Short-term observation of management of sclera patch grafts used in the scleral defects

Background:To explore the safety and effectiveness of Sclera patch grafts in the management of scleral defects.Methods:This is a retrospective uncontrolled study.Medical records were retrospectively reviewed for 8 eyes of 8 patients with sclera patch grafts.Two patients had necrotizing scleritis,2 patients had scleral melting/perforation secondary to thermal burns,4 patients had scleral staphyloma secondary to surgery.Sclera was reconstructed with allogenic sclera patch grafts,6 in 8 patients combined autologous conjunctival pedicle flap,1 patient combined partial medial rectus translocation,1 patient combined autologous pedicle tenon graft,simultaneously.Treatment outcomes were evaluated using structural integrity,best corrected visual acuity(BCVA),scleritis remission,sclera rejection and melt,and ocular symptoms.Results:Eight patients were reviewed.In all of these cases,satisfactory anatomic and functional outcomes were achieved.In the at least half a year follow-up,the BCVA of all the eight patients were no worse than that of preoperative.No eye pain,foreign body sensation and other discomforts showed in all the patients,except one woman,who showed sclera rejection and melt 1 month postoperative.In addition,one patient showed high intraocular pressure(28 mmHg),which can be controlled by a kind of medicine.Conclusions:In this series,sclera patch grafts is an effective method for management scleral defects in the at least half a year following-up.Attention should be paid to the sclera patch rejection and melt post operatively.

Scleral remodelling in myopia and its manipulation:a review of recent advances in scleral strengthening and myopia control

The biological mechanisms of eye growth and refractive development are increasingly well characterised,a result of many careful studies that have been carried out over many years.As the outer coat of the eye,the sclera has the ultimate impact on the restraint or facilitation of eye growth,thus any changes in its biochemistry,ultrastructure,gross morphology and/or biomechanical properties are critical in refractive error development and,in particular,the development of myopia.The current review briefly revisits our basic understanding of the structure and biomechanics of the sclera and how these are regulated and modified during eye growth and myopia development.The review then applies this knowledge in considering recent advances in our understanding of how the mechanisms of scleral remodelling may be manipulated or controlled,in order to constrain eye growth and limit the development of myopia,in particular the higher degrees of myopia that lead to vision loss and blindness.In doing so,the review specifically considers recent approaches to the strengthening of the sclera,through collagen cross-linking,scleral transplantation,implantation or injection of biomaterials,or the direct therapeutic targeting and manipulation of the biochemical mechanisms known to be involved in myopia development.These latest approaches to the control of scleral changes in myopia are,where possible,placed in the context of our understanding of scleral biology,in order to bring a more complete understanding of current and future therapeutic interventions in myopia,and their consequences.

Form-deprivation myopia induces decreased expression of bone morphogenetic protein-2, 5 in guinea pig sclera

AIM: To identify the presence of various bone morphogenetic proteins(BMPs) and their receptors in normal sclera of human, rat and guinea pigs, and to determine whether their expression changed with form-deprivation myopia(FDM) in guinea pig sclera.METHODS: The expression of BMPs and BMP receptors were detected using reverse transcription polymerase chain reaction(RT-PCR) and immunofluorescence. Two-week-old guinea pigs were monocularly form-deprived with a translucent lens. After fourteen days induction of FDM, total RNA was isolated and subjected to RT-PCR to examine the changes of BMPs and BMP receptors in tissues from the posterior sclera. Western blotting analysis was used to investigate their changes in protein levels.RESULTS: Human sclera expressed m RNAs for BMP-2,-4,-5,-7,-RIA,-RIB and BMP-RII. Conversely, rat sclera only expressed m RNA for BMP-7 and BMP-RIB,while the expression of BMPs and BMP receptors in guinea pigs were similar to that of humans. Human sclera also expresses BMP-2,-4,-5,-7 in protein level.Fourteen days after the induction of myopia, significant decreased expressions for BMP-2 and BMP-5 in the posterior sclera of FDM-affected eyes(P <0.05 vs internal control eyes).· CONCLUSION: Various BMPs were expressed in human and guinea pig sclera. In the posterior sclera,expressions of BMP-2 and BMP-5 significantly decreased in FDM eyes. This finding indicates that various BMPs as components of the scleral cytokines regulating tissue homeostasis and provide evidence that alterations in the expression of BMP-2 and BMP-5 are associated with sclera remodeling during myopia induction.

Dynamic changes of activator protein 1 and collagen I expression in the sclera of myopia guinea pigs

AIM: To investigate the dynamic changes of activator protein 1(AP1) and collagen I expression in the sclera of form-deprivation myopic model in guinea pigs. METHODS: A form-deprivation myopic model in guinea pigs were established with the left eye covered for 2 to 6 wk(FDM group). Normal control group(n=25) were untreated. Changes in refractive power and axial length(AL) were measured and recorded at different time points. Expressions of AP1 and collagen 1 of the sclera were measured with Western blotting and reverse transcription-polymerase chain reaction(RT-PCR). The relationship between AP1 and collagen I levels was analyzed. RESULTS: After 0, 2, 4, 6 wk, and 4/-1 wk of form-deprivation, the diopter in the FDM group was gradually changed(2.08±0.31,-1.23±0.68,-4.17±0.58,-7.07±0.55, and-2.67±0.59 D, respectively, P<0.05), and the AL was gradually increased(5.90±0.38, 6.62±0.37, 7.30±0.35, 7.99±0.31, and 6.97±0.32 mm, respectively, P<0.05). With the prolongation of covered time, the protein expressions of AP1 and collagen I in the FDM group were gradually down-regulated(all P<0.05);the mRNA expressions of them were also gradually down-regulated(all P<0.05);and there was positive correlation between them. The control group had no obvious change in each index(all P>0.05). CONCLUSION: AP1 may be an important transcription factor involved in the regulation of collagen I synthesis and degradation during myopic scleral remodeling.

Complement factors C1q, C3 and C5b-9 in the posterior sclera of guinea pigs with negative lens-defocused myopia

· AIM: To investigate the expression of complement factors in the posterior scleral fibroblasts of guinea pigs with negative lens-defocused myopia.· METHODS: Eighteen guinea pigs were assigned randomly to two groups: the negative lens-defocused group(NLD group, n =9) and the normal control without treatment group(NC group, n =9). The effect of myopic induction was compared in three subgroups: eyes treated with a-10.00 D negative lens in the NLD group(NL group), eyes treated with a plano(0 D) lens in the NLD group(PL group), and untreated right eyes in the NC group(NC group). The following analyses were conducted at four weeks: examination of the refractive error via retinoscopy, assessment of complement C5b-9expression in the posterior scleral fibroblasts using immunohistochemistry, and measurements of complement C1 q and C3 protein levels in the posterior sclera by Western blot.·RESULTS: After an induction period of four weeks, a significant myopic shift was detected in the eyes of the NL group, relative to that of the PL and NC groups(P <0.05). Data analysis showed a significant increase in the percentage of C5b-9 immunopositive fibroblasts in the posterior sclera of the NL group eyes, compared to the PL group(q =11.50, P <0.001). Significantly higher levels of C1q(q =4.94, P =0.01) and C3(q =4.07, P =0.03)protein were detected in the posterior sclera of NL group eyes, compared to the PL group. There were no significant difference between the PL and NC groups for C5b-9(q =2.44, P =0.10), C1q(q =1.55, P =0.53) and C3(q =0.98, P =0.77) in the posterior sclera.·CONCLUSION: The data from present study provide evidence of the up-regulation of C5b-9, C1 q and C3 in the posterior scleral fibroblasts in a NLD myopic animal model. The results suggest that the complement system may be involved in the development of myopia.

Regulation of scleral fibroblast differentiation by bone morphogenetic protein-2

Bone morphogenesis proteins(BMPs) are multi-functional growth factors. They are expressed in retina,retinal pigment epithelium(RPE) and sclera and serve as a regulator in the growth and development of the eye. This article reviewed the chondrogenic potency of the sclera,biochemical and pathological changes of myopic scleral tissue and the differentiation of chondrogenesis by BMP-2. We proposed the hypothesis that BMP-2 can regulate differentiate of scleral fibroblasts and affect the development of myopia.

Correlation of discoloration and biomechanical properties in porcine sclera induced by genipin

·AIM: To study the feasibility of using the discoloration to evaluate the biomechanical properties after treating with genipin.·METHODS: Porcine cadaver eyes were treated for30 min with 1.0%(by w/v) genipin. Untreated samples were used as controls. After treatment, scleral strips of4.0 ×10.0-mm2 were cut. The denaturation temperature(Td) measurement and stress-strain test were performed after taking photograph to analyze the color.·RESULTS: Within 24 h after treating with genipin, the sclera exhibited a bluish color which became deeper with time. And the denaturation temperature also was increased gradually. Compared with untreated groups, at1, 6, 12, 24 and 36 h after treatment, the ultimate stress were increased by 56%, 153%, 173%, 225% and 211%respectively. The Young's modulus at 10% strain also increased by 170%, 246%, 264%, 389% and 288%respectively. There were strong correlation between the discoloration and the biomechanical properties(ΔE-Ultimate stress:R2=0.892, P =0.00; ΔE-Young's modulus:R2=0.602, P =0.00).·CONCLUSION: Genipin could be used to strengthen collagen gradually in a relatively short time span. And the biomechanical properties could be reliably evaluated via simple visible discoloration.

Protective effects of riboflavin-UVA-mediated posterior sclera collagen cross-linking in a guinea pig model of form-deprived myopia

AIM:To evaluate the effect of posterior sclera collagen cross-linking induced by riboflavin-ultraviolet A(UVA)on form-deprived myopia in guinea pigs.METHODES:Twenty-five pigmented guinea pigs of 3-week-old were randomly assigned into 4 groups that included normal control(NOR,n=7),form-deprived(FDM,n=7),normal with riboflavin-UVA cross-linking(NOR+CL,n=5)and form-deprived with cross-linking(FDM+CL,n=6).The NOR+CL group and the FDM+CL group received the riboflavin-UVA induced cross-linking at day 0.FDM was induced by monocularly deprived with facemask in the right eyes.The refraction,axial length and corneal curvature were measured by retinoscopy,A-scan and keratometer respectively in scheduled time points(day 0 and 1,2,3,4 wk after form-deprivation).At the end of 4 weeks’experiment,stress-strain tests of sclera were measured and morphological changes of sclera and retina were examined.RESULTS:After 4 wk,the interocular difference of refractive error were-0.11±0.67,-2.93±0.56,1.10±0.58,and-1.63±0.41 D in the NOR,FDM,NOR+CL,and FDM+CL groups respectively.Mixed-effect linear model revealed significant effect of FDM(P<0.01)and CL(P<0.001).Also,after 4 wk,the interocular difference of axial length were 0.01±0.04,0.29±0.07,-0.13±0.06,and 0.11±0.05 mm in the NOR,FDM,NOR+CL,and FDM+CL group.Mixedeffect linear model revealed significant effect of FDM(P<0.001)and CL(P<0.01).As for corneal curvature,significant interocular difference have not found between any of the two groups.At the end of this experiment,the ultimate stress and elastic modulus were found significantly increased in both CL groups.But no difference was found in the groups without cross-linked.There was no abnormality observed in the retina and RPE cells of the treated eyes.CONCLUSION:The posterior sclera collagen crosslinking induced by riboflavin-UVA can slow down the progress of myopia and increase the sclera biomechanical strength in the guinea pig model of form-deprived myopia.

Scleral TGF-β1 and Smad3 expression is altered by TCM Bu Jing Yi Shi Tablets in guinea pigs with form-deprivation myopia

Objective:To explore whether the traditional Chinese medicine(TCM)Bu Jing Yi Shi Tablets alters the expression of scleral TGF-b1 and Smad3 in guinea pigs with formdeprivation myopia(FDM).Methods:Sixty-five guinea pigs were randomly divided into control,model,low-,medium-,and high-dose treatment groups.Except for the control group,FDM was induced by covering the right eye of each animal with opaque latex.The treatment groups were gavaged with different suspension concentrations of Bu Jing Yi Shi Tablets.Refraction and axial length were performed before and after myopia induction.At the end of the experiment,all right eyes were extracted,and scleral sections were prepared for staining and TGF-b1 and Smad3 immunohistochemistry.Scleral thickness and area,the scleral fibroblast quantity,and scleral TGFb1 and Smad3 expressions were measured.Results:The 5 FDM groups had the same initial axial length and diopter,the final diopter and axial length of the model group were significantly increased compared with the control group and treatment groups(P<.01).The axial length of each treatment group decreased as the dose decreased compared with the model group(P<.01);the total scleral area(P<.05 e.01)and the number of scleral fibroblasts(P<.01)in the model group were significantly lower than the treatment groups.Both the TGF-b1 and Smad3 integral optical densities in the model group were significantly lower than the control and medium-and high-dose treatment groups(P<.01).TGF-b1 and Smad3 mRNAs in the model group were decreased compared with the control group,but increased in expression after treatment.

Autologous sclera-muscle flaps technique in evisceration with hydroxyapatite implantation

·AIM: To provide superior cosmetic results and reduce complications, unlike traditional evisceration coupled with implant insertion technique and its modifications,we have developed a novel and simple technique for anophthalmic patients.·METHODS: All patients who underwent the scleral-muscle flaps procedure in evisceration with the placement of hydroxyapatite implant were included in the study. Main outcome measures were complications such as exposure, infection, chemosis, conjunctival inclusion cysts, granulomas. Meanwhile, implant motility was indirectly measured and the results were collected and analyzed.· RESULTS: A total of twenty-eight patients were enrolled in the study. Eighteen were men(64.29%) and ten were women(35.71%). Ages ranged from 18 to 65y(mean age, 32 years old). Mean follow-up was 12.32mo(range, 9-16mo). All patients received a hydroxyapatite implant. The average diameter of the implant was 19.29 ±1.36 mm(range, 18-22 mm). Minor complications occurred in 3 patients, and a major complication was observed in 1 patient. Mean motility were 11.04 ±1.45 mm horizontally(range, 7-14 mm) and 8.57 ±1.50 mm vertically(range, 5-12 mm).·CONCLUSION: The sclera-muscle flaps technique in evisceration with hydroxyapatite implantation is simple and practical that eases the surgical procedure, enables a proper size hydroxyapatite implantation, distinctively reduces complications and provides superior surgery results, especially the motility of the implant.

Auricular cartilage versus donor sclera as a wrapping of hydroxyapatite orbital implants

AIM: To retrospectively compare postoperative outcomes after primary enucleation and placement of a hydroxyapatite(HA) implant without wrapping, wrapped with auricular cartilage or donor sclera. METHODS: Medical records of patients presented as intraocular tumor or severe ocular injury were identified from the electronic medical record system. Cases underwent enucleation and HA orbital implantation were enrolled in this study and were divided into 3 groups according to the wrapping material of HA implant. Cases with autogenous cartilage caps were enrolled in group A(n=11), with donor sclera caps in group B(n=12), and without any wrapping material in group C(n=9). Follow-ups were set at 1, 2 wk, 1, 3, 6, and 12 mo after surgery.RESULTS: Altogether 32 cases finished the followup and were enrolled in this study. Three cases(27.27%) in group A, 4 cases(33.33%) in group B, and 4 cases(44.44%) in group C developed one complication each after surgery. In group A, no HA exposure occurred, but conjunctival inclusion cyst occurred in one and severe conjunctive chemosis in two cases. In group B, one HA exposure occurred, conjunctive inclusion cysts occurred in one, severe conjunctive chemosis occurred in one, and conjunctival granuloma occurred in one case. In group C, one HA exposure occurred, severe conjunctive chemosis occurred in two cases, and conjunctival granuloma occurred in one case. The case of exposure of none-wrapped implant was noted in the first 6 mo after placement of the orbital implant. The case of exposure of donor sclerawrapped implant was noted at the 12 mo after placement of the orbital implant. Both exposure cases were treated successfully with conservative treatment.CONCLUSION: With low incidence of implant exposure and mild complications, auricular cartilage can be a good choice of alternative wrapping material of orbit implant with satisfied outcome.

Non-Invasive and Non-Destructive Determination of Corneal and Scleral Biomechanics Using Vibrational Optical Coherence Tomography: Preliminary Observations

Experimental measurements made in this study on human and porcine eyes suggest that the resonant frequency for both cornea and sclera varies from 130 to 150 Hz and increases slightly with increasing intraocular pressure. The values of the moduli calculated using the experimental values of the thickness are close to 2 MPa. Similar values of the modulus for cornea and sclera suggest that there is very little stress concentration at the cornea-scleral junction and that any stress concentration that occurs probably resides at the scleral attachment laterally and posteriorly. These moduli are close to those measured in vivo on human skin suggesting that the mechanism of tensile deformation of skin, cornea and sclera are similar. Our results suggest that the modulus of cornea and sclera can be measured non-invasively and non-destructively using vibrational OCT. Results of these studies will assist clinicians to better understand the influence of biomechanics on the outcome of corneal refractive surgery as well as the pathogenesis of eye disorders such as glaucoma, myopia and keratoconus.

AB008:Structural and molecular changes in cornea and sclera of highly myopic-astigmatic chicks

Myopia and astigmatism, two common refractive errors frequently co-exist, are degrading vision at all working distances in populations worldwide. Eyeballs having high degrees of myopia and astigmatism are known to exhibit abnormal eye shape at the anterior and posterior eye segments, but whether the outer coats of these abnormal eyeballs, cornea anteriorly and sclera posteriorly, are regulated by region-specific molecular mechanism remains unclear. Here we presented the changes in eye shape and mRNA expression levels of three genes (MMP2, TIMP2, and TGFB2), all known to participate in extracellular matrix organization, at five regions of the cornea and sclera in chickens developing high myopia and astigmatism induced by form deprivation. Our results showed that, compared to normal chicks, the highly myopic-astigmatic chicks had significantly astigmatic cornea, deeper anterior chamber, longer axial length, and higher expressions of all three genes in the superior sclera. These results imply that local molecular mechanism may manipulate the eye’s structural remodeling across the globe during refractive eye growth.

Allogeneic sclera graft combined autologous conjunctival flap for repairing the emergent corneal perforation

To report a palliative and alternative surgical procedure, allogeneic sclera graft combined with autologous conjunctival flap (ASGACF), employing to repair the large emergent corneal perforation. The detail protocol of the surgical procedure was characterized and four representative cases were reviewed. An allogeneic sclera graft and recipient bed were prepared as the traditional penetrating keratoplasty (PK). And then sutured the sclera graft to the bed with 10-0 nylon suture and covered with a pedicled autologous conjunctival flap in half size. In the follow-up, the ASGACF repaired all of the corneal perforations and restored the integral walls of eyeballs, in spite of one who underwent a second surgery. This surgical procedure provided a palliative method to repair the large emergent corneal perforation while there is the lack of a corneal graft.

Biomechanics of sclera crosslinked using genipin in rabbit

AIM:To strengthen the biomechanics of collagen by crosslinking rabbit scleral collagen with genipin to develop a new therapy for preventing myopic progression. METHODS:Ten New Zealand rabbits were treated with 0.5 mmol/L genipin injected into the sub-Tenon's capsule in the right eyes. Untreated contralateral eyes served as the control. The treated area was cut into scleral strips measuring 4.0 mm×10.0 mm for stress-strain measurements(n=5). The remaining five treated eyes were prepared for histological examination.RESULTS:Compared to the untreated scleral strips,the genipin-crosslinked scleral strips showed that the ultimate stress and Young's modulus at 10% strain were increased by the amplitude of 130% and 303% respectively,ultimate strain was decreased by 24%. There had no α-smooth muscle actin(α-SMA)positive cells in control and treated sclera. Histologically,there was no sign of apoptosis in the sclera,choroid,and retina; and no side effects were found in the peripheral cornea and optic nerve adjacent to the treatment area.CONCLUSION:Genipin induced crosslinking of collagen can increase its biomechanical behavior by direct strengthening of the extracellular matrix in rabbit sclera,with no α-SMA expression seen in the myofibroblasts. As there is no evidence of cytotoxicity in the scleral,choroidal,and retinal cells,genipin is likely a promising agent to strengthen the weakened sclera to prevent myopic progression.

Expression and role of specificity protein 1 in the sclera remodeling of experimental myopia in guinea pigs

AIM:To study the expression of collagen I and transcription factor specificity protein 1(Sp1),a transforming growth factor-β1(TGF-β1) downstream target,and reveal the impact of the TGF-β1-Sp1 signaling pathway on collagen remodeling in myopic sclera.METHODS:Seventy-five 1-week-old guinea pigs were randomly divided into normal control,form deprivation myopia(FDM),and self-control groups.FDM was induced for different times using coverage with translucent latex balloons and FDM recovery was performed for 1wk after 4wk treatment;then,changes in refractive power and axial length were measured.Immunohistochemistry and reverse transcription-polymerase chain reaction were used to evaluate dynamic changes in collagen I and Sp1 expression in the sclera of guinea pigs with emmetropia and experimental myopia,and the relationship between collagen I and Sp1 levels was analyzed.RESULTS:In the FDM group,the refractive power was gradually changed(from 2.09±0.30 D at week 0 to-1.23±0.69 D,-4.17±0.59 D,-7.07±0.56 D,and-4.30±0.58 D at weeks 2,4,6,and 1wk after 4wk,respectively;P<0.05),indicating deepening of myopia.The axial length was increased(from 5.92±0.39 mm at week 0 to 6.62±0.36 mm,7.30±0.34 mm,7.99±0.32 mm,and 7.41±0.36 mm at weeks 2,4,6,and 1wk after 4wk;P<0.05).The m RNA and protein expression of Sp1 and collagen I in the sclera of the FDM group was lower than that of the control groups(P<0.05),and the reduction was eye-coverage time-dependent.Furthermore,correlation between Sp1 and collagen I down-regulation in the myopic sclera was observed.CONCLUSION:Our data indicate that transcription factor Sp1 may be involved in the regulation of type I collagensynthesis/degradation during myopic sclera remodeling,suggesting that TGF-β1 signaling plays a role in the development and progression of myopia.

Scleral ultrastructure and biomechanical changes in rabbits after negative lens application

AIM: To address the microstructure and biomechanical changes of the sclera of rabbits after negative lens application by spectacle frame apparatus.METHODS: Five New Zealand rabbits of seven weeks post-natal were treated with-8 D lens monocularly over the course of two weeks. Refractive errors and axial length(AXL) were measured at the 1 st, 7 th and 14 th days of the induction period. Ultrastructure of sclera was determined with electron microscopy. Biomechanical properties were tested by an Instron 5565 universal testing machine.RESULTS: Lens-induced(LI) eyes elongated more rapidly compared with fellow eyes with AXL values of 15.56±0.14 and 15.21±0.14 mm(P<0.01). Fibril diameter was significantly smaller in the LI eyes compared with control ones in the inner, middle, and outer layers(inner layer, 63.533 vs 76.467 nm; middle layer, 92.647 vs 123.984 nm; outer layer, 86.999 vs 134.257 nm, P<0.01, respectively). In comparison with control eyes, macrophage-like cells that engulfed fibroblasts, dilated endoplasmic reticulum, and vacuoles in fibroblasts were observed in the inner and middle stroma in the LI eyes. Ultimate stress and Young's modulus were lower in the LI eyes compared with those in the control eyes.CONCLUSION: Negative lens application alters eye growth, and results in axial elongation with changes in scleral ultrastructural and mechanical properties.

Influence of High Level TGF-β1 on Scleral Thickness

In order to explore the role of TGF-β1 in scleral remodeling and the possible mechanism,the influence of high level TGF-β1 on scleral thickness and the expression of MMP-2 and TIMP-2 was investigated in a TGF-β1 transgenic mouse model.Alb/TGF-β1(Cys223,225Ser) TGF-β1 transgenic mice were used as experimental subjects and non-transgenic littermates as controls.Plasma levels of TGF-β1 were determined by ELISA.TGF-β1,MMP-2 and TIMP-2 levels in sclera were detected by using Western blot.The thickness of posterior sclera was measured by computerized image analysis of a midsagittal section.Mean difference was analyzed with independent t-test.The results showed plasma levels of TGF-β1 in transgenic mice were 1.68 times as much as that in the controls(P<0.01).TGF-β1 levels in the sclera of transgenic mice were 2.68 times of the controls(P<0.01).Posterior scleral thickness in transgenic mice were significantly thicker than in the controls.There was no significant difference in the MMP-2 levels between transgenic mice and controls,but the TIMP-2 levels were increased significantly in transsgenic mice as compared with those in the controls.It was suggested that high levels of TGF-β1 in transgenic mice could result in the increased scleral thickness by inducing the expression of TIMP-2 to suppress the activity of MMP-2,finally inhibiting the degradation of collagen.

Biomechanics of the sclera and effects on intraocular pressure

Accumulating evidence indicates that glaucoma is a multifactorial neurodegenerative disease characterized by the loss of retinal ganglion cells(RGC), resulting in gradual and progressive permanent loss of vision.Reducing intraocular pressure(IOP) remains the only proven method for preventing and delaying the progression of glaucomatous visual impairment.However, the specific role of IOP in optic nerve injury remains controversial, and little is known about the biomechanical mechanism by which elevated IOP leads to the loss of RGC. Published studies suggest that the biomechanical properties of the sclera and scleral lamina cribrosa determine the biomechanical changes of optic nerve head, and play an important role in the pathologic process of loss of RGC and optic nerve damage. This review focuses on the current understanding of biomechanics of sclera in glaucoma and provides an overview of the possible interactions between the sclera and IOP. Treatments and interventions aimed at the sclera are also discussed.

Effects of scleral encircling surgery on vitreous cavity length and diopter

AIM: To observe the changes of vitreous cavity length and diopter after scleral encircling(SE) produce.·METHODS: This prospective study included 68 eyes of68 non-consecutive patients with macula-off retinal detachment who were operated by SE surgery. The corneal refractive power, ocular axial length and diopter were measured by keratometer, A-mode ultrasonic meter and computed dioptometer.· RESULTS: There was no significant difference in corneal refractive power among preoperative and post operative 1, 3 and 6mo(0.57±0.54 D at pre-surgery; 0.72±0.26 D at 1mo; 0.71 ±0.34 D at 3mo; 0.69 ±0.31 D at 6mo;all P >0.05). Axial lengths were obviously lengthened,especially in vitreous cavity length(17.87 ±3.09 mm,19.69 ±3.12 mm, 18.97 ±3.56 mm, 18.76 ±3.47 mm, 18.68 ±3.42 mm at pre-surgery, 1wk, 1, 3 and 6mo postoperatively,P <0.05) and diopter also increased at beginning and then recovered gradually. After 1 and 3 mo, axial length(vitreous cavity length) and myopia were more and in higher degree than before surgery.·CONCLUSION: The change of postoperative vitreous cavity length is the main factor that results in the changes of axial length and then makes the change of diopter.