Consensus paper on postural dysfunction: recommendations for prevention, diagnosis and therapy.

Good fundamentals of posture and balance are essential for the efficient performance of both simple daily tasks and more complex movement patterns. In particular, postural balance is the ability to keep the body in equilibrium and to regain balance after the shift of body segments: postural control mechanisms of integration of the visual, vestibular and foot afferential channels contribute to this. This document provides recommendations based on scientific evidence, clinical practice, and consensus between experts concerning the prevention, diagnosis, and treatment of postural dysfunction at the three stages of life as the developmental age, adult age, and old age > 65 years and follows the "National Guidelines on Classification and Measuring of Posture and its Dysfunctions" per the Italian Ministry of Health (December 2017). The paper answers four main questions: i) "Which measures can be adopted to prevent postural dysfunctions?" ii) "What can we do in order to make a correct diagnosis of postural dysfunction?" iii) "What are the correct treatment programs for postural dysfunctions?" iv) Which professional competencies and experiences are useful for preventing, diagnosing and treating postural dysfunctions? By the Consensus of the Experts and the scientific evidence, emerge that the approach to postural dysfunctions requires a multidisciplinary and interdisciplinary team. Furthermore, rehabilitation treatment interventions must be specific to the age groups that have been indicated, to consider the integration of the main systems and subsystems of postural control that change with age.

Correlation in foveal thickness measurements between spectral-domain and time-domain optical coherence tomography in normal individuals.

PURPOSE: To compare a time-domain (Stratus) and a spectral-domain (Spectralis) optical coherence tomography (OCT) device in assessing foveal thickness in healthy subjects. METHODS: In this observational study 40 healthy subjects (40 eyes) underwent Stratus OCT and Spectralis OCT measurements of foveal thickness using three consecutive horizontal and vertical B-scan. Paired samples t-test was used to compare means between Stratus and Spectralis OCT measurements. Coefficient of variation (CoV) was used to compare dispersion in datasets. Pearson's correlation coefficient was used to quantify linear relation between Spectralis and Stratus OCT measurements. To assess agreement between Spectralis and Stratus OCT foveal thickness measurements, the Bland and Altman plots were used. RESULTS: Sample age ranged from 19 to 49 years (mean 33.25, standard deviation (SD) +/-4.22). The Spectralis OCT foveal thickness measurements resulted significantly higher than those obtained with Stratus OCT (227.64+/-11.74 vs 144.36+/-12.25 microm, and 227.63+/-11.43 vs 144.92+/-12.34 microm, for horizontal and vertical foveal thickness, respectively) (P<0.05). Coefficient of variations were 5.16 and 5.02% using Spectralis OCT, and 8.49 and 8.51% using Stratus OCT. Mean Spectralis/Stratus ratio was 1.58 for both horizontal and vertical measurements. A linear relation between the two technologies was found (r(horiz)=0.899 and r(vert)=0.869) (P<0.001). CONCLUSIONS: A good correlation between Stratus and Spectralis OCT foveal measurements was found, independently of retinal thickness. This preliminary study suggests the existence of a conversion factor between Stratus and Spectralis OCT when measuring healthy foveal thickness.

Conjunctival characteristics in primary open-angle glaucoma and modifications induced by trabeculectomy with mitomycin C: an in vivo confocal microscopy study.

OBJECTIVES: To evaluate the microscopic epithelial features seen with in vivo confocal microscopy (IVCM) of bulbar conjunctiva in glaucomatous patients undergoing trabeculectomy with mitomycin C in order to elucidate modifications. METHODS: Fifteen eyes of 15 consecutive Caucasian patients affected with primary open-angle glaucoma (POAG) undergoing trabeculectomy and 10 eyes of 10 glaucomatous patients (controls) under medical therapy were enrolled. Eyes were examined using a digital confocal laser-scanning microscope (HRT II Rostock Cornea Module) at baseline and after 6 weeks. The mean microcyst density (MMD: cysts/mm(2)) and microcyst area (MMA: mum(2)) were the main outcome measurements. RESULTS: Before surgery, the mean intraocular pressure (IOP) was 25.1 (SD 3.2) mm Hg. MMD and MMA were 22.4 (11.9) and 4696.0 (3608.1), respectively. After trabeculectomy, the mean IOP was 16.1 (1.7) mm Hg. A marked increase in both MMD and MMA, with values of 103.1 (22.6) and 29 489.3 (12 954.9), respectively, was observed. In the control group at baseline, the mean IOP was 15.7 (1.9) mm Hg, and the microcyst parameters did not differ from eyes undergoing filtering surgery. After 6 weeks, IOP and microcysts parameters did not show any significant modifications. CONCLUSIONS: Conjunctival epithelial microcysts were demonstrable in glaucomatous eyes under medical therapy prior to trabeculectomy. The filtering procedure increased microcysts density and surface at bleb site indicating a marked postsurgical enhancement of aqueous filtration across conjunctiva.

The effect of pneumatic trabeculoplasty on intraocular pressure: the results of a 6-month, open-label, multicenter study.

PURPOSE: To evaluate the effects of pneumatic trabeculoplasty (PNT) in ocular hypertension and glaucoma subjects. METHODS: A total of 63 consecutive subjects, either treated (79%) or untreated (21%), with intraocular pressure (IOP) between 20 and 25 mmHg were enrolled; the eye with higher IOP (or, in case of identical IOP, worse visual field) was treated with PNT, with the fellow eye used as control. Subjects underwent a baseline evaluation the day before treatment, two PNT treatments at day 0 and 7, visits at day 1, 8, 14, and at each month until the end of the study, which lasted 6 months. Safety was addressed at all visits; an IOP curve (at 8 and 10 AM, 2 and 4 PM) was obtained at baseline and during monthly visits. RESULTS: In PNT eyes, baseline IOP was 22.2-/+1.6 mmHg. Following PNT a statistically significant reduction of IOP occurred at all visits (p<0.0001), with a mean decrease ranging from -2.7-/+2.5 (-11.9-/+10.8%) to -3.6-/+2.6 mmHg (-16.0-/+11.6%); mean reduction was 12.8-/+11.5%. Although IOP diminished also in the control eyes after baseline (p<0.05), the change in IOP was significantly higher in PNT group at each visit (p<0.05). Mild side effects were experienced by 76% of subjects and they all resolved without sequelae. CONCLUSIONS: The results suggest the effect of this procedure in reducing IOP in glaucoma and ocular hypertensive subjects.

An in vivo confocal microscopy and impression cytology analysis of preserved and unpreserved levobunolol-induced conjunctival changes.

PURPOSE: To provide an in vivo confocal microscopy (IVCM) and impression cytology analysis of preserved-and unpreserved levobunolol-induced changes of conjunctival epithelium. METHODS: 27 eyes of 27 patients were consecutively randomized to receive preserved or unpreserved levobunolol; all patients had a recent diagnosis of primary open angle glaucoma (POAG) or ocular hypertension and were not previously treated with topical medications. IVCM and impression cytology were performed before and after six months of therapy. Goblet cells density and a conjunctival epithelium regularity index were considered in the IVCM analysis, whereas impression cytology specimens were graded and scored in accordance with Nelson's method. RESULTS: After six months of therapy, IVCM and impression cytology parameters showed significant differences with respect to baseline in both groups (p<0.001); significant differences were also found between the two groups (p<0.001). The IVCM analysis showed a goblet cells density reduction (61% and 17% from baseline, respectively in group 1 and 2) (p<0.001) and an higher index of epithelial regularity (p<0.001) in both groups; the impression cytology analysis showed an higher score in both groups (p<0.001). CONCLUSIONS: All the IVCM and impression cytology parameters correlated well with the conjunctival modifications induced by the topical therapy, suggesting the less toxicity of unpreserved drugs.

Amniotic membrane transplantation for the management of corneal epithelial defects: an in vivo confocal microscopic study.

PURPOSE: To evaluate amniotic membrane (AM) tissue morphology and corneal epithelial healing in human eyes after amniotic membrane transplantation (AMT), using laser scanning in vivo confocal microscopy (IVCM). PATIENTS AND METHODS: Twenty eyes of 20 patients, treated with single layer epithelial side up AMT for chemical burns in the acute stage (n = 8) and persistent corneal epithelial defect (n = 12) were studied by serial IVCM post-AMT until complete re-epithelisation. Changes in morphology of transplanted amniotic tissue and healing corneal epithelium were noted. AM and corneal epithelial cell density was calculated using image-analysis software. RESULTS: IVCM enabled visualisation of transplanted AM and of regenerating epithelial cells under the AM. The mean AM epithelial cell density, 1 day after transplant, was 4613 (SD 380) cells/mm2. The average AM epithelial thickness was 35 (4) microm, while the AM stromal thickness was 116 (31) microm. The amniotic stroma appeared to be composed of a superficial dense fibrous layer and a deeper loose reticular network of fibres. Amniotic epithelium was lost within 15 days of transplant, and complete re-epithelisation of the corneal surface was achieved between 1 and 4 weeks. CONCLUSIONS: Laser scanning IVCM is a useful method for evaluating AM tissue morphology, degradation and corneal epithelial healing after AMT for different clinical indications. When the amniotic membrane acts as a patch, that is epithelial cells migrate under rather than over the membrane, the membrane disintegrates and is lost.

Fixation patterns evaluation by means of MP-1 microperimeter in microstrabismic children treated for unilateral amblyopia.

PURPOSE: The aim of the study was to evaluate the fixation patterns of microstrabismic children previously treated for unilateral amblyopia. METHODS: Thirty-three children (mean age 7.3+/-1.5 years) were included in the study. Visual acuity (VA) was measured using the Early Treatment of Diabetic Retinopathy Study charts. Fixationwas assessed by MP-1 microperimeter. Differences in position and stability of fixation between the fellow and the microstrabismic eyes were calculated by using the percentage of the preferred fixation points within central fixation and the percentage of the fixation points within target fixation, respectively. For statistical analysis Mann-Whitney test was used. To evaluate the influence of age and duration of anti-amblyopic treatment on microstrabismic eyes fixation, linear regression analysis was performed. RESULTS: In the microstrabismic eyes VA was significantly reduced when compared to the fellow eyes (0.1236+/-0.0204 vs 0.0042+/-0.0032 logMAR; p<0.001). Position and stability of fixation were significantly better in the fellow eyes (93.21+/-0.65% vs 70.91+/-4.80%; p=0.002, and 89.88+/-0.94% vs 71.73+/-2.94%; p<0.001, respectively). A significant correlation was found between fixation stability and both the duration of anti-amblyopic treatment and pretreatment VA (p=0.024 and p=0.009, respectively) and between fixation centrality and pretreatment VA (p<0.001). CONCLUSIONS: VA, centrality, and stability of fixation were significantly impaired in the microstrabismic eyes. Pretreatment VA was a risk factor for fixation impairment. The severity of fixation stability impairment was linked to the duration of anti-amblyopic treatment.

Immunohistochemical findings in epiretinal membrane after long-term silicone oil tamponade: case report.

PURPOSE: To report pre- and post-operative macular optical coherence tomography (OCT) and immunohistochemical findings in a case of long-lasting silicone oil tamponade followed by silicone oil removal and epimacular membrane peeling. METHODS: A 69-year-old man with long-standing silicone oil tamponade and an epiretinal membrane at the posterior pole in his right eye (RE) underwent silicone oil/BSS exchange with epiretinal membrane peeling. Preoperatively, RE best-corrected visual acuity was 20/200 and macular OCT examination revealed a small increase in foveal thickness (250 microm) with the appearance of a linear hyper-reflective signal at the foveal vitreoretinal interface and a thicker (440 microm) hyperreflective finding causing posterior shadowing at the vitreoretinal interface inferiorly to the fovea. Histopathologic and immunohistochemical study of the specimen including the epiretinal membrane was performed. RESULTS: Light microscopy revealed extensive rounded empty spaces interpreted as silicone oil bubbles in the preretinal membrane. Macrophages marker (CD68) positive staining cells were found surrounding the empty spaces within the preretinal membrane and several empty spaces were observed intracellularly within macrophage cytoplasm. Thirty days after surgery best-corrected visual acuity was 20/60 and OCT examination showed an evident decrease in foveal thickness (220 microm) with the disappearance of any hyper-reflective signal at the vitreoretinal interface referable to an epiretinal membrane. CONCLUSIONS: The immunohistochemical study showed both silicone oil droplets and macrophagic cells embedded in the epiretinal membrane. Postoperative OCT demonstrated retinal recovery after silicone oil removal and epiretinal membrane peeling, thus justifying an unexpected visual acuity recovery despite the very long term tamponade.

Zyoptix wavefront-guided versus standard photorefractive keratectomy (PRK) in low and moderate myopia: randomized controlled 6-month study.

PURPOSE: To evaluate the refractive and aberrometric outcome of wavefront-guided photorefractive keratectomy (PRK) compared to standard PRK in myopic patients. METHODS: Fifty-six eyes of 56 patients were included in the study and were randomly divided into two groups. The study group consisted of 28 eyes with a mean spherical equivalent (SE) of -2.25+/-0.76 diopters (D) (range: -1.5 to -3.5 D) treated with wavefront-guided PRK using the Zywave ablation profile and the Bausch & Lomb Technolas 217z excimer laser (Zyoptix system) and the control group included 28 eyes with a SE of -2.35+/-1.01 D (range: -1.5 to -3.5 D) treated with standard PRK (PlanoScan ablation) using the same laser. A Zywave aberrometer was used to analyze and calculate the root-mean-square (RMS) of total high order aberrations (HOA) and Zernike coefficients of third and fourth order before and after (over a 6-month follow-up period) surgery in both groups. Preoperative and postoperative SE, un-corrected visual acuity (UCVA), and best-corrected visual acuity (BCVA) were evaluated in all cases. RESULTS: There was a high correlation between achieved and intended correction. The differences between the two treatment groups were not statistically significant for UCVA, BCVA, or SE cycloplegic refraction . Postoperatively the RMS value of high order aberrations was raised in both groups. At 6-month control, on average it increased by a factor of 1.17 in the Zyoptix PRK group and 1.54 in the PlanoScan PRK group (p=0.22). In the Zyoptix group there was a decrease of coma aberration, while in the PlanoScan group this third order aberration increased. The difference between postoperative and preoperative values between the two groups was statistically significant for coma aberration (p=0.013). No statistically significant difference was observed for spherical-like aberration between the two groups. In the study group eyes with a low amount of preoperative aberrations (HOA RMS lower than the median value; <0.28 microm) showed an increase of HOA RMS while eyes with RMS higher than 0.28 microm showed a decrease (p<0.05). CONCLUSIONS: Zyoptix wavefront-guided PRK is as safe and efficacious for the correction of myopia and myopic astigmatism as PlanoScan PRK. Moreover this technique induces a smaller increase of third order coma aberration compared to standard PRK. The use of Zyoptix wavefront-guided PRK is particularly indicated in eyes with higher preoperative RMS values.

Custom measurement of retinal nerve fiber layer thickness using STRATUS OCT in normal eyes.

PURPOSE: To evaluate variability of retinal nerve fiber layer (RNFL) thickness measurements in normal eyes and their correlation with optic disc diameter by using two different scan options of the ultimate commercial optical coherence tomography (OCT) unit (STRATUS OCT, Carl Zeiss Meditec, Inc., Dublin, CA). METHODS: In this observational case series and instrument validation study 30 eyes of 30 normal subjects were enrolled. Each eye underwent optic disc vertical diameter measurement by means of both stereoscopic photography and planimetry and OCT; RNFL thickness measurements were performed using OCT. Three repetitions of two series of scans were performed. Each eye was scanned at two different options (RNFL thickness 3.4 and Nerve Head Circle). For each option descriptive statistics, analysis of variance, intraclass correlation coefficients (ICCs), and coefficients of variation (COVs) were calculated. To verify the correlation between the two methods of optic disc diameter assessment and to study the influence of optic disc diameter on RNFL measurement using the two different OCT options, Pearson's correlation coefficients were calculated. RESULTS: Optic disc diameter length ranged from 1.47 to 2.04 mm (mean 1.709 mm, SD +/- 0.147) with stereoscopic photographs, and from 1.47 to 2.02 mm (mean 1.703 mm, SD +/- 0.143) with OCT (Pearson correlation coefficient 0.999, p<0.001). Mean RNFL thickness was 89.29 mm (SD +/- 10.80 mm) using the RNFL thickness 3.4 scanning option and 89.88 mm (SD +/- 1.72 mm) using the Nerve Head Circle protocol (Pearson correlation coefficient 0.065, p=0.734). The intersubject variance is higher using the RNFL thickness 3.4 option than using the NHC protocol (sum of square: 1,014,760 vs. 25,741) (p<0.001); the intrasubject variance is very similar in the two groups (2,372 vs 2,360) (p=NS). The ICC is 99.89% when using the RNFL thickness 3.4 option, 95.62% with the NHC protocol (p=NS). COVs were 12.10% and 1.91% by using RNFL thickness 3.4 and Nerve Head Circle option, respectively. Pearson's correlation coefficient was 0.988 (p<0.001) when comparing optic disc diameter and RNFL thickness by using the RNFL thickness 3.4 option and -0.016 (p=0.932) when comparing optic disc diameter and RNFL thickness by using the Nerve Head Circle option. CONCLUSIONS: These results suggest that both scan options give good RNFL thickness measurement reproducibility; the use of the Nerve Head Circle option leads to less interindividual variability and can minimize the effect of differences in optic disc diameter on RNFL thickness measurements in normal subjects.

Optical coherence tomography and fundus microperimetry imaging of spontaneous closure of traumatic macular hole: a case report.

PURPOSE: To report a case of spontaneous closure of traumatic macular hole in a young patient followed using optical coherence tomography (OCT) and fundus microperimetry. METHODS/RESULTS: In the right eye of a 10-year-old child, a traumatic macular hole was observed to spontaneously resolve 18 weeks after blunt trauma. Initially, visual acuity in the right eye was 20/200 and OCT examination showed a 200 microm-diameter full-thickness macular hole with perifoveal edema. Fundus microperimetry examination showed an evident decrease in retinal sensitivity within the macular hole and in the upper macular region where an area of commotio retinae was clearly visible. During follow-up OCT demonstrated the appearance of a band of tissue linking the inferior edge of the hole to the foveal retinal pigment epithelium and at the bottom of the hole the presence of hyperreflective (glial) material. Eighteen weeks after trauma right eye visual acuity had improved to 20/25, OCT examination showed a restored foveal depression, and fundus microperimetry demonstrated an increase in foveal sensitivity. CONCLUSIONS: Both OCT and fundus microperimetry were useful tools for following the favorable course in a case of spontaneous closure of traumatic macular hole in a young patient. During follow-up OCT examinations were able to demonstrate the course of macular hole closure.

Optical coherence tomography imaging of surgical resolution of bilateral vitreomacular traction syndrome related to incomplete posterior vitreoschisis: a case report.

PURPOSE: To report a case of surgical resolution of bilateral vitreomacular traction syndrome related to incomplete posterior vitreoschisis as documented by optical coherence tomography (Stratus OCT, Carl Zeiss Meditec, Dublin, CA). CASE REPORT: In both eyes of a 72-year-old man with bilateral blurred vision, OCT examination disclosed a relevant increase in mean foveal thickness (right eye = 714 microm; left eye = 757 microm) due to a vitreomacular traction syndrome. At the edges of the most highly elevated area of vitreo-macular traction, OCT scans showed a characteristic splitting of the hyperreflective signal in both eyes, usually identified as posterior vitreous cortex. Both eyes underwent vitrectomy with epiretinal membrane peeling. Postoperative OCT examination showed vitreomacular traction resolution in both eyes with an evident decrease in mean foveal thickness (right eye = 364 microm; left eye = 335 microm). Right visual acuity improved from 20/200 to 20/50; left visual acuity changed from 20/150 to 20/40. CONCLUSIONS: OCT was a useful tool in identifying an unusual case of bilateral vitreomacular traction syndrome linked to incomplete posterior vitreoschisis and following a favorable course after surgical management.

Optical coherence tomography and retinal thickness analyzer features of spontaneous resolution of vitreomacular traction syndrome: a case report.

PURPOSE: To report optical coherence tomography (OCT) and retinal thickness analyzer (RTA) findings in a case of spontaneous resolution of vitreomacular traction syndrome. METHODS: Qualitative and quantitative analysis of the macular region was performed with OCT and RTA. RESULTS: In the left eye of a 34-year-old woman with blurred vision, OCT and RTA examination showed a discrete linear signal anterior to the retina with attachment at the macula and secondary cystoid macular changes. OCT and RTA examination showed an increase in macular thickness (350 microm). Six months later the patient showed a spontaneous complete recovery of visual acuity. Vitreomacular traction and cystoid changes were no longer detectable at OCT and RTA examination; retinal thickness was normal (205 microm) and a posterior vitreous detachment was visible. CONCLUSIONS: Both OCT and RTA were useful tools for making the diagnosis of vitreomacular traction syndrome and demonstrating the effect of spontaneous vitreomacular traction release with resolution of cystoid macular changes.

Management of scleral rupture during retinal detachment surgery: a case report.

PURPOSE: Rupture of the sclera occurring during retinal detachment surgery is generally associated with unfavourable anatomic and visual outcomes. Re-operation after a failed scleral buckle procedure and pre-existing scleral thinning are considered the main risk factors for scleral rupture. CASE REPORT: We describe the management and the favourable outcome of a case of scleral rupture in a 71-year-old woman during re-operation for retinal detachment. CONCLUSIONS: We managed this case of scleral rupture in accordance with current indications concerning the anatomical recovery, by scleral suture and patch graft, restoring IOP by gas tamponade. The positive outcome was partly related to the prompt closure of the retinal hole which led to reattachment, and partly to favourable events such as the moderate intensity of vitreous hemorrhage and the lack of any more serious intraoperative and postoperative complications.

Morphological evaluation of Schnyder's central crystalline dystrophy by confocal microscopy before and after phototherapeutic keratectomy.

A 29-year-old man with Schnyder's central crystalline dystrophy was treated with phototherapeutic keratectomy (PTK) in his right eye. Ocular examination revealed abnormal deposits of cholesterol and lipid within the corneal stroma (appearing as crystalline spindle-shaped deposits), high myopia, phakic anterior chamber intraocular lens implantation, and myopic macular degeneration in both eyes. Phototherapeutic keratectomy ablation to a central zone of 7.0 mm and a depth of 96 microm was performed with an Aesculap Meditec MEL-70 excimer laser. Confocal microscopy performed before PTK showed multiple deposits of large, brightly reflective crystalline material extending from the anterior to the mid stroma. The Z-scan curves revealed that the highest density of crystalline deposits was located within the first 140 microm of corneal depth. Six months after PTK, confocal microscopy showed a markedly decreased density of corneal crystalline deposits in the anterior stroma.

In vivo confocal microscopy of patients with amiodarone-induced keratopathy.

PURPOSE: To describe the corneal findings in patients with amiodarone-induced keratopathy by means of in vivo confocal microscopy. METHODS: Twenty-two eyes of 11 patients (eight men and three women) receiving amiodarone therapy and 20 eyes of 10 healthy sex-and age-matched control subjects were selected for confocal microscopic examination. The patients were examined by use of a scanning slit corneal confocal microscope (Confoscan 2.0). Five complete scans of the entire cornea were performed for each eye with a total examination time of less than 5 minutes. RESULTS: All patients receiving amiodarone showed the presence of high reflective, bright intracellular inclusions in the epithelial layers. These findings were more evident within the basal cell layers. In the eyes with advanced keratopathy (stages 2 and 3), bright microdots were detectable within the anterior and posterior stroma and on the endothelial cell layer. In the anterior stroma, the keratocyte density in the treated group was reduced compared with values of the control group (p < 0.001), and a markedly irregular aspect of the stromal nerve fibers was found. The main characteristic of this nerve irregularity was represented by the clew-shaped appearance of the nerve trunks. CONCLUSION: Detailed examination of corneal structure by confocal microscopy shows that amiodarone keratopathy in long-term treated patients presents some findings that are consistent with higher toxicity than was expected and that involve the deep corneal layers.

Reproducibility of nerve fiber layer thickness measurements using optical coherence tomography in silicone oil-filled eyes.

PURPOSE: To evaluate the reproducibility of nerve fiber layer (NFL) thickness measurements by optical coherence tomography (OCT) in individuals with silicone oil-filled eyes. METHODS: Eighteen patients who had undergone pars plana vitrectomy and silicone oil tamponade for retinal detachment were enrolled in a prospective, case-controlled clinical study. Each patient underwent OCT measurement of NFL thickness. Five repetitions of a series of scans on five separate occasions within a 0.5-month period were performed. Each eye was scanned at two different nerve head programs [radius (R) = 1.5 and R = 1.73]. The contralateral healthy eye was used as control. For each option (R = 1.5 and R = 1.73) and region (superior, inferior, temporal, nasal and overall mean), variance components and intraclass correlation coefficients (ICCs) were determined using repeated-measures regression. In these models, NFL thickness, as measured by OCT, was considered to have three variance components: intersubject, intervisit (within subject, between dates), and intravisit (within subject, within date). The ICC (intersubject variance/total variance) was used as a measure of reliability. RESULTS: The contralateral healthy eye provided a higher degree of reproducibility than the silicone oil-filled eye (p = 0.0001). Reproducibility was higher in a given eye on a given visit than from visit to visit. Reproducibility as measured by ICCs was as follows: R = 1.5, 0.54/0.30 (control eyes/silicone oil-filled eyes); R = 1.73, 0.51/0.30. CONCLUSIONS: Reproducibility results for OCT measurement of NFL thickness are different in healthy eyes and silicone oil-filled eyes. NFL thickness measurement is not reliable in silicone oil-filled eyes.

Effect of photorefractive keratectomy for myopia on measurement of retinal nerve fiber layer thickness using optical coherence tomography.

PURPOSE: To evaluate the effect of excimer laser photorefractive keratectomy (PRK) on nerve fiber layer thickness measurements by optical coherence tomography in myopic eyes. METHODS: Twenty-two patients who had PRK for myopia underwent nerve fiber layer measurement by optical coherence tomography in both eyes before and 6 months after surgery in the first operated eye and before surgery in the fellow (control) eye, 6 months after the first PRK. Optical coherence tomography was performed with a Humphrey Optical Coherence Tomography Scanner. Each eye was scanned at the nerve head program radius of 1.5. For each of the optical coherence tomography parameters (average for each quadrant, superior, inferior, temporal, nasal; average for each clock hour; average over the entire cylindrical section), descriptive statistics were calculated. The difference between the observed change from the first to the second examination was calculated between the treated and the control eye. Individual mean differences were tested with Student's t-test. Hotelling's T-squared generalized means test was used to determine whether the set of mean differences was equal to zero. RESULTS: The average preoperative refractive error was -3.90+/-1.50 D in treated eyes and -3.89+/-1.50 D in control eyes (P = .81, Student's t-test). Mean achieved refractive correction was 3.70+/-1.70 D, corresponding to 48.1+/-22.1 microm of corneal ablation. No statistically significant difference was found in any measurement in the treated eye compared with the untreated control eye. CONCLUSIONS: At 6 months postoperatively, photorefractive keratectomy for moderate myopia that resulted in clear corneas did not affect nerve fiber layer thickness measurements, as obtained by optical coherence tomography.