Patients experience Fuchs’ endothelial corneal dystrophy (FECD) may be asymptomatic for a period of time, but experience visual impairment as the condition advances. Recently, Japanese researchers aimed to describe factors that show the patient has reached the threshold at which visual symptoms manifest. They investigated correlations between disease severity grading, corneal scatter and higher order aberrations (HOAs) and visual function in Fuchs’ patients.

Be mindful that FECD patients graded level 3 or higher are likely to experience forward and anterior backward light scatter affecting visual performance. Photo: Christine Sindt, OD. Click image to enlarge.

The study was observational and included a total of 49 eyes of 27 FECD patients as well as 10 eyes of 10 healthy controls. Corrected distance visual acuity (CDVA) was evaluated. Visual function and explanatory variables were analyzed, including age, modified Krachmer grade, central corneal thickness (CCT), anterior segment OCT-based grade, higher-order aberrations (HOAs), intraocular straylight and corneal densitometry.

After analysis, the researchers found significant association between visual function and modified Krachmer grade, CCT, anterior segment OCT-based grade, HOAs, intraocular straylight and corneal densitometry. Decreased visual function threshold was identified to be confluent corneal guttae equivalent to a modified Krachmer grade of ≥3. Multivariate analysis revealed all visual function parameters were significantly associated with corneal densitometry, while HOAs were associated with CDVA but not contrast sensitivity. Their results were recently published in Investigational Ophthalmology & Visual Science.

In the discussion section of the paper, the authors relay that a Krachmer grade of ≥3 is when corneal guttae become confluent. As has been previously reported, corneal guttae without edema can affect quality of vision in FECD patients. In the current study, it was demonstrated that corneal guttae affect visual function once they become confluent. They further explain that in patients with an anterior segment OCT-based grade of 1, visual function was impaired; those with this grade included those with modified Krachmer grades of 2, 3 and 4. Thus, the authors contend, “anterior segment OCT-based grading appears not to be particularly sensitive for the evaluation of visual dysfunction.”

Visual function was found to be correlated significantly with all HOAs and forward and backward light scatter. In the group of those with a modified Krachmer grade of ≥3, those with 0mm to 2mm of central corneal densitometry values of the posterior layer ≥10 GSU had decreased CDVA. Consequently, the authors speculate that “this might suggest that corneal densitometry would be more valuable than the modified Krachmer grade to determine patients with significantly decreased visual function.”

Because of this, the authors state that they “believe that corneal backward light scatter is the most influential factor affecting visual function.”