Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision		 Previous revision
srk [2026/07/22 14:56] – [Step 7: IOL Emmetropic Power] Scott Larsonsrk [2026/07/28 12:31] (current) – Scott Larson
Line 47: Line 47:
 Using the Pythagorean theorem applied to corneal dome geometry: Using the Pythagorean theorem applied to corneal dome geometry:
  
-$$ H = r - √(r² - (Cw / 2)²) $$+$$ H = r - \sqrt{r^2 - \left( \frac{Cw}{2} \right)^2}* $$
  
 ---- ----
Line 78: Line 78:
 The IOL power for emmetropia is calculated using a modified vergence formula: The IOL power for emmetropia is calculated using a modified vergence formula:
  
-$$ IOLemme = (1000 × na × (nr × r - nc × LOPT)) / ((LOPT - ACDest) × (na × r - nc × ACDest)) $$ +$$ \text{IOL}{\text{emme}} = \frac{1000 \times na \left( na \times r - nc \times L{OPT} \right)}{\left( L{OPT} - ACD{est} \right) \times \left( na \times r - nc \times ACD{est} \right)} $$
-$$ \text{IOL}<em>{\text{emme}} = \frac{1000 \times n</em>a \left( n<em>r \times r - n</em>c \times L<em>{OPT} \right)}{\left( L</em>{OPT} - ACD<em>{est} \right) \times \left( n</em>a \times r - n<em>c \times ACD</em>{est} \right)} $$+
  
  
Line 85: Line 84:
  
   * **na** = refractive index of aqueous/vitreous (1.336)   * **na** = refractive index of aqueous/vitreous (1.336)
-  * **nc** = corneal refractive index (optimized, typically 1.333) +  * **nc** = corneal refractive index (1.333)
-  * **nr** = retinal refractive index +
- +
-----+
  
 ===== Step 8: Refraction Correction ===== ===== Step 8: Refraction Correction =====
Line 94: Line 90:
 To target a specific postoperative refraction (**REF**) rather than emmetropia: To target a specific postoperative refraction (**REF**) rather than emmetropia:
  
-$$ IOLpower = IOLemme - (REF / (1 - 0.012 × REF)) × (1000 × na) / ((LOPT - ACDest)² × ((na × r) / (na × r - nc × ACDest))⁻¹) $$+$$ \text{IOL}{\text{power}} = \text{IOL}{\text{emme}} - \frac{\text{REF}}{1 - 0.012 \times \text{REF}} \times \frac{1000 \times na}{\left( L{OPT} - ACD{est} \right)^2 \times \left( \frac{na \times r}{na \times r - nc \times ACD{est}} \right)^{-1}} $$
  
 ---- ----
Line 104: Line 100:
   * The **T2 modification** (Sheard et al., 2010) later addressed nonphysiologic behavior in the corneal height calculation step   * The **T2 modification** (Sheard et al., 2010) later addressed nonphysiologic behavior in the corneal height calculation step
  
 +=====Reference=====
 +[[https://docs.eyefixer.org/Cataract/IOL%20Calculations/Development%20of%20the%20SRK_T%20intraocular%20lens%20implant%20power%20calculation%20formula.pdf|Development of the SRK/T intraocular lens implant power calculation formula. Retzlaff et al. J Cataract Refract Surg. 1990;16:333-339]]
 +
 +{{tag>cataract}}