Laxmi Gella

Measuring retinal sensitivity with the microperimeter in patients with diabetes.

Purpose: To evaluate the retinal sensitivity and fixation characteristics in participants with diabetes mellitus, using the microperimeter (MP-1) and to correlate the MP-1 values with the severity of diabetic retinopathy (DR). Methods: We performed complete ophthalmic examinations, including best-corrected visual acuity, slit-lamp examination, indirect ophthalmoscopy, and microperimetry (central 20° of macula) on 210 eyes of 160 participants. Participants included healthy individuals, individuals with diabetes but no retinopathy, and individuals with different stages of DR. Results: The mean age of participants was (mean ± SD) 49.83 ± 7.43 years for healthy individuals, 53.20 ± 5.7 years for participants with diabetes but no retinopathy, and 55.39 ± 7.81 years for participants with DR. Retinal sensitivity was significantly (P = 0.001) decreased with severity of DR. The mean foveal sensitivity (retinal sensitivity in the central 2°) was 16.68 ± 2.13 dB in healthy individuals, 14.73 ± 3.64 dB in participants with diabetes but no DR, and 11.60 ± 5.76 dB in participants with DR. There was significant loss of retinal sensitivity in participants with diabetes but no retinopathy when compared with healthy individuals. Participants with severe nonproliferative DR showed more significant loss of retinal sensitivity in the central 20° than those with other stages of DR. Conclusion: The MP-1 is a useful tool to quantify retinal sensitivity in DR. Using the MP-1, we can detect early loss of retinal sensitivity in patients with diabetes but no retinopathy. Patients with severe nonproliferative DR will have less retinal sensitivity than those with other stages of DR. Scotoma mapping using the MP-1 provides details of functional vision in patients with DR.

Prevalence of visual impairment and associated risk factors in subjects with type II diabetes mellitus: Sankara Nethralaya diabetic retinopathy epidemiology and molecular genetics study (SN-DREAMS, report 16)

Purpose: To report the prevalence of visual impairment (VI) and the associated risk factors in type II diabetic subjects. Materials and Methods: The study included type II diabetes mellitus subjects who were enrolled from a cross-sectional study. Participants underwent biochemical testing and comprehensive ocular examination including stereo fundus photography. The VI was defined based on the World Health Organization criteria. Results: The prevalence of VI was 4% in the cohort. The risk factors associated with the presence of VI included a female gender, age greater than 60 years, low socio-economic status, hypertension, microalbuminuria, macroalbuminuria, neuropathy, use of insulin and alcohol. Various ocular risk factors are nuclear sclerosis, subjects who have undergone cataract surgery, myopia and sight-threatening diabetic retinopathy (STDR). After adjusting for the factors using stepwise logistic regression analysis, hypertension, use of alcohol, post-cataract surgery and myopia were not risk factors. Stepwise logistic regression analysis indicated that VI was higher among subjects older than 60 years (odds ratio (OR): 4.95 [2.67-9.15]) and those who belonged to a low socio-economic status (OR: 2.91 [1.24-6.85]). The systemic risk factors for VI included microalbuminuria (OR: 2.91 [1.59-5.33]), macroalbuminuria (OR: 4.65 [1.57-13.77]) and presence of neuropathy (OR: 1.97 [1.09-3.59]) among subjects. Subjects with nuclear sclerosis (OR: 36.82 [11.12-112.36]) and presence of STDR (OR: 4.17 [1.54-11.29]) were at a higher risk of VI. Cataract was the most common cause of VI in the cohort. Conclusion: Visual impairment, among type II diabetic subjects (4%), is a major public health problem that needs to be addressed. Cataract is the most common reversible cause of vision impairment in this population.

Local Anesthetic Agents for Vitreoretinal Surgery: No Advantage to Mixing Solutions

PURPOSE To compare the efficacy of lidocaine, bupivacaine, and a mixture of both in patients undergoing peribulbar anesthesia for vitreoretinal surgery. DESIGN Cross-sectional study. PARTICIPANTS Ninety patients. METHODS Patients who underwent vitreoretinal surgery were randomized into 3 groups based on the peribulbar injection they received: lidocaine, bupivacaine, or a combination of lidocaine and bupivacaine. MAIN OUTCOME MEASURES Time of onset of analgesia, akinesia, and intraoperative pain, if any, was noted. The efficacy of the block was graded from 0 to 5 depending on the adequacy of anesthesia and akinesia and the need for local supplementation. RESULTS Mean times of onset (± standard deviation) of sensory blockade for the lidocaine, bupivacaine, and combination groups were 2.14±0.18, 2.19±0.13, and 2.17±0.11 minutes, respectively (P = 0.103). Mean times of onset (± standard deviation) of motor blockade for the lidocaine, bupivacaine, and combination groups were 3.04±1.81, 4.04±2.68, and 3.38±2.48 minutes, respectively (P = 0.255). Mean time of onset of intraoperative pain for the bupivacaine group, 149.33±46.33 minutes, was prolonged significantly compared with that of the combination group, 115.83±34.49 minutes, and that of the lidocaine group, 94.17±49.86 minutes (P < 0.001). Adequate anesthesia and akinesia (grade 5) were achieved in 56.7% of the patients in the bupivacaine group compared with 23.3% in the lidocaine group and 30% in the combination group (P = 0.049). CONCLUSIONS In peribulbar anesthesia, 0.5% bupivacaine solution provides better quality of anesthesia than does combination 2% lidocaine and 0.5% bupivacaine in patients undergoing vitreoretinal surgery.

Morphological and functional changes in spectral domain optical coherence tomography and microperimetry in macular microhole variants: Spectral domain optical coherence tomography and microperimetry correlation

Purpose: To evaluate the relationship between the morphology and retinal function of macular microhole (MMH) variants. Materials and Methods: We evaluated 12 eyes of 11 patients with defects in the IS/OS junction of photoreceptor layer with SD-OCT. All patients underwent comprehensive ophthalmic examination including spectral domain optical coherence tomography (SD-OCT) and microperimetry. Results: The mean logMAR visual acuity in the affected eye was 0.15 ± 0.17 (range 0.00–0.5). Mean horizontal diameter of the MMH was 163 ± 99 μm; the mean retinal sensitivity in the area corresponding to the MMH was 13.79 ± 4.6 dB. Negative correlation was found between the MMH diameter and the retinal sensitivity (r = -0.65, p = 0.02). Three morphological patterns of MMH variants were recognized on SD-OCT, which did not differ in retinal sensitivities. Conclusion: We described and classified the MMH variants and made an assessment on the physiological functions using microperimeter.

Evaluation of in vivo human retinal morphology and function in myopes.

Purpose: To compare the retinal sensitivity, using Microperimeter and the morphological changes in retinal layers, using Spectral Domain Optical Coherence Tomography (SD-OCT), between myopes and age-matched emmetropes. Methods: Twenty-nine myopic eyes and 29 emmetropic eyes were enrolled in this prospective case control study. All subjects underwent subjective refraction as part of the ophthalmic examination and in addition, SDOCT and Microperimetry were performed. Based on the reflectivity on the OCT cross sections, the thickness of the retinal layers was measured 2.5 mm on either side of the fovea. Results: The mean retinal sensitivity was significantly (p = 0.001) reduced in myopes (17.31 ± 1.80 dB; mean ± SD) compared to that of emmetropes (18.61 ± 1.08 dB). SD-OCT did not show any significant difference in the photoreceptor layer and foveal thickness between myopes and emmetropes. The retinal pigment epithelium thickness was significantly reduced in myopes (35.03 ± 4.21 µm) compared to emmetropes (37.74 ± 4.30 µm) (p = 0.019). We found a significant positive correlation between refractive error and mean retinal sensitivity (r = 0.725, p = <0.001). Conclusion: The retinal sensitivity was significantly reduced in myopes in spite of normal retinal morphology indicating that functional changes may precede structural changes.

Retinal sensitivity changes associated with diabetic neuropathy in the absence of diabetic retinopathy

Purpose To explore any relationship between the markers of early retinal neuronal damage and peripheral diabetic neuropathy in subjects with no diabetic retinopathy (DR). Methods A cross-sectional study in which type 2 diabetic subjects (n=743) without DR were studied. Visual functions including visual acuity, contrast sensitivity, colour vision, retinal sensitivity using microperimeter and retinal thicknesses by spectral domain optical coherence tomography were measured. Vibration perception thresholds of greater than or equal to 20 µV, measured by sensitometer using a biothesiometer probe, were defined as having peripheral diabetic neuropathy. Statistical analyses were performed using independent t-test, multivariate logistic regression and Pearsons correlation. Results Of 743 subjects who had no DR, 24.9% had diabetic neuropathy. Independent comparisons among subjects who had diabetic neuropathy compared with those who did not showed statistically significant retinal nerve fibre layer thinning (p=0.01), reduced contrast sensitivity (p=0.0001), reduced retinal sensitivity (p=0.03), impaired colour vision (p=0.04) and reduced visual acuity (p=0.0001). Multivariate analysis showed significant association between the mean retinal sensitivity (measured using a microperimeter) and diabetic neuropathy (adjusted OR (95% CI): 0.76 (0.60 to 0.95), p=0.01). Conclusions Significant association of neuroretinal dysfunction with the presence of diabetic neuropathy was noted among subjects with no DR.

Spectral domain optical coherence tomography characteristics in diabetic retinopathy

Purpose: To report the appearance of diabetic retinopathy lesions using spectral domain optical coherence tomography (SD-OCT). Materials and Methods: A total of 287 eyes of 199 subjects were included. All the subjects underwent complete ophthalmic examination including SD-OCT. Results: The appearance of various lesions of diabetic retinopathy and the retinal layers involved were reported. In subjects with macular edema the prevalence of incomplete PVD was 55.6%. Conclusion: SD-OCT brings new insights into the morphological changes of the retina in diabetic retinopathy.

Retinal sensitivity in healthy Indians using microperimeter.

Aims: To establish the retinal sensitivity values in healthy Indians using microperimeter. Materials and Methods: In this prospective study, 144 healthy volunteers were included. All the participants underwent a comprehensive ophthalmic examination including contrast sensitivity. Microperimetry was performed in the central 20° of the macula using 76 stimulus points to assess the retinal sensitivity, and the fixation characteristics in the study population were assessed. Results: The mean age of the study sample was 43.08 ± 10.85 years (range: 25-69). Mean retinal sensitivity was 18.26 ± 0.99 dB. Males had significantly increased retinal sensitivity (18.34 vs. 18.17 dB, P = 0.03). The linear regression analysis revealed a 0.04 dB per year age-related decline in mean retinal sensitivity. Contrast sensitivity was significantly correlated with the mean retinal sensitivity (r = 0.432, P < 0.001). Fixation stability in the central 2° and 4° were 69% and 89%, respectively. Conclusion: Microperimeter is an ideal tool to assess the retinal sensitivity and the fixation behavior. These normative values could help in drawing a meaningful conclusion in various retinal pathologies.

Spectral domain optical coherence tomography and microperimetry in foveal hypoplasia

A case of foveal hypoplasia associated with ocular albinism with anatomic and functional changes by various techniques using spectral domain optical coherence tomography (SD-OCT), microperimeter and confocal scanning laser ophthalmoscope is described. This case highlights the importance of microperimeter in detecting the functional abnormalities of vision and SD-OCT in identifying the retinal laminar abnormalities in foveal hypoplasia.

Incidence and Progression of Diabetic Retinopathy in Urban India: Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SN-DREAMS II), Report 1

ABSTRACT Purpose: To evaluate the 4-year incidence and progression of and risk factors for diabetic retinopathy (DR) in an Indian population. Methods: From a cross-sectional study of 1425 subjects with diabetes, 911 (63.9%) returned for 4-year follow-up. After excluding 21 with ungradable retinal images, data from 890 subjects were analyzed. Participants underwent examinations based on a standard protocol, which included grading of retinal photographs. Results: The incidences of DR, diabetic macular edema (DME), and sight-threatening diabetic retinopathy (STDR) were 9.2%, 2.6%, and 5.0%, respectively. In subjects with DR at baseline, the incidence of DME and STDR had increased (11.5% and 22.7%, respectively). 1-step and 2-step progressions of DR were seen in 30.2% and 12.6% of participants, respectively, and 1-step and 2-step regressions were seen in 12.0% and 1.8%, respectively. Incident DR, DME, and STDR were associated with higher systolic blood pressure (odds ratio, OR, 1.21, 2.11 and 1.72, respectively, for every 10 mmHg increase). Incident DR and DME were associated with increasing duration of diabetes (OR 2.29 and 4.77, respectively, for every 10-year increase) and presence of anemia (OR 1.96 and 10.14, respectively). Incident DR was also associated with higher hemoglobin A1c (OR 1.16 for every 1% increase). Variables associated with 1-step progression were every 10 mg/dL increase in serum total cholesterol (OR 15.65) as a risk factor, and 10 mg/dL increase in serum triglyceride (OR 0.52) as a protective factor. Conclusions: The incidences of STDR and DME were higher in people with pre-existing DR than in those without DR at baseline.