Segment Spectral Optical Coherence Tomography Research Articles

Spectral optical coherence tomography vs. fluorescein pattern for rigid gas-permeable lens fit.

BackgroundThis study aimed to evaluate anterior segment spectral optical coherence tomography (AS SOCT) for assessing the lens-to-cornea fit of rigid gas-permeable (RGP) lenses. The results were verified with the fluorescein pattern method, considered the criterion standard for RGP lens alignment evaluations.Material/MethodsTwenty-six eyes of 14 patients were enrolled in the study. Initial base curve radius (BCR) of each RGP lens was determined on the basis of keratometry readings. The fluorescein pattern and AS SOCT tomograms were evaluated, starting with an alignment fit, and subsequently, with BCR reductions in increments of 0.1 mm, up to 3 consecutive changes. AS SOCT examination was performed with the use of RTVue (Optovue, California, USA).ResultsThe average BCR for alignment fits, defined according to the fluorescein pattern, was 7.8 mm (SD=0.26). Repeatability of the measurements was 18.2%. BCR reductions of 0.1, 0.2, and 0.3 mm resulted in average apical clearances detected with AS SOCT of 12.38 (SD=9.91, p<0.05), 28.79 (SD=15.39, p<0.05), and 33.25 (SD=10.60, p>0.05), respectively.ConclusionsBCR steepening of 0.1 mm or more led to measurable changes in lens-to-cornea fits. Although AS SOCT represents a new method of assessing lens-to-cornea fit, apical clearance detection with current commercial technology showed lower sensitivity than the fluorescein pattern assessment.

Ocular and Optical Coherence Tomography–Based Corneal Aberrometry in Keratoconic Eyes Treated by Intracorneal Ring Segments

To analyze corneal and total aberrations using custom-developed anterior segment spectral optical coherence tomography (OCT) and laser ray tracing in keratoconic eyes implanted with intracorneal ring segments (ICRS). Evaluation of technology. Prospective study. Case series. Nineteen keratoconic eyes were measured before and after ICRS surgery. Anterior and posterior corneal topographic and pachymetric maps were obtained pre- and postoperatively from 3-dimensional OCT images of the anterior segment, following automatic image analysis and distortion correction. The pupil center coordinates were used as reference for estimation of corneal aberrations. Corneal aberrations were estimated by computational ray tracing on the anterior and posterior corneal surfaces. Total aberrations were measured using a custom-developed laser ray tracing aberrometer. Corneal and total aberrations were compared in 8 eyes pre- and postoperatively for 4-mm pupils. Total and corneal aberrations were highly correlated. Average root mean square of corneal and total high-order aberrations (HOAs) were 0.78 ± 0.35 μm and 0.57 ± 0.39 μm preoperatively, and 0.88 ± 0.36 μm and 0.53 ± 0.24 μm postoperatively (4-mm pupils). The anterior corneal surface aberrations were partially compensated by the posterior corneal surface aberrations (by 8.3% preoperatively and 4.1% postoperatively). Astigmatism was 2.03 ± 1.11 μm preoperatively and 1.60 ± 0.94 μm postoperatively. The dominant HOA aberrations both pre- and postoperatively were vertical coma (Z3(-1)), vertical trefoil (Z3(-3)), and secondary astigmatism (Z4(4)). ICRS decreased corneal astigmatism by 27% and corneal coma by 5%, but on average, the overall amount of HOA did not decrease significantly with ICRS treatment. OCT is a reproducible technique to evaluate corneal aberrations. OCT-based corneal aberrations and ocular aberrations show a high correspondence in keratoconic patients before and after ICRS implantation. ICRS produced a decrease in astigmatism, but on average did not produce a consistent decrease of HOAs.

Tear Meniscus Measurement by Spectral Optical Coherence Tomography

To evaluate the use of lower tear meniscus measurements obtained with anterior segment Spectral Optical Coherence Tomography (OCT) in quantitative tear evaluation and diagnosis of dry eye syndrome. To verify sensitivity and specificity of different tear meniscus parameters in diagnosis of dry eye syndrome. A total of 111 eyes in consecutive patients, mean age 34.35 years (SD, 11.17), were enrolled. Each patient completed a standard Ocular Surface Disease Index questionnaire and general ophthalmic examination. Lower tear meniscus was evaluated using Spectral OCT (RTVue, Optovue) with cornea-anterior segment lens short. Three parameters were measured: tear meniscus cross-section area (TMA, mm), tear meniscus height (TMH, mm), and tear meniscus depth (TMD, mm). Break-up time and Schirmer tests after instillation of topical anesthetic drops were also evaluated. The highest correlation with Schirmer test results was found with TMA, followed by TMH and TMD. Respective Spearman correlation coefficient values were 0.54, 0.52, and 0.3, respectively. TMA, TMH, and TMD measurements were significantly lower in dry eyes than in controls. Sensitivity and specificity for dry eye diagnosis were 80.56% and 89.33% for TMH, 86.11% and 85.33% for TMA, and 77.78% and 52.7% for TMD, respectively. There was a significant negative correlation between both TMA and TMH and Ocular Surface Disease Index questionnaire scores. Lower tear meniscus parameters measured with Spectral OCT correlate well with the Schirmer test, break-up time, and subjective symptoms. TMA and TMH measurements have high sensitivity and specificity for the diagnosis of dry eye syndrome.