Clinical evaluation of scanning laser polarimetry: I Intraoperator reproducibility and design of a blood vessel removal algorithm

AIMS—To evaluate the reproducibility of the retardation values (change in polarisation) obtained with the scanning laser polarimeter in a series of normal subjects and glaucoma patients. To improve the analysis of the raw data by devising and evaluating a blood vessel removal algorithm.
METHODS—Scanning laser polarimetry was performed on 10 normal subjects and 10 glaucoma patients. A series of six images was obtained from each eye. The normal subjects were re-imaged 3 months after their initial assessment. The retardation values obtained from each eye were analysed using the authors' own methods, including the use of an algorithm to remove blood vessels from the polar profiles. The reproducibility of these measurements and the performance of the blood vessel removal algorithm were assessed.
RESULTS—The "individual point" coefficient of variation was approximately 12.5% for normal subjects and 17.0% for glaucoma patients. The "integral" coefficient of variation for these groups was approximately 5.5% and 9.5% respectively. The reproducibility of the measurements did not improve with an increased number of measurements. There was no difference in the reproducibility of the measurements in normal subjects over time. The blood vessel removal algorithm improved the reproducibility of the measurements when the shape of the profile was assessed.
CONCLUSION—The intraoperator reproducibility of retardation values obtained with the scanning laser polarimeter is satisfactory for its use as a clinical tool. The use of a blood vessel removal algorithm improves the reproducibility of the measurements and also assists the clinician in the interpretation of the polar profiles. Furthermore, it allows the construction of normal database polar profiles, thereby enabling the identification, location and quantification of retinal nerve fibre layer damage in an "at risk" individual's polar profile.

Keywords: scanning laser polarimetry; glaucoma; reproducibility; algorithm     

Depolarization properties of the optic nerve head: the effect of age

The degree of polarization (DOP) of the light reflected from the optic nerve head has been assessed by means of a polarimetric scanning laser ophthalmoscope as a function of the age of the participants. Four fundus images corresponding to independent polarization states in the recording pathway were used to compute the spatially-resolved DOP. This was not uniform across the optic nerve head and depended on both the location and the participant's age. Along a peripapillary annulus the DOP followed a double-peak pattern. Moreover, the values along this annulus decreased significantly with increasing age. This depolarization appears to originate in part in the retinal nerve fiber layer. Detailed age-dependent knowledge of the ocular depolarization properties may help to improve clinical diagnosis of the retinal nerve fiber layer.     

偏振激光扫描仪联合个体化角膜补偿技术对可疑青光眼的随访研究

目的 对临床可疑青光眼患者进行长期的偏振激光扫描仪联合个体化角膜补偿技术(scanning laser polarimetry with variable corneal compensation, GDx VCC)随访,分析GDx VCC对该类患者的诊断价值.方法 选取门诊可疑青光眼的眼底检查视乳头杯/盘比(C/D)≥0.4,或双眼不对称且C/D差值≥0.2,静态视野检查结果正常患者68例,随访前后均用GDx VCC检查(采用相同的角膜补偿值).如双眼C/D值相同,随机选取1眼,如C/D值不同,则选取C/D值大的1眼,对结果进行t检验统计学分析.结果 随访时间6～30个月,平均(12.5±7.0)个月,眼底C/D值为 0.57±0.17.随访前后GDx VCC 检查:椭圆平均值分别为50.33±7.72和49.66±8.12,上方平均值为58.72±13.56和58.18±12.01,下方平均值为60.71±11.31和59.13±11.95,神经纤维指数为30.85±19.62和33.03±21.22,差异无统计学意义,但从绝对数值上,椭圆平均值、上方平均值和下方平均值变小,神经纤维指数变大.其中7例(10.3%)诊断为青光眼, 21例(30.9%)排除青光眼,40例(58.8%)仍需进一步随访.结论 对临床怀疑青光眼的患者应长期进行随访,GDx VCC随访对青光眼的诊断有一定的价值.(中国眼耳鼻喉科杂志,2009,9:92-94)     

The Groningen Longitudinal Glaucoma Study. II. A prospective comparison of frequency doubling perimetry,the GDx nerve fibre analyser and standard automated perimetry in glaucoma suspect patients

Purpose: We aimed to determine prospectively the incidence of abnormal test results on frequency doubling perimetry (FDT), the nerve fibre analyser (GDx) and standard automated perimetry (SAP) in a cohort of glaucoma suspect patients with normal findings for all these tests at baseline. Methods: Seventy glaucoma suspect patients were followed prospectively for 4 years with SAP (Humphrey field analyser 30‐2 SITA Fast), FDT (C‐20 full‐threshold) and GDx (Version 2.010) in a clinical setting. All patients had normal baseline test results on SAP, FDT and GDx. After the follow‐up period, the number of patients who converted (whose test results changed from normal at baseline to reproducibly abnormal during follow‐up) were counted for each technique and then compared. The cut‐off point for FDT was > 1 depressed test‐point p < 0.01 in the total deviation probability plot; the cut‐off point for GDx was the Number > 29. Results: Of the 70 glaucoma suspect patients, three converted on FDT, 14 on GDx and six on SAP. These proportions are significantly different for GDx versus SAP (p = 0.033) and GDx versus FDT (p = 0.002), but not for FDT versus SAP (p = 0.256). Conclusions: The most frequent finding after a 4‐year follow‐up was conversion on GDx.     

GDx-VCC performance in discriminating normal from glaucomatous eyes with early visual field loss

Background To evaluate the ability of scanning laser polarimetry with variable corneal compensation (GDx-VCC) in separating healthy from glaucomatous patients with early visual field (VF) loss.Methods Sixty-two healthy and 48 glaucomatous age-matched patients with early glaucoma [mean deviation (MD): −1.74dB ±1.69] underwent complete ophthalmological evaluation, automated achromatic perimetry (AAP) and retinal nerve fiber layer (RNFL) measurement with GDx-VCC. One randomly selected eye from each subject was considered. Glaucomatous VF defects had either Glaucoma Hemifield Test (GHT) outside normal limits or pattern standard deviation (PSD) outside 95% confidence limits. Mean (±SD) MD, PSD and GDx-VCC parameters in the two groups were compared by t-test. For each GDx-VCC parameter, area under receiver operating characteristics (AUROC) curve and sensitivity at predetermined specificity ≥80% and ≥95% were calculated. Moreover, the parameter with largest AUROC was evaluated by likelihood ratios (LRs).Results Mean values for MD, PSD and ten of 14 GDx-VCC parameters were significantly different between the two groups (P<0.001). The three parameters with largest AUROCs were the nerve fiber indicator (NFI) (0.870), superior average (0.817) and normalized superior area (0.816) (P=0.08 for differences between AUROCs). NFI displayed sensitivity values of 80.2% and 60.4% for specificity ≥80% and ≥95%, respectively. At NFI cutoff value of 30, positive LR was 34.9 (95% CI: 4.9–247.6) and negative LR was 0.45 (95% CI: 0.32–0.61). Interval LRs showed large effect on post-test probability for NFI values ≤18 or ≥31.Conclusions In our sample of eyes with early VF loss, GDx-VCC showed moderate-to-good discriminating ability. Among the best performing parameters, NFI had the largest AUROC, but several glaucomatous eyes (21, 43.8%) had NFI <30. This suggests that algorithm for NFI calculation requires some refinement when eyes with early VF loss are evaluated.     

Posterior capsular opacification affects scanning laser polarimetry examination

Purpose To illustrate the effect of posterior capsular opacification (PCO) on retinal nerve fiber layer (RNFL) retardation measurements obtained during scanning laser polarimetry (SLP).Methods SLP was performed using GDx VCC on three eyes of three non-glaucomatous patients with clinically significant PCO, before and after Nd:YAG capsulotomy.Results PCO removal by Nd:YAG capsulotomy was associated with marked variations in retardation map morphology and with apparent RNFL thinning. Retardation map atypia decreased and typical scan score (TSS) increased remarkably after capsulotomy in all three cases.Conclusion An artifact introduced by PCO presence can affect SLP measurements reliability.Presented in part at the 80th Spanish Society of Ophthalmology Congress, Cordoba, Spain, September–October 2004None of the authors has a financial or proprietary interest in any material or method mentioned     

年龄对正常成年人视网膜神经纤维层厚度的影响(英文)

目的使用偏振激光扫描仪对部分健康的中国成年人视网膜神经纤维层（RNFL）厚度进行测定,评估年龄和RNFL厚度之间的关系。方法使用GDxVCC神经纤维分析仪的两种不同检测模式（可变角膜补偿,VCC;强化角膜补偿,ECC）测定150例患者共150眼的视网膜神经纤维层厚度。测量参数包括：颞侧-上方-鼻侧-下方-颞侧平均（TSNITave）、上方平均（Superiorave）、下方平均（Inferiorave）、TSNIT标准差（TSNITstdDev）、和神经纤维指数（NFI）。结果VCC检测模式得到的TSNITave、Superiorave、Inferiorave、TSNITstdDev、NFI平均值分别为（57.12&#177;6.26）,（69.35&#177;4.21）,（67.59&#177;7.06）,（25.46&#177;4.02）,（17.35&#177;7.59）。ECC检测模式五项检测值分别为：（56.15&#177;5.32）,（68.24&#177;6.63）,（66.90&#177;2.40）,（24.80&#177;6.76）,（18.84&#177;8.51）。VCC和ECC模式的检测值之间的差异不具统计学意义。在总样本人群中检测参数指标与年龄存在统计学意义的相关性。而在40岁以上人群中检测参数指标与年龄未发现相关性。结论VCC和ECC模式对检测150例正常国人视网膜神经纤维层厚度的检测值之间不存在统计学差异。对21～70岁的健康人眼中,RNFL厚度检测值随年龄增长而变薄,但在40岁以上人群中未见此改变。     

Retinal nerve fibre layer polarimetry: histological and clinical comparison

AIMS—To compare histological thickness of the retinal nerve fibre layer in the primate with retardation measurements obtained in vivo using the Mark II Nerve Fiber Analyzer (NFA, Laser Diagnostic Technologies, San Diego, USA).
METHODS—Scanning laser polarimetry was performed on both eyes of a healthy anaesthetised adult primate (Macaca mulatta). The retinal nerve fibre layer thickness was measured in the eye with the best polarimetry image. A nerve fibre layer thickness map was scaled and aligned to a retardation map to permit correlation of retardation and thickness measurements.
RESULTS—Retinal nerve fibre layer thickness measurements could be satisfactorily aligned with corresponding retardation values at 216 locations. The overall correlation coefficient for nerve fibre layer thickness and retardation was r = 0.70 (n = 216, p <0.001). Regional comparison showed the best correlation (r = 0.76, n = 45, p <0.001) occurred inferior to the optic disc. Less positive but still highly significant correlations were seen superiorly and temporally (r = 0.52, n = 26, p = 0.007 and r = 0.49, n = 86, p = <0.001 respectively), with the lowest correlation occurring at the nasal aspect of the disc (r  = 0.06, n  = 67, p = 0.64).
CONCLUSIONS—In the primate eye, retinal nerve fibre layer thickness shows a positive correlation with retardation measurements obtained with the nerve fibre analyser. However, since the correlation coefficient varied around the optic disc, further evaluation of the device is advised before its routine clinical use.

Keywords: nerve fibre layer; polarimetry; glaucoma; optic disc     

旋光法测定卡托普利及卡托普利片含量

目的：建立卡托普利及卡托普利片含量测定方法。方法：以乙醇为溶剂，采用旋光法测定卡托普利及卡托普利片含量。结果：卡托普利在5．0～30mg／ml范围内浓度与旋光度呈良好线性关系，回归方程C=-0．0095＋0．7654X，r=1．0000，平均回收率100．3％，RSD为0．18％（n=9）。结论：本法简便易行，结果准确，可作为卡托普利及卡托普利片的质控方法。