The value of preoperative electro-ophthalmological examination before cataract extraction

Predicting visual outcomes in keratoprosthesis surgery with critical flicker fusion frequency, B-scan, visual electrophysiology and endoscopy

PURPOSE

This study evaluates the predictive power of the critical flicker fusion frequency (CFF) test for visual outcomes in keratoprosthesis (KPro) candidates, comparing its accuracy with B-scan ultrasound, flash visual evoked potentials (fVEP) and endoscopy.

METHODS

The study included 42 patients (42 eyes) scheduled for KPro surgery with a median follow-up period of 6 months. The receiver operating characteristic curve identified the cut-off threshold for CFF in the model development study (17 eyes). All patients in the comparison study (25 eyes) underwent preoperative assessments including trichromatic CFF (red, green and yellow), B-scan ultrasound, fVEP and perioperative endoscopy. Results were classified as either favourable or unfavourable predictors of visual outcomes based on predefined criteria. Sensitivity and specificity of each assessment were calculated based on postoperative best-corrected visual acuity (BCVA)≥20/200. The Bland-Altman test assessed the consistency between CFF-predicted BCVA and actual BCVA.

RESULTS

Among the trichromatic CFF tests, the yellow-CFF (yCFF) exhibited the highest area under the curve value of 0.97 and a cut-off threshold at 10 Hz for predicting postoperative BCVA≥20/200 (p<0.05). yCFF achieved 90% sensitivity and 80% specificity in predicting satisfactory postoperative outcomes. Endoscopy had 80% sensitivity and 80% specificity, B-scan showed 70% sensitivity and 60% specificity, and fVEP had 75% sensitivity and 40% specificity. yCFF showed a mean bias of 0.091 logarithm of the minimum angle of resolution (logMAR) in postoperative prediction.

CONCLUSIONS

The CFF test provides robust visual function evaluation in KPro candidates. It demonstrates superior predictive accuracy for visual prognosis compared with routine ophthalmologic examinations, such as B-scan ultrasonography, fVEP and endoscopy.

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.

Analysis of postoperative intraocular pathologies in patients with mature cataracts

Purpose

To examine the prevalence and risk factors of intraocular pathologies after mature cataract surgery.

Methods

The medical records of 115 patients (115 eyes) diagnosed with brunescent or white cataracts, who underwent surgery at a single primary center between January 2018 and August 2021 were retrospectively reviewed. Dense cataracts precluded preoperative fundus examination in all eyes; however, patients with fundus examination results within 3 months after cataract surgery were included. Logistic regression analyses were performed to identify factors associated with intraocular pathologies.

Results

Intraocular pathologies were observed in 37 eyes (32.2%) 11.8 ± 13.9 days postoperatively. The most common abnormalities were drusen (6.1%), myopic degeneration (5.2%) and diabetic retinopathy (4.3%). Intraocular pathology in the fellow eye was associated with posterior segment pathology in mature cataract eyes (odds ratio, 47.72; P < 0.001).

Conclusions

The prevalence of each intraocular pathology found after mature cataract surgery was unremarkable. This study provides clinically useful evidence for clinicians to explain the risk of posterior segment pathology in patients with mature cataracts.

What can visual electrophysiology tell about possible visual-field defects in paediatric patients

Recognising a potential visual-field (VF) defect in paediatric patients might be challenging, especially in children before the age of 5 years and those with developmental delay or intellectual disability. Visual electrophysiological testing is an objective and non-invasive technique for evaluation of visual function in paediatric patients, which can characterise the location of dysfunction and differentiate between disorders of the retina, optic nerve and visual pathway. The recording of electroretinography (ERG) and visual-evoked potentials (VEP) is possible from early days of life and requires no subjective input from the patient. As the origins of ERG and VEP tests are known, the pattern of electrophysiological changes can provide information about the VF of a child unable to perform accurate perimetry. This review summarises previously published electrophysiological findings in several common types of VF defects that can be found in paediatric patients (generalised VF defect, peripheral VF loss, central scotoma, bi-temporal hemianopia, altitudinal VF defect, quadrantanopia and homonymous hemianopia). It also shares experience on using electrophysiological testing as additional functional evidence to other tests in the clinical challenge of diagnosing or excluding VF defects in complex paediatric patients. Each type of VF defect is illustrated with one or two clinical cases.

The Success of Cataract Surgery and the Preoperative Measurement of Retinal Function by Electrophysiological Techniques

Purpose. To study the effect of different electrophysiological methods to evaluate retinal function prior to cataract surgery. Methods. Cataract patients who had no significant other eye disease were chosen. VA, pattern visual evoked potential (PVEP), electroretinogram (ERG), and multifocal electroretinogram (mfERG) responses were measured from 150 cataract patients and 20 control subjects. Results. When the preoperative VA was more than 0.3 in cataract patients, the amplitude of PVEP was not significantly different between cataract and control subjects. The amplitude of central point mfERG was significantly lower in cataract patients compared with control group from HM to 0.8 of preoperative VA. The 95% confidence intervals (CIs) of the amplitudes of center point mfERG were calculated for a range of preoperative VA values. Most of the patients within 95% CI of the center point mfERG had a postoperative VA more than 0.5. Conclusions. The amplitude of central point mfERG in cataract patients was the most relevant parameter to the preoperative VA compared with PVEP and ERG. The 95% CI of the amplitude of central point mfERG for each level of VA could help to evaluate preoperative macular function which is used to predict the outcome of cataract surgery.

The electroretinogram in diabetic retinopathy

Electroretinography (ERG) is an objective method of evaluating retinal function. Since its introduction to clinical practice in the 1940s, it has become a useful and routine diagnostic clinical tool in ophthalmology. This review summarizes the role of ERG as a clinical technique for evaluating the progression of diabetic retinopathy and as a research tool for increasing our understanding of the pathophysiology of diabetic retinopathy. Most studies show unequivocally that the different types of ERG tests detect local abnormalities or widespread pathology, even in very early stages of the disease. It seems plausible that measurements from ERG recordings, particularly the oscillatory potentials, may be useful for predicting progression from nonproliferative to the more sight-threatening stages--preproliferative or proliferative--of diabetic retinopathy. Some recent work implies that the ERG can also be a useful diagnostic method for discriminating between eyes with diabetic retinopathy and those without the condition.

Electrophysiological testing of eyes with opaque media

Electrodiagnostic tests as applied to the eye are now widely used in the investigation of patients with inherited retinal degenerations but their value in patients with opaque media is perhaps less well recognised. The choice of stimulus is all important and a flash VEP and flash ERG probably provide the best combination of tests at present. A comparison with the fellow eye, if it is normal, greatly improves the value of the result. A pitfall of this type of test is its failure to detect amblyopia and a carefully recorded history is important in helping to interpret the traces.

Preoperative prediction of postoperative visual acuity in patients with cataracts: a quantitative review

Many tests of visual function have been proposed as means of preoperatively evaluating cataract patients' surgical outcomes. It is impractical to compare all of these tests simultaneously on the same group of patients. Quantitative reviews apply quantitative methods to comparisons across studies. We compared the results of 52 reports in which cataract patients' postoperative acuity was predicted by means of visually evoked potential, laser interferometry, or projection tests (potential acuity meters-pinhole). The results of each study were summarized in a 2 x 2 contingency table. Summary statistics were compared by means of analysis of variance and post hoc tests. Despite difficulties in metaanalysis, we found the visually evoked potential a better predictor with dense opacities. We recommend standardization in a quest for more precise predictions of postoperative visual acuity.

10-Hz flash visual evoked potentials predict post-cataract extraction visual acuity

Cataract patients suspected of having disease which might interfere with good postoperative visual function were referred for evaluation. Monocular steady-state luminance visual evoked potentials (VEPs) were elicited with closed eyes at a stimulus rate of 10 flashes/sec. VEPs were rated as either normal or abnormal. Patients with normal VEPs were predicted to have an acuity of 6/15 (20/50) or better. Patients with abnormal VEPs were predicted to have acuities of 6/18 (20/60) or worse. Postoperative acuities were determined for all patients who underwent surgery and who had no intraoperative or early postoperative complications. The association of preoperative VEPs and observed postoperative acuities were quantitatively compared by a 2 x 2 contingency table for the 59 eyes which met these criteria. The chi-square was significant (p less than 0.001). The overall accuracy of prediction was 76%. Accuracy was 80% for patients with a preoperative acuity of 6/60 (20/200) or better and 75% for those whose postoperative acuity was 6/120 (20/400) or worse. This difference was not statistically significant.

Evaluation of the central retina and optic nerve function in media opacities

Conventional electroretinogram (ERG) and pattern VECP (or visual evoked cortical potential) are of limited value in estimating visual function in eyes with media opacities. We used a method consisting of flicker ERG and flicker VECP to successfully overcome this limitation. Three of 25 eyes with cataract had a reduced flicker VECP. These 3 patients also had a history of glaucomatous optic nerve damage. Normal flicker VECP was found in some patients with reduced flicker ERG or reduced scotopic and photopic a-wave. Analysis of the results showed that the flicker VECP is independent of the ERG and flicker ERG. Utilizing this method we could rule out maculopathy and optic nerve damage in patients with media opacities as well as recognize optic nerve damage in patients with coexisting maculopathy.

Retinal visual acuity with pattern VEP normal subjects and reproducibility

Retinal visual acuity was determined using an objective method by means of VEP. Sixty subjects with subjective visual acuity ranging from 20/25 to 20/12 were measured with a computer-controlled laser interferometer, using interference fringes modulated in counterphase as pattern-reversal stimulus. Steady-state VEPs taken at different spatial frequencies were evaluated by Fourier analysis and linear regression. Objective retinal acuity was calculated as the intersection between the linear regression line and the linear scaled spatial frequency axis. In 68% of all cases, the difference between objective and subjective visual acuity was less than +/- 5.1 cycles per degree (c/d) (+/- 15.4% referred to subjective acuity); in 86%, the difference was less than +/- 7.7 c/d (+/- 23.1%).