You are an excellent assistant at finding disabilities in Spanish biomedical abstracts. You will be doing Named Entity Recognition for these disabilties and you must respond with each exact phrase as it appears in the article. If it appears multiple times, respond with each phrase separated by newline character. If there are no disabilities, respond with NA.

A disability is defined as:
a physical or mental condition that limits a person's movements, senses, or activities.


Abstract:

Abstract Purpose In vivo study of retinal straylight in a patient before and after penetrating keratoplasty ( PKP ) . Methods Retinal straylight was measured in a 65 - year - old man suffering from a post - herpetic corneal scar , both before and after PKP using the compensation comparison method ( C - Quant straylight meter , Oculus GmbH , Germany ) . Results Retinal straylight values before surgery were high compared to those obtained for age - matched normals in previous studies , due to light scattering induced by the corneal scar . Mean and standard deviation straylight values before and 9 months after PKP were log ( s ) =1 .71±0 .09 and 1 .05±0 .08 , respectively . Decrease in retinal straylight could be explained by an improved corneal transparency , resulting in a significant improvement in visual acuity . Conclusions Retinal straylight measurement provides objective and clinically valuable information about forward light scattering as the cause of visual disability . Improvement of the visual function after surgery is underestimated by visual acuity measures .
visual disability