Influence of Keratoconus Severity on Detecting True Progression with Scheimpflug Imaging and Anterior Segment Optical Coherence Tomography

To determine consistent change over time in keratoconus disease, it is necessary to establish progression cut-off values based on intersession variability of the device used to monitor the cornea. The aim of this study was to analyze the accuracy of corneal parameters using Scheimpflug tomography and anterior segment optical coherence tomography in healthy and keratoconic eyes of varying severity to determine the cut-off values that indicate real progression. Three repeated measurements of each cornea of healthy (20 eyes) and keratoconic eyes (mild = 16, moderate = 25 and severe = 20) were recorded using Pentacam and Casia SS-1000 devices, which were repeated 2-3 weeks later. K1, K2, maximal anterior and posterior keratometry, and corneal thickness at the thinnest location (TCT) were collected. The accuracy was excellent with both devices; however, the Casia device presented better repeatability and reproducibility in all parameters in all groups compared to the Pentacam. The cut-off of the Pentacam and Casia in the mild stage were lower (K1 = 0.50 and 0.37 D; K2 = 0.51 and 0.37 D; Kmax-A = 1.24 and 0.65 D; Kmax-P = 0.38 and 0.17 D; TCT = 19.64 and 11.19 µm) than that of the severe stage (K1 = 1.09 and 0.88 D; K2 = 1.41 and 0.87 D; Kmax-A = 2.74 and 2.15 D; Kmax-P = 0.82 and 0.22 D; TCT = 28.68 and 14.83 µm). These results show that the greater the keratoconus severity, the greater the change that must occur for it to be considered real.

Detecting True Change in Keratoconus after Intracorneal Ring Segment Implantation

Confirming the progression of keratoconus is of paramount relevance to providing the appropriate treatment. Real change should be considered consistent over time. It must be greater than the variability of the measurement of the device used to monitor the cornea. The present study aimed to assess the intraobserver repeatability and intersession reproducibility of a Scheimpflug camera in measuring corneal parameters in virgin keratoconus and intrastromal corneal ring segments (ICRS) implantation eyes to discriminate real change from measurement noise. Sixty keratoconus and 30 ICRS eyes were included. Corneal parameters were determined in three consecutive measurements and were repeated 2 weeks later. The precision within the same session for all parameters was better in the keratoconic eyes, with mean repeatability limits 33% narrower (range 13% to 55%) compared with ICRS eyes. Mean reproducibility limits were 16% narrower (range +48% to -45%) compared with ICRS eyes. The cutoff values to consider a real corneal shape change were lower for virgin keratoconic than for ICRS, except for the thinnest corneal thickness and Stage C (ABCD system), which were the opposite. Corneal tomography measurements in ICRS eyes showed worse accuracy than in virgin keratoconus, which should be taken into account by practitioners in patients' follow up.

Optometric practices and attitudes in keratoconus patient management in Latin America

CLINICAL RELEVANCE

To explore optometric practices and attitudes in the management of keratoconus patients in LatinAmerica and how they are influenced by eye-care technology will help to minimise disease progression and their impact on patients' quality of life in Latin America.

BACKGROUND

Keratoconus is a progressive, bilateral and asymmetric corneal disorder that requires a multidisciplinary approach, the use of different eye assessment technology, and different management approaches; mainly contact lenses and surgery.

METHODS

Self-reported answers to an online survey (adapted to primary eye care) distributed via a newsletter emailed by various professional organisations across 15 Latin American countries were assessed and compared with those previously reported in three European countries.

RESULTS

Answers from 977 eye care practitioners (60%) with >10 years of experience (396 in Latin America and 581 in Europe) were assessed. A total of 65.9% of Latin American responders prescribed rigid corneal lenses (RCL), although more than half of the respondents (54.0%) would fit more RCL if they underwent further training in RCL fitting. A majority of Latin American practitioners (74.0%) considered that RCL fitting is more difficult in keratoconus, requiring more diagnostic lenses (4.6 ± 2.7; median 4; range 1-10) than are necessary for healthy eyes. Low availability of corneal topography was reported in Latin America (23%), although practitioners with topographers are more likely to prescribe RCL (92.3%) and detect more new patients with keratoconus per year (83.5%). A minority of respondents referred keratoconus patients to another optometrist (25.8%) or (40.4%) participated in comanagement with ophthalmologists.

CONCLUSION

This study provides initial evidence regarding keratoconus management in Latin America and suggests that actions are necessary to improve RCL training, facilitate eye-care technology accessibility and encourage comanagement between eye care practitioners to minimise disease progression and their impact on patients' quality of life in Latin America.

Referral pattern and co-management of keratoconus patients in primary eye care: A survey of three European countries

PURPOSE

To explore current primary care practices in keratoconus management in Portugal and compare with previous reported results in two European countries (the UK and Spain), with a special focus on interdisciplinary collaboration and referral practice patterns.

METHODS

An online survey adapted to European professional practice was distributed (via newsletters) by the Portuguese Optometrist Association to explore keratoconus patient management and referral practice patterns among Portuguese practitioners.

RESULTS

Responses of 119 optometrists were compared with previous reported of 464 eye-care practitioners (126 in the UK and 338 in Spain). Most respondents (79% in Portugal, 71% in the UK and 76% in Spain; p = 0.31) had < 5 new keratoconus patients each year. No accepted referral criterion was found (p < 0.01) because small number of the respondents (14%) in Portugal referred out at initial diagnosis (50% in the UK and Spain); 32% referred out when progression was detected (17% in the UK and 30% in Spain); and a minority (10% in Portugal, 9% in the UK, and 6% in Spain) referred out when visual acuity was affected. A majority of respondents (83%) in Portugal reported no co-management with ophthalmologists (60% in the UK and 73% in Spain; p < 0.01).

CONCLUSION

The results of this study suggest that it is necessary to encourage interdisciplinary collaboration between practitioners to improve referral of patients with suspected keratoconus to an ophthalmology specialist to change the course of this disease, to reduce keratoconus progression and visual acuity impairment and to minimize the impact of this disease on patients' quality of life.

Clinical guidelines for the management of keratoconus patients with gas permeable contact lenses based on expert consensus and available evidence

PURPOSE OF REVIEW

Fitting rigid gas permeable contact lenses (RGP CLs) in keratoconic patients is the most common visual rehabilitation option to improve patients' quality of life, but require long patient and practitioner chair time. The purpose of this review is to provide evidence-based clinical practice guidelines (CPG) in the management of patients with keratoconus with RGP CLs.

RECENT FINDINGS

An extensive literature review from 1990 to 2017 identified 354 potentially relevant publications. Fifty-two articles were reviewed and included in the CPG. An international expert panel of eight contact lens practitioners, with vast experience in keratoconus management reviewed and appraised the CPG following the Appraisal of Guidelines for Research and Evaluation II consortium requirements. The developed CPG clearly outlines a strategy for the successful fitting of RGP CLs in patients with keratoconus. This includes how to calculate parameters of the first diagnostic lens, criteria for assessing good fit and a standardized schedule of wear time and follow-up appointments.

SUMMARY

The current evidence and consensus-based CPG helps guide clinicians in a successful strategy for fitting RGP CLs in patients with keratoconus.

Gas permeable contact lens fitting in keratoconus: Comparison of different guidelines to back optic zone radius calculations

Purpose:

Compare the agreement between the finally fitted back optic zone radius (BOZR) of a spherical gas permeable (GP) contact lense (CL) with those proposed by different guidelines currently available to fit GP CLs in keratoconus.

Methods:

The BOZR fitted in 81 keratoconus eyes (46 patients) were recorded and compared with the BOZR calculated with ten different guidelines (identified after a literature review) proposed to calculate the first diagnostic lens BOZR to be fitted in keratoconus. Arithmetic and absolute mean difference between both BOZR were calculated (paired t-test). The success rate of each guideline (difference between both BOZR ≤0.05 mm) was calculated for different keratoconus stages (Amsler–Krumeich classification). Agreement between BOZR was evaluated using Bland-Altman analysis.

Results:

The BOZR proposed by all guidelines correlated with the final BOZR that was fitted (R² > 0.71; P < 0.01). A statistically significant difference was found between the BOZR suggested by all guidelines and the BOZR that was prescribed (P < 0.05), except for three Guidelines (P ≥ 0.11). CALCULENS.com presented the best agreement (mean difference of 0.00 ± 0.12 mm), and 50.6% of cases showed ≤0.05 mm of difference with the BOZR that was fitted. However, the worst guideline showed an agreement of −0.38 ± 0.22 mm, and just 3.8% of cases had ≤0.05 mm of difference with the final fitted BOZR.

Conclusion:

BOZR calculated with most of the analyzed guidelines shows statistical differences with final fitted BOZR, suggesting a lack of clinical validation of these guidelines. The selection of the BOZR with CALCULENS.com could provide a better starting point for spherical GP CL fitting in keratoconus eyes.

A comparison of two optical coherence tomography-angiography devices in pseudoexfoliation glaucoma versus primary open-angle glaucoma and healthy subjects

PURPOSE

To compare peripapillary vascular parameters derived from two optical coherence tomography angiography devices in pseudoexfoliation glaucoma, primary open-angle glaucoma, and healthy controls and to evaluate their diagnostic accuracy.

METHODS

Observational, cross-sectional study. In total, 20 eyes with pseudoexfoliation glaucoma, 20 primary open-angle glaucoma eyes matched by peripapillary retinal nerve fiber layer thickness, and 20 control eyes were recruited. Participants underwent standard automated perimetry and peripapillary retinal nerve fiber layer analysis by Optovue and Cirrus optical coherence tomography. Vascular parameters provided by Angiovue and Angioplex optical coherence tomography angiography were compared. Their diagnostic accuracy and correlation with structural and functional parameters were assessed.

RESULTS

All peripapillary optical coherence tomography angiography vascular parameters were significantly different among groups (all p < 0.05). The whole image capillary density and peripapillary capillary density by Angiovue were significantly lower in pseudoexfoliation glaucoma compared with primary open-angle glaucoma (p = 0.009 and p = 0.001, respectively). Conversely, vascular parameters by Angioplex were not statistically different between primary open-angle glaucoma and pseudoexfoliation glaucoma. A good correlation was found using Angiovue between whole image capillary density and visual field mean deviation (0.758, p < 0.001), peripapillary capillary density and visual field mean deviation (0.729, p = 0.001), and peripapillary capillary density and peripapillary retinal nerve fiber layer thickness in eyes with pseudoexfoliation glaucoma (0.716, p = 0.001). Angiovue parameters showed higher area under the receiver operating characteristic curves than Angioplex to discriminate among groups.

CONCLUSION

Only Angiovue detected a significantly lower capillary density in pseudoexfoliation glaucoma compared to primary open-angle glaucoma at similar glaucoma damage. Both, Angiovue and Angioplex demonstrated a decreased capillary density in glaucoma eyes compared to healthy eyes. Furthermore, Angiovue-derived vascular parameters showed better correlation with functional and structural parameters and a higher diagnostic capacity to discriminate among groups compared to Angioplex.

Current optometric practices and attitudes in keratoconus patient management

PURPOSE

To compare the current optometric practices and attitudes in the management of keratoconus patients in the UK and Spain.

METHODS

An online survey (adapted to optometric practices) was distributed via a newsletter emailed by various professional organizations in the UK and Spain.

RESULTS

Four hundred and sixty-four practitioners (126 in the UK; 338 in Spain) who prescribed gas permeable GP contact lenses (CLs) more than once per month (54.8% of UK practitioners and 28.1% of practitioners in Spain; p<0.01) responded to the questionnaire. A combination of multiple factors is considered necessary in the keratoconus detection (79.4% in the UK, 75% in Spain; p=0.68), and the use of classification criteria is considered relevant (67.5% in the UK, 70.7% in Spain; p=0.49). There is a high consensus on the consideration that GP CL fitting is more difficult in keratoconus (79.4% in the UK, 80.5% in Spain; p=0.79) requiring more diagnostic lenses (3.2±1.4 and 3.4±1.2 in the UK and Spain, respectively; p=0.72) than are necessary for healthy eyes. Using corneal topography is uncommon from both countries (38.1% in the UK, 59.8% in Spain; p<0.01), with a similar ophthalmologist referral pattern (at initial diagnosis, 50% in both the UK and Spain; p=1.00). Few cases of co-management with ophthalmologists were noted (no co-management reported by 60.3% in the UK and 72.8% in Spain, p=0.01).

CONCLUSION

This study provides initial observations and evidence regarding keratoconus management by optometrists in the UK and Spain and shows similarity in the professional practices and attitudes of practitioners in these two countries.

Repeatability of Wavefront Aberration Measurements With a Placido-Based Topographer in Normal and Keratoconic Eyes

PURPOSE

To determine and compare the repeatability of anterior corneal higher order aberrations (HOAs) using a Placido-based topographer (Allegro Topolyzer; WaveLight Technologie AG, Alcon Laboratories, Erlangen, Germany) in a sample of normal and keratoconic eyes.

METHODS

Three repeated measurements of each cornea of normal and keratoconic eyes were taken with the Allegro Topolyzer. Repeatability of the HOAs (3rd- and 4th-order individual values and normalized polar Zernike coefficients, coma-like, root mean square (RMS) up to 8th-order values, HOA RMS, and total RMS for 6-mm pupil diameter) and central corneal power (3-mm pupil) were analyzed. Within-subject standard deviation (Sw), precision, repeatability, coefficient of variation (CV), and the intraclass correlation coefficient (ICC) were calculated.

RESULTS

Zernike coefficients were significantly different between the normal (36 eyes of 36 patients) and keratoconus (36 eyes of 36 patients) groups (P ≤ .03) except in Z(+1) 3, Z(+3) 3, Z(-4) 4, and Z(+4) 4. In the normal group, Sw was 0.031 µm or less, CV ranged from 6.49% (spherical aberration) to 37.18% (secondary astigmatism), and ICC values ranged from 0.227 to 0.982. In the keratoconus group, Sw was 0.059 µm or less, CV ranged from 2.06% (total RMS) to 25.82% (tetrafoil), and ICC values ranged from 0.839 to 0.996. In analyzing the keratoconus stages (Amsler-Krumeich classification), the repeatability of the Zernike coefficients tended to improve with increasing keratoconus stage.

CONCLUSIONS

The repeatability of corneal wavefront aberration provided by the Allegro Topolyzer was better in keratoconic eyes (good and moderate repeatability) than in normal eyes (moderate and poor repeatability). These results are important to eye care practitioners and refractive surgeons during refractive surgery planning or keratoconus detection, classification, and management. [J Refract Surg. 2016;32(5):338-344.].

Advantages, limitations, and diagnostic accuracy of photoscreeners in early detection of amblyopia: a review

Amblyopia detection is important to ensure proper visual development and avoid permanent decrease of visual acuity. This condition does not produce symptoms, so it is difficult to diagnose if a vision problem actually exists. However, because amblyopia treatment is limited by age, early diagnosis is of paramount relevance. Traditional vision screening (conducted in <3 years) is related with difficulty in getting cooperation from a subject to conduct the eye exam, so accurate objective methods to improve amblyopia detection are necessary. Handheld devices used for photoscreening or autorefraction could offer advantages to improve amblyopia screening because they reduce exploration time to just few seconds, no subject collaboration is needed, and they provide objective information. The purpose of this review is to summarize the main functions and clinical applicability of commercially available devices for early detection of amblyopia and to describe their differences, advantages, and limitations. Although the studies reviewed are heterogeneous (due to wide differences in referral criteria, use of different risk factors, different types of samples studied, etc), these devices provide objective measures in a quick and objective way with a simple outcome report: retest, pass, or refer. However, due to major limitations, these devices are not recommended, and their use in clinical practice is limited.

Keratoconus Screening in Primary Eye Care – A General Overview

Keratoconus early detection (screening) and diagnosis requires an in-deep corneal analysis with different techniques; slip lamp assessment, corneal topography and corneal tomography are the most commonly accepted to detect clinical signs and assess anterior and posterior corneal surface and global corneal pachymetry. However, keratoconus early detection and definitive diagnosis are two different clinical procedures that require a different approach and goals. The aim of this review is to provide some general information about different corneal assessment technology, useful in keratoconus patient assessment; highlighting the differences in the adequate investigation techniques to its detection in primary eye care clinic and to conduct the definitive diagnosis (usually in a cornea specialist clinic). Information of most extensively available commercial devices and the advantages and disadvantages of their use in keratoconus early detection and diagnosis are described. In conclusion, corneal topography (Placido-based keratographers) plays a significant role in keratoconus detection, especially in primary eye care clinics. However, corneal tomography (with different slit scanning and/or rotational imaging devices) including posterior corneal surface assessment and global corneal pachymetry investigation, is critical in definitive keratoconus diagnosis.