PURPOSE: The common change in corneal morphology that is seen in keratoconus (KC) suggests the presence of common high-order aberration (HOA) structures and the potential for HOA corrections that apply to more than one eye. The purpose of this investigation is to classify a sample of KC eyes into subgroups based on similar HOA characteristics and simulate optical performance of common HOA corrections on members of each subgroup. METHODS: High-order aberrations were recorded over a 5-mm pupil on 111 KC eyes. The eyes were divided into five subgroups based on observed commonality in HOA structure. From each subgroup, two eyes were removed for later evaluation of corrections. Principal components analysis was performed on the remaining eyes of each subgroup. The first principal component was scaled to form a set of corrections. Simulated optical correction of the test eyes was performed by identifying the magnitude of the inner-group correction providing the lowest level of residual higher order root mean square wavefront error (HORMS). Residual uncorrected HORMS was compared with levels found in uncorrected normal eyes and KC eyes wearing rigid gas-permeable corrections. RESULTS: Ninety (81%) of the 111 eyes were included in one of the five subgroups. All 10 test eyes experienced a reduction in HORMS with a template correction compared with their uncorrected levels. Median HORMS reduced from uncorrected levels of 2.14 to 0.97 μm. On average, the 10 subjects experienced a 51% reduction in HORMS (minimum, 16%; maximum, 81%; p < 0.01). When scaled to a 4-mm pupil, five of the 10 eyes experienced residual uncorrected HORMS within limits associated with gas-permeable wear. CONCLUSIONS: Overlap exists across these templates because of the dominance of vertical coma in the HOA structure. All eyes evaluated received reduced HORMS with a template-based correction.
PURPOSE: The common change in corneal morphology that is seen in keratoconus (KC) suggests the presence of common high-order aberration (HOA) structures and the potential for HOA corrections that apply to more than one eye. The purpose of this investigation is to classify a sample of KC eyes into subgroups based on similar HOA characteristics and simulate optical performance of common HOA corrections on members of each subgroup. METHODS: High-order aberrations were recorded over a 5-mm pupil on 111 KC eyes. The eyes were divided into five subgroups based on observed commonality in HOA structure. From each subgroup, two eyes were removed for later evaluation of corrections. Principal components analysis was performed on the remaining eyes of each subgroup. The first principal component was scaled to form a set of corrections. Simulated optical correction of the test eyes was performed by identifying the magnitude of the inner-group correction providing the lowest level of residual higher order root mean square wavefront error (HORMS). Residual uncorrected HORMS was compared with levels found in uncorrected normal eyes and KC eyes wearing rigid gas-permeable corrections. RESULTS: Ninety (81%) of the 111 eyes were included in one of the five subgroups. All 10 test eyes experienced a reduction in HORMS with a template correction compared with their uncorrected levels. Median HORMS reduced from uncorrected levels of 2.14 to 0.97 μm. On average, the 10 subjects experienced a 51% reduction in HORMS (minimum, 16%; maximum, 81%; p < 0.01). When scaled to a 4-mm pupil, five of the 10 eyes experienced residual uncorrected HORMS within limits associated with gas-permeable wear. CONCLUSIONS: Overlap exists across these templates because of the dominance of vertical coma in the HOA structure. All eyes evaluated received reduced HORMS with a template-based correction.
Authors: J T Barr; K Zadnik; B S Wilson; T B Edrington; D F Everett; B A Fink; J P Shovlin; B A Weissman; K Siegmund; M O Gordon Journal: Cornea Date: 2000-07 Impact factor: 2.651