Assessment of a software guided system to reduce pre-existing astigmatism in cataract surgery.

The aim of this pilot study was to assess the astigmatism after small incision cataract surgery by use of a novel software guided surgical technique. The software system guides the surgeon toward a hypothetical shape of the cornea. When this shape is achieved, the vertical meridian is relaxed and the incision does not produce any astigmatism. How that hypothetical shape is to be achieved by the surgeon is described. If preoperative astigmatism exists, the hypothetical shape calculated by the system takes that into account. This enables the surgeon to reduce preexisting astigmatism, without having to change the site or size of the standard 6 mm 12 o clock incision of SICS. Results: Results indicated that preoperative astigmatism reduced in 11 out of 14 cases at the end of 8 weeks, remained unchanged in one, and increased by less than 0.5D in two cases. This proves the hypothesis that the vertical corneal meridian is under higher tension and relaxing it by flattening the perpendicular meridian has a reducing effect on postoperative astigmatism.

[Assessment of astigmatism associated with the iris-fixated ARTISAN aphakia implant: Anterior fixation versus posterior fixation, study of postoperative follow-up at one year]. / Évaluation de l'astigmatisme associé à l'implant ARTISAN Aphakia fixé à l'iris en face antérieure versus face postérieure : étude du suivi postopératoire sur un an.

PURPOSE: The goal of our retrospective, single-center study of a case series was to compare the total, corneal, and internal astigmatism, and the visual acuity at one year after combined or stand-alone surgery consisting of iris fixation of an iris-claw intraocular lens (ARTISAN aphakia) in aphakic patients, according to whether the lens was fixated to the anterior (n=21) or posterior (n=51) surface of the iris. RESULTS: We did not find a significant difference between these two types of fixation for any of the studied variables. The surgically induced astigmatism was 1.67 D at 176° in group A versus 1.19 D at 11° in group P. CONCLUSION: Although this surgery creates additional corneal astigmatism, it has not been proven that it differs depending on the type of fixation of the iris-claw. If we adhere to the notion that the posterior fixated iris-claw decreases the risk of endothelial decompensation in case the implant becomes disenclavated, then reverse iris fixation of the iris-claw makes sense.

Development of a program for toric intraocular lens calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position.

BACKGROUND: To evaluate the toric intraocular lens (IOL) calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position (ELP). METHODS: Two thousand samples of corneal parameters with keratometric astigmatism ≥ 1.0 D were obtained using bootstrap methods. The probability distributions for incision-induced keratometric and posterior corneal astigmatisms, as well as ELP were estimated from the literature review. The predicted residual astigmatism error using method D with an IOL add power calculator (IAPC) was compared with those derived using methods A, B, and C through Monte-Carlo simulation. Method A considered the keratometric astigmatism and incision-induced keratometric astigmatism, method B considered posterior corneal astigmatism in addition to the A method, method C considered incision-induced posterior corneal astigmatism in addition to the B method, and method D considered ELP in addition to the C method. To verify the IAPC used in this study, the predicted toric IOL cylinder power and its axis using the IAPC were compared with ray-tracing simulation results. RESULTS: The median magnitude of the predicted residual astigmatism error using method D (0.25 diopters [D]) was smaller than that derived using methods A (0.42 D), B (0.38 D), and C (0.28 D) respectively. Linear regression analysis indicated that the predicted toric IOL cylinder power and its axis had excellent goodness-of-fit between the IAPC and ray-tracing simulation. CONCLUSIONS: The IAPC is a simple but accurate method for predicting the toric IOL cylinder power and its axis considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and ELP.

Assessment of Anterior, Posterior, and Total Central Corneal Astigmatism in Eyes With Keratoconus.

PURPOSE: To investigate the magnitudes and the axis orientations of anterior, posterior, and total central corneal astigmatism in eyes with keratoconus. DESIGN: Retrospective case series. METHODS: This study comprised 137 eyes of 137 keratoconic patients (97 men and 40 women; mean age ± standard deviation, 36.9 ± 12.2 years). The magnitude and the axis orientation of each corneal astigmatism were determined with a rotating Scheimpflug system. RESULTS: The mean magnitudes of anterior, posterior, and total central corneal astigmatism were 3.93 ± 2.74 diopters (D), 0.93 ± 0.64 D, and 3.90 ± 2.75 D, respectively. With-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism of the anterior corneal surface was found in 90 eyes (65.7%), 33 eyes (24.1%), and 14 eyes (10.2%), respectively, whereas the corresponding astigmatism of the posterior corneal surface was found in 14 eyes (10.2%), 15 eyes (10.9%), and 108 eyes (78.8%), respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r = 0.769, P < .001). CONCLUSIONS: The mean magnitudes of anterior and posterior corneal astigmatism were approximately 4 D and 1 D, respectively, in eyes with keratoconus. Approximately 65% and 80% of eyes showed that WTR anterior astigmatism and ATR posterior astigmatism, respectively. The presence of posterior corneal astigmatism is not necessarily negligible for the accurate astigmatic correction of toric intraocular lens implantation or rigid gas-permeable contact lens wear for keratoconus.

Surgically induced astigmatism assessment: comparison between three corneal measuring devices.

PURPOSE: To compare the findings of three corneal measuring devices for calculating surgically induced astigmatism (SIA) during cataract extraction. METHODS: Patients' records were retrospectively reviewed to identify patients who had corneal astigmatism measurements before and at least 1 month after cataract surgery through 2.4-mm corneal incisions by all three tested devices (Lenstar LS900, Haag-Streit, Koeniz, Switzerland; IOLMaster 500, Carl Zeiss Meditec, Dublin, CA; and Atlas topographer, Carl Zeiss Meditec). Vector analysis was used to calculate the SIA for each measuring device. RESULTS: Seventy eyes of 49 patients were included. All three measuring devices had similar SIA results: the median SIAs were 0.45 diopters (D) for the Lenstar, 0.41 D for the IOLMaster, and 0.47 D for the Atlas topographer (P = .884). CONCLUSIONS: The three evaluated anterior corneal measuring devices produced similar results in measuring SIA. [J Refract Surg. 2015;31(4):244-247.].

Microcoaxial torsional cataract surgery 1.8 mm versus 2.2 mm: functional and morphological assessment.

BACKGROUND AND OBJECTIVE: To compare functional and morphological outcomes of 1.8-mm versus 2.2-mm microincision coaxial cataract surgery (MCCS). PATIENTS AND METHODS: Thirty eyes of 30 patients that underwent MCCS were randomized to two groups: 1.8-mm MCCS (group 1: 15 eyes) and 2.2-mm MCCS (group 2: 15 eyes). RESULTS: There were no significant between-group differences in uncorrected visual acuity, best-corrected visual acuity, keratometric astigmatism, and endothelial cell count. One day postoperatively, a greater increase of corneal thickness at the incision site was observed in group 1 compared to group 2 using anterior segment optical coherence tomography with no significant differences in tunnel morphometric features and confocal microscopy showed more tunnel edema in group 1 versus group 2 that resolved in both groups. CONCLUSION: Both 1.8- and 2.2-mm torsional MCCS were safe and efficient with easy surgical maneuvers and excellent functional and morphological results; 1.8-mm MCCS induced slightly greater tunnel edema shortly after surgery that resolved in the medium term.

Ophthalmic assessment of children with down syndrome: is England doing its bit?

INTRODUCTION: Patients with Down syndrome have characteristic features including ocular manifestations. Guidelines exist for ophthalmic surveillance of people with Down syndrome, but locally (North Staffordshire) there is no formal program in place. METHODS: Hospital records were used to detect children with Down syndrome. Data were extracted retrospectively to determine which children had been seen by ophthalmic services, the mode of assessment used, and the frequency of ophthalmic disorders. RESULTS: Of the 96 children with Down syndrome, 38% received no ophthalmic assessment. Of those seen, the mean age at first appointment was nearly 3 years, with a number of children being more than 5 years old. Most children (96%) had at least one ophthalmic abnormality, the commonest being hyperopia. Requested follow-up was routinely exceeded by almost a year with 19% of children receiving no follow-up. DISCUSSION: Ocular disorders are common in the two thirds of children who are currently seen by ophthalmic services. Locally, we are falling short of the targets set by the 2006 recommendations for basic medical care of people with Down syndrome. A screening program might have a beneficial impact on the vision of children with Down syndrome.

Monte Carlo simulation of expected outcomes with the AcrySof toric intraocular lens.

BACKGROUND: To use a Monte Carlo simulation to predict postoperative results with the AcrySof Toric lens, evaluating the likelihood of over- or under-correction using various toric lens selection criteria. METHODS: Keratometric data were obtained from a large patient population with preoperative corneal astigmatism <= 2.50D (2,000 eyes). The probability distributions for toric marking accuracy, surgically induced astigmatism and lens rotation were estimated using available data. Anticipated residual astigmatism was calculated using a Monte Carlo simulation under two different lens selection scenarios. RESULTS: This simulation demonstrated that random errors in alignment, surgically induced astigmatism and lens rotation slightly reduced the overall effect of the toric lens. Residual astigmatism was statistically significantly higher under the simulation of surgery relative to an exact calculation (p < 0.05). The simulation also demonstrated that more aggressive lens selection criteria could produce clinically significant reductions in residual astigmatism in a high percentage of patients. CONCLUSION: Monte Carlo simulation suggests that surgical variability and lens orientation/rotation variability may combine to produce small reductions in the correction achieved with the AcrySof Toric IOL. Adopting more aggressive lens selection criteria may yield significantly lower residual astigmatism values for many patients, with negligible overcorrections. Surgeons are encouraged to evaluate their AcrySof Toric outcomes to determine if they should modify their individual lens selection criteria, or their default surgically induced astigmatism value, to benefit their patients.

A preliminary in vivo assessment of higher-order aberrations induced by a silicone hydrogel monofocal contact lens.

PURPOSE: To evaluate the effect of negatively powered soft contact lenses on ocular higher-order aberrations (HOAs). METHODS: HOA measurements were performed with fixed optical zones of 4.0 and 6.0 mm on 20 eyes of 10 participants before and minutes after wearing extended-wear Focus NIGHT & DAY contact lenses. For each eye, three contact lens powers were used: -2.00 diopters (D), -4.00 D, and a power equal to the spherical equivalent of each eye. RESULTS: The change in spherical aberration was highly correlated with the change in negative power of the contact lens at an optical zone of 4 and 6 mm (Pearson correlation coefficient=0.914 and 0.743, respectively, P<0.0001). Total HOAs had a weaker but important correlation at an optical zone of 6 mm (Pearson correlation coefficient=0.470, P=0.037) and insignificant correlation at an optical zone of 4 mm. Coma and trefoil were poorly correlated with contact lens power in either optical zone. Compared to the control using both optical zones, the -2.00 D contact lens resulted in a significant increase in total HOAs and spherical aberration, whereas the -6.00 D lens yielded a marked decrease in spherical aberration and a mild, statistically insignificant increase in total HOAs. Both contact lens powers yielded larger ocular coma and unchanged trefoil levels. The change from induction to reduction of spherical aberration occurred at -4.00 D. CONCLUSIONS: The Focus NIGHT & DAY lens vehicle harbors positive spherical aberration and coma, independently of the lens power. The negative power of contact lenses induces negative spherical aberration, which, at large values, compensates for the lens vehicle positive spherical aberration to produce a net negative spherical aberration.

Outcome of penetrating keratoplasty performed by cornea fellows compared with that of an experienced staff surgeon.

PURPOSE: To compare the outcome of penetrating keratoplasty performed by supervised cornea fellows and an experienced staff surgeon. METHODS: Retrospective review of cases of penetrating keratoplasty performed over a 4-year period with corneal topography performed on a clear graft. Overall, 202 cases from 184 patients were included: 108 performed by an experienced staff surgeon and 94 cases by 9 cornea fellows. Charts were reviewed for topographic astigmatism, other topographic indices, refractive astigmatism and best-corrected visual acuity (BCVA), all recorded after removal of the 10-0 sutures while the 11-0 suture remained in place. Graft clarity was assessed at final follow-up. RESULTS: Mean postoperative topographic astigmatism was 4.60 +/- 2.7 diopters in the fellow group and 4.08 +/- 2.41 diopters in the staff group. The mean postoperative time at which corneal topography was obtained was 9.53 +/- 4.4 months in the fellow group and 9.22 +/- 4.6 months in the staff group. Mean refractive astigmatism was 3.77 +/- 1.97 diopters (fellows) and 3.49 +/- 1.93 diopters (staff). Mean surface asymmetry index (SAI) was 1.89 +/- 1.42 (fellows) and 1.61 +/- 1.08 (staff). Mean surface regularity index (SRI) was 1.43 +/- 0.72 (fellows) and 1.45 +/- 0.61 (staff). Mean BCVA was 0.49 logMAR (20/61) +/- 4.3 lines (fellows) and 0.47 logMAR (20/59) +/- 3.9 lines (staff). In the fellow group, 85 (90%) cases remained clear over a mean follow-up of 32 months and in the staff group 100 (93%) grafts remained clear over a mean follow-up of 38 months. Simple and multiple regression analyses indicated no difference between the 2 groups in all outcome measures. CONCLUSIONS: Properly supervised cornea fellows in training achieved favorable penetrating keratoplasty results that were comparable to those of an experienced staff surgeon.

Sutureless cataract surgery with nucleus extraction: outcome of a prospective study in Nepal.

AIM: To report the short and medium term outcome of a prospective series of sutureless manual extracapsular cataract extractions (ECCE) at a high volume surgical centre in Nepal. METHODS: Cataract surgery was carried out, on eyes with no co-existing diseases, in 500 consecutive patients who were likely to return for follow up. The technique involved sclerocorneal tunnel, capsulotomy, hydrodissection, nucleus extraction with a bent needle tip hook, and posterior chamber intraocular lens (PC-IOL) implantation according to biometry findings. Surgical complications, visual acuity at discharge, 6 weeks, and 1 year follow up, and surgically induced astigmatism are reported. RESULTS: The uncorrected visual acuity at discharge was 6/18 or better in 76.8% of eyes, and declined to 70.5% at 6 weeks' follow up, and 64.9% at 1 year. The best corrected visual acuity was 6/18 or better in 96.2% of eyes at 6 weeks and in 95.9% at 1 year. Poor visual outcome (<6/60) occurred in less than 2%. Intraoperative complications included 47 (9.4%) eyes with hyphaema, and one eye (0.2%) with posterior capsule rupture and vitreous in the anterior chamber. Surgery led to an increase in against the rule astigmatism, which was the major cause of uncorrected visual acuity less than 6/18. Six weeks postoperatively, 85.5% of eyes had against the rule astigmatism, with a mean induced cylinder of 1.41 D (SD 0.8). There was a further small increase in against the rule astigmatism of 0.66 D (SD 0.41) between 6 weeks and 1 year. The mean duration of surgery was 4 minutes and the average cost of consumables, including the IOL, was less than $10. CONCLUSION: Rapid recovery of good vision can be achieved with sutureless manual ECCE at low cost in areas where there is a need for high volume cataract surgery. Further work is required to reduce significant postoperative astigmatism, which was the major cause of uncorrected acuity less than 6/18.

Extracapsular cataract extraction compared with small incision surgery by phacoemulsification: a randomised trial.

BACKGROUND: Cataract extraction constitutes the largest surgical workload in ophthalmic units throughout the world. Extracapsular cataract extraction (ECCE), through a large incision, with insertion of an intraocular lens has been the most widely used method from 1982 until recently. Technological advances have led to the increasing use of phacoemulsification (Phako) to emulsify and remove the lens The technique requires a smaller incision, but requires substantial capital investment in theatre equipment. In this randomised trial we assessed the clinical outcomes and carried out an economic evaluation of the two procedures. METHODS: In this two centre randomised trial, 232 patients with age related cataract received ECCE, and 244 received small incision surgery by Phako. The main comparative outcomes were visual acuity, refraction, and complication rates. Resource use was monitored in the two trial centres and in an independent comparator centre. Costs calculated included average cost per procedure, at each stage of follow up. RESULTS: Phako was found to be clinically superior. Surgical complications and capsule opacity within 1 year after surgery were significantly less frequent, and a higher proportion achieved an unaided visual acuity of 6/9 or better (<0.2 logMAR) in the Phako group. Postoperative astigmatism was more stable in Phako. The average cost of a cataract operation and postoperative care within the trial was similar for the two procedures. With the input of additional spectacles for corrected vision at 6 months after surgery, the average cost per procedure was pound359.89 for Phako and pound367.57 for ECCE. CONCLUSION: Phako is clinically superior to ECCE and is cost effective.

Topographic assessment of irregular astigmatism after photorefractive keratectomy.

OBJECTIVE: To correlate new quantitative topographic indexes of corneal irregular astigmatism to best spectacle-corrected visual acuity (BSCVA) following excimer laser photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, LSU Eye Center, and Refractive Surgery Center of the South, Ear, Nose & Throat Hospital, New Orleans, Louisiana; Manhattan Eye, Ear and Throat Hospital, New York, New York, USA. METHODS: Videokeratography data (TMS-1) were obtained preoperatively and 1, 3, 6, 12, 18, and 24 months postoperatively from 100 eyes having PRK for low to mild myopia. Algorithms measured fine local irregularity with the surface regularity index (SRIp), varifocality with the coefficient of variation of corneal power (CVPp), and central islands with the elevation/depression magnitude (EDM). RESULTS: The SRIp and CVPp increased after surgery and remained significantly higher than the preoperative levels throughout the 24 month follow-up (P < .05). The increase in EDM was significant from 1 to 6 months (P < .05) but not thereafter. Multiple regression analysis revealed that variables having a statistically significant relationship with postoperative BSCVA were CVPp and EDM at 1 month, CVPp at 3 months, and CVPp, haze, and age at 6 months. No statistically significant correlation between any measures of irregular astigmatism and BSCVA was found after 1 year of follow-up. CONCLUSION: The quantitative measures used in this study are sensitive methods by which irregular astigmatism after keratorefractive procedures can be classified, evaluated, and compared.

Clinical assessment of a hand-held automated keratometer in cataract surgery.

PURPOSE: Pre-operative keratometry was performed on 32 eyes of 32 patients undergoing extracapsular cataract extraction with intraocular lens implantation, for calculation of intraocular lens power. In an additional 20 eyes of 20 patients post-operative keratometry was performed to guide selective suture removal. Readings from a manual keratometer and an automated hand-held keratometer were compared. METHODS: Pre-operative measurements were repeated three times on each subject to assess the repeatability of each machine. Mean-difference plots were performed to define the limits of agreement of the two machines. RESULTS: Repeatability was higher using manual keratometry (MK) than automated keratometry (AK). There was broad agreement between the two machines in pre-operative and post-operative assessment, although clinically significant differences are likely to occur in some cases. CONCLUSIONS: MK should continue to be used for routine pre-operative keratometry, with the AK providing a useful alternative when MK is not possible. AK is sufficiently accurate to allow its use in post-operative assessment of suture-induced astigmatism.