Surgical management of moderate to high myopia

Faculty Medicine Year: 2006
Type of Publication: Theses Pages: 164
Authors:
BibID 3201173
Keywords : Surgical management , moderate , high myopia    
Abstract:
SUMMARYAs refractive surgery gets simpler, safer, more predictable and more effective, it becomes more popular. While cases of simple myopia are usually easy to handle and get satisfactory results when corrected with excimer laser, those with high myopia still represent some challenges.To get the best possible outcome, the surgical plan should be tailored individually to suit each particular case with its peculiar characteristics regarding patients age, activities, visual needs, expectations and of course not the least his own eye parameters.In an attempt to better understand this issue, this study was conducted including ninety eyes of 48 patients, 22 males (45.8 %) and 26 (54.2%) females with a mean age of 40.66±12.03 (range 20 to 63) years and mean spherical equivalent of -12.67±4.64 (range -24 to -7.5) diopters. They were divided into three equal groups.The first group (A) underwent phakic intraocular lens implantation namely Kelman duet lens which is an angle supported anterior chamber phakic lens with rigid tripod haptic and foldable optic that can be injected through a self sealed clear corneal incision of as small size as two mm to be assembled to the previously implanted haptic.The second group (B) under went LASIK after doing the necessary investigations to exclude keratoconus suspects and to make sure that the cornea has enough thickness to allow complete correction of the refractive error in an ablation diameter that matches the scotopic pupil size.The third group (C) underwent clear lens extraction using micro-incision cataract surgery followed by implantation of acrylic foldable posterior chamber IOLs.The mean efficacy index three months postoperatively was 0.99, 0.874 and 0.916 in group A, B and C respectively. UCVA of 0.5 (6/12) or better was achieved in 80%, 93.33%, 63.3% of cases of group A, B and C respectively, while UCVA of 1.0 (6/6) was achieved in 16.67% and 33.3% of cases of group A and B.The mean postoperative safety index was 1.268, 1.03 and 1.249 in group A, B and C respectively. BCVA of 0.5 (6/12) or better was achieved in all cases however, 50%, 60% and 26.67% of cases in group A, B and C respectively achieved postoperative BCVA of 1.0 (6/6)Postoperative spherical equivalent within one diopter of emmetropia was achieved in 76.67%, 86.67%, 70% of cases in group A, B and C respectively. Postoperative defocus equivalent equal to or less than one diopter was achieved in 50%, 80% and 60% of cases group A, B and C respectively.The contrast sensitivity curves improved in the first postoperative month in all spatial frequencies in cases of group A and C without significant change in the subsequent visits. However; in cases of group B the contrast sensitivity curves decreased in the first postoperative month in all spatial frequencies, then improved at the third month visit to the preoperative level to exceed it in the sixth month without significant change in the subsequent ninth month visit.There was transient rise in IOP in cases of group A and C during the first postoperative week however; in group B IOP showed significant decline all through the follow up period.There was statistically significant loss of endothelial cells at one and nine months postoperatively however, the degree of loss varied in different groups. The loss in the mean endothelial cell count from preoperative level to the first month postoperatively was 6.29%, 1.56% and 9.78% and from the first month to the ninth month postoperatively was 0.99%, 1.28% and 0.92% in group A, B and C respectively.Regarding complications; in group (A), 6.67% of cases developed mild intraoperative hyphaema. Pupil ovalization occurred in 6.67% of cases, In 3.33% of cases rotation of the lens occurred due to too short haptics. In group (B), 3.33% of cases had decentered flap 3.33 % had decentered ablation. Interface deposits as well as bleeding to the interface were observed in 6.67%. The incidence of epithelial ingrowth, DLK and flap stria was 3.33% where as that of pseudoDLK was 6.67%. while in group (C), 3.33% of cases had intraoperative iris trauma while developed 6.67% posterior capsule opacification.CONCLUSIONSurgical correction of moderate to high myopia proved to be effective, safe and predictable. The choice of the procedure should be based on the patient’s condition, the surgeon’s expertise as well as the resources of the health care facility. The main procedures for correction of high myopia are Phakic IOLs, LASIK and clear lens extraction. Each of these procedures has its own indications, precautions as well as its most feared complications.Phakic IOLs despite the excellent initial outcome in terms of predictability and quality of vision imply certain risk for endothelial damage therefore should be followed up regularly. Phakic IOL should be removed as soon as serious decline in endothelial cell density occurs. As large proportion of high myopes will develop cataract, care should be taken to interfere before endothelial cell count decreases below safe limit for performing cataract extraction. The younger the patient at time of PIOL implantation, the higher the endothelial cell count required before PIOL implantation.LASIK is less invasive but irreversible procedure. Concerns about LASIK include degradation in quality of vision especially with marked flattening of the cornea which directly increases the higher order aberrations, the compromise between the optical zone and the possible correction respecting the minimal residual stromal bed. At any cost the risk of post LASIK keratectasia, the most devastating complication of LASIK nowadays, should be minimized. It should be kept in mind that theoretical calculations do not make up for the common error in the flap thickness.Clear lens extraction is more appealing in patients over forty five years especially if there is lens sclerosis as phakic IOL may enhance the cataract. LASIK also complicates IOL calculation should cataract progress necessitating removal. CLE should be performed through as small incision as possible to decrease the fluctuation in anterior chamber depth. Complete cortical clean up as well as capsular polishing must be performed to decrease the incidence of posterior capsular opacification and consequently YAG laser capsulotomy which is a very important added risk factor for retinal detachment in high myopes.Finally, due to the possible risks and elective nature of these procedures, they should only be offered to patients who refuse glasses and do not tolerate contact lenses. Clear explanation and proper informed consent is mandatory in every case.SUMMARYAs refractive surgery gets simpler, safer, more predictable and more effective, it becomes more popular. While cases of simple myopia are usually easy to handle and get satisfactory results when corrected with excimer laser, those with high myopia still represent some challenges.To get the best possible outcome, the surgical plan should be tailored individually to suit each particular case with its peculiar characteristics regarding patients age, activities, visual needs, expectations and of course not the least his own eye parameters.In an attempt to better understand this issue, this study was conducted including ninety eyes of 48 patients, 22 males (45.8 %) and 26 (54.2%) females with a mean age of 40.66±12.03 (range 20 to 63) years and mean spherical equivalent of -12.67±4.64 (range -24 to -7.5) diopters. They were divided into three equal groups.The first group (A) underwent phakic intraocular lens implantation namely Kelman duet lens which is an angle supported anterior chamber phakic lens with rigid tripod haptic and foldable optic that can be injected through a self sealed clear corneal incision of as small size as two mm to be assembled to the previously implanted haptic.The second group (B) under went LASIK after doing the necessary investigations to exclude keratoconus suspects and to make sure that the cornea has enough thickness to allow complete correction of the refractive error in an ablation diameter that matches the scotopic pupil size.The third group (C) underwent clear lens extraction using micro-incision cataract surgery followed by implantation of acrylic foldable posterior chamber IOLs.The mean efficacy index three months postoperatively was 0.99, 0.874 and 0.916 in group A, B and C respectively. UCVA of 0.5 (6/12) or better was achieved in 80%, 93.33%, 63.3% of cases of group A, B and C respectively, while UCVA of 1.0 (6/6) was achieved in 16.67% and 33.3% of cases of group A and B.The mean postoperative safety index was 1.268, 1.03 and 1.249 in group A, B and C respectively. BCVA of 0.5 (6/12) or better was achieved in all cases however, 50%, 60% and 26.67% of cases in group A, B and C respectively achieved postoperative BCVA of 1.0 (6/6)Postoperative spherical equivalent within one diopter of emmetropia was achieved in 76.67%, 86.67%, 70% of cases in group A, B and C respectively. Postoperative defocus equivalent equal to or less than one diopter was achieved in 50%, 80% and 60% of cases group A, B and C respectively.The contrast sensitivity curves improved in the first postoperative month in all spatial frequencies in cases of group A and C without significant change in the subsequent visits. However; in cases of group B the contrast sensitivity curves decreased in the first postoperative month in all spatial frequencies, then improved at the third month visit to the preoperative level to exceed it in the sixth month without significant change in the subsequent ninth month visit.There was transient rise in IOP in cases of group A and C during the first postoperative week however; in group B IOP showed significant decline all through the follow up period.There was statistically significant loss of endothelial cells at one and nine months postoperatively however, the degree of loss varied in different groups. The loss in the mean endothelial cell count from preoperative level to the first month postoperatively was 6.29%, 1.56% and 9.78% and from the first month to the ninth month postoperatively was 0.99%, 1.28% and 0.92% in group A, B and C respectively.Regarding complications; in group (A), 6.67% of cases developed mild intraoperative hyphaema. Pupil ovalization occurred in 6.67% of cases, In 3.33% of cases rotation of the lens occurred due to too short haptics. In group (B), 3.33% of cases had decentered flap 3.33 % had decentered ablation. Interface deposits as well as bleeding to the interface were observed in 6.67%. The incidence of epithelial ingrowth, DLK and flap stria was 3.33% where as that of pseudoDLK was 6.67%. while in group (C), 3.33% of cases had intraoperative iris trauma while developed 6.67% posterior capsule opacification.CONCLUSIONSurgical correction of moderate to high myopia proved to be effective, safe and predictable. The choice of the procedure should be based on the patient’s condition, the surgeon’s expertise as well as the resources of the health care facility. The main procedures for correction of high myopia are Phakic IOLs, LASIK and clear lens extraction. Each of these procedures has its own indications, precautions as well as its most feared complications.Phakic IOLs despite the excellent initial outcome in terms of predictability and quality of vision imply certain risk for endothelial damage therefore should be followed up regularly. Phakic IOL should be removed as soon as serious decline in endothelial cell density occurs. As large proportion of high myopes will develop cataract, care should be taken to interfere before endothelial cell count decreases below safe limit for performing cataract extraction. The younger the patient at time of PIOL implantation, the higher the endothelial cell count required before PIOL implantation.LASIK is less invasive but irreversible procedure. Concerns about LASIK include degradation in quality of vision especially with marked flattening of the cornea which directly increases the higher order aberrations, the compromise between the optical zone and the possible correction respecting the minimal residual stromal bed. At any cost the risk of post LASIK keratectasia, the most devastating complication of LASIK nowadays, should be minimized. It should be kept in mind that theoretical calculations do not make up for the common error in the flap thickness.Clear lens extraction is more appealing in patients over forty five years especially if there is lens sclerosis as phakic IOL may enhance the cataract. LASIK also complicates IOL calculation should cataract progress necessitating removal. CLE should be performed through as small incision as possible to decrease the fluctuation in anterior chamber depth. Complete cortical clean up as well as capsular polishing must be performed to decrease the incidence of posterior capsular opacification and consequently YAG laser capsulotomy which is a very important added risk factor for retinal detachment in high myopes.Finally, due to the possible risks and elective nature of these procedures, they should only be offered to patients who refuse glasses and do not tolerate contact lenses. Clear explanation and proper informed consent is mandatory in every case.SUMMARYAs refractive surgery gets simpler, safer, more predictable and more effective, it becomes more popular. While cases of simple myopia are usually easy to handle and get satisfactory results when corrected with excimer laser, those with high myopia still represent some challenges.To get the best possible outcome, the surgical plan should be tailored individually to suit each particular case with its peculiar characteristics regarding patients age, activities, visual needs, expectations and of course not the least his own eye parameters.In an attempt to better understand this issue, this study was conducted including ninety eyes of 48 patients, 22 males (45.8 %) and 26 (54.2%) females with a mean age of 40.66±12.03 (range 20 to 63) years and mean spherical equivalent of -12.67±4.64 (range -24 to -7.5) diopters. They were divided into three equal groups.The first group (A) underwent phakic intraocular lens implantation namely Kelman duet lens which is an angle supported anterior chamber phakic lens with rigid tripod haptic and foldable optic that can be injected through a self sealed clear corneal incision of as small size as two mm to be assembled to the previously implanted haptic.The second group (B) under went LASIK after doing the necessary investigations to exclude keratoconus suspects and to make sure that the cornea has enough thickness to allow complete correction of the refractive error in an ablation diameter that matches the scotopic pupil size.The third group (C) underwent clear lens extraction using micro-incision cataract surgery followed by implantation of acrylic foldable posterior chamber IOLs.The mean efficacy index three months postoperatively was 0.99, 0.874 and 0.916 in group A, B and C respectively. UCVA of 0.5 (6/12) or better was achieved in 80%, 93.33%, 63.3% of cases of group A, B and C respectively, while UCVA of 1.0 (6/6) was achieved in 16.67% and 33.3% of cases of group A and B.The mean postoperative safety index was 1.268, 1.03 and 1.249 in group A, B and C respectively. BCVA of 0.5 (6/12) or better was achieved in all cases however, 50%, 60% and 26.67% of cases in group A, B and C respectively achieved postoperative BCVA of 1.0 (6/6)Postoperative spherical equivalent within one diopter of emmetropia was achieved in 76.67%, 86.67%, 70% of cases in group A, B and C respectively. Postoperative defocus equivalent equal to or less than one diopter was achieved in 50%, 80% and 60% of cases group A, B and C respectively.The contrast sensitivity curves improved in the first postoperative month in all spatial frequencies in cases of group A and C without significant change in the subsequent visits. However; in cases of group B the contrast sensitivity curves decreased in the first postoperative month in all spatial frequencies, then improved at the third month visit to the preoperative level to exceed it in the sixth month without significant change in the subsequent ninth month visit.There was transient rise in IOP in cases of group A and C during the first postoperative week however; in group B IOP showed significant decline all through the follow up period.There was statistically significant loss of endothelial cells at one and nine months postoperatively however, the degree of loss varied in different groups. The loss in the mean endothelial cell count from preoperative level to the first month postoperatively was 6.29%, 1.56% and 9.78% and from the first month to the ninth month postoperatively was 0.99%, 1.28% and 0.92% in group A, B and C respectively.Regarding complications; in group (A), 6.67% of cases developed mild intraoperative hyphaema. Pupil ovalization occurred in 6.67% of cases, In 3.33% of cases rotation of the lens occurred due to too short haptics. In group (B), 3.33% of cases had decentered flap 3.33 % had decentered ablation. Interface deposits as well as bleeding to the interface were observed in 6.67%. The incidence of epithelial ingrowth, DLK and flap stria was 3.33% where as that of pseudoDLK was 6.67%. while in group (C), 3.33% of cases had intraoperative iris trauma while developed 6.67% posterior capsule opacification.CONCLUSIONSurgical correction of moderate to high myopia proved to be effective, safe and predictable. The choice of the procedure should be based on the patient’s condition, the surgeon’s expertise as well as the resources of the health care facility. The main procedures for correction of high myopia are Phakic IOLs, LASIK and clear lens extraction. Each of these procedures has its own indications, precautions as well as its most feared complications.Phakic IOLs despite the excellent initial outcome in terms of predictability and quality of vision imply certain risk for endothelial damage therefore should be followed up regularly. Phakic IOL should be removed as soon as serious decline in endothelial cell density occurs. As large proportion of high myopes will develop cataract, care should be taken to interfere before endothelial cell count decreases below safe limit for performing cataract extraction. The younger the patient at time of PIOL implantation, the higher the endothelial cell count required before PIOL implantation.LASIK is less invasive but irreversible procedure. Concerns about LASIK include degradation in quality of vision especially with marked flattening of the cornea which directly increases the higher order aberrations, the compromise between the optical zone and the possible correction respecting the minimal residual stromal bed. At any cost the risk of post LASIK keratectasia, the most devastating complication of LASIK nowadays, should be minimized. It should be kept in mind that theoretical calculations do not make up for the common error in the flap thickness.Clear lens extraction is more appealing in patients over forty five years especially if there is lens sclerosis as phakic IOL may enhance the cataract. LASIK also complicates IOL calculation should cataract progress necessitating removal. CLE should be performed through as small incision as possible to decrease the fluctuation in anterior chamber depth. Complete cortical clean up as well as capsular polishing must be performed to decrease the incidence of posterior capsular opacification and consequently YAG laser capsulotomy which is a very important added risk factor for retinal detachment in high myopes.Finally, due to the possible risks and elective nature of these procedures, they should only be offered to patients who refuse glasses and do not tolerate contact lenses. Clear explanation and proper informed consent is mandatory in every case.SUMMARYAs refractive surgery gets simpler, safer, more predictable and more effective, it becomes more popular. While cases of simple myopia are usually easy to handle and get satisfactory results when corrected with excimer laser, those with high myopia still represent some challenges.To get the best possible outcome, the surgical plan should be tailored individually to suit each particular case with its peculiar characteristics regarding patients age, activities, visual needs, expectations and of course not the least his own eye parameters.In an attempt to better understand this issue, this study was conducted including ninety eyes of 48 patients, 22 males (45.8 %) and 26 (54.2%) females with a mean age of 40.66±12.03 (range 20 to 63) years and mean spherical equivalent of -12.67±4.64 (range -24 to -7.5) diopters. They were divided into three equal groups.The first group (A) underwent phakic intraocular lens implantation namely Kelman duet lens which is an angle supported anterior chamber phakic lens with rigid tripod haptic and foldable optic that can be injected through a self sealed clear corneal incision of as small size as two mm to be assembled to the previously implanted haptic.The second group (B) under went LASIK after doing the necessary investigations to exclude keratoconus suspects and to make sure that the cornea has enough thickness to allow complete correction of the refractive error in an ablation diameter that matches the scotopic pupil size.The third group (C) underwent clear lens extraction using micro-incision cataract surgery followed by implantation of acrylic foldable posterior chamber IOLs.The mean efficacy index three months postoperatively was 0.99, 0.874 and 0.916 in group A, B and C respectively. UCVA of 0.5 (6/12) or better was achieved in 80%, 93.33%, 63.3% of cases of group A, B and C respectively, while UCVA of 1.0 (6/6) was achieved in 16.67% and 33.3% of cases of group A and B.The mean postoperative safety index was 1.268, 1.03 and 1.249 in group A, B and C respectively. BCVA of 0.5 (6/12) or better was achieved in all cases however, 50%, 60% and 26.67% of cases in group A, B and C respectively achieved postoperative BCVA of 1.0 (6/6)Postoperative spherical equivalent within one diopter of emmetropia was achieved in 76.67%, 86.67%, 70% of cases in group A, B and C respectively. Postoperative defocus equivalent equal to or less than one diopter was achieved in 50%, 80% and 60% of cases group A, B and C respectively.The contrast sensitivity curves improved in the first postoperative month in all spatial frequencies in cases of group A and C without significant change in the subsequent visits. However; in cases of group B the contrast sensitivity curves decreased in the first postoperative month in all spatial frequencies, then improved at the third month visit to the preoperative level to exceed it in the sixth month without significant change in the subsequent ninth month visit.There was transient rise in IOP in cases of group A and C during the first postoperative week however; in group B IOP showed significant decline all through the follow up period.There was statistically significant loss of endothelial cells at one and nine months postoperatively however, the degree of loss varied in different groups. The loss in the mean endothelial cell count from preoperative level to the first month postoperatively was 6.29%, 1.56% and 9.78% and from the first month to the ninth month postoperatively was 0.99%, 1.28% and 0.92% in group A, B and C respectively.Regarding complications; in group (A), 6.67% of cases developed mild intraoperative hyphaema. Pupil ovalization occurred in 6.67% of cases, In 3.33% of cases rotation of the lens occurred due to too short haptics. In group (B), 3.33% of cases had decentered flap 3.33 % had decentered ablation. Interface deposits as well as bleeding to the interface were observed in 6.67%. The incidence of epithelial ingrowth, DLK and flap stria was 3.33% where as that of pseudoDLK was 6.67%. while in group (C), 3.33% of cases had intraoperative iris trauma while developed 6.67% posterior capsule opacification.CONCLUSIONSurgical correction of moderate to high myopia proved to be effective, safe and predictable. The choice of the procedure should be based on the patient’s condition, the surgeon’s expertise as well as the resources of the health care facility. The main procedures for correction of high myopia are Phakic IOLs, LASIK and clear lens extraction. Each of these procedures has its own indications, precautions as well as its most feared complications.Phakic IOLs despite the excellent initial outcome in terms of predictability and quality of vision imply certain risk for endothelial damage therefore should be followed up regularly. Phakic IOL should be removed as soon as serious decline in endothelial cell density occurs. As large proportion of high myopes will develop cataract, care should be taken to interfere before endothelial cell count decreases below safe limit for performing cataract extraction. The younger the patient at time of PIOL implantation, the higher the endothelial cell count required before PIOL implantation.LASIK is less invasive but irreversible procedure. Concerns about LASIK include degradation in quality of vision especially with marked flattening of the cornea which directly increases the higher order aberrations, the compromise between the optical zone and the possible correction respecting the minimal residual stromal bed. At any cost the risk of post LASIK keratectasia, the most devastating complication of LASIK nowadays, should be minimized. It should be kept in mind that theoretical calculations do not make up for the common error in the flap thickness.Clear lens extraction is more appealing in patients over forty five years especially if there is lens sclerosis as phakic IOL may enhance the cataract. LASIK also complicates IOL calculation should cataract progress necessitating removal. CLE should be performed through as small incision as possible to decrease the fluctuation in anterior chamber depth. Complete cortical clean up as well as capsular polishing must be performed to decrease the incidence of posterior capsular opacification and consequently YAG laser capsulotomy which is a very important added risk factor for retinal detachment in high myopes.Finally, due to the possible risks and elective nature of these procedures, they should only be offered to patients who refuse glasses and do not tolerate contact lenses. Clear explanation and proper informed consent is mandatory in every case.SUMMARYAs refractive surgery gets simpler, safer, more predictable and more effective, it becomes more popular. While cases of simple myopia are usually easy to handle and get satisfactory results when corrected with excimer laser, those with high myopia still represent some challenges.To get the best possible outcome, the surgical plan should be tailored individually to suit each particular case with its peculiar characteristics regarding patients age, activities, visual needs, expectations and of course not the least his own eye parameters.In an attempt to better understand this issue, this study was conducted including ninety eyes of 48 patients, 22 males (45.8 %) and 26 (54.2%) females with a mean age of 40.66±12.03 (range 20 to 63) years and mean spherical equivalent of -12.67±4.64 (range -24 to -7.5) diopters. They were divided into three equal groups.The first group (A) underwent phakic intraocular lens implantation namely Kelman duet lens which is an angle supported anterior chamber phakic lens with rigid tripod haptic and foldable optic that can be injected through a self sealed clear corneal incision of as small size as two mm to be assembled to the previously implanted haptic.The second group (B) under went LASIK after doing the necessary investigations to exclude keratoconus suspects and to make sure that the cornea has enough thickness to allow complete correction of the refractive error in an ablation diameter that matches the scotopic pupil size.The third group (C) underwent clear lens extraction using micro-incision cataract surgery followed by implantation of acrylic foldable posterior chamber IOLs.The mean efficacy index three months postoperatively was 0.99, 0.874 and 0.916 in group A, B and C respectively. UCVA of 0.5 (6/12) or better was achieved in 80%, 93.33%, 63.3% of cases of group A, B and C respectively, while UCVA of 1.0 (6/6) was achieved in 16.67% and 33.3% of cases of group A and B.The mean postoperative safety index was 1.268, 1.03 and 1.249 in group A, B and C respectively. BCVA of 0.5 (6/12) or better was achieved in all cases however, 50%, 60% and 26.67% of cases in group A, B and C respectively achieved postoperative BCVA of 1.0 (6/6)Allen, T.D. and Griffin, J.E. (1984): Endocrine studies in patients with advanced hypospadias. J Urol; 131: 310-314.Allera, A.; Herbst, M.A. and Griffin, J.E. et al. (1995): Mutations of the androgen receptor coding sequence are infrequent in patients with isolated hypospadias. J Clin Endocrinol Metab; 80: 2697.Arap, S.; Mitre, A.I. and DeGoes, G.M. (1984): Modified meatal advancement and glanuloplasty repair of distal hypospadias. J Urol; 131: 1140-1141.Barcat, J. (1973): Current concepts of treatment. Boston, Little, Brow 
   
     
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