Protection Against Photic Damage in Retinitis Pigmentosa

Lux study: Contribution of a three-dimensional, high dynamic range, ultra-high-definition heads-up visualization system to a significant delivered light intensity decrease during different types of ocular surgeries

OBJECTIVE

To explore the hypothesis that using a large, three-dimensional (3D), ultra-high-definition (4K), heads-up display (HUD) system in a real-life setting may be associated with a significant reduction in light intensity (LI) delivered during various types of eye surgery.

METHODS

Single center, post-learning curve observational study of 142 independent consecutive cases: 73 cataracts and 69 vitrectomies (VR). For each group, the only variable setting was the LI. The LI delivered by each source was calibrated in lumens (lm).

RESULTS

In the VR group, the delivered LI dramatically decreased from the 80% reference to 27.8%±13.2% (P<0.0001) (4.3 to 1.5lm). Among these surgeries, 91.3% needed 40% or less LI (2.3lm). The corneal transparency and quality of pupil dilation showed some correlation with the results. In the cataract group, the difference was even more spectacular, from 80% to 15%±11.3% (P<0.0001) (2.5 to 0.3lm). Among these surgeries, 80.8% required less than 20% LI (0.5lm). The surgical time, LI variations and type of cataract seemed to influence the results, down to 9.6%±5.4% (P<0.0001) (0.22lm) for nuclear cataracts, which represented 63% of the cataract sample.

CONCLUSION

The digital signal amplification with this HUD system allows comfortable posterior as well as anterior segment surgery despite the decrease in incident light, suggesting an unprecedented reduction in the risk of phototoxicity compared to conventional systems as well as a likely improvement in patient comfort.

Transdifferentiation and survival of neural retina cells in relation to illumination

Cultures of chicken embryo neural retina cells were exposed to light of different intensities and colours, in order to identify the wavelengths that promote cell degeneration and transdifferentiation into pigment epithelium. Blue and green light caused cell death; blue, green and yellow light enhanced transdifferentiation; red light had no effect. The relevance of these findings to retinal degeneration in man and the possible mediation of rhodopsin, riboflavin and other chromophores are discussed.

Retinitis pigmentosa: visual function and multidisciplinary management

Retinitis pigmentosa (RP) is a leading cause of blindness and visual disability in younger people. Optometrists have a major role in detecting RP and in reducing the visual disability associated with RP. This review summarises the literature relating to visual function in people with RP, with particular attention given to night-blindness, visual acuity decrease and visual field contraction. The range of low vision aids available for people with RP is reviewed and suggestions given on aids that have been found to be most successful. Most importantly, this review overviews the range of services available to people with RP and emphasises how optometrists need to work with a network of professionals to ensure the best possible visual outcomes for people with RP. Particular mention is made of current findings relating to orientation and mobility training, driving, sensory substitution and adaptive technology. The modern optometrist needs to be aware of the multiple needs of people with RP and have the ability to link them with the professionals best able to help them.

Operating microscope-induced retinal phototoxicity: pathophysiology, clinical manifestations and prevention

Retinal light damage is a poorly understood phenomenon, due to its multifactorial etiology and relatively infrequent recognition. It has been increasingly identified following ocular surgery involving the intense light of the operating microscope. The authors describe the clinical entity, review salient features of its pathophysiology and provide guidelines for prevention of retinal phototoxicity.

Retinal degeneration in the mouse induced transplacentally by N-methyl-N-nitrosourea: effects of constant illumination or total darkness

The DNA alkylating agent, N-methyl-N-nitrosourea (MNU), when administered prenatally (on day 16 of gestation) provokes a progressive retinal degeneration in CD-1 albino mice reared in standard fluorescent lighting conditions (12 L: 12 D). This degeneration begins at about 4 weeks postnatally and worsens with age. To determine whether light was essential to the development of this lesion, animals in the present study were maintained in either constant light or constant darkness. Systematic measurement of the inner and outer segment lengths, the number of rows of photoreceptor cells and the thicknesses of the outer nuclear layer and whole retina were made to quantify degenerative changes in animals at 2-, 4-, 6-, 8-, 12-, and 16 weeks of age. The constant light caused a drastic reduction in thickness of the retinas of MNU-treated and control mice. The MNU-exposed animals reared in the dark did not demonstrate this reduction in retinal thickness, at least up to 16 weeks of age. Rather, measurements from this group were much like those for dark-reared control mice. The results of the present study suggest that the retinopathy induced by this dose of MNU may require secondary insults such as light, to amplify the lesions induced in utero by the drug.