Effect of diabetic retinopathy and diabetes on the intraocular straylight in pseudophakic eyes

Evaluation of corneal backward light scattering in type 2 diabetes mellitus

AIM

To compare the corneal backward light scattering values in type 2 diabetes mellitus (DM) patients with those of age and sex-matched healthy controls.

METHODS

The study included 30 patients (30 eyes) with type 2 DM and 30 control subjects (30 eyes). Duration of diabetes, most recent hemoglobin A1c levels, along with the status of diabetic retinopathy, and existing medical treatment of all subjects were recorded. All subjects underwent a complete ophthalmologic examination. In addition, backward light scattering (densitometry) was measured to assess changes in corneal transparency using tomography (Pentacam HR).

RESULTS

The type 2 DM patients included 12 males and 18 females and control subjects included 16 males and 14 females. The age was 50.40±7.80y (range: 40-68y) of the diabetic group and 49.30±9.50y (rang: 40-73y) of control group. The diabetic group demonstrated significantly higher mean densitometry values of the anterior (6-10 mm) zone (P=0.047), the total anterior layer (P=0.036) and the total cornea (P=0.043) than control group. The corneal densitometry of the diabetic eyes demonstrated no significant correlation with hemoglobin A1c levels and DM duration.

CONCLUSION

Diabetic group has higher densitometry in anterior corneal (6-10 mm) zone, total anterior cornea, and total cornea and with no correlation with hemoglobin A1c levels and DM duration.

Evaluation of corneal densitometry changes in patients with lichen planus

PURPOSE

To investigate the corneal topography and densitometry changes in patients with lichen planus (LP).

METHODS

Anterior segment parameters and corneal densitometry of patients with LP and age- and gender-matched individuals with healthy eyes were evaluated using Scheimpflug corneal topography. A 12 mm corneal area was divided into 4 annular zones and 3 regions-in-depth anterior, central and posterior-for densitometry evaluation.

RESULTS

The study included 45 patients with LP and 50 individuals with healthy eyes. The two groups were similar in age and gender, and they showed no significant differences in anterior segment corneal topography parameters. Schirmer's I test results were significantly lower in the patients with LP than in the control group (P ˂ .001). The total corneal densitometry was higher in patients with LP than in the control group (P = .030). The anterior, central and posterior corneal densitometry in the 0-2 mm and 2-6 mm annular zones was higher in the LP group than in the control group. Correlation analysis between disease duration and corneal densitometry values showed a strong positive correlation in the anterior segment and a moderate positive correlation in the central and posterior segments (r = 0.632, P ˂ .001; r = 0.572, P ˂ .001; and r = 0.562, P ˂ .001, respectively).

CONCLUSIONS

Corneal densitometry values were higher in patients with LP than in individuals with healthy eyes, even if the patients had a clinically transparent cornea. More studies are needed to evaluate the changes that may occur in corneal transparency in patients with LP and other autoimmune dermatologic diseases that may affect the eye.

Iterative-Trained Semi-Blind Deconvolution Algorithm to Compensate Straylight in Retinal Images

The optical quality of an image depends on both the optical properties of the imaging system and the physical properties of the medium in which the light travels from the object to the final imaging sensor. The analysis of the point spread function of the optical system is an objective way to quantify the image degradation. In retinal imaging, the presence of corneal or cristalline lens opacifications spread the light at wide angular distributions. If the mathematical operator that degrades the image is known, the image can be restored through deconvolution methods. In the particular case of retinal imaging, this operator may be unknown (or partially) due to the presence of cataracts, corneal edema, or vitreous opacification. In those cases, blind deconvolution theory provides useful results to restore important spatial information of the image. In this work, a new semi-blind deconvolution method has been developed by training an iterative process with the Glare Spread Function kernel based on the Richardson-Lucy deconvolution algorithm to compensate a veiling glare effect in retinal images due to intraocular straylight. The method was first tested with simulated retinal images generated from a straylight eye model and applied to a real retinal image dataset composed of healthy subjects and patients with glaucoma and diabetic retinopathy. Results showed the capacity of the algorithm to detect and compensate the veiling glare degradation and improving the image sharpness up to 1000% in the case of healthy subjects and up to 700% in the pathological retinal images. This image quality improvement allows performing image segmentation processing with restored hidden spatial information after deconvolution.

Optical Quality and Intraocular Scattering in the Diabetic Eye without Diabetic Retinopathy

SIGNIFICANCE

This study suggests that despite having comparable best-corrected visual acuity and normal fundus appearance, objective measurements of optical quality showed that patients with diabetes but without overt retinopathy may have impaired visual function. Screening using the Optical Quality Analysis System might help identify those patients.

PURPOSE

Visual impairments are common in diabetes, but the status of the problem is unclear before the development of diabetic retinopathy. The aim of this pilot study was to investigate the optical quality and intraocular scattering in the diabetic eye without diabetic retinopathy.

METHODS

Twenty-seven patients with diabetes without diabetic retinopathy were enrolled. Twenty-seven age- and sex-matched healthy volunteers served as a control group. Optical quality parameters included modulation transfer function cutoff frequency, Strehl (two-dimensional) ratio, and Optical Quality Analysis System values at 100, 20, and 9 contrast levels. The objective scatter index was assessed using the Optical Quality Analysis System. Correlations were analyzed between the modulation transfer function cutoff, Strehl ratio, objective scatter index, and Optical Quality Analysis System value, and the age of the patient and the duration of diabetes mellitus.

RESULTS

The diabetic group exhibited lower modulation transfer function cutoff, Strehl ratio, and Optical Quality Analysis System values at 100, 20, and 9% contrast levels and higher objective scatter index than did the controls (all, P < .01). There were no associations between the optical quality parameters and age or the duration of diabetes mellitus in the diabetic participants (all, P > .05). Moderate associations were found between all parameters obtained from the Optical Quality Analysis System and age in the control group (all, P < .01).

CONCLUSIONS

This pilot study suggests that optical quality was reduced, and intraocular scattering increased in the diabetic eye without diabetic retinopathy compared with controls.

Objective Evaluation of Corneal and Lens Clarity in Children With Type 1 Diabetes Mellitus

PURPOSE

To investigate whether abnormal glucose metabolism and duration of diabetes mellitus (DM) affected the corneal and lens clarity in children with well-controlled type 1 DM and to compare the results obtained with those in healthy children.

DESIGN

Cross-sectional prospective study.

METHODS

This multicenter study enrolled 56 patients with DM and 51 control subjects. The duration of DM and the glycosylated hemoglobin (HbA1c) levels of the patients in the DM group were recorded. The Pentacam HR imaging system was used for corneal densitometry (12-mm corneal diameter) measurements. Furthermore, the lens densitometry and lens thickness (LT) measurements were performed after dilation of the pupils, using the same Pentacam HR device.

RESULTS

The corneal densitometry values were similar in all concentric zones and layers in both groups (P > .05, for all). The mean values of the average and maximum lens densitometry measurements of the 2 groups, as well as the mean LT values, were statistically significantly different (P = .021, P = .011, and P < .001, respectively). There were statistically significant correlations between the lens densitometry values and the duration of DM (P < .05, for all). Conversely, no statistically significant relationship was found between the lens densitometry values and HbA1c levels (r = 0.743; P = .084).

CONCLUSIONS

The children with type 1 DM had decreased lens clarity and increased LT, even in cases of well-controlled DM, without DR. It is reasonable to think that these changes might have been caused by the type 1 DM.

The grey fovea sign of macular oedema or subfoveal fluid on non-stereoscopic fundus photographs

PURPOSE

To describe the grey fovea sign of fovea-involving macular oedema or subretinal fluid accumulation in red-free fundus photography.

METHODS

A test set of 91 digital fundus photographs of good quality from 100 consecutive eyes in 72 patients with diabetic retinopathy or central serous chorioretinopathy was composed by one of the investigators and evaluated by four masked observers. The photographs were graded as to whether a normal dark fovea was present or absent. The reference method was foveal thickness measurement using optical coherence tomography (OCT).

RESULTS

Eyes graded as having a grey fovea on fundus photographs (n = 67) had a median foveal thickness of 279 μm (interquartile range 130 μm), whereas eyes graded as having a normal dark fovea (n = 24) had a median foveal thickness of 238 μm (interquartile range 44.5 μm, p = 0.025).

CONCLUSION

The absence of a dark fovea on red-free greyscale fundus photographs is a sign of foveal thickening or detachment that can be reliably recognized by graders when using OCT as the reference diagnostic method. Awareness of the grey fovea sign may facilitate fundus photographic screening for maculopathy because its absence is a reliable sign that no foveal oedema or detachment is present. Its presence may indicate that such conditions are present, but it can also be induced by various other conditions, for which reason it should prompt further investigations by OCT.