Prophylactic treatment shown to prevent spontaneous giant retinal tears in study

Although the study confirmed the effects of cryotherapy, prophylactic laser treatments may be the better clinical choice.

ByMichael Piechocki

Prophylactically treating the contralateral eyes of patients with spontaneous giant retinal tears can reduce the chance of retinal tears and detachments developing later in those eyes, a small retrospective study indicates.

Thomas J. Wolfensberger, MD, G. William Aylward, MD, and Peter K. Leaver, MD, conducted the study to evaluate the long-term effect of prophylactic peripheral 360° retinal cryotherapy in the fellow eyes of patients with spontaneous giant retinal tears.

According to previous studies, patients with giant retinal tears often have a combined incidence of retinal breaks or detachments in their fellow eyes of up to 60%.

This new study included 48 patients with a mean age of 42 ± 2 years and an average refraction of –4 ± 0.8 D in their phakic fellow eye. All patients were treated between 1979 and 1982.

Giant retinal tears

According to Thomas J. Wolfensberger, MD, giant retinal tears occur when the retina rips at the posterior margin of the vitreous base (Figure 1). This leaves a small amount of retina anterior to the tear at the ora serrata while the remainder of the retina tears in a line extending 90° or more, resulting in a tear of at least 3 clock hours. The posterior edge of a giant retinal tear usually retains no attached vitreous, and thus the flap may readily invert.

Although their cause is not specifically known, spontaneous giant retinal tears mainly develop in eyes with moderate to marked myopia, he said.

The pathophysiology of the detachment is thought to be due to condensation of the posterior vitreous base with taut transvitreal membranes in the anterior part of the vitreous cavity, which inserts into the posterior margin of the vitreous base. These areas are sometimes called white-with-pressure areas and represent the vitreous base.

Dr. Wolfensberger said that giant retinal tears usually have to be treated with pars plana vitrectomy and silicone oil followed by laser coagulation of the tear’s free border, although gas injection may be sufficient in selected cases.

“It’s thought nowadays that you should also extend the laser treatment, not only around the tear itself but also around the whole peripheral 360° … to prevent the tear from ripping further at a later time,” he said.

Over the course of follow-up, only four patients (8%) experienced retinal tears in their fellow eye.

“This evidence in favor of prophylactic treatment … may justify a prospective randomized clinical trial,” the authors wrote.

However, they continued, “such a trial would require a sample size of at least 645 patients in each arm of the study as well as long-term follow-up of at least 5 years to show an unequivocal difference in outcome. … It is unlikely that such a trial will ever be undertaken.”

Laser therapy preferred

Although cryotherapy appeared effective in the study for reducing rates of giant retinal tears in the fellow eyes, Dr. Wolfensberger told Ocular Surgery News that he prefers to use prophylactic laser treatments for such patients today.

He explained that the study included a series of patients treated at Moorfields Eye Hospital, London, as far back as 1979. At the time, the treatment strategy at the hospital was to use cryotherapy; no other treatments were readily available. Thus, the retrospective study could only evaluate the effects of cryotherapy.

Schematic diagram of a temporal spontaneous giant retinal tear with a retinal detachment in the two temporal quadrants of the right eye. Note that the large tear leaves a small area of anterior retina attached to the ora serrata.	Schematic diagram of prophylactic 360° cryotherapy to the posterior edge of the vitreous base in the fellow eye.	Schematic diagram of prophylactic 360° laser treatment in three to four rows to the posterior edge of the vitreous base in the fellow eye.
(All images courtesy of Thomas J. Wolfensberger, MD.)

“We mentioned … that nowadays laser therapy would be more appropriate as we know that it probably induces less inflammation and is generally associated with fewer side effects, such as epimacular membranes or … traction at the edge of the laser marks,” he said.

However, he said the question as to whether laser would be preferable to cryotherapy as a prophylactic treatment could only be answered through a prospective study.

“The problem is that nobody would do such a trial because we calculated that we would need a sample size of more than 600 patients in each arm and long-term follow-up of at least 5 years to show an unequivocal difference in outcome,” he said. “Technically speaking, I think it is unlikely such a trial would ever be undertaken.”

Clinical trend away from cryo

Dr. Wolfensberger noted that the prophylactic laser treatments he uses are applied to a similar extent as the cryotherapy applications. The laser is applied in three or four rows around the full 360° of the peripheral retina to cover an area similar to cryotherapy (Figures 2 and 3).

“This is a clinical decision that I cannot back up with any statistics. If you look both at the general flow of retinal therapy, which has moved from cryotherapy to laser therapy, and at the good effects you have with laser therapy for the treatment of peripheral tears and other diseases such as diabetic retinopathy, you can see a trend that all these diseases have been treated initially with cryotherapy and now everyone is using laser,” he said.

“I think putting the prophylaxis of giant retinal tears into the context of modern technology, you can deduce from the good results we found with cryotherapy that a similar effect can be obtained by laser,” he said. “Everything has moved from cryotherapy to laser. I think you can make the same step for the prophylaxis of the fellow eye of spontaneous giant retinal tears within that context.”

Dr. Wolfensberger stressed that because spontaneous giant retinal tears are very rare, hard data in the form of a prospective, controlled trial will not be coming forward in the future. The recommendations he and his co-authors made are based on a limited retrospective study.

For Your Information:

Thomas J. Wolfensberger, MD, can be reached at Hôpital Ophthalmique Jules Gonin, University of Lausanne, 15 Av. de France, CH-1004 Lausanne, Switzerland; +41-21-626-8111; fax: +41-21-626-8888; e-mail: thomas.wolfensberger@ophtal.vd.ch.

Reference:

Wolfensberger TJ, Aylward GW, Leaver PK. Prophylactic 360° cryotherapy in fellow eyes of patients with spontaneous giant retinal tears. Ophthalmology. 2003;110:1175-1177.