Capabilities of potential vision test measurements

Trichromatic critical flicker frequency as potential visual test in cataract and macula disease patients

PURPOSE

To investigate the capacity of critical flicker frequency (CFF) in discriminating cataract eyes with or without macula disease using trichromatic flickers, and to develop a model to predict postoperative best corrected visual acuity (BCVA).

METHODS

Patients were divided into two groups based on the presence or absence of macular disease. CFF threshold measurements of red (R-CFF), green (G-CFF), and yellow (Y-CFF) flickers were conducted both preoperatively and postoperatively. A generalized estimating equations model (GEE) was employed to examine the relationship between CFF threshold and 3-month postoperative BCVA.

RESULTS

A total of 115 eyes were enrolled, with 59 eyes in the cataract alone group and 56 eyes in the cataract with macular disease group completing the follow-up. R-CFF was found to be consistent before and after cataract removal (P = 0.06), even in cases where OCT was not performed successfully (P > 0.05). Y-CFF showed the highest AUC (0.798) for differentiating ocular comorbidities. According to the GEE model, in patients with a CFF threshold below 26 Hz, the odds ratios for achieving a postoperative VA of 20/40 or better were 34.8% for R-CFF, 26.0% for G-CFF, and 24.5% for Y-CFF.

CONCLUSION

CFF emerges as a promising tool for predicting postoperative BCVA, providing valuable supplementary insights when fundus examination is obstructed. R-CFF demonstrates the best resistance to cataracts, while Y-CFF exhibits the highest sensitivity both in identifying macular diseases and predicting postoperative BCVA of 20/40 or better.

Applications of the pinhole effect in clinical vision science

The pinhole effect is commonly used to discriminate uncorrected refractive error from ocular diseases. A small aperture limits the width of light beams entering the eye, thus increasing the depth of focus. The pinhole effect has also been used in spectacles, contact lenses, corneal inlays, and intraocular lenses (IOLs) to improve reading by compensating for loss of accommodative function. Pinhole spectacles improve near visual acuity, but reduce reading speed, increase interblink interval, and decrease tear break-up time. For contact lenses and IOLs, pinhole devices are usually used in the nondominant eye, which allow compensation of various refractive errors and decrease spectacle dependence. Pinhole corneal inlays are implanted during laser in situ keratomileusis or as a separate procedure. Pinhole IOLs are gaining popularity, particularly as they do not bring a risk of a local inflammatory reaction as corneal inlays do. Disadvantages of using the pinhole effect include high susceptibility to decentration, decrease in retinal luminance levels, and difficulties in performing fundus examinations or surgery in eyes with implanted devices. There are also concerns regarding perceptive issues with different retinal illuminances in the 2 eyes (the Pulfrich effect).

The theory of critical flicker fusion frequency and its application in cataracts

Background

Due to media opacity, it is usually difficult to accurately evaluate the postoperative visual acuity in cataracts patients. As a small and portable tool, the critical flicker fusion frequency (CFF) device reflects the temporal resolution of visual function and has been widely used in clinical research. However, poor understanding of the technique and equipment limitations have restricted its clinical application in China.

Main text

There was a decrease in the CFF value in various ophthalmic diseases, indicating that the CFF is sensitive to detect visual functional changes. A number of studies have shown that the CFF test can accurately distinguish patients with simple cataracts from those with cataracts combined with fundus disease, and, as a visual test, it can more accurately predict postoperative visual acuity without being affected by media opacity. This study comprehensive reviews the basic principles of CFF and its application in ophthalmology, especially in cataracts.

Conclusions

As one of the tools for dynamic visual function detection, the CFF test could help doctors to assess the possible presence of fundus disease in cataracts patients, especially in eyes with dense cataracts, and more precisely provide a reasonable visual prognosis than other available visual tests.

Results of the Pinhole Test Correlate with Hybrid Contact Lens Visual Acuity in Patients with Visual Impairment due to Corneal Diseases

Introduction. Trial rigid lens fitting is considered the best approach to determine whether the correction of residual defocus and irregular astigmatism might improve the visual acuity in patients with corneal disorders including keratoconus. This study aimed to analyze the correlation between hybrid lenses and pinhole visual acuity (VA). Methods. Patients undergoing hybrid contact lens fitting at the Hygeia Clinic, Poland, were included. The VA of each patient was assessed as decimal Snellen fractions under the following conditions: (i) uncorrected VA, (ii) VA with spherocylindrical correction (i.e., corrected distance VA), (iii) VA with a single 1.2 mm pinhole occluder, and (iv) VA with the best-fitted hybrid contact lens. Pearson’s correlation coefficient r was used to assess correlations among variables. Results. This study involved 29 eyes of 19 patients, mainly with advanced keratoconus. The uncorrected VA was 0.11 ± 0.10. The pinhole test provided significantly improved VA over corrected distance VA (0.51 ± 0.29 vs. 0.31 ± 0.20, respectively; $p<0.0001$ ). Similarly, the fitted hybrid contact lenses provided improved VA over corrected distance VA (0.66 ± 0.26 vs. 0.31 ± 0.20, respectively; $p<0.0001$ ). The pinhole VA was strongly correlated with the hybrid contact lens VA (r = 0.8135; 95% CI: 0.61–0.92; $p<0.0001$ ). The improvement in the pinhole test over corrected distance VA was moderately correlated with the improvement with the fitted lens over corrected distance VA (r = 0.6269; 95% confidence interval (CI): 0.32–0.80; $p=0.0005$ ). Conclusions. A significant improvement in VA with the pinhole test is a simple predictor of general improvement with hybrid contact lenses. The pinhole test should be used in patients with corneal diseases such as keratoconus to determine whether optical aberrations associated with the disease cause their visual impairment.

Pupil steering holographic display for pre-operative vision screening of cataracts

Cataract is the most common cause of preventable blindness and vision loss where the only treatment is surgical replacement of the natural lens with an intraocular lens. Computer-generated holography (CGH) enables to control phase, size, and shape of the light beam entering through the eye-pupil. We developed a holographic vision simulator to assess visual acuity for patients to experience the postoperative corrected vision before going through surgery. A holographically shaped light beam is directed onto the retina using small non-cataractous regions of the lens with the help of a pupil tracker. A Snellen chart hologram is shown to subjects at desired depth with myopia and hyperopia correction. Tests with 13 patients demonstrated substantial improvements in visual acuity and the simulator results are consistent with the post-operative vision tests. Holographic simulator overperforms the existing vision simulators, which are limited to static pinhole exit pupils and incapable of correcting aberrations.

The clinical application of critical flicker fusion frequency in demyelinating optic neuritis

Purpose

To investigate the application of critical flicker fusion frequency (CFF) in demyelinating optic neuritis (DON).

Methods

A cross-sectional study. A total of 127 eyes in 69 DON patients and 63 eyes in 33 healthy control (HC) groups were included between January 2021 to September 2021 from Department of Ophthalmology, PLA General Hospital. Patients underwent best-corrected visual acuity (BCVA), visual field, optical coherence tomography (OCT), flash visual evoked potential (F-VEP), and CFF examinations. The affected eyes were divided into aquaporins 4 (AQP4-), myelin oligodendrocyte glycoprotein (MOG-), and double negative DON according to serum antibody; mild, moderate, severe degree visual impairment according to BCVA ≥ 0.5, 0.1-0.5, < 0.1; and 4 groups: < 1, 1 ∼< 3, 3 ∼ < 6 and > 6 months according to time interval from onset to CFF examination. One-way ANOVA was used to perform above subgroup analysis. The correlations between CFF and F-VEP peak time, peak value, BCVA and mean visual filed defect (MD) were analyzed in order via Pearson correlation analysis.

Results

he trichromatic values of red, green, and yellow in DON affected eyes were 21.83 ± 9.03, 23.66 ± 10.21, 24.09 ± 10.77 Hz, respectively, which was significantly reduced compared with the HC group (t = -14.82, -14.22, -14.00; P < 0.001). The subgroup analysis showed no significant difference between different antibody subtypes (P = 0.914 <0.848 <0.604), whereas, a significant decrease of CFF trichromatic value was found in severe visual acuity impairment group (P < 0.001). There was a significant difference in CFF- trichromatic values at different time points (P < 0.001), to be specific, CFF fluctuated under 20Hz within 3 months after onset and tended to be stable around 24-28Hz. Correlation analysis showed that the peak time of F-VEP (r = -0.486, -0.515, -0.526; P < 0.001), BVCA (r = -0.640, -0.659, -0.642; P < 0.001), were negatively correlated with CFF trichromatic values, MD and CFF were positively correlated (r = 0.486, 0.453, 0.476; P = 0.003, 0.006, 0.004).

Conclusions

A significant decrease of CFF value was found in DON-affected eyes, and it has a good correlation with BCVA, MD and latency of F-VEP, and can better reflect the impairment of visual function.

Straylight as an Indicator for Cataract Extraction in Patients with Retinal Dystrophy

PURPOSE

Straylight reduces retinal sensitivity, which is particularly relevant in conditions with retinal dysfunction, such as retinitis pigmentosa (RP). Retinitis pigmentosa is associated with posterior subcapsular cataract (PSC), a cataract type that is known to cause severe disability glare (i.e., straylight). Study purposes were (1) to determine the severity of disability glare before and after cataract extraction (CE) in subjects with retinal dystrophy; (2) to study possible aggravation of disability glare due to the combination of retinal degradation and increased straylight from PSC; and (3) to evaluate whether straylight can be used to support the possible benefit of (early) CE.

DESIGN

Prospective, comparative study.

PARTICIPANTS

Sixteen patients (25 eyes) with retinal dystrophy scheduled for CE participated.

METHODS

Cataract severity was graded according to the Lens Opacities Classification System (LOCS) III. Preoperatively and postoperatively, corrected distance visual acuity (CDVA), spatial contrast sensitivity with the Pelli-Robson chart, and straylight were tested. Retinal function was assessed with Goldmann visual field and temporal contrast sensitivity (TCS). Temporal contrast sensitivity is a flicker test to evaluate central retinal sensitivity isolated from the eye's optical quality. Central retinal structure was assessed with spectral-domain OCT and fundus autofluorescence.

MAIN OUTCOME MEASURES

Preoperative and postoperative straylight were measured using the C-Quant (Oculus Optikgeräte GmbH, Wetzlar, Germany) and expressed as the logarithm of the straylight parameter s: log(s).

RESULTS

The average straylight value was 1.75 preoperatively and 1.45 postoperatively, 7.1 and 3.5 times higher than in a healthy young eye, respectively. Functionally significant improvement, defined as >0.20 log, was found in 72% of eyes for straylight and in 20% of eyes for CDVA. The CDVA and TCS were significantly correlated. Only straylight improvement was related to preoperative values; therefore, straylight was the only parameter that could be used to support postoperative improvement. In retinal dystrophy, eyes with cataract and a preoperative straylight value ≥1.66 log(s), a 50% chance of functionally significant log(s) improvement can be expected.

CONCLUSIONS

In patients with retinal dystrophy, straylight caused by cataract substantially aggravates visual disability, whereas CDVA is less affected. Therefore, straylight is a valuable (additional) indicator for beneficial CE in patients with retinal dystrophy and cataract.

Assessing visual function behind cataract: preoperative predictive value of the Heine Lambda 100 retinometer

PURPOSE

To analyze the accuracy of the Lambda 100 (Heine) potential visual acuity (VA) measurements in subjects undergoing cataract surgery.

METHODS

The medical records of all consecutive patients who underwent clear corneal incision phacoemulsification cataract surgery by a single surgeon between 2010 and 2012 at the Department of Ophthalmology, Hadassah Medical Center, a tertiary care hospital in Jerusalem, Israel, were reviewed. Subjects age 18 or older with a follow-up time of at least 30 days were included. Subjects with previous ocular comorbidities other than glaucoma were excluded. In addition, patients with intraoperative or perioperative complications that could affect final VA were excluded. Analyses were performed to analyze the accuracy of preoperative retinometer potential VA as a predictor of postoperative best-corrected VA.

RESULTS

A total of 374 operated eyes were included. There was a moderate positive correlation between Lambda estimated VA potential and postoperative achieved best-corrected VA (BCVA) (β coefficient 0.35, p<0.0001). Overall Lambda accurately (within 2 Snellen lines) estimated postoperative BCVA results in 60% of cases. The accuracy of prediction was significantly better in moderate cataracts when compared with advanced cataracts (p<0.01) with a twofold tendency towards underestimation in advanced cataracts. A Lambda ≥0.5 decimal has a calculated positive predictive value of 82% and a negative predictive value of 40% for predicting postoperative BCVA outcome ≥0.5 decimal.

CONCLUSIONS

Lambda may be used to relatively accurately predict postoperative BCVA in cataract patients, specifically in those with moderate cataracts.

Reliability of a standardized test in Swedish for evaluation of reading performance in healthy eyes. Interchart and test-retest analyses

PURPOSE

The purpose of our study was to establish a practical and quick test for assessing reading performance and to statistically analyse interchart and test-retest reliability of a new standardized Swedish reading chart system consisting of three charts constructed according to the principles available in the literature.

METHODS

Twenty-four subjects with healthy eyes, mean age 65 ± 10 years, were tested binocularly and the reading performance evaluated as reading acuity, critical print size and maximum reading speed. The test charts all consist of 12 short text sentences with a print size ranging from 0.9 to -0.2 logMAR in approximate steps of 0.1 logMAR. Two testing sessions, in two different groups (C1 and C2), were under strict control of luminance and lighting environment. Reading performance tests with chart T1, T2 and T3 were used for evaluation of interchart reliability and test data from a second session 1 month or more apart for the test-retest analysis.

RESULTS

The testing of reading performance in adult observers with short sentences of continuous text was quick and practical. The agreement between the tests obtained with the three different test charts was high both within the same test session and at retest.

CONCLUSION

This new Swedish variant of a standardized reading system based on short sentences and logarithmic progression of print size provides reliable measurements of reading performance and preliminary norms in an age group around 65 years. The reading test with three independent reading charts can be useful for clinical studies of reading ability before and after treatment.

Posterior segment causes of reduced visual acuity after phacoemulsification in eyes with cataract and obscured fundus view

Purpose

To determine posterior segment causes of reduced visual acuity after phacoemulsification in eyes with cataract and obscured fundus view.

Patients and methods

Retrospective review of medical records of patients with cataract, obscured fundus view, and normal B-scan ultrasonography, undergoing phacoemulsification from May 2005 to March 2012 was conducted. Eyes with fundus pathology, previous trauma, surgery, glaucoma, amblyopia, or uveitic cataract were excluded. Ocular comorbid conditions, preoperative visual acuity (VA), intraoperative and early postoperative complications, and final best corrected visual acuity (BCVA) at 1 month were abstracted from the records.

Results

All 201 eyes of 179 patients studied had a preoperative VA of ≤6/60. Preoperative ocular comorbidity was present in 31 eyes (15.5%). Intraoperative complications occurred in 20 eyes (10%). Postoperative complications developed in 34 eyes (17.0%). One month postoperatively, 175 eyes (87.1%) achieved a BCVA of ≥6/12; whereas 26 eyes (12.9%) achieved a BCVA of ≤6/18. The most common posterior segment causes of reduced VA in the 26 eyes were age-related macular disease in ten eyes (38.5%) and diabetic maculopathy in six eyes (23.1%). Similar fundus pathology was seen preoperatively in the fellow fundus in 10 of the 26 eyes (38.5%).

Conclusion

One month after phacoemulsification in eyes with cataract and obscured fundus view, age-related macular disease and diabetic maculopathy were the most common posterior segment causes of reduced final BCVA. To avoid postsurgical dissatisfaction, patients with obscured fundus view in their preoperative eye should be counseled, especially if posterior segment pathology exists in their fellow eye.

Psychophysics, reliability, and norm values for temporal contrast sensitivity implemented on the two alternative forced choice C-Quant device

The current paper describes the design and population testing of a flicker sensitivity assessment technique corresponding to the psychophysical approach for straylight measurement. The purpose is twofold: to check the subjects' capability to perform the straylight test and as a test for retinal integrity for other purposes. The test was implemented in the Oculus C-Quant straylight meter, using homemade software (MATLAB). The geometry of the visual field lay-out was identical, as was the subjects' 2AFC task. A comparable reliability criterion ("unc") was developed. Outcome measure was logTCS (temporal contrast sensitivity). The population test was performed in science fair settings on about 400 subjects. Moreover, 2 subjects underwent extensive tests to check whether optical defects, mimicked with trial lenses and scatter filters, affected the TCS outcome. Repeated measures standard deviation was 0.11 log units for the reference population. Normal values for logTCS were around 2 (threshold 1%) with some dependence on age (range 6 to 85 years). The test outcome did not change upon a tenfold (optical) deterioration in visual acuity or straylight. The test has adequate precision for checking a subject's capability to perform straylight assessment. The unc reliability criterion ensures sufficient precision, also for assessment of retinal sensitivity loss.

Clinician versus potential acuity test predictions of visual outcome after cataract surgery

BACKGROUND

The aim of this study was to compare the ability of potential vision tests and clinical judgement to predict postoperative visual acuity after uneventful cataract surgery.

METHODS

Sixty-two subjects (median, 74.5 years) were included in the study. Preoperative measurements included a clinical judgement prediction (based on case history and ocular examination alone), 2 super-illuminated pinhole techniques (distance and near), Potential Acuity Meter and interferometer. Postoperative visual acuity was used as the outcome measure to evaluate the accuracy of the preoperative predictions.

RESULTS

Subjects were categorized as follows: (a) moderate cataract (N = 25); (b) moderate cataract and comorbidity (N = 18), and (c) advanced cataract (N = 19). Preoperative predictions within 2 lines of the postoperative visual acuity were as follows (a, b, and c respectively): clinical judgement (92%, 72%, 58%), super-illuminated pinhole distance (96%, 100%, 21%), super-illuminated pinhole near (92%, 78%, 26%), Potential Acuity Meter (72%, 67%, 21%), and interferometer (56%, 61%, 37%).

CONCLUSIONS

Based on the preoperative predictions above, none of the potential vision tests was useful compared with the clinical judgement in the advanced cataract group. The super-illuminated pinhole (distance) provided additional information beyond clinical judgement in the moderate cataract subgroup. The Potential Acuity Meter and interferometer were inaccurate even in the presence of moderate cataract, and this and other recent findings suggest they should no longer be considered adequate for potential vision assessment.

Critical flicker fusion test of potential vision

PURPOSE

To continue developing a potential vision test based on the critical flicker fusion (CFF) phenomenon by using a brighter stimulus and optimizing its size.

SETTING

Flinders Eye Centre, Flinders Medical Centre, Flinders University, Bedford Park, South Australia, Australia.

METHODS

In a prospective nonrandomized study, 225 participants were assigned to 1 of 4 groups: normal, media opacity only, retinal/neural disease only, and cataract plus retinal/neural disease. Participants were recruited if they were 20 years or older but were excluded if they had a neurological disorder or medication known to affect CFF. The CFF thresholds were measured for 3 stimulus sizes: 0.5 degree, 1.0 degree, and 1.5 degrees. Discrimination between groups was tested by analysis of variance and receiver operating characteristic analysis. The relationship between visual acuity and CFF in eyes without media opacity was determined by linear regression and used to predict visual outcomes in 23 eyes having cataract surgery.

RESULTS

The mean age of the 225 participants was 71.4 years +/- 13.2 (SD); 134 (59.8%) were women. The normal group had 41 participants, and the other 3 groups had 61 participants each. Critical flicker fusion thresholds were reduced in retinal/neural disease but resistant to image degradation from media opacity. The 1.5-degree stimulus had 88% sensitivity and 90% specificity for discriminating groups. Visual acuity after cataract surgery was accurately predicted within +/-1 line in 43% of eyes, +/-2 lines in 83%, and +/-3 lines in 100%. All eyes with poor visual acuity (>0.50 logMAR) or dense cataract (>4.0 Lens Opacities Classification System III) were predicted within +/-2 lines.

CONCLUSIONS

The CFF phenomenon effectively discriminated between subjects with and without retinal/neural disease and accurately predicted visual outcome after cataract surgery. The use of a brighter stimulus enhanced performance in cases of dense media opacity.