Diode laser iridotomy in rabbit and human eyes

Corneal disease in patients with chronic renal insufficiency undergoing hemodialysis

PURPOSE

To evaluate alterations of the corneal endothelium in patients undergoing hemodialysis for renal insufficiency.

METHODS

Sixty-six patients undergoing hemodialysis received a complete ophthalmologic examination. The state of the endothelium was assessed using pachymetry and specular microscopy. The group of patients undergoing dialysis was divided according to the time of dialysis, aluminum, product of calcium and phosphate in blood, and parathyroid hormone to analyze the influence of these factors. The possible presence of iron and aluminum in the aqueous humor of patients who underwent and those who did not undergo hemodialysis was also estimated.

RESULTS

Patients undergoing hemodialysis did not have significant corneal edema. Cell density was significantly lower in patients undergoing dialysis than in patients not undergoing dialysis; this reduction appeared to be associated with length of dialysis and was unrelated to serum aluminum and calcium levels. Patients undergoing dialysis did not have cell polymorphism or polymegethism, although there was a tendency toward increased polymegethism with length of dialysis. Aluminum and iron were not increased in the aqueous humor of patients undergoing dialysis.

CONCLUSIONS

The alteration of the endothelium that we found is not related to the elements studied. It is possibly the result of another product dissolved in the anterior chamber or to the alterations of the anterior segment that these patients are known to have.

Corneal transmissibility of diode versus argon lasers and their photothermal effects on the cornea and iris

PURPOSE

Diode laser (810 nm) may possess theoretical advantages over the argon blue-green laser (488 nm) for iridotomy/iridoplasty in an eye with oedematous cornea, such as the acute angle-closure glaucoma (AACG) patient, because of better diode laser tissue penetration in opaque media. We assessed the transmissibility of diode and argon lasers through corneas of varying clarity and evaluated the histopathological features of cornea and iris burns produced by these lasers.

METHODS

The transmission of diode and argon lasers through human donor corneal buttons of three grades of clarity--clear, intermediate, and hazy--were compared. Corneal buttons of these varying levels of clarity were also treated with argon and diode lasers, with the beams deliberately focused onto the mid-stroma to assess their photothermal effects. Exposed pigmented irides from whole human eyes were treated directly with argon and diode lasers. The lasers were delivered via slit-lamp systems and the energy settings used were 1000 mW for argon and 980 mW for diode; spot sizes for both lasers were 100 microm, with exposure durations of 0.1 s. Light microscopy studies of these tissues were performed.

RESULTS

Transmissibility of diode laser in clear, intermediate, and hazy corneas were 89, 87 and 85% respectively and was significantly superior to argon laser (78, 73 and 70% respectively; P < 0.001, paired Student's t-test). Diode laser did not produce morphological changes in all three grades of corneas whereas argon-laser-treated hazy corneas showed photothermal damage. Both lasers produced deep iris burns, with the diode laser tending to produce deeper burns.

CONCLUSION

Our findings suggest that diode laser may be the ideal laser for iridotomy/iridoplasty in the AACG patient with hazy cornea.

Analysis of diode, argon, and Nd: YAG peripheral iridectomy in cadaver eyes

We compared semiconductor diode, neodymium (Nd): YAG and argon laser iridectomies performed in 14 cadaver eyes using Miyake videographic, histologic and scanning electron analysis. We found that the diode laser created an iridectomy in < 10 applications in blue, hazel and brown irides using 1000-1200 mW over 0.5 seconds. In hazel and blue irides the argon laser created iridectomies at parameters similar to the diode, but required multiple low energy burns in brown irides. Scanning electron microscopy showed pigment epithelial loss with the diode and Nd:YAG laser, and heaped up epithelium at the iridectomy site with the argon laser. Nd:YAG laser had the greatest iridectomy size. This study suggests a possible clinical advantage of diode versus argon laser iridectomies in reduced applications in brown irides and in preventing postoperative pigment occlusion. However, diode laser demonstrated no definite advantage over Nd:YAG laser.