Gonioscopy-Assisted Transluminal Trabeculotomy in Uveitis-Related Ocular Hypertension and Glaucoma.

PRCIS: Gonioscopy-assisted transluminal trabeculotomy (GATT) may be an effective first-line surgery for decreasing intraocular pressure (IOP) and medication burden in patients with uveitis-related ocular hypertension (OHT) or glaucoma. OBJECTIVE: The purpose of the study is to determine the efficacy of GATT in lowering IOP in uveitis-related OHT or glaucoma. METHODS: Retrospective case series that included patients with uveitis-related OHT or glaucoma who underwent GATT with or without concomitant cataract extraction and intraocular lens implantation at 2 Canadian academic centres from July 2018 to May 2022. Primary outcomes were: complete (no medications) and qualified success (with medication), and failure defined as (1) IOP >21 mm Hg with maximal medical therapy, (2) the need for additional glaucoma procedure, (3) loss of light perception secondary to glaucoma, and (4) IOP <6 mm Hg for 3 months. RESULTS: Twenty-one eyes from 18 patients were included with a mean preoperative IOP of 26.2 ± 7.3 mm Hg on 4.3 ± 0.7 classes of glaucoma drops. The average follow-up was 29.2 ± 17.6 months and 76% of eyes (n = 16) had reached at least 12 months of follow-up. At the 12-month follow-up visit, there was a significant decrease in average IOP by 9.9 ± 7.9 mm Hg (38%, P = 0.005) and a decrease of 1.9 in glaucoma medication classes ( P = 0.002). Of eyes, 14% achieved complete success, whereas 80% of eyes achieved qualified success. Six eyes failed (29%) and 5 patients (24%) required additional glaucoma surgery. The most common postoperative complication was hyphema (n = 9; 43%). CONCLUSION: This small case series suggests that GATT may be an effective first-line surgery for decreasing IOP and medication burden in patients with uveitis-related OHT or glaucoma. Further studies with longer follow-ups should be conducted to assess its long-term outcomes.

Refractive outcomes of immediately sequential bilateral cataract surgery in eyes with long and short axial lengths.

PURPOSE: To report the refractive outcomes of long (≥25.00 mm) and short (≤22.00 mm) axial length (AL) eyes undergoing immediately sequential bilateral cataract surgery (ISBCS). METHODS: In this retrospective cohort study, patients who underwent ISBCS were identified and eyes of patients with bilateral long and short ALs were included. Pre- and postoperative biometry, autorefraction, and ocular comorbidities or complications were recorded. The primary outcome was the mean refractive prediction error. RESULTS: Thirty-seven patients (74 eyes) with long ALs and 18 patients (36 eyes) with short ALs were included. The means ± standard deviations of the ALs were 26.40 ± 1.38 mm and 21.44 ± 0.46 mm in the long and short AL groups, respectively. In long AL eyes, the mean absolute error from the biometry-predicted refraction was - 0.16 ± 0.46 D, corresponding to 74% of eyes achieving a refraction within ±0.50 D of the predicted value. In short AL eyes, the mean absolute error was - 0.63 ± 0.73 D, corresponding to 44% of eyes achieving a refraction within ±0.50 D of the predicted value. Eight (44.4%) patients with short AL eyes had a myopic deviation greater than ±0.50 D from the predicted result in both eyes. CONCLUSIONS: Compared to patients with long AL eyes, ISBCS in patients with short ALs had a wider variance in refractive outcome and a lower rate of achieving a postoperative refraction within ±0.50 D of the predicted target.

Management of Uveitis-Glaucoma-Hyphema Syndrome Caused by Soemmering Ring Cataract: Case Report and Literature Review.

We describe a rare case of Soemmering's ring-induced uveitis-glaucoma-hyphema (UGH) syndrome, caused by an undisplaced, in-the-bag intraocular lens (IOL) 16 years after implantation. The presenting symptoms were recurrent episodes of transient monocular vision loss, which prompted extensive unremarkable investigations. Ultrasound biomicroscopy (UBM) eventually revealed an enlarging Soemmering's ring contacting the posterior iris and causing UGH syndrome. This is a unique case because the IOL haptics remained in the bag. Anterior vitrectomy, Soemmering's ring extraction, IOL exchange to a 3-piece IOL, and implantation of a trabecular meshwork bypass microstent were performed. IOP control and both functional and structural stability were achieved long term. Soemmering's ring-induced UGH syndrome should be on the differential of a patient with previous cataract surgery and elevated IOP complaining of visual disturbances. Early diagnosis with UBM and surgical intervention may provide optimal outcomes.

Visual outcomes and rotational stability of a new non-diffractive extended-vision toric intraocular lens.

OBJECTIVE: To evaluate visual outcomes and intraocular lens (IOL) rotational stability of patients undergoing immediate sequential bilateral cataract surgery with a non-diffractive extended-depth-of-focus toric IOL. DESIGN: Non-comparative single-centre cohort study. PARTICIPANTS: Twenty patients (40 eyes) with significant cataracts and corneal astigmatism who underwent immediate sequential bilateral cataract surgery with the AcrySof IQ Vivity Extended Vision Lens (Alcon Laboratories Inc, Fort Worth, Tex.). METHODS: Binocular uncorrected visual acuities (UCVA) and monocular best-corrected visual acuities (BCVA) were assessed at distance (6 m), intermediate (66 cm), and near (40 cm) postoperatively at 1 week and 3 months. The rotational stability of each IOL was assessed at 1 day, 1 week, and 3 months postoperatively. A validated questionnaire (Questionnaire for Visual Disturbances [QUVID]) was used for patient-reported subjective visual disturbances preoperatively at a 3-month follow-up. RESULTS: Binocular distance, intermediate, and near UCVAs (mean ± SD) were 0.00 ± 0.16, 0.09 ± 0.08, and 0.14 ± 0.11 logMAR at 1 week and 0.01 ± 0.06, 0.08 ± 0.08, and 0.14 ± 0.07 logMAR at 3 months postoperatively, respectively. Distance monocular BCVA improved from 0.22 ± 0.23 logMAR preoperatively to 0.02 ± 0.06 logMAR at 3 months. Monocular BCVAs at 3 months were 0.08 ± 0.08 logMAR at intermediate distance and 0.05 ± 0.08 logMAR at near distance. IOL rotation from the intended placement axis was 2.5 ± 1.7 degrees at 1 week and 1.7 ± 1.7 degrees at 3 months postoperatively. CONCLUSIONS: The AcrySof IQ Vivity Extended Vision IOL achieved good UCVAs and BCVAs for distance, intermediate, and near vision. This IOL also provided excellent rotational stability for astigmatism correction.

Development and validation of the Iris Glare, Appearance, and Photophobia questionnaire for patients with iris defects.

PURPOSE: To validate the Iris Glare, Appearance, and Photophobia (Iris GAP) questionnaire, a new symptom-based and appearance-based quality-of-life measure for patients with iris defects. SETTING: Single tertiary glaucoma clinic in Toronto, Ontario, Canada. DESIGN: Prospective cohort study. METHODS: Patients with varying degrees of iris defects were enrolled. Patients completed the Iris GAP questionnaire and the glare and driving subscales of the Refractive Status and Vision Profile (RSVP) questionnaire. Test-retest reliability, defined by Cronbach α and intraclass correlation coefficients (ICCs), was evaluated with repeat testing 2 weeks later. RESULTS: The study included 73 patients with iris defects, 68 controls with no iris defects, 77 patients with peripheral iridotomies (PIs) or transillumination defects (TIDs), and 22 patientswith surgically repaired irides (n = 22). Iris GAP scores ranged from 0 to 32 with a 97% completion rate. Iris GAP had high test-retest reliability (Cronbach α = 0.866, ICC = 0.953, P < .0005). Iris GAP scores were reliably distinguishable between patients with iris defects, repaired iris defects, and PIs and TIDs and controls (1-way analysis of variance, P < .0005). In pairwise comparisons, the major defect group had statistically significant higher scores than any of the other groups ( P < .005 for each). The control and repaired groups had the lowest scores, whereas the PI/TID group had intermediate scores. 9 patients underwent iris repair between tests and had a mean difference of 8.2 ± 6.2 points between their preoperative and postoperative scores ( P = .004). Iris GAP scores positively correlated with RSVP scores ( R2 = 0.73). CONCLUSIONS: Iris GAP can reliably evaluate symptomatology and patient-reported appearance in patients with iris defects.

A mysterious myopic surprise.

A 73-year-old man with an ocular history of inactive age-related macular degeneration and chronic angle-closure glaucoma (CACG) in both eyes recently underwent femtosecond laser-assisted cataract surgery/phacoemulsification and intraocular lens (IOL) implantation with simultaneous Hydrus microstent (Ivantis, Inc.) implantation in the left eye. Although there was some reported subincisional iris prolapse due to intraoperative floppy iris, the case was otherwise uneventful according to the referring surgeon. Two months postoperatively, he was referred to our office for a myopic surprise of approximately 2.0 diopters (D) in the left eye (Figure 1JOURNAL/jcrs/04.03/02158034-202202000-00022/figure1/v/2022-01-26T192641Z/r/image-tiff). Of note, he has a distant history of acute ACG and complicated cataract surgery in the right eye with a failed trabeculectomy. He subsequently had laser peripheral iridoplasty to pull the iris away from the angle in the right eye (Figure 2JOURNAL/jcrs/04.03/02158034-202202000-00022/figure2/v/2022-01-26T192641Z/r/image-tiff). His topical intraocular pressure (IOP)-lowering medications at presentation included dorzolamide-timolol 1 drop twice daily in the left eye and 1 drop of timolol in the right eye once daily. His past medical history is significant for hypertension and benign prostatic hyperplasia, and his oral medications include Tamsulosin (Flomax), Irbasartan (Avapro), and Atenolol. On examination, he had an UCDVA of 20/20 in the right eye and 20/80 in the left eye, and a BCDVA of 20/20 in the right eye and 20/25 in the left eye. His manifest refraction was plano in the right eye and 1.50 -0.75 × 90 in the left eye. IOP measured 19 mm Hg in the right eye and 26 mm Hg in the left eye. Pupil examination revealed a nonreactive pupil in the right eye and a round sluggish pupil in the left eye without an obvious relative afferent pupillary defect. Extraocular motility and confrontational visual fields were full in both eyes. On slitlamp examination, pertinent findings included the following: 1+ corneal guttata without edema in both eyes; anterior chambers were shallow but adequate in both eyes with scattered peripheral anterior synechiae in the right eye and a uniformly shallow but adequate chamber in the left eye; there was no cell or flare in either eye. Iris findings included a surgical pupil with a fibrotic pupillary membrane, laser iridoplasty scars with scattered temporal transillumination defects (TIDs) in the right eye, and 2.5 clock hours of TIDs and a patent peripheral iridotomy at 1 o'clock in the left eye; lens examination revealed centered posterior chamber IOLs with open posterior capsules in both eyes and lens pitting in the left eye. Pertinent findings on dilated fundus examination included a cup-to-disc ratio of 0.3 in both eyes with good neuroretinal rims and macular examination revealed medium-sized drusen with pigment clumping in both eyes and no active choroidal neovascular membranes. The remainder of the examination was unremarkable. What is the etiology of this myopic surprise? What diagnostic testing will help confirm the diagnosis and what are the best management options for this patient?

One-year outcomes of stand-alone ab externo SIBS microshunt implantation in refractory glaucoma.

BACKGROUND/AIMS: Determine the efficacy of stand-alone implantation of the ab externo SIBS or poly(styrene-block-isobutylene-block-styrene) microshunt with mitomycin C in glaucomatous eyes, refractory to previous subconjunctival filtering surgery, over 1 year of follow-up. METHODS: Consecutive retrospective cohort of patients with intraocular pressure (IOP) above target and previous subconjunctival filtering surgery, who received the microshunt between July 2015 and April 2019. Primary outcome was a complete success, with failure defined as IOP <6 mm Hg with vision loss, >17 mm Hg or <20% reduction in IOP without medications. Secondary outcomes included thresholds of 6 to 14 mm Hg and 6 to 21 mm Hg for both complete (no medications) and qualified (with medications) success as well as qualified success for thresholds of 6 to 17 mm Hg. Risk factors for failure, IOP, medications and complications were also assessed. RESULTS: 85 eyes of 79 patients with a preoperative median IOP of 22.0 mm Hg (IQR 18.0-29.0) on four (IQR 3-4) medications were included. Postoperative median IOP was 13.0 mm Hg (IQR 10.0-17.0) on zero (IQR 0-2) medication at 1 year. 61.0% achieved complete success and 79.7% achieved qualified success. Mild-to-moderate disease was associated with failure (adjusted HR 2.37; 95% CI 1.23 to 4.59). Needling was performed in 11.8%, and 8.2% underwent anterior chamber reformation. Complications were transient, consisting of hyphaema, choroidal detachment and hypotony maculopathy, with 7.1% of patients undergoing reoperation. CONCLUSIONS: In a group of high-risk eyes that had already failed at least one subconjunctival filtering surgery, the SIBS microshunt demonstrates reasonable surgical success over 1-year follow-up, with relatively few complications.

Two-year outcomes of the MINIject drainage system for uncontrolled glaucoma from the STAR-I first-in-human trial.

BACKGROUND/AIMS: The current study evaluates the efficacy and safety of the stand-alone implantation of the MINIject (iSTAR Medical, Wavre, Belgium) supraciliary, microinvasive glaucoma drainage device in patients with medically uncontrolled open-angle glaucoma. METHODS: This prospective, multicentre, first-in-human, single-arm interventional study evaluated stand-alone, ab interno implantation in 25 patients of a 5 mm long uveoscleral device made of STAR biocompatible material, which is a soft, microporous, flexible silicone. The primary outcome was the reduction of intraocular pressure (IOP) at 6 months compared with baseline, and follow-up continued until 2 years for 21 patients. Secondary outcomes included success defined as diurnal IOP of ≤21 mmHg and >5 mmHg with an IOP reduction of 20% without (complete) or with/without (qualified) glaucoma medication. RESULTS: Mean baseline IOP was 23.2±2.9 mmHg on 2.0±1.1 glaucoma medication ingredients and decreased to 13.8±3.5 mmHg (-40.7% reduction) on 1.0±1.3 medications 2 years after implantation. Complete success was achieved in 47.6% of patients (10/21) and qualified success in 100% of patients (21/21) at the 2-year follow-up. All patients achieved a 20% IOP reduction with 48% of patients medication-free. No serious ocular adverse events or additional glaucoma surgery were reported. Mean central endothelial cell density (ECD) mildly decreased from 2411 cells/mm2 (n=26) to 2341 cells/mm2 (n=21) at 24 months, which represents a 5% decrease for matched eyes. No patient had a ≥30% decrease in central ECD. CONCLUSION: This first-in-human study on the stand-alone implantation of the MINIject supraciliary drainage system shows promising IOP-lowering results and medication reduction over 24 months with few adverse events. TRIAL REGISTRATION NUMBER: NCT03193736.

Intraocular Lens Complications: Decentration, Uveitis-Glaucoma-Hyphema Syndrome, Opacification, and Refractive Surprises.

As cataract surgery has evolved, intraocular lens (IOL) complications are rare. The purpose of this review was to report the incidence, diagnosis, and management of IOL decentrations, uveitis-glaucoma-hyphema (UGH) syndrome, IOL opacifications, and refractive surprises. Literature review was performed by searching PubMed, MEDLINE, EMBASE, and the Cochrane Controlled Trial Database and the reference lists of original studies as well as reviews. Intraocular lens decentrations and dislocations can appear at any time, particularly in patients with predisposing factors such as pseudoexfoliation, prior vitreoretinal surgery, or trauma. Recognizing when they require surgical intervention for UGH or to improve visual function is critical in limiting long-term sequela. Intraocular lens opacifications such as glistenings rarely require intervention, but others, such as subsurface nanoglistenings, calcifications, or discolorations, may require IOL exchange. Finally, despite our best efforts to enhance measurements and IOL calculations, refractive surprises still occur. Intraocular lens complications are uncommon with modern cataract surgery. A number of these complications require proper identification and care to optimize patient outcomes.

XEN® Gel Stent: A Comprehensive Review on Its Use as a Treatment Option for Refractory Glaucoma.

The XEN Gel Microstent is a subconjunctival microinvasive glaucoma surgical device developed with the aim of improving the predictability and safety profile of bleb-forming glaucoma surgical procedures. The stent is a hydrophilic tube composed of a porcine gel cross-linked with glutaraldehyde with good stability and biocompatibility with minimal tissue reaction. This device has demonstrated promising outcomes with fewer risks compared to traditional surgeries. The aim of the review is to present early studies on different designs of the XEN Gel Stent, to summarize different surgical techniques of implantation and to analyze more comprehensively the results, complications and rates of needling of the commercially available device (Xen 45). The review will address separately special cases (PXG, UVG, ICE, congenital glaucoma) and describe small series and case reports.

Current review of Excimer laser Trabeculostomy.

BACKGROUND: Excimer laser trabeculostomy (ELT) is a microinvasive glaucoma surgery (MIGS) that creates multiple laser channels through the trabecular meshwork using a cold laser system, which minimizes tissue fibrosis and aids in bypassing the main area of resistance to aqueous outflow. The purpose of this review is to evaluate the current body of evidence surrounding ELT in terms of efficacy and review the safety profile of the procedure. MAIN TEXT: Studies screened had to show clear inclusion and exclusion criteria as well as well-defined outcome measures. PubMed, MEDLINE, EMBASE and the Cochrane Controlled Trial Database were searched. Preferred Reporting Items of Systematic Reviews (PRISMA) guidelines were used to assess for study quality and for any bias. Sixty-four articles were initially identified with 18 meeting preliminary screening criteria. Ultimately, 8 studies met inclusion criteria and 2 additional non-referenced publications were also included: 1 randomized control trial, 4 prospective case series and 5 retrospective studies. Overall studies showed moderate intraocular pressure (IOP) lowering of between 20% and 40% from baseline without medication washout and mostly a decrease in glaucoma medications with few complications. CONCLUSION: Current literature shows a significant IOP-lowering effect of ELT with a favorable safety-profile in standalone cases or combined with cataract surgery. Limitations to these studies are the lack of controls and washout IOP. Overall, ELT is an attractive MIGS option that does not require any residual device remaining in the angle.

Intermediate Outcomes of a Novel Standalone Ab Externo SIBS Microshunt With Mitomycin C.

PURPOSE: To determine the efficacy, risk factors for failure, and adverse events of a standalone novel ab externo SIBS microshunt with mitomycin C (MMC) during 1-year follow-up. DESIGN: Retrospective, interventional case series. SUBJECTS: Glaucomatous eyes with an intraocular pressure (IOP) above target and/or progressing on maximally tolerated medical therapy. METHODS: Consecutive patients with open-angle glaucoma (OAG) and no previous filtering surgery received an ab externo SIBS microshunt with MMC from July 2015 to November 2017. Main outcome measures were proportion of eyes at 1-year with (1) no 2 consecutive IOP readings >17 mm Hg or clinical hypotony without (complete) or with glaucoma medications (qualified); and (2) at least a 20% reduction from decision IOP. Secondary outcomes included upper IOP thresholds of 14 mm Hg and 21 mm Hg with and without a 20% IOP reduction from baseline, median IOP, medications, risk factors for failure, interventions, complications, and reoperations. RESULTS: A total of 164 eyes in 132 patients were included. Complete success was achieved in 76.9% of eyes, qualified success in 92.5%. Complete success was 75.6% for an upper IOP cut-off of 14 mm Hg and 76.9% for 21 mm Hg, and qualified success was 91.9% and 92.5%. MMC dose of 0.2 vs 0.4-0.5 mg/mL (hazard ratio [HR] 2.51; 95% CI 1.12-5.65) and primary open-angle glaucoma vs secondary open-angle glaucoma (SOAG) (HR 2.51; 95% CI 1.01-6.23) represented the only risk factors for failure in multivariable analysis. Needling was performed in 8.5% of eyes. Two eyes received surgical revision, and 1 a reoperation. CONCLUSIONS: One-year results of the ab externo SIBS microshunt demonstrated promising rates of qualified and complete success, decreased drop use, few complications, and infrequent postoperative interventions.

Usefulness of Prestorage Corneal Swab Culture in the Prevention of Contaminated Corneal Tissue in Corneal Transplantation.

PURPOSE: To assess the efficacy of the prestorage corneal swab (PCS) culture to screen for corneal graft contamination after storage in Optisol-GS. METHODS: A retrospective analysis of all PCS cultures was performed at the Eye Bank of Québec in Hôpital Maisonneuve-Rosemont from September 2013 to June 2016. Whole corneal culture was performed on rejected grafts because of a positive PCS, and a contamination rate was calculated. In addition, contamination rates of corneoscleral rims were compared between corneas tested with PCS and those of imported corneas which did not have PCS. RESULTS: Among the 1966 PCS cultures performed, 814 (41.4%) were positive for growth. Pathogenic bacteria were present in 144 (7.3%) corneas, including Staphylococcus aureus (n = 96, 11.8% of all positive cultures), Enterobacteriaceae (n = 14, 1.7%), and Pseudomonas aeruginosa (n = 6, 0.7%). After preservation in Optisol-GS, only 7 (6.9%) corneas remained contaminated (95% confidence interval 5.1-9.3). The sensitivity of the PCS culture was 87.5% (95% confidence interval 47.4-99.7). There was no significant difference in corneoscleral rim contamination between corneas tested with PCS (1/388; 0.2%) compared with imported, nonswabbed corneas (3/214; 1.4%) (P = 0.131). Therefore, the cost to recover the loss of tissue rejected because of false-positive PCS by purchasing corneal tissue was calculated to be $142,884 (CAD) per year. CONCLUSIONS: Despite the high sensitivity of PCS cultures, there was no significant reduction of infection after corneal transplantation using this technique. In consequence, 93% of the corneas possibly suitable for transplantation were rejected. This suggests that the PCS culture alone is a poor test for detecting clinically relevant corneal contamination.

No Light Perception Outcomes Following Boston Keratoprosthesis Type 1 Surgery.

PURPOSE: To determine the incidence rate, principal causes, and clinical course of eyes developing no light perception (NLP) visual acuity (VA) following Boston Keratoprosthesis (B-KPro) type 1 surgery. Secondary objectives include determining the incidence rate, relative risk (RR), and survival probability with respect to NLP outcomes among eyes with congenital aniridia. DESIGN: Retrospective, interventional case series. SUBJECTS: All patients undergoing B-KPro type 1 surgery between October 2008 and June 2016 by a single surgeon at CHUM - Hôpital Notre-Dame. METHODS: Records of patients having undergone B-KPro implantation were reviewed. Eyes with a final outcome of NLP were further reviewed to determine best recorded postoperative VA, time to NLP onset, clinical course, and principal cause. Descriptive statistics, incidence rates, Kaplan-Meier survival curves, and the RR of NLP outcomes among eyes with aniridia were determined. Statistical significance was defined as P < .05. RESULTS: Records of 119 patients were included, with an average follow-up of 49.1 ± 26.8 months postoperatively. Nineteen eyes had a final outcome of NLP, representing 16.0%. The incidence rate of NLP was 0.04 cases per eye-year of follow-up. The most common principal causes were inoperable retinal detachment (n = 7, 36.8%), terminal glaucoma (n = 6, 31.6%), and carrier graft melt-related complications (n = 5, 26.3%). The RR of developing NLP among eyes with aniridia was 3.04 (P = .01). CONCLUSIONS: No light perception is a devastating but uncommon outcome of B-KPro surgery. Patients with aniridia seem to be at increased risk. In spite of all available medical and surgical interventions, some eyes may still suffer this outcome.

Alternatives to eye bank native tissue for corneal stromal replacement.

Corneal blindness is a major cause of blindness in the world and corneal transplantation is the only widely accepted treatment to restore sight in these eyes. However, it is becoming increasingly difficult for eye banks to meet the increasing demand for transplantable tissue, which is in part due to population aging. Donor tissue shortage is therefore a growing concern globally and there is a need for alternatives to human donor corneas. Biosynthetic corneal substitutes offer several significant advantages over native corneas: Large-scale production offers a powerful potential solution to the severe shortage of human donor corneas worldwide; Good manufacturing practices ensure sterility and quality control; Acellular corneal substitutes circumvent immune rejection induced by allogeneic cells; Optical and biomechanical properties of the implants can be adapted to the clinical need; and finally these corneal substitutes could benefit from new advances in biomaterials science, such as surface coating, functionalization and nanoparticles. This review highlights critical contributions from laboratories working on corneal stromal substitutes. It focuses on synthetic inert prostheses (keratoprostheses), acellular scaffolds with and without enhancement of endogenous regeneration, and cell-based replacements. Accent is put on the physical properties and biocompatibility of these biomaterials, on the functional and clinical outcome once transplanted in vivo in animal or human eyes, as well as on the main challenges of corneal stromal replacement. Regulatory and economic aspects are also discussed. All of these perspectives combined highlight the founding principles of the clinical application of corneal stromal replacement, a concept that has now become reality.

Corneal Shape, Volume, and Interocular Symmetry: Parameters to Optimize the Design of Biosynthetic Corneal Substitutes.

PURPOSE: To characterize the three-dimensional (3D) shape, volume distribution, and mirror symmetry of the right and left corneas at the scale of a large population, based on the integrated analysis of 3D corneal shape average maps and topography parameters. METHODS: A total of 7670 Orbscan II corneal topographies from 3835 consenting subjects with no history of ocular disease were studied. Average topography maps were created using the right and left corneal topographies of all subjects. To quantify symmetry, left eye topographies were flipped horizontally into "right eye" topographies and statistics maps were generated, including difference and intraclass correlation coefficient (ICC) maps. RESULTS: The standard deviation of the anterior and posterior average elevation maps in the 3-mm radius central zone of the right and left corneas ranged within ± 8 µm and ± 44 µm, respectively. The ICC maps showed almost perfect interocular agreement for anterior elevation, posterior elevation, and pachymetry (all ICCs > 0.96). All studied shape parameters also showed excellent agreement (ICCs ≥ 0.80). Mirror symmetry was not affected by age, sex, or spherical equivalent. We also showed that this horizontal reflection (flip) of the right and left corneal shapes could not be replaced by a simple rotation. CONCLUSIONS: These results indicate that in normal eyes, the anterior elevation, posterior elevation, and pachymetry of the right and left corneas show remarkable symmetry. This comprehensive analysis was achieved with the purpose of guiding the development of future biosynthetic corneal substitutes.