Corneal epithelial thickness analysis of forme fruste keratoconus with optical coherence tomography

AIM:To explore the significance of corneal epithelial thickness analysis in diagnosing early keratoconus.METHODS:There were 26 clinical keratoconus,21 forme fruste keratoconus,40 high corneal astigmatism(ΔK)and 40 low ΔK eyes involved in the study.Fourierdomain optical coherence tomography was used to measure the corneal epithelial thickness of four groups.The morphological features of topographic map and the thickness of corneal epithelial thinnest point were analyzed.The distribution curve of corneal epithelial thickness at 45°,90°,and 135° axial directions that are through the pupil center was also analyzed.One-way ANOVA was performed to compare the data.RESULTS:The topographic map of forme fruste keratoconus corneal epithelial thickness was uniformity shape;crater shape existed only in clinical keratoconus group;and central island shape mainly existed in highΔK group.The thinnest point of corneal epithelial thickness of forme fruste keratoconus group was significantly lower than that of low ΔK group(P=0.022).The thickness of corneal epithelium in the forme fruste keratoconus at 90°was thinner than that in the low astigmatism group at -1,and -2 mm points(P_(-1mm)=0.015,P_(-2mm)=0.036).CONCLUSION:The analysis of the thinnest point in forme fruste keratoconus corneal epithelium appears earlier than corneal epithelial remodeling.The topographic map of corneal epithelium in high ΔK eyes appears in central island shape,and can be used for the differential diagnosis of early keratoconus.

Increased aquaporin-1 levels in lens epithelial cells with primary angle-closure glaucoma

AIM： To determine the levels of aquaporin-1（AQP-1） in the lens epithelial cells（LECs） of primary glaucoma and to clarify its correlation with lens thickness.METHODS： This study comprised 64 eyes of 64 patients with primary glaucoma, who were divided into 3 groups： 25 eyes of 25 patients with acute primary angle-closure glaucoma（APACG）, 19 eyes of 19 patients with chronic primary angle-closure glaucoma（CPACG） and 20 eyes of 20 patients with primary open angle glaucoma（POAG）. This study also included 12 eyes of 12 patients with senile cataract as controls. The levels of AQP-1 in LECs were examined by real-time quantitative polymerase chain reaction（RT-q PCR） and immunohistochemistry. The lens thickness was measured by A-scan ultrasonography. RESULTS： The AQP-1 m RNA levels of LECs were 0.84±0.27, 0.69±0.34, 0.44±0.19 and 0.51±0.21 in APACG, CPACG, POAG and senile cataract group, respectively. The levels of AQP-1m RNA were significantly higher in PACG groups compared with those in senile cataract and POAG group（all P〈0.05）. The immunohistochemistry showed the AQP-1 expression were strong-positive in PACG groups, but weak-positive in senile cataract and POAG group. A positive correlation was found between AQP-1 m RNA levels and the lens thickness（r=0.645, P〈0.001）. CONCLUSION： These findings show that the higher expression of AQP-1 in LECs may contribute to increased lens thickness, which might be associated with the occurrence and development of PACG.

Fine tuning of the default depth and rate of ablation of the epithelium in customized trans-epithelial one-step superficial refractive excimer laser ablation

Purpose:To fine tune the default depth and rate of ablation of the epithelium in cTen^(TM) customized trans-epithelial one-step superficial refractive surgery by the comparison between the attempted post-operative ideal corneal shape and the achieved corneal shape.Methods:88 consecutive eyes in 64 patients undergoing trans-epithelial superficial excimer ablation using the iVis laser Suite for either myopic/astigmatic or hyperopic/astigmatic refractive error.Each patient had at least 3 months of post-operative follow-up.Topographic examination of all eyes was carried out pre-operatively and at least 3 months post-operatively using the Precisio^(TM) surgical topographer.The comparison of these two measurements yielded values for depth,volumes and rates of ablated corneal tissue.By determining the different ablation rates of stroma and epithelium,a refinement of the depth of epithelium to be removed and a refinement of the stromal ablation were calculated.The mathematical model was applied on each one of the 88 clinical cases and the parameters for the fine tuning of the default depth and rate of ablation of the epithelium were determined using the least squares method.Results:The calculated pure stromal ablation rate was less than the average epithelium/stroma ablation rate used in planning the treatments by a factor of 0.96.The epithelial thickness predefined ablation assumption used to plan removal of the epithelium was adjusted considering the measured ablation and a radial adjustment function established for the fine tuning of the laser radial efficiency and allowing for the normal thickening of the epithelium in the peripheral cornea.From a clinical point of view,this methodology produces an improvement of the efficacy and a reduction of the variance of the clinical results.Conclusion:Comparison of accurately measured pre and postoperative topographies yields accurately established ablation rates of stroma and epithelium in trans-epithelial one step superficial ablation.

Corneal biomechanical changes in allergic conjunctivitis

Background:To explore corneal biomechanical changes,identify related factors and determine early indicators of keratoconus(KC)development risk in allergic conjunctivitis(AC)patients.Methods:A total of 50 patients,including 20 eyes without AC and 30 eyes with AC were enrolled in this study.All patients underwent a complete ocular examination,including evaluations of clinical manifestations of AC,corneal tomography and densitometry by Pentacam,corneal biomechanics by Corvis ST,and corneal and epithelial thickness mapping by RTvue optical coherence tomography(OCT).Results:The index of surface variance(ISV),index of vertical asymmetry(IVA),keratoconus index(KI),index of height decentration(IHD)and Belin/Ambrosio enhanced ectasia total deviation index(BAD-D)were significantly higher in the AC group than in the non-allergic conjunctivitis(NAC)group(P<0.05).The tomography and biomechanical index(TBl)was also significantly higher in the AC group(P=0.04).The average epithelial thickness in the 2-7 mm annulus was significantly thinner in the AC group than in the NAC group(P<0.05).The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group(P<0.001).The ISV,IVA,KI,IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients(P<0.05).The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores(P<0.05).Conclusions:AC patients should be advised to routinely undergo corneal tomographic and biomechanical measurements,and the TBl could be used as an indicator of KC development risk in AC patients.Trial registration:Corneal Biomechanical Changes of Allergic Conjunctivitis,NCT04299399.Registered March 3,2020-Retrospectively registered.

In pursuit of objective dry eye screening clinical techniques

Dry eye is a multifactorial,progressive,and chronic disease of the tears and ocular surface.The disease is multi-factorial and has intermittent symptoms.Discomfort,visual disturbance,tear film instability with potential damage to the ocular surface,and increased tear film osmolarity are known associates.Dry eye is a common clinical problem for eye-care providers worldwide and there is a large number of clinical investigative techniques for the evaluation of dry eye.Despite this,however,there is no globally accepted guideline for dry eye diagnosis and none of the available tests may hold the title of the‘gold standard’.The majority of the techniques involved in the diagnosis of the disease,particularly for its early stages,has a large degree of subjectivity.The purpose of this article is to review existing dry eye investigative techniques and to present a new objective dry eye screening technique based on optical coherence tomography.

Quantifying microstructural changes in retinitis pigmentosa using spectral domain – optical coherence tomography

Background:Most patients of established retinitis pigmentosa(RP)have subnormal peripheral vision and heavily rely on central vision for their daily activities.Central visual acuity is dependent on photoreceptor survival at the macula.Identification of structural changes that precede visual loss is essential.The aim of this study was to correlate the Spectral Domain-Optical Coherence Tomography(SD-OCT)characteristics with visual acuity in patients with typical RP.Methods:This was a retrospective,observational case series of 224 eyes of 113 RP patients conducted a tertiary eye care center.SD-OCT imaging was done for all eyes.Central retinal thickness(CRT),photoreceptor outer segment length(PROS),foveal outer segment pigment epithelial thickness(FOSPET)and ellipsoid zone(EZ)extent were measured.A new variable,FOSPET-PROS ratio(FPR),obtained by dividing FOSPET by PROS is defined and correlated to corrected distance visual acuity(CDVA)in logMAR using linear regression.Results:Out of 113 patients,71 were males and 42 females.Mean age of the patients was 35.4±15.1 years.Mean CDVA was 0.33±0.25 logMAR with no difference between the genders.Mean CRT(218.74±83.5μm)and FPR(1.63±0.22)significantly correlated to CDVA with a correlation coefficient of r=−0.139(p=0.048)and r=0.842(p=0.0001),respectively.FOSPET(mean=71.15±13.8μm)and PROS(mean=44.85±12.5μm)did not show a significant correlation to CDVA,independent of FPR.Conclusions:Retinal microstructural changes on SD-OCT,especially the FPR,can be used as a surrogate marker to monitor disease progression in the central retina in degenerative diseases like RP.

Corneal biomechanical changes in allergic conjunctivitis

Background:To explore corneal biomechanical changes,identify related factors and determine early indicators of keratoconus(KC)development risk in allergic conjunctivitis(AC)patients.Methods:A total of 50 patients,including 20 eyes without AC and 30 eyes with AC were enrolled in this study.All patients underwent a complete ocular examination,including evaluations of clinical manifestations of AC,corneal tomography and densitometry by Pentacam,corneal biomechanics by Corvis ST,and corneal and epithelial thickness mapping by RTvue optical coherence tomography(OCT).Results:The index of surface variance(ISV),index of vertical asymmetry(IVA),keratoconus index(KI),index of height decentration(IHD)and Belin/Ambrosio enhanced ectasia total deviation index(BAD-D)were significantly higher in the AC group than in the non-allergic conjunctivitis(NAC)group(P<0.05).The tomography and biomechanical index(TBI)was also significantly higher in the AC group(P=0.04).The average epithelial thickness in the 2-7mm annulus was significantly thinner in the AC group than in the NAC group(P<0.05).The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group(P<0.001).The ISV,IVA,KI,IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients(P<0.05).The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores(P<0.05).Conclusions:AC patients should be advised to routinely undergo corneal tomographic and biomechanical measurements,and the TBI could be used as an indicator of KC development risk in AC patients.