Effect of corneal curvature on optical zone decentration and its impact on astigmatism and higher-order aberrations in SMILE and LASIK.

PURPOSE: To determine the association between anterior corneal curvature and optical zone centration as well as its impact on aberration profiles in small-incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). METHODS: Seventy-eight eyes of 78 patients treated with SMILE (45 eyes) and LASIK (33 eyes) were included. The centration of the optical zone was evaluated on the instantaneous curvature difference map between the preoperative and 3-month postoperative scans using a superimposed set of concentric circles. The correlation between optical zone decentration and anterior keratometry values was evaluated. The effect of optical zone decentration on vector components of astigmatic correction and induction of higher-order aberrations (HOA) was assessed. RESULTS: The mean decentration distance was 0.21 ± 0.11 mm for SMILE and 0.20 ± 0.09 mm for LASIK (p = 0.808). There was a significant correlation between anterior keratometric astigmatism and decentration distance (r = 0.653, p < 0.001) for SMILE but not for LASIK (r = - 0.264, p = 0.138). Astigmatic correction was performed in 67 eyes. Optical zone decentration and the vector components of astigmatic correction were not correlated (p ≥ 0.420). Significant correlation was demonstrated between the decentration distance and the induced total coma (SMILE: r = 0.384, p = 0.009; LASIK: r = 0.553, p = 0.001) as well as the induced total HOA (SMILE: r = 0.498, p = 0.001; LASIK: r = 0.555, p = 0.001). CONCLUSION: Anterior cornea astigmatism affected the treatment centration in SMILE but not LASIK. Subclinical decentration was associated with the induction of total coma and total HOA, but it did not affect the lower-order astigmatic correction.

Non-mydriatic ultrawide field scanning laser ophthalmoscopy compared with dilated fundal examination for assessment of diabetic retinopathy and diabetic macular oedema in Chinese individuals with diabetes mellitus.

AIMS: To evaluate the performance of ultrawide field scanning laser ophthalmoscopy (UWF-SLO) for assessing diabetic retinopathy (DR) and diabetic macular oedema (DME) in a Chinese population, compared with clinical examination. METHODS: This is a retrospective cohort study. A series of 322 eyes from 164 patients with DM were included. Each patient underwent both dilated fundal examination with DR and DME grading by retina specialist and non-mydriatic 200° UWF-SLO (Daytona, Optos, Dunfermline, UK). The severity of DR and DME from UWF-SLO images was further graded by ophthalmologists, according to both international clinical DR and DME disease severity scales and the standard 7-field Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Any DR, DME and vision-threatening DR (VTDR) were treated as endpoints for this study. RESULTS: 23 out of 322 images (7.14%), including all four cases with proliferative DR on clinical examinations, were determined as ungradable. When the international scale was used for grading UWF-SLO images, the sensitivity of any DR, DME and VTDR was 67.7%, 67.4% and 72.6%, respectively; the specificity of any DR, DME and VTDR was 97.8%, 97.3% and 97.8%, respectively. The agreement with clinical grading in picking up any DR, DME and VTDR was substantial, with κ-values of 0.634, 0.694 and 0.707, respectively. The performance of UWF-SLO was shown to be lower when ETDRS scale was used for grading the images. CONCLUSION: The performance of non-mydriatic UWF-SLO is comparable in identifying DR with that of clinical examination in a Chinese cohort. However, whether UWF-SLO can be considered as tool for screening DR is still undetermined.

Author Correction: Determinants of Quantitative Optical Coherence Tomography Angiography Metrics in Patients with Diabetes.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Using Retinal Imaging to Study Dementia.

The retina offers a unique "window" to study pathophysiological processes of dementia in the brain, as it is an extension of the central nervous system (CNS) and shares prominent similarities with the brain in terms of embryological origin, anatomical features and physiological properties.  The vascular and neuronal structure in the retina can now be visualized easily and non-invasively using retinal imaging techniques, including fundus photography and optical coherence tomography (OCT), and quantified semi-automatically using computer-assisted analysis programs. Studying the associations between vascular and neuronal changes in the retina and dementia could improve our understanding of dementia and, potentially, aid in diagnosis and risk assessment.  This protocol aims to describe a method of quantifying and analyzing retinal vasculature and neuronal structure, which are potentially associated with dementia. This protocol also provides examples of retinal changes in subjects with dementia, and discusses technical issues and current limitations of retinal imaging.

Determinants of Quantitative Optical Coherence Tomography Angiography Metrics in Patients with Diabetes.

Early microvascular damage in diabetes (e.g. capillary nonperfusion and ischemia) can now be assessed and quantified with optical coherence tomography-angiography (OCT-A). The morphology of vascular tissue is indeed affected by different factors; however, there is a paucity of data examining whether OCT-A metrics are influenced by ocular, systemic and demographic variables in subjects with diabetes. We conducted an observational cross-sectional study and included 434 eyes from 286 patients with diabetes. Foveal avascular zone (FAZ) area, FAZ circularity, total and parafoveal vessel density (VD), fractal dimension (FD), and vessel diameter index (VDI) from the superficial capillary plexus OCT-angiogram were measured by a customized automated image analysis program. We found that diabetic retinopathy (DR) severity was associated with increased FAZ area, decreased FAZ circularity, lower VD, lower FD, and increased VDI. Enlarged FAZ area was correlated with shorter axial length and thinner central subfield macular thickness. Decreased FAZ circularity was correlated with a reduction in visual function. Decreased VD was correlated with thinner macular ganglion-cell inner plexiform layer. Increased VDI was correlated with higher fasting glucose level. We concluded that the effects of ocular and systemic factors in diabetics should be taken into consideration when assessing microvascular alterations via OCT-A.