readrPACI {rPACI}

Read a corneal topography file in rPACI format

Description

This function is intended to read external files with a corneal topography that have been previously exported by rPACI, using writerPACI. The file should have the format used by rPACI, i.e., a list with three columns (x and y coordinates of each point, and its ring index) and a row per data point In general, we recommend to use the more general wrapper function readFile to read any file format.

Usage

readrPACI(filepath, sep = ",")

Arguments

filepath

A file path to a corneal topography dataset exported by a Placido disk corneal topographer.

sep

The character used as column separator in the file (by default, ",").

Details

A corneal topographer is an ophthalmic clinical device that obtains measurements in the cornea (the anterior part of the eye). A Placido disk corneal topographer makes use of the Placido disk (see references and the vignette linked below), which produce a circular pattern of measurement nodes.

The readrPACI function is able to read a Placido disk corneal topography from a file that has been exported previously by rPACI using the function writerPACI. The dataset may have been obtained reading data from a file in other format (e.g. using readFile or readCSO), or by simulation using simulateData.

This file format consists of an optional header of any length (its size is automatically detected) and afterwards, three separated columns (x and y coordinates of each point, and its ring index) and a row per data point.

This function produces a data.frame in the usual format used by rPACI, i.e., a list with three columns (x and y coordinates of each point, and its ring index) and a row per data point, according to the function parameters (by default, 24*256 = 6144 rows or data points).

See more details about corneal topographers and the file structure in vignette("topographersDataFormat", package = "rPACI").

Value

A data.frame containing the corneal topography points, with columns:

x		The X Cartesian coordinates of the points
y		The Y Cartesian coordinates of the points
ring index		Number or index of the ring to which each point belongs

The resulting data.frame may also include in its Parameters attribute (attr(result,'Parameters')) the list of parameters used for the simulation (only if it was generated with simulateData and saved with writerPACI).

References

Rowsey, J. James, A. E. Reynolds, and Randy Brown. 1981. "Corneal Topography: Corneascope." Archives of Ophthalmology 99 (6): 1093-1100. doi: 10.1001/archopht.1981.03930011093022.

Pinero, D. P. 2015. "Technologies for Anatomical and Geometric Characterization of the Corneal Structure and Anterior Segment: A Review." Seminars in Ophthalmology 30 (3): 161-70. doi: 10.3109/08820538.2013.835844.

Samapunphong, Sopit, and Dimitri Azar. 1998. "Placido and Elevation-Based Corneal Topography. A Review." Ophthalmology Clinics of North America 11 (3): 311-29. doi: 10.1016/S0896-1549(05)70059-6.

Examples

# A dataset that was read from a corneal topographer file was later saved in the rPACI format.
# It can be read with:
dataset1 = readrPACI(system.file("extdata","ds1.txt", package="rPACI"))

dataset2 = readrPACI(system.file("extdata","ds2.txt", package="rPACI"))