Techniques for managing common complications of cataract surgery

Design and Evaluation of an Eye Mountable AutoDALK Robot for Deep Anterior Lamellar Keratoplasty

Partial-thickness corneal transplants using a deep anterior lamellar keratoplasty (DALK) approach has demonstrated better patient outcomes than a full-thickness cornea transplant. However, despite better clinical outcomes from the DALK procedure, adoption of the technique has been limited because the accurate insertion of the needle into the deep stroma remains technically challenging. In this work, we present a novel hands-free eye mountable robot for automatic needle placement in the cornea, AutoDALK, that has the potential to simplify this critical step in the DALK procedure. The system integrates dual light-weight linear piezo motors, an OCT A-scan distance sensor, and a vacuum trephine-inspired design to enable the safe, consistent, and controllable insertion of a needle into the cornea for the pneumodissection of the anterior cornea from the deep posterior cornea and Descemet's membrane. AutoDALK was designed with feedback from expert corneal surgeons and performance was evaluated by finite element analysis simulation, benchtop testing, and ex vivo experiments to demonstrate the feasibility of the system for clinical applications. The mean open-loop positional deviation was 9.39 µm, while the system repeatability and accuracy were 39.48 µm and 43.18 µm, respectively. The maximum combined thrust of the system was found to be 1.72 N, which exceeds the clinical penetration force of the cornea. In a head-to-head ex vivo comparison against an expert surgeon using a freehand approach, AutoDALK achieved more consistent needle depth, which resulted in fewer perforations of Descemet's membrane and significantly deeper pneumodissection of the stromal tissue. The results of this study indicate that robotic needle insertion has the potential to simplify the most challenging task of the DALK procedure, enable more consistent surgical outcomes for patients, and standardize partial-thickness corneal transplants as the gold standard of care if demonstrated to be more safe and more effective than penetrating keratoplasty.

Optical Quality Variation of Different Intraocular Lens Designs in a Model Eye: Lens Placed Correctly and in an Upside-Down Position

INTRODUCTION

Intraocular lenses (IOLs) may lose their optical quality if they are not correctly placed inside the capsular bag once implanted. One possible malpositioning of the IOL could be the implantation in an upside-down position. In this work, three aspheric IOLs with different spherical aberration (SA) have been designed and numerically tested to analyse the optical quality variation with the IOL flip, and misalignments, using a theoretical model eye.

METHODS

Using the commercial optical design software OSLO, the effect of decentration and tilt was evaluated by numerical ray tracing in two conditions: in their designed position and flipped with respect to the planned position (IOL is implanted upside down). The theoretical model eye used was the Atchison model eye. Seven IOL designs of +27.00 diopters were used: a lens with negative SA to correct the corneal SA, a lens to partially correct the corneal SA, and a lens to not add any SA to the cornea (aberration-free IOL). These lenses were designed with the aspherical surface located on the anterior and posterior IOL surface. A lens with no aspherical surfaces was also included. For the optical quality analysis, the modulation transfer function (MTF) was used, together with the Zernike wavefront aberration coefficients of defocus, astigmatism, and primary coma.

RESULTS

Off-centring and tilting the IOL reduced overall MTF values and increased wavefront aberration errors. With the IOL correctly positioned within the capsular bag, an aberration-free IOL is the best choice for maintaining optical quality. When the IOL is flipped inside the capsular bag, the optical quality changes, with the aberration-free IOL and the IOL without aspheric surfaces providing the worst results. With the lens in an upside-down position, an IOL design to partially correct corneal SA shows the best optical quality results in decentration and tilt, in terms of MTF and wavefront aberrations.

CONCLUSION

The aberration-free IOL is the best choice when minimal postoperative errors of decentration or tilt are predicted. With IOL flip, the negative SA lens design is the best choice, regarding the root mean square wavefront aberrations. However, in a proper IOL implantation, the IOL designed to partially compensate the corneal SA including asphericity on its posterior surface is the better possible option, even in the presence of decentration or tilt.

Sterile Corneal Infiltrates following Cataract Surgery: Case Series

We report a case series of 26 eyes of 26 patients undergoing planned cataract surgery from December 2021 to March 2022, who were diagnosed as having whitish round infiltrates in the surgical corneal incisions. The infiltrates were detected at the first check after 5-8 days from cataract surgery and were located either within the main corneal incision and/or in the smaller incisions. Corneal infiltrates (CIs) were single or multiple, without epithelial defects, and painless. All infiltrates were initially treated with full topical antibiotic coverage, in order to control eventual and serious postsurgical infection. However, at daily checks, the clinical course of CIs suggested a sterile etiology. For this reason, steroidal topical treatment was maintained for a long time with slow tapering until complete remission of the CIs. All infiltrates resolved completely in around 30-40 days. The surgical instruments and the sterilization process were scrutinized. A white amorphous material was found mainly on non-disposable anterior chamber cannulas and on irrigation/aspiration tips. Disposable cannulas were adopted, and machinery for cleaning and sterilization procedures were reviewed, with specific reference to water softener renewal. Thanks to these precautions, CIs never occurred again. Finally, our hypothesis was an immune corneal reaction to amorphous deposit on cannula tips. This case series describes a previously unknown complication of cataract surgery and our experience might be useful for other surgeons.

Small Aperture IC-8 Extended-Depth-of-Focus Intraocular Lens in Cataract Surgery: A Systematic Review

The aim of this paper is to evaluate the visual outcomes and patient satisfaction of small aperture IC-8 IOLs in cataract patients with or without prior ocular events. A systematic review of full-length original English studies reporting the visual results of small aperture IC-8 IOL implantation after cataract surgery in three databases, PubMed, Web of Science and Scopus, was performed according to the PRISMA statement. The Quality Assessment Tool for case series studies from the National Heart, Lung, and Blood Institute was used to analyze the quality of the studies selected. The search provided 543 articles, of which 22 were included in this systematic review. Significant improvements in uncorrected distance visual acuity (UDVA); uncorrected intermediate visual acuity (UIVA); uncorrected near visual acuity (UNVA); perception of photic phenomena; and patient satisfaction have been reported. Unilateral and bilateral small aperture IC-8 IOL implantation reduces photic phenomena and provides good vision for all distances with high patient satisfaction and minimal postoperative complications. Therefore, the implantation of this IOL may be recommended for patients with cataracts, corneal irregularities and ocular trauma with partial aniridia.

Advanced robotic surgical systems in ophthalmology

In this paper, an overview of advanced robotic surgical systems in ophthalmology is provided. The systems are introduced as representative examples of the degree of human vs. robotic control during surgical procedures. The details are presented on each system and the latest advancements of each are described. Future potential applications for surgical robotics in ophthalmology are discussed in detail, with representative examples provided alongside recent progress.

Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma: A Review of the Literature with Updates on Surgical Management

Pseudoexfoliation syndrome (PES) is a systemic disorder caused by progressive accumulation of extracellular material over various tissues. PES usually determines increased intraocular pressure, changes in the anatomical aspects of the optic nerve, and visual field alterations leading to the diagnosis of pseudoexfoliation glaucoma (PEG). Use of topical medical treatment usually leads to poor results in terms of long-term follow-up but many surgical techniques, such as Argon Laser or Selective Laser Trabeculoplasty, have been proposed for the management of PEG affected patients. The present paper is a review on the pseudoexfoliation syndrome and pseudoexfoliation glaucoma with an update on surgical management.

Manipulator Design and Operation for a Six-Degree-of-Freedom Handheld Tremor-Canceling Microsurgical Instrument

This paper presents the design and actuation of a six-degree-of-freedom (6-DOF) manipulator for a handheld instrument, known as "Micron," which performs active tremor compensation during microsurgery. The design incorporates a Gough-Stewart platform based on piezoelectric linear motor, with a specified minimum workspace of a cylinder 4 mm long and 4 mm in diameter at the end-effector. Given the stall force of the motors and the loading typically encountered in vitreoretinal microsurgery, the dimensions of the manipulator are optimized to tolerate a transverse load of 0.2 N on a remote center of motion near the midpoint of the tool shaft. The optimization yields a base diameter of 23 mm and a height of 37 mm. The fully handheld instrument includes a custom-built optical tracking system for control feedback, and an ergonomic housing to serve as a handle. The manipulation performance was investigated in both clamped and handheld conditions. In positioning experiments with varying side loads, the manipulator tolerates side load up to 0.25 N while tracking a sinusoidal target trajectory with less than 20 μm error. Physiological hand tremor is reduced by about 90% in a pointing task, and error less than 25 μm is achieved in handheld circle-tracing.

Proficiency of eye drop instillation in postoperative cataract patients in Ghana

OBJECTIVE

The purpose of the study was to evaluate the efficacy of postoperative instruction on proficiency of eye drop instillation following cataract surgery, and to determine whether such proficiency correlates with the prevalence and/or duration of irritation and pain experienced in operated eyes.

DESIGN

This was a prospective, nonrandomized control trial with an educational intervention conducted via a single eye clinic in Accra, Ghana.

PARTICIPANTS

The 218 subjects who completed the study were postoperative cataract surgery patients whose surgery had been funded by the nongovernmental organization Unite for Sight.

METHODS

Patients were evaluated on their ability to administer eye drops correctly on their first attempt on postoperative day one. If unsuccessful, patients were given an educational session that consisted of verbal instructions and an educational video. Both groups (successful and unsuccessful) on the first postoperative day were tested again for proficiency on postoperative day 30. The baseline group was evaluated only on postoperative day 30 and consisted of 36 patients.

RESULTS

Of the 133 patients who received the educational session on eye drop instillation, 112 (84%) exhibited proficiency on postoperative day 30 as compared with 29 of 49 patients (59%) who did not receive the intervention. Additionally, there were fewer reports of pain and irritation following cataract extraction in the patients who received the educational session.

CONCLUSION

This study supports the efficacy of patient education in improving proficiency in eye drop instillation and in reducing pain and irritation following cataract extraction surgeries.

Cataract and glaucoma surgery in pseudoexfoliation syndrome: a review

Pseudoexfoliation syndrome is a risk factor in cataract surgery because of the increased weakness of zonular apparatus and reduced pupillary dilatation. The surgical outcome of using phacoemulsification in the central zone, inducing minimal stress on the zonules, inserting a capsular tension ring in selected cases, and stretching the pupil mechanically in eyes with miotic pupils, may turn out to be uneventful in most cases. Postoperative fibrosis with subsequent shrinkage of the capsule is increased in these eyes, and these centripetal forces will further loosen the zonular fibres. Late in-the-bag intraocular lens dislocation is therefore anticipated to become a growing problem in the future. Despite the dysfunctioning of the blood-aqueous barrier in eyes with pseudoexfoliation syndrome, the frequency of postoperative inflammatory reaction is low due to the improvements made in surgical technique and equipment in recent years. Glaucoma frequently occurs in eyes with pseudoexfoliation syndrome. Compared with primary open-angle glaucoma, optic damage is more pronounced in these eyes at the time of diagnosis and response to medical therapy is poorer. Although responses to argon laser therapy and filtering surgery are roughly similar between the two types of glaucoma, there are indications that primary laser trabeculoplasty has a higher success rate in pseudoexfoliation glaucoma than in primary open-angle glaucoma.

Persistent fetal vasculature and minimal fetal vascular remnants

PURPOSE

To determine the significance of persistent fetal vasculature (PFV) and remnants of fetal vessels in the pathogenesis of pediatric unilateral cataracts.

STUDY DESIGN

Prospective observational case series.

PARTICIPANTS

Thirty-one children with unilateral cataract aged between 2 weeks and 15 years.

METHODS

As part of an ongoing prospective clinical trial concerning treatment and etiology of pediatric cataracts, a subgroup of 31 children with unilateral cataracts was defined. The affected eyes received preoperative and intraoperative biomicroscopic examinations to identify characteristic features of PFV and even minimal fetal vascular remnants (MFVRs) at the level of the posterior lens capsule and anterior hyaloid face. In eyes with MFVRs, 3 different severity degrees were assumed, according to different posterior capsule abnormalities: mild, A; moderate, B; and severe, C. All observations were documented on video and analyzed in relation to age (group I, infants between 0 and 1.5 years; group II, preschool children between 1.6 and 5.9 years; group III, schoolchildren between 6 and 16 years).

MAIN OUTCOME MEASURES

Frequency and morphology of characteristic features of PFV and MFVRs of the posterior lens capsule/anterior hyaloid face, lens clouding, and microphthalmos.

RESULTS

All 31 eyes with unilateral congenital cataracts showed signs of PFV syndrome (100%). Characteristic features of PFV were found in 75% of group I eyes, in 8% of group II eyes, and in 67% of group III eyes. Minimal fetal vascular remnants were found in 25% of group I eyes (severity degree C in all eyes), in 92% of group II eyes (severity degree A in 36.4%, B in 27.2%, and C in 36.4%), and in 33% of group III eyes (severity degree A). Associated microphthalmos was found in all eyes in groups I and III and in 73% of group II, whereas axial lengths were equal in both eyes in 27% of group II children with MFVRs.

CONCLUSIONS

Varying degrees of PFV seem to be a frequent cause of unilateral congenital cataracts. Although characteristic features of PFV occurred mainly in infants, eyes of preschool children were usually very mildly affected, showing MFVRs that were detected only by careful observation during surgery. Abnormalities of the central part of the posterior capsule, such as a translucent opacity or a lenticonic area leading to a spontaneous hole during lens aspiration, may be caused by minimal remnants of PFV.