The application of a new continuous functional visual acuity measurement system in dry eye syndromes

To evaluate the efficacy and safety of new moist cool air device (MCAD) for ocular symptoms, tear film stability and ocular surface status in office workers with dry eye disease (DED). In this prospective single-centre clinical trial, 40 eyes of 20 patients with DED were recruited and randomly divided into two groups (group with MCAD exposure and group without MCAD). All subjects are visual display terminals (VDTs) workers spending at least 4 h/day in front of VDTs. Patients using MCAD underwent moist air applications for 4 h/day for a total of five working weekdays during VDT works at their offices. The other group of patients performed their VDT work without moist cool air device exposure. The change in symptoms of ocular surface (OS) dryness, fatigue and discomfort was evaluated using visual analogue scale (VAS) scores. Changes in visual function, tear functions and ocular surface status were evaluated using best-corrected visual acuity (BCVA), the functional visual acuity (FVA) test, blink rate, BUT measurements, strip meniscometry (SM), tear evaporation rate, fluorescein staining and rose bengal staining scores. Tear film lipid layer interferometry was also performed to assess the status of the lipid layer over the tear film. In addition, adverse events were recorded. In group with MCAD, symptoms of OS dryness during VDTs work, and FVA and BUT were significantly improved. SM and tear evaporation rate were significantly improved. There were no statistically significant differences on lipid layer stability and corneal staining scores in both groups. Blink rate was significantly increased in group without MCAD. No adverse events were reported during this trial. Moist cool air device use provided symptomatic relief of ocular dryness and improvement on tear stability in office workers with DED. This new device seems to be a safe and promising alternative in the treatment of DED.

To investigate the relation of functional visual acuity (FVA) measurements with dry eye test parameters and to compare the testing methods with and without blink suppression and anesthetic instillation. A prospective comparative case series. Thirty right eyes of 30 dry eye patients and 25 right eyes of 25 normal subjects seen at Keio University School of Medicine, Department of Ophthalmology were studied. FVA testing was performed using a FVA measurement system with two different approaches, one in which measurements were made under natural blinking conditions without topical anesthesia (FVA-N) and the other in which the measurements were made under the blink suppression condition with topical anesthetic eye drops (FVA-BS). Tear function examinations, such as the Schirmer test, tear film break-up time, and fluorescein and Rose Bengal vital staining as ocular surface evaluation, were performed. The mean logMAR FVA-N scores and logMAR Landolt visual acuity scores were significantly lower in the dry eye subjects than in the healthy controls (p<0.05), while there were no statistical differences between the logMAR FVA-BS scores of the dry eye subjects and those of the healthy controls. There was a significant correlation between the logMAR Landolt visual acuities and the logMAR FVA-N and logMAR FVA-BS scores. The FVA-N scores correlated significantly with tear quantities, tear stability and, especially, the ocular surface vital staining scores. FVA measurements performed under natural blinking significantly reflected the tear functions and ocular surface status of the eye and would appear to be a reliable method of FVA testing. FVA measurement is also an accurate predictor of dry eye status.

Functional Visual Acuity in Stevens-Johnson Syndrome

Dry eye (DE) causes irregularity of the ocular surface and reduces the quality of vision. An intact, regular tear film is essential for high-quality retinal images; however, visual tasks requiring sustained gazing can disrupt the tear film, eventually degrading visual function. A functional visual acuity (FVA) measurement system has been uniquely developed in Japan to evaluate visual function related to tear stability in patients with DE. FVA has been shown to correlate with optical quality. The system measures the change in visual acuity (VA) over time automatically in aqueous-deficient DE and short tear breakup tear film DE characterized by decreased tear stability and minimal epithelial damage. It is also useful to detect minimal visual deterioration correlated with minimal ocular surface abnormality and vision-related quality of life otherwise undetectable by conventional VA testing, to assess and quantify vision-related symptomatology, and to determine the efficacy of treatments for DE disease. Recently, its use has been expanded, such as for the analysis of visual function accompanying refractive surgery, contact lens, cataract and cataract-related disease, retinal disease, glaucoma, amblyopia, presbyopia, and vehicle driving. Its use has revealed that FVA reflects not only visual function related to tear dynamics, but also visual function related to quick recognition of the target. This simple, noninvasive, and sensitive FVA measurement system may be expected to be used worldwide.

To investigate the changes in functional visual acuity (VA) and higher order aberrations in dry eye patients. In this prospective comparative case series, 22 right eyes were classified into those with or without superficial punctate keratopathy (SPK) in the central cornea of 22 patients with Sjögren syndrome; 10 right eyes of 10 normal subjects served as the control. Serial measurements of VAs using a functional VA measurement system and higher order aberrations using a wavefront sensor were performed under blink-free conditions without topical anesthesia over a 10-second period. The parameters for each measurement were compared among the SPK-positive and -negative and normal groups. The correlation between those parameters was also analyzed. Dry eye with SPK showed significant deterioration of visual function and optical quality compared with dry eye without SPK and in normal eyes, as detected by both the visual maintenance ratio (VMR; P < 0.05) and the variation of VA (P < 0.05) and by comalike and total higher order aberrations (P < 0.05). Moreover, the severity of epithelial damage at the central cornea correlated significantly with VMR (P < 0.01) and variation of VA (P < 0.01) as well as comalike (P < 0.05) and total higher order aberrations (P < 0.05). The dry eye group without SPK showed minor visual deterioration compared with normal eyes, as detected only by VMR (P < 0.05). Optical disturbances at the central optical zone of the cornea in dry eye disease may affect visual performance. Functional VA measurement may be an applicable method of evaluating visual performance in dry eyes that is as efficient as wavefront aberration measurements.

Functional visual acuity (FVA) has been suggested to reflect an individual's performance in relation to certain daily activities involving visual tasks. The concept of FVA has been thought applicable to the detection of masked impairment of visual function in patients with dry eye who complain of decreased visual acuity despite normal conventional visual acuity. A stable tear-film layer over the surface of the cornea is essential for a smooth ocular surface and the formation of clear visual images. In dry eye, the ocular surface tends to dry out when normal blinking is suppressed during gazing, and patients with dry eye may have problems maintaining clear vision while gazing. The FVA measurement system is a device to measure changes in continuous visual acuity over time. Visual maintenance ratio (VMR) is the ratio between FVA and baseline visual acuity. FVA and VMR are indices for the assessment of functional vision. FVA has been thought applicable to the detection of changes in functional vision in relation to the tear film over the ocular surface. It may also be useful for the assessment of subjective visual complaints in diseases that do not involve dry eye.

To report the changes in functional visual acuity (FVA) in eyes with experimentally induced astigmatism. This study included 26 right eyes from 26 healthy participants (mean age: 27.0±4.4 years). After confirming best correction under cycloplegia, the cylinder power ×90° and ×180° (against-the-rule [ATR] and with-the-rule [WTR] astigmatism, respectively) were added with 0.50-diopter (D) steps, from 0.50 to 2.50 D. Conventional visual acuity (VA), FVA as measured by the FVA Measurement System (NIDEK Co Ltd), and 10% low-contrast visual acuity (LCVA) were measured with 3-mm artificial pupil under each condition. The mean corrected logMAR VA, FVA, LCVA were -0.18±0.00 (20/13), -0.10±0.08 (20/16), and 0.06±0.06 (20/23), respectively. The VA, FVA, and LCVA had a significant linear negative correlation with the addition of cylinder irrespective of the axes. A significant decrease in FVA was noted on addition of ⩾0.50 D WTR astigmatism and ⩾1.00 D ATR astigmatism. With the addition of 1.00 D of cylindrical lens, 96% of eyes with WTR and ATR astigmatism could maintain 20/20 in VA testing, whereas only 50% and 62% of eyes with WTR and ATR astigmatism, respectively, could maintain 20/20 in FVA testing. Astigmatism may be associated with deterioration of visual function even when conventional VA of 20/20 is attained. Functional VA testing seems to be useful in evaluating the masked astigmatic visual impairment that cannot be detected by conventional VA testing.

Effect of preoperative tear function on early functional visual acuity after laser in situ keratomileusis

We determined whether functional visual acuity (VA) parameters and a dry eyes (DEs) symptoms questionnaire could predict DEs in a population of visual terminal display (VDT) users. This prospective study included 491 VDT users from the Osaka Study. Subjects with definite DE, diagnosed with the presence of DE symptoms, tear abnormality (Schirmer test ≤ 5 mm or tear breakup time [TBUT] ≤ 5 seconds), and conjunctivocorneal epithelial damage (total staining score of ≥3 points), or probable DE, diagnosed with the presence of two of them, were assigned to a DE group, and the remainder to a non-DE group. Functional VA was assessed, and DE questionnaires were administered. We assessed whether univariate and discriminant analyses could determine to which group a subject belonged. Sensitivity and specificity were assessed. Of 491 subjects, 320 and 171 were assigned to the DE and non-DE groups, respectively. No significant differences were observed between DE and non-DE groups in Schirmer test value and epithelial damage, but TBUT value (3.1 ± 1.5 vs. 5.9 ± 3.0 seconds). The sensitivity and specificity of single test using functional VA parameters were 59% and 49% in functional VA, 60% and 50% in visual maintenance ratio, and 83% and 30% in frequency of blinking, respectively. According to a discriminant analysis using a combination of functional VA parameters and a DE questionnaire, six variables were selected for the discriminant equation, of which area under the curve (AUC) was 0.735. Sensitivity and specificity of diagnoses predicted by the discriminant equation were 85.9% and 45.6%, respectively. The discriminant equation obtained using functional VA measurement combined with a symptoms questionnaire may suggest the possibility for the first step screening of DE with unstable tear film. Since the questionnaire has an overall poor sensitivity and specificity, further amelioration may be necessary for the actual utilization of this screening tool.

Recently, functional visual acuity (FVA) measurement has been reported to be an important method of determining 'masked impairment of visual function' and assessing visual acuity in detail. This review discusses a new continuous FVA measurement system for the assessment of visual performance and introduces the application of FVA measurement in cataract and intraocular lens implantation. The FVA was first developed to detect impaired visual function for daily activities in dry eye syndrome. The usefulness of this new methodology has been described in patients with tear instability, undergoing laser-assisted in-situ keratomileusis surgery, with Stevens-Johnson syndrome, Sjögren syndrome and mild cataract opacities. The microstructure of the lenticular opacities is highly variable (nucleus sclerosis and/or posterior capsular cataract and/or cortical opacity) causing a combination of different effects on the incident light rays that can be refracted, reflected, absorbed or scattered. In some cases, patients have a good visual acuity but may complain of disturbances in vision quality. We reported the improvement of FVA after cataract surgery in patients with mild cataracts and visual symptomatology despite a good preoperative and postoperative conventional visual acuity. To detect visual impairment due to cataract, measurement of FVA was useful in the evaluation of vision quality and changes in kinetic vision after phacoemulsification surgery. FVA measurement is an effective and noninvasive test that reflects the complaints of blurring/glare and postoperative satisfaction in patients with mild cataract.

To evaluate the efficacy of punctum plug insertion on tear and dynamic visual function in dry eye patients with short break-up time (s-BUT) of the tears. A prospective comparative case series design was used. Twenty-seven eyes of 27 dry eye patients with a s-BUT seen at Keio University School of Medicine, Department of Ophthalmology, were studied. Functional visual acuity (FVA) measurements, tear function examinations and ocular surface evaluations including Schirmer test, tear break-up time, fluorescein and Rose Bengal vital staining scores were performed before and 1 month after insertion of punctum plugs (PP) in dry eye patients with s-BUT. Degree of satisfaction with the PP treatment was also graded. Nineteen out of 27 eyes (70.4%) showed a satisfactory outcome with the PP treatment because of decreased subjective dry eye symptoms. On the other hand, six out of eight eyes with an unsatisfactory outcome had epiphora. The visual maintenance ratio value was observed to significantly increase from 0.87 +/- 0.09 to 0.91 +/- 0.07 in eyes with no epiphora, whereas the visual maintenance ratio value significantly decreased from 0.98 +/- 0.10 to 0.86 +/- 0.13 in the group of eyes with epiphora after PP treatment. (p < 0.05) Likewise, FVA significantly improved after PP insertion in the group with no epiphora and decreased in eyes with epiphora. Visual acuity in the conventional Landolt visual testing remained significantly unchanged in both group of eyes with or without epiphora. FVA was useful in assessing and quantifying vision related symptomatology in s-BUT type of dry eye treated with PP occlusion.

To investigate the effect of diquafosol tetrasodium on tear and visual function in short break-up time (sBUT) dry eye (DE). This interventional nonrandomized comparative study involved 11 eyes in 11 patients with sBUT DE (symptom-positive sBUT group) and 13 eyes in 13 volunteers with BUT values ≤5 s without DE symptoms (symptom-negative sBUT group). Tear function was assessed by measuring BUT and Schirmer values. Serial measurements were made of visual acuities (using a functional visual acuity measurement system) and higher-order aberrations (using a wavefront sensor). The parameters were compared before and 1 month after diquafosol tetrasodium instillation. Any changes in symptomatology after administration were also recorded. After diquafosol tetrasodium administration, BUT values tended to increase in the symptom-positive sBUT group (P=0.07) and significantly increased in the symptom-negative sBUT group (P<0.05). LogMAR functional, minimal, and maximal visual acuities and higher-order aberrations significantly decreased after diquafosol tetrasodium administration in the symptom-positive sBUT group (P<0.05), while there were no significant changes in these values in the symptom-negative sBUT group (P>0.05). Diquafosol tetrasodium administration provided relief of DE symptoms in 75% of patients in the symptom-positive sBUT group. Diquafosol tetrasodium appeared to improve tear film stability and visual function in sBUT DE.

The aim of this study was to use conventional visual acuity measurements to quantify the functional visual acuity (FVA) in eyes with successfully treated amblyopia, and to compare the findings with those for contralateral normal eyes. Nineteen patients (7 boys, 12 girls; age 7.5 ± 2.2years) with successfully treated unilateral amblyopia and the same conventional decimal visual acuity in both eyes (better than 1.0) were enrolled. FVA, the visual maintenance ratio (VMR), maximum and minimum visual acuity, and the average response time were recorded for both eyes of all patients using an FVA measurement system. The differences in FVA values between eyes were analyzed. The mean LogMAR FVA scores, VMR (p < 0.001 for both), and the LogMAR maximum (p < 0.005) and minimum visual acuity (p < 0.001) were significantly poorer for the eyes with treated amblyopia than for the contralateral normal eyes. There was no significant difference in the average response time. Our results indicate that FVA and VMR were poorer for eyes with treated amblyopia than for normal eyes, even though the treatment for amblyopia was considered successful on the basis of conventional visual acuity measurements. These results suggest that visual function is impaired in eyes with amblyopia, regardless of treatment success, and that FVA measurements can provide highly valuable diagnosis and treatment information that is not readily provided by conventional visual acuity measurements.

The effect of tinted soft contact lens wear on functional visual acuity and higher-order aberrations

To evaluate visual function changes after punctal plug (PP) occlusion in patients with short breakup time of tear film (BUT) type of dry eyes. A prospective comparative study was performed in 43 eyes of 43 dry eye patients with short BUTbreakup time of tear film receiving PP occlusion. Patients were divided into 2 groups as those receiving only upper or only lower occlusion. Functional visual acuity measurements, tear function evaluations, and questionnaire on satisfaction with treatment in relation to presence of epiphora were performed before and 1 month after PP insertion. Twenty eyes of 43 eyes (46.5%) with only lower occlusion and 17 eyes of 43 eyes (39.5%) with only upper occlusion showed satisfactory outcomes with treatment. One of 43 eyes (2.3 %) had epiphora. Vital staining scores and BUT values significantly improved in both groups after occlusion. The mean logarithm of the minimum angle of resolution functional visual acuity value significantly improved only in eyes receiving upper PP occlusion. Upper PP occlusion seems to be associated not only with improvement of tear stability, vital staining scores, and treatment-related satisfaction but also with better quality of visual function.