Contrast sensitivity following focal laser photocoagulation in clinically significant macular oedema due to diabetic retinopathy

Association Between Contrast Sensitivity and Central Subfield Thickness in Center-Involving Diabetic Macular Edema

Purpose: To evaluate the association between contrast sensitivity (CS) and central subfield thickness (CST) in diabetic macular edema (DME). Methods: This prospectively recruited, cross-sectional study included eyes with DME evaluated from November 2018 to March 2021. CST was measured using spectral-domain optical coherence tomography on the same day as CS testing. Only eyes with center-involving DME (CST >305 µm for women; >320 µm for men) were included. CS was evaluated using the quantitative CS function (qCSF) test. Outcomes included visual acuity (VA) and the following qCSF metrics: area under the log CS function, contrast acuity (CA), and CS thresholds at 1 to 18 cycles per degree (cpd). Pearson correlation and mixed-effects regression analyses were performed. Results: The cohort included 52 eyes of 43 patients. Pearson correlation analysis showed a stronger association between CST and CS thresholds at 6 cpd (r = -0.422, P = 0.002) than CST and VA (r = 0.293, P = 0.035). Mixed-effects univariate and multivariate regression analyses showed significant associations between CST and CA (β = -0.001, P = .030), CS at 6 cpd (β = -0.002, P = .008), and CS at 12 cpd (β = -0.001, P = .049) but no significant associations between CST and VA. Among the visual function metrics, the effect size of CST was largest on CS at 6 cpd (βStandardized = -0.37, P = .008). Conclusions: In patients with DME, CS may be more strongly associated with CST than VA. Including CS as an adjunct visual function outcome measure in eyes with DME may prove clinically valuable.

Psychophysical Exams as Early Indicators of Diabetic Retinopathy

Retinopathy is a serious and common complication of diabetes that represents the leading cause of blindness, among people of working age, in developed countries. It is estimated that the number of people with diabetic retinopathy (DR) will increase from 126.6 million in 2011 to 191 million by 2030. The visual function that seems to be affected first in the course of DR is probably the contrast sensitivity; in addition, being mainly a macular function, the perception of colour is also compromised. Moreover, the duration of the disease, the levels of glycated haemoglobin (HbA_1c) and the presence of cystoid macular oedema are strongly associated with the impairment of fixation stability in patients with diabetes with clinically significant macular oedema, suggesting the possible diagnostic role of microperimetry. The test of contrast sensitivity and the microperimetry and the chromatic sensitivity tests have proved to be useful, safe, reproducible and inexpensive tools to diagnose the disease early.

Mesopic foveal contrast sensitivity is impaired in diabetic patients without retinopathy

BACKGROUND

Contrast sensitivity (CS) has been studied extensively to determine its effectiveness as a test for diagnosing early and advanced diabetic retinopathy. Various techniques have been adopted to measure CS, and most of them reported a significant difference between diabetic and normal eyes. Our purpose is to demonstrate differences in foveal CS between diabetic patients without retinopathy and healthy subjects under mesopic and photopic conditions, using a simple, rapid computerized test.

METHODS

Seventeen eyes of nine patients with type 2 diabetes without diabetic retinopathy were included. Fourteen eyes of seven non-diabetic patients served as controls. All the patients underwent a careful ophthalmologic examination, including ETDRS chart visual acuity, color photographs, and optical coherence tomography (OCT). Patients with any ocular disease were excluded. All eyes had a visual acuity of 20/25 or better, a normal eye examination and optical coherence tomography (OCT). Photopic and mesopic contrast sensitivity was tested using a computerized psychophysical static method involving four forced-choice procedures. The targets were Gabor patches with spatial frequencies of 3-12 cycles per degree (cpd). The mesopic testing was conducted in a completely darkened room; the monitor was covered with a neutral density filter, allowing luminance of only 0.9 cd/m(2).

RESULTS

The average age was similar: 59.1 ± 5.3 years in the diabetic group vs 61.4 ± 3.2 years in the control group. The average duration of diabetes was 16 years (range 6-26). The average visual acuity was 0.04 ± 0.01 logMAR and 0.01 ± 0.01 logMAR in the diabetic and control groups respectively. Photopic foveal CS was similar in both groups. Significantly lower CS was found in diabetic patients under mesopic conditions at a spatial frequency of 3 (p < 0.008). At higher spatial frequencies, the mesopic contrast sensitivity was very low in both groups and without a significant difference.

CONCLUSIONS

Mesopic foveal CS is impaired in diabetic patients despite good visual acuity, a normal fundus examination and normal OCT. Early central visual function impairment may occur in diabetic patients before the appearance of retinopathy.

Functional outcome of subthreshold versus threshold diode laser photocoagulation in diabetic macular oedema

AIMS

To compare the efficacy of subthreshold diode laser photocoagulation with conventional threshold diode laser in clinically significant macular oedema (CSME) in diabetics.

METHODS

Prospective randomised controlled trial. Thirty eyes of 20 patients with CSME having central macular thickness (CMT) >or=250 microm on optical coherence tomography (OCT) and best corrected Snellen visual acuity (BCVA) of 20/80 or better were randomly assigned to receive subthreshold diode laser (group A) or threshold laser (group B). The clinical course of BCVA, CMT on OCT, photo stress recovery time (PSRT), contrast sensitivity (CS) using Pelli Robson chart, and central visual field (10-2 VF, Humphrey Field Analyser II) were monitored regularly for 18 weeks after intervention.

RESULTS

Both groups showed significant (P=0.03) and comparable improvement in mean BCVA at 18 weeks visit. There were also significant and comparable reductions (P<0.01) in mean CMT at all visits compared with baseline in both groups. PSRT and CS (75+/-16 (mean+/-SD) and 0.72+/-0.3 in group A and 81+/-12 and 0.68+/-0.2 in group B pre-laser) were significantly better in group A at the final visit (66+/-17 and 1.04+/-0.3) as compared to group B (78+/-11 and 0.73+/-0.3). One patient in group B showed a paracentral scotoma on 10-2 VF after the laser, which persisted till the end of follow-up.

CONCLUSION

Subthreshold diode laser photocoagulation is as effective as conventional threshold laser in reducing or eliminating diabetic macular oedema (on OCT) and in improving BCVA. Recovery of macular function as assessed by CS and PSRT maybe better with subthreshold laser.

Diabetic macular edema: what is focal and what is diffuse?

PURPOSE

To review the available information on classification of diabetic macular edema (DME) as focal or diffuse.

DESIGN

Interpretive essay.

METHODS

Literature review and interpretation.

RESULTS

The terms focal diabetic macular edema and diffuse diabetic macular edema frequently are used without clear definitions. Published definitions often use different examination methods and often are inconsistent. Evaluating published information on the prevalence of focal and diffuse DME, the responses of focal and diffuse DME to treatments, and the importance of focal and diffuse DME in assessing prognosis is hindered because the terms are used inconsistently. A newer vocabulary may be more constructive, one that describes discrete components of the concepts such as extent and location of macular thickening, involvement of the center of the macula, quantity and pattern of lipid exudates, source of fluorescein leakage, and regional variation in macular thickening and that distinguishes these terms from the use of the term focal when describing one type of photocoagulation technique. Developing methods for assessing component variables that can be used in clinical practice and establishing reproducibility of the methods are important tasks.

CONCLUSIONS

Little evidence exists that characteristics of DME described by the terms focal and diffuse help to explain variation in visual acuity or response to treatment. It is unresolved whether a concept of focal and diffuse DME will prove clinically useful despite frequent use of the terms when describing management of DME. Further studies to address the issues are needed.

Assessment of central vision and macular structure in patients undergoing iodine-125 brachytherapy for ciliochoroidal melanoma

OBJECTIVES

To prospectively report standardized visual function and macular structural assessment in patients undergoing iodine-125 brachytherapy for choroidal and ciliary body melanoma.

MATERIALS AND METHODS

Patients were enrolled for pretreatment and annual posttreatment assessment. Evaluations included ophthalmic history; standardized refraction; visual acuity, contrast sensitivity, and color vision measurement; comprehensive ophthalmic examination; fundus photography; fluorescein angiography; optical coherence tomography; and ultrasonography. Radiation doses to the foveola and optic disc margin were calculated.

RESULTS

Forty-two patients were enrolled. Melanoma location included 3 in the ciliary body, 7 anterior, 11 equatorial, 13 posterior, and 8 macular tumors. Mean apical tumor height was 4.45 mm (range 1.79-9.83 mm) and mean longitudinal tumor diameter was 9.41 mm (range 4.52-4.73 mm). Pretreatment mean best-corrected Ferris-Bailey early treatment diabetic retinopathy study visual acuity was 50 (standard deviation +/- 15) letters (Snellen equivalent 20/32, range 20/15 to hand motions). The mean Pelli-Robson contrast threshold percentage was 4.1% (+/- 2.5%). The mean Hardy-Rand-Rittler color vision score was 13/14 (+/- 2.7). Mean distances from the posterior edge of the tumor to the foveola and the optic disc margin were 6.99 mm (+/- 6.22 mm) and 7.28 mm (+/- 5.98 mm), respectively. At the foveola, median total radiation dose was 36.2 Gy (+/-50.6 Gy) and median dose rate was 31.6 cGy/h (+/- 39.8 cGy/h). At the optic nerve, median total radiation dose was 42.8 Gy (+/- 30.8 Gy) and median dose rate was 36.2 cGy/h (+/- 21.4 cGy/h).

CONCLUSION

This prospective assessment of macular structure and function will provide more complete understanding of the ocular effects of radiation therapy for ocular melanoma.