Functional visual acuity measurement in cataract and intraocular lens implantation

Quantifying refractive error in companion dogs with and without nuclear sclerosis: 229 eyes from 118 dogs

OBJECTIVE

To evaluate the relationship between nuclear sclerosis (NS) and refractive error in companion dogs.

ANIMALS STUDIED

One hundred and eighteen companion dogs.

PROCEDURES

Dogs were examined and found to be free of significant ocular abnormalities aside from NS. NS was graded from 0 (absent) to 3 (severe) using a scale developed by the investigators. Manual refraction was performed. The effect of NS grade on refractive error was measured using a linear mixed effects analysis adjusted for age. The proportion of eyes with >1.5 D myopia in each NS grade was evaluated using a chi-square test. Visual impairment score (VIS) was obtained for a subset of dogs and compared against age, refractive error, and NS grade.

RESULTS

Age was strongly correlated with NS grade (p < .0001). Age-adjusted analysis of NS grade relative to refraction showed a mild but not statistically significant increase in myopia with increasing NS grade, with eyes with grade 3 NS averaging 0.58-0.88 D greater myopia than eyes without NS. However, the myopia of >1.5 D was documented in 4/58 (6.9%) eyes with grade 0 NS, 12/91 (13.2%) eyes with grade 1 NS, 13/57 (22.8%) eyes with grade 2 NS, and 7/23 (30.4%) eyes with grade 3 NS. Risk of myopia >1.5 D was significantly associated with increasing NS grade (p = .02). VIS was associated weakly with refractive error, moderately with age, and significantly with NS grade.

CONCLUSIONS

NS is associated with visual deficits in some dogs but is only weakly associated with myopia. More work is needed to characterize vision in aging dogs.

Clinical Results and Factors Affecting Visual Function in Eyes Implanted with an Enhanced Monofocal Intraocular Lens

Purpose

To compare the clinical results achieved with the enhanced monofocal intraocular lenses (IOLs) with those of the monofocal IOL and investigate factors affecting the distance, intermediate, and near vision.

Patients and Methods

Patients were included who underwent bilateral consecutive cataract surgeries using the same IOLs with follow-up to 1 month postoperatively. Refractions, monocular UDVA and CDVA, and binocular distance-corrected functional visual acuity at 5 meters (BDCFVA), at 66 centimeters (BDCIFVA) and at 40 centimeters (DCNVA) were assessed. Multiple regression analysis was used to assess the factors affecting binocular BDCFVA, BDCIFVA, and BDCNFVA. Subjective symptoms were assessed using the Near Activity Visual Questionnaire (NAVQ) and visual analogue scale (VAS).

Results

Sixty patients (120 eyes) implanted with the Tecnis Eyhance IOL (30 patients, 60 eyes) or the Tecnis monofocal IOL (30 patients, 60 eyes) were included. The Tecnis Eyhance IOL provided significantly better binocular BDCIFVA than the Tecnis monofocal IOL in patients under 70 years of age. Multiple regression analysis showed that age was the only factor affecting distance and intermediate visual function in eyes with the Tecnis Eyhance IOL; gender, pupillary diameter, axial length, and average keratometry were not significant. There were no significant differences in subjective symptoms.

Conclusion

The comprehensive cohort analysis did not confirm the advantage on the intermediate vision of the Tecnis Eyhance IOL. Younger age may be an important factor to benefit from the unique optical characteristics of this IOL.

Beyond vision:Cataract and health status in old age, a narrative review

Cataract is a leading cause of visual impairment in old age. Lens opacification is notoriously associated with several geriatric conditions, including frailty, fall risk, depression and cognitive impairment. The association is largely attributable to visual impairment, while other mechanisms, associated with extraocular comorbidity and lifestyle, might partly explain this correlation. Available literature suggests that cataract surgery may be effective in decreasing fall risk, improving depressive symptoms and limiting the risk of cognitive impairment and dementia incidence, although intervention studies on these outcomes are still limited. In this review we also emphasize the need to move from the concept of visual acuity to functional vision, especially in the context of the geriatric patient. Research is needed regarding the effect on the cited outcomes of different cataract treatment strategies, such as systematic bilateral versus monolateral surgery and use of different intraocular lenses.

Rapamycin relieves the cataract caused by ablation of Gja8b through stimulating autophagy in zebrafish

Macroautophagy/autophagy is known to be important for intracellular quality control in the lens. GJA8 is a major gap junction protein in vertebrate lenses. Mutations in GJA8 cause cataracts in humans. The well-known cataractogenesis mechanism is that mutated GJA8 leads to abnormal assembly of gap junctions, resulting in defects in intercellular communication among lens cells. In this study, we observed that ablation of Gja8b (a homolog of mammalian GJA8) in zebrafish led to severe defects in organelle degradation, an important cause of cataractogenesis in developing lens. The role of autophagy in organelle degradation in lens remains disputable. Intriguingly, we also observed that ablation of Gja8b induced deficient autophagy in the lens. More importantly, in vivo treatment of zebrafish with rapamycin, an autophagy activator that inhibits MAPK/JNK and MTORC1 signaling, stimulated autophagy in the lens and relieved the defects in organelle degradation, resulting in the mitigation of cataracts in gja8b mutant zebrafish. Conversely, inhibition of autophagy by treatment with the chemical reagent 3-MA blocked these recovery effects, suggesting the important roles of autophagy in organelle degradation in the lens in gja8b mutant zebrafish. Further studies in HLE cells revealed that GJA8 interacted with ATG proteins. Overexpression of GJA8 stimulated autophagy in HLE cells. These data suggest an unrecognized cataractogenesis mechanism caused by ablation of Gja8b and a potential treatment for cataracts by stimulating autophagy in the lens.Abbreviations: 3-MA: 3-methyladenine; ATG: autophagy related; AV: autophagic vacuoles; Dpf: days post fertilization; GJA1: gap junction protein alpha 1; GJA3: gap junction protein alpha 3; GJA8: gap junction protein alpha 8; Hpf: hours post fertilization; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PtdIns3K: class III phosphatidylinositol 3-kinase; WT: wild type.

Relationship between visual function and cognitive function in the elderly: A cross-sectional observational study

It has been suggested that functional visual acuity (VA) testing may be able to measure both the visual performance and cognitive ability needed for driving and help to reduce the number of road traffic accidents. The aim of this study was to investigate the relationship between visual ability and cognitive function in healthy elderly subjects. The study included 34 eyes with a decimal best-corrected visual acuity (VA) ≥1.0 in 34 subjects (16 men, 18 women; mean age 72.7 ± 6.1 [range, 61-83] years) with the same type of monofocal intraocular lens implant. Using the score on the Japanese version of the Mini-Mental State Examination (MMSE) questionnaire, the subjects were divided into a mild cognitive impairment (MCI) group (score <28) and a normal cognition (NC) group (score ≥28). Visual ability was evaluated by functional VA testing. Functional VA was significantly lower in the MCI group (n = 10) than in the NC group (n = 24; P<0.02). There was no significant difference in best-corrected VA between the two groups. High correlations were found between the MMSE score and the logMAR functional VA (r = -0.36, P = 0.04), standard deviation of functional VA (r = -0.39, P = 0.02), and the visual maintenance ratio (r = 0.34, P = 0.048). In summary, despite a good best-corrected VA, deterioration in visual ability was detected in elderly individuals with MCI when measured by the functional VA test. Functional VA could be used to evaluate the integrated visual ability associated with age-related cognitive decline and have applications that help to reduce the disproportionately high rate of road traffic accidents in the elderly.

Kinetic visual acuity is correlated with functional visual acuity at higher speeds

Objective

To measure the kinetic visual acuity (KVA) which is the ability to identify approaching objects and the functional visual acuity (FVA) which is continuous VA during 1 min under binocular and monocular condition (non-dominant eye shielding) for healthy subjects, and related ocular parameters to explore their correlation and implication in aspect of integrated visual function.

Methods

The mean age of the 28 participants was 38.6±8.9 years (range, 23–57 years; 6 women). A KVA metre (AS-4Fα) and FVA metre (AS-28) were used to measure KVA and FVA, respectively. Multiple regression analysis was conducted to explore correlations among the measured visual function and related parameters, including age, binocularity, best-corrected visual acuity, refraction and tear break-up time.

Results

The results of binocular KVA were better than monocular KVA at all speeds. A strong correlation was found between monocular and binocular KVA. The results of binocular FVA were better than monocular FVA (p<0.001) and there was a correlation between monocular and binocular FVA (R=0.638, p<0.001), as well as the maintenance rate for FVA (R=0.228, p=0.003). A linear mixed-effects model revealed that binocularity for KVA prediction was significant at all speeds and FVA was also significant at 60 km/h (p<0.05).

Conclusion

The current results suggest that both binocularity and FVA may contribute to KVA.

Trial registration number

UMIN00032385

Shortened Measurement Time of Functional Visual Acuity for Screening Visual Function

The functional visual acuity test which is the average of the visual acuities measured during a specific time frame (standard, 60 seconds) has been used recently to assess the visual function in various conditions. The availability of a shorter version of the functional visual acuity test promises to be patient friendly in that it is a simple screening test performed in a shorter period of time than the standard test. The results of measurements of the FVA test between the 30-second measurement time (short-version FVA test) and the standard 60-second measurement are compared, and the feasibility of the short-version FVA test instead of the standard FVA test is investigated. Twenty-eight healthy volunteers (25 men and 3 women) were enrolled in this prospective observational study. All subjects underwent measurement of the binocular distance-corrected visual acuity and the binocular distance-corrected FVA with the 60-second and 30-second measurement times. The interchangeability of the corrected-distance FVA, maximal VA, visual maintenance ratio, and average response time in the short-version and the standard FVA tests was evaluated using the Bland–Altman method, and the results showed agreements of the two tests except for the minimal VA. The short-version FVA test is equivalent to the standard method except for evaluating the visual acuity fluctuations and promises to be a simple visual screening test that can be performed in a shorter time.

Improving clinical refractive results of cataract surgery by machine learning

AIM

To evaluate the potential of the Support Vector Machine Regression model (SVM-RM) and Multilayer Neural Network Ensemble model (MLNN-EM) to improve the intraocular lens (IOL) power calculation for clinical workflow.

BACKGROUND

Current IOL power calculation methods are limited in their accuracy with the possibility of decreased accuracy especially in eyes with an unusual ocular dimension. In case of an improperly calculated power of the IOL in cataract or refractive lens replacement surgery there is a risk of re-operation or further refractive correction. This may create potential complications and discomfort for the patient.

METHODS

A dataset containing information about 2,194 eyes was obtained using data mining process from the Electronic Health Record (EHR) system database of the Gemini Eye Clinic. The dataset was optimized and split into the selection set (used in the design for models and training), and the verification set (used in the evaluation). The set of mean prediction errors (PEs) and the distribution of predicted refractive errors were evaluated for both models and clinical results (CR).

RESULTS

Both models performed significantly better for the majority of the evaluated parameters compared with the CR. There was no significant difference between both evaluated models. In the ±0.50 D PE category both SVM-RM and MLNN-EM were slightly better than the Barrett Universal II formula, which is often presented as the most accurate calculation formula.

CONCLUSION

In comparison to the current clinical method, both SVM-RM and MLNN-EM have achieved significantly better results in IOL calculations and therefore have a strong potential to improve clinical cataract refractive outcomes.

Three-rods test as drivers' license vision test from the viewpoint of reproducibility, eye deviation, and functional visual acuity

Background

Three-rods test is required as depth perception vision test to obtain motor vehicle license to drive taxies, buses, and trucks in Japan. Functional visual acuity is measured automatically by successive visual target presentation in a fixed period of time. This study examined three-rods test from the viewpoint of reproducibility, eye deviation, and functional visual acuity to assess the feasibility for drivers' license vision test.

Methods

At three-rods test, a central rod was moved at the speed of 50 mm/sec forward and backward automatically against two fixed rods on both sides inside an illuminated box. An examinee at the distance of 2.5 m observed the rods inside the box from a small window and pushed a button to stop the central rod in alignment with the fixed rods. Erred distance of the central rod from the fixed rods as a mean of 4 measurements was used. At functional visual acuity test, an examinee moved a joystick to the same direction as Landolt-C opening as a visual target which was sequentially presented every 2 seconds for 30 times in 1 minute.

Results

The mean erred distance of three-rods test was reproducible between two tests done on separate occasions (n = 44, ρ = 0.679, P < 0.0001, Spearman rank correlation). Exophoria induced by wearing 4-prism-diopter base-out prism did not significantly influence the mean erred distance while vertical diplopia induced by wearing 4-prism-diopter base-up prism disrupted the measurement (n = 9). The mean erred distance of three-rods test was better correlated with functional visual acuity tested with both eyes open than with conventional visual acuity with both eyes open (n = 17, ρ = 0.2 versus ρ = 0.179).

Conclusion

In the context of the small sample size in the present study, the three-rods test was reproducible, and testable in the presence of phoria, but not testable in diplopia, indicating the feasibility as a depth perception vision test.

Functional visual acuity in patients with successfully treated amblyopia: a pilot study

PURPOSE

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.

METHODS

Nineteen patients (7 boys, 12 girls; age 7.5 ± 2.2 years) 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.

RESULTS

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.

CONCLUSIONS

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.

Comparison of postoperative corneal changes between dry eye and non-dry eye in a murine cataract surgery model

AIM

To compare the effects of the surgical insult of cataract surgery on corneal inflammatory infiltration, neovascularization (NV) and lymphangiogenesis (LY) between the dry eye and non-dry eye in murine cataract surgery models.

METHODS

We established two groups of animals, one with normal eyes (non-dry eye) and the second with induced dry eyes. In both groups, we used surgical insults to mimic human cataract surgery, which consisted of lens extraction, corneal incision and suture. After harvesting of corneas on the 9(th) postoperative day and immunohistochemical staining, we compared NV, LY and CD11b+ cell infiltration in the corneas.

RESULTS

Dry eye group had significantly more inflammatory infiltration (21.75%±7.17% vs 3.65%±1.49%; P=0.049). The dry eye group showed significantly more NV (48.21%±4.02% vs 26.24%±6.01%; P=0.016) and greater levels of LY (9.27%±0.48% vs 4.84%±1.15%; P=0.007). In corneas on which no surgery was performed, there was no induction of NV in both the dry and non-dry group, but dry eye group demonstrated more CD11b+ cells infiltration than the non-dry eye group (0.360%±0.160% vs 0.023%±0.006%; P=0.068). Dry eye group showed more NV than non-dry eye group in both topical PBS application and subconjunctival PBS injection (P=0.020 and 0.000, respectively).

CONCLUSION

In a murine cataract surgery model, preexisting dry eye can induce more postoperative NV, LY, and inflammation in corneal tissue.

Relationship between Functional Visual Acuity and Useful Field of View in Elderly Drivers

Purpose

To investigate the relationship between the functional visual acuity (FVA) and useful field of view (UFOV) in elderly drivers and assess the usefulness of the FVA test to screen driving aptitude in elderly drivers.

Methods

This study included 45 elderly drivers (31 men, 14 women; mean age, 68.1 years) and 30 younger drivers (26 men, 4 women; mean age, 34.2 years) who drive regularly. All participants underwent measurement of the binocular corrected distant visual acuity (CDVA), binocular corrected distant FVA (CDFVA), and Visual Field with Inhibitory Tasks Elderly Version (VFIT-EV) to measure UFOV. The tear function and cognitive status also were evaluated.

Results

The CDVA, the CDFVA, cognitive status, and the correct response rate (CAR) of the VFIT-EV were significantly worse in the elderly group than in the control group (P = 0.000 for all parameters). The cognitive status was correlated significantly with the CDVA (r = -0.301, P = 0.009), CDFVA (r = -0.402, P = 0.000), and the CAR of the VFIT-EV (r = 0.348, P = 0.002) in all subjects. The results of the tear function tests were not correlated with the CDVA, CDFVA, or VFIT-EV in any subjects. Stepwise regression analysis for all subjects in the elderly and control groups showed that the CDFVA predicted the CAR most significantly among the clinical factors evaluated.

Conclusion

The FVA test is a promising method to screen the driving aptitude, including both visual and cognitive functions, in a short time.

Functional Visual Acuity in Age-Related Macular Degeneration

PURPOSE

We evaluated whether a functional visual acuity (FVA) system can detect subtle changes in central visual acuity that reflect pathological findings associated with age-related macular degeneration (AMD).

METHODS

Twenty-eight patients with unilateral AMD and logMAR monocular best corrected VA better than 0 in both eyes, as measured by conventional chart examination, were analyzed between November 2012 and April 2013. After measuring conventional VA, FVA, and contrast VA with best correction, routine eye examinations including spectral domain-optical coherence tomography were performed. Standard Schirmer test was performed, and corneal and lens densities were measured.

RESULTS

The FVA score (p < 0.001) and visual maintenance ratio (p < 0.001) measured by the FVA system, contrast VA (p < 0. 01), and conventional VA (p < 0.01) were significantly worse in the AMD-affected eyes than in the fellow eyes. No significant differences were observed in the anterior segment conditions. Forward stepwise regression analysis demonstrated that the length of interdigitation zone disruption, as visualized by optical coherence tomography imaging, correlated with the FVA score (p < 0.01) but not with any other parameters investigated.

CONCLUSIONS

The FVA system detects subtle changes in best corrected VA in AMD-affected eyes and reflects interdigitation zone disruption, an anatomical change in the retina recorded by optical coherence tomography. Further studies are required to understand the value of the FVA system in detecting subtle changes in AMD.

Functional visual acuity assessment of severe atopic keratoconjunctivitis

PURPOSE

To evaluate changes in functional visual acuity (FVA) measurements before and after treatment with 0.1% cyclosporine ophthalmic solution for 3 months in patients with severe atopic keratoconjunctivitis (AKC).

METHODS

Pairs of eyes were analyzed from 3 boys (mean age 9 ± 3.6 years) who complained of having severe AKC and were recruited for the study. Conventional Landolt visual acuity, FVA, and visual maintenance ratio (VMR) measurements were conducted before and after 3 months of 0.1% cyclosporine eye drop treatment. Tear film lipid layer interferometry, tear film break-up time, fluorescein and rose bengal vital stainings, and the Schirmer test were also performed before and after treatment.

RESULTS

Eye drop treatment was associated not only with improvement of tear function and ocular surface status but also with better quality of visual function. The mean logarithm of the minimum angle of resolution FVA and Landolt visual acuity values improved from 0.45 ± 0.26 and 0.13 ± 0.17 before treatment to 0.16 ± 0.03 and -0.06 ± 0.05 after treatment, respectively. Similarly, the mean VMR values were markedly improved from 0.88 ± 0.06 to 0.95 ± 0.03 after treatment.

CONCLUSIONS

FVA and VMR are promising parameters in the assessment of dynamic visual acuity changes in AKC-affected patients and evaluation of treatment outcome.

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

PURPOSE

To investigate the differences of functional visual acuity (FVA) and high order aberrations (HOAs) in relation to tinted and clear hydrogel soft contact lens (SCL) wear.

METHODS

A prospective comparative study was performed in 16 eyes of 16 healthy volunteers. Dynamic visual acuity (using a FVA measurement system) and higher-order aberrations (using a wavefront sensor) were compared in subjects wearing two types of soft contact lenses: 1-day Acuvue(®) (Vistakon, Jacksonville, FL) clear and the 1-day Acuvue(®) Define(TM) (Vistakon, Jacksonville, FL) tinted lens. The blink rates were recorded during FVA testing. The correlation between the difference of HOAs and differences in FVA values was analyzed.

RESULTS

The mean LogMAR FVA scores with clear and tinted SCLs were 0.07 ± 0.13 and 0.14 ± 0.17 (P<0.05). The mean blink frequencies with clear and tinted SCL wear were 18.4 ± 8.3 and 25.3 ± 4.7 blinks/min (P<0.05). Both 3rd-order aberrations and total HOAs showed statistically significant differences between the two types of soft contact lenses for 6mm pupil measurements (P<0.05). A significant positive linear correlation was observed between ΔHOAs and ΔLogMAR FVA for 6mm pupil measurements (R=0.53, P=0.04).

CONCLUSIONS

Tinted contact lens wear appears to induce a reduction in optical quality. Functional visual acuity measurement is a useful procedure to study the changes of visual performance and quality in tinted contact lens wear.

Measuring the quality of vision after cataract surgery

PURPOSE OF REVIEW

The purpose of this review is to report some of the latest advances in visual acuity measurements and to review key articles on quality of visual after cataract surgery with intraocular lens (IOL) implantation.

RECENT FINDINGS

Different quality of life instruments were used in the most recent studies and showed improvements in subjective quality of vision after cataract surgery with or without ocular comorbidities and independent of the type of IOL implanted. The use of multifocal IOLs improved near vision without any adverse effect on distance acuity. Contrast sensitivity was lower in patients with multifocal IOLs. Femtosecond laser cataract surgery increased predictability of the steps involved in cataract surgery but has a definite learning curve associated with an initial high rate of complications. Toric IOLs showed significant improvement in uncorrected distant visual acuity with low amount of decentration and wavefront error. Incorporating the testing of visual acuity in real-life scenarios that patients encounter routinely using automated instruments promises to transform visual assessment in a rapid manner that can be integrated into clinical practice.

SUMMARY

Visual outcomes of cataract surgery with IOL implantation generally yield highly satisfactory results. Newer cataract surgery technology has emerged in an era wherein patients are demanding excellent visual results. Changes in the way we normally assess routine visual acuities should be implemented. We have introduced testing of visual acuity in timed, real-life scenarios that patients encounter daily, in an automated instrument, which may help us better document patient's complaints and surgical outcomes.

Detection of early visual impairment in patients with epiretinal membrane

PURPOSE

Patients with epiretinal membrane sometimes complain of impaired central visual function, despite good best corrected visual acuity (BCVA), as measured by visual acuity (VA) charts. Here, we evaluate early epiretinal membrane-induced changes in central VA.

METHODS

Subjects were 72 eyes of 36 patients with epiretinal membrane in only one eye and a BCVA in each eye better than 1.0, as measured by conventional Landolt C chart, at the Retina Division Clinic of the Department of Ophthalmology, Keio University Hospital, between December 2010 and November 2011. The conventional Landolt VA, functional VA (FVA) and contrast VA measurements were taken after a general eye examination. For the FVA, Landolt optotypes were sequentially displayed every 2 seconds, which size was changed according to the correctness of the answer. To exclude the influence of other diseases, a standard Schirmer test was performed to diagnose dry eye, and corneal and lens densities were evaluated.

RESULTS

Average BCVA measured by Landolt C chart was not changed between affected and unaffected fellow eyes. However, the affected eyes showed a poorer FVA score (0.21 ± 0.12, affected; 0.09 ± 0.12, fellow) and visual maintenance ratio (VMR) (0.90 ± 0.04, affected; 0.94 ± 0.04, fellow), measured by the FVA system, and contrast VA score (0.35 ± 0.11, affected; 0.25 ± 0.14, fellow) than fellow eyes. The FVA and contrast VA values were correlated with the presence of epiretinal membrane, but not with the presence of dry eye, cataract and corneal densities.

CONCLUSION

FVA and contrast VA results reflected early changes in central visual function caused by epiretinal membrane, which were not detected by conventional Landolt BCVA.

Effect of experimentally induced astigmatism on functional, conventional, and low-contrast visual acuity

PURPOSE

To report the changes in functional visual acuity (FVA) in eyes with experimentally induced astigmatism.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.