Fabrizio Zeri

Agreement and reliability in measuring central corneal thickness with a rotating Scheimpflug-Placido system and ultrasound pachymetry.

PURPOSE We compare the agreement and the reliability in measuring central corneal thickness (CCT) using two different technologies. METHOD The right eyes of 35 healthy individuals who had a negative history of ophthalmic disease, or ocular surgery were examined. The CCT was determined sequentially with a rotating Scheimpflug camera (Sirius; CSO), and an ultrasound pachymeter (P-1; Takagi). For statistical analysis, we used the methods suggested by Bland and Altman. RESULTS The mean values of CCT obtained from Sirius, and ultrasound were 537±28μm, and 550±35μm, respectively. There was a high correlation between Sirius and ultrasound (r=0.92; p<0.001), but the difference between the two measurements was statistically significant (t=-5.7; p<0.00001). The precision of Sirius and ultrasound were 9.4 and 15.9μm; repeatability 13.3 and 22.4μm, and coefficient of variation 0.9% and 1.5%, respectively. The intraclass correlation coefficient was 0.97 for Sirius and 0.95 for ultrasound. CONCLUSIONS The average difference between corneal thickness measured with Sirius and ultrasound pachymetry was small but clinically significant. This means that the two instruments cannot be used interchangeably. Sirius showed precision and repeatability almost twice as much as ultrasound pachymetry. Confidence interval of 13.3μm for Sirius can show variations in corneal thickness with an uncertainty value lower than 2.5% in 95% of cases. The simplicity of use, the possibility to obtain pachymetric maps, and less invasiveness make this instrument potentially useful in contact lens practice.

Ocular dominance stability and reading skill: a controversial relationship.

Purpose. Evidence is mixed concerning the relationship between stability of ocular dominance and reading deficits. Contrasting results may be due to the use of different tests of dominance, different samples of readers, and different scoring methods. The aim of this study was to investigate the relationship among ocular dominance, general visual abilities, and reading performance, and to evaluate the consistency and reliability of different tests of ocular dominance and the effects of different types of eye dominance scoring. Methods. In a group of young adults, we measured: (a) main optometric parameters; (b) reading time and accuracy; and (c) ocular dominance in two sighting and four motor tests. Dominance was determined using different scoring methods (relative, absolute, and binary scores). Results. All dominance tests showed good levels of internal reliability. Sighting tests were consistent regardless of the scoring method, and all participants had stable dominance. Three of four motor tests were moderately consistent when dominance was measured with relative scores but not when it was measured with absolute or binary scores. No relationship was found between stability of dominance and reading performance, regardless of the type of test or scoring method. No systematic pattern of correlation was found between binocular vision variables and dominance measures. Conclusions. Choosing the type of motor test to measure ocular dominance is crucial, because the level of consistency among tests is low to moderate. Furthermore, motor tests were not correlated with reading performances. Present results suggest caution when trying to link reading difficulties with specific profiles of ocular dominance.

The effect of hydrogel and silicone hydrogel contact lenses on the measurement of intraocular pressure with rebound tonometry

PURPOSE To assess the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) and silicone hydrogel (senofilcon A) contact lenses (CLs) of different powers. METHODS The experimental group comprised 36 subjects (19 male, 17 female). IOP measurements were undertaken on the subjects right eyes in random order using a rebound tonometer (ICare). The CLs had powers of +2.00D, -2.00D and -6.00D. Six measurements were taken over each contact lens and also before and after the CLs had been worn. RESULTS A good correlation was found between IOP measurements with and without CLs (all r≥0.80; p<0.05). Bland Altman plots did not show any significant trend in the difference in IOP readings with and without CLs as a function of IOP value. A two-way ANOVA revealed a significant effect of material and power (p<0.01) but no interaction. All the comparisons between the measurements without CLs and with hydrogel CLs were significant (p<0.01). The comparisons with silicone hydrogel CLs were not significant. CONCLUSIONS Rebound tonometry can be reliably performed over silicone hydrogel CLs. With hydrogel CLs, the measurements were lower than those without CLs. However, despite the fact that these differences were statistically significant, their clinical significance was minimal.

Visual discomfort while watching stereoscopic three-dimensional movies at the cinema

This study investigates discomfort symptoms while watching Stereoscopic three‐dimensional (S3D) movies in the ‘real’ condition of a cinema. In particular, it had two main objectives: to evaluate the presence and nature of visual discomfort while watching S3D movies, and to compare visual symptoms during S3D and 2D viewing.

Attitudes towards contact lenses: A comparative study of teenagers and their parents

PURPOSE This two-phase survey aimed to identify the beliefs and attitudes that create a barrier towards contact lens (CL) fitting among adolescents (aged 12-18 years) and their parents attending eye care practitioner clinics in Italy (phase 1) and Iberia (Spain and Portugal; phase 2). In phase 2, the sample was further focused, by limiting it to those adolescents who did not already wear CL. METHODS The extent to which CL satisfy aesthetic, visual, and practical needs and their effectiveness, safety, and comfort in the general population and in adolescents was rated by respondents on a 5-point Likert scale. RESULTS In phase 1, approximately one-third of adolescents (n=146) and parents (n=114) were CL wearers. Most adolescents (77.5% of 223) and parents (66.2% of 230) expressed a high interest in CL use in phase 2 despite none of the adolescents currently wearing CL. Parents, but not adolescents, perceived that CL were significantly less safe in adolescents than in the general population (p<0.05) in phases 1 and 2. Across both phases, adolescents and parents agreed that CL met an aesthetic need in adolescents (p<0.05 versus general population). Among 50% of parents (mainly mothers), significant concerns regarding CL were difficulties following instructions and taking care of the CL and potential eye damage, which, in mothers, led them to show less agreement towards CL use by the adolescent (p<0.001). CONCLUSIONS These findings highlight an essential need for improved education on CL use in the population.

Immediate cortical adaptation in visual and non-visual areas functions induced by monovision

Monovision is an optical correction for presbyopes that consists of correcting one eye for far distance and the other for near distance, creating a superimposition of an in‐focus with a blurred image. Brain adaptation to monovision was studied in unexperienced observers by measuring visual evoked potentials from 64‐channels. The first clear effect of monovision on visual evoked potentials was the C1 amplitude reduction, indicating that the unilateral blurring induced by monovision reduces feed‐forward activity in primary visual area. Monovision led also to an increased amplitude of the P1 and pP1 components, with the latter originating in prefrontal regions. This effect probably works as an attentional compensatory activity used to compensate for the degraded V1 signal.

An Italian translation and validation of the Near Activity Visual Questionnaire (NAVQ)

Purpose To validate the Near Activity Vision Questionnaire (NAVQ) in Italian to allow the assessment of presbyopia corrections in Italian-speaking patients. Methods An Italian version of the NAVQ was arranged through several steps: an initial forward translation (from English to Italian), a backward translation (from Italian to English), and finally a consensual version to check against the original NAVQ. This prospective study enrolled native Italian-speaking presbyopic patients with corrected distance visual acuity of 0.20 logMAR or better in each eye and free of ocular anomalies. Six different groups of patients were asked to complete the questionnaire: emerging presbyopic patients, reading spectacle users, multifocal spectacle users, multifocal contact lens (CL) wearers, monovision CL wearers, and monofocal intraocular lens patients. Subjects were asked to answer the questionnaire again 2 weeks after the first completion. Results A total of 207 subjects completed the questionnaire. Data analysis showed good internal consistency (Cronbach α = 0.93) and factorial validity with only one factor explaining 62.0% of the variance. Test-retest reliability was extremely good (ICC = 0.92) as well as discriminatory power of the questionnaires ability to discriminate between subjects with different forms of presbyopic correction. Conclusions The Italian version of the NAVQ matches the properties of the original English version. It is a valid instrument to evaluate near activity visual quality of presbyopic Italian speakers.

Hyperferritinemia-cataract syndrome: Long-term ophthalmic observations in an Italian family.

ABSTRACT Background: Hyperferritinemia-cataract syndrome (HCS) is a rare Mendelian condition characterized by bilateral cataract and high levels of serum ferritin in the absence of iron overload. Methods: HCS was diagnosed in three adult siblings. In two of them it was possible to assess lens changes initially in 1995 and again in 2013. Serum ferritin, iron, transferrin concentrations and transferrin saturation percentage were also measured, and the Iron Responsive Element (IRE) region of the L-ferritin gene (FTL) was studied. Results: Serum ferritin concentrations were considerably elevated while serum iron, transferrin and transferrin saturation levels were within the normal range in each sibling. Cataract changes in our patients were consistent with those previously reported in the literature. Progression of the cataract, an aspect of few studies in this syndrome, appeared to be quite limited in extent. The heterozygous +32G to T (-168G>T) substitution in the IRE of the FTL gene was detected in this family. Conclusions: Ophthalmic and biochemical studies together with genetic testing confirmed HCS in three family members. Although the disorder has been extensively described in recent years, little is known regarding cataract evolution over time. In our cases, lens evaluations encompassed many years, identified bilateral cataract of typical morphology and supported the hypothesis that this unique clinical feature of the disease tends to be slowly progressive in nature, at least in adults.

Measuring fixation disparity with infrared eye-trackers

Fixation disparity, that is, misalignment of the gaze direction of both eyes, may be observed in static conditions (through standard optometric evaluation) and dynamic conditions (through eye movement recording). A computation method is presented to determine vergence angles and fixation disparity from gaze positions as commonly recorded by infrared eye-trackers when a participant looks at a personal computer (PC) screen. Eye-tracking devices provide gaze position in coordinates relative to the bidimensional screen surface. From these data, vergence angles can be calculated by trigonometric triangulations; fixation disparity is then calculated from the vergence angles. The application of the procedure to the recordings of one participant is described. To control for the effective alignment of the two eyes on the target during binocular calibration, a procedure based on the dichoptic presentation of nonius lines was used. The recordings confirm that computation and the dichoptic calibration procedures ensure reliable measures of vergence and fixation disparity. The usefulness of this approach with infrared recording of eye position is discussed.

Pattern of reading eye movements during monovision contact lens wear in presbyopes

Monovision can be used as a method to correct presbyopia with contact lenses (CL) but its effect on reading behavior is still poorly understood. In this study eye movements (EM) were recorded in fifteen presbyopic participants, naïve to monovision, whilst they read arrays of words, non-words, and text passages to assess whether monovision affected their reading. Three conditions were compared, using daily disposable CLs: baseline (near correction in both eyes), conventional monovision (distance correction in the dominant eye, near correction in the non-dominant eye), and crossed monovision (the reversal of conventional monovision). Behavioral measures (reading speed and accuracy) and EM parameters (single fixation duration, number of fixations, dwell time per item, percentage of regressions, and percentage of skipped items) were analyzed. When reading passages, no differences in behavioral and EM measures were seen in any comparison of the three conditions. The number of fixations and dwell time significantly increased for both monovision and crossed monovision with respect to baseline only with word and non-word arrays. It appears that monovision did not appreciably alter visual processing when reading meaningful texts but some limited stress of the EM pattern was observed only with arrays of unrelated or meaningless items under monovision, which require the reader to have more in-depth controlled visual processing.