Vision-Related Quality of Life in Keratoconus: A Save Sight Keratoconus Registry Study

Vision Improvement in Keratoconus Patients Trained With Perceptual Learning: A Randomized Controlled Trial

PURPOSE

To investigate the effectiveness and maintenance of perceptional learning (PL) on vision improvement in keratoconus (KC) patients corrected with spectacles.

DESIGN

Randomized, double-blind clinical trial.

METHODS

Non-progressive KC patients 9 years of age or older who had best spectacle-corrected distance visual acuity (CDVA) of 0 to 1.0 logMAR (Snellen equivalent range 20/20 to 20/200) and who were contact lenses intolerant were enrolled. Eligible subjects were randomized into PL and control groups to receive PL and placebo training for 3 months, respectively. Spectacle-corrected visual acuity, contrast sensitivity function (CSF), stereoacuity, and visual functioning and quality of life were measured at baseline, 3 months, and 6 months of follow-up. Statistics were analyzed following the intention-to-treat principle.

RESULTS

After 3 months of training, the CDVA of patients in the PL group improved as compared to the placebo group (0.17 ± 0.15 logMAR vs 0.02 ± 0.06 logMAR; P = .0006). Eight of 17 (47.06%) patients in the PL group reached CDVA improvement ≥2 lines (P = .0010). This improvement persisted for at least 6 months (from baseline) as compared to the placebo group (0.17 ± 0.17 logMAR vs 0.01 ± 0.07 logMAR; P = .0011). The increase in CSF in the PL group mainly was found for moderate spatial frequency (0.11 ± 0.17 log units at 3 cpd; 0.12 ± 0.19 log units at 6 cpd). Linear regression indicated that patients with worse initial CDVA achieved better gains in CDVA after PL (P = .009). No side effects were observed, and no subjects withdrew from the study because of training difficulties.

CONCLUSIONS

Three-month PL improved vision in KC patients, and the improvement was maintained after 3 months of treatment cessation. The results indicate that PL may be a promising therapy for KC patients with unsatisfied spectacle-corrected visual acuity.

Intereye Asymmetry as a Predictor of Progression in Patients With Untreated Keratoconus: Findings From a Longitudinal Study

PURPOSE

The purpose of this study was to evaluate interocular predictors of progression in patients with untreated keratoconus.

METHODS

This is a multicenter longitudinal observational study with real-world data collected through the Save Sight Keratoconus Registry. Patients between the period of June 2000 and September 2022 were included in this study. Parameters such as patient age, sex, ocular history, visual acuity, K2, Max-K, and thinnest corneal thickness pachymetry (TCT) were analyzed.

RESULTS

There were 4342 untreated eyes from 2171 patients with keratoconus. A total of 333 patients showed progression of either Max-K, TCT, or both, whereas 1838 patients showed stable parameters. Factors associated with a higher incidence of progression in Max-K were younger baseline age (HR 0.96 per year older; 95% CI 0.95-0.98, P < 0.0001) and a higher baseline intereye asymmetry in Max-K (HR 1.02 per higher diopter; 95% CI 1.00-1.04, P = 0.04). A younger baseline age was the only predictor of progression in TCT (HR 0.97 per year older; 95% CI 0.95-0.99, P = 0.001).

CONCLUSIONS

Age is the most significant predictor of progression for both corneal thinning and progression of Max-K. Interocular asymmetry in Max-K at baseline could be used as part of an algorithm for determining the risk of keratoconus progression. It is recommended that patients with higher interocular asymmetry in Max-K have a closer follow-up of both eyes as they are at a higher risk of progression.

[Effect of keratoplasty on the quality of life of keratoconus patients]

Corneal deformations caused by keratoconus produce high levels of optical aberration (OA). Despite appropriate optical correction, these alter the quality of vision and diminish the patient's quality of life, especially since the affected population is predominantly young and of working age. When thinning is too severe or corneal transparency too impaired, a corneal transplant may be considered. In this study, we compare the quality of life of patients with keratoconus in the early (stages 1 and 2) or advanced (stages 3 and 4) stages of the Krumeich classification, as well as patients who have had keratoconus treated by keratoplasty. Quality of life was assessed using the NEI-VFQ 25 questionnaire, the most widely used for keratoconus. An aberrometric examination (OQAS®; HD Analyser, Visiometrics, Terrassa, Spain) was also performed to assess patients' quality of vision. Our results show that keratoplasty provides an improvement in quality of life compared with advanced-stage keratoconus in the areas of distance (p=0.0083) and near vision (p=0.029) activities. This improvement also applies to Best-Corrected Visual Acuity (BCVA) (p=0.032) and transparency (OSI) (p=0.049). Our study shows that keratoplasty improves corneal transparency, and it is interesting to note that it improves patients' quality of life over the long term.

Evaluation of the test-retest and inter-mode comparability of the Impact of Vision Impairment questionnaire in people with chronic eye diseases

PURPOSE

The main objective of this study is to assess the test-retest and inter-administration mode reliability of the Impact of Vision Impairment profile (IVI), a common patient-reported outcome measure (PROM) for people with chronic eye diseases.

METHODS

The IVI was administered to adult patients with stable, chronic eye diseases two to four times per participant (average intervals between administrations 12 to 20 days; maximum two phone interviews, paper administration, electronic administration) by two trained interviewers. Rasch models were fit to the data. Intra-class correlation coefficients (ICCs), mean differences and Cronbach's alpha between test-retest administrations (two phone interviews) and inter-mode comparisons were calculated.

RESULTS

Two hundred-sixteen patients (mean age 67 ± 12 years, 40% male) were included in the study. The IVI met all psychometric requirements of the Rasch model, and the division into the domains of functional items (IVI_F) and emotional items (IVI_E) corresponded to the German validation study. ICCs (all for IVI_F and IVI_E, respectively) for the retest administrations were 0.938 and 0.912, and 0.853 and 0.893 for inter-mode comparisons phone/paper, 0.939 and 0.930 for phone/electronic, and 0.937 and 0.920 for paper/electronic (all p < 0.01). Mean differences (all for IVI_F and IVI_E, respectively) for the retest administrations were 2.8% and 0.7% and ranged from 2.0% to 6.2% and from 0.4 % to 4.9% between administration modes. Cronbach's alpha ranged from 0.886 to 0.944 for retest and inter-mode comparisons.

CONCLUSION

Due to the high test-retest reliability and the almost equally high comparability of different modes of administration of the IVI, the study endorses its use as a robust PROM to capture vision-related quality of life. Our results further support the use of the IVI as an endpoint in clinical trials and may simplify implementing it in both clinical trials or real-world evidence generation by offering multiple administration modes with high reliability.

The Chinese keratoconus (CKC) cohort study

The Chinese keratoconus (CKC) cohort study is a population-based longitudinal prospective cohort study in the Chinese population involving a clinical database and biobanks. This ongoing study focuses on the prevention of KC progression and is the first to involve the effect of gene‒environment interactions on KC progression. The CKC cohort is hospital-based and dynamic and was established in Zhengzhou, China; KC patients (n = 1114) from a large geographical area were enrolled from January 2019 to June 2023, with a mean age of 22.23 years (6‒57 years). Demographic details, socioeconomic characteristics, lifestyle, disease history, surgical history, family history, and visual and social function data are being collected using questionnaires. General physical examination, eye examination, biological specimen collection, and first-degree relative data were collected and analyzed in the present study. The primary focus of the present study was placed on gene, environment and the effect of gene‒environment interactions on KC progression. The follow-up of the CKC cohort study is expected to include data collection at 3 months, 6 months, and 1 year after the initial examination and then at the annual follow-up examinations. The first follow-up of the CKC cohort study was recorded. A total of 918 patients completed the follow-up by June 1, 2023, with a response rate of 82.40%. Aside from the younger age of patients who were followed up, no significant differences were found between patients who were followed up and patients who were not.

Vision-Related Quality of Life in Patients With Keratoconus With Enantiomorphic Topography After Bilateral Intrastromal Corneal Ring Implantation

PURPOSE

The aim of this study was to evaluate the quality of life (QOL) after intrastromal ring implantation in patients with keratoconus.

METHODS

This was a prospective, randomized, interventional study. We analyzed 60 eyes of 30 patients aged 16 to 35 years who were treated at the Department of Ophthalmology and Visual Sciences, Federal University of São Paulo, Brazil. The Visual Function Questionnaire (VFQ-25) and Short-Form 36 Questionnaire (SF-36) were used before intracorneal ring segment (ICRS) implantation and at 3, 6, and 12 months after surgical intervention.

RESULTS

The mean corrected visual acuity improved from a mean of 0.32 ± 0.2 logMAR (20/40) preoperatively to 0.14 ± 0.11 logMAR (20/25) 1 year postoperatively ( P = 0.001). The mean spherical equivalent varied from -7.24 ± 3.47 preoperatively to -4.13 ± 2.41 postoperatively ( P = 0.001). The overall composite score for the VFQ-25 improved from 55.1 preoperatively to 80.4 1 postoperatively ( P = 0.001). SF-36 showed statistically significant improvement in all scores. When analyzing the correlation between visual acuity and VFQ composite score, a significant correlation was found between both variables (Pearson correlation coefficient of -0.40, P = 0.001).

CONCLUSIONS

Patients with keratoconus had increased psychological symptoms and lower QOL and improved psychosocial criteria associated with corneal remodeling and decreased visual dependence on others after surgery. Extrapolation of these data to the whole keratoconus population suggests that ICRS implantation could improve QOL in these patients.

Investigating the Link Between Visual Quality and Vision-Related Quality of Life in Patients With Keratoconus

PURPOSE

The purpose of the study was to investigate the optical and visual determinants of vision-related quality of life (VR-QoL) in patients with keratoconus.

METHODS

A cross-sectional case-control study was conducted at the Department of Ophthalmology, Antwerp University Hospital, Belgium. Patients previously diagnosed with keratoconus and healthy emmetropic or ametropic volunteers were included. Patients younger than 18 years, with ametropia of more than ±10 D, or with a history of corneal surgery or relevant ocular comorbidity limiting visual acuity were excluded. Assessment included autorefraction, high-contrast visual acuity testing, corneal imaging, intraocular straylight analysis, contrast sensitivity, aberrometry, and the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25). The Rasch-modified visual functioning scale (VFS) and socio-emotional scale were used to quantify VR-QoL. Stepwise linear regression was used to investigate the association between the clinical variables and VR-QoL.

RESULTS

Seventy-seven patients with keratoconus (77 pairs of eyes) and 77 age-matched and sex-matched controls were included in the study. The scores on the VFS and the SES were significantly lower in patients with keratoconus compared with controls ( P < 0.001). Higher-order and lower-order aberrations, high-contrast visual acuity, and contrast sensitivity were poorer in patients with keratoconus ( P < 0.001). Bivariate analyses showed that spectacle-corrected high-contrast visual acuity, higher spatial frequency contrast sensitivity, and higher-order aberration metrics were strong predictors of SES ( P < 0.001) and of VFS ( P < 0.001). Higher-order aberration of the worse eye was the strongest predictor for both SES (b = 0.310, P < 0.001) and VFS (b = 0.638, P < 0.001) on stepwise regression. Contrast sensitivity was not included in the stepwise regression because of insufficient data in the keratoconus group (33/77 patients; 42.9%).

CONCLUSIONS

Both higher and lower aberration showed a strong correlation with VR-QoL, surpassing high-contrast visual acuity. These findings underline the importance of visual quality measures within keratoconus research and clinical care.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Patient-Reported Outcomes in Keratoconus: A Save Sight Keratoconus Registry Study

PURPOSE

The aim of this study was to evaluate the quality-of-life (QoL) status in keratoconus severity subgroups using the Keratoconus Outcomes Research Questionnaire (KORQ) and to determine the relationship between the QoL scores and the standard clinical variables.

METHODS

A cross-sectional study was conducted using prospective, web-based Save Sight Keratoconus Registry data. Rasch analysis was conducted on the KORQ data using the Andrich Rating Scale Model. Comparative analysis included Welch t test and 1-way ANOVA. Associations between visual acuity, corneal curvature, and minimum corneal thickness with KORQ scores were evaluated with Pearson correlation and multiple regression adjusted for age and sex.

RESULTS

The KORQ was completed by 542 patients with keratoconus (male, 67.7%; mean age, 31.6 years). Keratoconus severity, based on Kmax, was mild [<48 diopter (D)], moderate (48-55 D), and severe (>55 D) in 26.3%, 45.0%, and 28.7% of patients, respectively. Activity limitation (AL) and symptoms (SY) scales of the KORQ had robust psychometric properties including well-functioning response categories, unidimensionality, excellent measurement precision, and satisfactory fit statistics. In a group-wise analysis, the female patients had significantly lower AL and SY scores. Similarly, the severe keratoconus group had the worst AL and SY scores. Contact lens wearers had worse KORQ scores than the spectacles wearers. Overall, statistically significant but weak correlations between KORQ scores and visual acuity and corneal curvature (Kmax and K2) (Pearson r, 0.11-0.35) were observed. The correlations for SY were weaker than for AL scores.

CONCLUSIONS

Female sex, contact lens wear, reduced visual acuity, and higher disease severity were associated with worse AL and SY scores in keratoconus. Although the correlations between clinical and QoL scores were statistically significant, the low magnitudes suggested a complex relationship between clinical parameters and patient-reported outcomes.

Quality of life and tomography indices in patients with keratoconus

OBJECTIVE

Keratoconus is a corneal ectasia that leads to thinning and steepening of the corneal surface. We aimed to assess the relationship between quality of life and corneal tomography indices, irrespective of visual acuity.

METHODS

This was a cross-sectional study using a translated and validated Keratoconus Outcomes Research Questionnaire (KORQ) in Arabic language. We screened patients with keratoconus using the Belin/Ambrósio D-Index. We included the best-seeing eye in each patient with keratoconus, with a best corrected visual acuity better than 0.5. We collected variables including KORQ scores, flattest meridian keratometry, steepest meridian keratometry, mean keratometry front, maximum simulated keratometry, astigmatism front, Q value front, and thickness at the thinnest location. We performed linear regression analysis to identify predictors of the visual function score and symptom score.

RESULTS

Sixty-nine patients were included in this study, 43 (62.3%) male and 26 (37.7%) female patients, with a mean age 34.0 ± 11.50 years. The only predictor for visual function score was sex (β = 11.64, 95% confidence interval: 3.50-19.78). None of the topographic indices were related to quality of life.

CONCLUSION

In this study, quality of life in patients with keratoconus was not related to specific tomography indices and might be related to visual acuity itself.

Efficacy and Safety of Standard Corneal Cross-Linking Procedures Performed With Short Versus Standard Riboflavin Induction: A Save Sight Keratoconus Registry Study

PURPOSE

The objective of this study was to compare the effectiveness and safety of short versus standard riboflavin induction times in cross-linking (CXL) for keratoconus.

METHODS

A retrospective comparative study was conducted with data from the Save Sight Keratoconus Registry. Inclusion criteria were epithelium-off technique, standard UVA CXL protocol (3 mW/cm 2 for 30 minutes), riboflavin induction for 15 minutes (short) or 30 minutes (standard), and 1 year of follow-up data after CXL. Outcome measures included changes in best-corrected visual acuity (BCVA), keratometry in the steepest meridian (K2), maximum keratometry (Kmax), thinnest pachymetry (TCT), and adverse events. Analysis was conducted using mixed-effects regression models adjusted for age, sex, visual acuity, keratometry, pachymetry, practice, and eye laterality.

RESULTS

Two hundred eighty eyes (237 patients; mean, 27.3 ± 10.5 years old; 30% female) were included. The riboflavin induction time was short in 102 eyes (82 patients) and standard in 178 eyes (155 patients). The baseline characteristics (sex, mean age, BCVA, keratometry, and pachymetry [TCT]) were similar between the groups. At the 1-year follow-up visit, no statistically significant differences were observed in flattening in K2 and improvement in BCVA. Greater Kmax flattening [-1.5 diopters (D) vs. -0.5D, P = 0.031] and a greater proportion of >2% increase in TCT (23.5 vs. 11.3, P = 0.034) and haze (29 vs. 15, P = 0.005) were observed with short riboflavin induction.

CONCLUSIONS

Short and standard riboflavin induction times achieved similar degrees of flattening in K2 and improvement in vision. Greater improvements in Kmax and TCT were seen with short riboflavin times; however, this group had higher rates of haze.

Five-year corneal cross-linking outcomes: A Save Sight Keratoconus Registry Study

BACKGROUND

We aimed to determine the long-term outcomes of epithelium-off cross-linking (CXL) in keratoconus patients.

METHODS

An observational registry study from 41 centres across 5 countries was carried out. Primary outcomes included the mean change in visual acuity (VA), Kmax, K2, and thinnest corneal thickness (TCT) at 1-5 years. Secondary outcomes included the percentage of eyes with worsening, stable and improving outcomes.

RESULTS

There were 976 eyes of 794 patients with 1-year of complete follow-up, 501 eyes with 2-years, 355 with 3-years, 235 with 4-years and 162 with 5-years. There was a significant improvement in mean VA from baseline by 3.7 logMAR letters (p < 0.001) in year 1, and 6.9 (p < 0.001) in year 5. Mean Kmax decreased by 1.2 dioptres (D; p < 0.01) in year 1. During subsequent years the Kmax flattening appeared sustained but this was not statistically significant. K2 flattened significantly from baseline in year 1 and then remained stable. At 1 year, 4.1% patients were poor responders to CXL in terms of VA, losing ≥15 letters. The proportion of the poor responders remained unchanged: 4.9% at 5-years. The proportion of poor responders in terms of Kmax remained similar: 5.9% steepening by ≥2D at 1-year and 7.5% at 5-years. The proportion of K2 poor responders remained stable with 4.7% steepening by ≥2D at 1-year and 5.8% at 5-years.

CONCLUSIONS

Cross-linking is effective at stabilising keratoconus up to 5 years in most patients. However, a small proportion of eyes failed to stabilise and had reduced vision.

Oxygen in Corneal Collagen Crosslinking to Treat Keratoconus: A Systematic Review and Meta-Analysis

PURPOSE

Keratoconus is a disorder that results in visual loss from increased corneal high-order aberrations and irregular astigmatism and reduces quality of life. The primary treatment for progressive keratoconus is crosslinking (CXL). Recently, it has been suggested that oxygen enhances the type II photodynamic reaction of CXL that is oxygen dependent. Our study investigated the effect of increased oxygen availability in epithelium-on CXL on visual acuity and corneal curvature.

METHODS

We searched PubMed, EMBASE, Medline, Web of Science, and Scopus databases on November 3, 2021. We included studies that reported increased oxygen availability during CXL in patients with keratoconus published within the last 10 years. A meta-analysis on the primary outcomes, maximum keratometry, and corrected distance visual acuity, was conducted.

RESULTS

The search yielded 108 publications which were screened and assessed for eligibility. Six studies were included in the systematic review and 5 studies were included in our meta-analysis of the outcomes of increased oxygen availability in accelerated CXL. The meta-analysis on data after 6 months of follow-up found a significant decrease in mean maximum keratometry of 1.2 diopter (95% confidence interval: 0.2-2.3; P =0.02) and an improvement in mean corrected distance visual acuity by 0.08 logMAR (95% confidence interval, 0.02-0.13; P =0.01). There were no serious adverse events reported.

CONCLUSIONS

Increasing oxygen during epithelium-on CXL improved visual acuity and produced corneal flattening without any serious adverse events in patients with keratoconus. The demarcation line depth was significantly higher with oxygen compared to the control group. Further data are required with a control group and long-term follow-up across a range of CXL protocols for implementation into standard clinical practice.

Serum androgens and prolactin levels in patients with keratoconus

CLINICAL RELEVANCE

There is growing evidence for the involvement of sex hormones in the pathogenesis of keratoconus.

BACKGROUND

This study aimed to evaluate serum androgen and prolactin levels in patients suffering from keratoconus.

METHODS

One hundred and two subjects were enrolled in the keratoconus (76 patients) and control (26 subjects) groups in a cross-sectional survey. Topographic evaluation of the cornea was undertaken for all enrolled participants. Serum testosterone, dehydroepiandrosterone sulphate (DHEAS), prolactin (PRL), luteinising hormone (LH), and follicle-stimulating hormone (FSH) were measured in all subjects.

RESULTS

There was no significant difference in demographic characteristics between the study groups. Significantly higher mean serum levels of DHEAS (3.71 ± 2.23 vs. 2.53 ± 1.77 µg/mL; P = 0.009) and T (6.18 ± 3.80 vs. 1.57 ± 1.76 ng/mL; P < 0.001) were observed in men with keratoconus compared to controls. In females, there were also higher mean levels of DHEAS (2.40 ± 1.57 vs. 2.18 ± 0.72 µg/mL; P = 0.355) and T (0.78 ± 0.96 vs. 0.32 ± 0.13 ng/mL; P < 0.001) in patients with keratoconus but only T level reached the statistically significant level of difference. Also, the mean serum PRL level was significantly higher in women with keratoconus compared to control (13.33 ± 17.85 vs. 4.63 ± 3.10 ng/mL; P < 0.001). There was no significant difference between serum FSH and LH levels between study groups.

CONCLUSION

In patients with keratoconus, serum PRL in females and serum androgen levels in both genders are elevated.

Factors affecting quality of life in keratoconus

PURPOSE

To identify the factors affecting the quality of life (QoL) in adults with keratoconus, using the disease-specific Keratoconus Outcomes Research Questionnaire (KORQ).

METHODS

In this cross-sectional study, 574 patients with keratoconus completed the 29-item KORQ (18-item activity limitations and 11-item symptoms subscales) and demographic information. Based on mean corneal curvature to grade keratoconus severity, participants were categorised into four groups: mild <48 dioptres [D]; moderate: 48 to 53 D; advanced: 54 to 55 D and severe: >55D. Rasch analysis was used to assess the psychometric properties and to score the KORQ. Multivariable regression was performed to determine the independent impact of age, sex, laterality, severity and duration of keratoconus, education, employment status and mode of treatment for keratoconus on activity limitations and symptoms.

RESULTS

Mean (SD) age was 24.5 (5.1) years. 304 (53%), 160 (28%), 26 (4%) and 84 (15%) belonged to keratoconus groups 1, 2, 3 and 4, respectively. Rasch analysis demonstrated the 'activity limitations' and 'symptoms' KORQ subscales to possess good psychometric properties. Statistically significant associations were found between activity limitation score and the following measures: visual acuity (VA) in the better-seeing eye (r = -0.10, p = 0.01); VA in the worse-seeing eye (r = -0.09, p = 0.04) and ocular aberrations (r = -0.13, p = 0.008) in the worse-seeing eye. Statistically significant associations were also found between symptoms score and mean corneal curvature in the better-seeing eye (r = -0.10, p = 0.02). In regression models, female sex was associated with 21% worse symptom score than male (β = -0.33, 95% CI, -0.09, -0.59, p = 0.01) and working people experienced clinically and statistically significantly greater trouble from symptoms compared to those not working (β =0.44, 95% CI, 0.17, 0.70, p = 0.001).

CONCLUSIONS

People with keratoconus have poorer QoL in terms of activity limitations if they have poorer VA and greater wavefront aberrations, and in terms of symptoms if they are female and employed.

Patient-Reported Measures of the Effects of Vision Impairments and Low Vision Rehabilitation on Functioning in Daily Life

The quantification of vision impairments dates to the mid-nineteenth century with standardization of visual acuity and visual field measures in the eye clinic. Attempts to quantify the impact of vision impairments on patients' lives did not receive clinical attention until the close of the twentieth century. Although formal psychometric theories and measurement instruments were well developed and commonplace in educational testing, as well as in various areas in psychology and rehabilitation medicine, the late start applying them to clinical vision research created a vacuum that invited poorly developed and poorly functioning instruments and analytic methods. Although this research is still burdened with legacy instruments, mandates by regulatory agencies to include the patients' perspectives and preferences in the evaluation of clinical outcomes have stimulated the development and validation of self-report instruments grounded in modern psychometric theory and methods. Here I review the progress and accomplishments of applying modern psychometrics to clinical vision research. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Anterior and posterior corneal higher-order aberrations in early diagnosis and grading of keratoconus

CLINICAL RELEVANCE

Evaluation of corneal higher-order aberrations can be used clinically to diagnose early cases of keratoconus as well as to classify the severity of keratoconus.

BACKGROUND

To investigate the anterior and posterior corneal higher-order aberrations (HOAs) up to the sixth order and their ability to identify early keratoconus (KCN) as well as differentiate different severities of KCN using cross-validation analysis.

METHODS

This prospective cross-sectional comparative study was performed at a tertiary eye hospital in Tehran, Iran, in 2019. The study sample consisted of 95 eyes of 95 patients with KCN and 53 eyes of 53 normal individuals. The eyes with KCN were classified into three groups based on the Amsler-Krumeich classification system: group 1 (mild KCN), group 2 (moderate KCN), and group 3 (severe KCN). Corneal wavefront analysis was performed using Pentacam HR.

RESULTS

Based on the magnitude of AUC, posterior vertical secondary coma (Z5^-1) had an excellent discriminant ability (AUC: 0.91) and anterior vertical coma (Z3^-1) and anterior vertical secondary coma (Z5^-1) had a good discriminant ability (0.8 < AUC < 0.89) for differentiating eyes with mild KCN from normal eyes. The anterior and posterior primary spherical aberrations (Z4°) had an excellent ability (AUC > 0.9), and anterior secondary spherical aberration (Z6°) had a good ability (AUC: 0.83) for differentiating moderate from mild KCN. In the differentiation of severe from moderate KCN, anterior and posterior primary aspherical aberrations (Z4°) had a good AUC value (AUC > 0.8).

CONCLUSION

Coma-like aberrations had a good discriminant ability between normal eyes and eyes with mild KCN. Spherical aberrations showed a good ability for differentiating between different stages of KCN. The cut-off values reported in this study can be used for early detection of KCN as well as classification of KCN severity.

Comparison of deep anterior lamellar keratoplasty and corneal cross-linking in patients with advanced keratoconus

PURPOSE

To compare outcomes of deep anterior lamellar keratoplasty (DALK) and corneal cross-linking (CXL) in patients with advanced keratoconus, with the primary aim of assessing CXL as a potential therapeutic alternative.

STUDY DESIGN

Retrospective, multi-center, comparative study.

METHODS

Patients with advanced keratoconus (maximum keratometry reading (K-max) > 58D, best spectacle-corrected visual acuity worse than 0.52logMAR), undergoing either DALK or CXL treatment at four tertiary ophthalmic centers in Wenzhou, Hangzhou, Nanjing and Wuhan were included. Visual acuity, refractive error, corneal topography and complications were evaluated at baseline and at least 2 year postoperatively.

RESULTS

75 eyes of 72 patients were included, of which 37 eyes underwent DALK and 38 eyes, CXL. A larger reduction in Kmax was observed in the DALK group (-18.18 ± 9.44 D versus -1.10 ± 2.70D, p < 0.001). Seven eyes (18%) in the CXL group showed progression of keratoconus. No disease progression was observed in the DALK group. Greater improvements in best spectacle-corrected visual acuity (logMAR) were observed in the DALK group (-0.59 ± 0.25 versus -0.24 ± 0.44, p < 0.001).

CONCLUSIONS

Compared to CXL, DALK leads to larger reductions in Kmax and better improvement in visual acuity in advanced keratoconus.

Sequence of events leading to diagnosis of keratoconus and its impact on quality of life

Purpose

Early diagnosis of keratoconus (KCN) and corneal collagen cross-linking can ensure that best-corrected visual acuity is preserved. We report the sequence of events leading to the diagnosis of KCN, as well as its impact on quality of life.

Methods

This survey-based study included patients diagnosed with KCN for the first time at our center. Their corneal tomography was analyzed, and they were provided with a proforma and the NEI-VFQ-25 questionnaire and were asked to answer the given set of questions.

Results

The study included 328 eyes of 164 patients. At the time of diagnosis, 112 (68.3%) patients were not aware of a disease called "keratoconus." VKC was present in 56 patients, and 92 patients were not aware of the need to avoid eye rubbing. In total, 101 patients gave a history of sleeping more often on the side with worse KCN. The preferred primary point of contact was an optometrist for 45.1% of patients; 51.2% of patients reported never having visited an ophthalmologist. Sixty-four (39%) patients were advised a screening test to rule out KCN before presenting to our center; 42 (71.8%) of these patients did not get it done. Vision-targeted score showed a significant negative correlation with grade of KCN (r value: -0.471) and positive correlation (r value: 0.534) with LogMAR vision.

Conclusion

KCN is a disease of the young and severely affects the quality of life. Improving awareness of the general public, ensuring timely referral by optometrists, and keeping a high index of suspicion is emphasized.

Contrast sensitivity and higher-order aberrations in Keratoconus subjects

This study analyzes the relationship between contrast-sensitivity and higher-order aberrations (HOA) in mild and subclinical-keratoconus in subjects with good visual-acuity (VA). Keratoconus group (including subclinical-keratoconus) and controls underwent autokeratometry, corneal-tomography, autorefraction and HOA measurement. Contrast-sensitivity was tested using a psychophysical two-alternative forced-choice Gabor patches in three blocks (6, 9, 12 cycles/deg). Controls were compared to the keratoconus group and to a keratoconus subgroup with VA of 0.00 LogMar group ("keratoconus-0.00VA"). Spearman correlation tested association between HOA and contrast-sensitivity. Twenty-two keratoconus subjects (38 eyes: 28 keratoconus, 10 subclinical-keratoconus, 20 keratoconus-0.00VA) and 35 controls were included. There was a significant difference between control and keratoconus, and between control and keratoconus-0.00VA, for keratometry, cylinder, thinnest and central corneal thickness (p < 0.001). Controls showed lower HOA and higher contrast-sensitivity for all spatial-frequencies (p < 0.001). Most HOA were negatively correlated with contrast-sensitivity for all spatial-frequencies for keratoconus group and for 9 and 12 cycles/deg for keratoconus-0.00VA. Keratoconus subjects with good VA showed reduction in contrast-sensitivity and increased HOAs compared to controls. HOA and contrast-sensitivity are inversely correlated in subjects with mild keratoconus despite good VA. This suggests that the main mechanism underlying the decreased vision quality in keratoconus is the increase of HOA.

Quality of life in keratoconus: evaluation with Keratoconus Outcomes Research Questionnaire (KORQ)

To assess the quality of life of keratoconus patients using the Keratoconus Outcomes Research Questionnaire (KORQ), translated and validated in Portuguese language. The KORQ is the only validated keratoconus specific questionnaire and has a high rating for its psychometric properties. This cross-sectional study enrolled 100 keratoconus patients from a tertiary referral eye hospital between April 2018 and June 2019. Associations between age, sex, allergic conjunctivitis, keratoconus stage, best-corrected visual acuity (BCVA), maximum simulated keratometry (Kmax), steep keratometry (K2), pachymetry, treatments performed, hydrops, and KORQ scores were evaluated using univariate (Wilcoxon test and the Kruskal Wallis test) and multivariate linear regression with stepwise backward modeling. Lower KORQ scores are associated with better quality of life, whereas, higher scores are associated with greater impairment of functional activities and symptoms. Among the 100 patients, mild, moderate, and severe keratoconus were observed in 15%, 46% and 39% of participants, respectively. Univariate analysis showed lower function scores values, with male sex (p < 0.05) and both functional and symptom scores were significantly associated with BCVA < 0.3 (LogMAR) (p < 0.05). Multivariate analysis indicated significantly lower functional scores in individuals with BCVA < 0.3 (LogMAR) (p < 0.001) and those with a history of crosslinking treatment (p = 0.022), while symptom scores were only significantly associated with only BCVA < 0.3 (LogMAR) (p < 0.001). In patients with keratoconus, BCVA in the better eye and history of crosslinkig were factors associated with better quality of life scores using the KORQ.

Keratoconus in Africa: A systematic review and meta-analysis

PURPOSE

The aim of this review is to evaluate the prevalence of and factors associated with keratoconus in Africa.

METHOD

A systematic online literature search was conducted for articles on keratoconus in Africa. Meta-analysis was performed to estimate the prevalence of keratoconus in Africa. The Freeman-Tukey double arcsine transformation was used to minimize the effects of studies with extremely high or low prevalence estimates on the overall pooled estimates. Leave-one-out sensitivity analysis was used to assess the robustness of the pooled effects and potential outliers. Meta-regression was performed to explore associations between keratoconus, gender and age.

RESULTS

Twelve studies were included in the review; 5 from Egypt, 2 from South Africa, 2 from Kenya, 1 from Sudan, 1 from Ghana and 1 from Nigeria. Two studies were conducted in allergic conjunctivitis patients, 4 in keratoconus patients, 1 in contact lens service seekers, 1 in pre-LASIK patients, 1 in refractive patients and 1 in a student population. Eight studies were included in the meta-analysis. The overall prevalence estimate of keratoconus in Africa was 7.9% (95% CI: 2.5%-16.0%). The prevalence of keratoconus among males and females in Africa was estimated to be 9.3% (95% CI: 2.5%-19.5%) and 5.8% (95% CI: 1.5%-12.7%) respectively. The estimated prevalence of unilateral and bilateral keratoconus was 2.6% (95% CI: 0.4%-6.5%) and 5.8% (95% CI: 1.6%-12.3%), respectively. The estimated prevalence of mild keratoconus was 2.2% (95% CI: 0.7%-4.7%), moderate keratoconus was 3.5% (95% CI: 0.0%-11.8%) and severe keratoconus was 4.0% (95% CI: 0.0%-19.6%). There was no significant association between gender and the prevalence of keratoconus in Africa (p = 0.63), and age and the prevalence of keratoconus in Africa (p = 0.78).

CONCLUSION

The estimated prevalence of keratoconus reported here is higher than prevalence values reported in other meta-analyses or different geographical locations. This is mainly because studies included in this meta-analysis were either conducted on a cohort at high risk of keratoconus or a population with high possibility of finding keratoconus patients. There is a dearth of well-designed population-based studies on keratoconus in Africa, resulting in a lack of epidemiological information. This highlights the urgent need for research on keratoconus in Africa.

Outcomes of Conductive Keratoplasty Combined with Corneal Crosslinking in Advanced Ectatic Corneal Disease

Purpose

To assess the effectiveness of a novel treatment for patients with advanced corneal ectasia and loss of visual acuity (VA). Conductive keratoplasty (CK) is performed to improve VA followed by epithelium-on (epi-on) corneal crosslinking (CXL) to stabilize the cornea after CK.

Methods

Retrospective, exploratory cohort study. Patients with keratoconus or postsurgical ectasia and best spectacle-corrected distance VA (CDVA) ≤ 20/40 were included. Conductive keratoplasty was performed (ViewPoint CK System, Refractec, Inc., Bloomington, MN); followed a day later by epi-on CXL (CXLUSA/CXLO, Bethesda, MD/CXLO Encinitas, CA). Measures included uncorrected distance visual acuity (UDVA) and CDVA, as well as refractive and tomographic measures and tomographic indices.

Results

Data from 50 eyes of 45 patients were analyzed. Mean follow-up was 15.1 ± 12.2 months (range: 2 to 51). Overall, UDVA and CDVA improved postoperatively. Subjective refraction and tomographic metrics did not show consistent changes, but changes in tomographic indices were associated with treatment follow-up time. At the 1-year visit, mean UDVA significantly improved over baseline (P = 0.009) by approximately 3 lines; mean CDVA improved significantly (P = 10⁻⁵) by approximately 2 lines. No eye lost lines of CDVA. Change in the Index of Surface Variance (ISV) was associated with treatment, and the D-Index trended over follow-up time.

Conclusion

Conductive keratoplasty with a proprietary epi-on CXL treatment improved vision in patients with advanced ectasia This CK/epi-on CXL treatment offers the possibility of improved VA for patients with compromised vision due to ectasia.

Predictors of progression in untreated keratoconus: a Save Sight Keratoconus Registry study

AIMS

We set out to identify risk factors for progression in untreated keratoconus patients from 34 centres across Australia, New Zealand, Spain and Italy.

METHODS

Patients were divided into 'progressors' and 'stable' patients for each clinical parameter: visual acuity (VA), steepest keratometry (maximum keratometry (Max-K)) and thinnest corneal thickness (TCT). Primary outcomes were the proportion of eyes with sustained progression in VA, Max-K or TCT within 3 years. Secondary outcomes included predictors of progression.

RESULTS

There were 3994 untreated eyes from 2283 patients. The proportion of eyes with VA, Max-K and TCT progression at 1 year were 3.2%, 6.6% and 3.1% respectively. Factors associated with VA loss were higher baseline VA (HR 1.15 per logMAR line increase in VA; p<0.001) and steeper baseline Max-K (HR 1.07 per 1D increase; p<0.001). Younger baseline age was associated with Max-K steepening (HR 0.96 per year older; p=0.001). Thicker baseline TCT, steeper baseline Max-K and younger baseline age were associated with TCT thinning: (HR 1.08 per 10 µm increase in TCT; p<0.001), (HR 1.03 per 1D increase; p=0.02) and (HR 0.98 per year younger; p=0.01), respectively.

CONCLUSIONS

Steeper Max-K and younger age were the most clinically useful baseline predictors of progression as they were associated with worsening of two clinical parameters. Every 1D steeper Max-K was associated with a 7% and 3% greater risk of worsening VA and thinning TCT, respectively. Each 1 year younger was associated with a 4% and 2% greater risk of steepening Max-K and thinning TCT, respectively.

Efficacy of Conventional Versus Accelerated Corneal Cross-linking in Pediatric Keratoconus: Two-Year Outcomes

PURPOSE

To compare the efficacy and safety of accelerated corneal cross-linking (CXL) with conventional CXL in pediatric patients with keratoconus.

METHODS

Consecutive patients with keratoconus received either accelerated CXL (9 mW/cm² irradiance for 10 minutes) or conventional CXL (3 mW/cm² irradiance) for 30 minutes. Visual acuities (uncorrected [UDVA] and corrected [CDVA] distance visual acuity, logMAR), spherical error, cylindrical error, spherical equivalent, and keratometric values were recorded. Follow-up measurements were compared with baseline values.

RESULTS

The study enrolled 48 eyes: 22 eyes had accelerated CXL (mean age: 16.0 ± 1.7 years) and 26 eyes had conventional CXL (mean age: 15.7 ± 1.6 years). Compared with preoperative values, all mean keratometric values significantly improved in the accelerated CXL group (flat [K1]: Δ = -0.64 D, P < .0001, steep [K2]: Δ = -0.63 D, P = .009 and Kmax: Δ = -0.55 D, P = .028), but no significant changes were observed in the mean UDVA and CDVA. In the conventional CXL group, all mean keratometric values and CDVA significantly improved (K1: Δ = -0.65 D, P = .017, K2: Δ = -0.87 D, P = .006, Kmax: Δ = -1.47 D, P = .011). No significant changes were observed in refractive error in either CXL group. There were no significant differences in the keratometric readings, visual acuities, or refractive error between the two groups at the 2-year follow-up.

CONCLUSIONS

Both conventional and accelerated CXL protocols appear to be effective in stabilizing keratoconus progression in pediatric patients. Improved CDVA was also observed in the conventional CXL group. Accelerated CXL, with its advantage of shorter treatment duration, may be an alternative in pediatric patients. [J Refract Surg. 2020;36(4):265-269.].

Microbial Keratitis After Corneal Collagen Cross-Linking for Corneal Ectasia

PURPOSE

The aim of this study was to report the clinical profile and microbiological of patients with microbial keratitis post accelerated corneal collagen cross-linking (CXL).

METHODS

A retrospective case series of all patients diagnosed with microbial keratitis post-CXL who attended the Sydney Eye Hospital, Australia from January 1, 2012 to December 31, 2019 were included. Patients were identified from hospital coding and pathology data. Data were extracted from patients' medical records.

RESULTS

Eleven eyes from 10 patients with a mean age of 29 ± 11 years (range 16-48) were included. The median time of infection after CXL surgery was 4 days [interquartile range (IQR) 3-83]. Median initial and final Visual acuity at presentation were 1.3 logMAR (IQR 1-2.0) and 0.8 logMAR (IQR 0.6-1.2), respectively. The culture positivity rate was 92%, identifying 13 isolates, predominately made up of coagulase-negative Staphylococcus (n = 6, 50%) and Staphylococcus aureus (n = 3, 25%). The median epithelial healing time was 30 days (IQR 15-53).

CONCLUSIONS

Post-CXL microbial keratitis was predominately associated with gram-positive bacteria and in some cases delayed epithelialization. Microbial keratitis post-CXL may lead to moderate to poor patient outcomes.

Translation and validation of the "Questionnaire for research on keratoconus results" (KORQ) in the Colombian population

OBJECTIVE

It is proposed to carry out a process of translation and adaptation of the "Questionnaire for Research on Keratoconus Results" (KORQ) into Spanish and its validation in a Spanish-speaking population, such as Colombia. This is intended to provide a tool for measuring and monitoring the commitment to quality of life of patients with this corneal ectasia.

MATERIAL AND METHODS

A prospective analytical study was carried out, in which 200 subjects diagnosed with keratoconus completed a translated version of the KORQ questionnaire. The internal validity of the questionnaire was evaluated using Cronbach's Alpha, while its construction was evaluated by an Exploratory Factor Analysis, including a Parallel Horn Analysis for the selection of the number of underlying factors. Subsequently, 50 patients were re-selected to complete the questionnaire one week later. The repeatability of the questionnaire was measured by the Spearman test.

RESULTS

The KORQ questionnaire in its Spanish version showed some internal validity in both sections. Both sections of the questionnaire showed an essentially unidimensional behaviour. The test-retest repeatability of the test was excellent (Spearman rho> 0.95).

CONCLUSIONS

The translated version of the KORQ is valid in Colombian population.

Both Subjective Emotional Distress and Visual Handicap Correlate with Belin ABCD Classification in the Worse Eye as Measured with the "Keratoconus End-Points Assessment Questionnaire" (KEPAQ)

BACKGROUND

Keratoconus is a disease characterized by progressive corneal distortion and quality of vision. So far, no study using disease-specific scales has evaluated whether different stages of the disease correlate with higher quality of life (QoL) compromise.

METHODS

A total of 114 patients with a confirmed diagnosis of Keratoconus were included in this retrospective study. All patients underwent a clinical and a Pentacam evaluation. They were also administered the "Keratoconus End-Points Assessment Questionnaire" (KEPAQ). Belin ABCD criteria were used for Keratoconus classification. "Better eye" was defined as the eye with the lowest maximum keratometry value. Spearman Rank Order Correlation was used to determine the correlation between the different Belin criteria and the KEPAQ scores in both subscales.

RESULTS

Mean age was 28.13 ± 11.57 years, with 39.47% of patients being male. Mean score for the KEPAQ-E was 2.33 ± 3.40 Logit, while for the KEPAQ-F, it was 1.85 ± 3.61 Logit. Criteria A (anterior elevation), B (posterior elevation) and D (visual acuity) in the worse eye correlated significantly with a greater decrease in QoL (p < 0.05 for all correlations). No correlation could be found regarding the better eye.

CONCLUSION

A greater corneal distortion in the worse eye, as determined by Belin ABCD, is associated with a greater decrease in patient's QoL. Surgical improvement of the worse eye should probably be performed before surgery of the better eye, as it may provide a better response regarding the quality of life improvement.

Refractive approaches to visual rehabilitation in patients with keratoconus

PURPOSE OF REVIEW

As keratoconus is a chronic disease affecting young people, vision-related quality of life is often significantly impaired in patients with this disease. However, successful management of keratoconus, including visual rehabilitation strategies, can improve quality of life in these patients. This review will describe clinical approaches that improve vision-related quality of life in patients with stable keratoconus.

RECENT FINDINGS

Several types of contact lenses including scleral lenses have been used successfully to manage keratoconus. Eyes with severe keratoconus, even those in which fitting with other types of lenses is challenging, can be successfully fitted with scleral lenses. Although laser ablative procedures, such as photorefractive keratectomy (PRK) have been traditionally contraindicated in patients diagnosed with or suspected of having keratoconus, PRK has been attempted to partially correct refractive errors in keratoconus. Although phototherapeutic keratectomy and radial keratotomy have been reported to be used in eyes with keratoconus, effectiveness and safety results have varied. Implantation of phakic intraocular lenses and intraocular lenses, including toric intraocular lenses, which primarily correct regular astigmatism, with cataract extraction or refractive lens exchange can improve vision-related quality of life in patients with keratoconus by significantly reducing cylinder while improving uncorrected visual acuity.

SUMMARY

Appropriate selection and application of treatment options based on consideration of multiple factors will help patients with keratoconus, improving their vision-related quality of life and delaying or avoiding keratoplasty.

Development and Validation of the "Keratoconus End-Points Assessment Questionnaire" (KEPAQ), a Disease-Specific Instrument for Evaluating Subjective Emotional Distress and Visual Function Through Rasch Analysis

BACKGROUND

Keratoconus is a disease characterized by progressive distortion of the corneal anatomy, coupled with a decrease in vision. Assessing quality of life (QoL) in keratoconus is essential. So far, no instrument in the world has been designed to evaluate both visual function and emotional distress in this population. The purpose of the following study is to develop and validate the "Keratoconus End-Points Assessment Questionnaire" (KEPAQ) in a population of ectatic patients, the very first disease-specific scale to measure emotional latent traits in keratoconus.

METHODS

A last generation, Rasch analysis method was used for scale validation. First, a number of focus groups were carried out to create a pool of potential items. Then, a series of processes (such as "Content Validity Index") was carried out to develop a prior, 20-question version of the KEPAQ. Then, a study including 150 keratoconus patients was performed, followed by a careful Rasch analysis to validate and optimize both sub-scales (Emotional Compromise, KEPAQ-E, and Functional Compromise, KEPAQ-F).

RESULTS

Initially, 86 items were considered as potential elements. After test optimization, 20 items were retained. A total of 150 patients with a confirmed diagnosis of keratoconus were included for the Rasch analysis. The mean age was 29.84 ± 9.96 years. In 150 patients, 12.6% had a history of keratoplasty, 46.0% had corneal rings, and 31.3% had crosslinking. For both sub-scales, misfitting items were removed until no misfitting was determined by repetitive Rasch runs. For the final version of the KEPAQ-E sub-scale, variance explained by the model was 62.4% with a dimensional scale. Person Separation Index and Person Number of Strata were 2.43 and 3.57, respectively. For the final version of the KEPAQ-F sub-scale, variance explained by the model was 61.3% with a unidimensional scale. Person Separation Index and Person Number of Strata were 3.19 and 4.59, respectively. Both sub-scales showed excellent Person Reliability.

CONCLUSION

The KEPAQ is a robust scale, developed and validated through the latest theoretical models. It shows excellent psychometric properties, which render it extremely useful for both clinical and research use. To date, the KEPAQ is the only disease-specific scale worldwide to evaluate both functional and emotional compromise in keratoconus patients.

Diagnostic Sensitivity of Different Reference Bodies When Using Scheimpflug Tomography in a Myopic Population with Keratoconus

Purpose

To establish which reference body offers the greatest sensitivity in keratoconus (KC) diagnosis, obtain normative data for the myopic population with toric ellipsoid reference bodies, and determine the cutoff points for a population with KC.

Methods

A retrospective, observational study of the entire Scheimpflug tomographer database of the Fundación Jiménez Díaz in Madrid was conducted to identify a normal myopic and a KC myopic population. Three different reference bodies were tested on all patients: best fit sphere (BFS), best fit toric ellipsoid with fixed eccentricity (BFTEFE), and best fit toric ellipsoid (BFTE). Anterior and posterior elevation measurements at the apex and thinnest point were recorded, as well as the root mean square of posterior elevations (RMS-P). Normative data were extracted, and receiver operating characteristic (ROC) curves were generated to obtain cutoff points between the normal and KC population.

Results

A total of 301 eyes were included, comprising 219 normal myopic and 82 myopic KC eyes. BFS and BFTEFE produced the best results when measuring posterior elevation at the thinnest point. BFTE had better sensitivity with the RMS-P. From all measurements, best sensitivity (100%) was achieved with a cutoff point of 8 μm of posterior elevation at the thinnest point using the BFTEFE. BFTE was found to hide the cone in certain patients.

Conclusions

Posterior elevation measured at the thinnest point with a BFTEFE is the best-performing parameter and, therefore, is recommended to discriminate between normal and KC patients within a myopic population.