon, I would advocate doing nothing for the astigmatism at the time of cataract surgery, preferring to wait at least 6 months to see what happens to the corneal and refractive astigmatism. Thereafter, a decision could be made regarding incisional surgery or excimer laser surgery either beneath the LASIK flap or by surface ablation with the intraoperative use of MMC to prevent haze formation. I would be reluctant to use a toric IOL because of the possibility of a change in the corneal astigmatism. Moreover, I would advocate using a monofocal IOL because of all the issues with the astigmatism. Irving M. Raber, MD Bala Cynwyd, Pennsylvania, USA REFERENCE 1. Masket S, Masket SE. Simple regression formula for intraocular lens power adjustment in eyes requiring cataract surgery after excimer laser photoablation. J Cataract Refract Surg 2006; 32:430–434
- According to the patient’s ophthalmic history, there is a decrease in visual performance 6 years after hyperopic LASIK for monovision that became clinically significant in the past 6 months. Visual acuities are justified by
J CATARACT REFRACT SURG - VOL 32, AUGUST 2006
1251
topography changes during the first 3 to 6 months compared to subsequent topography examinations. Brian S. Boxer Wachler, MD Beverly Hills, California, USA
- Of highest importance in this case is determining the primary cause of the decreased visual acuity in the left eye. Is it corneal ectasia and high cylinder or the nuclear sclerosis? Topography and pachymetry point to ectasia; however, a rigid gas-permeable (RGP) lens overrefraction would help to affirm whether the cataractous changes were enough to cause the patient’s symptoms. Ectasia after hyperopic LASIK is an uncommon complication, with only a few anecdotal reports. A review of the preoperative topography shows a ‘‘kissing fish’’ pattern described by William Trattler, MD, as forme fruste pellucid degeneration. This may be the genesis of an unstable cornea after laser ablation. The progression of corneal ectasia is not well known. Therefore, at present, I recommend treating by removing the cataract and replacing with a toric IOL if possible. I would treat any untolerated residual astigmatism with spectacles or a contact lens, including the new hybrid lens that has an RGP button and a soft hioxifilicon skirt. I would not perform any corneal relaxing incisions or do further surgery on this unstable cornea. Finally, if the ectasia progresses, one could consider Intacs, although most studies show only mild visual improvement; the device increases the ability to tolerate a contact lens. Still, this must be considered before a full-thickness corneal transplant. Debra G. Tennen, MD Agoura Hills, California, USA
- I am at a loss to explain the increase in with-the-rule astigmatism that occurred over the past 3 years in the left eye. The topographic map documents fairly symmetric bow-tie astigmatism with no localized areas of flattening or steepening to suggest an ectatic process or external pressure from something such as a chalazion, although I would look closely to make sure that there is no lesion of the eyelids. Both corneas are thinner inferocentrally than superocentrally, but I do not know what to make of this. The more hyperopic ablation was performed in the left eye and as such I would have expected more paracentral–midperipheral thinning in the left eye, which is not the case. The 2-month postsurgical topography documents significantly steeper simulated keratometry than the 6-year topographic maps of both eyes, which suggests the possibility of
epithelial hypertrophic induced corneal flattening in both eyes. Although there does not seem to be regression of the hyperopic effect in the right eye associated with the apparent corneal flattening, that may very well be explained by concomitant lens-induced myopia. That the SE in the left eye is now no different than it was 3 years ago, despite more prominent nuclear sclerosis than in the right eye, is difficult to interpret because the refraction may be inaccurate as a result of the reduced visual acuity. The patient obviously has a visually significant cataract in the left eye, which I would recommend she have removed. The 2 issues are how to derive the IOL calculations and what to do about the astigmatism. We have complete preoperative and post-LASIK information from before the development of the cataract to allow for the use of the historical method to calculate the IOL power. Various other methods have been recommended for calculating postLASIK IOL powers. I have had good success using Masket and Masket’s regression formula,1 wherein the IOL power calculated from the present keratometry is adjusted by the SE of the amount of laser correction multiplied by ( 0.326) C 0.101. I like to compare the predicted values of the aforementioned 2 methods before deciding on the IOL power to use, if anything wanting to err a little on the myopic side. I would aim for plano, although if the patient preferred she could always try for a monovision outcome as occurred with the original LASIK surgery. Because I do not know what has caused the astigmatism and whether it is a progressive phenomenon, I would advocate doing nothing for the astigmatism at the time of cataract surgery, preferring to wait at least 6 months to see what happens to the corneal and refractive astigmatism. Thereafter, a decision could be made regarding incisional surgery or excimer laser surgery either beneath the LASIK flap or by surface ablation with the intraoperative use of MMC to prevent haze formation. I would be reluctant to use a toric IOL because of the possibility of a change in the corneal astigmatism. Moreover, I would advocate using a monofocal IOL because of all the issues with the astigmatism. Irving M. Raber, MD Bala Cynwyd, Pennsylvania, USA REFERENCE 1. Masket S, Masket SE. Simple regression formula for intraocular lens power adjustment in eyes requiring cataract surgery after excimer laser photoablation. J Cataract Refract Surg 2006; 32:430–434
- According to the patient’s ophthalmic history, there is a decrease in visual performance 6 years after hyperopic LASIK for monovision that became clinically significant in the past 6 months. Visual acuities are justified by
J CATARACT REFRACT SURG - VOL 32, AUGUST 2006
1251