Competing theories of cataractogenesis after pars plana vitrectomy and the nutrient theory of cataractogenesis: a function of altered aqueous fluid dynamics

Metabolic characterization of human intraocular fluid in patients with pathological myopia

Pathological myopia (PM) and its associated complications can lead to permanent vision loss. However, the cellular mechanisms underlying PM development remain unclear. To identify the metabolic alterations that may contribute to the pathophysiology of PM, we performed non-targeted metabolomics analysis using ultra-high-performance liquid chromatography with tandem mass spectrometry in age- and sex-matched patients with PM (n = 30) and individuals without myopia as controls (n = 30). Targeted metabolomics and insulin microarray were used to validate the results. We identified 508 metabolites in the aqueous humour (AH) and 601 in the vitreous humour (VH). Statistical evaluation revealed that 104 metabolites in AH and 114 metabolites in VH were significantly different between the two groups (variable important for the projection >1, fold change >1.5, or < 0.667, and P < 0.05). The four metabolic pathways enriched in both AH and VH identified to be associated with PM were: bile secretion, insulin secretion, thyroid hormone synthesis, and cGMP-PKG signaling pathway. The concentration of 10 amino acids was significantly higher in the PM than in the controls. Insulin microarray analysis showed that insulin, insulin-like growth factor 2 (IGF-2), IGF-2R, insulin-like growth factor binding protein 1 (IGFBP-1), IGFBP-2, IGFBP-3, IGFBP-4, and IGFBP-6 levels were significantly higher in PM patients compared to that in the controls. Thus, this study identified potential metabolite biomarkers for PM and provided novel insights into the mechanisms underlying this disorder.

The Postvitrectomy Cataract

To review the recent literature regarding risk factors for cataract formation after vitrectomy, the challenges and management strategies for anterior segment surgeons when facing post-vitrectomy cataract surgery, and the visual outcomes of patients undergoing post-vitrectomy cataract surgery. Cataract surgery after vitrectomy can be safely performed to significantly improve the visual outcome in most post-vitrectomy patients, although final visual acuity is primarily limited by the patient’s underlying vitreoretinal pathology.

Predicting speed of progression of lens opacification after pars plana vitrectomy with silicone oil

Purpose

An increasing number of posterior segment disorders is routinely managed with pars plana vitrectomy (PPV). In older, phakic patients cataract formation is expected within the first two years after surgery. For younger patients its progression is individually fluctuating. This study uses an objective quantitative measurement for lens-status-monitoring after PPV with silicone oil to derive predictions for progression and severity of post-operative lens opacification evaluated in patients with rhegmatogenous retinal detachment (RRD).

Methods

Data acquisition was performed prospectively between March 2018 and March 2021. PentacamHR® Nucleus Staging mode (PNS) was used to objectively gather data about nuclear cataracts after PPV at different time points. Data was grouped into training and test sets for a mathematical prediction model. Via backward variable selection method a mathematical formula was set up by means of which predictions about lens densitometry (LD) can be calculated.

Results

20 males [58.8%] and 14 females [41.2%] matched the inclusion criteria (mean age 50.6 years [23–75; ±12.3]). Average follow-up was 8.1 months (3,4–17.4; ±3.4). Mean baseline LD of the treated and fellow eye before surgery was 11.1% (7.7%-17.6%; ±2.0) and 11.2% (7.7%-14.8%; ±1.5), respectively. Predicted LD values by the model for five pre-selected patients closely match the observed data with an average deviation of 1.06%.

Conclusions

Using an objective parameter like LD delivered by the PentacamHR® PNS mode additionally to the patient’s age allows us to make an individual prediction for any time after PPV with silicone oil due to RRD for all ages. The accuracy of the model was stronger influenced by baseline LD as cofactor in the equation than patient’s age. The application for the prediction lens opacification [which can be accessed for free under the following link (https://statisticarium.com/apps/sample-apps/LensDensityOil/)] can help vitreoretinal surgeons for patient consultation on the possibility to combine PPV with cataract surgery.

Scleral Buckling Alone or in Combination with Pars Plana Vitrectomy for Rhegmatogenous Retinal Detachment Repair: A Meta-Analysis of 7212 Eyes

PURPOSE

The efficacy and safety of scleral buckling (SB) versus combination SB and pars plana vitrectomy (SB+PPV) for rhegmatogenous retinal detachment (RRD) repair remains unclear.

METHODS

A systematic review and meta-analysis was conducted to identify comparative studies published from Jan 2000-Jun 2021 that reported on the efficacy and/or safety following SB and SB+PPV for RRD repair. Final best-corrected visual acuity (BCVA) represented the primary endpoint, while reattachment rates and ocular adverse events were secondary endpoints. A random-effects meta-analysis was performed, and 95% confidence intervals were calculated.

RESULTS

Across 18 studies, 3912 SB and 3300 SB+PPV eyes were included. Final BCVA was non-significantly different between SB and SB+PPV (20/38 vs. 20/66 Snellen; WMD=-0.11 LogMAR; 95%CI [-0.29,0.07]; P=0.23). Primary reattachment rate was similar between procedures (P=0.74); however, SB alone achieved a significantly higher final reattachment rate (97.40% vs. 93.86%; RR=1.03; 95%CI [1.00,1.06]; P=0.04). Compared to SB+PPV, SB alone had a significantly lower risk of postoperative macular edema (RR=0.69; 95%CI [0.47,1.00]; P=0.05) and cataract formation (RR=0.34; 95%CI [0.12,0.96]; P=0.04). The incidence of macular hole, epiretinal membrane, residual subretinal fluid, proliferative vitreoretinopathy, elevated intraocular pressure, and extraocular muscle dysfunction were similar between SB and SB+PPV.

CONCLUSIONS

There was no significant difference in final BCVA between SB+PPV and SB alone in RRD. SB alone offers a slightly higher final reattachment rate along with a reduced risk of macular edema and cataract. Primary reattachment rate and the incidence of other complications were similar between the two procedures.

Cataract Following Pars Plana Vitrectomy: A Review

Introduction: The indications for pars plana vitrectomy (PPV) have increased over the years. The vitreous is no longer considered an inert ocular structure and it is well known that its removal has anatomical and physiological consequences. The vitreous is no longer considered an inert ocular structure. The vitreous plays a key role as an intraocular physiologic oxygen regulator. In order to maintain its transparency, the crystalline lens needs protection from an excessive oxygen exposure. PPV leads to progression of nuclear sclerosis in most eyes.Methods: A systematic review of the literature was conducted using Embase and Medline databases. Articles studying the physiology, pathogenesis and surgical treatment of cataract after PPV were included in this review.Results: The pathogenesis of cataract formation after PPV remains unclear. Predisposing factors include advanced patient age, preexisting nuclear sclerosis, light toxicity, intraoperative oxidation of lens proteins, use of silicone oil or intravitreal gas, mechanical trauma and the duration of exposure to an irrigating solution.Conclusion: Cataract surgery in vitrectomized eyes presents with more technical difficulties, is more challenging and often has a higher risk of intraoperative and postoperative complications than in non vitrectomized eyes. There is no standardized technique or management in these cases; therefore, it requires more precautions during surgery.

Management of vitreous floaters: an international survey the European VitreoRetinal Society Floaters study report

BACKGROUND/OBJECTIVES

To evaluate the efficacy and safety of pars plana vitrectomy for symptomatic floaters.

SUBJECTS/METHODS

Forty-eight vitreoretinal surgeons from 16 countries provided information on 581 eyes who underwent vitrectomy for floaters in this retrospective survey study conducted by European VitreoRetinal Society. Percentage symptomatic improvement, incidence of retinal tears/detachment and post-vitrectomy cataract surgery, and the factors associated with satisfaction and complications were investigated.

RESULTS

Ninety-two percent were satisfied with the results, with 86.3% reporting complete resolution of daily-life symptoms. Overall satisfaction was lower in patients with smaller vitreous opacities at presentation (OR:0.4). Iatrogenic retinal breaks occurred in 29 eyes (5%). Core vitrectomy and cut rates of 1500-4000 or >4000 cuts/min were associated with lower risk of retinal breaks than complete vitrectomy (OR:0.05) and cut rates < 1500 cuts/min (OR: 0.03, 0.12, respectively). Fourteen eyes (2.4%) developed retinal detachment at a median of 3 months; and 84 (48.6%) developed cataract at a median of 16 months post-vitrectomy.

CONCLUSIONS

Pars plana vitrectomy resulted in high patient satisfaction with relatively low rate of severe complications in a large group of patients. The procedure may be safer when core vitrectomy and cut rates > 1500 cuts/min are favoured. Proper patient selection and informed consent are the most important aspects of surgery.

Prospective Cohort Study on Refractive Changes after Trabeculectomy

We prospectively evaluated refractive changes in the eyes of 97 patients who underwent trabeculectomy at Fukui University Hospital, Fukui, Japan. The primary outcome measure was the refractive change after trabeculectomy. Secondary outcome measures included postoperative complications and prognostic factors for refractive change. We observed a progressive and significant mean refractive myopic shift of −0.80 D at 12 months after surgery. In phakic eyes, the mean myopic refractive shifts progressed significantly by −0.46 D at 3 months after surgery (P=0.003), by −0.52 D at 6 months (P=0.012), and by −1.31 D at 12 months (P < 0.001). In the pseudophakic eyes, we found no significant refraction progression at any of the postsurgery follow-up visits. Our multivariable analyses showed that lens nuclear color grade change was a significant prognostic factor for refractive myopic progression (P < 0.001). Trabeculectomy causes refractive myopic progression in phakic eyes. Nuclear sclerotic cataract progression is associated with refractive myopic shift after trabeculectomy. This trail is registered with UMIN000007813.

Integrated Tear Proteome and Metabolome Reveal Panels of Inflammatory-Related Molecules via Key Regulatory Pathways in Dry Eye Syndrome

Dry eye syndrome (DES) is a growing public health concern with a high global prevalence; however, the fundamental processes involved in its pathogenic mechanisms remain poorly understood. In the present study, we applied nanoscale liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (nanoLC/Q-TOF-MS/MS) and ultraperformance LC/Q-TOF-MS/MS technologies on tear samples obtained from 18 dry eye patients and 19 healthy controls for integrated proteomic and metabolomic analyses. Overall, 1031 tear proteins were detected, while 190 proteins were determined to be significantly expressed in dry eye patients. Further functional analysis suggested that various biological processes were highly expressed and involved in the pathogenesis of DES, especially immune and inflammatory processes. In total, 156 named metabolites were identified, among which 34 were found to be significantly changed in dry eye patients. The results highlighted the key elements, especially inflammatory-related proteins and metabolites that played important roles in the development of DES. Further, the regulatory roles of primary pathways, including complement and coagulation cascades, glycolysis/gluconeogenesis, and amino acid metabolism, were also identified as processes involved in DES. Collectively, our work not only provided insight into the potential biomarkers of DES for diagnostic and prognostic purposes but extended our knowledge of the physiopathology of this syndrome.

Metabolic characterization of human aqueous humor in the cataract progression after pars plana vitrectomy

BACKGROUND

While pars plana vitrectomy (PPV) has become the third most commonly performed surgery in the world, it can also induce multiple post complications easily. Among them, cataract progression is the most frequent one that can lead to blindness eventually.

METHODS

To understand the underlying mechanisms of post PPV cataract progression, we performed comprehensive metabolic characterization of aqueous humor (AH) samples from 20 cataract patients (10 post PPV complication and 10 none PPV cataract) by a non-targeted metabolomic analysis using gas chromatography combined with time-of-flight mass spectrometer (GC/TOF MS).

RESULTS

A total of 263 metabolites were identified and eight of them are determined to be significantly different (VIP ≥ 1 and p ≤ 0.05) between post PPV group and none PPV control group. The significantly changed metabolites included glutaric acid and pelargonic acid that play key roles in the regulation of oxidative stress and inflammatory responses. Furthermore, we constructed a metabolic regulatory network in each group based on metabolite-metabolite correlations, which reveals key metabolic pathways and regulatory elements including amino acids and lipids metabolisms that are related to cataract progression.

CONCLUSIONS

Altogether, this work discovered some potential metabolite biomarkers for post PPV cataract diagnostics, as well as casted some novel insights into the underlying mechanisms of cataract progression after PPV.

Changes of Accommodative Power in Vitrectomized Eyes with Crystalline Lenses

PURPOSE

To evaluate changes of accommodative power in phakic eyes after uneventful pars plana vitrectomy (PPV) in patients aged younger than 45 years without presbyopia.

METHODS

We investigated patients aged younger than 45 years who underwent PPV without crystalline lens extraction because of vitreoretinal disorders. Twelve weeks after vitrectomy, the near point of accommodation, high-frequency component of accommodative microfluctuation, axial length, and anterior chamber depth of vitrectomized and contralateral nonvitrectomized eyes were examined.

RESULTS

Ten eyes of 10 patients were included. The average patient age was 39.8 (±4.3) years. None experienced cataract progression in the vitrectomized eye up to 12 weeks after surgery. Near point of accommodation was significantly lower in the vitrectomized eye than in the opposite eye at 12 weeks after vitrectomy (5.23 [±1.39] diopters vs. 5.91 [±1.83] diopters, p < 0.001). The high-frequency components in the vitrectomized eyes were significantly greater than those in the contralateral eyes (p = 0.01). However, anterior chamber depth and axial length were similar in value to the preoperative observations.

CONCLUSIONS

Uneventful PPV in relatively young patients without presbyopia reduced accommodative power during the early postoperative period with no cataract progression.

Vitreous humor in the pathologic scope: insights from proteomic approaches

The vitreous humor (VH) is the largest component of the eye. It is a colorless, gelatinous, highly hydrated matrix that fills the posterior segment of the eye between the lens and retina in vertebrates. In VH, a diversity of proteins that can influence retinal physiology is present, including growth factors, hormones, proteins with transporter activity, and enzymes. More importantly, the protein composition of VH has been described as being altered in a number of disease states. Therefore, attempts aiming at establishing a map of VH proteins and detecting putative biomarkers for ocular illness or protein fluctuations with putative physiologic significance were conducted over the last two decades, using proteomic approaches. Proteomic strategies often involve gel-based or LC techniques as sample fractioning approaches, subsequently coupled with MS procedures. This set of studies resulted in the proteomic characterization of a range of ocular disease samples, with particular incidence on diabetic retinopathy. However, practical therapeutic applications arising from these studies are scarce at the moment. A pertinent example of therapeutic targets arising from VH proteomics has emerged concerning vasoproliferative factors present in the vitreous, which should be involved in neovascularization and subsequent fibrovascular proliferation of the retina, in ocular disease context. Therefore, this review attempts to sum up the information acquired from the proteomic approaches to ocular disease conducted in VH samples, highlighting its clinical potential for disclosing ocular disease mechanisms and engendering pharmacological therapeutic treatments.

Combined 23-gauge vitrectomy and femtosecond laser-assisted cataract surgery

BACKGROUND

The aim of this study was to assess the safety and surgical results of femtosecond laser-assisted phacovitrectomy.

METHODS

A retrospective analysis of the medical records of patients over 50 years of age with vitreoretinal pathology, who had undergone pars plana vitrectomy using 23-gauge instruments and femtosecond laser-assisted cataract surgery and implantation of an intraocular lens, was performed at the Instituto de Microcirugía Ocular between June 2012 and September 2013. The diameter of the anterior capsulorhexis was set at 4.8 mm in cases where a gas tamponade was used and at 5 mm in all other cases. During the pars plana vitrectomy, posterior capsulotomy was performed on all eyes. An assessment was carried out of preoperative characteristics, surgical indications, postoperative results and complications. Only patients with a minimum of 3 months of follow-up were included.

RESULTS

A total of 21 eyes in 21 patients (71.4% women) were treated. Mean age (± SD) was 65.8 ± 6.4 years (range 53-76). The most common indication for surgery was epiretinal membrane (61.9%), followed by vitreous haemorrhage (23.8%) and macular hole (14.3%). The mean preoperative best corrected visual acuity (BCVA) was 0.81 ± 1.01 logMAR and the mean postoperative BCVA was 0.12 ± 0.19 logMAR (p = 0.003). 85.7% of patients improved their visual acuity. The remaining patients maintained their visual acuity. The only intraoperative complication related to femtosecond laser was 1 case of suction loss (4.8%). A patient with rhegmatogenous retinal detachment discovered during surgery required an additional circular scleral procedure and developed synechiaes in the early postoperative period (<1 month). There were no cases of subluxation of the intraocular lens. Mean follow-up was 6 months (range 3-14).

CONCLUSIONS

The application of femtosecond laser in phacovitrectomy is a safe and effective technique that presents advantages compared to conventional techniques in cases of macular pathology and/or vitreous haemorrhage.

Cataract progression in macular hole cases: results with vitrectomy or with observation

PURPOSE

To quantify the difference in progression of nuclear sclerotic cataract using Scheimpflug image analysis in patients with idiopathic full-thickness macular hole who were randomized to have vitrectomy and gas tamponade or to be observed.

SETTING

Moorfields Eye Hospital, London, United Kingdom.

DESIGN

Prospective randomized placebo-controlled masked clinical trial.

METHODS

As part of the Moorfields Macular Hole Study, patients with full-thickness macular hole who were randomized to have vitrectomy and gas tamponade or who were observed were compared. Patients had Scheimpflug image analysis of the crystalline lens to evaluate nuclear sclerosis progression by the single-masked observer at baseline and 3, 6, 9, and 12 months postoperatively.

RESULTS

Ninety-eight patients had sufficient baseline data for analysis. At 3 months and 6 months, vitrectomy patients had significant increases in nuclear density compared with baseline (16.6% and 33.9%, respectively) (both P<.0001). In the observation group, nuclear density increased by 1.4% between baseline and 6 months (P = .92). At 6 months, the increase in nuclear density from baseline was 24 times greater in the surgical group than in the observation group (P<.0001). No correlation between the rate of nuclear sclerosis progression and age or baseline nuclear density was found.

CONCLUSIONS

Rapid nuclear sclerosis progression was quantifiable by Scheimpflug image analysis in patients having surgery for idiopathic full-thickness macular hole.There was no [corrected] evidence of a correlation between age groups and the rate of cataract progression.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Pars plana vitrectomy for primary rhegmatogenous retinal detachment

Pars plana vitrectomy (PPV) is growing in popularity for the treatment of primary rhegmatogenous retinal detachment (RD). PPV achieves favorable anatomic and visual outcomes in a wide variety of patients, especially in pseudophakic RD. A growing number of clinical series, both retrospective and prospective, have demonstrated generally comparable outcomes comparing PPV and scleral buckling (SB) under a variety of circumstances. The Scleral Buckling Versus Primary Vitrectomy in Rhegmatogenous Retinal Detachment (SPR) study is a multicenter, randomized, prospective, controlled clinical trial comparing SB versus PPV. This study should provide useful guidelines in the future. At this time, the choice of SB versus PPV should be based on the characteristics of the RD, the patient as a whole, and the experience and preference of the individual retinal surgeon.

Cochlin in the eye: functional implications

Aqueous humor is actively produced in the ciliary epithelium of the anterior chamber and has important functions for the eye. Under normal physiological conditions, the inflow and outflow of the aqueous humor are tightly regulated, but in the pathologic state this balance is lost. Aqueous outflow involves structures of the anterior chamber and experiences most resistance at the level of the trabecular meshwork (TM) that acts as a filter. The modulation of the TM structure regulates the filter and its mechanism remains poorly understood. Proteomic analyses have identified cochlin, a protein of poorly understood function, in the glaucomatous TM but not in healthy control TM from human cadaver eyes. The presence of cochlin has subsequently been confirmed by Western and immunohistochemical analyses. Functionally, cochlin undergoes multimerization induced by shear stress and other changes in the microenvironment. Cochlin along with mucopolysaccharide deposits has been found in the TM of glaucoma patients and in the inner ear of subjects affected by the hearing disorder DNFA9, a late-onset, progressive disease that also involves alterations in fluid shear regimes. In vitro, cochlin induces aggregation of primary TM cells suggesting a role in cell adhesion, possibly in mechanosensation, and in modulation of the TM filter.

Bimanual microphacoemulsification and Acri.Smart intraocular lens implantation combined with vitreoretinal surgery

PURPOSE

To assess the efficacy and safety of bimanual microphacoemulsification combined with vitrectomy in eyes with clinically evident cataract and vitreoretinal pathology.

SETTING

Institute of Ophthalmology of the University of Modena and Reggio Emilia, Modena, Italy.

METHODS

This prospective case series comprised 19 consecutive patients with clinically significant cataract who were scheduled for vitrectomy. Bimanual microphacoemulsification was performed, and an Acri. Smart 46 S hydrophobic acrylic intraocular lens (IOL) with a 6.0 mm optic (Acri.Tec, Inc.) was implanted in the capsular bag. Immediately after, standard 3-port vitrectomy was performed.

RESULTS

The prevailing vitreoretinal pathology was retinal detachment, with 1 case of macular pucker and 1 case of macular hole. In all cases, the IOL was implanted in the capsular bag. There were no intraoperative complications during the cataract surgery or vitrectomy. Follow-up 1, 15, 30, 90, and 180 days after surgery showed significant visual recovery in all cases. The mean endothelial loss was 10.05%+/-2.01% (SD). In 3 cases that had tamponade with heavy silicone oil, progressive posterior capsule opacification occurred 6 months after surgery.

CONCLUSIONS

Bimanual microphacoemulsification combined with vitrectomy was effective and safe. The microincisions and 19-gauge instruments provided excellent chamber resistance that simplified surgical maneuvers in eyes that might have a distorted fundus reflection and increased zonular laxity. The Acri. Smart 46 S IOL, which can be injected through a 2.0 mm incision, provided good fundus visibility during vitrectomy and good maneuverability up to the extreme periphery without resulting in glare or distracting reflections for the surgeon.

Primary retinal detachment: scleral buckle or pars plana vitrectomy?

PURPOSE OF REVIEW

There remains no consensus among vitreoretinal surgeons regarding the optimal management of primary rhegmatogenous retinal detachment. In this article, fundamental principles are discussed and applied to recent clinical reports.

RECENT FINDINGS

The consensus of the peer-reviewed literature appears to be that scleral buckling and primary pars plana vitrectomy may yield comparable single-operation success rates and visual acuity outcomes for a wide variety of rhegmatogenous retinal detachments.

SUMMARY

No definitive prospective, randomized, multicenter trial compares scleral buckling with pars plana vitrectomy. The upcoming Scleral Buckling versus Primary Vitrectomy in Rhegmatogenous Retinal Detachment study may yield useful information in this regard. Even when this study is completed, the choice of surgical modality is complex and may be individualized for specific patients.