Oculomotor Status, Binocular Vision, and Stereoacuity in a Series of Keratoconus Subjects

Antunes-Foschini, Rosália; Coutinho, Jean V. A. L.; Rocha, Eduardo Melani; Bicas, Harley E. A.

doi:10.1167/iovs.17-23484

Cited by 10 publications

(5 citation statements)

References 33 publications

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“…Dandapani et al 1 evaluated the wide age range of participants (8–40 years) regardless of the vergence and accommodative normative values related to the patients' age. The same problem can be observed in the study performed by Antunes-Foschini et al, 2 who evaluated keratoconus patients without categorizing the subject's age. The different age groups should be considered for assessing first, second, and third degrees of binocular vision 3–5 .…”

supporting

confidence: 56%

Letter to the Editor: Spectrum of Binocular Vision Anomalies in Keratoconus Subjects

Heirani

Askarizadeh

2021

Optom Vis Sci

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We read with interest the recent study conducted by Dandapani et al. 1 regarding binocular vision anomalies in patients with keratoconus. The authors concluded that the patients with keratoconus encounter several vergence and accommodative anomalies. They suggested that binocular vision assessment would be an essential part of the examination setting in all keratoconus patients. We would like to congratulate the authors on their informative research. However, the methodology and conclusion of the study suffer from some shortcomings.Dandapani et al. 1 evaluated the wide age range of participants (8-40 years) regardless of the vergence and accommodative normative values related to the patients' age. The same problem can be observed in the study performed by Antunes-Foschini et al., 2 who evaluated keratoconus patients without categorizing the subject's age. The different age groups should be considered for assessing first, second, and third degrees of binocular vision. [3][4][5] Also, the best-corrected visual acuity of ≤0.4 logMAR does not represent an efficient value in binocular vision studies. The vergence and accommodative examinations required satisfactory sensory status, and its prerequisite is clear vision under normal fused viewing. 6 The methodology does not support the conclusion of the study. The authors concluded that "Assessment of binocular vision should be included in the clinical examination of all keratoconus patients." In fact, the authors reported their findings without considering severe cases of keratoconic corneas.According to the myopia classification, the most common definition of low myopia is spherical equivalent of −0.50 D or less. 7 The patients with keratoconus have low myopia in the study of Dandapani et al. 1 (mean, −1.00 D; range, 0.00 to −3.50 D). Interestingly, the mean sphere, cylinder, and spherical equivalent of the patients with keratoconus are lower in the worse eyes than the better eyes of the keratoconus group. These results are surprising. As stated in the study, 58.3% of patients with keratoconus had central cones in both eyes, and 31% of participants had a central cone in one eye and a paracentral cone in the fellow eye. According to the effects of keratoconus cone location on optical characteristics of keratoconic corneas, we expect to observe higher degrees of myopia in keratoconus eyes with central cone location. 8 Based on different scoring methods for keratoconus grading, eyes with keratoconus have a wide range of severities. 9 Considering the significant clinical differences between different stages of keratoconus, it is illogical to evaluate stereopsis, fusional vergence, accommodation facility, accommodative amplitude, and phoria in such patients who had significant visual impairment and intereye differences. Consequently, we cannot assess binocular vision in all keratoconus patients. Simply classifying eyes as keratoconus versus nonkeratoconus for binocular vision assessment can lead us astray. It would be recommended to clarify the stage of keratoconus ...

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supporting

confidence: 56%

Letter to the Editor: Spectrum of Binocular Vision Anomalies in Keratoconus Subjects

Heirani

Askarizadeh

2021

Optom Vis Sci

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“…All patients with a diagnosis of atopy, noninflammatory connective disease, Down syndrome or anisometropia coming for refractive surgery should be examined carefully for signs of keratoconus. 15,16 Corneal tomography is also recommended in children with astigmatism and anisometropic amblyopia, as pediatric keratoconus could be misdiagnosed as meridional amblyopia. 17 A literature search showed a few previous studies evaluating keratoconus screening parameters of the Sirius topographer.…”

Section: Discussionmentioning

confidence: 99%

Sensitivity and specificity of Sirius indices in diagnosis of keratoconus and suspect keratoconus

Salman¹,

Darwish

Ali

et al. 2021

European Journal of Ophthalmology

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Aim To estimate the sensitivity and specificity of topographic and tomographic corneal parameters as determined by Sirius (CSO, Florence, Italy) in discriminating keratoconus (KC) and suspect keratoconus from normal cornea. Method In this retrospective case-series study, keratoconus screening indices were measured using Sirius tomographer. Receiver operating characteristics (ROC) curves were used to determine the test's overall predictive accuracy (area under the curve) and to identify optimal cut-off points to maximize sensitivity and specificity in differentiating keratoconus and suspect keratoconus from normal corneas. Results Receiver operating characteristics (ROC) curve analyses showed high predictive accuracy for Symmetry Index back (SIb), Keratoconus Vertex front (KVf), Symmetry Index front (SIf), Keratoconus Vertex back (KVb), Apex Keratometry (Curve-Apex) and Minimum corneal Thickness (ThkMin) to distinguish keratoconus from normal (area under the curve > 0.9, all). Symmetry Index back was identified as the best diagnostic parameter for detecting suspect keratoconus with AUC of 0.86. Highest specificity to detect keratoconus and suspect keratoconus was seen for SIb, 99.87% and 84.66%, respectively. These values were associated with optimal cut-off points of 0.46 D for keratoconus and 0.12 D for suspect keratoconus. Conclusion Sirius parameters evaluated in the study were effective to differentiate keratoconus from normal corneas. However, Symmetry Index back was the index with the highest ability to detect suspect keratoconus.

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“…The severity of keratoconus was also graded into mild (<48 D steepest keratometry value), moderate (48 to 53 D), severe (53 to 58 D), and advanced (>58 D) categories based on the Amsler-Krumeich classification 21 . Unlike Marella et al, 3 most cases in the present study had an interocular difference in D-index ≤10 (except one subject with an interocular D-index difference of 14) to ensure that they did not exhibit suppression of the weaker eye and had measurable stereoacuity 3,22 …”

Section: Methodsmentioning

confidence: 75%

“…21 Unlike Marella et al, 3 most cases in the present study had an interocular difference in D-index ≤10 (except one subject with an interocular D-index difference of 14) to ensure that they did not exhibit suppression of the weaker eye and had measurable stereoacuity. 3,22…”

Section: Measurement Of Visual Acuity and Corneal Topographymentioning

confidence: 99%

Interocular Contrast Balancing Partially Improves Stereoacuity in Keratoconus

et al. 2023

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SIGNIFICANCE: Partial improvement in stereoacuity may be achieved by balancing the contrast input to the two eyes of patients with bilaterally asymmetric keratoconus.PURPOSE: Interocular differences in image quality, characterized by dissimilar contrast loss and phase shifts, are implicated in stereoacuity loss in keratoconus. This study determined whether contrast balancing improves stereoacuity in this disease condition and, if so, whether it is dependent on the baseline interocular contrast imbalance.METHODS: Interocular contrast imbalance and stereoacuity of 43 subjects (16 to 33 years) with bilaterally asymmetric keratoconus were tested with spectacle correction as baseline using a binocular rivalry paradigm and random-dot stereograms, respectively. Stereoacuity measurements were repeated in a subset of 33 subjects at their contrast balance point (i.e., contrast level in stronger eye allowing balanced rivalry with 100% contrast in weaker eye) and with contrast levels biased in favor of stronger or weaker eye, all conditions in randomized order.RESULTS: Contrast imbalance level was significantly correlated with the subject's stereoacuity at baseline (r = −0.47, P = .002). The median (25th to 75th interquartile range) stereoacuity improved by 34.6% (19.0 to 65.1%) from baseline (748.8 arc sec [261.3 to 1257.3 arc sec]) to the contrast balanced condition (419.0 arc sec [86.6 to 868.9 arc sec]) (P < .001), independent of their baseline stereoacuity or contrast imbalance levels (r < 0.2, P > .26 for both). Contrast bias in favor of the weaker eye (881.3 arc sec [239.6 to 1707.6 arc sec]) worsened stereoacuity more than a bias toward the stronger eye (502.6 arc sec [181.9 to 1161.4 arc sec]), both relative to the contrast balanced condition (P < .002).CONCLUSIONS: Interocular contrast balancing partially improves stereoacuity in bilaterally asymmetric keratoconus, independent of their baseline contrast imbalance level. Cyclopean viewing may be inherently biased toward the input from the stronger eye in keratoconus.

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Oculomotor Status, Binocular Vision, and Stereoacuity in a Series of Keratoconus Subjects

Cited by 10 publications

References 33 publications

Letter to the Editor: Spectrum of Binocular Vision Anomalies in Keratoconus Subjects

Letter to the Editor: Spectrum of Binocular Vision Anomalies in Keratoconus Subjects

Sensitivity and specificity of Sirius indices in diagnosis of keratoconus and suspect keratoconus

Interocular Contrast Balancing Partially Improves Stereoacuity in Keratoconus

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