Dr. Rajesh Ramanjulu, R14072, Dr. Pradeep Sagar, Dr. Mishra Divyansh Kailashcandra, Dr. Mahesh Shanmugam P
Purpose: To evaluate the effect of circular polarizer filter on visual function in patients with lesions of optic nerve head and macula.
Methods: 300 patients with a minimum BCVA of 6/60 due to various macular and optic nerve pathologies including optic atrophy, macular dystrophies were included in the study. Circular polarizer filter was used over the best refractive correction to assess its impact on the visual function in different lighting conditions.
Results: Use of circular polarizer improved the visual function in more than 75% of patients. Degree of improvement varied in different lighting condition and maximum improvement was noted with yellow light.
Conclusion: Circular polarizer filters can improve visual function in patients with optic nerve and macular pathologies beyond their BCVA.
Introduction:
Visual impairment at any age, whether partial or total has a great negative impact on development, education, professional and daily activity. According to the WHO, Low vision is defined as V/A less than 6/18 in the better eye. Most individuals with V/A of 6/18 can perform in par with the normal peers. The problem lies with individuals having V/A ≤ 6/24, who need to be recognized, assessed and guided to lead near normal life. With the available resources LVA is limited in applicability due to various factors (bulky, limited field of view etc). We hereby test the role of circular polarizer filters in enhancing the V/A in such patients.
Rationale:
Polarizer filters help in betterment of V/A by eliminating the stray light rays and thereby averting glare.
Aims of the study:
To test the role of circular polarizer in patients with low vision.
Materials and Methods:
300 patients with various macular pathologies, including AMD (Disciform scar) –43 patients (86 eyes) , PFT – 13 patients (26 eyes), diabetic associated ischaemic macula – 52 patients (102 eyes), Retinal vein occlusion associated ischaemic fovea – 11 patients (22 eyes), Optic disc pallor of unknown etiology – 6 patients (12 eyes), NAION – 10 patients (20 eyes), CNS associated 9 patients (18 eyes), Local lesion of ONH 3 patients (6 eyes), Diabetic papillopathy – 4 patients (8 eyes) with a minimum V/A of more than 6/60 were included in the study.
This was a non-randomised, single blinded prospective study on patients of various macular and ONH pathologies attending the retina clinic. The BCVA was tested using the standard methods. Over and top of the BCVA a circular polarizer ( Hoya Inc, Japan ) was placed in front of the eye and rotated to get the best V/A. Both the distance and near V/A were tested under standard lighting condition. Various light sources and colors were used to determine the best suited for our patients.
Results were tabulated and statistical analysis was done using the SPSS software. For inter-group analysis student’s “t” test was applied.
Results:
The pretest mean V/A of the patients was 0.43 LogMAR (20/50). The Median was 0.50 LogMAR (20/63) and Mode was 0.63 LogMAR (20/80). The post test results mean V/A of the patients was 0.17 LogMAR (20/32), Median of 0.1 LogMAR (20/25) and mode was 0.1 (20/25).
The “p” value was > 0.0001, which is very significant.Discussion:
Visual acuity may be affected due to various macular and optic nerve pathologies as enumerated earlier. Most of the patients with these diseases have irreversible blindness. The present rehabilitation techniques are limited to Low visual aids which can improve the V/A to a limited extent with all its drawbacks. Hereby we tested a novel technique of using the circular polarizer filter under various lights of different sources.
The comparison test revealed a significant improvement in V/A over the BCVA upon applying the polarizer filter. The probable mechanism of action can be:
- Decreasing or eliminating the stray lights and thereby decreasing the glare component of low distance focused light.
- The polarized light stimulates the residual nerve fibres in the damaged retina in appropriate manner and thereby increasing the V/A beyond the BCVA using the standard methods.
The patients were tested under lights of various sources such as tungsten,
metal Halide, LED bulbs and CFL lamps. Patients were asked to undergo the same tests under morning sunlight. As expected all the patients did much better in reflected sunlight. Next best was the conventional tungsten bulb emitted yellow light. The patients did worst in the LED lights. The significance have to be further tested.
Conclusion:
Polarizer filter aided patients with various macular and ONH pathologies to see much better than their respective BCVA’s. it is completely safe and reversible as it’s an add on filter.
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