Post-keratoplasty astigmatism management by relaxing incisions: a systematic review

Managing Post Keratoplasty Astigmatism

Corneal transplantation, when used in the correct setting, can significantly improve visual acuity and therefore quality of life. One of the barriers to good vision following keratoplasty is residual post operative surgical astigmatism. Following a thorough literature search, we present the different options available to readers, with regards to how post-operative astigmatism can be approached and managed in order to improve vision. We present available data from the literature, which in some areas are scarce, with a view to collating all of this information in one place, allowing comparison between different modalities of treatment.

Safety and efficacy of a laser refractive procedure in eyes with previous keratoplasty: systematic review and meta-analysis

Post-keratoplasty (KP) patients' visual acuity can be severely limited by ametropia. Irregular astigmatisms are frequently encountered in these patients and is commonly associated with high degrees of hyperopia or myopia. This systematic review investigates the safety and efficacy of laser refractive surgery for post KP vision correction. 31 studies with 683 participants (732 eyes) enrolled in this review. Mean astigmatism improved significantly (mean difference [MD] = -2.70, 95% CI, -3.13 to -2.28, P < .0001). As well as Mean spherical equivalent (MD = -3.35, 95% CI, -3.92 to -2.78, P < .0001). From 586 participants 5.8% lost 2 or more lines of corrected distance visual acuity after treatment. The proportion of eyes with 20/40 uncorrected distance visual acuity or better was reported and the percentage was 46.79% overall. Laser refractive procedures (laser in situ keratomileusis [LASIK] or photorefractive keratectomy [PRK] or transepithelial PRK) on eyes with corneal transplantation were found to be relatively safe and effective. Our systematic review shows there is improvement in all outcomes. Main adverse effects were haze for PRK and epithelial ingrowth for LASIK.

High Astigmatism After Conventional Diameter Deep Anterior Lamellar Keratoplasty in Keratoconus Can Be Successfully Managed With Repeat Wide Diameter Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to describe a new surgical technique to replace a conventional diameter (≤8 mm) deep anterior lamellar keratoplasty (DALK) graft with associated high astigmatism refractory to corneal-based astigmatic procedure/intolerance to contact lenses with a larger diameter (≥9 mm) DALK graft to improve best spectacle-corrected visual acuity (BSCVA).

METHODS

Two eyes from 2 keratoconic patients at Southend University Hospital between December 2019 and June 2021 with a minimum follow-up of 17 months were evaluated. The primary outcome of interest was Snellen BSCVA with a secondary outcome of topographic cylinder.

RESULTS

Patient 1 had undergone initial 8 mm diameter DALK, with residual keratometric astigmatism of nearly 12 diopters (D) postoperatively despite numerous astigmatic interventions, with a BSCVA of 6/60, before undergoing 9 mm diameter repeat modified DALK. After suture removal and subsequent in-the-wound blunt manual relaxing incisions, the patient had a final keratometric astigmatism of 3.5 D, manifest refraction of plano/-3.50 × 175, and a BSCVA of 6/9. Patient 2 had undergone initial 7.75 mm diameter DALK, with residual keratometric astigmatism of 10.5 D with a BSCVA of counting fingers. The patient underwent 9 mm repeat modified DALK with final residual keratometric astigmatism of 3.1 D after suture removal, manifest refraction of -1.00/-2.75 × 25, and BSCVA of 6/9.

CONCLUSIONS

Wide diameter DALK (>9 mm) is effective in the management of conventional diameter DALK (≤8 mm) associated high astigmatism in keratoconus. Creation of a peripheral posterior stromal shoulder also allows safe further titration of residual astigmatism if needed.

Visualization of surgical maneuvers using intraoperative real-time volumetric optical coherence tomography

Ophthalmic microsurgery is traditionally performed using stereomicroscopes and requires visualization and manipulation of sub-millimeter tissue structures with limited contrast. Optical coherence tomography (OCT) is a non-invasive imaging modality that can provide high-resolution, depth-resolved cross sections, and has become a valuable tool in clinical practice in ophthalmology. While there has been substantial progress in both research and commercialization efforts to bring OCT imaging into live surgery, its use is still somewhat limited due to factors such as low imaging speed, limited scan configurations, and suboptimal data visualization. In this paper we describe, to the best of our knowledge, the translation of the fastest swept-source intraoperative OCT system with real-time volumetric imaging with stereoscopic data visualization provided via a heads-up display into the operating room. Results from a sampling of human anterior segment and retinal surgeries chosen from 93 human surgeries using the system are shown and the benefits that this mode of intrasurgical OCT imaging provides are discussed.

Relationship of Density, Depth, and Surface Irregularity of Superficial Corneal Opacification with Visual Acuity

PURPOSE

To explore the relationship between the density, depth, and surface irregularity of superficial corneal opacities and vision.

METHODS

This prospective imaging study included 19 patients with unilateral superficial corneal opacification due to scarring post-microbial keratitis. Each eye underwent an assessment of uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contact lens corrected visual acuity (CLCVA), and Scheimpflug and anterior segment optical tomography imaging. Regression analysis was performed to detect the association between density, depth of scarring, and the surface irregularity in terms of higher order aberrations (HOA), and keratometry and UCVA, CLCVA, and the difference between BSCVA and CLCVA.

RESULTS

The mean logMAR UCVA, BSCVA, and CLCVA were 0.76, 0.35, and 0.28, respectively. The corneal scars had a mean thickness of 158.7 ± 61 µ and density of 65.73 ± 24.46 GSU. Bivariate analysis model for UCVA showed an association with Z₄² secondary astigmatism (p = 0.02), Z₄⁴ quadrafoil (p = 0.01), combined coma Z₃ ^± 1(p = 0.03), and combined HOA Z₃-Z₆ (p = 0.045), out of which Z₄⁴ Quadrafoil (p = 0.04) was most significant with multivariate analysis. Bivariate analysis for BCVA-CLVA showed association with Z₃¹ coma horizontal (p = 0.04), Z₃³ oblique trefoil (p = 0.02), Z₄⁰ primary spherical aberration (p = 0.008), and Z₅ ^- 5 (p = 0.007), out of which Z₃¹ horizontal coma (p = 0.04) and Z₄⁰ spherical aberration (p = 0.009) were significant on multivariate analysis. Change in densitometry, corneal thickness, epithelial:stromal reflectivity ratio, scar depth, and keratometry did not show any significant association with UCVA, BSCVA-CLCVA, or CLCVA.

CONCLUSION

In superficial corneal stromal scarring, deranged surface irregularity parameters like higher-order aberrations affect the final visual acuity more than the depth or density of the opacity.

Undesirable High Astigmatism after Penetrating Keratoplasty in Pseudophakia Corrected with an Add-On Toric Intraocular Lens

The purpose of the present case is to report the visual outcomes of a pseudophakic patient with high post-penetrating keratoplasty astigmatism treated with implantation of toric AddOn® intraocular lens (IOL) in the sulcus. A 79-year-old man with a ophthalmologic history of pseudoexfoliative glaucoma and Fuchs endothelial dystrophy had a graft failure after Descemet's stripping automated endothelial keratoplasty procedure on his right eye. Consequently, a penetrating keratoplasty was performed, and a high corneal astigmatism of -9.8 D to 140° resulted in that eye after selective suture removal. A secondary AddOn® toric IOL customized for the patient with a manufacturer-calculated power of +11.0 D was implanted to 50° in sulcus of the right eye. Subjective refraction was used for IOL calculation. Final refraction was +1.0 D of sphere and -2.0 D of cylinder power to 105°, with spherical equivalent of 0.0 D. Best corrected visual acuity was logMAR 0.1 (20/25, 0.8 decimal) 1 year after the IOL implant. Our case report demonstrates that the toric AddOn® secondary IOL can be effective and safe in correcting residual refractive error of high regular astigmatism after keratoplasty in pseudophakic eyes.

Management of post-keratoplasty ametropia

Even after a successful corneal transplant, patients experience severe refractive errors, impeding their rehabilitation and satisfaction. Refractive errors can be caused by recipient pathology and corneal thickness, as well as intraoperative factors such as donor-host discrepancy, recipient's eccentric trephination, vitreous length, wound apposition, technique of suturing, and suture material. Also, wound healing and the interim between keratoplasty and suture removal contribute to astigmatism. Lamellar keratoplasty outperforms penetrating keratoplasty in terms of endothelial cell loss and endothelial graft rejection, yet the risk of developing refractive errors is comparable. Nonsurgical interventions such as spectacles and lenses fail to provide desirable vision in cases with high astigmatism and corneal irregularity. When these limitations are encountered, surgical interventions including incisional keratotomy, wedge resection, laser refractive surgeries, intracorneal segments, and intraocular lens implantation are employed. However, occasionally, none of these approaches deliver the desired effects, leading to the need for a repeat keratoplasty.

Effects of corneoconjunctival transposition, posterior lamellar keratoplasty and modified deep lamellar endothelial keratoplasty on streak retinoscopy in equine cadaver eyes

OBJECTIVE

Evaluate the effects of corneoconjunctival transposition (CCT), posterior lamellar keratoplasty (PLK) and modified deep lamellar endothelial keratoplasty (DLEK) on streak retinoscopy in equine cadaver eyes.

METHODS

Intraocular pressure (IOP) was maintained at 25 ± 3 mmHg in 35 equine cadaver eyes. Streak retinoscopy was performed prior to (NO VISCO) and following (VISCO) intracameral injection of 1.0 ml of viscoelastic. Following optical coherence tomography (OCT), an axial CCT [n = 11] or PLK [n = 12], or peripheral DLEK [n = 12] was performed. Streak retinoscopy and OCT were repeated postoperatively.

RESULTS

Postsurgical net meridional and spherical refraction for CCT [Horizontal (H): 3.4 (95% CI 2.4-4.4) diopters (D), p < .001, Vertical (V): 3.5 (95% CI 2.7-4.4) D, p < .001, Spherical: 3.5 (95% CI 2.6-4.3) D, p < .001] and PLK [H: 3.2 (95% CI 2.2-4.1) D, p < .001, V: 2.8 (95% CI 2.0-3.6) D, p < .001, Spherical: 3.0 (95% CI 2.2-3.8) D, p < .001] were significantly increased from presurgical (VISCO) values. No difference between presurgical (VISCO) and postsurgical values were identified for the DLEK. Postoperative OCT revealed space between anterior and posterior corneal grafts and corneal undulation associated with suture placement.

CONCLUSION

Meridional and spherical refraction had a hyperopic shift following CCT and PLK, with a significantly higher value in the vertical meridian for the CCT. Pre- and postoperative refraction was not significantly different for the DLEK. This supports that the DLEK has a lesser effect on immediate postoperative refraction compared with CCT or PLK.

Repeated Femtosecond Laser-Assisted Astigmatic Keratotomies in Post-Keratoplasty Eyes

Visual rehabilitation after a keratoplasty is often compromised due to high amounts of residual astigmatism. Femtosecond laser-assisted astigmatic keratotomy (FLAK) is gaining popularity in decreasing this astigmatism. Though one set of two incisions suffices in most cases, sometimes the treatment proves insufficient and additional treatment is required. This case series evaluates the outcomes in patients who underwent two consecutive FLAK sets to correct post-keratoplasty residual astigmatism. All repeated FLAK cases performed on post-keratoplasty eyes were reviewed in a high-volume clinic as a non-comparative retrospective case series. The data extracted include the procedure parameters, time between procedures, refraction including sphere, astigmatism, spherical equivalent (SE), and uncorrected and best-spectacle-corrected distance visual acuity (UDVA, BSDVA, respectively). Eleven eyes of eleven patients aged 25.5 ± 10 treated with more than one FLAK procedure were identified. The average follow-up time was 6 months after the first FLAK and 24 ± 10 months after the second. The second FLAK was performed six months after the first. The preoperative mean astigmatism was −9.59 ± 2.36 D. At the final follow-up, the mean astigmatism decreased to −5.38 ± 1.79 D (p = 0.001). Repeated FLAK procedures achieved a significant and stable reduction of astigmatism in post-keratoplasty eyes. This procedure shows safety and effectivity in these complex eyes and may prevent the need for a further keratoplasty.

The treatment of end-stage corneal disease: penetrating keratoplasty compared with Boston type 1 keratoprosthesis

Penetrating keratoplasty (PKP) yields excellent results for restoring vision in end-stage corneal diseases. However, its success is limited to high-risk diseases such as aniridia, chemical burns, autoimmune corneal diseases, and herpetic eye disease. Boston type 1 keratoprosthesis (BKPro) offers another option to these patients. Since 1992, improvements in perioperative management and device construction have significantly increased the use of BKPro worldwide and challenged the therapeutic role of PKP in these patients. This review aims to evaluate BKPro's place in the treatment algorithm of these high-risk patients to assist surgeons' decision-making. PKP and BKPro are compared in three outcome categories: visual acuity, graft retention and failure, and complications profile. Special attention is given to comparing secondary BKPro versus repeated PKP as well as primary BKPro versus primary PKP. We conclude that secondary BKPro bears a better prognosis than repeated PKP in most high-risk patients. Similarly, primary BKPro likely confers improved outcomes over primary PKP in most high-risk recipients. However, current evidence is based on retrospective designs, and controlled prospective randomized trials are required to validate these conclusions.

[Optical properties of the cornea after different modifications of penetrating keratoplasty]

PURPOSE

Comparative analysis of optical properties of the cornea after different modifications of penetrating keratoplasty.

MATERIAL AND METHODS

The study included 56 patients (56 eyes) divided into three study groups according to the surgery technique. Group I included 17 patients (17 eyes) after one-piece mushroom keratoplasty, group II - 21 patients (21 eyes) after two-piece mushroom keratoplasty and group III - 18 patients (18 eyes) after penetrating keratoplasty. In addition to standard examination methods, before surgery and in the course of the follow-up all patients underwent software-powered corneal densitometry on the anterior segment analyzer (Pentacam HR, "Oculus", Germany), as well as an assessment of the degree and regularity of postoperative astigmatism.

RESULTS

Comparison of the obtained results revealed with a high degree of confidence higher values of the total specific light scattering after two-piece mushroom keratoplasty throughout the entire observation period (p<0.05). At the same time, there was no statistically significant difference in visual acuity between the three study groups (p>0.05). A statistically significant increase in the level of induced astigmatism was revealed after penetrating keratoplasty.

CONCLUSION

The observed increase in light scattering after two-piece mushroom keratoplasty does not lead to a decrease in visual acuity. The interface in the optical zone of the cornea formed by a microkeratome does not affect the degree and regularity of induced astigmatism.

[Comparative evaluation of the results of one- and two-piece mushroom keratoplasty]

PURPOSE

To compare and evaluate the outcomes of one- and two-piece mushroom keratoplasty configurations for various corneal pathologies.

MATERIAL AND METHODS

A total of 32 patients (32 eyes) with corneal perforations, descemetocele and deep corneal opacities underwent surgery. Depending on the surgery technique, the patients were divided into 2 groups: group I (17 eyes) underwent manual one-piece mushroom keratoplasty according to our own technique; group II (15 eyes) underwent modified two-piece microkeratome-assisted mushroom keratoplasty according to the technique by M. Busin. All patients underwent clinical and functional studies before surgery and in the course of a 1-year follow-up.

RESULTS

Transparent engraftment of the cornea was achieved in 82 and 80% of cases; best corrected visual acuity (BCVA) averaged 0.57±0.19 and 0.53±0.17; spherical component of refraction varied from 1.25 to +5.5 and from 1.25 to 6.0 diopters; mean corneal astigmatism was 3.15±1.73 and 3.21±1.89 diopters in groups I and II, respectively. At 6 months after surgery, the mean endothelial cell density (ECD) was 2336±198 and 2291±175 cells/mm², at 1 year - 2041±189 and 1955±161 cells/mm² in groups I and II, respectively.

CONCLUSION

One- and two-piece mushroom keratoplasty is effective in surgical treatment of various corneal pathologies ensuring a high rate of transparent corneal engraftment. The revealed risk of false chambers formation between separate parts of the graft after the two-piece method could in most cases be eliminated by re-injecting air into the anterior eye chamber.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Topography-Guided Photorefractive Keratectomy for Postkeratoplasty Astigmatism: Long-Term Outcomes

PURPOSE

To evaluate the long-term efficacy and safety of topography-guided photorefractive keratectomy (TG-PRK) for postkeratoplasty refractive error correction.

METHODS

A retrospective interventional case series of 54 eyes of 50 patients who underwent previous corneal transplants. Unaided distance visual acuity (UDVA) and best corrected visual acuity (CDVA), manifest refraction, mean central keratometric value, mean keratometric astigmatism, and postoperative complications were reviewed.

RESULTS

Final follow-up was at mean 31 (±17) months. Sixteen point seven percent of eyes underwent more than 1 surface ablation. Mean UDVA improved from 0.96 ± 0.06 logarithm of the minimum angle of resolution (LogMAR) preoperatively to 0.46 ± 0.05 LogMAR of resolution at the final follow-up (Bonferroni, P < 0.0001). Mean UDVA improved by 4.4 Snellen lines. Improvement in CDVA was not significant, although a significant improvement was noted when eyes with preoperative CDVA <20/40 were analyzed separately (t test, P = 0.005). Mean astigmatism improved from -4.4 ± 0.26 D preoperatively to -2.4 ± 0.26 D at the final follow-up (Bonferroni, P < 0.0001), whereas mean SEQ improved from -2.5 ± 0.39 D preoperatively to -1.1 ± 0.25 D (Bonferroni, P = 0.02). In total, 9% at the preoperative visit and 55% at the final visit had less than 2 D of astigmatism, respectively. Keratometric astigmatism decreased from 5.24 ± 0.36 D preoperatively to 2.98 ± 0.34 D at the final follow-up (t test, P < 0.0001). No eyes developed clinically significant haze, 14.8% developed regression, and 13% had a reduction of 2 or more CDVA lines.

CONCLUSIONS

Postkeratoplasty topography-guided photorefractive keratectomy has good long-term efficacy and safety, resulting in significant UDVA, refractive, and keratometric improvement. Regression can occur after the first year of treatment, emphasizing the importance of long-term follow-up.

Comparison of manual and femtosecond astigmatic keratotomy in the treatment of postkeratoplasty astigmatism

PURPOSE

To compare the outcomes of femtosecond astigmatic keratotomy (FSAK) and manual astigmatic keratotomy (AK) in treatment of postkeratoplasty astigmatism.

METHODS

A retrospective, comparative, pairwise-matched case series including 150 patients who underwent either FSAK (n = 75) or manual AK (n = 75) for the treatment of astigmatism (>3.00 D) following penetrating keratoplasty or deep anterior lamellar keratoplasty. Pairwise matching for baseline variables (age, visual acuity and astigmatism) was performed.

RESULTS

Mean age was 57.5 ± 16.0 years. The FSAK group had significantly better postoperative best-corrected visual acuity (BCVA) (p = 0.010), uncorrected visual acuity (UCVA) (p = 0.049), corneal astigmatism (p = 0.020) and manifest astigmatism (p < 0.001) compared with the manual AK group. Gain of ≥3 lines in BCVA (logMAR) was seen in five eyes (6.7%) and 21 eyes (28.0%) in manual AK and FSAK, respectively (p = 0.005). Alpins vector analysis showed lower (closer to 0) index of success (0.50 ± 0.24 and 0.79 ± 0.48, p < 0.001) and higher (closer to 1) correction index (0.94 ± 0.45 and 0.74 ± 0.55, p = 0.020) in FSAK compared with manual AK. Corneal and manifest astigmatism improved significantly in both groups, while BCVA and UCVA improved significantly in FSAK only. Repeat AK rate was 32% (24 eyes) in manual AK and 4% (three eyes) in FSAK (p < 0.001). Overcorrection-related re-suturing rate was 0% in manual AK and 8% (six eyes) in FSAK (p = 0.037). There was one microperforation (1.3%) in FSAK, and there were no occurrences of graft dehiscence, infectious keratitis or graft rejection.

CONCLUSIONS

Both manual AK and FSAK were safe and effective in reducing postkeratoplasty astigmatism. FSAK had superior visual and keratometric outcomes compared with manual AK.

Effect of Stem Cell-Derived Extracellular Vesicles on Damaged Human Corneal Endothelial Cells

Purpose

Human corneal endothelial cells (HCECs) are essential to visual function; however, since they have limited proliferative capacity in vivo, they are prone to corneal endothelial dysfunction. At present, the only treatment is a corneal transplantation from donor cadavers. Also, due to a global shortage of donor corneas, it is important to find alternative strategies. Recent studies highlight that stem cell–derived extracellular vesicles (EVs) play a relevant role in stem cell-induced regeneration by reprogramming injured cells and inducing proregenerative pathways. The aim of this work is to evaluate whether EVs derived from mesenchymal stem cells (MSC-EVs) are able to promote regeneration of damaged HCECs.

Methods

We isolated HCECs from discarded corneas in patients undergoing corneal transplantation or enucleation (N = 23 patients). Bone marrow mesenchymal stem cells (MSCs) were obtained from Lonza, cultured, and characterized. MSC-EVs were obtained from supernatants of MSCs. In order to establish a valid in vitro damage model to test the regenerative potential of EVs on HCECs, we evaluated the proliferation rate and the apoptosis after exposing the cells to serum-deprived medium at different concentrations for 24 hours. We then evaluated the HCEC migration through a wound healing assay.

Results

In the selected serum deprivation damage conditions, the treatment with different doses of MSC-EVs resulted in a significantly higher proliferation rate of HCECs at all the tested concentrations of EVs (5‐20 × 10³ MSC-EV/cell). MSC-EVs/cell induced a significant decrease in number of total apoptotic cells after 24 hours of serum deprivation. Finally, the wound healing assay showed a significantly faster repair of the wound after HCEC treatment with MSC-EVs.

Conclusions

Results highlight the already well-known proregenerative potential of MSC-EVs in a totally new biological model, the endothelium of the cornea. MSC-EVs, indeed, induced proliferation and survival of HCECs, promoting the migration of HCECs in vitro.

Initial High-Dose Prophylaxis and Extended Taper for Mushroom Keratoplasty in Vascularized Herpetic Scars

PURPOSE

To report the outcomes of initial high-dose and extended taper of antiviral and steroid prophylaxis for the treatment of eyes with high-risk vascularized herpetic corneal scars that underwent 2-piece mushroom keratoplasty (MK).

DESIGN

Prospective interventional case series.

METHODS

In this single-center study, 52 consecutive eyes with vascularized (≥2 quadrants) herpetic corneal scars underwent 2-piece microkeratome-assisted MK. Initial high-dose and extended taper of combined oral and topical antiviral and steroid prophylaxis was administered. Outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), endothelial cell density, immunologic rejection, herpetic recurrence, and graft failure rates.

RESULTS

Excluding patients with vision-impairing comorbidities, baseline BSCVA (1.73 ± 0.67 logMAR) significantly improved annually during the first 2 years (P < .001, P = .016), reaching 0.17 ± 0.18 logMAR at year 2, and remaining stable up to 10 years (P = .662). At 2 years, 86% of eyes saw ≥20/40, 55% saw ≥20/25, and 18% saw ≥20/20 Snellen BSCVA. RA exceeded 4.5 diopters in 7% of cases after wound revision for high-degree astigmatism in 7 cases. Endothelial cell loss was 40.9% at 1 year with an annual decline of 3.1% over 10 years. The 10-year cumulative risk for immunologic rejection, herpetic recurrence, and graft failure was 9.7%, 7.8%, and 7.6%, respectively.

CONCLUSIONS

Initial high dose and extended taper of antiviral and steroid prophylaxis for MK in high-risk, vascularized herpetic corneal scars achieves clinical outcomes that remain stable for up to 10 years after surgery with minimal risk of immunologic rejection, herpetic recurrence and graft failure.

"Harmonization" of donor and recipient tomography in corneal transplantation

The applicability of donor and recipient tissue matching in corneal transplantation ("harmonization") to reduce residual astigmatism after keratoplasty was simulated using Matlab software. The height profile of the donor and recipient corneas was measured using the anterior segment optical coherence tomography (AS-OCT) Casia 2. After best fit of the donor button in the recipient bed the mean height difference as the mismatch, which had to be minimized, was derived from the height profile of the donor and recipient corneal front and back surfaces. The donor button was rotated in the recipient bed to extract the best fit situation where the mean height difference was minimized. After successful simulation, the procedure will be transferred to real measurement data.

Corneal transplantation in the modern era

Corneal blindness is one of the major causes of reversible blindness, which can be managed with transplantation of a healthy donor cornea. It is the most successful organ transplantation in the human body as cornea is devoid of vasculature, minimizing the risk of graft rejection. The first successful transplant was performed by Zirm, and since then, corneal transplantation has seen significant evolution. It has been possible because of the relentless efforts by researchers and the increase in knowledge about corneal anatomy, improvement in instruments and advancements in technology. Keratoplasty has come a long way since the initial surgeries wherein the whole cornea was replaced to the present day where only the selective diseased layer can be replaced. These newer procedures maintain structural integrity and avoid catastrophic complications associated with open globe surgery. Corneal transplantation procedures are broadly classified as full-thickness penetrating keratoplasty and partial lamellar corneal surgeries which include anterior lamellar keratoplasty [sperficial anterior lamellar keratoplasty (SALK), automated lamellar therapeutic keratoplasty (ALTK) and deep anterior lamellar keratoplasty (DALK)] and posterior lamellar keratoplasty [Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK)] broadly.

A novel blunt dissection technique to treat modified deep anterior lamellar keratoplasty (DALK)-associated high astigmatism

OBJECTIVES

To describe a new surgical technique to correct a high astigmatism following modified deep anterior lamellar keratoplasty (DALK) and to evaluate the associated clinical outcomes.

METHODS

Retrospective interventional case series included eyes with high astigmatism following modified DALK performed between July 2012 and June 2016. The prevalence of keratometric astigmatism (KA) higher than 4.5 diopters (D) was evaluated after complete suture removal. Surgical correction was obtained by opening the surgical wound at the steeper meridian and carrying out a blunt dissection at the graft-host surface of contact under keratoscopic control. KA, Refractive astigmatism (RA), and best spectacle-corrected visual acuity (BSCVA) were measured preoperatively and at 1, 12, and 24 months postoperatively. Vector analysis of 1 year change in KA was performed.

RESULTS

High astigmatism was found in 47 of 511 eyes (9.2%). KA (mean ± standard deviation [SD]) decreased from 7.67 ± 2.78 to 3.10 ± 1.37 D at 1 month after astigmatic correction (p < 0.001) with no subsequent significant change. Vector analysis of 1 year change in KA: surgically induced astigmatism was 5.30 ± 3.29 D and mean absolute angle of error was 6.97 ± 4.25°. BSCVA improved from 0.21 ± 0.20 logMAR preoperatively to 0.11 ± 0.13 logMAR (p < 0.001); RA decreased from 6.32 ± 2.56 to 2.61 ± 1.05 D (p < 0.001). No intra- or post-operative complications occurred.

CONCLUSIONS

High astigmatism is present in <10% of cases after modified DALK and can be effectively managed by means of blunt relaxing dissection at the graft-host junction.

Long-term Results of Corneal Wedge Resection for High Postkeratoplasty Astigmatism

PURPOSE

To present the results of corneal wedge resection in postkeratoplasty astigmatism, performed by the same surgeon using the same nomogram over a 25-year period.

METHODS

This is a retrospective observational study. The sample was obtained from the medical records of all patients who underwent penetrating or deep lamellar keratoplasty, performed by a single surgeon from 1993 to 2018. All surgeries were performed using a diamond knife, on the flat meridian, involving the keratoplasty scar and closed with five 10-0 nylon sutures.

RESULTS

A total of 39 eyes were included. The keratometry measured cylinder improved from 7.99 ± 0.25 to 2.5 ± 0.3 D at 12 months and remained stable thereafter (a mean follow-up of 76.3 months). Best spectacle corrected visual acuity increased from 0.35 ± 0.01 to 0.57 ± 0.02 at 12 months and remained stable thereafter. There was a coupling ratio of 0.08 ± 0.03 D at 12 months. There were no corneal graft rejections or loss of best spectacle corrected visual acuity on this series.

CONCLUSIONS

Corneal wedge resection is a valuable resource for the management of high postkeratoplasty astigmatism. It is a safe and reproducible procedure, with stable results at 12 months and thereafter.

Rotational stability of a new multicomponent intraocular lens

Purpose

To evaluate the rotational stability of the Precisight multicomponent intraocular lens (MCIOL) following primary implantation and after enhancement procedures.

Patients and methods

Prospective, single-center study of eyes that underwent routine cataract surgery with implantation of a non-toric MCIOL, (Precisight, InfiniteVision, Optics, Strasbourg, France). The axis of the MCIOL was measured with a line bisecting the two dialing holes in the front lens. Intraoperative orientation was determined using a digital surgical guidance system while the postoperative orientation was determined using slit-lamp imaging. Two populations were analyzed: eyes that only underwent cataract surgery (PRIM) and eyes that also underwent enhancement (ENH), consisting of surgical front optic exchange. Both populations had 3 observation visits: first implantation (P-Op); 3 months (3mo) and 6 months (6mo) after primary surgery. The ENH group had an additional fourth visit that corresponded to the enhancement surgery (E-Op). The main outcome measure was mean absolute change in MCIOL orientation (degrees). The effects of axial length (AL) and anterior chamber depth (ACD) on IOL rotational stability were examined.

Results

Thirty-three eyes received MCIOL of which 29 had usable orientation images. Of these, 12 were in the PRIM group and 17 underwent ENH. Regarding the mean absolute rotation, among PRIM eyes, P-Op to 3mo was 3.03±2.45 degrees; P-Op to 6mo, 2.28±1.54 degrees; and 3–6mo, 2.37±1.56 degrees. Among the ENH eyes, P-Op to 3mo was 3.09±1.68; E-Op to 6mo, 2.71±3.30 and P-Op to 6mo, 3.62±3.42. There were no significant differences in the IOL rotation. There were no statistical differences in rotational stability between the ENH and PRIM groups. There was no correlation between IOL rotation and AL or ACD.

Conclusion

Precisight appears to be rotationally stable. The enhancement procedure does not affect rotational stability.

Astigmatismus

Der Astigmatismus ist der weltweit häufigste Refraktionsfehler vor Hypermetropie und Myopie. Man unterscheidet den äußeren vom inneren Astigmatismus. Der äußere Astigmatismus kann weiter in „mit der Regel“, „gegen die Regel“ und „schräg“ unterteilt werden. Die Summierung des äußeren und inneren Astigmatismus ergibt den refraktiven Zylinder. Astigmatismus wurde lange als zweidimensionales Phänomen gesehen, doch erst die dreidimensionale Betrachtung hat den Blick auf bestehende Analyseverfahren (Topo- und Tomographie) erweitert. Die Vektoranalyse nach Alpins ist hierbei eine bekannte Methode zur Therapieplanung. Zur Therapie des Astigmatismus stehen konservative Optionen wie Brille oder torische Kontaktlinse sowie unterschiedlichste chirurgische Verfahren wie photorefraktive Keratektomie, Femtosekundenlaser-assistierte Keratotomie, Laser-in-situ-Keratomileusis, „small-incision lenticule extraction“ und die Implantation torischer Intraokularlinsen zur Verfügung.

[Astigmatism]

Astigmatism is the most frequent refractive error worldwide followed by hyperopia and myopia. Internal astigmatism has to be differentiated from external astigmatism. Furthermore, external astigmatism can be divided into "with the rule", "against the rule" and "oblique". The summation of internal and external astigmatism results in the refractive cylinder. Astigmatism has for a long time been regarded as a two-dimensional phenomenon; however, only a three-dimensional consideration expanded the view on existing analytical methods (topography and tomography). Alpins' vector analysis is a commonly used method for treatment planning. Multiple options exist for treatment of astigmatism with conservative approaches, such as eyeglasses or toric contact lenses as well as various surgical procedures, such as photorefractive keratectomy, femtosecond laser-assisted keratotomy, laser in-situ keratomileusis, small incision lenticule extraction and toric intraocular lens implantation.

Femtosecond laser-assisted astigmatic keratotomy: a review

Background

Astigmatic keratotomy (AK) remains an accessible means to correct surgically induced or naturally occurring astigmatism. The advantages of femtosecond laser-assisted astigmatic keratotomy (FSAK) over conventional methods have been recognized recently.

Main text

This review evaluates the efficacy, complications, and different methods of FSAK for correction of astigmatism in native eyes and those that underwent previous penetrating keratoplasty (PKP).

The penetrating and intrastromal FSAK (IFSAK) techniques can reduce post-keratoplasty astigmatism by 35.4% to 84.77% and 23.53% to 89.42%, respectively. In native eyes, the penetrating and IFSAK techniques reduce astigmatism by 26.8% to 58.62% and 36.3% to 58% respectively, implying that the magnitude of the astigmatic reduction is comparable between the two FSAK procedures. Nonetheless, IFSAK offers the additional advantages of almost no risk of infection, wound gape, and epithelial ingrowth. The use of nomograms, anterior-segment optical coherence tomography, and consideration of posterior cornea and corneal biomechanics are helpful to enhance the efficacy and safety of FSAK. The complications of FSAK in eyes that underwent PKP include overcorrection, visual loss, microperforations, infectious keratitis, allograft rejection, and endophthalmitis. The reported difficulties in native eyes include overcorrection, anterior gas breakthrough, and suction loss.

Conclusions

In eyes that underwent PKP, FSAK effectively reduces high regular or irregular astigmatism, with rare and manageable complications. Nevertheless, the drawbacks of the procedure include the potential loss of visual acuity and low predictability. For native eyes undergoing femtosecond laser-assisted cataract surgery, IFSAK is a good choice to correct low astigmatism (< 1.5 diopters). The refractive effect of astigmatism from the posterior cornea needs to be considered in the nomograms for native eyes undergoing refractive cataract surgery. To further improve the efficacy of FSAK, more large-scale randomized studies with longer follow-up are needed.