skip navigation

E-mail to a friend

Home » Resources » Clinical Studies » An Observational Study of the Development of Diabetic Macular Edema Following Scatter Laser Photocoagulation

An Observational Study of the Development of Diabetic Macular Edema Following Scatter Laser Photocoagulation

Purpose:

To determine the incidence and extent of macular edema following scatter laser photocoagulation surgery using optical coherence tomography (OCT) in eyes without macular edema prior to scatter laser photocoagulation.
To explore whether the incidence and extent of macular edema varies according to the number of sittings included in the treatment regimen.

Background:

The development or worsening of macular edema following full scatter photocoagulation is a well recognized occurrence. However, there is limited literature in this regard. Most of the literature consists of case reports and case series. Shimura et al conducted a randomized trial of 36 patients with type 2 diabetes who had bilateral symmetric severe nonproliferative or early proliferative retinopathy but did not have clinically significant macular edema. Visual acuity was 20/20 or better in each eye. Patients were randomized to receive scatter photocoagulation weekly in one eye and biweekly in the other eye. Macular thickness was measured with OCT weekly for 8 weeks and then after 12 weeks and 16 weeks. Seven eyes of four patients were excluded because the eyes developed macular edema with a more rapid and progressive course than did the remaining eyes. Ninety percent of eyes maintained their visual acuity level and did not develop clinically significant macular edema, although many eyes had a transient increase in retinal thickness. Among the eyes maintaining their level of visual acuity, central retinal thickness increased by 42% and among eyes that had a reduction in visual acuity, central retinal thickness increased by 150%. There was a greater increase in central retinal thickening in the eyes treated weekly than in the eyes treated biweekly and the resolution of the edema was slower in the eyes treated weekly. This study, although it provides meaningful data, does not provide sufficient data for a precise estimate of the incidence of macular edema after scatter photocoagulation and the sample size is too small to explore factors that may be associated with an increased risk of macular edema. The Early Treatment Diabetic Retinopathy Study (ETDRS), which was performed prior to OCT availability, found that among eyes with no central retinal thickening at baseline in graded fundus photographs, retinal thickening was present at 4 months in 16% of eyes that underwent full scatter photocoagulation compared with 12% in eyes for which scatter photocoagulation was not performed.

The full scatter photocoagulation can be given in a single sitting or can be spread out over several sittings. A survey of the Diabetic Retinopathy Clinical Research Network (DRCRnet) investigators found that for early proliferative or severe nonproliferative retinopathy, 10 (27%) would administer the photocoagulation in a single sitting, 11 (31%) in 2 sittings, and 15 (42%) in 4 sittings.

Description:

The study is designed as a prospective, multi-center nonrandomized clinical trial.

Study eyes will receive scatter photocoagulation given by one of the following two regimens to be selected by the investigator at his/her discretion:

1 sitting with a minimum of 1200 to a maximum of 1600 burns, with one burn width separation of burns and scatter extending from the peripheral arcades to beyond the equator.
4 sittings, each separated by four weeks (+4 days), with approximately 300 burns in each of the first two sittings and investigator judgment for number of burns for the third and fourth sittings as long as the total for the four sittings is between 1200 and 1600 burns.

Both of these regimens conform with usual clinical practice. To reduce selection bias, investigators will be required, prior to study initiation, to indicate which treatment (1 PRP sitting or 4 PRP sittings) they will administer. Only the selected treatment will be performed by a given investigator on study eyes.

Patient Eligibility:

Subject-level Inclusion Criteria

To be eligible, the following inclusion (1-3) and exclusion criteria (4-7) must be met:

1. Age >= 18 years

2. Diagnosis of diabetes mellitus (type 1 or type 2)

3. Able and willing to provide informed consent.

Exclusion

A patient is not eligible if any of the following exclusion criteria (5-8) are present:

4. History of chronic renal failure requiring dialysis or kidney transplant.

5. History of pancreatic transplant.

6. A condition that, in the opinion of the investigator, would preclude participation in the study (e.g., unstable medical status including blood pressure and glycemic control).

7. Patient is expecting to move out of the area of the clinical center to an area not covered by another clinical center during the next 8 months.

Study Eye Criteria

The patient must have at least one eye meeting all of the inclusion criteria (a-d) and none of the exclusion criteria (e-k) listed below. A patient can have only one study eye. If both eyes are eligible, the investigator at his/her discretion will select one to be the study eye. The eligibility criteria for a study eye are as follows:

Inclusion

a. Presence of early proliferative or severe nonproliferative diabetic retinopathy for which investigator intends to perform full scatter photocoagulation in either one sitting or four sittings.

b. Central subfield thickness on OCT <= 299 microns.

c. Visual acuity 73 letters or greater (20/32 or better).

d. Media clarity, pupillary dilation, and patient cooperation sufficient to administer full scatter photocoagulation and obtain adequate fundus photographs and OCT.

Exclusion

e. Prior scatter photocoagulation.

f. High risk (severe proliferative) retinopathy.

g. Presence of an ocular condition (other than diabetes) that, in the opinion of the investigator, might produce macular edema or alter visual acuity during the course of the study (e.g., vein occlusion, uveitis or other ocular inflammatory disease, neovascular glaucoma, Irvine-Gass Syndrome, significant vitreomacular interface disease, etc.).

h. Treatment for diabetic macular edema is planned.

i. History of any treatment for DME within prior 6 months, including focal/grid macular photocoagulation and corticosteroids by any route.

j. History of major ocular surgery (including cataract extraction, vitrectomy, scleral buckle, any intraocular surgery, etc.) within prior 6 months or anticipated within the next 8 months following enrollment.

k. History of YAG capsulotomy performed within 2 months prior to enrollment.

Patient Recruitment Status:

No longer recruiting. Comments: Recruitment ended April 30, 2007.

Current Status of Study:

Completed, with results not yet published. Comments:

Results:

None at this time.

Publications

None

Clinical Centers

Arizona

California

Colorado

Florida

Hawaii

Illinois

Indiana

Louisiana

Maryland

Massachusetts

Michigan

Missouri

New Jersey

New York

North Carolina

Ohio

Rhode Island

South Carolina

Tennessee

Texas

Wisconsin

NEI Representative

maryann.redford@nei.nih.gov

Resource Centers

Coordinating Center

rbeck@jaeb.org

Fundus Photograph Reading Center

rdanis@rc.ophth.wisc.edu

Network Chairman's Office

nbressler@jhmi.edu

Last Updated: 8/18/2009

U. S. Department of Health and Human Services

National Institutes of Health