S Gollamudi 1, M Cohler 2, E Hocking 2, J Linn 1, P Gunvant 2 1) Eye Specialty Group Memphis, Tennessee 2) Southern College of Optometry, Memphis, Tennessee Dr. Pinakin Gunvant received an unrestricted grant from Heine USA investigate the Heine Lambda 100 Retinometer. All other authors- no competing interests

 To evaluate the efficacy of the Heine Lambda 100 Retinometer (interferometer) in predicting the post- cataract extraction visual outcome.

 The Heine Lambda 100 retinometer is based upon Maxwellian principles. A micro-aperture is illuminated by a halogen bulb through a red filter and imaged by an optical system into the patient’s pupil. Diffraction forms a circular test pattern with equally spaced red and black lines.

 This grating pattern is projected onto the patient’s retina.  The unit of measure of the retinometer is visual angle in arc minutes and is therefore equivalent to Snellen acuity.  The grating lines can be oriented in 4 different directions over 6 different acuity levels (20/300, 20/150, 20/60, 20/40, 20/30, and 20/25). 20/15020/6020/4020/3020/25

 Patients who were scheduled to undergo cataract extraction were recruited for the study n=81 eyes of 81 individuals  Pupils were dilated and the pre-cataract evaluation included measurement of visual acuity using the retinometer.

 The orientations of the retinometer grating bars were randomized at each acuity level by means of a computer-generated randomization sequence.  Retinometer acuity was recorded as the last acuity level in which the subject was able to correctly identify at least 3 of the 4 randomized grating orientations.  Sequence of measurements for patients 1, 2 and 3 20/30020/15020/6020/4020/3020/25 1V,R,H,LV,H,R,LH,V,R,LL,H,R,VR,H,L,VH,L,R,V 2V,R,H,LV,H,L,RH,V,L,RR,L,H,VL,R,V,HV,L,H,R 3V,R,H,LH,V,R,LL,H,R,VR,H,L,VH,L,R,VV,H,R,L

 One week post cataract extraction, Snellen equivalent visual acuity with the aid of pinhole was evaluated. This was compared to the acuity obtained pre-operatively using the interferometer.  The visual acuity was recorded as a decimal acuity for the purposes of analysis. Example:  20/40 Snellen acuity = 0.5 decimal acuity  Altman and Bland Plots were performed to graphically examine the agreement between pre-operative retinometer acuity and post- operative visual outcome.

 Examining the results, we find that the upper limit and lower limit of agreement examined by the Altman and Bland plots are to of decimal acuity.

 In 25% of the cases, predicted retinometer acuity was the same as the post-operative visual outcome.  The predicted retinometer acuity was within one line of the post cataract visual outcome in 63% of the cases and within two lines for 77% of the cases.  The approximate time required for performing the retinometer evaluation was no greater than five minutes.

 Potential acuity meter (PAM) is a device that coupled with using a slit lamp biomicroscope can estimate post cataract visual outcome.  Prior reports show that PAM may underestimate post cataract visual outcome 1,2. 1)Devereux et al Potential acuity meter results in cataract patients Clinical and Experimental Ophthalmology (2000) 28, 414–418 2) Chang et al A comparison of the potential acuity meter (PAM) and the illuminated near card (INC) in patients undergoing phacoemulsification Eye (2006) 20, 1345–1351

 Tharp et al 3 have compared the retinometer with the PAM and found that both devices in a small group of eyes (n=34).  They concluded that neither the retinometer nor the PAM can predict post cataract visual outcome.  Small sample size and methodological differences may explain the differences in results when compared to present study 3) Tharp et al Prospective comparison of the Heine Retinometer with the potential acuity meter for the assessment of potential visual acuity before cataract surgery. Ophthalmic Surgery 1994; 25(9):576–579.

 The Heine Lambda 100 Retinometer appears to be a clinically easy device to use.  It predicts post cataract visual outcome within two lines of Snellen visual acuity in 77% of cases.  It could prove to be a useful tool in evaluating the retinal integrity prior to cataract extraction.