Study: ERG can help diagnose endophthalmitis

Electroretinogram in some patients can indicate a poor prognosis in patients undergoing IOL implantation.

NAGOYA, Japan — A single-flash electroretinogram can help predict the visual outcome of endophthalmitis after IOL implantation and the virulence of the causative organism, study here states.

Combined findings of an electroretinogram (ERG) b-wave:a-wave ratio of less than 1.0 and onset of endophthalmitis within 1 week of IOL surgery may indicate a highly virulent causative organism and poor visual prognosis, according to Naoichi Horio, MD, and colleagues at the Nagoya University School of Medicine.

Previous animal studies have shown that organisms detected in eyes with a b-wave:a-wave (b:a) ratio of less than 1.0 “cause irreversible change in the retina within a few days,” Dr. Horio said.

“These data indicate that eyes with remarkably reduced b-wave and early onset endophthalmitis require immediate treatment before the retina is destroyed,” he continued.

The Endophthalmitis Vitrectomy Study found that pars plana vitrectomy was beneficial only for endophthalmitis patients who presented with severe visual loss to the level of light perception only, Dr. Horio pointed out.

“It is important to assess the problem from the point of the preoperative ERG as well as the preoperative visual function,” he said.

In patients with opacified media, this technique can provide information on retinal function, Dr. Horio said. It is not influenced by media opacity in severely inflamed eyes.

Sixteen patients

Dr. Horio and colleagues reviewed the medical records of 16 eyes in 16 patients with endophthalmitis following IOL implantation. Ten men and six women ranging in age from 58 to 83 years were included. The original surgical procedures that led to the endophthalmitis were phacoemulsification following IOL implantation in 15 eyes and secondary IOL implantation in one eye.

The treatment for 13 eyes included vitrectomy and IOL removal. Three eyes were treated with IOL removal and intravitreal injection of gentamicin (0.5 mg/0.1 mL). Intraocular specimens were obtained during vitrectomy or IOL removal.

The preoperative ERGs were taken by a 20-J single-flash light (PE-3000; Tomey) after 30 minutes of dark adaption. The ERG findings, duration until the onset of symptoms or signs, culture results and postop visual acuity were analyzed. The postop visual acuity was measured at the latest examination, 3 to 48 months after treatment.

In four eyes, the b:a ratio was less than 1.0, and the duration until the onset of endophthalmitis was less than 1 week. Postoperative visual acuity in these patients ranged from no light perception to 20/200. One eye cultured positive for Pseudomonas aeruginosa and three eyes cultured positive for Enterococcus faecalis.

Postop visual acuity of these eyes was significantly worse than that of the other 12 eyes, which ranged from 20/100 to 20/15, using the Mann-Whitney U-test (P = .0035). In those 12 eyes, Staphylococcus epidermidis was found in one eye, glucose non-fermentative gram-negative rods were found in two eyes and Propionibacterium acnes was found in one eye, according to the study.

Of those 12 eyes, four eyes also registered a b:a ratio below 1.0, yet achieved a postop visual acuity of 20/100 to 20/20. Preoperatively the visual acuity of this group ranged from only hand-motion visible to 20/200, the authors indicated.

Conclusion

Dr. Horio said that even in this small study, results were consistent with animal studies that have described a rapid de crease in b-wave amplitude in end oph thalmitis with highly virulent organisms.

Further study of this diagnostic technique are of interest but have not yet been undertaken, Dr. Horio said.

“The purpose of the study would be not only to confirm the ability of this diagnostic method to classify the severity of endophthalmitis, but also to study how treatment, including vitrectomy and intravitreal injection of antibiotics, should be performed in eyes according to their classification with ERG,” he said.

Co-authors of the study were Hiroko Terasaki, MD, Etsuko Yamamoto, MD, and Yozo Miyake, MD.

For Your Information:

Naoichi Horio, MD, can be reached at the Department of Ophthalmology, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466-0065; fax: +(81) 52-744-2278; e-mail: naoichi@med.nagoya-u.ac.jp. Dr. Horio has no direct financial interest in any products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Reference:

Horio N, Terasaki H. Electroretinogram in the diagnosis of endophthalmitis after intraocular lens implantation. Am J Ophthalmol. 2001;132:258-259.