In the context of IOL power calculation, the SRK/T formula differs from the original SRK formula (SRK I) primarily in which way?
- A SRK/T uses a linear regression formula; SRK I uses a theoretical optical formula with nonlinear axial length correction
- B SRK/T accounts for anterior chamber depth only; SRK I accounts for both ACD and lens thickness
- C SRK I uses a linear empirical regression formula; SRK/T is a theoretical formula incorporating a nonlinear ACD prediction model with corneal curvature and axial length ✓
- D SRK/T is recommended for eyes with short axial length (<22 mm); SRK I is recommended for long eyes
Correct answer: C. SRK I uses a linear empirical regression formula; SRK/T is a theoretical formula incorporating a nonlinear ACD prediction model with corneal curvature and axial length
Explanation
The original SRK I formula is a simple linear empirical regression: P = A − 2.5L − 0.9K (where L = axial length, K = average keratometry). The SRK/T is a theoretically derived formula that incorporates a nonlinear axial length correction and a more sophisticated prediction of postoperative ACD based on corneal height, making it more accurate especially for eyes with longer axial lengths. For extremely long eyes (>26 mm), Haigis or Barrett Universal II formulas are now preferred.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.