The effect of incisions for cataract on corneal curvature

Merriam, John C.; Zheng, Lei; Merriam, Joanna E.; Zaider, Marco; Lindström, Bo

doi:10.1016/s0161-6420(03)00537-2

Cited by 46 publications

(34 citation statements)

References 24 publications

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“…John Merriam C et al 8 in their study found that there is significant change in corneal curvature when incision is taken on temporal clear cornea. 9 Kurz S et al 10 found BCVA was 20/20 in microphaco and 20/25 in routine.…”

Section: Discussionmentioning

confidence: 95%

Surgical and Visual Outcome of Phacoemulsification Surgery (Routine) and Micro - Phaco (Bimanual Phaco): A Comparative Study

Sutaria¹,

Dhok²,

Mahatme³

et al. 2015

jemds

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Cataract surgery has evolved over the past few decades with progressive decrease in the size of the incision. Originally from 12 mm intracapsular incision to bimanual phacoemulsification (Micro-Phaco) that has incision size of just 700 microns. In the present comparative PROSPECTIVE study best corrected visual acuity postoperatively and surgically induced astigmatism were compared in routine Phacoemulsification technique and bimanual phaco (Micro-Phaco) 60 eyes were studied. There was no statistically significant difference in postoperative best corrected visual acuity (BCVA) of patients operated with Micro-Phaco or routine Phacoemulsification. There was difference in surgically induced astigmatism (SIA); average SIA in microphaco was 0.5972 as against 0.8328 in routine Phacoemulsification.

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Section: Discussionmentioning

confidence: 95%

Surgical and Visual Outcome of Phacoemulsification Surgery (Routine) and Micro - Phaco (Bimanual Phaco): A Comparative Study

Sutaria¹,

Dhok²,

Mahatme³

et al. 2015

jemds

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“…However, five years after surgery patients exhibited astigmatism in the reverse direction, with an average of -0.7 diopters change in the vertical meridian and +0.6 diopters change in the horizontal meridian compared to their pre-operative condition [1]. This is likely because the vision change in first weeks after surgery is heavily influenced by tissue swelling and the healing response, whereas the long term vision change may be due to permanent structural changes in the cornea.…”

Section: Resultsmentioning

confidence: 99%

“…For patients with pre-existing astigmatism, the astigmatism can be reduced or increased, depending on incision placement. Cornea surgeons have produced tables based on empirical observations of surgical results that allow them to predict the cornea curvature change that will result from a given incision [1]. However, a clear mechanical understanding of the causes of the observed changes does not exist.…”

Section: Introductionmentioning

confidence: 99%

Finite Element Model of Cornea Deformation

Crouch

Merriam²,

Crouch

2005

Lecture Notes in Computer Science

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Abstract. Cornea surgeons have observed that changes in cornea curvature can follow cataract surgery and cause astigmatism. The placement of surgical incisions has been shown to influence these curvature changes. Though empirical data has been collected about this phenomenon, a biomechanical model has not been employed in predicting post-surgical outcomes. This work implemented an incised finite element model of the eye to investigate factors influencing corneal shape after surgery. In particular, the effects of eye muscle forces and intra-ocular pressure were simulated. Cornea shape change was computed via finite element analysis, and the resulting change in cornea curvature was measured by fitting quadratic curves to the horizontal and vertical meridians of the cornea. Results suggest that these two sources of deforming force counteract each other and contribute to astigmatism in perpendicular directions.

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“…Merriam et al (2001) 15 in a study on horizontal and vertical meridians of the cornea after manual SICS concluded that with 6 mm superior scleral tunnel incision the corneal meridians stabilized at average 1.2 months.…”

Section: Discussionmentioning

confidence: 99%

A Comparative Study of Surgically Induced Astigmatism in Straight, Frown and Modified Chevron Incisions in Manual Small Incision Cataract Surgery

Solanki¹,

Anand²

2015

jemds

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PURPOSE:To compare the surgically induced astigmatism following straight, frown and modified chevron incisions in MSICS. METHOD: This is a Prospective interventional study conducted in RIO Bhopal during academic session of April 2009 to October 2010 in which 145 eyes of 137 patients were evaluated. Patients with relatively soft nuclei and healthy cornea, adequate anterior chamber and those who could be called up for regular follow up were chosen for the study. Preoperative keratometry was done to determine K-reading in both horizontal and vertical meridians. Astigmatism was graded and classified according to Holmström's gradation 1 37.9% cases were given straight incision, 18.6% cases were given Frown incision. While in the remaining 43.4% cases Modified chevron was made. In majority of cases 71%, 6.5 mm incision was made while larger incision 7mm and 7.5mm were made in 23.4% and 5.5% cases respectively. Post-operative keratometry readings were taken at first post-operative day and at the end of 6 th week following surgery and surgically induced astigmatism was calculated. RESULTS: Post operatively frown incision group's average SIA was 0.68 D. Modified chevron incision group had 1.02 D SIA, Straight incision group had the maximum SIA of 1.15D. However the mean surgically induced astigmatism in all incision types in our study was found to have SIA=1.01 D. CONCLUSION: In our study we observed that Frown incision was the best of all incision types with regards to SIA. KEYWORDS: SIA, Modified chevron incision, straight incision, frown incision. INTRODUCTION:In the developing countries where cost 1 is a major issue, MSICS was developed after the advent of phacoemulsification, and hence it is a relatively younger technique than the latter. Innumerable variations in methodologies of MSICS as well as the utility of MSICS in the day to day practice invoke a great deal of discussion and debate. In MSICS which is based on the concept of scleral tunnel, everything about the wound has to be carefully planned depending on the type of technique, hardness of the nucleus, amount of preoperative astigmatism. 2,3 It has been unequivocally demonstrated that smaller the incision, 4,5 lesser the number of sutures 6,7 and valvular construction of wound would induce minimal corneal curvature change that is astigmatism. The parameters 8 important for the structural integrity of the tunnel are- The self-sealing property of the tunnel.  The location of the wound on the sclera with respect to the limbus, 7,9 and  The shape of the incision. 7,10 Cataract surgery has gone beyond just being a means to get the lens out of the eye. Postoperative astigmatism plays an important role in evaluation of final outcome of surgery. Astigmatic consideration hence forms an integral part of incisional considerations prior to surgery.

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The effect of incisions for cataract on corneal curvature

Cited by 46 publications

References 24 publications

Surgical and Visual Outcome of Phacoemulsification Surgery (Routine) and Micro - Phaco (Bimanual Phaco): A Comparative Study

Surgical and Visual Outcome of Phacoemulsification Surgery (Routine) and Micro - Phaco (Bimanual Phaco): A Comparative Study

Finite Element Model of Cornea Deformation

A Comparative Study of Surgically Induced Astigmatism in Straight, Frown and Modified Chevron Incisions in Manual Small Incision Cataract Surgery

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