Original article
Spectral transmission of the pig lens: Effect of ultraviolet A + B radiationTransmission spectrale du cristallin du porc : l’effet du rayonnement ultraviolet A + B

https://doi.org/10.1016/j.jfo.2014.06.006Get rights and content

Summary

Objective

To determine the spectral transmission curve of the crystalline lens of the pig. To analyse how this curve changes when the crystalline lens is irradiated with ultraviolet A + B radiation similar to that of the sun. To compare these results with literature data from the human crystalline lens.

Procedures

We used crystalline lenses of the common pig from a slaughterhouse, i.e. genetically similar pigs, fed with the same diet, and slaughtered at six months old. Spectral transmission was measured with a Perkin-Elmer Lambda 35 UV/VIS spectrometer. The lenses were irradiated using an Asahi Spectra Lax-C100 ultraviolet source, which made it possible to select the spectral emission band as well as the intensity and exposure time.

Results

The pig lens transmits all the visible spectrum (95%) and lets part of the ultraviolet A through (15%). Exposure to acute UV (A + B) irradiation causes a decrease in its transmission as the intensity or exposure time increases: this decrease is considerable in the UV region.

Conclusions

We were able to determine the mean spectral transmission curve of the pig lens. It appears to be similar to that of the human lens in the visible spectrum, but different in the ultraviolet. Pig lens transmission is reduced by UV (A + B) irradiation and its transmission in the UV region can even disappear as the intensity or exposure time increases. An adequate exposure intensity and time of UV (A + B) radiation always causes an anterior subcapsular cataract (ASC).

Résumé

Objectif

Déterminer la courbe de transmission spectrale du cristallin du porc. Analyser comment cette courbe change quand le cristallin est irradié avec un rayonnement ultraviolet (A + B) semblable à celui du soleil. Comparer ces résultats avec des données existantes dans la bibliographie du cristallin humain.

Procédures

Nous avons utilisé les cristallins du porc commun d’abattoir, c’est-à-dire des porcs génétiquement similaires, avec le même régime alimentaire et abattus à six mois. La transmission spectrale a été mesurée à l’aide d’un spectrophotomètre Perkin-Elmer Lambda35 UV/VIS. Les cristallins ont été irradiés en utilisant la source d’ultraviolets Asahi Spectra Lax-C100, qui nous a permis de choisir la bande d’émission de spectre aussi bien que l’intensité et le temps d’exposition.

Résultats

Le cristallin du porc transmet tout le spectre visible (95 %) et laisse passer une partie de l’ultraviolet A (15 %). L’exposition aux radiations UV (A + B) provoque une diminution de la transmission à mesure qu’augmentent l’intensité de la radiation ou le temps d’exposition. Cette diminution est considérable dans la région UV.

Conclusions

Nous avons pu déterminer la courbe de transmission spectrale moyenne du cristallin de porc. Elle s’avère être semblable à celle du cristallin humain dans le spectre visible, mais différente dans la région des ultraviolets. Dans ce dernier cas, la transmission se réduit pour les UV (A + B), et peut même disparaître dans la région UV en fonction de l’augmentation du temps d’exposition ou de l’intensité. Une intensité et un temps d’exposition de rayons UV (A + B) suffisants provoquent toujours une cataracte sous-capsulaire antérieure dans le cristallin du porc.

Introduction

Numerous studies state that ultraviolet radiation (UV) is one of the factors that most influences the loss of transparency of the crystalline lens (cataracts) in both humans and animals [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. Several studies with rats [5], [6], [7], [8], [9], [10], [11] and rabbits [13] show the influence UV radiation bears on the development of cataracts.

For different reasons, swine ophthalmology has historically received little attention [14]. Consequently, there are few studies on the porcine eye in the literature and fewer focusing on its optical properties. However, currently a greater interest has emerged in the study of the eye of the pig because it is used as a model in investigation [15], [16], [17] since it does not have the ethical and economic restrictions of other species and it shares many similarities with the human eye. The porcine eye is phylogenetically close to the human eye, since, for example, it does not have a tapetum lucidum, it has holangiotic retinal vascularisation, it has cones on the external retina, and the thickness, shape and size of the sclera is similar to that of the human lens [18]. Thus, some inferences may be made to the human lens.

In the human eye, it is complicated to determine the influence of the UV radiation precisely on the development of opacities as it is difficult to isolate its effect from other factors that can also bear an influence. Nonetheless, some epidemiologic [1], [2] studies have been performed in humans with a view to analysing the effect that exposure to sunlight, especially ultraviolet B (UVB) radiation, has on crystalline lens opacification. Sunlight is the principal source of ultraviolet radiation for most of the world's population. This fact now has considerable interest in the era of ozone depletion and potential for even greater exposure to UVB. The Chesapeake Bay Waterman Study [1] was the first investigation to develop a detailed model of personal ocular exposure to UVB, and correlate it with a detailed standardised system for cataract assessment. An increased risk of cortical opacity was found with increasing average annual ocular UVB exposure. Likewise, the Beaver Dam Eye Study [2] reveals a significant correlation between exposure to UVB radiation and cortical opacities.

Deduction from animal data to the human situation is always questionable. However, it is the only option for development of empirically based safety recommendations for avoidance of cataract after exposure to UV radiation.

The use of the porcine eye as a research model involves studying its specific characteristics, therefore diverse studies on the pig eye have been performed [18], [19], [20], [21]. Regarding the action of UV radiation on the pig lens, Oriowo et al. [22] analysed in vitro the action spectrum for acute UV cataractogenesis using whole cultured lenses. They used wavebands ranging from 270 to 370 nm and studied the intensity thresholds that produce permanent and reversible damage. Along the same lines, Okuno et al. [23] performed a similar study to determine ultraviolet action spectra for cell killing of primary porcine lens epithelial cells, using a waveband range from 235 to 311 nm. These research works are particularly important for studying cataractogenesis and they show that the waveband between 270 and 315 nm is the most dangerous in general.

However, practically no solar radiation reaches the Earth's surface [24], [25], [26] below 300 nm nor do artificial sources emit below 400 nm [27]. Therefore, in natural conditions, the formation of lens opacities due to UV radiation cannot be as a result of wavelengths under 300 nm more or less.

The purpose of this study is to determine the mean spectral transmission curve of the common pig lens, with a view to defining said curve for the species, and how ultraviolet A + B radiation affects porcine lens transmission. Then we analysed the effect controlled exposure to ultraviolet radiation ranging from 300 to 400 nm had on in vitro porcine lens. This UV radiation band corresponds approximately to that which reaches the Earth's surface from the sun. The effect such radiation produces on the porcine lens will be analysed in two ways: (1) how its spectral transmission varies, and if so what type and quantity of radiation the lens lets through, and (2) if opacities occur and if so, what type.

Finally, we will compare the results with the existing data in the literature on the human lens.

Section snippets

Pig lens

We used the lenses of freshly slaughtered common pigs from an industrial abattoir for our experiments. The pigs were slaughtered at six months of age and the eyes were removed at the same time, stowed in suitable recipients in saline solution, and sent to our laboratory five or six hours afterwards where the lenses were then removed. Therefore, all the eyes we used belonged to genetically similar pigs that were fed the same diet and that were slaughtered at the same age: thus, our study was

Results

We measured the transmission of twelve crystalline lenses, randomly selected, to establish the baseline. The Kolmogorov-Smirnov test confirmed that the variable follows a normal distribution (P > 0.50 for any wavelength). As the standard deviations were small for all values of wavelength (λ), we investigated if three measurements would be enough to establish a transmission curve. Fig. 1 shows the mean and the confidence interval from three spectral transmission curves of three porcine lenses. In

Spectral transmission of the common pig lens

The spectral transmission curve of the common pig lens (Fig. 1) shows that this lens lets the whole visible spectrum through with practically no attenuation (about 95 % transmission). However, from the 400 nm wavelength onwards and towards the short wavelengths, an abrupt decline in transmission commences which stops at about 370 nm; from there on the transmission remains constant at about 15 % up to 320 nm where it drops abruptly. This wavelength can be considered as the cut-off point since

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

Funding: partially supported by Cátedra Alcon-Universitat de València.

References (29)

  • X. Dong et al.

    Ultraviolet radiation-induced cataract: age and maximum acceptable dose

    Invest Ophthalmol Vis Sci

    (2003)
  • V.C. Mody et al.

    Ultraviolet radiation-B induced cataract in albino rats: maximum tolerable dose and ascorbate consumption

    Acta Ophthalmol Scand

    (2006)
  • V.C. Mody et al.

    High lenticular tolerance to ultraviolet radiation-B by pigmented guinea-pig; application of a safety limit strategy for UVR-induced cataract

    Acta Ophthalmol

    (2012)
  • M.N. Ayala et al.

    Influence of exposure time for UV radiation-induced cataract

    Invest Ophthalmol Vis Sci

    (2000)
  • Cited by (8)

    • The mechanism of the interaction of α-crystallin and UV-damaged β<inf>L</inf>-crystallin

      2019, International Journal of Biological Macromolecules
      Citation Excerpt :

      In particular, it was observed that the number of cataract extractions increases with the decrease in latitude [27]. Despite the fact that most of the shortwave UV radiation is scattered by the atmosphere and the eye cornea, ultraviolet light B (UVB) reaches the lens [28,29]. The Alienor Study (Bordeaux, 2006–2008) has shown that excess of UVB radiation exposure, received during lifetime, above 1 kJ cm−2 increases the risk for cataract development by 1.53 times [30].

    • Solar ultraviolet radiation cataract

      2017, Experimental Eye Research
      Citation Excerpt :

      Many birds have a high transmittance in the UVA waveband, which facilitates the use of their UV sensing photoreceptors (Lind et al., 2014). Pig lens UV transmittance was similar in two studies (Tsukuhara et al., 2014; Artigas et al., 2014) with the latter showing a decreased UV transmittance after exposure to UVA + UVB radiation. 3-Hydroxykynurenine O-beta-D-glucoside (3OHKG) decreases in the human lens nucleus with age, while the levels of three novel kynurenine metabolites increase.

    View all citing articles on Scopus
    View full text