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. 1997 Sep;81(9):789–794. doi: 10.1136/bjo.81.9.789

Local hypothermia protects the retina from ischaemic injury in vitrectomy

K Tamai 1, E Toumoto 1, A Majima 1
PMCID: PMC1722302  PMID: 9422935

Abstract

AIMS—Hypothermic irrigating solutions were used during vitrectomy in pressure induced ischaemic eyes so that their effects on retinal function and histological changes could be investigated.
METHODS—After anaesthetised albino rabbits underwent closed vitrectomy, their vitreous cavities were continuously irrigated for 30 minutes at a perfusion pressure of 140 mm Hg. The rabbits were divided into three groups according to their intraocular perfusion temperatures—8°C, 22°C, and 38°C. Electroretinograms were taken before and after irrigation. Glutamate levels in the vitreous were examined after irrigation. Eyes were enucleated on the seventh postoperative day and examined histologically.
RESULTS—On the seventh postoperative day, the recovery rate of a-wave amplitudes was significantly lower in the 38°C group than in the 8°C group, and that of b-wave amplitudes was significantly lower in the 38°C group than in either the 8°C or 22°C group. Retinal damage in the 38°C group revealed more severe histological impairment than in either the 8°C or 22°C group. Oedema of the inner retinal layer was significant in both the 22°C and 38°C groups. Glutamates reached peak values 30 minutes after the end of ischaemia in the 38°C group. However, no significant glutamate increases were detected 15 to 60 minutes after ischaemia in either the 8°C or 22°C group.
CONCLUSION—Local hypothermia during vitrectomy in acute ischaemic eyes appears to decrease retinal damage.



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Figure 1  .

Figure 1  

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The vitreous cavity is irrigated at perfusion pressure of 140 mm Hg. The pressure at the outflow site is maintained at about 120 mm Hg.

Figure 2  .

Figure 2  

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A sample for the evaluation of inner retinal layer (IRL) thickness, a region with a width of 420 µm at a distance of 6.0 mm from the ora serrata. The IRL thickness was measured and averaged from four values in each region. Vertical bars indicate IRL thickness.

Figure 3  .

Figure 3  

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Relative ERG recovery of a-wave (A) and b-wave (B) amplitudes (n=7). *p<0.05, **p<0.01. Error bars represent standard deviations.

Figure 4  .

Figure 4  

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Histological findings of retinal damage by grade (haematoxylin and eosin stained, × 240). (A) Grade 0. Retina of a non-operated eye. (B) Grade 1. Retina that underwent 8°C irrigation. (C) Grade 2. Retina that underwent 8°C irrigation. Proliferation of retinal pigment epithelial cells is observed. (D) Grade 2. Retina that underwent 22°C irrigation. Retinal oedema with inflammatory cell infiltration is observed. (E) Grade 3(a). Retina that underwent 22°C irrigation. (F) Grade 4(a). Retina that underwent 38°C irrigation. (G) Grade 4(b). Retina that underwent 38°C irrigation. Retina is extensively disorganised and thinned.

Figure 5  .

Figure 5  

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The thickness of inner retinal layer (IRL). Perfusion at 8°C ( n=35), perfusion at 22°C (n=35), and perfusion at 38°C ( n=29) (non-operated eyes; n=105). *p<0.01. Error bars represent standard deviations.

Figure 6  .

Figure 6  

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Changes in glutamate (A) and serine (B) levels in the vitreous after ischaemia (n=5). *p<0.01. Error bars represent standard deviations.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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