Merits of conjunctival frill incision in reducing trabeculectomy-induced astigmatism and patient discomfort

Purpose

To compare results of a novel "conjunctival frill/smile incision" on surgically induced astigmatism (SIA) and patient discomfort vs conventional trabeculectomy in the initial postoperative period.

Methods

Sixty trabeculectomy cases were subjected to either conjunctival frill incision, performed 1.5-2.0 mm from the limbus (study group) or conventional fornix-based conjunctival flap (control group). Corneal astigmatism and suture-induced discomfort were assessed by keratometry and a self-devised patient questionnaire, respectively.

Results

Both groups generated a "with the rule" SIA, which was 1.77 vs 2.42 at 1 week and reduced to 1.27 vs 1.8 in the study vs control group, after removal of sutures - both scleral flap releasable and conjunctival at 1 month. Patient discomfort score revealed enhanced comfort in 37% of patients (study group) vs 17% (control group) during the early postoperative period. After 1 month of surgery, good comfort was regained in all cases.

Conclusion

This novel suturing technique results in reduced SIA, patient discomfort during the 1st month after trabeculectomy.

The Zeiss surgical keratometer in cataract surgery

The Zeiss keratometer is easy to use with simple and fast reading. The preoperative keratometry principle is satisfactory by allowing theorically a better control of surgical factors of postoperative astigmatism after cataract surgery. Its major interest appears in surgical training, when one wants to compensate a preoperative astigmatism or when one wishes to avoid secondary suture removal. However, its interest is very variable according to surgical experience.

A new approach based on Machine Learning for predicting corneal curvature (K1) and astigmatism in patients with keratoconus after intracorneal ring implantation

Keratoconus (KC) is the most common type of corneal ectasia. A corneal transplantation was the treatment of choice until the last decade. However, intra-corneal ring implantation has become more and more common, and it is commonly used to treat KC thus avoiding a corneal transplantation. This work proposes a new approach based on Machine Learning to predict the vision gain of KC patients after ring implantation. That vision gain is assessed by means of the corneal curvature and the astigmatism. Different models were proposed; the best results were achieved by an artificial neural network based on the Multilayer Perceptron. The error provided by the best model was 0.97D of corneal curvature and 0.93D of astigmatism.

Keratometric astigmatism evaluation after trabeculectomy

INTRODUCTION

Post-operative astigmatism is one of the most important causes for diminution of vision after trabeculectomy.

OBJECTIVE

To evaluate the induced corneal astigmatism following trabeculectomy with the use of 8-0 silk suture.

MATERIALS AND METHODS

A prospective interventional study was done including 100 consecutive eyes of 84 patients who underwent trabeculectomy with the use of 8-0 silk suture. The postoperative induced astigmatism on the 1st post-operative day, 3rd week and after 6 months was determined.

STATISTICS

Vector analysis was performed on the data using a computerized method for calculating the surgically induced astigmatism (SIA) for each eye at every time point postoperatively. In order to analyze group changes, we also performed vector decomposition which gave us a mathematical expression of the changes in astigmatism "with the rule" (WTR) or "against the rule" (ATR).

RESULTS

The mean age of all the patients was 53.31 11.39 years. The mean 1st post-operative surgically induced astigmatism (SIA) was 2.73 D ( 99 degree ) which reduced to 0.41 D ( 58 degree) at the 3rd week and 0.43 ( 21 degree) at 6 months. The mean WTR astigmatism was 4.46 D and ART astigmatism was 1.42 D on the 1st post-operative day which was significantly high ( p less than 0.0001). At the 3rd week and 6 months WTR astigmatism ( 1.40 D and 1.08D ) and ATR astigmatism (1.27 D and 1.10 D) showed no significant changes (p=0.69,0.97 respectively.

CONCLUSION

Trabeculectomy with the use of 8/0 silk sutures showed significantly high 1st post-operative day SIA which nevertheless perished fast to a minimum amount at just 3 weeks.

Analyses of surgically induced astigmatism and axis deviation in microcoaxial phacoemulsification

To evaluate surgically induced astigmatism (SIA) and axis deviation after coaxial microincision superotemporal clear corneal phacoemulsification incision in eyes with differently located steep axis. This prospective, comparative study included four groups of 45 eyes with age-related cataracts; each group underwent 2.2-mm superotemporal clear corneal incision (CCI) cataract surgery. The four groups of patients were divided by location of the steep axis. Groups were matched according to symmetry of the steep axis for both right and left eyes as follows--0°-45° of steep axis for right eyes, and 136°-180° for left eyes (group 1); 46°-90° for right eyes and 91°-135° for left eyes (group 2); 91°-135° for right eyes and 46°-90° for left eyes (group 3); and 136°-180° for right eyes and 0°-45° for left eyes (group 4). Outcome measures included changes in mean total astigmatism, SIA, and axis deviation. Astigmatism was measured by manual keratometry readings before surgery and week 1, week 4, week 8, and week 12 postoperatively. SIA was calculated by the vector analysis (Holladay-Cravy-Koch method). The magnitude of mean total astigmatism was lowest in group 3 and highest in group 1 at week 12. SIA was 0.39 diopters (D), 0.22 D, 0.17 D, and 0.28 D in group 1, group 2, group 3, and group 4, respectively. The change in astigmatic axis deviation was highest in group 3 (23.6 ± 16.6) (P < 0.05). Axis deviation and SIA were stable after week 4. Planning of CCI on or near the steep axis can help decrease corneal astigmatism.

Clinical evaluation of three incision size-dependent phacoemulsification systems

PURPOSE

To compare the outcomes of cataract surgery performed with 3 incision size-dependent phacoemulsification groups (1.8, 2.2, and 3.0 mm).

DESIGN

Prospective randomized comparative study.

METHODS

One hundred twenty eyes of 120 patients with age-related cataract (grades 2 to 4) were categorized according to the Lens Opacities Classification System III. Eligible subjects were randomly assigned to 3 surgical groups using coaxial phacoemulsification through 3 clear corneal incision sizes (1.8, 2.2, and 3.0 mm). Different intraoperative and postoperative outcome measures were obtained, with corneal incision size and surgically induced astigmatism as the main clinical outcomes.

RESULTS

There were no statistically significant differences in most of the intraoperative and postoperative outcome measures among the 3 groups. However, the mean cord length of the clear corneal incision was increased in each group after surgery. The mean maximal clear corneal incision thickness in the 1.8-mm group was significantly greater than for the other groups at 1 month. The mean surgically induced astigmatism in the 1.8- and 2.2-mm groups was significantly less than that in the 3.0-mm group after 1 month, without significant difference between the 1.8- and 2.2-mm groups.

CONCLUSIONS

With appropriate equipment, smaller incisions may result in less astigmatism, but the particular system used will influence incision stress and wound integrity, and may thus limit the reduction in incision size and astigmatism that is achievable.

[The impact of incisional dimensions on the surgically induced astigmatism]

PURPOSE

The study reveals the incision's dimension impact on the the values of the postoperative induced astigmatism after cataract phacoemulsification surgery.

METHOD

The study involved 648 patients who have suffered cataract surgery by phacoemulsification.

RESULTS

The postoperative induced astigmatism has lower values as the incision's dimension is lower The astigmatism takes place after cataracts with hard nucleus.

CONCLUSIONS

The microincisions used in cataract surgery allow the obtaining of lower values of the postoperative induced astigmatism. The nucleus's hardness has an influence over the values of the postoperative induced astigmatism.

Influence of suture regularity on corneal astigmatism after penetrating keratoplasty

PURPOSE

To investigate whether suture regularity affects corneal astigmatism after keratoplasty.

METHODS

Twenty-one patients undergoing penetrating keratoplasty for various corneal diseases were included in the study. The grafts were sutured in place using a single-running Nylon 10-0 suture, taking 24 bites. Immediately after surgery, standard calibrated images of the grafted eye were captured and stored. Using a dedicated image analysis programme, stitches and needle points were identified, and a number of suture regularity variables were calculated. Corneal topographic images were obtained before suture removal (12 months after surgery) and 3 months after suture removal (18 months after surgery). Topographic measures of astigmatism [surface regularity (SRI), surface asymmetry index (SAI) and simulated keratometric astigmatism] were calculated and correlated with the computed suture regularity variables.

RESULTS

The average stitch length was 3.04 ± 0.28 mm and the distance between the outer needle points was 2.53 ± 0.09 mm. The SRI was 1.26 ± 0.36 and the SAI was 1.59 ± 0.67 after 12 months; these decreased to 1.03 ± 0.48 and 0.92 ± 0.46 after 18 months, respectively. Corneal astigmatism was 6.38 ± 2.99 and 5.87 ± 3.13 dioptres after 12 and 18 months, respectively. Suture regularity did not affect SAI, SRI or corneal astigmatism significantly 12 months after surgery. Eighteen months after surgery (3 months after suture removal), the standard deviation on the original stitch length was found to significantly increase corneal astigmatism. In addition, the size of the counter-clockwise angle between stitch and graft radian was correlated significantly with a lower SRI.

CONCLUSION

The origin of corneal astigmatism after penetrating keratoplasty is multifaceted. Regular stitch length and stitch advancement on the surface appears to improve the optical quality of the graft after suture removal. Factors such as stitch depth, suture tension and variations in wound construction might also be important predictors of corneal astigmatism after penetrating keratoplasty.

Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement

PURPOSE

To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement.

METHODS

Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germany) both before and after surgery. Clear corneal incisions with one suture were used in the phacoemulsification surgery. The keratometric corneal SIA (KSIA) was derived using the anterior corneal surface measurement and the keratometric index (1.3375) while neglecting the posterior corneal surface measurement. The Pentacam-derived total corneal SIA (PSIA) was derived by vergence tracing and polar value analysis [KP(135) and KP(180)] of the measurements on both corneal surfaces.

RESULTS

The mean arithmetic estimation errors of the KSIA for the PSIA were 0.16 ± 0.32 (-0.52 to 1.14) D for the KP(135), and -0.02 ± 0.30 (-0.75 to 1.29) D for the KP(180). There was a significant difference between the KP(135) components of the KSIA and PSIA. Bivariate analysis revealed a statistically significant difference between the combined means of the KSIA and PSIA. Overall, 24% had either a KP(135) component of the KSIA that differed by > 0.50 D from that of the PSIA or a KP(180) component of the KSIA that differed by > 0.50 D from that of the PSIA. The blurring strength caused by neglecting the posterior corneal measurement was > 0.50 D in 24% of eyes.

CONCLUSION

Neglecting the posterior corneal surface measurement may lead to significant deviation in the corneal SIA estimation after phacoemulsification in a proportion of eyes.

Topography-guided conductive keratoplasty: treatment for advanced keratoconus

PURPOSE

To evaluate the use of topography-guided conductive keratoplasty in eyes with keratoconus.

DESIGN

Interventional case series.

METHODS

We examined 21 eyes in 21 patients with advanced keratoconus. Topography-guided conductive keratoplasty was performed with intraoperative monitoring of corneal astigmatism using a surgical keratometer. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal topography, manifest refraction, intraocular pressure (IOP), corneal endothelial cell counts, complications, and eventual outcomes were evaluated.

RESULTS

UCVA (logarithm of the minimal angle of resolution [logMAR]), which was 1.65 ± 0.49 preoperatively, improved to 1.04 ± 0.64 at 1 week (P < .001) and 1.12 ± 0.61 at 1 month after surgery (P < .001). BSCVA, which was 1.02 ± 0.56 preoperatively, improved to 0.76 ± 0.65 at 1 week (P = .026) and 0.76 ± 0.60 at 1 month after surgery (P = .003). Manifest refraction, which was -15.13 ± 6.66 diopters (D) before surgery, declined to -9.97 ± 6.71 D at 1 month after surgery (P = .002). Although corneal topography reverted to the preoperative pattern and UCVA and BSCVA also regressed toward preoperative values, 12 of 21 eyes were better able to tolerate and conduct normal daily activities using contact lenses. Five subjects have undergone or are considering corneal transplantation after unsatisfactory postoperative results. No serious perioperative complication was observed.

CONCLUSIONS

Topography-guided conductive keratoplasty may be effective in reshaping corneal configuration in eyes with keratoconus, without serious complications, and possibly contributed to avoiding or delaying corneal transplantation.

[Acrysof(®) toric intraocular lens implantation in cataract surgery]

AIM

To assess the medium term outcomes of Acrysof(®) toric intraocular lens implantation in 54 patients (54 eyes).

METHODS

Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), preoperative astigmatism, residual postoperative astigmatism, and global average and model-specific intraocular lens (IOL) rotation grade were analyzed.

RESULTS

At 2-months of follow-up,the mean UCVA was 0.83 (SD: 0.14) Snellen scale, with 73.9% of the patients ≥0.8, and 32.6% with 1.0. Mean BCVA achieved was 0.94 (SD: 0.10). Mean preoperatory astigmatism was -2.25 diopters (D) (SD: 0.78), and mean postoperative astigmatism was -0.32 D (SD: 0.56), with significant differences between both groups (p<0.001). Model-specific mean residual astigmatism was -0.1 D for T3, -0.27 D for T4 and -0.43 D for T5, without significant differences between the three models (p=0.483). Mean IOL-axis rotation grade was 3.87±3.25 degrees, with 91.6% of implanted lens within 10° of predicted axis.

DISCUSSION

T3, T4 and T5 Acrysof(®) Toric intraocular lenses can correct preoperative astigmatism with a high success rate in terms of UCVA, and residual postoperative astigmatism, with minimum IOL-rotation grade at 2 months follow-up period.

Surgical approaches to corneal wound healing

New approaches to improving corneal epithelial wound healing include stromal puncture and removal of abnormal basement membrane material by excimer laser ablation (phototherapeutic keratectomy). Non-healing corneal erosions and chemical burns may also benefit from laser excision of the damaged surface to permit more normal epithelial attachments. Reduction of postsurgical astigmatism may be facilitated by adjustable sutures after penetrating keratoplasty or by molding the cornea with the use of a rigid contact lens in the immediate postoperative period.

The effect of different suturing techniques on astigmatism after penetrating keratoplasty

The purpose of this study was to compare the effects on astigmatism after penetrating keratoplasty with three different suture techniques. In this prospective study, 38 eyes of 38 patients underwent penetrating keratoplasty with three suturing techniques: interrupted, single running, and double running. Topographic astigmatism was measured at 2, 6, 12, and 18 months after keratoplasty. During 18 months after surgery, the interrupted suture group had higher astigmatism than the double running suture group. There was no significant difference in the amounts of astigmatism during the first year after keratoplasty between the single running and the double running suture group. However, at 18 months after surgery, when all sutures were out, the double running suture group (3.60+/-1.58 diopters) showed significantly less astigmatism than the single running group (5.65+/-1.61 diopters). In conclusion, post-keratoplasty astigmatism was the least in the double running suture group of the three suturing techniques at 18 months after penetrating keratoplasty.

[Penetrating keratoplasty with intrastromal corneal ring. A prospective randomized study]

BACKGROUND

The purpose of the study was to evaluate the efficacy and safety of Krumeichs' intrastromal corneal ring following penetrating keratoplasty. Postoperative astigmatism and occurrence of complications were the main criteria of this study.

MATERIAL AND METHODS

A total of 20 patients were included in this prospectively randomized study (10 patients with and 10 patients without corneal ring). Follow-up examinations were performed 6 weeks, 4, 12, and 18 months postoperatively, including best corrected visual acuity and Orbscan corneal topography.

RESULTS

The mean follow-up time is currently 18.9+/-2.8 months. The mean astigmatism (Orbscan) is 3.9 D in the group with ring and 4.0 D in the group without a ring. Spontaneous suture rupture occurred in five patients with corneal ring.

CONCLUSIONS

The use of the intrastromal corneal ring following penetrating keratoplasty caused no reduction of postoperative astigmatism. The reason for the spontaneous suture ruptures is unclear.

Corneal Topography-Guided Penetrating Keratoplasty and Suture Adjustment

PURPOSE

To describe a new keratoplasty procedure using intraoperative topography to reduce postoperative astigmatism.

METHODS

One hundred sixty-five eyes of 150 consecutive patients were enrolled in this prospective study. The most common diagnosis was keratoconus (78.8%). As many as 5.5% had post-laser in situ keratomileusis ectasia. Keratoplasty was performed with the Hanna Corneal Trephine System. A 24-bite running suture was placed, using a specially developed marker. Suture adjustment was performed with the aid of an intraoperative topographer (Keratron Scout; OPTIKON 2000, Rome, Italy). The aim of the adjustment was to obtain an astigmatism < or =2.0 D on the operating table. In case of >3.0 D of astigmatism at 1 month after surgery, suture adjustment was performed using the same intraoperative topographer.

RESULTS

At 12 months postoperatevely (suture in), data from 108 (64%) eyes were available. The mean refractive astigmatism was 3.53 D, and the mean topographical astigmatism was 4.7 D. At 18 months (suture out), data from 32 eyes (19.4%) were available, and at 24 months, data from 29 eyes (13.3%) were available. The mean refractive astigmatism was 3.39 D at 18 months and 3.47 D at 24 months. The mean topographic astigmatism was 2.30 D at 18 months and 1.76 D at 24 months. Mean best spectacle-corrected visual acuity (BSCVA) was 0.51 at 3 months, 0.63 at 12 months (suture in), 0.67 at 18 months (suture out), and 0.78 at 24 months postoperatively.

CONCLUSIONS

The combination of intraoperative topography and a 24-bite single running suture resulted in a stable astigmatism throughout the follow-up period, even after suture removal. BSCVA reached a 20/40 level as early as 3 months postoperatively and continued to rise after suture removal. The stability of astigmatism and BSCVA shortened the postoperative visual rehabilitation time and provided a high quality of vision early in the postoperative period.

A new technique to mark the donor and host corneas in keratoplasty

A new technique is described to easily and accurately mark the donor and the host cornea in keratoplasty using simple, readily available instruments and utilizing a simple mathematical equation. This technique will allow for even distribution of the donor tissue in the recipient bed.

Active Eye-tracking Improves LASIK Results

PURPOSE

To study the advantage of active eye-tracking for photorefractive surgery.

METHODS

In a prospective, double-masked study, LASIK for myopia and myopic astigmatism was performed in 50 patients using the ALLEGRETTO WAVE version 1007. All patients received LASIK with full comprehension of the importance of fixation during the procedure. All surgical procedures were performed by a single surgeon. The eye-tracker was turned off in one group (n = 25) and kept on in another group (n = 25). Preoperatively and 3 months postoperatively, patients underwent a standard ophthalmic examination, which included comeal topography.

RESULTS

In the patients treated with the eye-tracker off, all had uncorrected visual acuity (UCVA) of > or = 20/40 and 64% had > or = 20/20. Compared with the patients treated with the eye-tracker on, they had higher residual cylindrical astigmatism (P < .05). Those treated with the eye-tracker on achieved better UCVA and best spectacle-corrected visual acuity (P < .05). Spherical error and potential visual acuity (TMS-II) were not significantly different between the groups.

CONCLUSIONS

The flying-spot system can achieve a fair result without active eye-tracking, but active eye-tracking helps improve the visual outcome and reduces postoperative cylindrical astigmatism.

Acuité visuelle un et deux ans après kératoplastie transfixiante pour kératocône

PURPOSE

To quantify the visual outcome obtained in patients operated on for penetrating keratoplasty for keratoconus (KC) after 1 and 2 years.

PATIENTS

and methods: The files from consecutive keratoconus patients operated on for PKP after more than 2 years of follow-up were retrospectively studied. The demographic charts, the KC stage, and the surgical features were noted. The best corrected visual acuities (BSCVA) were analyzed at the initial examination and after 1 and 2 years of follow-up.

RESULTS

One hundred and two eyes from 98 patients were analyzed, including 83 grade 4 (81%) and 19 grade 3 (18%) cases of KC. The mean preoperative BSCVA was 0.08 on the decimal chart, which increased to 0.5 and 0.6 1 and 2 years after penetrating keratoplasty (p<0.001, respectively). The mean keratometric astigmatism was 3.80+/-2.9 D and 3.94+/-2.3 D for the grade 3 and 4 KC, respectively, after 1 year and 2.52+/-1.9 D and 3.34+/-2.2 D after 2 years (NS). At this time point, 81% of the eyes had less than 5 D astigmatism.

CONCLUSION

One and 2 years after penetrating keratoplasty, a mean BSCVA of 0.5 and 0.6 could reasonably be expected in keratoconus patients and three-quarters of patients can be expected to see better than 0.5 after 2 years.

Optimizing higher-order aberrations with intraocular lens technology

PURPOSE OF REVIEW

Aspheric intraocular lens technology has been implemented during the past 5 years, and more and more intraocular lenses with different amounts of asphericity are becoming available. Despite the efficacy in the correction of spherical aberration and the good results on implanted eyes, the theoretical advantages of aspheric intraocular lenses are still controversial.

RECENT FINDINGS

All investigations showed the ability of the aspheric intraocular lenses to correct the positive spherical aberration of the cornea, with variable impact on the total eye wavefront but with constant advantages in the optical quality of the eyes as measured by the Modulation Transfer Function, the Point Spread Function, and the contrast sensitivity of implanted patients. Theoretical studies on model eyes underlined some possible limitations of aspheric intraocular lenses, especially sensitivity to decentration. In addition, the actual optical quality in implanted eyes is also affected by light scattering, a parameter missed by simple aberration analysis.

SUMMARY

Aspheric intraocular lenses effectively reduce spherical aberration in implanted eyes, with improvement in optical quality over the parent spherical intraocular lens. The advantages for implanted eyes could be limited by decentration, by small pupil diameter, and by reduced media transparency.

Science and Strategy for Preventing and Managing Corneal Ulceration

ABSTRACT Corneal ulcers can cause significant loss of vision from scarring and astigmatism, but rapid management can limit the destruction and improve outcomes. Infectious ulcers usually resolve with antimicrobial treatment. Noninfectious ulcers, however, present a diagnostic and therapeutic challenge. They can often be resolved by eliminating toxic medications and providing surface support with lubrication and collagenase inhibitors, but resistant ulcers may need more aggressive therapy with bandage contact lenses, tarsorrhaphy, or autologous serum. Ulcers impending perforation require urgent surgical management (e.g., tissue glue, conjunctival flaps, or keratoplasty). Topical steroids are useful when the ulceration is secondary to inflammatory mediators, but they are contraindicated in corneal melts with minimal inflammation, such as those associated with Sjogren syndrome. Systemic immunomodulation is required in addition to topical therapy in the presence of autoimmune disease. Understanding of the pathological processes that occur in different types of corneal ulcers is essential to formulation of a logical and effective treatment plan. Newer, more targeted treatment modalities may offer treatment options that have greater efficacy and fewer adverse effects.

Topography-guided CATz Versus Conventional LASIK for Myopia With the NIDEK EC-5000: A Bilateral Eye Study

PURPOSE

To evaluate the difference in visual acuity, subjective night vision glare, and higher order aberrations in eyes with myopia with or without astigmatism operated with topography-guided customized corneal LASIK and conventional LASIK.

METHODS

This contralateral study includes 46 eyes (23 patients) that underwent topography-guided corneal customized LASIK using the customized aspheric treatment zone (CATz) ablation profile in one eye and conventional LASIK using the NIDEK EC-5000 Advanced Vision Excimer laser system (NAVEX) in the other eye for myopia with or without astigmatism. Patients were masked to which eye underwent topography-guided CATz or conventional LASIK. Postoperative glare and root-mean-square (RMS) values for total higher order aberrations were measured at 1 and 3 months and compared between the two eyes.

RESULTS

No significant difference was noted in uncorrected visual acuity between the two groups at 1 and 3 months postoperatively. Of all patients, 81% stated glare was higher in conventionally treated eyes than in the CATz-treated eyes at 1 and 3 months postoperatively. The RMS values for total coma (0.2385 vs 0.1522) and spherical aberration (0.2381 vs 0.1058) in conventionally treated and CATz-treated eyes were significantly higher in conventionally treated eyes (P=.029 and P=.004, respectively) at 3-month follow-up.

CONCLUSIONS

Topography-guided corneal customized LASIK with the CATz profile gave better night vision quality as compared to conventional LASIK with expanded treatment zone. Better night vision quality was associated with less induced spherical aberrations and coma postoperatively in the CATz treatment group.

Reduction in astigmatism in manual small incision cataract surgery through change of incision site

To compare the astigmatism induced by a superior, supero-temporal and temporal incision in manual small incision cataract surgery. Induced astigmatism was analysed by Cartesian coordinates based analysis, using Holladay's system. Mean astigmatism induced by surgery was 1.28 Dx2.9 degrees for superior incision, 0.20 Dx23.7 degrees for supero-temporal incision and 0.37 Dx90 degrees for temporal incision. The study found that induced astigmatism was lower in the temporal and superotemporal groups compared to that in the superior group.

[The penetrating keratoplasty. A 100-year success story]

Ten precautions for prophylaxis of astigmatism in penetrating keratoplasty are recommended:1. The attempt should be made to determine donor topography for exclusion of previous refractive surgery, keratoconus/high astigmatism, and to allow for "harmonization" of donor and recipient topography.2. Donor and recipient trephination should be performed from the epithelial side with the same system, which is the prerequisite for congruent cut surfaces and angles in donor and recipient. For this purpose an artificial anterior chamber is used for donor trephination.3. Orientation structures in donor and host facilitate the correct placement of the first four or eight cardinal sutures to avoid horizontal torsion.4.A measurable improvement seems to be possible, using the Krumeich guided trephine system (GTS), the second generation Hanna trephine, and the Erlangen technique of nonmechanical trephination with the excimer laser.5. Horizontal positioning of the head and limbal plane are indispensable for state-of-the-art PKP surgery in order to avoid decentration, vertical tilt, and horizontal torsion.6. Graft size should be adjusted individually ("as large as possible, as small as necessary").7. Limbal centration should be preferred over pupil centration (especially in keratoconus).8. Excessive graft over- or undersize should be avoided to prevent stretching or compression of peripheral donor tissue.9. As long as Bowman's layer is intact a double running cross-stitch suture (according to Hoffmann) is preferred since it results in higher topographic regularity, earlier visual rehabilitation, and less suture loosening requiring only rarely suture replacement.10.Intraoperative keratoscopy should be applied after removal of lid specula and fixation sutures.

Modified Microkeratome-Assisted Posterior Lamellar Keratoplasty Using a Tissue Adhesive

OBJECTIVE

To compare graft stability and astigmatic change using suture vs tissue adhesive in an experimental model of microkeratome-assisted posterior lamellar keratoplasty.

METHODS

A 300-microm-thick partial flap keratectomy was performed in human donor corneoscleral rims using an artificial anterior chamber and a manual microkeratome. The flap stopped at the left central opening border, providing a wide hinge to add stability. After flap reflection, a 6.25-mm trephination was performed to obtain a disc of posterior stroma, Descemet membrane, and endothelium. The disc was positioned in a sutureless fashion, and the flap secured with either 5 interrupted sutures or a chondroitin-sulfate-aldehyde-based adhesive. Increasing intrachamber pressures were created to detect graft stability. Videokeratographic data were recorded to evaluate astigmatic change.

RESULTS

The mean (SD) astigmatic change was 3.08 (0.84) diopters (D) in the sutured group and 1.13 (0.55) D in the glued group (P = .008). Mean (SD) resisted pressures were 95.68 (27.38) mm Hg and 82.45 (18.40) mm Hg in the sutured and glued groups, respectively (P = .97).

CONCLUSION

This modified technique of microkeratome-assisted posterior lamellar keratoplasty showed excellent graft stability in both groups. Flaps sealed with the novel tissue adhesive had reduced astigmatic changes in our experimental model.

CLINICAL RELEVANCE

Sutureless microkeratome-assisted posterior lamellar keratoplasty using tissue adhesive may become a new alternative in the surgical treatment of corneal endothelial disorders.

Advances in microincision cataract surgery intraocular lenses

PURPOSE OF REVIEW

This review provides an update of recent advances in understanding the quality and functional significance of contrast sensitivity for the clinician regarding cataract, intraocular lenses and refractive surgery that goes beyond the measurement of visual acuity.

RECENT FINDINGS

New American National Standards Institute standards for contrast sensitivity based on linear sine-wave gratings are discussed that promise rapid advances of understanding and quantifying visual quality and function by unifying clinical results reported using contrast sensitivity. Increased sensitivity of linear sine-wave gratings over proposed bull's-eye radial gratings is discussed. Digital-image-processing software uses contrast sensitivity data to process images to help understand the quality of what the patient sees. Contrast sensitivity measurement is compared with wavefront aberrometry. Contrast sensitivity measures the total visual system quality in terms of contrast, whereas wavefront aberrometry measures the optical quality in terms of spatial distortion. Both measurements are needed to more fully understand the quality of vision.

SUMMARY

Recent advances provide the clinician with an awareness of why the new contrast-sensitivity standards are based on linear sine-wave gratings and how image-processing software can be used to better understand the quality of functional vision of the patient.

Comparison of surgically induced astigmatism of temporal versus superior clear corneal incisions

PURPOSE

Comparison of the astigmatism induced by the operation based on the 2.8 mm incisions in the clear cornea, performed by temporal approach and superior approach.

MATERIAL AND METHODS

Retrospective analysis was performed on the group of 65 patients (41 women and 24 men), mean age 74.5 +/- 7.1 years old. We studied a series of 70 eyes (32 right eyes and 38 left eyes). All of the patients underwent cataract surgery by means of ultrasonic phacoemulsification conducted at the Department of Ophthalmology, Military Health Services Institute in Warsaw, Poland within 2004-2005. Follow-up examinations took place 6 months after operation. There were DBCVA. NBCVA, intraocular pressure, anterior segment of the eye and fundus examined. Curvature of the cornea was measured by means of Javal's ophthalmometry. The results were assumed as significant in view of corneal curvature stabilization. Vector analysis of astigmatism was performed on the basis of method described by Jaffe. There was preoperative astigmatism vector (K1) and post-operative astigmatism vector (K3) calculated, as well as surgically inducted astigmatism (SIA)--vector (K2). From the group of 70 eyes, 19 were excluded from the study, where vector K1 was > 1.0 D as well as four eyes, where the main opening site depended on the size and axis of K1 vector. The group of 47 eyes was divided according to the opening site into two subgroups--group I (temporal approach--2.8 mm)--25 eyes and group II (superior approach 2.8 mm)--22 eyes. Statistical analysis was performed based on Statistica package 6.0 PL., using U-Mann-Whitney's test, Chi square Yates' test, Kruskal-Wailis' variance analysis, logistic regression and W Shapiro-Wilk's test.

RESULTS

Studied groups were homogeneous with respect to age structure, sex, number of operated eyes and pre-operative size of corneal astigmatism vector K1 (p > .05). The mean values of SIA in group I and II were respectively: 0.63 +/- 0.28 and 1.00 +/- 0.54 and were statistically significant (p < .05). The mean values of K3 post-operative vector measured 6 months following the operation was: 0.54 +/- 0.35 in the group I and 0.96 +/- 0.43 in the group II. Differences between two groups show statistical significance (p < .05). Size of SIA has crucial influence on generating post-operative astigmatism > 1.0 D (p = .03).

CONCLUSIONS

Clear corneal temporal approach 2.8 mm is more beneficial method comparing to superior approach of the same width, because of the scale of SIA.

Clinical evaluation of the arched blade for cataract surgery

PURPOSE

To evaluate the efficacy of the arched blade for making clear corneal incisions in cataract surgery.

METHODS

This prospective study comprised 112 eyes of 74 patients scheduled for cataract surgery. Temporal clear corneal incisions were made with either a 3.2-mm conventional flat blade or the arched blade. The choice of knife was randomly assigned. Two surgeons, one with substantial cataract surgery experience and the other with less experience, performed the surgery. Corneal topography and aberration were examined pre- and postoperatively. The degree of surgically induced astigmatism (SIA) and high order aberration was analysed. The self-sealing ability of the wound was also compared between both blades.

RESULTS

For the less experienced surgeon, the degree of SIA was significantly higher with the 3.2-mm flat blade than with the 3.2-mm arched blade as measured at any time during postoperative follow-up. For the more experienced surgeon, the degree of high order aberration increased significantly with the 3.2-mm flat blade. The incision's self-sealing ability was significantly better when the wound was made with the arched blade rather than with the flat blade.

CONCLUSION

The arched blade proved to be effective in reducing surgically induced astigmatism and high order aberration in cataract surgery, particularly when used by the less experienced surgeon. Using the arched blade should lead to better wound self-sealing and, therefore, safer surgical results.

Epithelial ingrowth after LASIK treatment with scraping and phototherapeutic keratectomy

PURPOSE

To evaluate the effect of phototherapeutic keratectomy (PTK) in combination with manual scraping when removing epithelial ingrowth under a LASIK flap.

MATERIAL AND METHODS

Three patients, who had undergone several surgeries following LASIK in order to remove epithelial ingrowth that was threatening vision, were treated with a flap lift, manual abrasion and PTK. The PTK was performed on both the stromal and the flap side with the aim of eliminating the threat and improving vision. Two patients underwent primary surgery to remove epithelial ingrowth with manual abrasion and PTK. The influence on vision, topography and cell recurrences was evaluated.

RESULTS

Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) improved in four cases and remained good in the fifth case. The refraction did not change significantly. Topography disclosed changes in the irregular astigmatism, explaining the improved BSCVA. Central epithelial ingrowth did not recur, whereas peripheral ingrowth did. The peripheral ingrowth did not progress, except in case 1, where a cyst formed that required surgery.

CONCLUSIONS

It is our belief that adding PTK to manual scraping improves the prognosis for eyes with epithelial ingrowth. It is mainly the central ingrowth that is positively affected. Improved adhesion between the stroma and the flap is one possible explanation.

[The use of intracorneal rings in penetrating keratoplasty]

BACKGROUND

The visual rehabilitation after penetrating keratoplasty (PKP) is affected by postoperative corneal astigmatism. Up to now studies were focused on different trephine systems as well as the suture techniques. A new option for reducing postoperative corneal astigmatism could be the implantation of an intracorneal ring.

PATIENTS AND METHODS

Over a period of 2 years we implanted in 20 patients, who were suffering from keratoconus, Fuchs' dystrophy or bullous keratopathy, an 8-mm cobalt-molybdenum-titanium intracorneal ring in a prospective clinical trial. We used the guided trephine system (GTS) for preparation and a 10-0 nylon double running suture. The mean follow-up period was 16.2 months. A control group of 20 additional patients who underwent PKP was randomized. Topographic astigmatism as well as the spherical equivalent was evaluated after 1, 3, 6 and 12 months, respectively.

RESULTS

Although a lower topographic astigmatism in the intracorneal ring group was reached 12 months postoperatively (3.0 dptr., SD 1.2 versus 4.0 dptr., SD 1.8) no statistical significance was found. The spherical equivalent in that group was lower during the complete evaluation period with a hyperopization in both groups as well. We did not see any immunological reactions caused by the ring.

CONCLUSIONS

Whether the intracorneal ring could be a useful addition to PKP is not yet clear. Therefore more patients need to be enrolled and further studies established.

Astigmatism outcomes of horizontal temporal versus nasal clear corneal incision cataract surgery

PURPOSE

To compare the short- and long-term astigmatism outcomes after cataract surgery using temporal clear horizontal corneal incisions and nasal horizontal clear corneal incisions.

SETTING

Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, Maryland, USA.

METHODS

This retrospective study included a consecutive series of eyes having phacoemulsification with implantation of a 6.0 mm foldable acrylic intraocular lens through a 3.5 mm horizontal clear corneal incision at 180 degrees (temporal incision in right eyes, nasal incision in left eyes). Astigmatism was measured by keratometry readings before surgery and 6 weeks and 12 months postoperatively.

RESULTS

The mean preoperative astigmatism in the 178 eyes (94 right, 84 left) of 161 patients was 0.78 diopter (D); 54.5% of eyes had against-the-rule (ATR) astigmatism, 22.5% had with-the-rule (WTR) astigmatism, and 14.0% were astigmatically neutral. A significant shift toward WTR astigmatism occurred postoperatively. At 6 weeks, 48.3% of eyes had WTR astigmatism and 23.0% had ATR astigmatism. At 12 months, 43.8% had WTR astigmatism and 25.8% had ATR astigmatism. Vector analysis revealed a mean surgically induced astigmatism (SIA) of 1.17 D at 6 weeks and 1.04 D at 12 months. The side of the incision significantly affected SIA. At 6 weeks, temporal incisions yielded a mean SIA of 0.74 D and the nasal incisions, of 1.65 D. This trend in SIA persisted at 12 months: 0.71 D for temporal incisions and 1.41 D for nasal incisions.

CONCLUSIONS

Cataract surgery using a horizontal clear corneal incision induced WTR astigmatism 6 weeks and 12 months postoperatively. Temporal incisions induced significantly less astigmatism than nasal incisions.

Opposite clear corneal incisions on the steep meridian in phacoemulsification

PURPOSE

To evaluate the effect of on-axis opposite clear corneal incisions (OCCIs) in phacoemulsification on reducing preoperative corneal astigmatism and to predict the astigmatic outcome of the incisions.

SETTING

Royal Eye Infirmary, Dorset County Hospital, and Winterbourne Hospital, Dorchester, Dorset, and the Department of Ophthalmology, East Somerset Hospital, Yeovil, Somerset, United Kingdom.

METHODS

This prospective study included all patients (n = 103) who had on-axis OCCIs as a part of routine phacoemulsification with foldable intraocular lens (IOL) implantation performed by 1 surgeon during 2000. Keratometry was done 6 to 8 weeks postoperatively. The differences in the preoperative and postoperative corneal astigmatism and corneal spherical equivalent (SE) were recorded. Surgically induced astigmatism (SIA) was calculated using vector analysis.

RESULTS

The mean reduction in corneal astigmatism was 0.50 diopter (D) (P<.001). The mean SIA was 1.57 D (95% confidence interval [CI], 1.42 to 1.71). There was a weak association between the SIA and the patient's age and axis of preoperative astigmatism. The mean change in SE was +0.02 D (95% CI, -0.08 to +0.12).

CONCLUSIONS

Results indicate that on-axis OCCIs are a reliable and practical way of reducing preexisting corneal astigmatism. The change in SE was negligible and thus can be ignored during biometry.

[Penetrating keratoplasty in keratoconus by using the method of intraoperative corneal compression]

The authors suggested the method of intraoperative dot-type keratocompression to localize the zones of ectasia in keratoconus. Corneocompression is made before corneal transplantation under the monitoring of the operation microscope by a special corneocompressor (from the keratoconus top to its periphery). The sagging degree of the examined corneal portion proportionate to its thinning is in the focus of attention. Simultaneously, the ectasia zone is marked by a 1% solution of brilliant green, after which a decision is made on the possibility of its radical incision by trepans of various sizes, ranging from 7.5 to 11 mm. Penetrating keratoplasty was made by using this method in 116 patients (147 eyes) with keratoconus of degrees III-IV according to Amsler. Better refractive results, including a higher visual acuity and a lower degree of postoperative astigmatism in long-term follow-ups ranging from 2 to 12 years, were ensured in the main group (77 patients, 93 eyes) versus the control group (39 patients, 54 eyes). Finally, the authors suggested, on the basis of their own experience, an operational classification of keratoconus.

Surgical technique for control of postkeratoplasty myopia, astigmatism, and anisometropia

PURPOSE

We previously demonstrated that selective suture removal reduces keratoplasty astigmatism; however, a myopic shift was induced with the increasing number of interrupted sutures removed. This study is an attempt to determine the effects of a modified surgical technique on postkeratoplasty myopia, astigmatism, and anisometropia.

DESIGN

A cohort study compared with historical controls.

METHOD

Optical penetrating keratoplasties were performed on 92 eyes of 84 patients. The study group consisted of 92 consecutive penetrating keratoplasties performed using 12 interrupted 10-0 nylon sutures and a tight 12-bite continuous suture and an average K reading of 46.00 diopters for eyes undergoing combined and intraocular lens exchange procedures. All patients had refraction, keratometry, and videokeratoscopy postoperatively starting at 6 weeks and at the completion of selective suture removal.

RESULTS

Before suture removal, the average spherical equivalent was -0.160 +/- 3.59 diopters; it was -1.58 +/- 3.66 diopters at the completion of suture removal at 1 year and -1.44 +/- 3.72 at the last follow-up visit, averaging 20.7 months. Final refractive, keratometric, and videokeratoscopy astigmatism was 2.81 +/- 1.82, 4.19 +/- 2.94, and 3.58 +/- 2.03 diopters, respectively. Anisometropia, using the spherical equivalent of the operated and fellow eyes, was 2.49 +/- 2.25 diopters at completion of the study. A best-corrected visual acuity of 20/50 or better was achieved in 59% of patients.

CONCLUSIONS

Low myopic spherical equivalent and anisometropia were achieved using a K reading of 46 diopters for calculation of intraocular lens power. The use of tighter continuous sutures and selective removal of fewer interrupted sutures only served to increase final astigmatism, with no significant effect on the final spherical equivalent.

[Possibilities of prophylaxis of the induced "suture" astigmatism in cataract extraction]

Due to a number of reasons, the traditional methods of cataract extraction, i.e. through 8-12 mm limbic incisions, are still widely used in the clinical practice. A frequent occurrence of a high postoperative astigmatism, even if the operation is successful, is the main shortcoming of different variations of the traditional method of cataract extraction. Possibilities of how to neutralize the induced "suture-like" corneal astigmatism were investigated in this study by using two methods: A. a modified technique of applying a continuous corneal Pirs' suture with elements of an accentuated impact in the projection of the horizontal meridian. B. Meridian keratorraphia--application, in the cornea, of an additional compensatory suture in the projection of the horizontal meridian. Studies were made in two groups of patients after extracapsular cataract extraction (ECE) with intraocular lens (IOL) implantation--a total of 30 patients, 30 eyes. The main group was divided into two subgroups--A and B--(10 patients and 10 eye in each) in accordance with a used method of compensating the induced astigmatism. 10 patients were in the control group. A comparative evaluation of changes of a degree of the original astigmatism, which occurred under the influence of the sealing suture, showed that the parameters of induced astigmatism in the control group essentially and reliably (p < 0.001) exceeded the similar parameters registered in both subgroups of the main group; finally, the efficiency of method B in respect to neutralizing the "suture" astigmatism out did the possibilities of method A (p < 0.01).