Effects of intraoperative sponge mitomycin C and 5-fluorouracil on scar formation following strabismus surgery in rabbits

Rectus muscle pseudo-adherence syndrome

Purpose

To describe a clinical entity called "rectus muscle pseudo-adherence syndrome" following buckling surgery.

Methods

A retrospective data review was undertaken to analyze the clinical profile of strabismus patients who had developed it following buckling surgery. Between 2017 and 2021, a total of 14 patients were identified. The demography, surgical details, and intraoperative challenges were reviewed.

Results

The average age of the 14 patients was 21.71 ± 5.23 years. The mean pre-op deviation was 42.35 ± 14.35 prism diopters (PD) of exotropia, and the mean post-op deviation was 8.25 ± 4.88 PD of residual exotropia at 26.16 ± 19.53 months follow-up. Intraoperatively, in the absence of a buckle, the thinned-out rectus adhered to the underlying sclera with much denser adhesions along its margins. When there was a buckle, the rectus muscle adhered to the outer surface of the buckle again, but less densely, with marginal union into the surrounding tenons. In both scenarios, due to the absence of protective muscle coverings, the rectus muscles were naturally adsorbed onto the immediately available surface in the presence of active healing by the tenons.

Conclusion

While correcting ocular deviations following buckling surgery, a false sense of an absent, slipped, or thinned-out rectus muscle is very much possible. This is due to active healing of the muscle with the surrounding sclera or the buckle in a single layer of tenons. This is the rectus muscle pseudo-adherence syndrome, where the culprit is the healing process and not the muscle.

Effect of Topical 5-Fluorouracil on Lacrimal Drainage System: Histopathological Evidence From Animal Experiments and Potential Clinical Implications

PURPOSE

The purpose of this study is to investigate the histopathological changes in the lacrimal drainage system of rabbits following the application of 1% topical 5-fluorouracil (5-FU) for 4 weeks.

METHODS

Ten eyes of 10 healthy New Zealand white rabbits were subjected to topical instillation of 1% (10 mg/mL) 5-FU, 1 drop 4 times a day for 4 weeks. Rabbits underwent a detailed ocular examination including eyelids, ocular surface, punctal, peri-punctal changes, and nasolacrimal duct patency at baseline and after 4 weeks of 5-FU. The rabbits were then sacrificed, and the eyelid, conjunctiva, lacrimal gland, and the entire lacrimal drainage system were retrieved for histopathological analysis as per standard protocols.

RESULTS

Clinically demonstrable peripunctal changes and canalicular stenosis were noted in 6 (60%, 6/10) rabbits. Two of these (20%, 2/10) had additional complete regurgitation of clear fluid, indicating a nasolacrimal duct obstruction. The remaining 4 (40%, 4/10) clinically did not demonstrate lacrimal drainage changes and were patent on irrigation. The conjunctiva showed focal loss of goblet cells in several areas. Significant changes were noted in the canalicular, lacrimal sac, and the nasolacrimal duct tissues in the form of epithelial hyperplasia, subepithelial inflammation, edema, dilated and congested vessels, and fibrosis. The lacrimal gland, eyelid tissue (excluding tarsal conjunctiva), and cornea showed no significant histopathological changes.

CONCLUSIONS

Clinical and histopathological changes were noted in the lacrimal drainage system of rabbits subjected to topical 5-FU application. These findings can have potential clinical implications for patients receiving 5-FU therapy.

Comparative Assessment of Short-Term Tendon-Scleral Postoperative Inflammation and α-Smooth Muscle Actin Expression following Oral and Topical Diclofenac Administration for Strabismus Surgery in Rabbits

PURPOSE

Wound healing and fibrosis modulation are considered pivotal for the long-term outcome of strabismus surgery. Nonsteroidal anti-inflammatory drugs, including diclofenac sodium, are inflammation suppressive drugs that may modulate wound healing, including postoperative inflammation. This study aimed to compare the effect of oral and 0.1% topical diclofenac sodium on short-term inflammation and α-smooth muscle actin (α-SMA) expression at the tendon-scleral attachment site following strabismus surgery in an experimental rabbit model.

METHODS

Superior rectus recession was performed in 12 eyes of six New Zealand rabbits. Rabbits were divided into three groups: oral diclofenac 2 × 5 mg/kg for three days (group A), 0.1% diclofenac sodium eye drops 3 times/day for three days (group B), and controls (group C). On postoperative day 14, enucleation was performed. Macroscopic adhesion score, microscopic adhesion score, percentage of postoperative inflammation area (Masson's trichrome staining), and α-SMA (immunohistochemistry staining) were assessed. Data analysis was performed using a semi-quantitative and quantitative assessment with ImageJ. All groups were compared with reciprocal staining intensity (RSI) values to measure α-SMA expression.

RESULTS

All groups showed no difference in macroscopic (p = 0.13) and microscopic adhesion scores (p = 0.28). The percentage of postoperative inflammation area in group B (12.44% (8.63-18.29)) was significantly lower than group A (26.76% (21.38-37.56) p = 0.03) and group C (27.80% (16.42-36.28), p = 0.04). Comparative RSI analysis found that group B had a significantly lower α-SMA expression than group C (174.08 ± 21.78 vs 212.58 ± 12.06, p = 0.04).

CONCLUSION

The results suggest that compared to oral, the administration of topical diclofenac showed a more significant reduction of short-term postoperative inflammation and α-SMA expression at the tendon-scleral attachment site following strabismus surgery.

Molecular mechanisms regulating wound repair: Evidence for paracrine signaling from corneal epithelial cells to fibroblasts and immune cells following transient epithelial cell treatment with Mitomycin C

In this paper, we use RNAseq to identify senescence and phagocytosis as key factors to understanding how mitomyin C (MMC) stimulates regenerative wound repair. We use conditioned media (CM) from untreated (CMC) and MMC treated (CMM) human and mouse corneal epithelial cells to show that corneal epithelial cells indirectly exposed to MMC secrete elevated levels of immunomodulatory proteins including IL-1α and TGFβ1 compared to cells exposed to CMC. These factors increase epithelial and macrophage phagocytosis and promote ECM turnover. IL-1α supplementation can increase phagocytosis in control epithelial cells and attenuate TGFβ1 induced αSMA expression by corneal fibroblasts. Yet, we show that epithelial cell CM contains factors besides IL-1α that regulate phagocytosis and αSMA expression by fibroblasts. Exposure to CMM also impacts the activation of bone marrow derived dendritic cells and their ability to present antigen. These in vitro studies show how a brief exposure to MMC induces corneal epithelial cells to release proteins and other factors that function in a paracrine way to enhance debris removal and enlist resident epithelial and immune cells as well as stromal fibroblasts to support regenerative and not fibrotic wound healing.

Histologic and Immunohistochemical Evaluation of Radiosurgery in Strabismus Surgery in a Rabbit Model

PURPOSE

The aim of this study was to evaluate the use of monopolar radiosurgery (MRS) assisted strabismus surgery and to compare its histologic and immunohistochemical wound healing outcomes with conventional surgery.

MATERIALS AND METHODS

Superior rectus muscle resection was performed on 30 white rabbits with three different surgical muscle cutting techniques: monopolar radiosurgery (MRS group), conventional scissors preceded by bipolar electrocautery (BEC group), and conventional scissors with no cauterization (control group). Degree of tissue injury, bleeding, inflammation, and fibrosis, as well as wound healing rate (CD68+ cell number), were evaluated.

RESULTS

In CS group, hemorrhage scores were significantly higher than those in the other groups (MRS group: Z = 5.182; p < 0.001 and BEC group: Z = 4.463; p < 0.001) and MRS group had lower scores than BEC group; however, the difference was not significant (Z = 1.423; p = 0.211). The tissue injury score in BEC group was higher when compared with MRS, and the difference was statistically significant (p = 0.028). Median inflammation scores at days 1 and 21 were lowest in MRS group, but the difference was not statistically significant among groups (day 1; p = 0.115, day 21; p = 0.095). The median fibrosis score was higher in the control group, when compared with MRS, and the difference was statistically significant (muscle-sclera; p = 0.011 and muscle-conjunctiva: p = 0.003). The macrophage score (number of CD68+ cells) was lowest in CS group; however, the difference was not significant (p = 0.657).

CONCLUSIONS

Monopolar radiosurgery is a novel method for strabismus surgery and provides equivalent hemostasis effects and wound healing properties, compared with conventional methods, and enhances surgeon comfort, as muscle incisions are made in one step with clean surgical area.

Iatrogenic corneal diseases or conditions

Any prescribed or self-administered therapy carries inherent risks of secondary adverse events. While the volume of treatments being administered through healthcare systems has been increasing, scientific advancements in our understanding of the mechanisms of pharmaceutical side effects and complications from procedures now allow us to reduce the risk of non-intentional damage to ocular health. This review summarizes the most common and leading causes of iatrogenic visual impairment, corneal diseases, and conditions that present in a general ophthalmologic practice, including a comprehensive analysis of their pathophysiology and recommendations for management and prophylaxis.Iatrogenic corneal diseases and conditions can arise from topical drugs, contact lens use, eye surgeries and procedures, systemic drugs, non-ophthalmological events, and cosmetic procedures. Topical and systemic drugs may disturb tear film homeostasis or result in ocular surface deposits. The use of ill-fitted contact lenses can trigger eye discomfort and poor hygiene conditions that can predispose to severe infections. Procedures to the eye may result in a variety of anatomical and functional complications that ophthalmologists should be aware of how to avoid or at least be prepared to manage if they occur. Even non-ophthalmological events such as non-invasive ventilation, radiation therapies and, immune-based conditions, or cosmetic procedures such as eyelash growth and fillers, can result in unwanted damage to the ocular surface.

Identification and Correction of Restrictive Strabismus After Pterygium Excision Surgery

PURPOSE

To report the characteristics of patients with restrictive diplopia following pterygium excision and a successful treatment approach for the strabismus.

DESIGN

Retrospective interventional case series.

METHODS

This study was set in a single academic institution and included 15 patients with restrictive diplopia after pterygium excision. Patients with any other reason for strabismus were excluded. Patients were evaluated for deficits with special attention to diplopic measures. The intervention was a combined procedure by a strabismologist and oculoplastic surgeon to correct the diplopia. The primary outcome measurements were subjective and objective improvement of diplopia.

RESULTS

Fifteen patients (mean age = 49 years) who developed diplopia after pterygium excision were included. Mean time to diplopia was 6 months. All patients had limited abduction in the previously operated eye causing esotropia in the abductive field (mean deviation = 18 prism diopters). After intervention, all patients were no longer diplopic in primary gaze. In the abductive field, 11 (73%) patients had residual small angle esotropia (mean = 7 prism diopters) in ipsilateral extreme end-gaze only. Only 2 patients required additional surgical intervention for scar tissue removal. No patients underwent medial rectus recession.

CONCLUSIONS

Restrictive diplopia is a potential complication after pterygium excision, particularly for patients with a history of recurrent pterygia requiring multiple excisions and previous amniotic membrane graft placement with fibrin glue. However, diplopia after pterygium excision in primary position is surgically correctable with scar tissue removal and ocular surface reconstruction, without needing medial rectus recession. Given the high volume of pterygium excision, awareness of postoperative restrictive strabismus and the potential for correction is critical.

Cryopreserved rabbit amniotic membrane alleviated inflammatory response and fibrosis following experimental strabismus surgery in rabbits

We evaluate the ability of cryopreserved rabbit amniotic membrane (AM) transplantation to reduce postoperative inflammation and the extent of fibrosis following experimental strabismus surgery. Ten white rabbits underwent bilateral superior rectus (SR) muscle resection. In the left eye, the resected SR muscle was wrapped with cryopreserved rabbit AM. The right eye underwent SR resection only and served as a control. The eyes were enucleated 4 weeks after strabismus surgery. The degree of postoperative inflammatory infiltration, the extent of fibrosis, and profile of the relative expression of inflammatory mediators in the SR muscle were evaluated and compared between the two groups by histological analysis and real-time polymerase chain reaction (PCR). There were statistically meaningful differences in the degree of postoperative inflammatory infiltration and extent of fibrosis between the eyes treated with cryopreserved rabbit AM after SR resection and those underwent SR resection only. A significant decrease in the expression of inflammatory cytokines [interleukin (IL)-12a, IL-12b, IL-17f, and tumor necrosis factor- alpha (TNF-α)], and a markedly increased expression of anti-inflammatory cytokines (transforming growth factor-beta-1(TGFβ-1) and IL-10) were observed in the eyes treated with cryopreserved rabbit AM. In this study, we demonstrate that cryopreserved rabbit AM is effective in reducing postoperative inflammation and extent of fibrosis in a rabbit model of strabismus surgery. Our results imply that cryopreserved AM allograft has anti-inflammatory and anti-scarring properties that can prevent postoperative adhesions following strabismus surgery.

TFOS DEWS II iatrogenic report

Dry eye can be caused by a variety of iatrogenic interventions. The increasing number of patients looking for eye care or cosmetic procedures involving the eyes, together with a better understanding of the pathophysiological mechanisms of dry eye disease (DED), have led to the need for a specific report about iatrogenic dry eye within the TFOS DEWS II. Topical medications can cause DED due to their allergic, toxic and immuno-inflammatory effects on the ocular surface. Preservatives, such as benzalkonium chloride, may further aggravate DED. A variety of systemic drugs can also induce DED secondary to multiple mechanisms. Moreover, the use of contact lens induces or is associated with DED. However, one of the most emblematic situations is DED caused by surgical procedures such as corneal refractive surgery as in laser-assisted in situ keratomileusis (LASIK) and keratoplasty due to mechanisms intrinsic to the procedure (i.e. corneal nerve cutting) or even by the use of postoperative topical drugs. Cataract surgery, lid surgeries, botulinum toxin application and cosmetic procedures are also considered risk factors to iatrogenic DED, which can cause patient dissatisfaction, visual disturbance and poor surgical outcomes. This report also presents future directions to address iatrogenic DED, including the need for more in-depth epidemiological studies about the risk factors, development of less toxic medications and preservatives, as well as new techniques for less invasive eye surgeries. Novel research into detection of early dry eye prior to surgeries, efforts to establish appropriate therapeutics and a greater attempt to regulate and oversee medications, preservatives and procedures should be considered.

Restrictive problems related to strabismus surgery

Strabismus surgery may be responsible for some restrictions in ocular motility that may cause new problems after surgery. Most of the time these restrictions present as a complex motility problem after surgery that requires further treatment. There may be various reasons that cause motility restriction following strabismus surgery. Those are excessive shortening or inadvertent capture of extraocular muscles, transposition procedures and, the most challenging problem, postoperative scar tissue-adhesion formation. In this review the potential reasons for postoperative restrictive problems, preventive measures and finally the treatment options for such problems are overviewed.

Dried human amniotic membrane does not alleviate inflammation and fibrosis in experimental strabismus surgery

Purpose. The purpose of this study was to evaluate the efficacy of dried human amniotic membrane (AM) in reducing the postoperative inflammatory response and scarring after strabismus surgery. Methods. The inflammatory response at the extraocular muscle reattachment site was analyzed after superior rectus (SR) resection in 12 rabbits. Dried human AM (Ambiodry2) was applied between the resected SR muscle plane and Tenon's capsule of the left eyes of rabbits. As a control, the right eyes of rabbits underwent SR resection only. The surgeon randomly ordered which eye gets operated first during the experiment. Two weeks later, enucleation was performed. Six sagittal sections were made for each eye at the insertion of the SR muscle. The grade of postoperative inflammation and the presence of fibrosis were evaluated in histological examinations. Results. There was no statistically significant difference in the intensity of inflammation and fibrous proliferation between the eyes treated with dried human AM after SR resection and those treated with SR resection only. Conclusions. The use of dried human AM was not effective in controlling the postoperative inflammation and scarring in rabbit eyes after extraocular muscle surgery. However, this may be due to the devitalized dry preparation of human AM (Ambiodry2), which may have lost the expected anti-inflammatory and anti-scarring properties, and further studies on humans may be necessary.

A comparison of the effectiveness of mitomycin C and 5-fluorouracil in the prevention of peridural adhesion after laminectomy

Object

The effectiveness of the topical application of mitomycin C (MMC) or 5-fluorouracil (5FU) in preventing peridural adhesion after laminectomy was compared in this study.

Methods

Laminectomies were performed at L-1 in 30 rats. Cotton pads soaked with 0.1 mg/ml MMC, 25 mg/ml 5FU, or 9 mg/ml saline (control) were applied to the operative sites. To evaluate neurological deficits pre- and postoperatively, somatosensory evoked potentials were monitored and the Basso-Beattie-Bresnahan locomotion test was performed. Four weeks postlaminectomy the rats were killed, and peridural scar adhesion was evaluated histologically. The level of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts were determined. The degree of peridural adhesion was classified according to the Rydell standard.

Results

No obvious adhesion formed in the rats in the MMC group, but severe peridural adhesions were found in those in the 5FU and control groups. The content of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts in the MMC group were significantly lower than those in the 5FU and control groups.

Conclusions

The topical application of MMC rather than 5FU may be a successful method of preventing post-laminectomy peridural adhesions.

The Clinical Applications of Fluorouracil in Ophthalmic Practice

Fluorouracil (5-fluorouracil, 5-FU) is a pyrimidine analogue that was originally known for its widespread use as an anticancer drug. The ability of 5-FU to reduce fibroblastic proliferation and subsequent scarring has made it an important adjunct in ocular and periorbital surgeries. It is used in primary glaucoma filtering surgeries and in reviving failing filtering blebs, in dacryocystorhinostomy, pterygium surgery, and in vitreoretinal surgery to prevent proliferative vitreoretinopathy. In addition, 5-FU is also gaining recognition in the treatment and surgical management of ocular surface malignancies like ocular surface squamous neoplasia; however, the specific action of the drug on highly proliferating cells limits its use in primary acquired melanosis of the conjunctiva. When applied topically, this drug has a low rate of sight-threatening adverse effects, is inexpensive, and is easy to administer, making it an important tool in enhancing the success rate in ophthalmic surgery and in reducing the recurrence of ocular surface neoplasia.