Effect of contact lenses on ocular biometric measurements based on swept-source optical coherence tomography / Efeito de lentes de contato em um biômetro ocular baseado na tomografia de coerência óptica de varredura

ABSTRACT Purpose: To determine the reliability of swept- source optical coherence tomography in cases in which soft contact lenses cannot be removed when acquiring biometric measurements. Methods: Eight subjects were included and only one eye per participant was analyzed. Each eye was measured six times by swept-source optical coherence tomography with the IOLMaster 700 instrument (Carl Zeiss Meditec, Jena, Germany). Axial length, central corneal thickness, anterior chamber depth, lens thickness, and keratometric measurements were evaluated for the naked eye and while wearing soft contact lenses of three different powers (-1.5, -3.0, and +2.0 D). Results: There were statistically significant changes in axial length, central corneal thickness, anterior chamber depth, and keratometric measurements with soft contact lenses as compared to the naked eye (p<0.001). However, there were no significant differences in lens thickness outcomes between the naked eye and while wearing the three soft contact lenses (p>0.5). The changes in axial length, central corneal thickness, and anterior chamber depth were lens-specific and dependent on the thickness of the lens used. Conclusions: Sept-source optical coherence tomography based lens thickness measurements while wearing soft contact lenses are comparable to those of the naked eye. However, the thickness and the optical design of the soft contact lens may lead to significant differences in the axial lengh, central corneal thickness, anterior chamber deph, and keratometric measurements.

RESUMO Objetivo: Determinar a confiabilidade da tomografia de coerência óptica de varredura em casos especiais em que lentes de contato gelatinosas não podem ser removidas ao realizar medições biométricas. Métodos: Oito indivíduos foram incluídos e apenas um olho por participante foi analisado. Cada olho foi medido seis vezes por tomografia de coerência óptica de varredura com o instrumento IOLMaster 700 (Carl Zeiss Meditec, Jena, Alemanha). O comprimento axial, a espessura central da córnea, a profundidade da câmara anterior, a espessura da lente e as medidas ceratométricas foram avaliados a olho nu e enquanto usavam lentes de contato gelatinosas de três diferentes potências (-1,5, -3,0 e +2,0 D). Resultados: Houve alterações significativas no comprimento axial, espessura central da córnea, profundidade da câmara anterior e medidas ceratométricas com as lentes de contato gelatinosas em comparação com as a olho nu (p<0,001). No entanto, não houve diferenças significativas nos resultados de espessura do cristalino entre o olho nu e enquanto usava as três lentes de contato gelatinosas (p>0,5). As alterações de comprimento axial, espessura central da córnea e profundidade da câmara anterior foram específicas da lente e dependentes da espessura da lente usada. Conclusões: As medições da espessura da lente baseadas na tomografia de coerência óptica da Sept-source, enquanto usam lentes de lentes de contato gelatinosas, são comparáveis às do olho nu. Entretanto, a es pessura e o desenho óptico da lente de contato gelatinosa podem levar a diferenças significativas no comprimento axial, na espessura central da córnea, na profundidade da câmara anterior e nas medidas ceratométricas.

Effect of contact lenses on ocular biometric measurements based on swept-source optical coherence tomography.

PURPOSE: To determine the reliability of swept- source optical coherence tomography in cases in which soft contact lenses cannot be removed when acquiring biometric measurements. METHODS: Eight subjects were included and only one eye per participant was analyzed. Each eye was measured six times by swept-source optical coherence tomography with the IOLMaster 700 instrument (Carl Zeiss Meditec, Jena, Germany). Axial length, central corneal thickness, anterior chamber depth, lens thickness, and keratometric measurements were evaluated for the naked eye and while wearing soft contact lenses of three different powers (-1.5, -3.0, and +2.0 D). RESULTS: There were statistically significant changes in axial length, central corneal thickness, anterior chamber depth, and keratometric measurements with soft contact lenses as compared to the naked eye (p<0.001). However, there were no significant differences in lens thickness outcomes between the naked eye and while wearing the three soft contact lenses (p>0.5). The changes in axial length, central corneal thickness, and anterior chamber depth were lens-specific and dependent on the thickness of the lens used. CONCLUSIONS: Sept-source optical coherence tomography based lens thickness measurements while wearing soft contact lenses are comparable to those of the naked eye. However, the thickness and the optical design of the soft contact lens may lead to significant differences in the axial lengh, central corneal thickness, anterior chamber deph, and keratometric measurements.

Ocular biometric changes with different accommodative stimuli using swept-source optical coherence tomography.

PURPOSE: To evaluate ocular biometric changes with different accommodative stimuli using a new swept-source optical biometer. METHODS: Only the right eye was analyzed. Each subject was measured six times with the IOLMaster 700 swept-source optical biometer (Carl Zeiss Meditec, Jena, Germany) with the subject looking at the stimulus shown by the instrument and with the subject looking at a target placed outside the instrument at 0D of vergence. Axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT), white-to-white (WTW), and keratometry readings (K1 and K2) were evaluated in both cases. To assess if the changes found may affect the intraocular (IOL) power calculation for surgical applications, we have applied some formulae, using the software provided by the optical biometer manufacturer, to the ocular parameters found in both situations for three different types of IOLs. RESULTS: No statistically significant differences were found for AL, CCT, WTW, K1 and K2 between the subject looking at the stimulus of the biometer and looking at the outside target at 0D of vergence (p > 0.05). However, the measurement of ACD revealed a statistically significant reduction of 20 microns (p = 0.03) and, on the contrary, LT increased significantly 30 microns (p = 0.02). ACD and LT changes were highly correlated (R2 = 0.91). As for the IOL power calculation, in all cases, the mean change was lower than 0.25 D both for IOL power selection and residual refraction. CONCLUSIONS: Although ACD and LT change significantly with different accommodative stimuli measured by swept-source optical biometry, these changes are not clinically relevant.

Ocular anatomic changes for different accommodative demands using swept-source optical coherence tomography: a pilot study.

PURPOSE: The purpose of our study was to assess the changes in ocular parameters for different accommodative demands using a new optical biometer based on swept-source optical coherence tomography (SS-OCT). METHODS: Seven subjects were included in this pilot study, and only one eye per participant was analyzed. Each eye was measured six times with the optical biometer IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). As this instrument is not able to change the vergence of the stimulus, to enable measurements at different accommodative states, a tilted first-surface mirror attached to the optical biometer was used to place the fixation stimulus at different vergences. Measurements were taken on the right eye of the subject while the left eye was looking through the mirror. Central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), axial length (AL), white-to-white (WTW) distance and keratometric readings were evaluated for three different accommodative states: 0.0 diopters (D), 1.5 D, and 3.0 D. RESULTS: No statistically significant differences were found for CCT, AL, WTW, K1 and K2 between the three accommodative states. As expected, changing the accommodative condition did not change CCT, AL, WTW, and keratometric outcomes. Nevertheless, statistically significant differences between the accommodative states were found for ACD and LT measurements. In addition, variations in ACD correlated linearly with variations in LT (R2 ≥ 0.99) when changing the vergence of the optotype. CONCLUSION: A practical methodology to assess the changes in ocular parameters for different accommodative demands using the IOLMaster 700 based on SS-OCT has been described. Statistically significant changes that have been found that agree well with previous reports.

Evaluation of the repeatability of a swept-source ocular biometer for measuring ocular biometric parameters.

PURPOSE: The purpose was to evaluate the repeatability of a new swept-source optical biometer for measuring ocular biometric parameters. METHODS: Thirty subjects with healthy and phakic eyes were included in this study, and only one eye per participant was analysed. Each eye was measured five times with the IOLMaster 700 swept-source optical biometer (Carl Zeiss Meditec, Jena, Germany). Axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT), white-to-white (WTW), and K1 and K2 keratometric readings were evaluated. The repeatability of swept-source biometry was evaluated on the basis of five measurements captured for each patient. RESULTS: The repeatability limits for the axial measurements AL, ACD, CCT, and LT were 0.03, 0.07, 0.004, and 0.11 mm, respectively. For the WTW distance and both keratometry readings, the repeatability limits were 0.20, 0.06, and 0.05 mm, respectively. The AL resulted in the lowest coefficient of variation, and the LT had the highest one. The spherical equivalent showed statistically significant negative correlations with the AL and ACD. CONCLUSION: Swept-source optical biometry showed high repeatability performance for all biometric parameters in healthy eyes, where the correlation between the spherical equivalent and AL showed the strongest value.