AUG 06, 2012
This prospective, nonrandomized study found that subclinical macular edema after uneventful conventional phaco occurs mainly due to changes in the outer nuclear layer, and the use of a femtosecond laser may reduce postop inflammation and macular edema risk.
It surprises me that femto created less edema in the outer nuclear layer than conventional phaco because it seems there is more opportunity for prostaglandin release when the capsule is opened before the lens is removed. I do think this is an important finding if it is true.
The authors used OCT to compare changes in macular morphology after femtosecond laser–assisted phaco versus conventional phaco in 25 patients. Total retinal thickness of the macula was evaluated using Stratus OCT four to eight weeks postoperatively. The images were segmented using OCT retinal image analysis software. Regional thickness data in the central area, inner rings and outer rings were obtained and absolute and relative thicknesses of the individual retinal layers in the two study groups compared. Relative thickness was calculated as the ratio of the retinal layer to the total retinal thickness.
Retinal thickening occurred in both the femtosecond and conventional group four to eight weeks after cataract surgery. Macular edema was mainly detectable as thickening of the outer nuclear layer in the inner and outer macular ring in both groups; it was not seen in the central foveal area.
However, the femtosecond group showed a significantly smaller increase in absolute and relative outer nuclear layer thickness values compared to the conventional group. This significant difference in layer thickness at the same location, the authors write, suggests a similar pathophysiologic background in the formation of postoperative subclinical cystoid macular edema in both groups.
The authors conclude that subclinical macular edema after uneventful phacoemulsification is due to changes in the outer nuclear layer of the retina, comprising the photoreceptors, but the mechanism of this phenomenon is not yet known. The results also support the view that femtosecond laser–assisted cataract surgery may provide an option for less traumatic cataract extraction, and thus reduced postoperative inflammation and a smaller risk for macular edema.