1. Partial Coherence Interferometry Failure Rate in a Teaching Hospital Leslie A. Wei 1,2, BA, Nickolaus P. Katsoulakis 2, MD, Theodoros Filippopoulos 3, MD, Paul B. Greenberg 1,2, MD 1 Ophthalmology Section, Veterans Affairs Medical Center, Providence, RI 2 Division of Ophthalmology, Warren Alpert Medical School of Brown University, Providence, RI 3 Cornea and Refractive Surgery Service, New York Eye and Ear Infirmary, New York, NY 4 Private Practice, Athens, Greece Sources of financial support: none Author financial and proprietary interests: The authors have no financial interests or proprietary interests to disclose.

2. Purpose To investigate the PCI biometry failure rate using the IOLMaster (Carl Zeiss Meditec, Dublin, CA) in a cohort of patients with visually significant cataract seen in a resident ophthalmology clinic at a Veterans Affairs (VA) medical center.

3. Background  IOLMaster (Carl Zeiss Meditec AG)  Infrared optical biometry system using partial coherence interferometry for axial length measurement  Accuracy within 20 mm  Ultrasound is accurate to 100 mm  Superior to applanation ultrasound biometry  Non-contact  IOLMaster (Carl Zeiss Meditec AG)  Infrared optical biometry system using partial coherence interferometry for axial length measurement  Accuracy within 20 mm  Ultrasound is accurate to 100 mm  Superior to applanation ultrasound biometry  Non-contact

4. Background  Partial coherence interferometry (PCI) has an 8- 22% failure rate due to a variety of causes such as mature cataracts, inability to fixate secondary to macular degeneration, tremor, keratopathy, nystagmus, and vitreous hemorrhage 1,2,3,4.  The new composite IOLMaster Version 5 software has demonstrated a failure rate of 7.4%, mostly due to posterior subcapsular cataracts 5.  There have been few studies on the efficacy of PCI in a teaching hospital setting.  Partial coherence interferometry (PCI) has an 8- 22% failure rate due to a variety of causes such as mature cataracts, inability to fixate secondary to macular degeneration, tremor, keratopathy, nystagmus, and vitreous hemorrhage 1,2,3,4.  The new composite IOLMaster Version 5 software has demonstrated a failure rate of 7.4%, mostly due to posterior subcapsular cataracts 5.  There have been few studies on the efficacy of PCI in a teaching hospital setting.

5. Methods  After obtaining IRB approval, the biometric measurements of 147 consecutive patients (165 eyes) who had resident-performed cataract surgery at a VA Medical Center from September 2007 to June 2008 were examined.

6. Results  Thirty-nine patients (42 eyes) were excluded due to a lack of preoperative cataract history and physical in the electronic medical record.  One hundred and eight patients  One hundred and eight patients (123 eyes) met the inclusion criteria: 106 patients were male (98.1%); mean age was 72.4 (range 50-91).  Thirty-nine patients (42 eyes) were excluded due to a lack of preoperative cataract history and physical in the electronic medical record.  One hundred and eight patients  One hundred and eight patients (123 eyes) met the inclusion criteria: 106 patients were male (98.1%); mean age was 72.4 (range 50-91).

7. 37.4%  Forty-six eyes (37.4%) were documented PCI failures that required immersion A-scan for axial length determination. version 5  The subgroup of eighty-eight eyes that had IOLMaster version 4 readings had a failure rate of 43.2% while the subgroup of thirty-five eyes with IOLMaster version 5 readings had a significantly lower failure rate of 22.9% (OR = 0.38, p < 0.05). 37.4%  Forty-six eyes (37.4%) were documented PCI failures that required immersion A-scan for axial length determination. version 5  The subgroup of eighty-eight eyes that had IOLMaster version 4 readings had a failure rate of 43.2% while the subgroup of thirty-five eyes with IOLMaster version 5 readings had a significantly lower failure rate of 22.9% (OR = 0.38, p < 0.05). Results

8.  All PCI failures were due to dense cataract; the type of cataract was not specified.  Eyes that successfully underwent PCI had significantly better mean preoperative best corrected visual acuity (BCVA) of 0.48 (20/60) than those requiring immersion A-scan, which had a mean preoperative BCVA of 1.4 (<20/400) (p = 0.01).  All PCI failures were due to dense cataract; the type of cataract was not specified.  Eyes that successfully underwent PCI had significantly better mean preoperative best corrected visual acuity (BCVA) of 0.48 (20/60) than those requiring immersion A-scan, which had a mean preoperative BCVA of 1.4 (<20/400) (p = 0.01).

9. Limitations  Retrospective nature  Variability in measurements secondary to different resident physicians performing PCI  Small sample size  Large number of exclusions due to incomplete electronic medical records  Inability to analyze the PCI failures in terms of type of cataract because of lack of documentation.  Retrospective nature  Variability in measurements secondary to different resident physicians performing PCI  Small sample size  Large number of exclusions due to incomplete electronic medical records  Inability to analyze the PCI failures in terms of type of cataract because of lack of documentation.

10. Conclusions  PCI biometry failure rate is still significant in the veteran population due to dense cataracts, though the new Version 5 software does appear to decrease this rate.  Poor preoperative vision is a predictor of PCI failure.  We look forward to continued improvements in PCI that will facilitate pre-operative biometry in cases of advanced cataract in teaching hospital settings.  PCI biometry failure rate is still significant in the veteran population due to dense cataracts, though the new Version 5 software does appear to decrease this rate.  Poor preoperative vision is a predictor of PCI failure.  We look forward to continued improvements in PCI that will facilitate pre-operative biometry in cases of advanced cataract in teaching hospital settings.

11. References  1 Narvaez J, Cherwek DH, Stulting RD, et al. Comparing immersion ultrasound with partial coherence interferometry for intraocular lens power calculation. Ophthalmic Surg Lasers Imaging 2008;39(1):30-4.  2 Haigis W, Lege B, Miller N, et al. Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to Haigis. Graef’s Arch Clin Exp Ophthalmol 2000;238:765-73.  3 Rajan MS, Keilhorn I, Bell JA. Partial coherence laser interferometry vs conventional ultrasound biometry in intraocular lens power calculations. Eye 2002;16:552-6.  4 Ueda T, Taketani F, Ota T, et al. Impact of nuclear cataract density on postoperative refractive outcome: IOL Master versus ultrasound. Ophthalmologica 2007;221:384-87.  5 Hill W, Angeles R, Otani T. Evaluation of a new IOLMaster algorithm to measure axial length. J Cataract Refract Surg 2008; 34:920-924.  1 Narvaez J, Cherwek DH, Stulting RD, et al. Comparing immersion ultrasound with partial coherence interferometry for intraocular lens power calculation. Ophthalmic Surg Lasers Imaging 2008;39(1):30-4.  2 Haigis W, Lege B, Miller N, et al. Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to Haigis. Graef’s Arch Clin Exp Ophthalmol 2000;238:765-73.  3 Rajan MS, Keilhorn I, Bell JA. Partial coherence laser interferometry vs conventional ultrasound biometry in intraocular lens power calculations. Eye 2002;16:552-6.  4 Ueda T, Taketani F, Ota T, et al. Impact of nuclear cataract density on postoperative refractive outcome: IOL Master versus ultrasound. Ophthalmologica 2007;221:384-87.  5 Hill W, Angeles R, Otani T. Evaluation of a new IOLMaster algorithm to measure axial length. J Cataract Refract Surg 2008; 34:920-924.