Visual Acuity and Refractive Error Improvement in Keratoconic Patients: A Low-Income Context Management Perspective

Figures & data

Table 1 The Average Income and Economic Spend for Healthcare and Eye Care Costs in the Two Economic Settings

Indices	High-Income Countries	Low-Income Countries
Annual GDP (USD)	USD 20 Trillion	USD 75 Billion
Average income per year	USD 51,000	< USD 6000
Percentage Expenditure on health	17%	6%
National expenditure on eye health per year	USD 150 million	USD 50 million
Cost of corneal cross linking per eye	USD 4000	USD 300
Average cost of a specialized RGP lens	USD 1000	USD 600
Cost of corneal transplant per eye	USD 13,000	USD 5000

Abbreviations: RGP, rigid gas permeable; USD, United States Dollar.

Table 2 Keratometric Profile of Patient Eyes (n=195)

		Range	Mode	Minimum	Maximum	Mean	Standard Deviation
Right eye	Flatter	26.30	52.00	41.50	67.80	50.86	5.86
	Steeper	35.10		43.70	68.80	54.68	6.53
Left eye	Flatter	35.00	54.00	34.60	69.60	50.67	6.27
	Steeper	33.50		34.00	67.50	53.68	6.48

Table 3 Scleral and Corneal RGP Lens Parameters Dispensed to Keratoconic Patients

Contact Lens Parameter	Minimum	Maximum	Mode
Corneal lens diameter	7.5 mm	10.2 mm	9.0 mm
Corneal lens base curve	4.2 mm	7.2 mm	6.4 mm
Scleral lenses diameter	14.5 mm	18.1 mm	16.5 mm
Scleral lenses SAG	3500 µm	4900 µm	4200 µm
Lens Power (Spherical Equivalent)	−8.25D	−13.75D	−7.50D

Abbreviations: D, diopters; µm, microns.

Figure 1 Histogram showing the distribution of unaided (A) and aided (B) visual acuity in keratoconic patients.

Table 4 Distribution of Patients According to the Severity of Unaided VA and Aided VA When Corrected with Corneal and Scleral RGP Contact Lenses

	Visual Acuity Categories Snellen (logMAR)
	Normal	Moderate	Blindness	Severe Blindness
	6/6-6/12 (00–0.1)	6/18-6/60 (0.3–0.5)	6/60-3/60 (1.0 −1.3)	3/60-1/60 (1.3–1.6)
Unaided visual acuity		120	4	–
Visual acuity with corneal RGP lenses	108	3	–	–
Visual acuity with scleral RGP lenses	13	–	–	–

Figure 2 Histogram showing the distribution of presenting (A) and corrected refractive errors (B).

Table 5 Patient Distribution According to Severity of Unaided and Aided Refractive Errors (RE) and Mean (Median) Pre and Post Fitting Refractive Error Findings

	Severity of RE						Mean RE Findings (Median)		p-value
	Myopia			Emmetropia	Hyperopia		Unaided	Aided
	a*	b*	c*		e*	f*	–	–
Unaided	1	9	114	0	-	0
RE
Corneal RGP wearers	23	8	–	80	–	–	−9.80D±4.468	−0.457D±0.80	0.001
Scleral RGP wearers	–	–	–	13	–	–	(−8.00D)	(0.02D)	0.001

Notes: *Myopia was classified into low (a), moderate (b) and high (c) and hyperopia into mild (e) and moderate to high (f).