EFFECT OF LASER PHOTOCOAGULATION ON CONTRAST SENSITIVITY , VISUAL ACUITY AND COLOUR VISION IN PATIENTS OF DIABETIC MACULAR EDEMA

Nirmala Jyothi Pamu 1 , V. Rajeswara Rao 2 and Chandana Priyanka S 3 . 1. Associate Professor, Department of Ophthalmology, AMC, Vishakhapatnam. Andhra Pradesh, INDIA. 2. Professor, Department of Ophthalmology, AMC, Vishakhapatnam Andhra Pradesh, INDIA. 3. Postgraduate, Department of Ophthalmology, AMC, Vishakhapatnam Andhra Pradesh, INDIA. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 11 December 2018 Final Accepted: 13 January 2019 Published: February 2019 Aim: To assess the effects of laser photocoagulation on contrast sensitivity, visual acuity and colour vision in patients of diabetic macular edema. Methods: It is a hospital-based prospective analytical study conducted on 30 eyes of type 1 and types 2 of diabetes mellitus patients with NPDR and non-centre involved diabetic macular edema of more than 18 years of age of both the sexes for a one-year duration. Results: The majority belonged to the age group of 51-60 yrs. Males represented 60% with a peak incidence at 51-60 years and females represented 40 %. BCVA was stabilized in 63%, improved by 26% and decreased by 10%. In this study, the mean baseline contrast sensitivity was 0.49 log CS which improved significantly to o.60 log CS and 0.64 logs CS at 3 and 6 months respectively.No change in colour vision was noted at 6 months follow up Conclusion: Timely treatment of Diabetic macular edema with laser retinal photocoagulation prevents further dysfunction and salvages involved retina causing statistically significant improvement in vision and quality of life.

802 sensitivity are present I the diabetics even with normal visual acuity recorded by the Snellen's chart. Mechanism of loss of contrast sensitivity in DME(diabetic macular edema) is not known but may be due to accumulation of abnormal fluids in the macula 5,9 and enlargement of foveal avascular zone 10 macular edema, is the thickening of retina in the region of macula caused by break down of inner retinal barrier at the papillary endothelial level. The prevalence of macular edema is more in non-insulin dependent diabetes mellitus patients requiring insulin for glycemic control 6 . The diabetic macular edema is broadly divided into focal macular edema and diffuse macular edema.
Optical coherence tomography (OCT) provides insight into underlying retinal layers and yields usual information. According to OCT, there are 5 distinct patterns of macular edema. (11) 1. Sponge-like retinal thickening 2. Cystoids macular edema 3. Subserous retinal detachment 4. Focal tractional retinal detachment 5. Taut posterior hyaloid membrane According to current ETDRS guild lines, focal or grid laser photocoagulation remains the gold standard for diabetic macular edema without central involvement. EDTRS gave the treatment strategies' for diabetic macular edema and is followed worldwide. The central macular thickness was found to be the most predictive factor for visual prognosis. According to ETDRS Diabetic macular edema is can be graded into CSME which is a good indicator of laser photocoagulation. It includes any of the following findings:-1. Retinal thickening at or within 500 microns of the centre of the macula 2. Hard exudates at or within 500 microns of the centre of the macula with the adjacent retinal thickening 3. An area or areas of retinal thickening at least disk area in size part of which is within one disc diameter of the centre of the macula OCT definition retinal thickening due to DME > 2 SD beyond the normal value outside the central subfield but < mean +SD in spectral domain OCT within the central subfield. All through the central macular thickness was found to be most predictive factor additional factors like angiographic leakage at the inner subfields' also contribute to loss of visual acuity(VA).
In this study, we compared the changes in the VA, macular thickness and volume parameters measured with OCT in patients with non-central-involved macular edema (Non-CME) treated with focal laser photocoagulation.

Aims and Objectives:-
To evaluate visual acuity, colour vision, and contrast sensitivity in patients with non-centre involved diabetic macular edema following laser photocoagulation.

Materials and Methods:-
It is a hospital-based prospective analytical study conducted on 30 eyes of type 1 and type 2 of diabetes mellitus patients with NPDR and non-centre involved diabetic macular edema of more than 18 years of age of both the sexes. Definite retinal thickening due to diabetic macular edema within 3000 microns of the centre of macula but involving the central subfield.
According to DR CR. NET approved spectral domain OCT machine -ZEISS, cirrus < 290 in women and <305 in men. Patients with media not clear, active proliferative diabetic retinopathy and those who had undergone prior photocoagulation and patients with a history of recent ocular surgery, a patient with other disorders of retina / optic nerve In which contrast sensitivity is already compromised and best corrected visual acuity less than 3/60 were excluded from the study Visual acuity was recorded with the help of self-illuminated Snellen acuity chart placed at a distance of 6 meters and best corrected visual acuity (BCVA) taken after giving appropriate spherical and cylindrical lenses. These BCVA measurements are converted into log mar units for statistical analysis.

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Then the contrast sensitivity test was conducted by using Pelli Robison chart, which is a wall mount chart kept at a distance of 1 meter which is illuminated by room light. A contrast sensitivity test was conducted before the dilatation of the pupils.
Colour vision was recorded by using FARNS WORTH D12 test then detailed anterior segment evaluation was done by slit lamp examination and ocular comorbidities were ruled out.
The fundus evaluation was done with the help of direct and indirect ophthalmoscope. Then OCT was performed through dilated pupils using cirrus ziess HD-OCT macular scans After fundus fluorescein angiography to detect the areas of the leak, laser photocoagulation was done by a single retina specialist in the retina clinic after obtaining written consent from the patient.

Focal direct laser treatment:-
Directly treat all leaking microaneurysms in areas of retinal thickening between 500 and 3000 µm from the centre of the macula (but not within 500 µm of the disc). -Spot size -50 µm-Burn duration -0.05 to 0.1 sec -power 50-150mwatt.
Modified grid laser: focal treatment for leaking microaneurysms and grid treatment to the areas of retinal thickening with diffuse leakage located more than 500 microns from the centre of the macula and 500 microns from the temporal margin of the optic disc. Spot size should be100 to 200 microns, duration of laser 0.10 second power-100-150mWatt.

Results:-
The age groups of the patients included under the study ranged from 40-75 years with a mean age of 58.48± 7.8years.  In the present study age group of the patients included under the study ranged from 41-75 years. The majority belonged to the age group of 51-60 yrs. This is in concordance with Seo and Park et al. 12  In our study, BCVA was stabilized in 63%, improved by 26% and decreased by 10%.In a study conducted by Talwar Det al 14 on contrast sensitivity following laser photocoagulation in CSME, the mean pre-laser contrast sensitivity score was 121.3±83.6 which increased significantly to a mean of 151.6±80.5 which concluded that focal argon laser photocoagulation in CSME helps in improving the contrast sensitivity and stabilizes the visual acuity. In In the present study Tritan defect was seen in 20 eyes (66%), deutan defect seen in 6 eyes(20%) and colour vision was normal in 4 eyes(6%). No change in colour vision was noted at 6 months follow up. Sadiqulla et al 16 reported a red-green loss pattern prevailing then total colour blindness, Shin et al 17 reported a blue-yellow loss pattern, the same reported by Patzetal 18 andMa´ar et al 19 .
Limitations of the study are Limited duration of follow up, Long term complications of laser photocoagulation were unknown. Small sample size

Conclusion:-
Timely treatment of Diabetic macular oedema with laser retinal photocoagulation prevents further dysfunction and salvages involved retina causing statistically significant improvement in vision and quality of life.