Author: haroon tayyab (Pakistan)
Co-authors: Rehman Siddiqui, sana jahangir, shiraz hashmi
Recently, optical coherence tomography (OCT) based indicators have been used and assessed for the ability to predict both functional and structural outcome after macular hole surgery. This has advanced the role of OCT from just diagnosing FTMH towards predicting outcome. This application of different FTMH parameters based on pre-operative OCT can give us further insight into the pathogenesis of FTMH and effectiveness of varying surgical techniques in yielding better surgical outcomes.Researchers have used Diameter Hole Index (DHI), Tractional Hole Index (THI), Hole Form Factor (HFF), minimum hole diameter, hole base diameter, maximum hole diameter, apex diameter, macular hole height, hole arm length and Macular Hole Index (MHI) as OCT based indicators to predict structural and functional outcome of FTMH surgery. Similarly, other OCT based findings may correlate with the functional outcome of macular hole surgery like the integrity of External Limiting Membrane (ELM) and Inner Segment/Outer Segment (IS/OS) line. We aim to study these OCT based parameters in our population in predicting the functional outcome of FTMH surgery and compare the results with international literature to explore the utility of this information in our population of FTMH.
This study was designed as retrospective chart review of 30 eyes diagnosed to have FTMH and then proceeded with surgical management. The cases reviewed in this study were from January 2016 to March 2020. All of these cases presented at The Aga Khan University Hospital, Karachi, Pakistan.
These cases were diagnosed clinically on slit lamp examination by an experienced vitreoretinal surgeon. Further macular hole staging and parameter measurement was done using Spectral Domain Optical Coherence Tomography (SD-OCT – Spectralis Heidelberg Engineering Inc. Franklin, USA). This parameter measurement was done using caliber function of OCT machine in all pre-operative OCTs scans by two independent operators and then verified by an experienced vitreoretinal surgeon. Patients who had other concurrent diseases that may impair the functional outcome of surgery were excluded from the study (glaucoma, retinal detachment, vascular retinopathy, proliferative vitreoretinopathy, high myopia > -6.00 DS). Secondary macular holes were also excluded from the study (trauma, high myopia, secondary epiretinal membrane associated macular hole). Patients with a history of symptoms of more than 6 months were not included in this study. The Ethical Review Committee (ERC) of The Aga Khan University Hospital gave approval of this study. The reference number of ERC is 2020-5158-11463. Various OCT based ratios were calculated using following formulas: • Diameter Hole Index (DHI) = MD/BD • Tractional Hole Index (THI) = H/MD • Hole Form Factor (HFF) = (RAL + LAL)/BD • Macular Hole Index (MHI) = H/BD
We analyzed the data of 28 out of 30 patients. The mean age was 61.5 ± 6.2 years. The female to male ratio was 2.11:1. Mean Minimum Diameter (MD) was 448.3 ± 189.9 m. Mean hole height was 456.2 ± 112.6 m. Hole base diameter was 888.9 ± 277.1 m. Table 1 shows pre-operative and 6 months post-operative BCVA in LogMAR with a p-value <0.001 which is statistically significant. Indices of various OCT cut points derived from ROC curve analysis that predict favorable outcomes (BCVA equal to or better than 0.4 logMAR at 6 months post-operative) was: 0.454, 1.086, 0.854, and 0.501 for Diameter hole index (DHI), Tractional hole index (THI), Hole form factor (HFF) and Macular hole index (MHI) respectively. Area under the curve and 95% estimated to be acceptable range for DHI [0.750 (0.559 to 0.889)], however was in excellent range [0.827 (0.637 to 0.943)], [0.846 (0.660 to 0.954)], [0.827 (0.637 to 0.943)] for THI, HFF, and MHI respectively. Specificity was 100% for each indices and sensitivity was high for HFF (84.6%) and lowest for DHI (64.29%)
The cut off values for MHI, DHI, HFF and THI in our study were 0.501, 0.454, 0.854 and 1.086 respectively. These cut off values showed a predicted LogMAR vision gain of 0.4 or better at 6 months post-operative time. These cut offs were associated with area under curve (AUC with 95% confidence interval), sensitivity (with 95% confidence interval) and specificity (with 95% confidence interval) of 0.827, 69, 100 for MHI; 0.75, 64, 100 for THI; 0.846, 84, 100 for HFF; 0.827, 73 , 100 for DHI. This result is in comparison with Geng et al where cut off values for MHI and HFF were 0.427 and 1.02 with comparable sensitivities and specificities. The difference was the BCVA at 6 months. We restricted the outcome to 0.4 LogMAR or better as success where Geng included all cases as success where post-operative BCVA improved by 2 lines at 6 months post-operative period. In another study, the cut offs for MHI and THI were 0.47 and 0.97 which correlated with improved functional results after surgery. These results are also comparable with our study as the author set the cut off for BCVA at 0.25 whereas in our study, it was 0.4.