Interpreting Beam Geometry and Repeated Exposure in Dermatologic Laser Therapy

Studies of spot size, beam profile, and repeated laser exposure often appear to support conflicting treatment choices.Some compare equal pulse energy, others match surface radiant exposure, and others adjust several settings to reach a clinical endpoint.This critical narrative review examines how those choices determine what can be concluded about efficacy and safety.A documented PubMed search through October 1, 2026, was supplemented by citation checking and a previously assembled bibliography.Seventeen primary reports underwent detailed extraction of exposure settings, controlled variables, measurement methods, experimental units, and outcomes.The review distinguishes evidence about an optical mechanism from evidence about a complete treatment strategy.A pigment treatment trial found similar observed clearance with fewer unwanted reactions when a larger spot, lower fluence, and absence of whitening were combined, but did not isolate the contribution of spot size.Studies of repeated vascular exposure reported both improved blanching and no additional benefit under different pulse sequences and cooling schedules.Small descriptive comparisons did not establish equivalence, and histologic depth could not establish clinical improvement or safety.In one resurfacing report, a cumulative depth was the sum of means from separate treatment groups rather than the measured depth after repeated passes.These examples support a practical approach to appraisal: define the contrast, identify how exposure was established, and interpret the outcome at the correct experimental level.The contribution is a critical explanation of what published comparisons support, rather than a new dose formula.Similar target response should not be taken to imply similar collateral injury or justify transfer of settings between devices.