Corneal and conjunctival findings after mitomycin C application in pterygium surgery: an in-vivo confocal microscopy study

Noncontact Conjunctiva: A Better Mitomycin C Application Site for Trabeculectomy

INTRODUCTION

Bleb scarring is the most important complication of trabeculectomy. Changing the application position of mitomycin C (MMC) during trabeculectomy might affect the surgery outcome. Our aim is to compare the effectiveness and safety of intraocular pressure (IOP) lowering in two different application sites of mitomycin in trabeculectomy.

METHODS

This retrospective trial compared the surgical outcomes of 177 eyes that underwent trabeculectomy with adjunctive mitomycin C. In 70 eyes, an MMC-soaked sponge was applied under the scleral flap without touching Tenon's capsule. In 107 eyes, an MMC-soaked sponge was applied under the scleral flap covered by Tenon's capsule. Outcome measures were the IOP, best-corrected visual acuity (BCVA), success rates, and incidence of complications.

RESULTS

Within both groups, a highly significant IOP reduction was seen during follow-up. The effectiveness in reducing IOP and the change in best-corrected visual acuity (BCVA) were similar between the two groups. Thin-walled blebs and postoperative hypotony were seen more often when MMC-soaked sponges were applied under the scleral flap covered by Tenon's capsule (P = 0.008 and P = 0.012, respectively). There was no significant difference in BCVA or other complications in either group.

CONCLUSION

Since the effectiveness of IOP reduction was similar between both groups and with a low incidence of thin-walled blebs and hypotony, the subscleral application without touching Tenon's capsule seems to be the safer application site of MMC during trabeculectomy.

Antigen-presenting cells in ocular surface diseases

PURPOSE

To review the role of antigen-presenting cells (APC) in the pathogenesis of ocular surface diseases (OSD).

METHODS

A thorough literature search was performed in PubMed database. An additional search was made in Google Scholar to complete the collected items.

RESULTS

APCs have the ability to initiate and direct immune responses and are found in most lymphoid and non-lymphoid tissues. APCs continuously sample their environment, present antigens to T cells and co-ordinate immune tolerance and responses. Many different types of APCs have been described and there is growing evidence that these cells are involved in the pathogenesis of OSD. OSD is a complex term for a myriad of disorders that are often characterized by ocular surface inflammation, tear film instability and impairment of vision.

CONCLUSIONS

This review summarizes the current knowledge concerning the immunotopographical distribution of APCs in the normal ocular surface. APCs appear to play a critical role in the pathology of a number of conditions associated with OSD including infectious keratitis, ocular allergy, dry eye disease and pterygium.

The in vitro anti-fibrotic effect of Pirfenidone on human pterygium fibroblasts is associated with down-regulation of autocrine TGF-β and MMP-1

We aimed to investigate the in vitro effect of pirfenidone (PFD) on proliferation, migration and collagen contraction of human pterygium fibroblasts (HPFs). HPFs were obtained from tissue explants during pterygium surgery. After treatment with pirfenidone, the HPFs proliferation was measured by MTT, cell cycle progression measured by flow cytometry, cell migration measured by the scratch assay, and cell contractility evaluated in fibroblast-populated collagen gels. The expression of TGF-β1, TGF-β2, MMP-1 and TIMP-1 were also determined with quantitative PCR, western blot and immunofluorescence staining. Results showed pirfenidone markedly inhibited HPFs proliferation with an IC₅₀ of approximately 0.2 mg/ml. After treatment with 0.2 mg/ml pirfenidone for 24 hours, HPFs were at G0/G1 cell cycle arrest, with significantly reduced cell migration capability and collagen contraction, decreased mRNA and protein expressions of TGF-β1, TGF-β2 and MMP-1, and no alterations of TIMP-1 expression. Thus, we have concluded that pirfenidone at 0.2 mg/ml inhibits proliferation, migration, and collagen contraction of HPFs, which is associated with decreased expression of TGF-β and MMP-1, and pirfenidone might represent a potentially therapeutic agent to prevent the recurrence of pterygium after surgery.

Modulation of Fibroblasts in Conjunctival Wound Healing

Modulating conjunctival wound healing has the potential to improve outcomes after glaucoma filtration surgery and for several ocular disorders, including ocular cicatrial pemphigoid, vernal keratoconjunctivitis, and pterygium. Although anti-inflammatories and antimetabolites have been used with success, these nonspecific agents are not without their complications. The search for novel and more targeted means to control conjunctival fibrosis without such limitations has brought much attention to the regulation of fibroblast proliferation, differentiation, extracellular matrix production, and apoptosis. This review provides an update on where we stand with current antifibrotic agents and outlines the strategies that novel agents use, as they evolve from the bench to the bedside.

Characterization of Goblet Cells in a Pterygium Biopsy Using Laser Scanning Confocal Microscopy and Immunohistochemistry

PURPOSE

To confirm that structures presumed to be GCs observed using laser scanning confocal microscopy (LSCM) are actually GCs.

METHODS

A single tissue sample was obtained from a pterygium that was freshly excised from a 33-year-old male. After viewing what were believed to be GCs in the tissue sample using LSCM, the same sample was observed using laboratory confocal microscopy and immunohistochemistry. GCs were identified by a combination of classic morphologic appearance and the use of immunofluorescence to antibodies for mucin 5AC and cytokeratin-7. The LSCM and immunohistochemistry results were compared.

RESULTS

Using LSCM, GCs were observed between 7 and 41 μm deep, at the level of the superficial basal cells of the tissue sample. GCs were estimated to have a diameter of 35-40 μm near the surface and 20-30 μm in the deeper layers. A small dark dot was visible in some GCs, indicating cell nuclei and/or the opened apical portion of cells representing the site of mucin release. GCs were more reflective and larger than the surrounding cells. Positively stained GCs in immunofluorescence showed a similar distribution pattern to those observed with LSCM. The tissue sample stained intensely for GC-specific mucin type 5AC.

CONCLUSIONS

The pattern of discrete, large reflective cells observed using LSCM are likely to be GCs.

Effects of Mitomycin C in Early Conjunctival Inflammation after Pterygium Surgery

PURPOSE

The purpose of this study was to compare inflammatory events and graft characteristics 1 month and 6 months after conjunctival limbal autograft (CLAU) with and without intraoperative mitomycin C (MMC).

METHODS

This study included 69 eyes of 69 patient's eyes with pterygium. Clinical data concerning patient demography, preoperative examination including pterygium morphology, recurrence clinical assessment, and complications after CLAU with (MMC+) and without (MMC-) intraoperative MMC were all registered at 1 month and 6 months after surgery.

RESULTS

Thirty-five eyes were included in MMC+ and 34 in MMC-. Preoperative data were similar in both groups (Student's t test and Fisher's exact test; p > 0.05). Thirty-four (49.6%) eyes in the whole sample showed at least one inflammatory complication at 1 month after surgery. MMC- group showed a significantly higher number of cases with complications (p < 0.001; Chi² test) (MMC+ 28.5%; MMC- 70.5%). No patients presented clinical recurrence at 1 month after surgery. The examination revealed a higher incidence of clinical hyperemia surrounding the surgical site and graft contraction on the host site on the MMC- group, both with statistical signification (p < 0.001; Chi² test). Although the hemorrhages were less frequent in the MMC- group, there were no significant differences between the two groups (p > 0.05; Chi² test). Pyogenic granuloma developed at the surgical site in three eyes (4.37%), two of those granulomas were at the MMC- group (p > 0.05). Tendency for recurrences was significantly different between both groups (p = 0.0001; Fisher's exact test) at the end of 6 months. Thirteen (38%) eyes showed recurrence in MMC- and no cases were displayed in MMC+. Presence of at least 1 inflammatory event was only seen in 16 (23%) cases, all of them in MMC-. Specifically, 15 (44%) eyes showed hyperemia and one (3%) eye presented conjunctival hemorrhages. No new cases of pyogenic granuloma or graft contraction were seen at this time point in both groups. Hyperemia was the only specific event with significant differences between MMC- and MMC+ (p = 0.0001; Fisher's exact test) at 6 months after surgery.

CONCLUSION

The eyes receiving intraoperative MMC after CLAU seem to present less hyperemia and graft contraction after surgery than those that did not receive MMC as an adjuvant factor. Intraoperative MMC could be associated with a lower recurrence rates.

Prophylactic removal and microbiological evaluation of calcified plaques after pterygium surgery

PURPOSE

The aim of this study was to investigate microbiological characteristics of prophylactically removed calcified plaques developed after pterygium excision, and to evaluate risk factors for the growth of microorganisms.

METHODS

Only exposed calcified plaques developed at the same site of previous pterygium excision were prospectively removed in 15 eyes of 14 patients. Plaques were completely removed, divided into small pieces and evaluated for microbiological identification. Underlying scleral defects were reconstructed using a conjunctival autograft, amniotic membranes and scleral patch grafts according to the size and depth of the defects. Based on the results of microbiologic cultures, eyes were divided into two groups and risk factors for microbial growth were analyzed.

RESULTS

At surgery, the mean age of the patients was 71.2 ± 5.8 years and 71.4 % were females. The mean time interval between pterygium excision and calcified plaque removal was 19.3 ± 13.8 years. Six of 15 (40 %) removed plaques showed bacterial growth, and Stenotrophomonas maltophilia was the most frequently isolated microorganism. The size of calcified plaques was the only risk factor for culture-positive results (p = 0.045). Underlying scleral defects were successfully repaired without any serious complication.

CONCLUSIONS

Microorganisms can be isolated from calcified plaques developed at the site of previous pterygium excision, and the size of plaques is the only risk factor for culture-positive results. To remove potential source of infection, prophylactic removal of calcified plaques and scleral surface reconstruction should be considered, especially when the plaques are exposed and large.

Conjunctival Short-term Evolution after Pterygium Excision

PURPOSE

To analyze conjunctival cytological features 1 month after pterygium excision using limbo-conjunctival autograft (LCA) with and without intraoperative mitomycin C and to assess tissue short-term evolution in both situations.

METHODS

Fifty-nine primary nasal pterygia from 59 patients were excised with LCA. Twenty-nine were treated with intraoperative mitomycin C 0.02% (MMC+) and 30 were treated without it (MMC-). Impression cytology was performed in nasal and temporal conjunctiva before and 1 month after the excision. Goblet cell density (GCD) and nucleus-to-cytoplasm nongoblet epithelial cell ratio were quantified.

RESULTS

Surgical strategy comparisons (intergroup comparisons): All the preoperative data were, in mean, within the reference range, except for a slight goblet cell hyperplasia in the area of the lesion in MMC+ but no significant differences were found between the groups (p = 0.079 for GCD and p = 0.245 for nucleus-to-cytoplasm ratio; analysis of variance). Clinically relevant differences after surgery were only shown in nasal GCD that was significantly lower in MMC+ than in MMC- (p = 0.000; analysis of variance), with the mean value in MMC+ slightly below normal values whereas that in MMC- remained normal. Tissue evolution (intragroup comparisons): No clinically relevant changes were found in MMC-. Data from MMC+ displayed no changes 1 month after surgery, except for nasal GCD that showed a significant reduction (p = 0.000; paired t test). Nevertheless, this GCD decrease was more modest than that previously described using mitomycin C without autograft, because in the present study, nasal GCD was not lower but similar to postoperative temporal data of the same eye (p = 0.164; paired t test).

CONCLUSIONS

Limbo-conjunctival autograft is a good technique for conjunctiva early recovery. When mitomycin C was added, the GCD reduction was lower than described using other surgical techniques. Mitomycin C, in optimal concentration and exposure, associated with LCA could be a good clinical option to minimize pterygium recurrence.

Conditional knockout of CTGF affects corneal wound healing

PURPOSE

This study aimed to elucidate the role of connective tissue growth factor (CTGF) in healthy eyes and wounded corneas of mice and rabbits. Conditional knockout mice were used to determine the role of CTGF in corneal healing.

METHODS

CTGF expression was determined using transgenic mice carrying CTGF promoter driven-eGFP, quantitative RT-PCR, and immunofluorescent staining. Mice that carried two floxed CTGF alleles and a Cre/ERT2 transgene under the control of human ubiquitin C (ubc) promoter were used to conditionally delete CTGF gene in a tamoxifen-inducible manner. Phototherapeutic keratectomy (PTK) was used to generate an acute corneal wound and corneal re-epithelialization was assessed by fluorescein staining.

RESULTS

Connective tissue growth factor expression was found in multiple ocular tissues with relatively high levels in the corneal endothelium, lens subcapsular epithelium, and in the vasculature of the iris and retina. Wounded corneas responded with an immediate upregulation of CTGF in the epithelium at the wound margin and a sustained CTGF induction during re-epithelialization. At the onset of haze formation, CTGF protein becomes more focused in the basal epithelium. Deletion of the CTGF gene caused a 40% reduction (P < 0.01) in the cornea re-epithelialization rate in knockout mice compared with wild-type mice.

CONCLUSIONS

Connective tissue growth factor is expressed in the naïve cornea, lens, iris, and retina, and is expressed immediately after epithelial injury. Loss of CTGF impairs efficient re-epithelialization of corneal wounds.

The progression of haze formation in rabbit corneas following phototherapeutic keratectomy

PURPOSE

To determine the topographical location and time course of development of corneal haze in a phototherapeutic keratectomy model using slit lamp examination, macrophotography, quantitative image analysis, and immunofluorescence staining of corneal sections.

METHODS

Rabbit corneas were ablated with an excimer laser and were observed and graded for haze via slit lamp, imaged, and graded by macrophotography. Corneal sections were stained for α-smooth muscle actin (α-SMA) and tenascin-C (TNC). The distribution of haze imaged in the macrophotographs and density of α-SMA and TNC staining were compared. A daily image time course of haze formation was generated using macrophotography.

RESULTS

The first signs of corneal haze were apparent shortly after reepithelialization. The haze was distributed as a ring at the wound margin in all cases, while nearly all corneas also had some central islands of haze initiation. With time, the haze spread within the ablated zone and intensified. The pattern of immunofluorescent staining for α-SMA and TNC at the wound margin mirrored the haze distribution, spread, and intensification with time.

CONCLUSIONS

The initiation and spread of subepithelial haze begins shortly after reepithelialization. The haze then spreads from the loci of initiation and becomes more dense with time, maturing as early as 14 days after wounding. The improved temporal and spatial resolution provided by these data improve the current model of light-scattering haze formation in wounded corneas, which will improve the design of studies aimed at maintaining corneal clarity following acute injury or surgery.

Intraoperative mitomycin C versus autologous conjunctival autograft in surgery of primary pterygium with four-year follow-up

PURPOSE

To compare the 4-year outcome of primary pterygium excision using intraoperative mitomycin C (MMC) with suturing a free conjunctival autograft (CA).

METHODS

A total of 115 eyes with nasal primary pterygium of 115 patients were included in the study. After randomization into two groups, the eyes were operated on by a single surgeon (GK). After excision of the pterygium, 56 eyes received 0.04% MMC intraoperatively on the bare sclera for 3 min and 59 eyes received a free CA sutured using 7-0 Vicryl. Postoperative follow-up was 4 years. Main outcome measures were recurrences, re-operations, surgery time, complications, visual acuity and astigmatism. Statistical evaluation was performed with the chi-squared test.

RESULTS

The recurrence rate was 38% in the MMC group and 15% in the CA group (p < 0.05). The re-operation rate of the recurrences was 53% in the MMC group and 29% in the CA group. Average surgery time was 13 minutes (range: 6-22 min) in the MMC group and 26 min (range: 18-32 min) in the CA group (p < 0.01). There was no significant change in best-corrected visual acuity and astigmatism. One major complication occurred in each group. The most frequently observed complication was delayed epithelial healing (40%) and mild scleral thinning (20%) in the MMC group and suture-related inflammation in the CA group (10%).

CONCLUSION

Pterygium surgery including free autologous conjunctival grafting is associated with fewer recurrences, re-operations and complications than using the bare sclera technique together with single-dose intraoperative MMC.

In vivo confocal microscopic evaluation of morphologic changes and dendritic cell distribution in pterygium

PURPOSE

To observe morphologic changes and the distribution of dendritic cells in pterygium using in vivo laser scanning confocal microscopy (LSCM).

DESIGN

Prospective comparative study.

METHODS

Twenty-six eyes of 26 patients with pterygium and 17 eyes of 17 healthy subjects were recruited. Using LSCM, in vivo images of the pterygium and adjacent clear cornea were captured. The density of basal corneal epithelial cells and keratocytes in the anterior and posterior stroma and the density of dendritic cells in the pterygium and adjacent clear cornea were determined. In the controls, the central cornea and nasal bulbar conjunctiva were imaged. The density of basal corneal epithelial cells, keratocytes, and dendritic cells was evaluated.

RESULTS

Morphologic alterations of the sub-basal nerve plexus were observed in pterygium. The density of basal corneal epithelial cells and anterior keratocytes in pterygium was 5359.0 ± 543.1 cells/mm² and 407.4 ± 188.7 cells/mm² respectively, which was significantly lower than that in the controls (P < .001). The density of dendritic cells in the clear corneas of pterygia was 60.3 ± 25.5 cells/mm², which was significantly higher than the 23.6 ± 11.1 cells/mm² in the central corneas of controls (P < .001). The dendritic cell density in the pterygium was significantly higher than the density in the nasal bulbar conjunctiva of controls (P < .001).

CONCLUSIONS

Histopathologic alterations and increased dendritic cells were evident in pterygium and the adjacent clear cornea by in vivo LSCM. In vivo LSCM was found to be an effective method of observing the morphologic alterations of pterygium.