Pressure dependent direct transtissue transmission of eyewall, sclera and vitreous body in the range of 350-1050nm

Determination of Correlated Color Temperature in Ex Vivo Porcine Eyes during Intraocular Illumination

(1) Background: In ophthalmic surgery, white light is mostly applied to illuminate the intraocular space, and ophthalmologists are comfortable working with it. Diaphanoscopic illumination changes the spectral composition of light, resulting in a change in the correlated color temperature (CCT) of the intraocular illumination. This color change makes it difficult for surgeons to recognize the structures in the eye. CCT during intraocular illumination has not yet been measured before, and it is the aim of this study to perform such measurement. (2) Methods: CCT was measured inside ex vivo porcine eyes during diaphanoscopic illumination and endoillumination using a current ophthalmic illumination system with a detection fiber inside the eye. By applying pressure on the eye with a diaphanoscopic fiber, the dependency of CCT on pressure was examined. (3) Results: The intraocular CCT values during endoillumination were 3923 K and 5407 K for the halogen and xenon lamps, respectively. During diaphanoscopic illumination, a strong unwanted red shift was observed, resulting in 2199 K and 2675 K for the xenon and the halogen lamps, respectively. Regarding different applied pressures, the CCT did not differ considerably. (4) Conclusions: This red shift should be compensated for in the development of new illumination systems since surgeons are used to white light illumination, which also simplifies the identification of retinal structures.

Determination of the intraocular irradiance and potential retinal hazards at various positions in the eye during transscleral equatorial illumination for different applied pressures

PURPOSE

With diaphanoscopic illumination of the eye, the intensity of light entering its interior depends on the transmission properties of the eyewall. Light that passes through the eyewall can cause damage to the retina. Therefore, in this study, the intraocular irradiances are determined at different positions on the retina, directly behind the illuminated eyewall, the opposite eyewall and near the macula of ex-vivo porcine eyes. These irradiances are examined for their dependence on the pressure applied on the eyewall with the illuminating fiber and for the influence of the pigmentation of the eye.

METHODS

In total 221 ex-vivo porcine eyes were investigated. For transscleral illumination an illumination fiber with a diffusing adapter cap is pressed against the equatorial eyewall. The illumination fiber is pressed onto the eye and the pressure is measured in the anterior chamber. Three different pressures are applied, 23, 78 and 132 mmHg. A detection fiber with diffusing fiber tip is inserted into the eye at the desired position. The eyes were divided in groups with high and less pigmentation to investigate the influence of the pigmentation on the intraocular irradiance.

RESULTS

The intraocular irradiances Eintra increases for various increasing applied pressures with the illumination fiber on the eyewall and for various positions inside the eye. With this the irradiances weighted with the photochemical and thermal hazard weighting function, EA-R and EVIR-R, also increases. Differences in Eintra, EA-R and EVIR-R could be found for different pigmented eyes as these values are higher for less pigmented eyes than for strong pigmented ones.

CONCLUSION

The hazard to the retina during diaphanoscopic illumination of the eye depends on how strong the surgeon presses the illumination fiber on the eyewall. Depending on the applied pressure and the measuring position in the eye, the specified limit for the photochemical hazard to the retina is partly exceeded. The pigmentation of the eye also plays a role. The irradiance in less pigmented eyes appears to be higher than in strongly pigmented eyes. Because of this, the surgeon should be able to adjust the intensity of the light source to the color of the patient's eye.

Influence of the scleral indentation technique on the re-detachment rate following retinal detachment surgery

Purpose

The aim of this study was to determine whether the choice of scleral indentation technique during primary rhegmatogenous retinal detachment surgery has an influence on the risk of re-detachment.

Methods

We included retrospectively 154 eyes with a primary rhegmatogenous retinal detachment treated in the Eye Clinic Sulzbach/Saar Germany, who were operated on by two experienced surgeons using the same basic surgical setup. Surgeon A performed an external 360° indentation, shaved the vitreous base using the light pipe cap, and used the operating microscope (opm) for direct visualization. Surgeon B performed an external 360° indentation, shaved the vitreous base using a simple indentor, and used an endoillumination (light pipe) with the opm and a handheld widefield lens for direct visualization.

Results

Comparing both indentation procedures, 15.66% (13/83) of patients operated on by surgeon A and 9.86% (7/71) of patients operated on by surgeon B had a retinal re-detachment within a follow-up period of 6 months (adj. p = 0.64, two-proportion Z-test).

Conclusion

The rate of retinal re-detachment could be influenced by the indentation technique at the end of surgery favoring external indentation and internal visualization with an endoilluminator (chandelier light). We attribute this to the better visualization of the vitreous base facilitated by endoillumination. However, many variables play a role in the development of retinal re-detachment, requiring further studies with a larger number of patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40942-022-00362-8.

What we already know:

Scleral indentation is widely recognized as an important step in rhegmatogenous retinal detachment surgery via pars-plana vitrectomy.

There are several surgical techniques for scleral indentation, however the procedures are neither standardized, nor have they ever been compared to one another to the best of our knowledge.

What this study adds:

This study shows that the rate of retinal re-detachment could be influenced by the indentation technique at the end of surgery favoring external indentation and internal visualization with an endoilluminator (chandelier light).

We attribute this to the better visualization of the vitreous base facilitated by endoillumination.