Korean J Ophthalmol.  2018 Dec;32(6):497-505. 10.3341/kjo.2018.0008.

Comparison of Intraocular Lens Power Calculation Methods Following Myopic Laser Refractive Surgery: New Options Using a Rotating Scheimpflug Camera

• Cho K
• Lim DH
• Yang CM
• Chung ES
• Chung TY

• KMID: 2427965
• DOI: http://doi.org/10.3341/kjo.2018.0008

Abstract

PURPOSE
To evaluate and compare published methods of calculating intraocular lens (IOL) power following myopic laser refractive surgery.
METHODS
We performed a retrospective review of the medical records of 69 patients (69 eyes) who had undergone myopic laser refractive surgery previously and subsequently underwent cataract surgery at Samsung Medical Center in Seoul, South Korea from January 2010 to June 2016. None of the patients had pre-refractive surgery biometric data available. The Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug total corneal refractive power (TCRP) 3 and 4 mm (SRK-T and Haigis), Scheimpflug true net power, and Scheimpflug true refractive power (TRP) 3 mm, 4 mm, and 5 mm (SRK-T and Haigis) methods were employed. IOL power required for target refraction was back-calculated using stable post-cataract surgery manifest refraction, and implanted IOL power and formula accuracy were subsequently compared among calculation methods.
RESULTS
Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug TCRP 4 mm (Haigis), Scheimpflug true net power 4 mm (Haigis), and Scheimpflug TRP 4 mm (Haigis) formulae showed high predictability, with mean arithmetic prediction errors and standard deviations of −0.25 ± 0.59, −0.05 ± 1.19, 0.00 ± 0.88, −0.26 ± 1.17, 0.00 ± 1.09, −0.71 ± 1.20, and 0.03 ± 1.25 diopters, respectively.
CONCLUSIONS
Visual outcomes within 1.0 diopter of target refraction were achieved in 85% of eyes using the calculation methods listed above. Haigis-L, Barrett True-K (no history), and Scheimpflug TCRP 4 mm (Haigis) and TRP 4 mm (Haigis) methods showed comparably low prediction errors, despite the absence of historical patient information.

Keyword

Barrett True-K; Intraocular lenses; Pentacam; Refractive surgical procedures; Scheimpflug

MeSH Terms

Cataract
Humans
Korea
Lenses, Intraocular*
Medical Records
Methods*
Refractive Surgical Procedures*
Retrospective Studies
Seoul

Figure

• 

  Fig. 1 Mean numeric prediction error (PE). A comparison of mean arithmetic PE between the Haigis-L, Shammas, Barrett True-K, and Wang-Koch-Maloney (WKM) methods with Haigis formulas using input values from the Pentacam system. The most accurate corneal power adjustment and formula combinations were the Haigis-L, Barrett True-K, and total corneal refractive power (TCRP) 4 mm (Haigis). TNP = true net power; TRP = total refractive power.

• 

  Fig. 2 Mean absolute prediction error. A comparison of mean absolute prediction error values calculated with the Haigis-L, Shammas, Barrett True-K, and Wang-Koch-Maloney (WKM) with the Haigis formulae using values obtained with the Pentacam system. The most accurate corneal power adjustment and formula combinations were the Haigis-L, Barrett True-K, and total corneal refractive power (TCRP) 4 mm (Haigis). TNP = true net power; TRP = total refractive power.

• 

  Fig. 3 Percentages of eyes within ±0.5 and ±1.0 diopters (D) of the target refraction. A comparison of the percentages of eyes within ±0.5 and ±1.0 D of the target refraction for the difference formulae (the Haigis-L, Shammas, Barrett True-K, and Wang-Koch-Maloney [WKM] with Haigis formulae) using values obtained from the Pentacam system. The most accurate corneal power adjustment and formula combinations were the Haigis-L, Barrett True-K, and total corneal refractive power (TCRP) 4 mm (Haigis) and total refractive power (TRP) 4 mm (Haigis). TNP = true net power.

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